By Anonymous -
Parasitic Insects
By Tyler Souza, Ali Bland, and Patrick Lunn
A variety of invertebrates feed on or in the human skin, including flies, fleas, bedbugs, lice, mites and ticks. The main goal of these parasites is to bite, feed quickly, and then leave without you ever knowing they were there. There are, of course, some exceptions to this including larvae of a few flies, scabies mites and hard ticks. All of these skin parasites leave tell tale signs, including itchy, round, red swellings. The majority of the bites last about two weeks if left alone, which is something almost impossible to do. If scratched, as everyone does, the itchiness and swellings could last up to two months. Not to mention that human fingernails are loaded with bacteria and scratching often leads to infections which can leave scarring.


Mosquito Bite


When most people think about human parasites, almost immediately the mosquito buzzes into their minds. It is the one we are all most familiar with. Those summer nights sitting around a campfire, or having a BBQ in your backyard, only to wake up the next morning covered in those itchy, red dots. Mosquitos, which belong to the family Culicidae, are very interesting in the fact that it is only the female that feeds on humans. Both males and females feed on honeydew, nectar, and plant juices. They use the sugar from these liquids for their daily life. But when it comes time for a female to reproduce, she must first find a victim. The female needs the blood in order to produce the eggs. In a laboratory study, a female mosquito experienced a weight gain of 140% after having a blood meal. The fact that female mosquitoes are blood-feeders means that they are very susceptible to carrying blood borne pathogens and various diseases that are extremely harmful to humans. Mosquitoes have been known to carry deadly diseases including yellow-fever, malaria, encephalitis, and the West Nile virus.


Another “interesting” insect, human parasite is the bot fly (Dermatobia hominis). Bot flies are “true-flies” found in the order Diptera. These flies are not the typical parasite. The larval stage is actually the only stage that affects humans. The adult stage actually never comes into contact with humans. You may be wondering how that works. Well, a female carrying mature eggs will find another blood-feeding arthropod, like a mosquito, and capture it. This is called phoresy. Then it will deposit its eggs on the arthropod. When the arthropod begins to feed, the eggs will detect a change in temperature (from the blood) and hatch onto the skin. There they move through the bite wound or available hair follicles. The larvae then burrow into the skin to the subcutaneous layer of the skin and will stay there for up to 12 weeks, growing and feeding on tissue. Then the fly emerges and goes into the soil to pupate. Pupation lasts for about three weeks. The now adults emerge and immediately look for a mate. They must do this quickly because adult botflies do not feed. So their energy/time is limited to reproduce. Once they mate, the cycle repeats itself.


       
The bot fly larva does not carry any disease. The only symptoms that the larva causes are pain around the infection site and swelling where the larva sits beneath the skin. The lesion does secrete pus as well. The most common treatment for the removal of the larvae is surgical procedure using a scalpel and local anesthesia. Another way, that does not require a doctor, is to put a piece of tape over the lesion. This covers the breathing holes (spiracles) of the bot fly larvae and forces it to come out of the skin. The larva can then be removed with forceps or tweezers. More than likely, the larva cannot be removed by popping it like a zit because the larva uses spines to anchor itself to the skin. When traveling to these areas it is recommended that travelers use insect repellent and wear protective clothing to avoid exposure to bot flies.


Some insects that parasitize humans are seen more as pests. For example bot fly larvae leave a small open wound and bedbugs leave tiny itchy bumps on their hosts. These insects do not dramatically damage the health of their host. This is more beneficial to them because then they are able to return to the same host over and over to gain nutrients. The real health issue from parasites comes when parasites carry diseases. Insects such as assassin bugs and mosquitoes are well known as carriers of disease. When it comes to more dangerous insects precautions should be taken to protect yourself from disease. Insect repellent, bed nets, and clothing that covers most of one’s skin is the easiest way to protect against these parasites.

References:

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