My post, titled ‘Spiders do not bite‘, remains the most frequently visited post on my blog, receiving hundreds of hits each week. It was written over a year ago, and has received quite a number of interesting comments. Some people decide to comment without actually reading the post (!), and by in large, these comments come from people who just can’t be convinced that spiders rarely bite people. In other cases, people comment with a big “Thanks“, as the post has provided them some comfort (this is a key reason why I wrote the post). The title of that post was meant to be provocative, and to help swing the pendulum a bit, and be an antidote to the garbage out there on the Internet about spiders bites. I remain emphatic: spider bites are exceedingly rare and other causal agents are much more likely.

Just recently, I was thrilled to see another paper published by Rick Vetter (a well respected Arachnologist who has worked on debunking myths about spiders). This recent paper is titled “Spider Envenomation in North America” and was published in the journal Critical Care Nursing Clinics of North America. The paper was aimed at Nurses and to a lesser extent, Doctors, and gives frank, clear and concise information about spiders and spider bites.

Here’s the opening sentence: “Spiders occupy an interesting position in human society and in medicine. The overall health risk that they pose is minor compared with other routine events such as driving an automobile, vocational and recreational hazards, or living an unhealthy lifestyle”

Bingo. Spider bites are exceedingly rare!

Here is some more detail and context: there are only two groups of spiders in North America which can truly be considered ‘medically important’ – some species within the ‘widow’ group (e.g. black widows) and some within the ‘recluse’ group (e.g. brown recluse). Here’s a lovely photo of a brown recluse spider, courtesy of Matt Bertone (thanks, Matt, for permission to post the photo here!).

Much of Rick’s article documents the effects of bites from these two groups of spiders, and without a doubt, verified, real cases of spider bites from these two groups can certainly affect your health. Rick provides a clear list of symptoms and also discusses treatment options (including what used to be done, historically e.g., cocaine treatment for widow bites in the early 1900s). He also points out that the actual number of recorded, verified bites by spiders are quite rare, even in regions where widows and recluse spiders live in proximity to humans (um, I have to state that because recluse spiders are continually blamed for bites in areas well beyond their range!). Without doubt, poison control centres, Doctors, and other health care professionals hear panic about spider bites, and certainly see cases of lesions that are attributed (often by the affected person) to recluse spiders.

So, if it’s not spider bites, what is causing lesions? Thankfully, Rick provides an answer, and I quote from the paper: “Possibly the most important advance in spider toxicology is the realization that many skin lesions that were attributed to spider bites were actually bacterial infections… Another study showed that of 182 southern Californian patients seeking treatment for spider bites, only 3.8% had actual spider bites while 85.7% had infections“. So… more likely causal agents should be investigated. Here’s a table from a 2003 publication by Vetter et al. that lists some of the potential causal agents that could be confused with brown recluse bites.

In sum, I remain steadfast in the claim that spider bites are exceedingly rare. Furthermore, there are very few species that are medically important, and of the thousands of spider species that exist in North America, few warrant any concern or fear. Spiders are our friends. Arachnids deserve positive attention.

I’ll finish on a positive note: as I was preparing this blog post, I had some nice discussion with Rick about his crusade to reduce fear and anxiety about spider bites. He’s worked hard to publish articles in journals which are read by health care professionals, and he believes the strategy is working. Here’s a quote from Rick:

I have seen significant change in the medical literature where they are quoting my papers a lot and telling colleagues to be cautious with their diagnoses. There are still those out there that continue to misdiagnose but I think that they are now in the minority.

This is great news, and I am heartened. That being said, I think we must continue to provide clear and accurate information to a broad audience and to the news media. I believe general paranoia and hysteria about spider bites is still high despite a potential shift in diagnosis from the medical community.

References

UC (Riverside) Spider Site.

Vetter, R. (2013). Spider Envenomation in North America Critical Care Nursing Clinics of North America, 25 (2), 205-223 DOI: 10.1016/j.ccell.2013.02.006

Vetter RS, Cushing PE, Crawford RL, & Royce LA (2003). Diagnoses of brown recluse spider bites (loxoscelism) greatly outnumber actual verifications of the spider in four western American states. Toxicon : official journal of the International Society on Toxinology, 42 (4), 413-8 PMID: 14505942