Symptomatology, Treatment and Toxinology of 

Malayan pit viper (Calloselasma rhodostoma) venom

 

Tan, Nget Hong

Department of Molecular Medicine

Faculty of Medicine, University of Malaya

Kuala Lumpur, Malaysia

tanngethong@yahoo.com.sg

 FIRST AID SUMMARY

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 Main Risk

  • Serious Malayan pit viper venom poisoning is rare and death in human is highly exceptional.
  • Main risks are shock, hemorrhagic syndrome, local necrosis. Local necrosis is a cause of prolonged morbidity.
  • Bacterial infection following necrosis may spread to bones and joints leading to loss of a digit or limb, or crippling deformity due to the gangrene of the affected areas.
  • Tetanus secondary to postnecrotic infection is a cause of death.
Signs and Symptoms of Poisoning
  • Immediate local swelling. Swelling extending above the elbow or knee if bitten on the hand or foot respectively indicate moderate to severe poisoning.
  • Other local poisoning symptoms include: local pain, blistering and local necrosis.
  • Systemic poisoning symptoms include: continuing oozing from wound, bleeding gums. Cough hard to produce spit: hemoptysis indicates severe poisoning.

 First Aid Measures

  • The patient should be reassured and kept warm
  • Gently clean the site of the bite but do not attempt to cut the wound and suck out the venom. This will introduce infection.
  • Take the patient to the nearest hospital as quickly as possible
  • Immobilize the patient immediately after the bite and also during transit to the hospital. The bitten limb in particular should be kept still and below the level of the heart
  • If the snake has been killed, bring it together to hospital for identification.

 

                                                                      CONTENTS

 

Section 1

Name, Scientific name, family, common names

Section 1

Summary. Main risks and target organs, summary of clinical effects. Relevant laboratory analyses and sample collection, First-aid measures and management principles, Venom apparatus, Main toxins

Section 3

Characteristics: Description of the animal, special identification features,                  habitat, distribution, poisonous parts, the toxins

Section 4

Circumstances of poisoning. Uses, high risk circumstances, high risk                  geographical areas

Section 5

Route of Entry: parenteral, others

Section 6

Kinetics. Absorption by routes of exposure, distribution by route of exposure, biological half-life by route of exposure, elimination by route of exposure

Section 7

Toxicology. Mode of action, Range of toxicity (human data, animal data)

Section 8

Toxicological Analysis. Methods, ELISA for Malayan pit viper venom                  detection. Toxin concentration (serum, urine, wounds)

Section 9

Clinical Effects. Acute poisoning, parenteral exposure, chronic poisoning.                  Course, prognosis and cause of death, Criteria for the severity of the poisoning, expected complications. Systemic description of the clinical effects (cardiovascular, gastrointestinal, renal, dermatologic and local effects, hematological, fluid and electrolyte disturbances, allergic reactions,                  autopharmacological effect, special risk, pregnancy.

Section 10

Management. General principles, diagnosis of the biting species. Diagnosis of the severity of Malayan pit viper venom poisoning. Relevant laboratory analyses (sample collection, biomedical analysis, clot quality observation test), toxicological analysis, life supportive procedures and symptomatic treatment, decontamination, Antidotes (indication for antivenom, administration, serum sensitivity test, antivenom reactions, relapse of clotting defect, adult dosage, child dosage). Management discussion (the use of prednisone, the application of tourniquet, antivenom does not benefit local poisoning,, heparin, blood transfusion, fasciotomy, hospitalization).

Section 11

Illustrative Cases

Section 12

References

Section 13

Additional Information

Section 14

Authors and dates

 

Section 1: Name

 1.1 Scientific name: Calloselasma rhodostoma (Formerly known as Ancistrodon rhodostoma

       or Agkistrodon rhodostoma.)

 1.2  Family: VIPERIDAE, subfamily: CROTALINAE; Tribe: AGKISTRODONTINI; Genus:

      Calloselasma

 1.3  Common names: Malayan pit viper, marbled pit viper, Ular Kapak Bodoh (Malaysian), Ular

      Kapak Lekir (Malaysian)

 Section 2: Summary

 2.1 Main risks and target organs:

      Main risks are: shock, hemorrhagic syndrome, prolonged coagulation defect (which may lead to extensive bleeding in respond to trauma), local necrotic effect (which causes prolonged morbidity) and loss of a digit or limb, or crippling deformity due to the gangrene of the affected areas as a results of complications. Tetanus: secondary to postnecrotic infection. Serious Malayan pit viper venom poisoning is rare and death in human is highly exceptional.

      Target organs: haemostatic system, in particular the capillary endothelium.

 2.2 Summary of clinical effects:

     Local poisoning: Immediate local swelling. Local pain, blistering, local necrosis. Bacterial

     infection may follow necrosis.

Systemic poisoning: General hemorrhagic syndrome. Bleeding gums. Bleeding wound, hemoptysis. Discoid ecchymoses appear in the skin. Shock. Prolonged clotting defect due to defibrination. Thrombocytopenia. Hemorrhage into vital organs may be fatal.

2.3 Relevant laboratory analyses/sample collection:

  • Whole blood clotting time should be determined at admittance and 6-hourly after administration of the antivenom
  • The amount of local swelling as assessed by circumference at bite site compared with the unbitten limb
  • Monitor for features of hemorrhage such as hemoptysis
  • Hourly blood pressure and pulse rate
  • The following laboratory tests should be conducted: platelet count, hematocrit

 2.4 First-aid measure and management principles

      First-aid measure:

  • The patient should be reassured and kept warm: serious Malayan pit viper venom poisoning is rare
  • Gently clean the site of the bite but do not attempt to cut the wound and suck out the venom. This will introduce infection
  • Take the patient to the nearest hospital as quickly as possible
  • Immobilize the patient immediately after the bite and also during transit to hospital. The bitten part in particular must be kept still. The immobilized limb should be kept below the level of the heart
  • If the snake has been killed, bring it together to hospital for identification

 Management principles

  • Specific antivenom should be given for patient with systemic poisoning. The indication for antivenom is hemoptysis or non-clotting blood.
  • General: Treatment of shock. Tetanus prophylaxis and treatment with antibiotics if local necrosis developed. Mild analgesics to relief pain.
  • Local: No coverings or dressings should be applied to bite site. Blisters should be let undisturbed. Slough should be excised if local necrosis is obvious. When secondary infection has spread to the bones and joints, amputation may be necessary.

 2.5 Venom apparatus, poisonous parts or organs:

The venom apparatus consists of the fangs (usually a pair), which are situated in the front portion of the jaws, and a duct that connects the venom gland with the fang.

 2.6 Main toxins

The venom is a mixture of enzyme, polypeptides and non-enzymatic proteins. The main toxins include: thrombin-like enzymes, platelet-aggregation inducers, platelet-aggregation inhibitors and hemorrhagins. Other unidentified active principles may be present.

Section 3: Characteristics

3.1 Description of the animal (Figure 1)

Head triangular, snout pointed with facial pit, with large scale on the crown and smooth body scales. Middle of back reddish or purplish brown, sides paler with dark speckling; series of dark brown cross-bands, narrow in midline, wider on sides, edged with white or buff; belly pinkish white mottled with brown, top of head dark brown, sides light pinkish brown, the colors separated by a white stripe that passes just above the eye. Average length 23 to 32 inches, maximum about 40 inches. It will bite readily if disturbed but is remarkably sedentary and usually does not move away even after biting a human being. As such the snake was usually recovered at the location of the incident several hours later—hence the local name ‘stupid axe-headed snake’ (Ular kapak bodoh)

       The Malayan Pit Viper (Calloselasma rhodostoma)

3.1.1. Special identification features

   

Like other pit viper, the snake has a loreal pit between the eye and nostril, which distinguishes it from the other common poisonous snakes in Southeast Asia such as cobras, kraits and Russell’s viper (Figure 2). Unlike other pit vipers in this area (the genus Trimeresurus), Malayan pit viper has large scales on the crown which are symmetrically arranged (Figure 2b)

Figure 2: Heads of Pit Vipers: a,b: Malayan pit viper; c: Trimeresurus

 

3.1.2. Habitat:

A ground dwelling snake, it is usually found on forest floor. Apparently requires climate with well-marked wet and dry seasons (tropical monsoon). Common in the forests at low elevations and cultivated areas such as plantations and rice field.

3.1.3 Distribution:

 

Thailand, northern Malaysia (the northern states of Kedah, Penang and Perlis and also Kelantan), Cambodia, Laos, Vietnam, Burma and Indonesia (Java and Sumatra)  (Figure 3, shaded area)

3.2 Poisonous parts:

 

The entire venom apparatus consists of the fangs and ducts that connect the venom glands with the fangs. The glands and ducts are located on each side of the head, while the fangs are situated in the front portion of the jaws. The fangs are long, movable and very prominent (Figure 4). When the snake bites, the venom is forced down the hollow of the fang into the wound of the victim by muscles which compress the gland at the time of biting. The snake apparently can control the amount of venom it ejects.

3.3  The Toxins:

3.3.1 Name: Calloselasma rhodostoma venom

3.3.2 Description:

      Calloselasma rhodostoma venom is a mixture of enzymes and non-enzymatic proteins. On the average 50 mg dry weight of venom can be extracted from an adult snake (Reid, 1967). The venom exhibits the following biological and enzymatic activities: hemorrhage, platelet-aggregating inducing, platelet-aggregating inhibiting, edema-forming, thrombin-like, protease, fibrinogenase, hyaluronidase, arginine ester hydrolase, arginine amidase, L-amino acid oxidase, 5’-nucleotidase, phosphodiesterase, alkaline phosphomonoesterase and phospholipase A (Tan et al., 1986). The important biologically active constituents of the venom include: 

  • Thrombin-like enzymes: The venom contains several thrombin-like enzymes, all of which exhibit arginine ester hydrolase and fibrinogenolytic activities. They are responsible for the defibrination syndrome (leading to prolonged coagulation defect) caused by the venom. The major form is known as ancrod or arvin, which constitutes 7.5% by weight of the protein content of the venom. Ancrod has a molecular weight of 55000 and is a glycoprotein with 29% carbohydrate content (Esnouf and Tunnah, 1967; Hatton, 1973). The enzyme coagulates fibrinogen solution by catalyzing the release of fibrinopeptide A (but not fibrinopeptide B), AP and AY. Unlike thrombin, ancrod does not require calcium ion for its coagulant action and does not activate Factor XIII. Consequently, clots that form with the enzyme are not cross-linked and are very susceptible to rapid lysis by plasmin. Thus, when injected into human or animals, it causes continual microcoagulation of fibrinogen but the resulting fibrin is virtually simultaneously disposed off. Thus, although ancrod is basically ‘coagulant’, the paradoxical effect in human or animals is non-clotting or poorly clotting blood because of absent or very low fibrinogen level. The thrombin-like enzymes of the venom are rather heat stable and retains 50% of coagulant activity after 6 days’ incubation at 37oC. Ancrod is quite lethal to rabbits but well tolerated by rats (Ashford et al, 1968).
  • Hemorrhagins: the venom contains several hemorrhagins. It has been suggested that hemorrhagin acts by destruction of the collagenous basement membrane and other connective tissue collagens with consequent weakening of the stability of the blood vessel wall, causing hemorrhagic effects (Ohsaka, 1979). The major Malayan pit viper venom hemorrhagin, termed rhodostoxin (or kistomin) has been isolated and amino acid sequence is homologous to other venom hemorrhagins (Tan 1998).
  • Platelet aggregation inducers: The platelet aggregation inducer, aggretin (Rhodocytin) is a nonenzymatic protein with 2 subunits, containing 136 and 123 amino acid residues, respectively (Chung et al., 1999; Shin and Morita, 1998, Wong et al, 2001.). Some authors suggested that it is an endothelial integrin α2β1 agonist but recent report indicated the inducer does not recognize that α2β1.
  • Platelet aggregation inhibitors or disintegrins: Several disintegrins have been isolated from Malayan pit viper venom, including rhodostomin and rhodocetin. Rhodostomin is a 68 amino acid residue polypeptide with a hairpin loop that presents the binding sequence RGD (Arg-Gly-Asp). It inhibits platelet aggregation by blocking the binding of fibrinogen to the integrin aIIbb3 of platelet (Teng and Huang, 1991). On the other hand, rhodocetin is a bigger molecule (262 amino acid). It is RGD-independent and binds to a2b1 integrin (Bergmeier et al., 2001)
  • The antiplatelet protease, a metalloproteinase, is identical to rhodostoxin (kistomin). It dose and time-dependently prolonged the latent period of aggregation and inhibited ATP secretion of human washed platelets stimulated by thrombin (Huang et al., 1993)
  • Fibrinolytic factor: this probably plays only a secondary role in defibrination syndrome caused by the venom (Reid, 1967)
  • L-amino acid oxidase: a major constituent of the venom, constituting 30% of the crude venom dried weight (Ponnudurai et al., 1994). The enzyme is an acidic glycoprotein with a molecular weight of 132000, and is composed of two subunits of equal molecular weight. Preliminary studies indicated that the enzyme was not lethal but exhibited strong edema-inducing activity in rat.
  • Hyaluronidase: this is the spreading factor of the venom and probably promote the absorption of the venom
  • Edema-forming factors: the nature of these factors is not well investigated (Tan et al., 1992)
  • Other factors causing autopharmacological action which may lead to bradykinin release etc. (Reid, 1967)
  • Other venom enzymes such as phospholipase A, other arginine ester hydrolases, arginine amidase, proteases and fibrinogenases may play a role in the toxic action of the venom but these are not well characterized (Tan et al., 1986; Tan and Ponnudurai, 1996).

 Section 4  Circumstances of Poisoning

 4.1 Uses

The snake is used for milking of the venom which is used for immunization of horse/goat to produce antivenom. In Malaysia and Thailand, the snake is also kept in Snake Farms which are tourist attractions.

Ancrod, or Arvin, the major thrombin-like enzyme of the venom, can be used clinically to produce controlled defrination in patients requiring anticoagulant therapy (Sherman et al., 2000)

 4.2 High risk circumstances:

Malayan pit viper bite is predominantly a rural and occupational hazard. Many bites occur in the compound of house, inside the house or on a path. Adults bitten on a path or house compound are usually going to a well or latrine, clearing their compound or picking up firewood. Many school children are also bitten on their way to school. Individuals at occupational risk are rubber tappers, weeders, rice and other farmers.

 4.3 High risk geographical areas:

Malaysia: Only in Peninsular Malaysia and the snake is not found south of Penang state latitude (and it does not occur on Penang Island). All the confirmed bites occurred in the states of Perlis, Kedah and Penang., though it has been also been reported in Kelantan (Vishna et al., 1994). During the period 1970-1979, among 5745 snakebites treated in General Hospital Alor Star at Kedah, 3230 cases (56.5%) were due to Malayan pit viper. Common in lowland forests and cultivated areas such as plantations and rice fields. Usually found on the forest floor, taking shelter in between roots of trees, underneath logs and also among heaps of dried leaves. In rubber plantations, it is found on the ground or at bases of rubber trees. In rice fields, it is found commonly in the straw during the harvest when rats are abundant.

Thailand: most common in the eastern and southern parts of the country where rainfall is heaviest.

 

Section 5: Route of Entry

5.1 Parenteral

      Cutaneous, subcutaneous or intramuscular routes through biting

5.2 Others:

Experimentally, the intraperitoneal, intravenous, subcutaneous and intramuscular routes are all used.

 

Section 6: Kinetics 

6.1 Absorption by routes of exposure:

      The venom is injected into the bitten limb and the bulk of it absorbed immediately via the lymphatics. However, certain amount of the venom injected is retained in the wound and continues to enter into the circulation for some time (this is known as the ‘depot’ effect).

 

6.2 Distribution by route of exposure:

The injected venom is transported through the lymphatic vessels to the general circulation.

6.3 Biological half-life by route of exposure:

In human victim, serum venom level remains relatively constant over a period of 2-3 days (Brown and Brown, 1987). Studies using radiolabelled ancrod (the major thrombin-like enzyme of the venom) in human indicated that half the dose was eliminated from the plasma compartment during the first 3-5 hours, followed by a slower elimination over the next 4 days, and finally the last 7% to 8% of the total dose was eliminated with a half-life of 11.5 days (Regoeczi et al., 1970). Reid et al. (1963d) reported that non clotting blood persisted in untreated patients for an average of 6.7 days and may persist for over 2 weeks. All these observations suggest slow catabolism or continued uptake of the venom from the wound site. ELISA study indicated the persistence of venom in wound aspirates for as long as two weeks.

The serum kinetics of the venom and two venom components (the major hemorrhagin and the thrombin-like enzyme) in rabbit has been examined by double-sandwich ELISA (Ponnudurai and Tan, 1998). The level of C.rhodostoma venom in serum peaked 12 hr post injection and was followed by a gradual decline. The level was not detectable 192 hr post injection. The serum level of the C.rhodostoma thrombin-like enzyme increased slowly, reached the maximum 48 hr after intramuscular injection of the venom and thereafter decreased slowly. On the other hand, rhodostoxin exhibited a biphasic serum kinetics profile; with a considerably high serum level 15 min post injection, which then dropped slightly and progressively increased again after 1 hr post injection. It peaked 12 hr post injection and declined gradually thereafter.  The serum levels of both thrombin-like enzyme and rhodostoxin wee not detectable 5 days after venom injection.

6.4 Elimination by route of exposure:

Some venom components may be eliminated unchanged in the kidney while others may be catabolized (see also section 6.3)

 

Section 7: Toxicology

7.1 Mode of action

  • Thrombocytopenia: presumably due to the action of platelet aggregation inducers and antiplatelet proteases
  • Defibrination syndrome: the defibrination syndrome is due mainly to the action of ancrod and partly to the activation of fibrinolysis causing fibrinogenolysis. Ancrod acts directly on fibrinogen, releasing only fibrinopeptide A and fibrin monomers that form microclots. These fibrin monomers polymerize more slowly and form less turbid clots than do thrombin-induced fibrin monomers. The microclots formed are also more easily lysed by plasmin digestion than are thrombin clots. Also, Arvin does not activate factor XIII, so the fibrin complex is not cross-linked and hence permits rapid lysis of the fibrin formed through secondary activation of the fibrinolytic system. Thus, ancrod causes continual microcoagulation of fibrinogen but the microclots are virtually simultaneously lysed. In the presence of sufficient amount of ancrod, the rate of consumption of fibrinogen may exceed its rate of synthesis in the liver, resulting in defibrination syndrome characterized by non-clotting blood without intravascular thrombi formation.
  • Systemic bleeding: the primary defect in systemic bleeding caused by Malayan pit viper bite is hemostatic failure due to thrombocytopenia aggravated by defibrination syndrome.
  • Local swelling, hemorrhage and necrosis: these may be due to the actions of the hemorrhagins and edema-forming factors as well as autopharmacological actions of the venom.
  • Shock: this is caused partly by hypovolemia from loss of fluids into the bitten limb and probably partly due to bradykinin release caused by the autopharmacological action of the venom.

7.2 Range of toxicity

7.2.1 Human data

Lethal dose in human is not known. However, injection of 0.48 mg of dry venom in adult caused only local symptoms including edema, subcutaneous bleeding and throbbing (Vest and Kardong, 1980).

7.2.2 Animal data

Acute toxicity: LD50 (median lethal dose) is the dose that is required to kill 50% of the animals in study within a definite period of time (usually 24-48 hrs)

         LD50 in mouse: 4.6 mg/kg (intravenous injection)

                                 16.1 mg/kg (subcutaneous injection)

         LD50 in dog    :  0.9 mg/kg (intravenous injection)

                                   1.9 mg/kg (subcutaneous injection)

 

Defibrination activity: Minimum defibrinating dose (MDD) is the least quantity of venom producing non-clotting blood within 60 min (in mouse) or 150 min (in dog)

         MDD in mouse:   0.005 mg/kg (intravenous injection)

                                     1.5     mg/kg  (subcutaneous injection)

         MDD in dog    :    0.005 mg/kg (intravenous injection)

                                      0.05 mg/kg (intramuscular injection)  

 

Hemorrhagic activity:  Minimum hemorrhagic dose (MHD) is the least quantity of venom causing a hemorrhagic skin reaction of 10 mm diameter on the inner side of the skin 24 hours after intracutaneous injection of 0.1 ml into the depilated dorsal skin of rabbit. MHD of Malayan pit viper venom in rabbit was 10 mg

 

Section 8: Toxicological Analysis

8.1 Methods

There is no simple technique for analysis of the venom. Theakston and Reid (1983) proposed the following tests for inter-laboratory characterization of venoms: median lethal dose, minimum coagulant dose, minimum hemorrhage dose, minimum necrotizing dose and minimum defibrinating dose. Malayan pit viper venom is characterized by having the lowest minimum defibrinating dose (MDD = 0.9mg/mouse) compared to the other snake venoms in the areas (MDD> 4mg/mouse). The various components of venom can generally be separated by gel filtration and ion exchange chromatography (Iwanaga and Suzuki, 1979).

A simple, indirect method for assessing the venom level in victim is the non-clotting blood test (Reid, 1970). This can be done by using a capillary tube with blood taken from a finger prick. The tube should be kept horizontal at room temperature for 20 to 30 min and then raised vertically. Non-clotting blood runs out of its own accord, and this indicates enough amount of venom has been injected into the victim to cause systemic poisoning.

Venom concentration in tissue fluids, however, can be readily quantitated by enzyme-linked immunosorbent assay (ELISA) (Ho et al., 1986, Dhaliwal et al., 1983, Tan et al., 1992)

      ELISA for Malayan pit viper venom detection:     (according to Ho et al., 1986)

  1. Preparation of the IgG, conjugation and substrate:

Antiserum to crude Malayan pit viper venom was raised in rabbits and the IgG fraction was purified by a protein A-Sepharose 4B column (Goding, 1976), dialyzed against phosphate buffered saline and suspended at 2 mg/ml. Parts of the purified IgG was conjugate to alkaline phosphatase (Engvall and Perlmann, 1972) and stored at 4oC until use. The substrate solution contains 1 mg/ml of p-nitrophenyl phosphate in diethanolamine buffer, pH 9.8.

  1. Test Procedure

This was performed using the double sandwich ELISA for antigen detection (Voller et al., 1980). Polystyrene micro ELISA plates were coated overnight at 4oC with purified rabbit antivenom IgG at 1 mg/ml. The plates were post-coated with 1% bovine serum albumin at room temperature for 1 hour. Test sera were diluted in the microtiter plate wells in duplicate by adding 20 ml of sample to 180 ml of PBS/Tween plus 1% normal rabbit serum to a final dilution of 1:10. Serum samples were incubated for 4 hours at room temperature. The plate is washed three times in PBS/Tween and the conjugate at 1:1000 was then added and the plate kept at 4oC overnight. Substrate was added and the reaction allowed to proceed for 30 minutes at room temperature. Absorbance at 405 nm was determined using an ELISA reader. Venom concentrations were read from a standard curve prepared in each run. Mean absorbance value of large number of normal sera from local population should be used to establish the negative cut-off point. According to Ho et al. (1986), the method had a specificity of 95%, a lower detection limit of 10 ng/ml and coefficient of variation of 10-12%.

8.2 Toxin concentration (Ho et al., 1986)

Serum: A study by Ho et al., (1986) showed that the mean venom level in serum is 175+34 ng/ml for patients with non-clotting blood on admission (average 9.6 hours after being bitten) and 35+4 ng/ml for patients with no gross clotting abnormally on admission. However, for these patients non-clotting blood became evident in 1.5 to 72 hours. Patients in whom spontaneous systemic bleeding occurred had venom level of 219.0+53.5 ng/ml while those who did not, had venom level of 61.1+12.8 ng/ml. However, there was no significant correlation between admission venom level and the length of snake, or the age, weight or surface area of the victim. Brown and Brown (1987) reported that in an untreated severe poisoning case the blood venom level was 525 ng/ml, 22 hours after being bitten, and remained at 230-290 ng/ml range for 56 hours.

Urine: In urine specimens collected early after the bite, venom concentration comparable to serum venom concentration is readily detectable. However, venom may be absent in urine of patients who are admitted late (56-85 hours)

Wound: Venom concentration in wound aspirates varies widely (0-1 mg/ml) and may be detectable in some cases up to 2 weeks after the bite.

 

Section 9: Clinical Effects

9.1 Acute Poisoning –Parenteral exposure

Local swelling (Figure 5) begins minutes after the bite and may continue to increase from 24 to 72 hours. The swelling, which is due to the extravasation of plasma and red blood cells into tissue results in discoloration and is usually hard and tense for the first 24 to 48 hours and thereafter becoming soft and pitting. There may be slight oozing of blood from the wound site.

 

  Figure 5: Local swelling twenty minutes after the bite

 

If large amount of venom has been injected, blisters may form around the bite (Figure 6) followed by local superficial necrosis (Figure 7 and 8).

Gangrene may occur as complications. Local pain may be negligible or severe and is related to the degree of poisoning. It can last for a few days. The extent of local poisoning is an indication of the severity of systemic poisoning. Reid et al. (1963) reported that in Malaysia, 15% and 11%, respectively, of the patients developed blisters and local necrosis. On the other hand, Warrell (1986) reported that the clinical picture of Malayan pit viper bite in Thailand is dominated by local effects of the venom and massive local swelling, bruising, blistering and extensive necrosis of skin and muscle are not uncommon.

Systemic poisoning is characterized by systemic bleeding, which may be slight with only a prolonged clotting time or when severe, present as hemorrhagic syndrome with or without shock. The earliest manifestation of severe systemic poisoning is hemoptysis, which may present 20 minutes after the bite if large amount of venom has been injected. Other signs that followed (usually 2 hours after the bite) are continued oozing of blood from the wound site, gum bleeding, tooth sockets or ulcers, discoid hemorrhages (Figure 9). In severe systemic poisoning, blood clotting defect may occur 30 minutes after the bite and the blood remained incoagulable for prolonged period.

 

 

Figure 6 (Left): Blisters in Calloselasma

               rhodostoma bite

Figure 7 (above): Local necrosis in finger

               bite by Calloselasma rhodostoma

 

Figure 8: Extensive necrosis of skin, subcutaneous tissues and muscle in a victim bitten by Calloselasma rhodostoma 15 days previously
         
       Figure 9: Circular discoid ecchymoses occur in 

       systemic Calloselasma rhodostoma venom poisoning

 

9.2 Chronic Poisoning—Parenteral exposure

Chronic infections as complications of local necrosis such as osteomyelitis may lead to malignant change (Warrell et al., 1986)

9.3 Course, Prognosis, Cause of Death

Course and evolution of poisoning

Local swelling starts within a few minutes of the bite and may continue to increase for 24 to 72 hours after the bite and lasted 2-3 weeks. The local swelling usually resolve in 2-3 weeks. Pain, which is also related to the degree of poisoning, usually lasted 1-2 weeks. Blisters, if left alone, will rupture spontaneously about 2 weeks after the bite and dry up in an additional 1-2 weeks. Superficial necrosis may develop over wound sites in particular bites on fingers, toes or feet, with a mean healing time of 47 days but in severe cases may take up to 10 months to heal. In severe systemic poisoning, the following hemorrhagic syndromes may present within 20 minutes to 2 hours of the bite: hemoptysis, positive tourniquet test, discoid ecchymoses, bleeding gums, continued oozing from wound and hematemesis. These syndromes may last 1-4 days. Shock occurs in very severe poisoning. In victims with systemic poisoning, blood coagulation defect may begin within 30 minutes of the bite, and persist for an average of 2 weeks. The development of non-clotting blood, however, may be delayed by up to 72 hours after the bite if less venom has been injected. The blood coagulation defect, which is essentially a defibrination syndrome, seems to be a relatively benign state. Average death time is 65 hours (range 5-240 hours) (Reid, 1968)

Prognosis:

Many patients of Malayan pit viper bite remain asymptomatic or only slight local or systemic poisoning. Reid et al. (1963a) reported that in Malaysia, moderate or severe poisoning followed in only 28% of the Malayan pit viper bite, and that the severity of poisoning was not significantly related either to age or weight of victims. The mortality rate is only 1-2% without treatment, and is less than 0.5% with treatment. In Malaysia, only 11% of the patients developed necrosis (Reid, et al., 1963d). In Thailand, however, the clinical picture is dominated by local effects of the venom, including massive swelling, bruising, blistering and extensive necrosis of skin and muscle (Warrell, 1986).

Criteria for the severity of the poisoning

The severity of the systemic poisoning is graded as severe when a hemorrhagic state was clinically evident, moderate if blood would not clot but no hemorrhagic symptoms, and slight if blood clotting was poor in quality (see Section 10.2.2). The commonest and the earliest manifestation of hemorrhagic symptom is hemoptysis. It is therefore very important, especially on admission, to ask the patient to cough hard in order to produce spit.

A fair estimate of venom dose can also be made from the extent of local poisoning: swelling extending above the elbow or knee if bitten on the hand or food, respectively, formation of blisters or local necrosis point to moderate to severe systemic poisoning.

Expected complications:

Bacterial infection usually follows necrosis and may spread to joints. Incision of the bite or the blisters also may result in bacterial infection. Misuse of tourniquets may result in complications including gangrene, peripheral neuropathy and increased fibrinolytic activity (Warrel et al., 1986)

Causes of death:

Shock appears to be the main mechanism of death. Hemorrhage into a vital organ (e.g., cerebreal hemorrhage, massive gastrointestinal hemorrhage) may also be fatal. Secondary infections, including tetanus, are also responsible for some deaths (see also Section 11.1.4)

9.4 Systematic description of clinical effects    (see also Section 11.1.1)

9.4.1 Cardiovascular

In severe cases, loss of blood from continued external hemorrhage and internal loss of fluid into the bitten limb may lead to hypovolemic shock. Profound apathy, persistent thirst, rapid thready pulse, increased sweating and hypotension develop. Heart sounds become faint and a pulmonary systolic murmur is common. For most cases, electrocardiograms are normal but in severe poisoning may show marked T-wave changes.

9.4.2 Gastrointestinal

      Vomiting may occur in severe poisoning. Hematemesis and melena sometimes occur.

9.4.3 Renal

Usually blood-urea remains in the normal range. Proteinuria and hematuria may occur in severe poisoning but are not frequent.

9.4.4 Dermatologic and local effects:

Local swelling starts within a few minutes of the bite. Extravasation of red blood cells and plasma into subcutaneous tissues results in discoloration. In severe poisoning, blisters, which usually precede necrosis, may form around the bite. They may be serious or sanguineous. Blisters extending up the limb indicate a large dose of venom. Local necrosis usually occur only in severe poisoning and is usually superficial. Bacterial infection, however, may follows necrosis and may spread to bones and joints, and amputation may then be necessary. Gangrene may also occur as complications.

9.4.5 Hematological

The hemorrhagic syndrome include hemoptysis, discoid ecchymoses, bleeding gums, continued oozing from bite and hematemesis are due to the action of the following biologically active components present in the venom: platelet aggregation inducers, platelet aggregation inhibitors, thrombin-like enzymes and hemorrhagins. While the local bleeding around the bite site is presumably due to the action of the hemorrhgin, systemic bleeding is due to hemostatic failure caused by platelet deficiency and aggravated by the defibrination syndrome (due to the consumption of fibrinogen by the thrombin-like enzymes).

Anemia caused by loss of red blood cell into the bitten limb and hemorrhage may result in a fall in hemoglobin of over 8 gm/100 ml.

9.4.6 Fluid and electrolyte disturbances

Loss of blood from continued external hemorrhage and internal loss of circulating fluid into the subcutaneous tissues of the bitten limb (a swollen limb may accommodate up to 50% of the normal blood volume) may lead to hypovolemic shock.  

9.4.7: Allergic reactions:

May be present. Person handling venom often may become allergic to the venom and develop allergic swelling when bitten. Anaphylactic reaction may occur during antivenom treatment.

 

9.4.8 Autopharmacological effect

The venom may lead to release of bradykinin which may be involved in shock in severe poisoning.

9.4.9 Special risk:

Pregnancy: Reid et al. (1963d) reported that of 5 women bitten while pregnant, only 1 aborted although all 5 had moderate or severe systemic poisoning. No harmful fetal effects were observed.

Section 10:  Management

10.1 General Principles:

Two major questions in the diagnosis of snakebite poisoning are: the identity of the snake inflicting the bite and the severity of the poisoning:

Diagnosis of the biting species: Is it the Malayan pit viper? This can be ascertained by

a)      Identification of the snake (see Section 3.1.1), if the patient bring the snake to the hospital

b)      ELISA: this is costly, time consuming (2 days) and can be performed only in a well-equipped laboratory

c)      Clinical observations and inquiring circumstances of bite (applicable in Malaysia only):

Clinical observations: Systemic pit viper poisoning is characterized by non-clotting blood and other hemorrhagic syndrome accompanied by rapid local swelling after the bite. Clinical observations alone cannot distinguish between Malayan pit viper bite and other pit viper bites in Malaysia.

Circumstances of bite: Malayan pit viper is found only in lowland and usually on the forest flood. The other common pit vipers in Malaysia also found in lowland are arboreal, usually found clinging to branches of trees. Two other pit vipers (Trimeresurus popeorium and Trimeresurus monticola) which are also found on forest floor are usually confined to hilly areas. Thus, if clinical observations suggest that the patient was bitten by pit viper, and the bite occurred in lowland areas by a snake found on the forest floor, the snake involved is most likely Malayan pit viper.

Diagnosis of severity of Malayan pit viper venom poisoning: This can be made by observation of extent of local poisoning and hemorrhage symptoms (see Section 9.3 for details)

General treatment of Malayan pit viper venom poisoning includes the following measures:

  • Adequate reassurance
  • Immobilize the patient, particularly the bitten limb. If a tourniquet has been applied, it should be released upon admission to hospital
  • Treatment of local lesion: the site of the bite and blisters should be let strictly alone. Sloughs should be excised when local necrosis is obvious
  • Treatment of shock
  • Tetanus prophylaxis. Tetanus antitoxin should be given in victims in whom local necrosis developed
  • Specific antivenom should be given to patient with systemic poisoning
  • Blood transfusion, particularly if no antivenom available.
  • All bitten patients, even without symptom of poisoning, should be admitted to hospital for observation of at least 24 hours.

10.2 Relevant laboratory analyses:

10.2.1 Sample Collection:

Blood and urine for biochemical analysis. Bring the killed snake if available for identification.

10.2.2 Biomedical analysis:

  • Determination of the blood clotting time: this should be performed at admittance and 6-hourly during antivenom treatment
  • Determination of prothrombin time, fibrinogen, hematocrit
  • Complete blood count, platelet count
  • Typing and cross-matching of blood
  • Hourly blood pressure, pulse rate
  • In severe poisoning, urine output and blood urea.
  • Clot Quality Observation Test (Reid et al., 1963c)

This is a simple test useful for assessing defibrination and the severity of systemic poisoning” clot quality is observed in glass tubes (6.5x1 cm). After contraction of the clot is complete (1 hour at room temperature) clot quality is graded according to the volume of extruded cell deposit and size of the remaining clot as follows (Figure 10):

            Grade 1: Normal. Clot approximately 50% of original whole blood volume

            Grade 2: Slight defect. Cell deposit is above the bottom curve of the tube up to

                           30% of the original whole blood volume. Clot size is diminished in

                           proportion.

            Grade 3: Moderate defect. Cell deposit is 30-50% of the original whole blood

                           volume, clot size is about half the size of a contracted normal clot.

            Grade 4: Severe defect. Cell deposit is 50% or more of original volume. Clot is

                           only a small speck.

            Grade 5: No clot.

            These grades closely parallel fibrinogen titer: Grade 1. 3 and 5 clots represent a

            fibrinogen concentration of about 75, 50 and 25 mg/100 ml, respectively.

 

Figure 10:  Clot Quality Observation  Test. After clot contraction, grading is (1) normal, (2) slightly defective, (3) moderately defective, (4) severely defective, (5) no clot

 

10.2.3 Toxicological analysis:

Venom concentration in tissues can be measured by ELISA but because of the high cost, in practice this is not done. However, it is possible to determine whether the amount of venom in blood is high enough to cause systemic poisoning by blood clotting test or clot quality observation test (see Section 8.1 and 10.2.2 for details.)

10.3 Life supportive procedures and symptomatic treatment:

  • Reassurance: Fright is the commonest symptom following snakebite. Emotional symptoms come in rapidly and the frightened patient may appear semiconscious and complains of local pain. Thus, adequate reassurance is one of the most important measures in the general treatment. A placebo injection usually rapidly relieve the symptoms (Reid, 1970)
  • Treatment of shock: This is treated like shock resulting from hemorrhage
  • Treatment of the local lesions:

Wound site: after cleansing, no covering or dressings should be applied to the wound site to avoid incidence of secondary bacterial infection. Incision and suction are more harmful than helpful because of the risk of bacterial infection and aggravating hemorrhage

Blisters: should be left alone, they will break spontaneously in about 2 weeks and will quickly heal without infection if there is no underlying necrosis.

Necrosis: as soon as local necrosis is obvious, sloughs should be excised. The best local dressing to apply after excision of slough is normal saline. Necrosis, however, is usually confined to the subcutaneous tissues and rarely involves tendons and muscle, even though muscle may appear necrotic, and excision should be avoided. Systemic antibiotics may be helpful and skin grafting should be carried out. Necrosis usually heal with little permanent ill effect. However, in neglected cases where secondary infection has spread to the bones and joints, amputation may be necessary.

  • Treatment of pain: mild analgesics may be necessary
  • Blood transfusion can help in the treatment of shock, especially if the patient was anemic before the bite, or if effective antivenom is not available
  • Antitetanus prophylaxis and antibiotics: some patients of Malayan pit viper bite survive the venom poisoning but died from tetanus. Thus, all patients should be given tetanus toxoid and antibiotics to prevent bacterial infection
  • Prednisone and epinephrine are indicated in antivenom reactions during antivenom therapy.

10.4 Decontamination:

  • Immediate amputation of the bitten toe or finger, though fully effective in preventing envenomation, are generally impracticable
  • Incision and suction of the wound site in practice are more harmful than helpful because of the danger of introducing infection or/and aggravating hemorrhage and therefore should be avoided.

10.5 Antidotes

  • Indication for antivenom: antivenom is expensive and can cause antivenom reactions. It therefore should not be given routinely in Malayan pit viper bite. Indications for antivenom therapy are: hemorrhagic signs, especially hemoptysis or non-coagulation of blood or both
  • Administration by intravenous drip. Epinephrine should be available in a syringe before antivenom infusion is started. The intravenous drip should be slow initially, and at the first sign of an anaphylactoid reaction, should be temporarily stopped and 0.5 ml of 1:1000 epinephrine solution should be injected intramuscularly. This is always effective and the antivenom infusion can then be cautiously restarted.
  • Serum sensitivity test. While many clinicians advocated serum sensitivity tests prior to antivenom administration, Reid and Theakston (1983) felt that serum sensitivity tests are unreliable and not advisable. They recommended that all patients given antivenom treatment should be regarded as likely to have a reaction. A known allergic history contraindicates antivenom treatment unless the risk of death from envenoming is so high.
  • Antivenom reactions: antivenom reactions are often classified as ‘early’ (immediate) and ‘late’ (delayed) reactions.

Early reactions occur within 24 hours of antivenom administration and vary in severity from minor to lethal (anaphylactic shock). When early reactions occur, epinephrine (1:1000, 0.5-1 ml) should be given. An antihistamine may be given intramuscularly and steroids intravenously. Supportive therapy, including maintenance of the air way and plasma expanders may be needed.

Late reactions occur between 5 to 24 days after antivenom therapy and the patients develop fever, urticaria, arthralgia, proteinuria, lymphademopathy or neuropathy. The late reactions may require steroids treatment.

Pyrogenic reactions may be treated by cooling the patient and given antipyretic drugs.

The severity of antivenom reactions depends on the purity (whether refined or unrefined etc.) of the antivenom used and the type of animal used in the preparation of the antivenom. Thus, antivenom from certain manufacturers may cause more severe antivenom reactions than others. (see Section 11.1.5 and 11.1.6)

  • Relapse of clotting defect after antivenom treatment: this may occur up to 130 hours after the initial correction. Reported incidence of relapse ranges from 10% to 35% (Reid, et al., 1963b, Warrel et al., 1986; Institute for Medical Research, 1984). The phenomenon is associated with the reappearance of venom in blood, presumably results from the continuing absorption of venom from a depot at the bite site. While the serum venom level at relapse is relatively low (average 20 ng/ml, see also Section 8.2), the amount of venom is nevertheless sufficient to cause defibrination syndrome but unlikely to cause other hemorrhage symptoms.

10.6.1 Adult Dosage

The total dosage of antivenom required depends on its potency and the severity of poisoning. The recommend initial dosage for the following antivenom is 5 ampoules: Antivenine serum Malayan pit viper (Thai Red Cross Society, TRC), Anti-Malayan pit viper venom serum (Thai Government Pharmaceutical Organization, TGPO), Snake antivenom Malayan Pit Viper (Twyford Pharmaceutical, TP). Each ampoule of TRC or TGPO freeze-dried antivenom is to be reconstituted with 10 ml of sterile water. TP antivenom (2 ml per ampoule) is to be injected neat. A higher initial dose should be given to patients with severe poisoning (e.g., with shock, gingival or gastrointestinal bleeding, massive local swelling).

Blood clotting test should be done 6 hours after administration of the antivenom. If the blood remains incoagulable, a second dose of 5 ampoules of antivenom should be given and further dose should be given at 6-hr intervals until blood coagulability is restored. After that, the blood clotting test should be repeated 12 hourly, and more antivenom given if the incoagulable state recurred.

 

10.6.2  Child Dosage

Children respond well to smaller doses of antivenom than those required by adults. However, a higher initial dose should be given to children patient with clinical signs of severe poisoning.

10.7  Management Discussion

  • The use of prednisone: Some clinicians proposed the use of steroids in the treatment of pit viper venom poisoning. Reid et al. (1963b), however, reported that prednisone benefited neither local nor systemic poisoning. Prednisone, however, is useful in the treatment of late serum reactions.
  • The application of tourniquet: this is a rather controversial procedure. ELISA study showed that in victims of Malayan pit viper bite there is no significant change in blood venom level or in the rate of increase of venom level after release of tourniquet (Ho et al., 1985). On the other hand, Pearn et al. (1981) reported that a compressive bandage delayed venom absorption in an Australian snakebite. In view of the potential complications of the improper use of tourniquets, particularly in the rural areas in Southeast Asia, their use should be discouraged.
  • Antivenom does not benefit local poisoning: Injection of antivenom locally into the site of the bite is inadvisable as this will increase the risk of secondary bacterial infection. In toe or finger bites, the increase tissue tension from injecting antivenom might aggravate the tendency to necrosis. Warrell et al., (1986) felt that necrosis can rarely be prevented if antivenom treatment is delayed for much longer than 1 hour after the bite.
  • Antivenom is highly effective in treatment of systemic poisoning even though not given until several days after the bite: It is therefore not only safe but highly desirable to wait for clear clinical evidence of systemic poisoning before giving antivenom. The clinical improvement following specific antivenom administration is usually dramatic. Oozing from the gums and bite site stopped rapidly in about 1-2 hours after antivenom administration. However, the restoration of clotting usually takes slightly longer, and the rise in platelet count is not significantly accelerated.
  • Heparin is ineffective against blood coagulation defect caused by Malayan pit viper venom poisoning as the venom has a direct thrombin-like action on fibrinogen.
  • Blood transfusion may be required when the patient was anemic before the bite or becomes anemic as a result of venom poisoning. However, intravenous infusion of human fibrinogen is not useful in correction of the coagulation defect (Reid, et al., 1963c).
  • Fasciotomy: Fasciotomy rarely benefits and may permanently harm the patient. The decision to use fasciotomy should not be just based on clinical signs alone but must be supported by objective assessment of impaired blood flow using, for example, ultrasound (Reid and Theakston, 1983).
  • Hospitalization: While defibrination symptom alone seems to be a relatively benign state, there is a risk of extensive bleeding in response to trauma, particularly for a laborer returning to hard physical work. Thus, in view of the possibility of recurrent incoagulability after antivenom treatment, patients should be hospitalized for at least 5 days and preferably longer after the initial antivenom treatment, and blood clotting checked 12-hourly.

 

Section 11. Illustrative Cases

11.1 Case report from the literature

11.1.1 Clinical observations at Sungai Petani Hospital, Kedah, Malaysia (Reid et al., 1963)

During the year mid-April 1960 to mid-April, 1961, Reid et al studied 281 cases of Malayan pit viper bite patients who attended Sungai Petani Hospital, Kedah, Malaysia. The followings are clinical data of 250 cases.

The youngest victim was aged 3 years, the oldest 85 years, and the severity of poisoning was not significantly related either to age or to weight of victim. Moderate or severe poisoning followed in 30% of 96 patients with one fang mark, and in 60% of 148 victims with 2 fang marks. Moderate or severe poisoning occurred in 40% of 29 toe bites, 45% of 142 foot bites, 50% of 23 lower-leg bites, 60% of 30 finger bites, 66% of 6 hand bites, and 75% of 20 upper-leg bites.

Local swelling is the outstanding feature of local poisoning and started within a few minutes of the bite. The swelling may continue to increase for 24 to 72 hours after the bite but in all case, at least 75% of the final swelling was reached within 12 hours of the bite. Systemic poisoning developed in 32 of 33 patients with swelling above the knee, in 8 of 12 with swelling above the elbow. None of the 86 victims with swelling below the mid-leg or elbow developed serious systemic poisoning.

In 11 patients with severe poisoning, discoloration extended up the whole limb from the bite site, but in the other 20 severely poisoned patients the discoloration was limited to around the bite. Blisters around the bite preceded necrosis and also occurred in 11 patients without ensuing necrosis. Extensive blisters occurred only in 6 patients, of whom 5 had severe and the 6th had moderate systemic poisoning. Local necrosis occurred in 27 (11%) patients. It was much commoner in toe and finger bites (27% of cases). Necrosis is usually superficial. Bacterial infection usually follows necrosis and may spread to joints. In 24 of the 27 patients with local necrosis, the area of necrosis averaged 3.3 sq cm (range 0.25 –9.0), mean healing time being 47 days (range 13-86). In the other 3 severe cases, the necrosed area was 30, 128 and 500 sq cm, respectively, and healing took 120, 234 and 322 days, respectively. Except as a complication of necrosis, local bacterial infection never occurred. In general, local pain was related to the degree of poisoning, being most severe and persistent in patients with necrosis.

Systemic envenoming was severe in 37 (15%), moderate in 32 (13%) and slight in 28 (11%) patients. Mean admission blood pressure was not significantly different between the poisoning grades. Fever occurred in only 12 of the 250 patients a  direct result of systemic poisoning. Mean duration of fever was 2 days. Clinical evidence of a general hemorrhagic syndrome was present in all 37 patients with severe systemic poisoning as follows: 

Hemorrhgaic symptoms

Patients No.

Patients %

Hours after bite first noted

Maximum duration (days)

 

Hemoptysis

29

78

0.5

4

Positive tourniquet test

25

71

1.0

3

Discoid ecchymoses

21

58

2.75

3

Bleeding gums

17

46

2.75

3

Continued oozing from bite

11

30

2.0

2

Hematemesis

3

8

2.0

1

Macroscopic hematuria

1

3

24.0

3

Oozing from sores

1

3

2.0

3

Cerebral hemorrhage

1

3

36.0

Died

 

In 8 of 37 patients with severe poisoning, shock was indicated by profound apathy, persistent thirst, rapid thready pulse, and increased sweating. Diastolic blood pressure dropped to 50-60 mm Hg. Average fall in systolic blood pressure was 26. Heart sounds were often faint, and a pulmonary systolic murmur appeared in 5 of the 8, disappearing as the patient’s condition improved. A similar murmur was heard in 4 of the 29 without shock. In the 8 shocked patients, the swelling extended above the knee in all cases. The mean lowest hemoglobin was 6.9 gm per 100 ml for the 8 shocked patients, and 9.2 gm/100 ml for those without shock. Two patients with shock had extensive and fluctuating T-wave inversions. Three patients with severe and 4 patients with moderate systemic poisoning had right-sided dominant R waves.

         Chest radiographs were not significantly abnormal in 11 out of 11 moderate cases and in 22 out of 29 severe cases. Two of the 29 had questionable increase of lung markings, in 3 the increase was unequivocal. The remaining 2 patients had opacities suggesting pulmonary infarction (1 had shock).

The white blood cell count remained within the normal range. There was no increase in urinary urobilinogen, reticulocytes, or serum bilirubin. Serial erythrocyte sedimentation rates remained normal. Significant anemia developed in some patients with severe poisoning, presumably due to the loss of red blood cells into the bitten limb.

Incoagulable blood was observed as early as 30 minutes after the bite. In 43 patients with systemic poisoning who were not given specific antivenom, the blood remained incoagulable for an average of 8 days (range 5-11) in 8 severe cases and 6.6 days (range 1-15) in 24 moderate case. Subsequently clotting remained of poor quality for a further period averaging 6.1 and 8.3 days respectively. The fibrinogen level in 27 severe or moderate poisoning cases ranged from 10 to 160 mg/ml.

In 3 of the 37 severe cases, 24-hour-urine volume fell below 500 ml. Serial blood-ureas of most patients remained in the normal range. Proteinuria was present in 16 of the 43 severe or moderate cases but disappeared in a few days. Microscopy showed red cells in the urine of 5 patients. Serial estimations of serum potassium and sodium in 12 cases and of serum transaminases remained normal.

One patient with slight systemic poisoning died 17 days after the bite from tetanus secondary to postnecrotic infection. Another patient died 38 hours after the bite from a combination of serum anaphylaxis, cerebral hemorrhage and severe pre-existing anemia.

In the absence of necrosis, recovery is rapid. The average days to complete recovery for patients with negligible poisoning, slight local poisoning, moderate local poisoning and patients with necrosis were 3.6 (range 1-10 days), 6.8 (range 2-20), 10.5 (range 5-24) and 67.6 (range 12-323) days respectively. Resolution of the swelling usually coincided with complete recovery. Systemic poisoning usually receded before local poisoning by a few days. But in 5 cases, local poisoning had completely resolved yet the coagulation defect persisted for a further 3-14 days. In the absence of necrosis, permanent ill effects have not been observed, and even following necrosis they are rare.

11.1.2    Treatment of prolonged coagulation defect caused by Malayan pit viper venom poisoning (Reid et al., 1963c)

The study was conducted at Penang General Hospital, Malaysia during 1960 to 1961 and 29 patients with moderate or severe Malayan pit viper venom poisoning were included in this study.

Non-clotting blood was present in all 29 patients. Platelets were grossly deficient in all except one case. The one-stage prothrombin time was indefinitely prolonged in 28 patients. Plasma electrophoresis showed absence of fibrinogen.

Blood transfusion does not materially shorten the duration of the coagulation defect. Fibrinogen infusion after brief improvement appeared to aggravate the coagulation defect. When monospecific antivenom(unrefined horse antiserum from the Queen Saovabha Memorial Institute, Bangkok, Thailand) was given by intravenous drip, the clinical effect was dramatic: an apathetic, shocked patient brightened and oozing from gums, bite-marks, sores, and injection sites stopped whilst the drip is still running. Correction of the coagulation defect is remarkably rapid (average 9 hours, range 2-18 hours with intravenous administration; average 17.7 hours, range 12-36 hours, with intramascular injection), regardless of time elapsing between bite and antivenom administration. However, the antivenom did not accelerate the rise in platelets, and return of platelets to normal numbers was comparatively slow (3-6 days). In some cases relapse of clotting defect followed temporary correction, and subsequently defective coagulation persisted for 3 weeks. Administration of polyvalent antivenom from the Haffkine Institute, India (horse antiserum made with venoms from Vipera russelli, Echis carinatus, Naja naja, Bungarus caeruleus) and monospecific cobra antivenom from Queen Saovabha Memorial Institute failed to correct the coagulation defect.

11.1.3    Controlled trial of specific antivenom and prednisone in Malayan pit viper venom poisoning (Reid et al., 1963b)

The trial was undertaken at Sungai Petani Hospital, Kedah, Malaysia during 1960-1961. Patients included in the trials were those with significant poisoning (but not severely poisoned cases) by Malayan pit viper, aged between 10 to 69 years and that treatment could be started within 6 hours of the bite. A total of 100 patients were divided into three groups. In the A group, 50 ml of monospecific antivenom (Queen Saovabha Memorial Institute, Bangkok, Thailand) with 1 ml of hyaluronidase was injected into the gluteal muscle of the unbitten leg. The P and C Groups received an intramuscular injection of 50 ml of distilled water with 1 m of hyaluronidase. Subjects in P Group in addition received 5 mg tablets of prednisone whereas patients in A and C Groups received indistinguishable dummy tablets.

The trial confirmed that the specific antivenom was effective in combating systemic Malayan pit viper venom poisoning while prednisone did not benefit the patients. The difference in incidence and severity of the blood coagulation defect between the group treated by specific antivenom (8%, no severe defect observed after treatment) and those receiving prednisone (53%, 4 severe cases out of 33 cases) or control treatment (43%, 5 severe cases out of 34 cases) is statistically very significant. In contrast, however, the clinical feature of local poisoning showed no significant difference between the groups.

11.1.4: Morbid pathology of Malayan pit viper venom poisoning (Reid HA, 1967)

  • Case 1: A male Malaysian Chinese aged 52 died of shock and anemia 9 hours after a bite on the left ankle by a Malayan pit viper. At necropsy 30 minutes after death, the left lower limb was tightly swollen and subcutaneous tissues were packed with blood. Viscera were notably dry and showed no hemorrhages, petechial or otherwise. Microscopy showed some centrilobular liver degeneration, small hemorrhage in muscle and fascia adjoining the bite but no thrombi or damage to vascular endothelium. Blood was incoagulable.
  • Case 2: A male Malaysian Indian aged 41 fell heavily on his head soon after being bitten by a 65 cm Malayan pit viper. Two hours later hemoptysis was observed but the general condition seemed satisfactory until 5 ½ hours after the bite, when breathing suddenly became rapid, blood pressure was unrecordable, and the patient died in a few minutes. At necropsy 17 hours after the bite, hematomas and abrasions were seen over the scalp and the bitten limb was swollen, subcutaneous tissues being filled with gelatinous hemorrhagic exudates. Subdural and subarachnoid hemorrhages were pronounced. A 2-cm hemorrhage was present in the corpus callosum. Two ecchymotic patches were present in the pericardium. No thrombosis or intravascular clotting was seen. Blood from the heart was incoagulable.

11.1.5 Envenomation by a juvenile Malayan pit viper (Vest and Kardong, 1980)

A Caucasian male, age 35, weighing 72 kg was bitten by a juvenile Malayan pit viper while preparing for force feeding. The snake was a captive raised specimen, hatched 5 months prior to bite and had a length of 27.8 cm. The subject was bitten on the dorsal surface of the fourth digit of the left hand. There was no immediate pain, but local swelling adjacent to the fang puncture developed in the first 5 minutes accompanied by throbbing. Swelling progressed rapidly and encompassed the entire distal portion of the finger within 20 minutes. The finger was tender. A small, well-defined area of subcutaneous hemorrhage was noted distal to fang puncture just behind the nail. Throughout the subsequent 5 hours the swelling gradually progressed up the digit. By the fifth hour the dorsal surface of the hand appeared puffy and edematous. 12 hours after the bite, the swelling of the left arm had begun to subside. The remaining edema encompassed the entire left hand and had some puffiness extended to adjacent digits. The wrist was edematous and tender. Tenderness was present to the elbow. Pain was not severe. The distal portion of the bitten digit had taken on a rosy hue. By the fourth day postbite, the deep redness over the distal phalanx was almost gone and the swelling had subsided completely. Joint stiffness in the fourth digit persisted until the ninth day and forearm grip strength was near normal by the 11th day. Tenderness in the forearm did not start to subside until the 4th day postbite and the last remaining tenderness in the wrist lasted for 12 days. It was estimated that about 0.48 mg dry weight of the venom had been injected during the bite.

11.1.6. Clinical trial of the monospecific Malayan pit viper antivenom at the General Hospital Kangar, Perlis, Malaysia. (Institute for Medical Research, 1984)

Seventeen Malayan pit viper bite patients in General Hospital Kangar, Perlis, Malaysia during the period July 1982 to December 1983 were selected for clinical trial of the monospecific Malayan pit viper antivenom produced by the Institute for Medical Research Malaysia. All patients had systemic poisoning symptom. The degree of systemic poisoning manifested as hemorrhagic tendencies are as follows:

  • Bleeding gums: 9 out of 17
  • Wound bleeds: 13 out of 17
  • Discoid ecchymoses: 8 out of 17
  • Hemoptysis: 3 out of 17
  • Hematemesis and Melena: 3 out of 17
  • Hematuria: 1 out of 17

In 16 out of the 17 cases where fibrinogen were determined, all except one had low fibrinogen levels (<150 mg/dl, normal 150-450 mg/dl). Antivenom of between 2 ml and 40 ml in 200 ml of normal saline or 5% dextrose was given to the patients by slow intravenous drip over 1-2 hours, after giving a test dose. Subcutaneous adrenaline 0.25 mg was given 15 minutes before giving the antivenom. Oozing from the gums, bite marks, wound and injection site generally stopped rapidly in about 1-2 hours. More antivenom were given if there was still evidence of systemic bleeding.

      Correction of the coagulation defect after antivenom infusion are shown in the following table:

 

Case No

Antivenom (ml)

Clotting time before (min)

Clotting time after (min)

Time for C.T. to return to normal (hrs)

Platelets Before (x103)

Platelet After (x103)

 

1

30

>10

5

6

60

60

2

10

>10

5

1

30

120

3

5

>10

5

5

140

140

4

40

>10

5

18

150

40

5

5

>10

>10

Antivenom stopped

40

70

6

10

>10

5

6

40

80

7

2

>10

-

not known

180

--

8

10

>10

6

18

80

190

9

10

>10

5

16

30

60

10

5

>10

10

6

110

60

11

10

>10

6

12

60

40

12

20

>10

6

6

150

100

13

10

>10

10

12

160

60

14

30

>10

>10

Not clotted

250

60

15

10

>10

8

79

150

200

16

10

>10

4

18

180

70

17

20

>10

10

24

70

70

 

         The fibrinogen level of most of the patients returned to normal values very slowly. The rise in platelets was not accelerated by the antivenom treatment. All 17 patients had non-clotting blood prior to antivenom administration. Restoration of blood clotting was achieved in 14/17 cases. In case 7, the patient requested for early discharge. There was a death (case 4). On the fourth day this patient had evidence of bleeding into the brain, with respiratory arrest requiring ventilation. There was extensive gastrointestinal bleeding. There were 6 cases (35%) of relapse of clotting defect. Amtivenom reactions including pruritus, rigors, generalized erythematous rash, urticaria and arthralgia were noted in 7 cases (41%). The onset of these side effects was as early as 30 minutes after antivenom administration but all occurred within the first 24 hours. Only in case 5 required stoppage of the antivenom infusion. In case 14, although there was a generalized pruritus and arthralgia after the first dose of antivenom, on day 2 and day 4 the 2nd and 3rd doses of antivenom were given without further problem. Anaphylaxis was not seen. All the side effects were treated with hydrocortisone and piriton with success.

11.1.7 Comparative trials of antivenoms for bites of Malayan pit viper in Southern Thailand (Warrell et al., 1986)

Fourty-six Malayan pit viper bite patients in Trang Provincial Hospital, southern Thailand during the period March-May 1984 were admitted to the study. Twenty-three brought the dead Malayan pit viper, while in the remainder, the diagnosis was confirmed by detecting specific venom antigen in the serum using ELISA method. 21 patients developed incoagulable blood more than 22 hours after admission. Patients were randomly allocated to three groups for treatment with (a) antivenine serum Malayan pit viper (Thai Red Cross Society, TRC), (b) anti-Malayan pit viper venom serum (Thai Government Pharmaceutical Organization, TGPO) and (c) snake antivenom Malayan pit viper (Twyford Pharmaceutical, TP). The initial dose was 5 ampoules of each antivenom and the antivenom was administered either by intravenous (i.v.) injection over 10 minutes or by iv infusion (antivenom diluted in 200 ml of isotonic saline) over 30 minutes. The whole blood clotting test was repeated 6 hours after the initial dose of antivenom. If the blood remained incoagulable, a second dose of 5 ampoules of antivenom was given and further does was repeated 12 hourly, and more antivenom given if relapse occurs. Treatment failure was defined as recurrence or persistence of incoagulable blood after a total of 20 ampoules of antivenom had been given. To prevent tetanus and wound infection, all patients were given tetanus toxoid 1 ml intramuscularly and benzyl penincillin, 1 megaunit, 6-hourly by iv injection for 3 days. Patients who developed signs of early antivenom reactions wee treated immediately with 0.1% epinephrine given subcutaneously (adults 0.3-0.5 ml, children 0.01 mg/kg) and chlorpheniramine maleate given by slow injection (adults 10 mg, children 0.2 mg/kg). Pyrogenic reactions were treated by cooling the patient and given antipyretic drugs. Late serum sickness reactions were treated with a 5-day course of oral prednisolone (5 mg, 6-hourly) and chlorpheniramine (2 mg, 8-hourly). Patients were transfused with fresh whole blood if after restoration of blood coagulability, the hematocrit fell below 25%.

There were no deaths in the study. Extensive necrosis developed in one of the patients, a 5-year-old girl, who was in shock on admission and was bleeding from the gums. The entire bitten limb was swollen. Platelet count was 95000/ml; all features suggesting very severe poisoning. The patient was given the first dose of antivenom 3 hours after being bitten but seems certain to suffer residual deformity and loss of function. In the other patient (44-year-old man) there was necrosis of the muscles of the anterior tibial compartment and there was clinical signs suggesting intracompartmental ischemia. The patient refused surgery and was left with severe weakness of the peroneal muscle. One patient had to have a necrotic toe amputated.

Bleeding from gingival sulci stopped within 1 hour of starting antivenom in all cases and did not recur. TP antivenom restored coagulability within 6 hours of the first dose in all 16 cases. Restoration of coagulability by the first dose of antivenom was achieved in 13/15 cases treated with  TGPO antivenom, and 11/15 cases treated with TRC antivenom. In the TRC group, 1 patient required 4 doses of antivenom, and 2 were judged treatment failures. Both were severely envenomed and were successfully treated by a single dose of TP antivenom. In 8 patients there was late recurrence of blood incoagulability 20-130 hours after it had initially been restored by antivenom. Compare to patients who responded to a single dose of antivenom, patient who needed additional doses of antivenom generally had a higher incidence of gingival bleeding, more local swelling, higher leukocyte counts and lower hematocrit, and they had been bitten by longer snake. All patients whose blood became incoagulable late (>22 hours after the bite) were cured by a single dose of antivenom.

         The responses to the three monospecific antivenoms were as follows:

 

Antivenom

TRC

TGPO

TWFORD

 

Number of cases

 

15

 

15

 

16

Platelet count/ml (median)           

 

 

 

       Before Treatment

95000

26000

69500

       After   Treatment

 

81000

26000

64000

Average time to initial restoration of blood 

      clotting, in hours (range)

 

4

(1-10)

4

(1-16)

5.5

(1-6)

Average time to permanent elimination of

       serum venom antigen, in hours (range)

 

0.8

(0.08-133)

0.85

(0.04-169)

4.75

(0.04-74.5)

Antivenom Reactions

 

 

 

    Early (Severe)

13(2)

6(1)

8(0)

    Pyrogenic

8

1

0

    Late

2

1

1

The clinical evidence for the ability of the antivenom to combat local poisoning was inconclusive.

 

11.1.8  Miscellaneous cases:

Case 1: (Brown and Brown, 1987)

A Thai farmer was admitted to the hospital 22 hours after being bitten by a Malayan pit viper. Non-clotting blood was oozing from two puncture sites in the right foot. The patient had ecchymoses and swelling of the lower leg and hemoptysis. For 56 hours the patients received monospecific Russell’s viper antivenom  owing to the initial misidentification of the snake. By 60 hours after admission, the patient’s foot had developed hemorrhagic bullae on a necrotic base and swelling extended to the groin. Chest X-ray revealed new infiltrates consistent with intra-alveolar hemorrhage and venous blood still did not clot. At 66 hours after admission patient received 5 ampoules of monospecific Malayan pit viper antivenom (Thai Red Cross Society). 6 hours later, blood clotting was observed at 18 minutes with only slight defect in clot quality. Five more ampoules of antivenom was given and the patient recovered without further complication.

Case 2 (Sawai et al., 1973)

A 59-year old Chinese was bitten on left calf by a Malayan pit viper at 10 a.m., 1st  February, 1969 while cutting grass in the rubber estate. The patient went to the district hospital, bringing the killed snake. As the patient’s general condition deteriorated with prolonged blood coagulation defect, he was transmitted to the General Hospital Penang. The patient complained of severe pain, swelling and hemorrhage. The blood pressure was 78/50, the pulse was frequent and the patient drowsy. Antivenom (80ml) was administered intravenously with hydrocortisone and 5% dextrose saline. Patient died at 3 a.m. on the next day.

Case 3 (Sawai et al., 1973)

A 47-year old male was bitten by a Malayan pit viper on right little toe at 8 a.m., 19th January, 1971, while working in a rubber estate at Songkla, Thailand. He came to hospital on 24th January, complaining of pain, swelling, hemoptysis and ecchymoses. He was treated with antivenom, but marked ecchymoses in whole right leg and a gangrene of the little toe developed.

Case 4: (Sawai et al., 1973)

A 18-year old male was bitten by a Malayan pit viper on left foot at 8 a.m., 2nd January, 1971, while cutting grass in Surathani, Thailand. He came to the hospital, complaining of pain, swelling, hemoptysis and ecchymoses. Later severe necrosis of muscle tissue developed on sole of left foot.

 

Section 12:  References

12.1 List of clinical and toxicological references

Ashford A, Ross JW and Southgate, P (1968)  Pharmacology and toxicology of a

        defibrinating substance from Malayan pit viper venom. Lancet, 1: 486-489.

Bergmeier W, Bouvard D, Eble JA, Mokhtari-Nejad R, Schulte V, Zirngibl H,

        Brakebusch C, Fassler R and Nieswandt B (2001): Rhodocytin (aggretin) activates

        platelets lacking alpha(2)beta(1) integrin, glycoprotein VI, and the ligand-binding

        domain of glycoprotein Ib-alpha.  J Biol Chem. 276, 25121-6.

Brown AE and Brown L (1987) Blood venom antigen levels after Malayan pit viper

        bite. Trans. Roy. Soc. Trop. Med. Hyg., 81, 548.

Chan KE and Reid, HA (1964) Fibrinolysis and the defibrination syndrome of Malayan

        pit viper bite. Lancet 1, 461-463.

Chan KE, Rizza CR and Henderson MP (1965) A study of the coagulant properties of

        Malayan pit viper venom. Br. J. Haemat., 11, 646-653.

Chan KE (1969) The comparison of the antithrombotic action of the thrombin-like

         fraction of Malayan pit viper venom and heparin. Cardiovas. Res. 3, 171-178.

Chan, KE (1979) Bleeding after Malayan pit viper bites. Southeast Asian J. Trop. Med. Pub. Hlth., 10, 276-279.

Chung CH, Au LC and Huang TF (1999) Molecular cloning and sequence analysis of aggretin, a collagen-like platelet aggregation inducer. Biochem Biophys. Res. Commun., 263, 723-727.

Chung MCM, Ponnudurai G, Kataoka M, Shimizu S and  Tan NH (1996)  Structural studies of a major hemorrhagin (rhodostoxin) from the venom of  Calloselasma rhodostoma  (Malayan pit viper). Arch. Biochem. Biophys. 325,  199-208.

Daltry JC, Ponnudurai G, Chai KS, Tan NH, Thorpe RS and Wolfgang W (1996) Electrophoretic profiles and biological activities: Intraspecific variation in the venom of the Malayan pit viper (Calloselasma rhodostoma)  Toxicon 34, 67-79.

Devarak. T (1979) Bleeding manifestations in snake bite. Southeast Asian J. Trop. Med. Pub. Hlth, 10, 255-257.

Esnouf MP and Tunnah GW (1967) The isolation and properties of the thrombin-like activity from Ancistrodon rhodostoma venom. Br. J. Haemat., 13, 581-590.

Gnanjothy P, Chung MCM.and Tan NH (1993) Isolation and characterization of a hemorrhagin from the venom of  Calloselasma rhodostoma (Malayan  pit viper). Toxicon,  31, 997-1005.

Hatton MWC (1973) Studies on the coagulant enzyme from Agkistrodon rhodostoma venom. Biochem J., 131, 799-807.

Ho M, Warrell DA, Looareesuwan S, Phillips RE, Chanthavanich P, Karbwang J, Supanaranond W, Viravan C, Hutton RA and Vejcho S (1986) Clinical significance of venom antigen levels in patients envenomed by the Malayan pit viper (Calloselasma rhodostoma). Am. J. Trop. Med. Hyg. 35, 579-587.

Huang TF, Wu YJ and Ouyang C (1987) Characterization of a potent platelet aggregation inhibitor from Agkistrodon rhodostoma venom. Biochim. Biophys. Acta 925, 248-257.

Huang,T.F., Chang, M.C. and Teng, C.M. (1993). Antiplatelet protease, Kistomin, selectively cleaves human platelet glycoprotein Ib. Biochim. Biophys. Acta, 1158: 293.

Institute for Medical Research (1984) Report on Malayan pit viper (Agkistrodon rhodostoma) antivenom. Institute For Medical Research, Kuala Lumpur, Malaysia. pp28-35.

Lim TW (1982) Epidemiology of snake-bites in Malaysia. The Snake, 119-124.

Ouyang C, Hwang LJ and Huang TF (1986) a-Fibrinogenase from Agkistrodon rhodostoma (Malayan pit viper) snake venom. Toxicon, 21, 25-33.

Ouyang C, Yeh HI and Huang TF (1986) Purification and characterization of a platelet aggregation inducer from Calloselasma rhodostoma (Malayan pit viper) snake venom. Toxicon, 24, 633-643.

Ponnudurai G and Tan NH (1998) Serum kinetics of Calloselasma rhodostoma  (Malayan  pit viper) venom and venom components in a rabbit injected with a non-lethal dose of C.rhodostoma venom. Paper presented at the Symposium on  Animal, Plant and Microbial Toxins (Natural Toxins of Malaysia), 28th, February, 1998, Kuala Lumpur, Malaysia.

Ponnudurai G, Chung MCM and Tan NH (1994) Purification and properties of the L-amino acid oxidase from Malayan  pit viper (Calloselasma  rhodostoma) venom. Arch. Biochem. Biophys. 313, 373-378.

Regoeczi E and Bell WR (1970) In vivo behavior of coagulant enzyme from Agkistrodon rhodostoma venom: studies using 131I-Arvin. Br. J. Haemat., 16, 573-587.

Reid HA (1967) Defibrination by Agkistrodon rhodostoma venom. In: Animal Toxins (Russell FE and Saunders PR Eds). Pergamon Press, Oxford and New York, pp 323-335.

Reid HA (1968) Symptomology, pathology and treatment of land snake bites in India and Southeast Asia. In: Venomous Animals and Their Venoms. Vol. 1 (Buckely EE, Bucheri W and Deulofeu V Eds). Academic Press, New York, pp 611-642.

Reid HA (1970) The principles of snakebite treatment. Clinical Toxicol., 3, 473-482.

Reid HA and Theakston RDG (1983) The management of snake bite. Bull. W.H.O., 61, 885-895.

Reid HA, Thean PC and Martin WJ (1963a) Epidemiology of snake bite in north Malaya. Br. Med. J. 7, 992-997.

Reid HA, Thean PC and Martin WJ (1963b) Specific antivene and prednisone in viper bite poisoning: controlled trial. Br. Med. J., 4, 1378-1380.

Reid HA, Chan KE and Thean PC (1963c) Prolonged coagulation defect (defibrination syndrome) in Malayan viper bite. Lancet, 1, 621-626.

Reid HA, Thean PC, Chan KE and Baharom AR (1963d) Clinical effects of bites by Malayan viper (Ancistrodon rhodostoma). Lancet, 1: 617-621.

Sawai Y, Koba K, Okonogi T, Mishima S, Kawamura Y, Chinzei H, Ibrahim AB, Devaraj T, Phong-Aksara S, Puranananda C, Salafranca ES, Sumpaico JS, Tseng CS, Taylor JF, Wu CS and Kuo TP (1972). An epidemiological study of snakebites in the Southeast Asia. Jpn. J. Exp. Med., 42, 283-307.

Sherman DG, Atkinson RP, Chippendale T, Levin KA, Ng K, Futrell N, Hsu CY, Levy DE. (2000)   Intravenous ancrod for treatment of acute ischemic stroke: the STAT                        study: a randomized controlled trial. Stroke Treatment with Ancrod Trial. JAMA. 283: 2395-403.

Shin Y and Morita T (1998): Rhodocytin, a functional novel platelet agonist belonging to the heterodimeric C-type lectin family, induces platelet aggregation independently of glycoprotein Ib. Biochem. Biophys. Res. Commun. 245, 741-745.

Singh N and Menon V (1973) Assessing the role of anti-viper serum in the management of viper bites. Med. J. Malaysia, 28, 47-49.

Tan NH (1998)  Kistomin (Calloselasma rhodostoma). In: Handbook of Proteolytic Enzymes (Barratt, A., Rawlings, N.D. and Woessner, J.F. Eds.)  pp.1287-1290. Academic Press, London.

         Tan NH and Ponnudurai G (1996) The toxinology of Calloselasma rhodostoma  (Malayan pit viper) venom. Toxin Reviews 15, 1-17.

Tan NH, Kanthimathi MS and Tan CS (1986) Enzymatic activities of Calloselasma rhodostoma (Malayan pit viper) venom. Toxicon, 24, 626-630.

Tan NH, Thambyrajah V and Ariaratnam P (1992) The  edema inducing activity of Malayan pit viper (Calloselasma  rhodostoma) venom.  In: Recent Advances In Toxinology  Research (Gopalakrishnakone, P. and Tan, C.K. eds.), Vol.1,   pp. 636-646. National University of Singapore Press.

Tan NH, Yeo KH and Nik Jaafar MI (1992): The use of  enzyme-linked immunosorbent assay for the quantitation of  Calloselasma rhodostoma  (Malayan pit viper) venom and venom  antibodies. Toxicon. 30, 1609-1620.

Teng, CM, Huang TF (1991): Snake venom constituents that affect platelet functin. Platelet, 2, 77-87.

Theakston RDG and Reid HA (1983) The development of simple standard assay procedures for the characterization of snake venoms. Bull. W.H.O. 61. 949-956.

Vest DK and Kardong KV (1980) Envenomation by a juvenile Malayan pit viper (Agkistrodon rhodostoma). Clin. Toxicol., 16, 299-303.

Vishna DVN, Tan NH and Choo KE (1994) The use of  enzyme-linked immunosorbent assay for immonodiagnosis of  snake bite in northeast coast of Malaysia.  (Abstr.) Toxicon 32. p.550.

Wang R, Kong C, Kolatkar P and Chung MCM (2001): A novel dimmer of a C-type lectin-like heterodimer from the venom of Calloselasma rhodostoma (Malayan pit viper).  FEBS Letts 508, 447-453.

Warrell DA (1986) Tropical snake bite: Clinical studies in Southeast Asia. In: Natural Toxins (Harris JB Ed.) Clarendon Press, Oxford, pp. 25-45.

Warrell DA, Looareesuwan R, Theakston RDG, Phillips RE, Chanthavanich P, Viravan C, Supanaranond W, Karbwang J, Ho M, Hutton RA and Vejcho S (1986) Randomized comparative trial of three monospecific antivenoms for bites by the Malayan pit viper (Calloselasma rhodostoma) in southern Thailand: Clinical and laboratory correlations. Am. J. Trop. Med. Hyg., 35, 1235-1247.

W.H.O. (1981) Progress in the Characterization of Venoms and Standardization of Antivenoms. WHO Offset Publicationos, No.58, Geneva.

 

 

12.2 List of zoological references:

 

Hoge AR and Hoge R (1973) Poisonous snakes of the world. Part 1: Checklist of the pit

          vipers. Mem. Int. Butantan,, 42/43, 179-310.

Lim BL (1982) Poisonous Snakes of Peninsular Malaysia. 2nd Edition. Malayan Nature   

         Society, Kuala Lumpur, 73 pp.

Lim BL and Ibrahim, AB (1970)  Bites and stings by venomous animals with special references to snake bites in West Malaysia. Med. J. Malaysia, 25, 128-141.

Lim BL, La, EE and De Witt, GF (1977) Comparative studies on the crude dry weight of venom extract from the Malayan pit viper Agkistrodon rhodostoma of 3 different weight groups. The Snake, 9, 11-13.

Tweedie NWF (1983) The Snakes of Malaya. 3rd Edtion. Singapore National Printers, Singapore. 167pp.

 

 

12.3 List of other technical references:

 

Dhaliwal, JS, Lim TW and Sukumaran KD (1983)  A double antibody sandwich micro-ELISA kit for the rapid diagnosis of snake bite. Southeast Asian J Trop. Med. Publ. Hlth. 14, 367-373.

Engvall, E and Perlmann, P (1972)  ELISA III. Quantitation of specific antibodies by enzyme-linked anti-immunoglobulin in antigen coated tubes. J. Immunol., 19, 129-135.

Goding JW (1976) Conjugation of antibodies with flurochromes: modifications to standard methods. J. Immun. Meth., 13, 215-226.

Latallo ZS (1978) Report of the task force on clinical use of snake venom enzymes. Thromb. Haemostasis, 39, 768-774.

Ohsaka A (1979) Hemorrhagic, necrotizing and edema-forming effects of snake venoms. In: Handbook of Experimental Pharmacology (Lee, C.Y. Ed.), Vol 52, Springer-Verlag, Berlin. pp. 481-546.

Iwanaga S and Suzuki I (1979) Enzymes in snake venom. In: Handbook of Experimental Pharmacology (Lee, C.Y. Ed.), Vol 52, Springer-Verlag, Berlin. pp.61-158.

Pearn J, Morrison N, Charles N and Muir V (1981) First aid for snake bite. Efficacy of a constrictive bandage with limb immobilization in the management of human envenomation. Med. J. Australia, 2, 293-295.

Voller A, Bidwell D and Bartlett A (1980) Enzyme-linked immunosorbent assay. pp359-371. In: Manual of Clinical Immunology (Rose NR and Friedman F Eds) American Society of Microbiology, Washington.

 

 

Section 14: Additional Information

 

Availability of antidotes:

  1. Antivene serum Malayan pit viper (Ancistrodon).: Unrefined equine freeze-dried monospecific antivenom. Queen Saovabha Memorial Institute. Thai Red Cross Society. Rama IV Road, Bangkok, Thailand.

  1. Anti-Malayan pit viper venom serum: Refined equine freeze-dried monospecific antivenom. Thai Government Pharmaceutical Organization, Bangkok, Thailand.

  1. Snake antivenom Malayan Pit Viper: Refined caprine liquid monospecific antivenom. Twyford Pharmaceutical GmbH Ludwigshafen, Germany.

  1. Polyvalent antivenom against the venoms of Malayan pit viper, Bungarus fasciatus, Naja naja. Pasteur Institute, Postbox 47, Bandung, Indonesia.

  1. Antivenom Agkistrodon rhodostoma (equinum): Institute For Medical Research, Kuala Lumpur, Malaysia.

Section 15: Authors and dates

Professor Tan, Nget Hong

Department of Molecular Medicine

Faculty of Medicine

University of Malaya, Kuala Lumpur, Malaysia

 

First Edition: Jan 31st, 1989

Second Edition: June 15th, 2004

 

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