• Though there are about 20,000 species of predominantly venomous spiders in the United States, most lack fangs capable of penetrating human skin or toxin strong enough to produce more than a mild reaction.
• Two species, however, can cause significant harm.
• The black, red, and brown widow spiders (Latrodectus mactans species) and brown recluse spiders (Loxosceles reclusa species) can cause severe local and systemic reactions, including death.

• While there are about 120 snake species in this country, only 15% envenomate poisonous substances capable of causing fatal reactions.
• About 8,000 people annually in the United States sustain a poisonous snake bite, and 12 to 15 fatalities occur.
• Four of the 20 species of poisonous snakes found in North America are responsible for the majority of bites: Crotalinae (pit viper family: rattlesnakes, cottonmouths, copperheads), and Elapidae (coral snake).

• Small local reactions: painful, pruritic, urticarial lesion at the sting site
• Large local reaction: swelling and erythema, about 5 cm in diameter. May cross joint boundary and decrease function.
• Systemic anaphylactic reaction: some combination of generalized cutaneous manifestations (urticaria, edema, pruritus), gastrointestinal symptoms, upper or lower airway compromise, and hypotension

• Local reaction: pain, erythema, swelling, and pruritus.
• Ischemia and skin necrosis: A bright red papule appears within a few hours of the bite and can evolve within 48 to 72 hours into a hemorrhagic vesicle surrounded by purple discoloration (necrosis) or blanching (vasospasm). Shortly after, a firm, star-shaped, purple necrotic lesion appears, and within 7 to 14 days black eschar is visible. Ulcer healing can take weeks to months.
• Systemic reaction of black widow bites: muscle cramping, hypertension, tachycardia, and cholinergic effects (diaphoresis, salivation, lacrimation, and bronchorrhea) may be accompanied by abdominal rigidity or chest tightness. Nausea and vomiting are seen. Mortality in young children is as high as 50% and results from cardiovascular collapse.

• Crotalidae (pit viper) bites
  • Intense local pain and burning occur initially, followed by edema and perioral numbness that extends to the scalp and periphery.
  • Local ecchymosis and vesicles appear within the first few hours, and by 24 hours hemorrhagic blebs are present.
  • Necrosis extending throughout the bitten extremity generally ensues without treatment.
  • Nausea, vomiting, weakness, chills, and sweating can also occur.
  • Within several hours neuromuscular involvement can develop (diplopia, dysphagia, lethargy, etc.).
  • The dramatic and life-threatening effects are hypovolemic shock, hemorrhagic diathesis, and neuromuscular dysfunction.
• Elapidae (coral snake) bites
  • Characterized by mild local signs and symptoms (pain, swelling), but significant neurologic effects that include extremity paresthesias, weakness, fasciculations, and bulbar dysfunction that can progress to flaccid paralysis.

• Fortunately, most injury from animal bites is trivial, but infections are not uncommon, and fatalities do occur rarely.

• Dogs are responsible for 90% to 95% of cases, while the remainder of cases are divided as follows: cats, 3% to 8%; rodents or rabbits, 1%; and raccoons and other animals, 1%. Ninety percent of the offending animals are well-known to the victim.
• Though fatalities from animal bites are rare, the majority occur in the pediatric population. Considerable morbidity does occur: 10% require suturing, 5% to 50% develop into infections, 30% cause disability, and 50% leave scars.

• Brown recluse spider bite: other spider bites, insect bites and stings, poison ivy/oak, Stevens-Johnson syndrome, toxic epidermal necrolysis, erythema nodosum, chronic herpes simplex, purpura fulminans, diabetic ulcer
• Black widow spider bites: acute abdomen, renal colic, opioid withdrawal, and tetanus
• Poisonous snake bites: non-poisonous snakebite (leaves scratches, not punctures), rodent bites, thorn wounds

• Type of animal
• Apparent health of the animal
• Any provocation for the attack
• Location of the bite
• Rabies immunization status of the animal
• Tetanus immunization status of the child

• A description of the offender is important (particularly spiders).
• The black widow, about the size of a quarter, should be described as glossy black, gray, or brown with a red, orange, or yellow hourglass-shaped marking on the ventral surface of the abdomen.
• The brown recluse spider is small (1 to 1.5 cm), with a characteristic brown violin-shaped mark on the dorsum of the cephalothorax (see Associated Diseases and Complications, for details of presenting signs and symptoms).

• A pit just in front of the eye
• Fangs instead of rows of small teeth
• Elliptical or slitlike pupil
• Single row of subcaudal plates
• Somewhat triangular shape to the head
• Presence of rattles (at times)
• The Elapidae (coral snakes) are red, yellow, and black striped (specifically, red stripes bordered by yellow stripes) snakes. They have round pupils and rows of small teeth.
• Non-poisonous snakes also have round pupils, rows of small teeth, no pit, and a double row of subcaudal plates.

Test: Brown recluse spider bites—platelet count for evidence of hemolysis is needed as well as monitoring of hemoglobin, urine sediment, blood urea nitrogen (BUN), and creatinine.
Significance: Evidence of hemolysis and renal failure.

Test: Black widow spider bites—follow complete blood count (leukocytosis may be seen), hemoglobin, hematocrit, reticulocyte count, tests for hematuria (urinalysis, renal profile), blood glucose, and electrolytes.
Significance: In severe cases, elevated creatine kinase has been reported.

• Copious irrigation of the wound should be performed with at least 500 mL lactated Ringer solution or normal saline with a 19-gauge angiocatheter attached to a syringe.
• Devitalized tissue needs debridement.
• Primary closure of wounds by suturing is controversial, but the consensus now appears to be in favor of bite wound closure.
• Because of the propensity for infection, hand wounds are an exception and probably should not be sutured.

• Are indicated for wounds with obvious infection and wounds at high risk for becoming infected; deep punctures, cat bites, non-superficial hand wounds, and non-superficial facial wounds.
• Treatment with amoxicillin and clavulinic acid (Augmentin) or penicillin plus a penicillinase-resistant penicillin is suggested.
• Rabies prophylaxis (see Rabies chapter): recommended for bites by bats, skunks, raccoons, foxes, coyotes, and unknown, unobservable dogs and cats. It is not recommended following bites by observable healthy dogs and cats or most rodents and lagomorphs (hares and rabbits). Human rabies immune globulin (RIG): 20 IU/kg body weight (one-half infiltrated into wound, the remainder intramuscularly); human diploid cell rabies vaccine (HDCV): 1.0 mL intramuscularly on days 0, 3, 7, 14, and 28. (Rabies vaccine adsorbed [RVA] can be used alternatively at the same dosage.)
• Tetanus prophylaxis: Most children are fully immunized. Those who are not may require adsorbed tetanus (and diphtheria) toxoid. Tetanus immune globulin, a human product used for passive immunization, is required only in dirty wounds sustained by children with inadequate or uncertain immunization history.

• If the stinger remains in the skin, it should be removed by flicking or scraping with a fingernail. Mild reactions can be treated with ice or cold compresses. Moderate reactions may require an antihistamine such as diphenhydramine orally for several days. Mild or severe anaphylactic reactions require epinephrine 1:1000 solution 0.01 mL/kg (maximum, 0.3 mL) subcutaneously followed by diphenhydramine and a corticosteroid PO or IV.

• To alleviate muscle pain and cramping, an opioid (morphine or meperidine) alone or in combination with a benzodiazepine can be used.
• 10% calcium gluconate may also be given slowly by intravenous with electrocardiographic monitoring.
• Methocarbanol (Robaxin) is a muscle relaxant, and can be given q6h if needed.
• Lactrodectus antivenom is available and should be administered as soon as possible. For children less than 40 kg the usual dose is 2.5 mL (one vial). For children weighing more than 40 kg, the following are specific indications for antivenom use: age >16 years, respiratory difficulties, or significant hypertension.

• Mild bites: Frequent cleaning with soap and water, ice compresses initially, immobilization and elevation, use of diphenhydramine for pruritus, and an analgesic may also be considered.
• Large necrotic areas may require surgical excision and skin grafting.
• Antivenom is not yet commercially available.
• The use of dapsone is controversial. Current recommendations are to limit its use to adults with proven brown recluse bites. Dapsone should not be used in children because of the risk of methemoglobinemia.

• Rapid transport to medical facility, removal of jewelry/clothing from affected extremity, immobilization of the area in position of function below level of heart.
• A constriction band is indicated when incision and suction are called for or when anticipated transport will be longer than 30 to 60 minutes.
• Incision and suction are helpful only for pit viper bites when started within 5 to 10 minutes of the bite.
• After constriction band placement, linear incisions (1 × 0.05 cm deep) should be made through the fang marks, and suction with a snake bite kit suction cup applied for 30 to 60 minutes.
• If possible, the snake should be killed and brought in for identification. The head of a dead snake must be handled with care because it can deliver a venomous bite for up to 1 hour after death/decapitation.
• The use of antivenom is the mainstay of treatment.
• There are two types of antivenom, one for North American pit vipers and the other for Eastern coral snakes.
• Three to 20 vials may be required after skin testing for sensitivity to horse serum.
• Intravenous dosing is guided by serial measurements of the circumference of the extremity.
• The following should also be considered:
  • Treatment of shock with intravenous fluids
  • Analgesic use
  • Broad-spectrum antibiotic administration for extensive tissue involvement
  • Tetanus prophylaxis

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