Spider Bite: Recluse Spider Bite

There are more than 30,000 recognized spider species in the world. But only about 100 defend themselves aggressively and have fangs long enough to penetrate human skin and can cause harm to humans. Bites of the most spiders are painful but do not cause any harm. The venom that spiders use to hunt their prey can cause necrosis of skin and systemic toxicity. Bites of spiders like brown recluse spiders, widow spiders and very few other species can be life threatening. Specific treatment for spider bite like widow and brown recluse spiders is available, so offending spider should be tried to identify. In many cases it is seen that injury is by something else but spiders are attributed as the offender.

The scientific name of the recluse spider is Loxosceles recluse. Recluse spiders are found southern and Midwestern USA. They are about 0.7 to 1.5 cm in body length and 2 to 4 cm in leg span. Recluse spiders are brown in color and they have violin shaped spot on their surface. Recluse spiders do not spin web. They are not aggressive toward humans and bite only when they are provoked or threatened, or pressed against skin. They invade homes particularly during fall and hide in undisturbed dark places like closets, in furniture, store rooms, garage, and folds of cloths. That is why bites are common while dressing and the common sites are arms, neck and abdomen. In wild they hide under rocks and logs and in animal burrows and caves. They emerge at night to hunt insects and other spiders.

The venom of recluse spider is clear and viscous and it contains an esterase, alkaline phosphatase, protease and other enzymes which produces hemolysis (breakdown of blood cells) and tissue necrosis (death of tissue). Sphingomyelinase B is the most potent enzyme which causes vascular thrombosis and tissue necrosis. At the beginning the bite is painless, but after few hours the site of the bite becomes painful and itching. The bite site becomes hard and it is surrounded by a pale zone (due to lack of blood and oxygen) and a zone of redness. Maximum cases the lesion resolve spontaneously without any treatment in a few days. But if it is not resolved within 2 to 3 days, the red surrounding spreads, the central pale becomes hemorrhagic and dies. This part sloughs off and a big ulcer forms which, may be sometimes as big as one foot in diameter. It eventually becomes a big depressed scar. Healing of the scar may take up to 3 to 6 months. If subcutaneous fat is involved it may take 3 years to heal properly. Complications of recluse spider bite include secondary infection and injury to nerves. Nausea, vomiting, weakness, fever, chills, headache, rash, painful muscles, arthralgia may develop after the bite. Very rarely renal failure, hemolytic anemia may cause death.

Treatment of Recluse Spider bite:

Initial treatment includes local cleansing of bite site, icepack, dressing and elevation and immobilization of limb if the bite site is limb. Treatment with painkillers, antihistaminics, antibiotics and tetanus prophylaxis is given. If lesion is becoming necrotic dapsone, a leukocyte inhibitor is given within 2 to 3 days, which prevent progression of the lesion. Dapsone (used in treatment of leprosy) is given at the dose of 50 to 100 mgs twice a day orally. Glucose 6 phosphate dehydogenase deficiency should be ruled out before giving dapsone. Loxosceles specific antivenom is not approved in USA. Cleaning of wound and removal of dead tissues should be done. Immediate surgical removal of wound is very useful in serious cases. Finally skin grafting is required in most cases. Patient should be observed for the development of renal failure, hemolysis and other systemic complications.

Preventive measures like wearing full sleeve heavy shirts, full trousers (not half pant or bermuda), and hand gloves should be kept in mind while working outdoor and in dark areas indoor in the localities where widow spiders are commonly found.

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