Human botfly

📖Overview

Dermatobia hominis is a large oestrid fly native to tropical and subtropical regions of the Americas. Adults are short-lived and do not feed; instead females attach eggs to blood-feeding insects (usually mosquitoes or flies). When the carrier lands on a warm-blooded host, the eggs hatch and the larvae burrow into the skin, developing under the host's skin for several weeks.

Infestations produce single or multiple raised, often painful swellings with a central breathing pore. Larvae feed on host tissue and fluids, then drop to the ground to pupate. Human cases are most common in rural and forest-edge areas where people are exposed to the carrier insects; the species is an important veterinary pest of livestock in its range.

🔍How to identify a human botfly

Adult Dermatobia hominis are robust flies about 12-20 mm long with a stout, hairy body resembling other botflies. They have a grayish thorax, a shiny metallic blue abdomen, yellowish-orange legs and face, and short antennae. The larvae (mature third instars) are cream to yellowish, about 15-25 mm long, conical with rows of backward-pointing spines that anchor them in host tissue, and a posterior breathing cone that protrudes at the skin pore.

1. Look for a raised, boil-like lesion, often itchy or painful, with a central breathing pore and intermittent movement or a sensation of movement.
2. A small, firm round swelling that occasionally discharges serous fluid or blood is typical; larval breathing hole often visible.
3. In endemic regions, recent outdoor exposure in forest or pasture makes D. hominis likely when single lesions occur; multiple lesions suggest multiple transfers.
4. If a larva is extracted, the conical, spined third-instar (cream to yellow, 15-25 mm) confirms botfly myiasis.

Lookalikes

↻Life cycle

1. 🥚

   Egg

   Female captures or attaches eggs to a blood-feeding insect (e.g., mosquito or fly). Eggs are transferred to a mammal when the carrier feeds; warmth triggers hatching.

2. 🐛

   Larva

   Larvae burrow into the skin and develop as subcutaneous parasites (furuncular myiasis) for about 5-12 weeks, passing through three instars while feeding on host tissue and fluids.

3. 🫛

   Pupa

   Mature larva exits the host, drops to the ground and pupates in soil or leaf litter for several weeks before emerging as an adult fly.

4. 🪰

   Adult

   Adults are short-lived, mate, and females capture or glue eggs to carrier insects to continue the cycle.

🍃Diet and predators

🌱Effect on plants and gardens

Does not feed on or damage plants; impact is on mammal hosts rather than vegetation.

How to get rid of human botflies

Protect people and animals from carrier insects (mosquito nets, repellents, protective clothing). For livestock use recommended insecticides and ear tags or pour-on products as advised by a veterinarian. Inspect animals regularly and have larvae removed by a vet; properly dispose of extracted larvae and treat secondary infections. Eliminating breeding sites for carrier mosquitoes may reduce transmission locally.

📍Where and when to find it

Adults near forest edges, pastures and areas with mosquitoes. Larval lesions are found on exposed skin of humans and mammals, commonly on arms, legs, torso and scalp.

✨Fun facts

• Females use a 'phoretic' strategy: they attach eggs to other blood-feeding insects which unknowingly deliver the eggs to a mammal host.
• The breathing pore is an adaptation that lets the larva remain under the skin while still getting oxygen.
• Despite the alarming appearance, infestations are usually localized and can be treated safely by health professionals.

?Frequently asked questions

📷Photos of the human botfly