Spiders belong to a group of animals called “arachnids”. Scorpions, mites, and ticks are also part of the arachnid family. Arachnids are creatures with two body segments, eight legs, no wings or antennae and are not able to chew. Many people think that spiders are insects but they are mistaken since insects have six legs and three main body parts. Most insects have wings.
Arachnids belong to an even larger group of animals called “arthropods” which also include insects and crustaceans (lobster, crabs, shrimp, and barnacles). This is the largest group in the animal kingdom! Approximately 80% of all animals are from this group…that would be over a million different species! There are more than 30 000 different species of spiders.All spiders are predators and many will eat other spiders. Scientists have found spiders in amber (Did you watch Jurassic Park?) that dates back to about 2 million years. Because spider’s skeletons are quite small and fragile it is difficult to find whole fossilized spiders
spider venom
Despite the terrible wounds often associated with brown recluse, they are much less likely to cause significant injury than black widows. Skin infections may cause boils, which are often misdiagnosed as brown recluse spider bites .It’s easier to figure out when a bite is not from a recluse than when it is. One tool to rule out brown recluse bites is to use the mnemonic NOT RECLUSE. This mnemonic helps point out things that are not present in brown recluse bites.Numerous: If there are more lesions than just one or two, they’re not from a brown recluse. Brown recluse bites come in ones and sometimes two.
Signs and symptoms
A study of 750 definite spider bites in Australia indicated that 6% of spider bites cause significant effects, the vast majority of these being redback spider bites causing significant pain lasting more than 24 hours. Activation of the sympathetic nervous system can lead to sweating, high blood pressure and gooseflesh.
spider bites
Most recluse spider bites are minor with little or no necrosis. However, a small number of bites produce necrotic skin lesions. First pain and tenderness at the site begin. The redness changes over two to three days to a bluish sinking patch of dead skin—the hallmark of necrosis. The wound heals slowly over months but usually completely. Rarely, bites may cause widespread symptoms, with occasional fatalities.
Cause
Spiders do not feed on humans and typically bites occur as a defense mechanism. This can occur from unintentional contact or trapping of the spider. Most spiders have fangs too small to penetrate human skin. Most bites by species large enough for their bites to be noticeable will have no serious medical consequences
Medically significant spider venoms include various combinations and concentrations of necrotic agents, neurotoxins, and pharmacologically active compounds such as serotonin. Worldwide only two spider venoms have impact on humans—those of the widow and recluse spiders. Unlike snake and scorpion envenomation. widow and recluse species bites rarely have fatal consequences. However, isolated spider families have a lethal neurotoxic venom: the wandering spider in Brazil and the funnel web in Australia. However, due to limited contact between these spiders and humans, deaths have always been rare, and since the introduction of anti-venom in Australia, there have been no funnel web related deaths
spider venom
In the United States, black widow spiders are considered the most venomous. They have a toxin capable of a systemic reaction that affects muscle and nerve function. Black widow spider bite symptoms can be used to diagnose these bites and include:
- “Fang” marks (tiny twin holes): telltale signs that are only visible right after the bite happens, before any swelling or redness occurs
-
Sweating
- Chills
- Headache
- Dizziness
- Muscular cramps (legs, stomach, etc.)
- Rapid pulse
- Exhaustion
Other countries have a widow spider called the redback spider. It’s a good idea to consider any shiny black spider with a red mark to be in the widow family. Another type of widow spider, the brown widow, generally has a weaker toxin and can be found worldwide.
Pathophysiology
A primary concern of the bite of a spider is the effect of its venom. A spider envenomation occurs whenever a spider injects venom into the skin. Not all spider bites involve injection of venom, and the amount of venom injected can vary based on the type of spider and the circumstances of the encounter.
The mechanical injury from a spider bite is not a serious concern for humans.
However, it is generally the toxicity of spider venom that poses the most risk to human beings; several spiders are known to have venom that can cause injury to humans in the amounts that a spider could inject when biting. While venoms are by definition toxic substances, most spiders do not have venom that is directly toxic (in the quantities delivered) to require medical attention and, of those that do, severity is typically mild.
spider venom
Spider venoms work on one of two fundamental principles; they are either neurotoxic (attacking the nervous system) or necrotic (attacking tissues surrounding the bite). In some cases, the venom affects vital organs and systems. The venoms of the widow spiders, Brazilian wandering spider and Australian funnel-web are neurotoxic. Heart muscle damage is an unusual complication of widow venom that may lead to death. Pulmonary edema, which is fluid accumulation in the lungs, is a feared and potentially serious but uncommon complication of funnel-web venom.Recluse and South African sand spider venoms are necrotic. Recluse venom may also cause severe hemolysis (destruction of red blood cells), though this is typically uncommon
spider venom
