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# Dermatobia hominis

- Parasite
- For completeness

Fly larvae living in skin or wounds. The botfly sends its eggs on a mosquito, and its larva forms a boil-like lump with a breathing hole.

Updated 2026-11-01

Also called: human botfly, torsalo, New World screwworm (Cochliomyia hominivorax)

## Key points

- Dermatobia uses mosquitoes to carry its eggs (phoresis).
- Boil-like nodule with a central breathing pore.
- Cochliomyia hominivorax: wound myiasis with tissue destruction.
- Treatment: remove the whole larva.
- Risk in uncovered wounds of vulnerable people.

## At a glance

**Shape**
Bottle- or barrel-shaped larva with rows of spines

**Family**
Oestridae (Dermatobia); Calliphoridae (Cochliomyia)

**Type**
Insect: fly larva (Diptera)

**Size**
Mature larva 1–2 cm

## Morphology

- Larva with spines that anchor it in tissue and posterior spiracles for breathing.
- Identified by its spiracles, mouthparts and cuticular spines.
- Lesion with a central opening through which the larva breathes.

## Transmission

- Dermatobia: the fly glues its eggs onto a mosquito or other blood-feeding insect (phoresis), which carries them to the skin.
- Cochliomyia hominivorax: the fly lays eggs directly in wounds or on nasal and oral mucosa.
- Risk factors: uncovered wounds, chronic ulcers, homelessness or reduced mobility.

**Reservoir:** Cattle, dogs and other mammals (animal myiasis)

**Vector:** For Dermatobia, mosquitoes and other blood-feeding insects carry the eggs.

### Isolation precautions

What the care team adds to standard precautions.

- Standard

## Life cycle

- The adult Dermatobia fly catches a mosquito or other blood-feeding insect and glues its eggs to it.
- When that insect bites a person or animal, the larvae emerge and enter the skin.
- The larva lives 5–10 weeks in a cavity under the skin and breathes through a central hole.
- When mature, it leaves the skin, drops to the ground and pupates; the adult emerges in a month.
- Cochliomyia hominivorax lays its eggs in wounds or mucosa; its larvae eat living tissue.

## Virulence factors

- Dermatobia: painful boil-like nodule with discharge and a feeling of movement.
- Cochliomyia: extensive destruction of living tissue in wounds, sometimes fatal.
- Bacterial superinfection of the lesion.
- Cavity myiasis (nose, orbit, ear) with a risk of serious damage.

## Diseases it causes

- Cutaneous, wound or cavity myiasis [Tungiasis and furuncular myiasis →](https://durgical.com/en/conditions/tungiasis-and-furuncular-myiasis/)
- Screwworm myiasis (Cochliomyia hominivorax) with tissue destruction

## Clinical picture

- Inflamed nodule with a central pore that drains fluid and bubbles.
- Stabbing pain and a feeling that something is moving.
- Wound or ulcer with visible larvae and a foul smell.

## Diagnosis

- Finding larvae in tissue.
- Identification of genus or species by morphology (spiracles, mouthparts, spines).
- Ultrasound or dermoscopy can show the larva.
- History of travel or rural living.

## Treatment

Complete removal of the larvae, often by minor surgery, and daily wound cleaning; antibiotics for superinfection. There is no routine antiparasitic drug.

Drug class only; doses and regimens are set by the clinician from the current guideline.

## Prevention

- Repellents and loose long-sleeved clothing.
- Cover open wounds and care for chronic ulcers.
- Mosquito and fly control.
- In livestock, the sterile male technique against screwworm.

## In Colombia

The botfly ('nuche', Dermatobia hominis) is common in warm rural cattle-raising areas, and the screwworm (Cochliomyia hominivorax) causes wound myiasis in cattle and in people with neglected ulcers or wounds.

## Memory aid

The botfly travels as a passenger: it never bites, it ships its eggs on a mosquito, and the larva breathes through a pinhole.

## Test yourself

Think of the answer, then tap the question to see it.

## How do Dermatobia hominis eggs reach human skin?

Glued to a mosquito or other blood-feeding insect captured by the fly; when it bites, the larvae emerge and penetrate the skin.

## Which sign marks a botfly lesion?

A boil-like nodule with a central opening through which the larva breathes.

## Which fly causes destructive wound myiasis in the Americas?

Cochliomyia hominivorax, the New World screwworm.

## What is the main treatment of myiasis?

Complete removal of the larvae and wound cleaning.

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## Related

- [Tunga penetrans](https://durgical.com/en/microbiology/tunga-penetrans/)
- [Sarcoptes scabiei](https://durgical.com/en/microbiology/sarcoptes-scabiei/)

## Related conditions

- [Tungiasis and furuncular myiasis](https://durgical.com/en/conditions/tungiasis-and-furuncular-myiasis/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Ectoparasites](https://durgical.com/en/microbiology/groups/ectoparasites/)

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: [CDC - DPDx - Myiasis](https://www.cdc.gov/dpdx/myiasis/index.html) (CDC, 2024); [About Myiasis | Myiasis | CDC](https://www.cdc.gov/myiasis/about/index.html) (CDC, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/dermatobia-hominis/