Spider Bites Highly Unlikely to Cause Bacterial Infections, Study Finds
Last year, spider expert Richard S. Vetter, a former staff research associate at the University of California, Riverside, debunked the myth that venomous spiders are commonly found in bananas and other international cargo.
Now he and a team of scientists have set their sights on another spider-related question that is circulating among the medical community — namely, whether spider bites can provoke infections or be carriers of human pathogens.
Vetter and colleagues data-mined the history of publications on spider envenomations to conclude that the evidence for spider-vectored infection is scanty. Further, the researchers note that the mere presence of bacteria on spider fangs or mouthparts does not establish spiders as vectors for these bacteria.
The study results appear as a letter to the editor in the journal Toxicon.
“Although spider bite may be an attractive and tenable causative agent of a bacterial infection, the data show this is highly improbable,” Vetter said. “Any implied causative association between skin infections and spider bites should be considered suspect. The medical community should not scapegoat spiders for bacterial infections. When examining reports of thousands of spider bites of many species worldwide, we found almost no mention of infection associated with the arachnid-inflicted injury.”
Another problem occurs when people mistake bacterial infections for spider bites. However, Vetter explained that an important advancement in spider bite diagnosis in recent years shows that bacterial infections have been commonly misattributed as spider envenomation by both physicians and patients.
“‘Spider bite’ is used as a default diagnosis despite lack of supporting evidence,” he said. “In a study published three years ago, of 182 Southern Californian patients presenting with complaint of spider bite, less than four percent had spider envenomations, while about 86 percent had skin infections.”
He mentioned that the only credible report of spider bite leading to infection that his research team is aware of is an episode involving an Australian golden silk spider, a very large orbweaver.
“It resulted in colonization by a bacterium rarely found in humans,” he said. “The bite led to a pus-filled lesion that persisted more than two months.”
Vetter’s advice to people concerned with skin infections is that both the medical community and the general public should stop blaming spiders as the cause of bacterial infections.
“This medical platitude is not supported by the history of spider bite data and could lead to misdiagnosed patients who then have an overzealous reaction that could, in turn, lead to the unwarranted development of arachnophobia in bite victims, possibly then requiring psychological desensitization to spiders or excessive use of pesticides in living spaces,” he said.
Vetter should know a thing or two about arachnophobia, having written an article about “Arachnophobic Entomologists” — scientists who are fascinated by six-legged insects, but are frightened by eight-legged spiders.
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