Warning: if you do not like spiders, or are squeamish, maybe don’t read this post!
When I was at university, I found a red bump on my elbow that progressed to an actual hole. Many doctor’s visits and anti-inflammatory steroid injections later, I had an impressive scar and perhaps, an impressive story.
A persistent myth
My doctor told me that the hole was the result of a white-tailed spider (Lampona cylindrata and Lampona murina) bite, which causes tissue necrosis. Anyone in Australia has heard about people being bitten by a white-tailed spider and ending up requiring multiple skin grafts, or in the worse case scenario, amputation! In actual fact, spider bite-induced necrosis (necrotic arachnidism) is linked to only one spider, the Brown recluse (Loxosceles reclusa), which is found in the southcentral and southeastern areas of the United States. A compound found in the spider venom creates an acute immune response that results in inflammation-driven tissue destruction.
The link between the white-tailed spider and tissue necrosis is in fact an urban legend that has persisted since the 1980s.
So if the white-tailed spider doesn’t actually cause tissue necrosis, how did I get a hole in my elbow?
The jury is still out
The theories put forward focus on mycobacterium ulcerans infection at the bite sites resulting in an ulcer, or Staphylococcus aureus infection resulting in cellulitis (bacterial skin infection).
It is unlikely that the majority of the cases are the result of a M. ulcerans infection. Firstly, this type of infection is predominantly localised to tropical areas, and is a highly contagious infection. Secondly, studies have shown that the white-tailed spider venom does not carry this bacterium.
The second theory, that the tissue necrosis is from S. aureus infection resulting in cellulitis, is more likely. I couldn’t find a straightforward answer, but it seems that most researchers and clinicians feel that the S. aureus infection occurs from entering at the site of broken skin, i.e. a bite site that someone has scratched.
So, despite a lack of evidence linking the white-tailed spider to necrotic arachnidism, the myth persists. I mean, what is going to have viewers glued to their TV or clicking on links:
“I lost my leg to a spider bite!” or, “I scratched a spider bite and now I have a bacterial infection!”
Tip: don’t enter tissue ulcer into Google images if you are of a weak constitution…!
This post was inspired by a recent post in Australian Geographic.