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Does anyone have a good idea about how many common/or uncommon spiders in the USA give a nasty enough bite to cause serious problems for people? I know the Brown Recluse can cause tissue necrosis(death) and the Black Widow is bad, though I don't know what the effects are.
I don't think of most spider bites as being much more than a possible annoyance. Am I delusional? Should I be more worried about getting bitten? Because right now I am not!
Thanks,
Helen
The brown recluse and the widow spiders (Latrodectus spp.) appear to be the only spiders in the US likely to have a bite of serious medical concern, and even with the brown recluse, there appears to be quite a bit of over/misdiagnosis. Whereas the effects of widow spider venom appear fairly characteristic/diagnostic, bites allegedly from recluse spiders are difficult to confirm unless one actually captures/sees the spider in the act of biting, as there are many other causes of necrotic skin lesions other than spider bites - see http://spiders.ucr.edu/.
Also, you will find references (particularly on the internet) to the bites of sac spiders (especially Cheiracanthium sp.) and hobo spiders (Tegenaria agrestis) causing necrotic lesions, but these do not appear serious.
With very few exceptions, all spiders are venomous, but in the vast majority of cases, bites are of no real consequence. However, as with bee/wasp venoms, some individuals react more severely than others, and may even experience general systemic reactions such as fever, malaise, stomach cramps, and nausea.
Hope this helps...
suunto, thanks for your input.
I agree, any insect or bug bite can cause an allergic reaction that can be life threatening. But luckily that is rare.
I will continue to enjoy the company of spiders around my house without worry. :-)
Suunto, Thanks for your informative and accurate response to this question :) I fully expected to find the replies full of innacuracies since that is the norm for these misunderstood creatures.
I am a spider enthusiest and while I have no formal training I have researched and observed the for sometime :)
I currently only keep several species of tarantula but I have kept 3 different species of Latrodectus in the past and L mactans many times over the past 13 or so years.
As far as L mactans I can vouch that they are actually very shy creatures that will run from human intrusion (if in the web) or play dead (if caught on the ground) unless they are actively guarding an egg sack or young. When guarding a fertile sack or young they tend to be quite protective. In all of my time workin with black widows I have never been bitten just by taking some basic precautions.
L reclusa and L mactans venom works on the human body in different ways. L reclusa has a necrotic venom they breaks down the tissue radiating outward from the site of the bite. Only about 20% of the population has a serious reaction to the venom. A black widow has a neurotoxin, the venom affects the pain receptors. It is rarely fatal except in cases of the very young, elderly or infirmed. Results of envenomation include varying degrees of increased salivation and perspiration, numbness, muscle weakness, headache, nausea and vomiting, difficulty breathing and high blood pressure depending on the individual's sensitivity. There are actually four different species found in North america now, with L mactans, the Southern black widow, having the most potent venom.
While L reclusa is a wandering spider that never stays in one place for very long (a primary reason I have never kept this species) the black widow tends to set up house and once familiarized is very easy to locate by it's webs. The black widow prefers to live in cracks, crevices and other protected areas but it's tangled web will extend out from its 'hide' to catch happless prey that wanders by. I am in zone 7 and have seen widows alive and well in protected southern exposures even in the middle of winter (although they were much slower as a result of the cold weather.)
I have never killed the widows around the outside of my home and have had 4 children playing in areas where widows are known to coexist. The only precaution I have ever taken is checking the rims and undersides of toys and making sure the children could identify likely Latrodectus webs and the spiders themselves. One summer we even watched a large female find a mate and raise her young about two feet to the left of my front door with no incident and none of the young finding their way inside. They most definitely are not as fearsome as urban legends would lead you to believe!
I knew a friend of a friend who claimed to have gotten some unknown virus from a spider bite. Even though the bite wasn't poisonous, it did supposedly transmit some virus. The virus would occasionally cause him to break out in a cold sweat, and cause him to shake, he said. After I heard that I never tried to handle any spiders. However, I never researched this (that was in the early '80s before the Internet was popular), and that guy was unreliable about some things, so maybe he was wrong. Has anybody else heard of catching viruses from spiders?
To the best of my knowledge,there has never been any evidence of any viral transmission to humans by any spider, period. On the other hand, it is possible to get a secondary bacterial infection from the bite of a large spider (they seldom brush their fangs), just as you might from the bite of any other creature if you don't wash the wound thoroughly.
Interesting, suunto. That makes sense. For example, one of the worst effects of an alligator bite is the bacterial infection from the alligator's dirty teeth, which are frequenty in contact with stagnant water. Also, your story sounds the same as for plant viruses: although there is no documented case of a plant virus being transmitted to a human (to my knowledge, the last I heard), it's cautioned that people don't take chances on being the first to catch such a virus, therefore it's best to avoid contact with infected plants. For that matter, there's no documented case of a human being eaten by a killer whale, either, but obviously killer whales are fully capable of bestowing that honor upon some hapless human.
We get "spider bites" a few times a day from the ER. I work in microbiology and we culture these "spider bites". Funny thing about these "spider bites", there is never a spider to go with them, it is just assumed that a spider is responsible for the wound. These things used to be called boils and carbuncles but for some reason there is a huge urban myth about spider bites. A few years ago I found an article on the web cautioning ERs from diagnosing these MRSA and other bacteria infections as spider bites but I can't find it now. We have a poster in the department of some boils and other infections and how they are mistaken for "spider bites"
Most spiders cannot even break the skin of a human. I run around in the woods quite a bit and run into webs all the time. I used to dance around a bit but I don't even react anymore. I also frequentlly photograph, relocate, and otherwise interact with spiders and for some reason have never been bitten by a spider.
And there are no virus transmissions by spiders that I have heard of either. I wonder what the next hysterical myth will be.
My daughter made a nurse a couple of years back and she has been scared to death of mersa ever since. She found some little red bumps on her back that reminded her of spider bits and she thought it could be this flesh eating bacteria. I don't know what could have cause it but it went away to her relief.
But get this, I constantly get spider venom in my eyes. That is right, 4 times now it has happened. I kill them with my hand and get so busy cleaning that I forget, wipe my eyes , and get it in there. It causes the eye to burn, itch, feels like something is in my eye, and it causes the flesh around the eye to swell. Last year I got some in my eye while I was outside building a pergola. It actually caused the pupil to dilate. Boy did it hurt. One pupil dilated and the other pupil was real small from the sunlight. It scared my daughter to death when she came out to say bye to me before she went to work. She thought I had had a stroke!
And oh yes, I am no expert, but I did take a course in "Invertabrates" when I was working on my masters in biology. Spiders were the last section of that course. I believe that funnel spiders, the ones that build very thick webs in bushes like yews - are very poisonous. However, their fangs are so short that they can not pentrate our skins.
The only truly dangerous 'funnel web spiders' are those found in Australia (Atrax robustus and relatives - see http://tinyurl.com/2ho355). Those called funnel web spiders in the US belong to an entirely different family (Agelenidae), and although large specimens are capable of biting if you handle them carelessly, they are not dangerous.
