The AFU and Urban Legend Archive Animals maggots Select a topic - - - - - - - - Home Searches AFU FAQ - - - - - - - - AFU Animals Books Celebrities Classic Collegiate Death Disney Drugs Food GIF Language Legal Medical Misc Movies Politics Products Religion Science Sex Songs TV - - - - - - - - Other sites

Date: Wed, 31 Jul 1996 22:50:48 -0400
From: Judy Johnson <jjohnson@asrr.arsusda.gov>
Subject: Maggots

The following was in response to various ULish stories about maggots infesting people. (Its rather long so it may be unusable).

While I don't have access to Medline, I do have a medical entomology text book with a fairly good section on myiasis, defined as an infestation of the organs and tissues of man or animal by fly maggots that, at least for a period of time, feed upon the living, necrotic or dead tissues or upon the ingested food of the host (whew). The following is a summary.

Facultative myiasis refers to infestations where the maggot is normally free-living, but adapts itself to a parasitic existence under certain circumstances. Wounds may become invaded by carrion flies, and occasionally urinary tract infestations are recorded. Occasionally, maggots do make their way into the intestinal tract of humans and survive long enough to cause severe clinical symptoms. This is often referred to as pseudomyiasis, and is usually from the ingestion of food containing fly eggs, or from flies laying eggs near the victims anus (the back-door approach, hereby dubbed the Gere method). Flies involved include cheese skippers, Piophila casei, soldier flies Hermetia illucens, drone flies Eristallis tenax, and several muscids (house flies).

Obligatory myiasis involves flies that are dependent on an animal host. The screw-worm, Cochliomyia hominivorax, is one of the best known to Merkins, and is the most important producer of human and animal myiasis in the western hemisphere. The fly deposits eggs in wounds and the resulting maggots feed in the surrounding tissue. One particularly unpleasant example was recorded from Kansas in the 1880s. A man received a deposit of eggs in his nose while he slept. Apparently the flies were attracted to a nasal discharge. Despite attempts to remove the maggots (more than 250 in all) the patient died when his eustachian tubes were invaded. Other screw-worm type flies are Chrysomya and Wohlfahrtia (who says entomologists don't have a sense of humor) species.

Cattle grubs are maggots of heel or ox warble flies in the genus Hypoderma. Normally parasites of cattle and deer, they occasionally attack man and horses. These maggots burrow into the skin, migrating until they reach the back. There a pocket is formed about the maggot, in which it continues to develop, eventually emerging to pupate. Although humans are not the normal host, cases have been reported. Great pain and discomfort is associated with the migrating maggots, and local paralysis may occur from invasion of the spinal canal.

Sheep or horse head maggots are in the same family as cattle grubs, and reside in the nose of the host. Again, humans are not a normal host, but infestations do occur on occasion, often in the eye or nose. The maggots usually do not survive beyond the first larval instar. Cutaneous myiasis in humans can be caused by Wohlfartia species, resulting in boil-like lesions, usually in young children. Two flies that produce painful boil-like lesions in various parts of the body are Dermatobia hominis, common in Mexico, Central and South America, and Cordylobia anthropophaga. Both have a wide range of vertebrate hosts, including humans.

Enteric myiasis is infestation of the hosts intestinal system. True enteric myiasis does not occur in man, but does affect horses, donkeys, mules, and other animals. One well known example is the horse bot fly, Gasterophilus intestinalis.

According to my source, the use of sterile maggots in the disinfection of osteomyelitis and other wound infections is only of historical interest (although I thought it might be making a comeback, like leeches). It was introduced shortly after WWI by Baer, who noticed that maggot-infested wounds did not develop infections. At least one aboriginal tribe (the Ngemba of New South Wales) was known to use this technique.

[several astute AFUians responded with citations regarding recent use of maggots for debriding of wounds, so they have indeed made a comeback]

My source for all of the above (Herms's Medical Entomology; James and Harwood, 1969) may be a bit outdated, but I can't afford most of the newer textbooks that are available, and apparently neither can CSUFresno.

Judy "Wohlfartia...sounds like lupine flatulance" Johnson