Treatment of Syndromes Linked to Spider Bites Ineffective

Research needed to identify and treat associated clinical syndromes of latrodectism, loxoscelism

THURSDAY, July 14 (HealthDay News) -- Latrodectism and loxoscelism are important worldwide clinical syndromes associated with spider bites, but the effectiveness of antivenom treatment is unclear, according to a review published online July 14 in The Lancet.

Geoffrey K. Isbister, M.D., from the University of Newcastle in Australia, and Hui Wen Fan, Ph.D., from Instituto Butantan in São Paulo, Brazil, reviewed through July 2010 to report the epidemiology, diagnosis, treatment, and prevention of medically important spider bites and associated clinical syndromes.

The authors report that there are two worldwide medically important clinical syndromes associated with spider bites: latrodectism caused by bites from widow spiders or Latrodectus spp, and loxoscelism caused by Loxosceles spp bites, mainly in South America. Other medically important spiders are located in specific regions such as the Australian funnel-web spider. Spider bites are diagnosed on the basis of a clear history of the spider bite and identification of the spider and/or the bite, and are often misdiagnosed or diagnosed late. Antivenom use has been less successful than in treatment of snake or scorpion evenomation. There are few studies on Latrodectus antivenom, and although Loxosceles antivenom is efficacious in vitro, delayed clinical presentation and the irreversibility of cutaneous necrosis means it may not be an effective treatment. Antivenom for funnel-web spiders is highly effective and potentially life-saving. Reduced contact between human beings and medically dangerous spiders is the best possible prevention for bites, and can be achieved through chemical control in human habitations.

"Studies are needed to prevent the unnecessary use of ineffective antivenom, which puts patients at risk of allergic reactions, and to better define the timing and dosing of antivenom when it is effective," the authors write.

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