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SNAKES, COLUBRID, OLD WORLD

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Classification   |    Detailed evidence-based information

Substances Included Synonyms

Therapeutic Toxic Class

    A) Old world colubrids are rear fanged snakes native to Africa and Asia. In general, these snakes are not aggressive; nearly all bites reported have occurred during handling of the snakes. Because colubrids have fangs located towards the back of the mouth, bites occur most often on small body parts, usually the fingers. The snake is often difficult to remove after biting.

Specific Substances

    A) Old World Colubridae capable of Fatal Envenomation
    1) Dispholidus typus (Boomslang)
    2) Rhabdophis subminiatus (red-necked keelback)
    3) Rhabdophis tigrinus (Yamakagashi or Japanese garter snake)
    4) Thelotornis capensis (bird, twig or vine snake)
    5) Thelotornis kirtlandii
    Old World Colubridae capable of Severe Envenomation
    1) Malpolon monspessulanus (Montpellier snake)
    2) Madagascarophis meridonalis (Madagascar snake)
    Old World Colubridae capable of Mild to Moderate Envenomation
    1) Ahaetulla nasuta (common green or long nosed whip snake)
    2) Amplorhinus multimaculatus (Many spotted snake)
    3) Balanophis ceylonensis (Sri Lanka keelback or blossom krait)
    4) Boiga blandingii (Blanding's tree snake)
    5) Boiga ceylonensis (Sri Lanka cat snake)
    6) Boiga dendrophila (mangrove snake)
    7) Boiga forsteni (Forsten's cat snake)
    8) Cerebus rhynchops (dog-faced water snake)
    9) Coluber ravergieri (mountain racer)
    10) Coluber rhodorachis (Jan's desert racer)
    11) Crotapheopeltis hotamboeia (herald, red or white lipped snake)
    12) Enhydris enhydris (rainbow water snake)
    13) Malpolon moilensis (hooded malpolon)
    14) Psammophis biseriatus
    15) Psammophis phillipsii (olive grass snake)
    16) Psammophis sibilans
    17) Psammophylax rhombeatus (spotted or rhombic skaapsteker)
    18) Psammophylax tritaeniatus (striped skaapsteker)
    19) Telescopus semiannulatus (Eastern tiger snake)

Overview

Life Support

    A) This overview assumes that basic life support measures have been instituted.

Clinical Effects

    0.2.1) SUMMARY OF EXPOSURE
    A) BACKGROUND: Colubrids, members of the largest family of snakes, are found on every continent except Antarctica. Some members of the family are venomous. The most commonly known venomous members includes the Brown tree in Guam, the boomslang and twig snake native to sub-Saharan Africa and Rhabdolphis species in southeast Asia.
    B) TOXICOLOGY: Colubrid venoms cause coagulopathy. The mechanism is not clear, but the venom of the boomslang contains metalloproteinases.
    C) EPIDEMIOLOGY: Envenomations in humans are rare because colubrids are rear-fanged, possess weak venom glands, and are not aggressive. Rare fatalities are reported in Africa and Asia. Envenomations are exceedingly rare in the US and are limited to exotic snake handlers.
    D) WITH POISONING/EXPOSURE
    1) MILD ENVENOMATIONS: Bites by most old world colubrids have only been reported to cause minor envenomation syndromes, including mild local swelling, inflammation or discoloration, transient local pain or bleeding, stiffness or numbness at the bite site. Systemic symptoms such as nausea, headache, and rigors have occasionally been described.
    2) MODERATE ENVENOMATIONS: Bites by the Malpolon monspessulanus (Montpellier snake) can cause moderate envenomation. Severe local swelling may develop, with paresthesia at the bite site, lymphangitis, and vague constitutional symptoms (nervousness, paresthesias of the limb). A few case reports have described ptosis and weakness of the muscles of respiration and deglutition, which resolved within 48 hours. There is limited information about Madagascarophis meridionalis envenomation, but it can produce extensive local swelling.
    3) SEVERE ENVENOMATION: Bites by Dispholdius typus (boomslang), Thelotornis capensis or kirtlandi (bird, twig or vine snakes), Rhabdophis subminiatus (red-necked keelback) or R. tigrinus (Yamakagashi or Japanese garter snake) can cause severe, potentially lethal envenomation. There is usually little initial pain and minimal swelling. Severe coagulopathy and disseminated intravascular coagulation may develop within a few hours of the bite, or may be delayed. Headache, nausea, vomiting and abdominal pain may develop early. Clinical bleeding manifestations may be severe and may not develop for 12 hours or more. They may include bleeding from the bite site (usually an early manifestation), hematuria, bleeding from venipuncture sites, hematemesis, melena or hematochezia, superficial ecchymosis, bleeding from gums, nose or ears, and subarachnoid or intracranial hemorrhage. Hemolysis and renal failure may develop. Laboratory manifestations include prolonged INR and PTT, elevated fibrin degradation products, decreased fibrinogen, thrombocytopenia and anemia.

Laboratory Monitoring

    A) MALPOLON MONSPESSULANUS (Montpellier snake): Monitor for local swelling, lymphangitis and tissue damage. Monitor for weakness or other evidence of neurotoxicity.
    B) DISPHODIDUS TYPUS (Boomslang), THELOTORNIS CAPENIS or T. KIRTLANDI (bird, twig or vine snake), RHABDOPHIS SUBMINIATUS (red-necked keelback) or R. TIGRINUS (Yamakagashi or Japanese garter snake): Monitor CBC with platelets, INR, PTT, fibrinogen and fibrin degradation products every few hours until stable. Monitor vital signs and evaluate for clinical evidence of bleeding. Monitor urinalysis and urine output. Monitor renal function, serum electrolytes, and liver enzymes in patients with coagulation abnormalities.
    C) Other old world colubrids: monitor for local swelling and tissue damage and systemic effects such as nausea or headache.

Treatment Overview

    0.4.7) BITES/STINGS
    A) MANAGEMENT OF MILD TO MODERATE ENVENOMATION
    1) Most patients will have local symptoms. Patients who develop coagulopathy after Boomslang or Rhabdolphis species envenomation should receive the appropriate antivenom. The local poison center should be contacted to obtain the appropriate antivenom. Twig snake envenomations should be closely observed, there is no antivenom. These patients can appear asymptomatic initially, and develop a delayed severe coagulopathy. The Brown Tree Snake is not known to cause severe symptoms in humans, treat with local wound care and symptomatic and supportive care. Tetanus prophylaxis should be given as indicated.
    B) MANAGEMENT OF SEVERE ENVENOMATION
    1) Severe toxicity is manifested as disseminated intravascular coagulopathy (DIC) causing severe bleeding and end-organ ischemia. These patients should receive antivenom, if available, for their species. The administration of clotting factors (FFP) and platelets is not supported by evidence, but should be considered in patients with severe bleeding. Treat with a polyvalent Colubrid antivenom should be considered if a species specific antivenom is not available. Contact a poison control center for antivenom guidelines and availability.
    C) AIRWAY MANAGEMENT
    1) PREHOSPITAL: Compression wrapping of the affected extremity, beginning proximally, is recommended during transport.
    D) ANTIVENOM
    1) Several monovalent antivenoms are available. A specific antivenom is available for Dispholidus typus (boomslang) envenomation. Anti-Yamakagashi (manufacturer: Japan Snake Institute) is available for envenomation by Rhabdophis species (Yamakagashi or Japanese garter snake, red necked keelback). Their use should be considered in patients who develop coagulopathy after bites by these snakes. These antivenoms are manufactured in Africa and Japan, respectively, to obtain them in the US contact your nearest poison center (800-222-1222)
    E) PATIENT DISPOSITION
    1) HOME CRITERIA: Any patient with a colubrid bite should be sent to the hospital. Most species are nonvenomous, but the species may be unclear at presentation.
    2) OBSERVATION CRITERIA: Patients should be observed for the development of local or systemic evidence of envenomation for 8 to 12 hours. Patients with a clear nonvenomous species envenomation can be discharged after appropriate wound care.
    3) ADMISSION CRITERIA: A patient with a Boomslang, Twig Snake, and Rhabdolphis envenomation should be admitted and any patient with more than minimal local effects should be admitted.
    4) CONSULT CRITERIA: A medical toxicologist, toxinologist or poison center should be consulted for all symptomatic patients, if antivenom use is considered or if the species is unclear.
    F) PITFALLS
    1) Coagulopathy can be delayed for several hours.
    G) DIFFERENTIAL DIAGNOSIS
    1) Elapid or crotalid envenomations.

Range Of Toxicity

    A) SEVERE ENVENOMATION: A single bite from a Dispholidus typus (boomslang), Thelotornis capensis or T. kirtlandi (bird, twig or vine snake), Rhabdophis subminiatus (red necked keelback) or R. tigrinus (Yamakagashi or Japanese garter snake) snake can cause severe bleeding and coagulopathy or, rarely, death.
    B) MODERATE ENVENOMATION: Malpolon monspessulanus (Montpellier snake) bite can cause moderate local and systemic effects, but fatalities have not been reported.
    C) MILD ENVENOMATION: Bites by other old world colubrids may cause mild local or systemic effects.

Clinical Effects

Summary Of Exposure

    A) BACKGROUND: Colubrids, members of the largest family of snakes, are found on every continent except Antarctica. Some members of the family are venomous. The most commonly known venomous members includes the Brown tree in Guam, the boomslang and twig snake native to sub-Saharan Africa and Rhabdolphis species in southeast Asia.
    B) TOXICOLOGY: Colubrid venoms cause coagulopathy. The mechanism is not clear, but the venom of the boomslang contains metalloproteinases.
    C) EPIDEMIOLOGY: Envenomations in humans are rare because colubrids are rear-fanged, possess weak venom glands, and are not aggressive. Rare fatalities are reported in Africa and Asia. Envenomations are exceedingly rare in the US and are limited to exotic snake handlers.
    D) WITH POISONING/EXPOSURE
    1) MILD ENVENOMATIONS: Bites by most old world colubrids have only been reported to cause minor envenomation syndromes, including mild local swelling, inflammation or discoloration, transient local pain or bleeding, stiffness or numbness at the bite site. Systemic symptoms such as nausea, headache, and rigors have occasionally been described.
    2) MODERATE ENVENOMATIONS: Bites by the Malpolon monspessulanus (Montpellier snake) can cause moderate envenomation. Severe local swelling may develop, with paresthesia at the bite site, lymphangitis, and vague constitutional symptoms (nervousness, paresthesias of the limb). A few case reports have described ptosis and weakness of the muscles of respiration and deglutition, which resolved within 48 hours. There is limited information about Madagascarophis meridionalis envenomation, but it can produce extensive local swelling.
    3) SEVERE ENVENOMATION: Bites by Dispholdius typus (boomslang), Thelotornis capensis or kirtlandi (bird, twig or vine snakes), Rhabdophis subminiatus (red-necked keelback) or R. tigrinus (Yamakagashi or Japanese garter snake) can cause severe, potentially lethal envenomation. There is usually little initial pain and minimal swelling. Severe coagulopathy and disseminated intravascular coagulation may develop within a few hours of the bite, or may be delayed. Headache, nausea, vomiting and abdominal pain may develop early. Clinical bleeding manifestations may be severe and may not develop for 12 hours or more. They may include bleeding from the bite site (usually an early manifestation), hematuria, bleeding from venipuncture sites, hematemesis, melena or hematochezia, superficial ecchymosis, bleeding from gums, nose or ears, and subarachnoid or intracranial hemorrhage. Hemolysis and renal failure may develop. Laboratory manifestations include prolonged INR and PTT, elevated fibrin degradation products, decreased fibrinogen, thrombocytopenia and anemia.

Heent

    3.4.3) EYES
    A) WITH POISONING/EXPOSURE
    1) Blurred vision was reported in an adult following envenomation by a Montpellier (Malpolon monspessulanus) species. Spontaneous nystagmus, partial oculomotor paralysis with ptosis and complete accommodation paralysis was found on exam. Oculomotor paralysis resolved completely by day 6 (Pommier & deHaro, 2007).
    3.4.5) NOSE
    A) WITH POISONING/EXPOSURE
    1) Bleeding from the nose, eyes, and ears may develop in patients with severe coagulopathy after envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) species (Nicolson et al, 1974; Smeets et al, 1991).

Cardiovascular

    3.5.2) CLINICAL EFFECTS
    A) TACHYCARDIA
    1) WITH POISONING/EXPOSURE
    a) Mild tachycardia has been reported after severe boomslang and Rhabdophis species envenomation, likely secondary to blood loss (Geddes & Thomas, 1985; Cable et al, 1984; du Toit,DM, 1980).

Respiratory

    3.6.2) CLINICAL EFFECTS
    A) HEMOPTYSIS
    1) WITH POISONING/EXPOSURE
    a) Hemoptysis may develop in patients with coagulopathy or hemolysis after severe envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) species (Seow et al, 2000; Beiran & Currie, 1967; Lakier & Fritz, 1969).

Neurologic

    3.7.2) CLINICAL EFFECTS
    A) HEADACHE
    1) WITH POISONING/EXPOSURE
    a) Headache is a common early manifestations after envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) species (Gomperts & Demetriou, 1977; Cable et al, 1984).
    B) DECREASED LEVEL OF CONSCIOUSNESS
    1) WITH POISONING/EXPOSURE
    a) Decreased level of consciousness was reported in a patient with severe Dispholidus typus (boomslang) envenomation, without associated intracranial hemorrhage (du Toit,DM, 1980).
    C) INTRACRANIAL HEMORRHAGE
    1) WITH POISONING/EXPOSURE
    a) Fatal intracranial hemorrhage has been reported after R. tigrinus envenomation, and could occur with severe Dispholidus or Rhabdophis secondary to coagulopathy (Warrell, 1995a).
    D) PARESTHESIA
    1) WITH POISONING/EXPOSURE
    a) Paresthesias at the bite site have been reported from old world colubrids that are only capable of mild envenomation (Warrell, 1995a; Perry, 1988), by Malpolon monspessulanus (Montpellier snake) (Gonzalez, 1982), and by Dispholidus, Thelotornis and Rhabdophis species (Geddes & Thomas, 1985; Atkinson et al, 1980).
    b) A compression neuropathy developed in a patient with a large iliopsoas hematoma secondary to coagulopathy after Rhabdophis subminiatus (red necked keelback) envenomation (Seow et al, 2000).
    E) MUSCLE WEAKNESS
    1) WITH POISONING/EXPOSURE
    a) Ptosis, dyspnea, dysphagia and in one case severe neurotoxicity have been reported after evenomation by Malpolon monspessulanus (Montpellier snake) envenomation (Gonzalez, 1982). Weakness resolves within 48 hours with supportive care.
    b) Asthenia and ptosis were reported in another patient envenomated by Malpolon monspessulanus (Montpellier snake) species who developed only mild symptoms. The patient recovered completely following supportive care (Pommier & deHaro, 2007).
    F) GENERALIZED EEG AMPLITUDE ASYMMETRY
    1) WITH POISONING/EXPOSURE
    a) CASE REPORT: A patient bitten by a dog-faced fresh water (Cerberus rhynchops rhynchops) demonstrated diffuse abnormal sharp waves or spikes and slow theta and delta waves on an EEG (Ramachandran et al, 1995).

Gastrointestinal

    3.8.2) CLINICAL EFFECTS
    A) NAUSEA AND VOMITING
    1) WITH POISONING/EXPOSURE
    a) Nausea and vomiting are common early manifestations after envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) species (Cable et al, 1984; Lakier & Fritz, 1969).
    B) ABDOMINAL PAIN
    1) WITH POISONING/EXPOSURE
    a) Crampy abdominal or epigastric pain have been reported after envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) species (Atkinson et al, 1980; Ferlan et al, 1983; Aitchison, 1990).
    C) GASTROINTESTINAL HEMORRHAGE
    1) WITH POISONING/EXPOSURE
    a) Hematemesis, melena and/or hematochezia may develop in patients with severe coagulopathy after envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) species (Cable et al, 1984; Aitchison, 1990).

Hepatic

    3.9.2) CLINICAL EFFECTS
    A) LIVER ENZYMES ABNORMAL
    1) WITH POISONING/EXPOSURE
    a) Elevated ALT and AST have been reported after severe envenomation by Dispholidus (boomslang) species (Gomperts & Demetriou, 1977); this appears to be related to hemolysis.

Genitourinary

    3.10.2) CLINICAL EFFECTS
    A) ACUTE RENAL FAILURE SYNDROME
    1) WITH POISONING/EXPOSURE
    a) Transient renal failure has been described after severe Dispholidus typus (boomslang) and severe R. subminiatus (red necked keelback) envenomation (Lakier & Fritz, 1969; du Toit,DM, 1980; Smeets et al, 1991).
    b) Permanent renal failure has been reported after R. tigrinus (Yamakagashi or Japanese garter snake) envenomation (Warrell, 1995a).
    B) HEMATURIA SYNDROME
    1) WITH POISONING/EXPOSURE
    a) Gross hematuria may develop in patients with coagulopathy or hemolysis after severe envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) species (Reitz, 1989; Seow et al, 2000).

Hematologic

    3.13.2) CLINICAL EFFECTS
    A) DISSEMINATED INTRAVASCULAR COAGULATION
    1) WITH POISONING/EXPOSURE
    a) Severe coagulopathy with features of disseminated intravascular coagulation is a hallmark of severe envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) species (Warrell, 1995a; Warrell, 1995).
    b) Laboratory findings may include:
    1) Prolonged INR and PTT, often with incoagulable blood (Aitchison, 1990; Seow et al, 2000)
    2) Decreased concentrations of factors II, V, VIII and X (Gomperts & Demetriou, 1977; Hoffmann et al, 1992; Cable et al, 1984)
    3) Decreased fibrinogen and increased fibrin degradation product (Hoffmann et al, 1992; Geddes & Thomas, 1985)
    4) Elevated D dimer (Hoffmann et al, 1992)
    5) Thrombocytopenia (Atkinson et al, 1980; Lakier & Fritz, 1969)
    6) Abnormal red cell morphology with evidence of hemolysis including anisocytosis, fragmented red cells, burr cells, spherocytosis, and macrocytosis (Nicolson et al, 1974; Lakier & Fritz, 1969).
    7) Anemia (Smeets et al, 1991)
    1) Clinical evidence of bleeding may develop within a few hours or may be delayed more than a day. Manifestations may include: bleeding from the bite site (often the earliest sign of bleeding); bleeding from venipuncture sites; hematomas at areas of recent trauma; epistaxis; bleeding from the gums, eyes and ears; hematemesis; hematochezia or melena, hematuria; hemoptysis; and intracranial hemorrhage.
    2) Laboratory and/or clinical evidence of coagulopathy may persist for more than a week in untreated patients (Smeets et al, 1991; Hoffmann et al, 1992; Cable et al, 1984).

Dermatologic

    3.14.2) CLINICAL EFFECTS
    A) EDEMA
    1) WITH POISONING/EXPOSURE
    a) Moderate local swelling may develop with Malpolon monspessulanus (Montpellier snake) envenomation (Pommier & deHaro, 2007; Warrell, 1995; Gonzalez, 1982).
    b) CASE SERIES: In a series of 5 bites by Coluber rhodorachis, mild local pain and tenderness occurred in all 5, but swelling was seen in only 3. Blisters and lymphadenitis occurred in one patient each (Malik, 1995).
    c) CASE REPORT: A 19-year-old man bitten on the hand by a Coluber rhodorachis immediately developed erythema and lymphangitis. Within 3 hours, the hand swelled to one and a half times normal size with minimal dull pain. The swelling subsided over 24 hours (Perry, 1988).
    d) With Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) bites, swelling is absent or minimal (Warrell, 1995; Warrell, 1995a).
    B) ECCHYMOSIS
    1) WITH POISONING/EXPOSURE
    a) Ecchymosis may develop at areas of traumatic injury patients with severe coagulopathy after envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Rhabdophis (red necked keelback, Japanese garter snake) species (Seow et al, 2000; Beiran & Currie, 1967; Nicolson et al, 1974).
    C) BLEEDING
    1) WITH POISONING/EXPOSURE
    a) Bleeding from the bite site is often one of the earliest clinical manifestations of coagulopathy in patients with severe envenomation by Dispholidus (boomslang), Thelotornis kirtlandi (bird, twig or vine snakes), and Dispholidus (boomslang) species (Hoffmann et al, 1992; Beiran & Currie, 1967; Aitchison, 1990).
    b) Bleeding from venipuncture sites is also fairly common in these patients (Nicolson et al, 1974).

Musculoskeletal

    3.15.2) CLINICAL EFFECTS
    A) RHABDOMYOLYSIS
    1) WITH POISONING/EXPOSURE
    a) In a series of 5 patients envenomated by Coluber rhodorachis, an elevated CPK was observed in 2 patients (Malik, 1995).

Laboratory Monitoring

Monitoring Parameters Levels

    4.1.1) SUMMARY
    A) MALPOLON MONSPESSULANUS (Montpellier snake): Monitor for local swelling, lymphangitis and tissue damage. Monitor for weakness or other evidence of neurotoxicity.
    B) DISPHODIDUS TYPUS (Boomslang), THELOTORNIS CAPENIS or T. KIRTLANDI (bird, twig or vine snake), RHABDOPHIS SUBMINIATUS (red-necked keelback) or R. TIGRINUS (Yamakagashi or Japanese garter snake): Monitor CBC with platelets, INR, PTT, fibrinogen and fibrin degradation products every few hours until stable. Monitor vital signs and evaluate for clinical evidence of bleeding. Monitor urinalysis and urine output. Monitor renal function, serum electrolytes, and liver enzymes in patients with coagulation abnormalities.
    C) Other old world colubrids: monitor for local swelling and tissue damage and systemic effects such as nausea or headache.
    4.1.2) SERUM/BLOOD
    A) DISPHOLIDUS TYPUS (BOOMSLANG), THELOTORNIS CAPENSIS OR T. KIRTLANDI (BIRD, TWIG OR VINE SNAKE), RHABDOPHIS SUBMINIATUS (RED NECKED KEELBACK) OR R. TIGRINUS (YAMAKAGASHI OR JAPANESE GARTER SNAKE)
    1) Severe bleeding and disseminated intravascular coagulation may develop after envenomation by Rhabdophis, Dispholidus or Thelotornis species. Monitor CBC with platelets, INR, PTT, fibrinogen and fibrin degradation products every few hours until stable. Monitor vital signs and evaluate for clinical evidence of bleeding.
    2) Monitor renal function and liver enzymes in patients with coagulation abnormalities.
    B) MALPOLON MONSPESSULANUS
    1) MALPOLON MONSPESSULANUS (Montpellier snake): Monitor for local swelling, lymphangitis and tissue damage. Monitor for weakness or other evidence of neurotoxicity.
    4.1.3) URINE
    A) DISPHOLIDUS TYPUS (BOOMSLANG), THELOTORNIS CAPENSIS OR T. KIRTLANDI (BIRD, TWIG OR VINE SNAKE), RHABDOPHIS SUBMINIATUS (RED NECKED KEELBACK) OR R. TIGRINUS (YAMAKAGASHI OR JAPANESE GARTER SNAKE)
    1) Monitor urinalysis and urine output.

Treatment

Life Support

    A) Support respiratory and cardiovascular function.

Patient Disposition

    6.3.6) DISPOSITION/BITE-STING EXPOSURE
    6.3.6.1) ADMISSION CRITERIA/BITE-STING
    A) A patient with a Boomslang, Twig Snake, and Rhabdolphis envenomation should be admitted and any patient with more than minimal local effects should be admitted.
    6.3.6.2) HOME CRITERIA/BITE-STING
    A) Any patient with a colubrid bite should be sent to the hospital. Most species are nonvenomous, but the species may be uncertain at presentation.
    6.3.6.3) CONSULT CRITERIA/BITE-STING
    A) A medical toxicologist, toxinologist or poison center should be consulted for all symptomatic patients, if antivenom use is considered or if the species is uncertain.
    B) In the US, envenomations are likely to occur in zoos, or academic or private collector settings. Snake identification may be inaccurate in non-institutional settings. Obtaining an accurate identification of the snake is of utmost importance in order to guide treatment and monitoring. When dealing with private collectors, consideration should be given to independently verify the snake species. A regional poison center can assist with envenomation management, including obtaining antivenom when available (eg, boomslang envenomation), and should be contacted whenever a patient develops unexpected symptoms after being bitten by a snake. A local zoo or aquarium may be of assistance in identifying the snake.
    C) Information found on the Online Antivenom Index (www.aza.org/AI/Index) can be provided by a regional poison center by contacting 1-800-222-1212.
    D) Consult with a surgeon if necrotic areas develop.
    6.3.6.5) OBSERVATION CRITERIA/BITE-STING
    A) Patients should be observed for the development of local or systemic evidence of envenomation for 8 to 12 hours. Patients with a clear nonvenomous species envenomation can be discharged after wound care.

Monitoring

    A) MALPOLON MONSPESSULANUS (Montpellier snake): Monitor for local swelling, lymphangitis and tissue damage. Monitor for weakness or other evidence of neurotoxicity.
    B) DISPHODIDUS TYPUS (Boomslang), THELOTORNIS CAPENIS or T. KIRTLANDI (bird, twig or vine snake), RHABDOPHIS SUBMINIATUS (red-necked keelback) or R. TIGRINUS (Yamakagashi or Japanese garter snake): Monitor CBC with platelets, INR, PTT, fibrinogen and fibrin degradation products every few hours until stable. Monitor vital signs and evaluate for clinical evidence of bleeding. Monitor urinalysis and urine output. Monitor renal function, serum electrolytes, and liver enzymes in patients with coagulation abnormalities.
    C) Other old world colubrids: monitor for local swelling and tissue damage and systemic effects such as nausea or headache.

Range Of Toxicity

Summary

    A) SEVERE ENVENOMATION: A single bite from a Dispholidus typus (boomslang), Thelotornis capensis or T. kirtlandi (bird, twig or vine snake), Rhabdophis subminiatus (red necked keelback) or R. tigrinus (Yamakagashi or Japanese garter snake) snake can cause severe bleeding and coagulopathy or, rarely, death.
    B) MODERATE ENVENOMATION: Malpolon monspessulanus (Montpellier snake) bite can cause moderate local and systemic effects, but fatalities have not been reported.
    C) MILD ENVENOMATION: Bites by other old world colubrids may cause mild local or systemic effects.

Minimum Lethal Exposure

    A) A single bite from a Dispholidus typus (boomslang), Thelotornis capensis or kirtlandi (bird, twig or vine snake), Rhabdophis subminiatus (red necked keelback) or R. tigrinus (Yamakagashi or Japanese garter snake) snake can cause severe bleeding and coagulopathy or, rarely, death (Warrell, 1995; Warrell, 1995a).

Maximum Tolerated Exposure

    A) A single bite from Dispholidus typus (boomslang), Thelotornis capensis or kirtlandi (bird, twig or vine snake), Rhabdophis subminiatus (red necked keelback) or R. tigrinus (Yamakagashi or Japanese garter snake) can cause severe bleeding and coagulopathy or, rarely, death (Warrell, 1995; Warrell, 1995a).
    B) Malpolon monspessulanus (Montpellier snake) bite can cause moderate local and systemic effects, but fatalities have not been reported (Warrell, 1995).
    C) Bites by other old world colubrids may cause mild local or systemic effects (Warrell, 1995).
    D) CASE REPORT: A 16-year-old boy was bitten on the hand by a Chrysopelea paradisi and moderate pain was the only symptom reported. The patient was treated with an oral analgesic and prophylactically treated with tetanus and antibiotics and discharged after 6 hours of observation (Tan et al, 2012).

Pharmacology Toxicology

Toxicologic Mechanism

    A) A toxic protein that causes death in mice, with profuse bleeding from the nostrils, has been isolated from the Duvernoy gland secretions of the colubrid snake Malpolon monspessulanus (Rosenberg et al, 1992).
    B) The venoms of D. typus (boomslang) and Thelotornis species contain enzymes that activate prothrombin and may activate Factor X (Warrell, 1995; Hoffmann et al, 1992). Laboratory evaluation of a man with boomslang envenomation revealed activation of compliment by the alternative pathway (Nicolson et al, 1974). There is evidence supporting the presence of class P-III/P-IV venom metalloproteinases (SVMP) in boomslang venom. In viperid species, many of the coagulopathic and hemorrhagic effects of their venom are attributed to SVMPs (Kamiguti et al, 2000). The venoms of the Asian Rhabdophis subminiatus and R. tigrinus also contain a prothrombin activator (Warrell, 1995a) and R. subminiatus venom exhibits antithrombin III activity, resulting in defibrinogenation and hemorrhage (Li et al, 2001).
    C) The clinical result is a disseminated intravascular coagulation-like syndrome, with deposition of microthrombi, consumption of fibrinogen, and subsequent impaired clotting and clinical bleeding. Thrombocytopenia, anemia, and red cell fragmentation may develop (Lakier & Fritz, 1969).
    D) Most colubrid venoms display proteolytic activity, although with variable levels. Low phosphodiesterase activity is present in Amphiesma stolata. Diadophis punctatus, Heterodon nasicus kennerlyi, H. n. nasicus and Thamnophis elegans vagrans. Acetylcholinesterase has been found in Boiga irregularis venom. High phospholipase A2 (PLA2) activity was found in Trimorphodon bicutatus lambda venom and moderate levels in Boiga dendrophila, and D. p regalis venoms, and B. dendrophila and H. n. snasicus saliva. No venoms or saliva from 12 colubrid species studied displayed hyaluronidase, thrombin-like, or kallikrein-like activities (Hill & Mackessy, 2000). Boiga dendrophila venom has components that exhibit purinergic and muscarinic receptor activity (Lumsden et al, 2004).

Animal Toxicology

Clinical Effects

    11.1.3) CANINE/DOG
    A) Two small dogs envenomated by a boomslang snake developed uncontrolled bleeding. They both recovered after receiving monospecific boomslang antivenom (Hoole & Goddard, 2007).

Continuing Care

    11.4.3) TREATMENT
    11.4.3.5) SUPPORTIVE CARE
    A) Two small dogs envenomated by a boomslang snake developed uncontrolled bleeding, which stopped within 45 minutes of monospecific boomslang antivenom administration, including improvement in aPTT and PT (Hoole & Goddard, 2007). However, one dog developed anaphylaxis including dyspnea, nystagmus and vomiting; symptoms resolved with IV steroids and symptomatic care.

References

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