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Insect Bites (cont.)

Causes of Insect Bites

Most insects do not usually attack humans unless they are provoked. Many bites and stings are defensive. Insects sting to protect their hives or nests or when incidentally touched or disturbed (so hives and nests should not be disturbed or approached).

A sting or bite injects venom composed of proteins and other substances that may trigger an allergic reaction in the victim. The sting also causes redness and swelling at the site of the sting.

Bees, wasps, hornets, yellow jackets, and fire ants are members of the Hymenoptera family. Bites or stings from these species may cause serious reactions in people who are allergic to them. Death from bee stings is 3 to 4 times more common than death from snake bites. Bees, wasps, and fire ants differ in how they inflict injury.

  • When a bee stings, it loses the entire injection apparatus (stinger) and actually dies in the process.
  • A wasp can inflict multiple stings because it does not lose its injection apparatus after it stings.
  • Fire ants inject their venom by using their mandibles (the biting parts of their jaw) and rotating their bodies. They may inject venom many times.
  • Puss caterpillars (Megalopyge opercularis or asp) have hollow "hairs" or spines (setae) that break when touched and toxin is injected into the skin.
  • In contrast, bites from mosquitoes are not defensive; mosquitoes are looking to get blood for a meal.
    • Typically, most mosquitoes do not cause significant illnesses or allergic reactions unless they convey "vectors," or pathogenic microorganisms that actually live within the mosquitoes. For instance: 
      • malaria is caused by an organism that spends part of its life cycle in a particular species of mosquitoes.
      • West Nile virus is another disease spread by a mosquito. Various mosquitoes spread other viral diseases such as
      • equine encephalitis;
      • Zika virus (suspected of causing microcephaly);
      • dengue; and
      • yellow fever to humans and other animals.

Other types of insects or bugs that bite for a blood meal and diseases that are possibly transmitted are as follows:

  • Lice bites can transmit epidemic relapsing fever, caused by spirochetes (bacteria).
  • Leishmaniasis, caused by the protozoan Leishmania, is carried by a sand fly bite.
  • Sleeping sickness in humans and a group of cattle diseases that are widespread in Africa, and known as, are caused by protozoan trypanosomes transmitted by the bites of tsetse flies.
  • Bacteria-caused diseases tularemia can be spread by deer fly bites, the bubonic plague by fleas, and the epidemic typhus rickettsia by lice.
  • Ticks (arachnids) can transmit Lyme disease and several other illnesses through their bites; ticks bite so they can obtain a blood meal.
  • Other arachnids (bugs) such as chiggers, bedbugs, and mites typically cause self-limited localized itchiness and occasional swelling.
  • Serious bites from spiders (arachnids), which are not insects, can be from the black widow or brown recluse spiders; the spiders bite usually as a defense mechanism.

Other insects and bugs can transmit diseases by simply transferring pathogens like Salmonella spp by contact. For example, in unsanitary conditions, the common housefly can play an incidental role in the spread of human intestinal infections (such as typhoid, bacillary and amebic dysentery) by contamination of human food as it lands and "walks" over foods after previously "walking" on contaminated items like feces.

Medically Reviewed by a Doctor on 6/1/2016

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