Bot Flies In Belize: What You Need To Know

Bot flies are a common problem in Belize, a small Central American country. The female bot fly deposits mature eggs on the body of another insect, such as a mosquito or a fly. When the mosquito or fly bites a person, the mature egg is injected into the person's skin, where it hatches into a larva. The larva then burrows into the skin, creating a lesion with a hole in the centre to breathe through. While bot flies are rarely seen in the U.S., they are a common skin problem in Central America, and can be removed through various home remedies or medical procedures.

Bot fly prevention methods

The bot fly is a type of parasitic fly known for its disturbing appearance during its larval stage, when it burrows and feeds on mammalian flesh. The human bot fly, or Dermatobia hominis, is native to the tropics of Central America and South America, including Belize.

To prevent bot fly bites, it is recommended to:

• Wear protective clothing, such as long sleeves and pants, to minimise exposed skin.
• Apply insect repellent to deter not only flies but also mosquitoes, wasps, and ticks that can carry fly eggs.
• Sleep under mosquito nets.
• Close all windows and doors after dark.
• Use nets on windows.
• Avoid having food or liquids accumulating indoors, as this can attract insects.
• Iron all clothing before dressing, especially if it has been dried outside, as bot fly eggs may stick to the fabric.

It is also recommended to take precautions when spending time in the jungle, as this seems to be where most bot fly bites occur. Regular bathing and shampooing may also help to prevent bot fly eggs from developing.

Bot fly removal methods

Bot flies are a type of fly that can be a nuisance for both humans and animals. The female bot fly lays eggs on a mosquito, and when the mosquito bites a person, the eggs enter the wound. The egg then develops into a larva, which grows and eventually drops out. The larva has backward-directed spines that prevent the host from removing it. While bot fly infestations are not common in Belize, it is important to know how to remove them safely if needed. Here are some methods that can be used to remove bot flies:

Shaving and Duct Tape

Shaving the affected area, applying duct tape, and waiting 24 hours before removing the tape is one method suggested by a lodge owner in Belize. This method creates a seal over the bot fly, and it can then be removed by popping it out like a pimple.

Ivermectin

Ivermectin is an animal deworming medicine that can be prescribed by a doctor to treat bot fly infestations. This medication helps to kill the larva and stop its development.

Regular Bathing and Shampooing

Maintaining good hygiene by bathing daily and shampooing regularly can help prevent bot fly eggs from developing. Even in jungle settings without running water, daily bathing with soap and shampoo can reduce the risk of bot fly infestations.

Covering Exposed Skin

Wearing a hat and covering exposed body parts such as the neck, arms, and ankles can help reduce the risk of bot fly bites. This is especially important in areas where bot flies are prevalent, as they can bite without being felt.

It is important to note that bot fly removal should be done carefully to ensure the entire larva is removed. In some cases, medical attention may be required, especially if the bot fly is in a sensitive area or is causing severe symptoms.

Bot fly lifecycle

The lifecycle of a bot fly varies depending on the species, but all species are internal parasites of mammals. Some species grow in the flesh of their hosts, while others grow within the host's alimentary tracts.

The female bot fly can deposit between 150 and 1,000 eggs on a host, or sometimes use an intermediate vector such as a mosquito. After mating, the female captures the insect by holding onto its wings with her legs. She then attaches her eggs to the insect's abdomen, where they incubate. The female does this repeatedly to distribute the 100 to 400 eggs she produces during her short adult stage of life, which lasts only 8-9 days.

The eggs hatch into maggots within 7 to 10 days of being laid. The larvae are stimulated to emerge by the host licking or biting the attached, fully developed eggs. The larvae either crawl to the host's mouth or are ingested and subsequently bury themselves in the tongue, gums, or lining of the mouth. After wandering in the mucosa of the mouth, the larvae molt to the second stage and move into the stomach. The second and third-stage larvae attach to the lining of the stomach and remain immobile for the following 9 to 12 months.

The third-instar larvae are relatively large, between 1/2 to 3/4 inch (1.27 to 1.91 cm) long. They have rounded bodies, narrow, hooked mouthparts, and spines. The hooked mouthparts enable the larvae to securely attach to the lining of the stomach and intestinal tract. The larvae use their flat mandibles to abrade the tissue of the stomach.

After the third-instar larvae have matured, they detach from the gastrointestinal tract and pass from the host's body in the feces. The larvae then burrow into the soil or dried manure and pupate, remaining in this stage for the next one to two months. After a three- to 10-week period, the adult bot fly emerges and quickly finds a mate. The female begins host-seeking and oviposits, and the cycle repeats.

Bot fly appearance

The adult human bot fly, also known as the torsalo, is a large, densely-haired fly native to Central and South America. It resembles a bumblebee in appearance, with a yellow face, a metallic blue abdomen, orange legs, and hairs covering each body segment. The adult bot fly is 12 to 18mm long and exhibits a wide array of colours.

The female bot fly attaches her eggs to mosquitoes, stable flies, ticks, and other insects that carry the eggs to the actual host. The eggs are creamy-coloured and oval-shaped. The warmth of the host animal induces the eggs to hatch, and the larvae penetrate the skin. The larvae, or white maggots, go through three stages of development once inside the mammalian host. Each stage, or instar, has a distinctive shape: the first is worm-like with a bulbous end, the second has a bottle-neck shape, and the third is cylinder-shaped. Each instar has backward-projecting spines that encircle the thorax, anchoring the larvae in the wound.

The larvae breathe through two posterior spiracles that lie flush with the skin of the host. After approximately thirty days, the third instar larvae crawl out of the host and pupate in the soil. After two to three weeks, the adult bot flies emerge from the pupal cases.

The human bot fly is not known to transmit disease-causing pathogens, but the larvae infest the skin of mammals and live out the larval stage in the subcutaneous layer, causing painful, pus-secreting pustules.

Bot fly health risks

Bot flies are a type of fly that belongs to the Oestridae family. They are usually found in humid, mountainous areas of tropical countries, such as Brazil and Belize. The female botfly lays its eggs on another insect, typically a mosquito, which then transfers the eggs to a human host when it bites them. The larvae then enter the host's skin and feed on their soft tissue for 5 to 10 weeks, causing a condition known as myiasis.

Symptoms of Myiasis

• Slow-growing nodules with swelling, usually noticed about a week after the initial insect bite.
• Skin lesions that are pruritic and mildly painful, with a sensation of movement under the skin.
• Formation of wounds on the skin with redness and slight swelling.
• Release of a yellowish or bloody fluid from the sores.
• Pain or intense itching at the wound site.

Health Risks

While myiasis is typically a self-limiting condition and the larvae will expel themselves after 6 weeks, there are several health risks associated with bot fly infestations:

• Secondary infections: Removing the larvae in pieces, especially using at-home methods like tweezers, can lead to secondary infections.
• Lethal brain infestations: Pediatric patients with scalp involvement can lead to potentially lethal brain infestations.
• Eye infections: There have been reports of bot fly larvae moving through the fontanelles of infants and causing eye infections.
• Misdiagnosis: Due to their rare occurrence, bot fly infestations are often misdiagnosed as cellulitis, leishmaniasis, furunculosis, staphylococcal boils, insect bites, or sebaceous cysts.

Prevention and Treatment

To prevent bot fly infestations, it is recommended to wear protective clothing, use insect repellent, and sleep under mosquito nets when travelling to endemic regions.

If you suspect a bot fly infestation, it is important to consult a medical professional for proper diagnosis and treatment. Treatment options may include surgical management, non-surgical methods such as suffocating the larva, or expectant management if the patient does not desire removal.

Frequently asked questions