Monday, July 11, 2011

Something Worse Than Its Bite

Common House Spider, Tegenaria domestica
I can understand why people are afraid of spiders. I think its the scurrying movements. Stillness followed by an unpredictable dash. With the smaller, species its not a problem, but when the big boys dart across the semisolid laminate it can cause even the bravest among us a moments terror. Probably the most common culprit in cases in Ireland like this is the impressively sized Common House Spider (Tegenaria domestica), which generally has a body size of 10 mm, but can often be larger. Its is strongly associated with human activities, making webs with funnel entrances in many parts of houses and their external walls. It has a hairy body of variable colour, from pale to dark brown (1).
Common House Spider, Tegenaria domestica
While it is easy to scoff at (some may say irrational) fear of species like T. domestica, there is a health risk with the spider. It is not, as with many spiders worldwide, a risk of being bitten – species of spider in Ireland are not venomous unless you're smaller than a grasshopper – but something more intriguing. In 2005 it was reported (2) that a pig farmer in Tampere, Finland presented to the University Hospital there with eczema on his face, neck and hands. Isolation from and re-exposure to the sty in which he worked revealed the problem to lie there. It was also discovered that there had been an increase in the number of house flies (Musca domestica) in the sty in the past number of years, which had lead to an increase in the numbers of T. domestica. Skin prick tests preformed with T. domestica extract as well as its webbing were positive and Immunoglobulin E (IgE) immunospot tests with spider extract and patient serum proved similarly positive. Indeed the patient proved to be allergic to this species alone and not to any other spider or mites species often associated with similar allergic reactions.

  1. Sterry 2004. Collins Complete Guide to Irish Wildlife p. 154
  2. Hasan et al., 2005. Allergy 60 pp. 1455–1457

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