“The human botfly (Dermatobia hominis) is a species of fly from the family Oestridae that is well-known for its love of human flesh, and its “interesting” means of parasitizing humans —bot fly larvae develop within the subcutaneous layers of human skin. And, yes, those who are unfortunate enough to become temporary hosts to the larvae can expect to feel them moving around underneath their skin”.
Bot flies are known by several names, human bot fly, warble flies, heel flies, gadflies, torsalo (Central America), moyocuil (Mexico), berne (Brasil), mucha (Columbia), mirunta (Peru), and ura (Agentina, Paraguay, and Uruguay. Their larvae are internal parasites of mammals, some species growing in the host’s flesh and others within the gut. The word “bot” is in reference to “a maggot”.
Lifestyle
Adult bot flies do not feed, and live only a short time. Botflies are obligate parasites of vertebrates. Their larvae must undergo development inside a warm-blooded host.
The distribution of Dermatobia hominis bot fly includes Mexico, Costa Rica, Central and South America. In the U.S., cases usually occur in travelers who have visited endemic areas.
Appearance
Bot flies (Order Diptera, Family Cuterebridae) are stout bodied, large, hairy flies that resemble bumblebees.
The adult bot fly is 12 to 18 mm long with a wide array of colors and their face is yellow with a metallic blue abdomen and orange legs and each body segment is covered with hairs which give the fly a bumblebee appearance.
How they live?
“The botfly egg is deposited by a mosquito or sometimes by another insect. The larva grows in the host’s body until it is fairly large. The botfly larva can easily be killed by taking away its air supply — by putting vaseline or similar on the skin where the lump is, but then you still have to extract the larva. Adult botflies have nonfunctional mouthparts and do not feed. Larvae of this species parasitize wild and domestic rabbits. Females deposit their eggs in or near the entrance of their host’s burrow. Bot fly larvae penetrate their host through the skin or natural body openings after hatching. The larvae form a tumor (called a warble) in the subdermal zones of their host and remain at this location until larval development is complete. Larval development varies among species, ranging from 20 to 60 days. Before pupating, the larvae leave the host’s skin and drop to the soil.
Generally, the host is not severely damaged by this parasite. The majority of the injury occurs when the larvae exit the host through the warble. Parasitism by the botfly does not affect the edibility of the rabbit (assuming you eat rabbit), generally the area adjacent to the warble is trimmed away, and the rest of the rabbit is suitable to eat,” explains Ambergriscaye.com.
Cattle and dogs are the most common hosts for the human bot fly. They can also be found in many warm-blooded animals that include sheep, rabbits, pigs, monkeys, humans, dogs, cats, cattle and buffalo.
Do they host in humans?
The bot fly insect lays its eggs on a mosquito and the eggs hatch when the mosquito feeds on a host. This insect also can humans hatch in you. While the maggot feeds on you as the host, it has to have a hole in the skin so it can continue to breath. The process takes approximately 6 weeks to complete development on its host.
According to IFAS University of Florida, cases of human Dermatobia hominis myiasis reported from non-indigenous people are diagnosed when travelers bring the parasite back with them from Central and South America. Haruki et al. (2005) reported 33 cases of Dermatobia hominis in Japan from 1974-2005 as a result of overseas travel to Central and South America. One third of the reported cases occurred during the last six years of the study. Six different studies have documented seven reported cases of Dermatobia hominis myiasis in the United States since 1999 (Lawson et al. 2005, Liebert et al. 2004, Maier et al. 2004, Marty et al. 2005, Millikan 1999, Sampson et al. 2002). All the patients with confirmed Dermatobia hominismyiasis had recently been to Central or South America”.
Symptoms and Treatment
“Dermatobia hominis larvae cause a raised lesion in the skin that becomes hard and sometimes painful. In some cases the patients can feel the larvae moving when they shower or cover the wound (Haruki et al. 2005, Sampson et al. 2001). The host reacts with elevated white cell counts and a high amount of macrophages can be found around the wound. For this reason, the lesion often secretes pus. There are several treatment options for treatment of Dermatobia hominis myiasis. The most conventional way of removing the larvae is with a simple surgical procedure that includes local anesthesia. Using a scalpel to cut a slit to enlarge the wound, the larvae can be taken out.
Dermatobia hominis survives in its host by breathing through spiracles that are flush with the skin. In order to coax the larva out, the spiracles need to be covered. They can be covered with bacon, petroleum jelly, beeswax, or any other thick substance that prevents the larvae from breathing. The larvae will come up out of the lesion to breathe allowing it to be removed with forceps.
In some cases the larva maybe popped out by applying pressure around the wound. Tamir et al. (2003b) cited a technique that used two wooden spatulas to apply pressure to pop the larva out. There may be some difficulty with this method due to the spines that anchor the larvae in the wound.
Several authors (Diaz et al. 2006, Kahn 1999, Safdar et al. 2003, Tamir et al. 2003b) have cited the use of lidocaine injections underneath the cyst. This creates pressure that pushes the larva out. After any of these procedures, antibiotics are given to prevent infection. The wound should heal in one to two weeks with little or no scarring,” reports IFAS University of Florida.
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