Myiasis (Fly Maggot Infestation): Types, Symptoms, and Treatment

Myiasis (sometimes misspelled "tachiasis") is the infestation of living tissue by fly larvae (maggots). It occurs when certain fly species deposit eggs on or near wounds, body orifices, or intact skin. The hatched larvae feed on host tissue, causing significant morbidity.

Clinical Classification

• Cutaneous myiasis (most common):
  • Furuncular: Single larva in a boil-like lesion (e.g., Dermatobia hominis botfly, Cordylobia tumbu fly). Central punctum for breathing.
  • Migratory/creeping: Larvae burrow through subcutaneous tissue (e.g., Gasterophilus, Hypoderma).
  • Wound myiasis: Eggs laid on necrotic tissue (e.g., Lucilia, Chrysomya blowflies).
• Cavitary myiasis: Nasal, aural, ocular, oral, vaginal, or urinary tract infestation.
• Systemic/visceral myiasis (rare, severe): Larvae invade internal organs.

Geographic and Risk Factors

Endemic in tropical/subtropical regions (Africa, South America, Caribbean). Risk factors: poor wound care, immunosuppression, malnutrition, alcoholism, homelessness, travel to endemic areas.

Clinical Features

• Painful, pruritic nodules with central pore (furuncular)
• Serosanguinous discharge, foul odor (wound myiasis)
• Sensation of movement under skin
• Cavitary: nasal obstruction, epistaxis, otalgia, visual disturbance

Treatment

1. Larva removal: Occlusion (petroleum jelly, adhesive tape) to force larval emergence, then manual extraction with forceps. Surgical incision for deep/embedded larvae.
2. Wound care: Debridement, irrigation, topical/systemic antibiotics for secondary infection.
3. Ivermectin: Oral (200 mcg/kg) for multiple or inaccessible lesions.
4. Prevention: Wound coverage, insect repellents, screened housing, ironing clothes (kills eggs).

Urgent medical attention is needed for cavitary myiasis (risk of intracranial/ocular invasion) or extensive infestation.