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History:  54 year-old male woodcutter working near Huao on the Urubamba River in a remote area of primary rainforest.  While looking for a place to camp after a 13 hour work day he was bitten on the left foot by a snake described as ?cascabel? about 50 cm long and being brown and grey.  The patient experienced a sharp pain in the bite area extending up the leg, with edema developing over the next hours but extending only to just above the ankle.  His mates performed a small incision at the bite site without suction or tourniquet application.  One vial of antivenom (most likely against Bothrops sp.) that was on hand was divided between the wound and intramuscularly into the left buttock.

During the 2-day boat ride to Atalaya, the nearest town, he felt dizzy and diffuse ecchymosis in the left buttock (starting over injection site) developed, as well as gross hematuria and oliguria.  Pain continued in the left leg up to the groin but diminished over time.  In Atalaya, 2 vials of antivenom were given intravenously at the Centro de Salud and he was airlifted to our hospital.

Epidemiology:  Born in, and lifelong resident of Atalaya in the high jungle of Ucayali, Perú.  At his present occupation for 5 years without witnessing any snakebite accidents.

Physical Examination:  Pale appearing.  Afebrile.  Hemodynamically stable.  Oliguric for previous 12 hours.  Mild edema of left foot with 2 small lesions on the dorsum suggestive of fang marks [see image A].  Extensive ecchymosis of the left leg to the buttock [see image B].  No spontaneous bleeding noted.

Laboratory Examination:  Hematocrit 25.  WBC 7,100 with 86% neutrophils, 16 lymphs.  Platelets 174,000 (initially 33,000).  INR 1.8. PTT 57.6/32.5.  Fibrinogen undetectable.  CK 460.  BUN 200.  Creatinine 8.9.  Total bilirubin 1.7.  Chest x-ray normal.

The Gorgas participants were asked to consider the likely snake species and whether, in addition to supportive care, further antivenom would be indicated several days after the snakebite.

By nature many snakebites occur in settings where some vials of antivenom may be available in the absence of laboratory facilities.  Using the bedside 20-minute clotting time test being demonstrated by Professor Warrell (on another patient without DIC; see image A), blood that fails to coagulate after 20 minutes in an untreated glass tube is a good indicator of incoagulability and an indication for antivenom administration.

Species of Bothrops are the most important cause of snakebite deaths and morbidity throughout the whole Amazon region, and account for most of the serious snakebites in Latin America.  Bothrops range from Mexico to Argentina and can adapt to habitats varying from grasslands to rainforest, with some being arboreal.  These are medium to long snakes (0.7 to 2.5 m) with heat-sensing pits between the eyes and the nostrils.  Description by the patient of the offending snake is most often unreliable.  In this case the patient thought he had been bitten by a ?cascabel? (literally ?rattlesnake?), which does not even occur in that particular region of Perú.  Description of the color of the snake, the fact that the snake was on the ground, its size and the well known use of ?cascabel? for juvenile Bothrops atrox in this area of Perú, and the known pre-eminence of Bothrops atrox in the locality make this the likely culprit.  An example is shown in image B.

Severe local necrosis and ecchymosis is more characteristic with vipers and pit vipers than with elapid snakes (cobras, mambas, coral snakes, kraits and others).  Necrosis was not a major component in this case but ecchymosis was.  This was in part due to iatrogenic cause.  Intramuscular or local wound injections of antivenom should not be done in general; the preferred route is intravenous.  This is more true for patients with a hemorrhagic diathesis.  This patient also had a right jugular catheter inserted for hemodialysis (before his blood coagulation had been fully normalised with further antivenom) with resulting complication [see image C].  With Bothrops other organ systems may also be involved, including cardiovascular (shock), renal (acute renal failure as in this case), hematologic (coagulopathy, thrombocytopenia, anemia from blood loss), and central nervous system (secondary to cerebral hemorrhage).

Fatalities due to Bothrops envenomation occur regularly among indigenous peoples in the Amazon basin.  In Perú the overall case-fatality rate is 1-3% of all bites.  However, the snakes are not aggressive and will only attack if disturbed.  Travelers should be educated to be alert when walking in the rainforest, to wear adequate boots, and to carry a flash light after dark.  The use of first aid measures such as compression/immobilization of an affected limb in viperidae envenomation is not indicated.  Local incision, as was done in this case, only increases the hemorrhagic loss of blood and the risk of further injury and infection, and suction of the wound can enhance local tissue necrosis and serves no purpose.  The aim should be to keep the whole patient as immobile as possible while being transported to hospital care quickly.  Expedition travelers to remote locations can consider carrying a supply of antivenom but its use does not obviate the need for rapid transport to a medical facility for management of IV fluid administration and support of cardiorespiratory compromise that may ensue.

With appropriate antivenom administration and supportive care, including hemodialysis, the patient recovered and was discharged after a week.

History:  54 year-old male woodcutter working near Huao on the Urubamba River in a remote area of primary rainforest.  While looking for a place to camp after a 13 hour work day he was bitten on the left foot by a snake described as ?cascabel? about 50 cm long and being brown and grey.  The patient experienced a sharp pain in the bite area extending up the leg, with edema developing over the next hours but extending only to just above the ankle.  His mates performed a small incision at the bite site without suction or tourniquet application.  One vial of antivenom (most likely against Bothrops sp.) that was on hand was divided between the wound and intramuscularly into the left buttock.

During the 2-day boat ride to Atalaya, the nearest town, he felt dizzy and diffuse ecchymosis in the left buttock (starting over injection site) developed, as well as gross hematuria and oliguria.  Pain continued in the left leg up to the groin but diminished over time.  In Atalaya, 2 vials of antivenom were given intravenously at the Centro de Salud and he was airlifted to our hospital.

Epidemiology:  Born in, and lifelong resident of Atalaya in the high jungle of Ucayali, Perú.  At his present occupation for 5 years without witnessing any snakebite accidents.

Physical Examination:  Pale appearing.  Afebrile.  Hemodynamically stable.  Oliguric for previous 12 hours.  Mild edema of left foot with 2 small lesions on the dorsum suggestive of fang marks [see image A].  Extensive ecchymosis of the left leg to the buttock [see image B].  No spontaneous bleeding noted.

Laboratory Examination:  Hematocrit 25.  WBC 7,100 with 86% neutrophils, 16 lymphs.  Platelets 174,000 (initially 33,000).  INR 1.8. PTT 57.6/32.5.  Fibrinogen undetectable.  CK 460.  BUN 200.  Creatinine 8.9.  Total bilirubin 1.7.  Chest x-ray normal.

The Gorgas participants were asked to consider the likely snake species and whether, in addition to supportive care, further antivenom would be indicated several days after the snakebite.