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Spiders considered medically important

Author: Martin Overton


Time after time the question of "how dangerous are tarantulas and other spiders" raises its head. Before I answer this, the following needs to be considered:

  1. Allergic reactions to venom and urticating hairs vary from individual to individual.
  2. Other conditions, such as age, youth, heart problems, high blood pressure, etc. may influence a person's reaction to venom.
  3. Complications may appear that cause more damage than the injected venom or urticating hairs.

Lets address tarantulas first as this is the spiders that most of us are concerned about as we are in frequent contact with them, whether is be direct contact through handling (not advised!) or through indirect contact from bombardment or urticating hairs from substrate, etc.

To date there have been no substantiated deaths attributed to a bite from a tarantula. This said though, there have been concerns that certain old-world species; such as Poecilotheria may have high venom potential. The same goes for a number of Australian species. Of course the reaction of one individual to a particular species venom cannot be used as a reliable measure. We need a suitable cross section of individuals that have been bitten to make a sound general statement as to the effect of being bitten by a particular species.

Concerns have also been raised regarding urticating hairs and the possible damage they may cause. Suggestions include, partial or total blindness, cataracts, breathing problems (burning nose, throat, etc.) and severe urticaria that may re-occur years after the original bombardment.

Of course the documented proof for many of the above is lacking, or merely resides in the imagination of the media who 'smell a good story'.

To try and resolve the lack of documented proof on bites and bombardment from tarantulas I have created a survey on my web site. (at http://arachnophiliac.com)

The purpose of this survey is to get first hand feedback from individuals that have suffered an attack. The results from this survey will be used to write a paper for publication in the BTS journal (and any other societies that are interested, both arachnid and medical) and also to be used in the on-line species database I'm setting up.

Other spiders that have been documented as being of medical importance (unlike tarantulas) are:

Black Widow Spiders (Latrodectus sp.)
This is probably the best known 'dangerous' spider. Found throughout the world, including America, New Zealand and Australia. The female is the one responsible for biting humans (the males are considered to be harmless, as they can't pierce the skin). There have been recorded deaths attributed to it. It is known by a number of common names: Katipo (New Zealand) and Red Back (Australia). An antivenin was developed in 1956 and is effective if used within 80 hours.

The most frequently encountered of this species are: L. mactans and L. hesperus.

Brown Spiders (Loxosceles sp.)
The spider is widespread in the southern half of the USA and may also be resident further south. The member of this species that comes into contact with humans most frequently is known as the Brown recluse (or Violin spider) (L. reclusa). This has been blamed for a number of deaths (5) in the US amongst young children and the aged. There are a number of others in this family, including L.deserta and L. laeta.

One interesting side note is that problems from bites of this spider, could be compounded by Streptococcal infection that lead to gangrenous limbs that require surgical amputation.

Brazilian Wandering Spiders (Phoneutria sp.)
This species of spider is feared in and around Brazil and there are reported cases of young children being killed by it. Little other information appears to be available about it's range and the effects of its venom.

Funnel Web Spiders (Atraxus sp.)
The Sydney Funnel Web (A. robustus) is the best known of this family as it frequently come into contact with humans. Unlike the Black Widow, the male of this species is the one to watch out for. The other main member of this family is known as the Tree Funnel Web (A. formidablis). The Sydney Funnel Web is widely reported by the Australian media and has gained a certain notoriety.

I would welcome your feedback on this short article. I believe that this could easily be expanded into a full article for one of the society journals (any society interested?)


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