Chilean Recluse - Medical Significance

Medical Significance

As indicated by its name, this spider is not aggressive and usually bites only when pressed against human skin, such as when putting on an article of clothing. Like all sicariid spiders, the venom of the Chilean recluse contains the dermonecrotic agent, Sphingomyelinase D, which is otherwise found only in a few pathogenic bacteria. According to one study, the venom of the Chilean recluse (along with the six-eyed sand spider), contains an order of magnitude more of this substance than that of other sicariid spiders such as the brown recluse.

Some bites are minor with no necrosis, but a small number produce severe dermonecrotic lesions (cutaneous loxoscelism) or even systemic conditions (viscerocutaneous loxoscelism); sometimes resulting in renal failure and in 3%–4% of cases in a clinical study in Chile, death. (For a comparison of the toxicity of several kinds of spider bites, see the list of spiders having medically significant venom.)

The serious bites form a necrotising ulcer that destroys soft tissue and may take months, and very rarely, years to heal, leaving deep scars. The damaged tissue will become gangrenous and eventually slough away. Initially there may be no pain from a bite, but over time the wound may grow to as large as 10 inches (25 cm) in extreme cases. Bites may take up to seven hours to cause visible damage; more serious systemic effects may occur before this time, as venom of any kind spreads throughout the body in minutes. Deaths have been reported for the related South American species L. intermedia.

First aid involves the application of an ice pack to control inflammation, the application of aloe vera to soothe and help control the pain, and prompt medical care. If it can be captured, the spider should be brought with the patient in a clear, tightly closed container for identification. However, by the time the bite is noticed any spider found nearby is not likely to be the culprit.