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First Aid for Spider Bites in Pets
Veterinary & Aquatic Services Department, Drs. Foster & Smith
Bites - Stings - Injuries
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Spider venom

Poisonous spiders such as the female black widows (Latrodectus) and brown recluse (Loxosceles)

General Information
Spider bites affect different areas of the body depending on the type of spider.

Toxic Dose
Varies depending upon species of spider, location of bite, and size and species of animal.

Black widow spider: Signs of the black widow spider bite include regional tenderness and numbness followed by hyperesthesia. Muscle pain (severe) and cramping of the muscles of the chest, abdomen, back, and other large muscles occur. Abdominal rigidity without tenderness is a classic sign of envenomation by the black widow spider. Seizures are possible. Respiration may be compromised because of the abdominal cramping. Muscle rigidity decreases with time followed by muscle paralysis. Increased blood pressure and heart rate may be seen. Death is caused by respiratory or cardiovascular collapse. Extremely sensitive to black widow spider bites, cats show signs of severe pain, drooling, restlessness, and early paralysis. Death is common in cats.

Brown recluse spider: Initially, bites from the brown recluse spider are not painful. The cutaneous form of reaction is seen within 2-6 hours of the bite with signs of localized pain and redness. A blister is seen within 12 hours of the bite; this lesion often progresses into the classic "bull's-eye" lesion. The skin dies and focal ulceration occurs within 7-14 days. Skin healing is very slow, taking several months, and scars may remain. The viscerocutaneous form with signs of fever, joint pain, weakness, vomiting, seizures, blood disorders, and kidney failure rarely occurs but is possible. Death is more likely if the viscerocutaneous form occurs.

Immediate Action
Identify the spider if possible. Seek veterinary attention.

Veterinary Care
General treatment: The area around the wound will be clipped and cleaned. A cold compress may be used in cases of recluse spider bites.

Supportive treatment: IV fluids and pain medication will be administered, and lab work performed to monitor organ function. For black widow spider bites, additional treatment may include medications for seizures and muscle cramping, and monitoring cardiopulmonary function. For brown recluse spider bites, additional treatment includes debriding the affected tissues, irrigating the affected areas with Burow's solution, and providing antibiotics. If available, hyperbaric oxygen for several days may be helpful.

Specific treatment: Antivenin may be given for black widow spider bites.


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