What is the treatment for bot fly (myiasis) infections?

Botfly (Myiasis) Treatment

The primary treatment for botfly myiasis is complete surgical extraction of the intact larva, which should be performed promptly to prevent complications and does not require antibiotic therapy unless secondary bacterial infection is present. 1, 2

Treatment Approach

Furuncular Myiasis (Dermatobia hominis - Human Botfly)

Surgical excision is the treatment of choice for furuncular myiasis. 1 The goal is to remove the entire larva intact along with its surrounding burrow to prevent retention of larval fragments that can lead to inflammatory reactions. 1

Extraction Technique:

• Ensure complete removal of the intact larva to avoid leaving fragments in the wound that can cause persistent inflammation 1
• The larva is often found alive and moving upon removal 3
• Mechanical extraction should be performed carefully to maintain larval integrity 1

Post-Extraction Care:

• No antibiotic treatment is routinely needed after successful larval extraction 2
• Antibiotics should only be used if there is evidence of secondary bacterial infection 2
• The wound typically heals well after complete larval removal 2

Ophthalmomyiasis Externa (Oestrus ovis - Sheep Botfly)

For eye infestations, mechanical removal of larvae followed by topical antibiotics and corticosteroids is the standard treatment. 4

Management Protocol:

• Immediate mechanical removal of all visible larvae from the conjunctiva using slit-lamp examination 5, 4
• Apply antibiotic ointment or drops to prevent secondary infection 5, 4
• Add topical corticosteroid drops to reduce inflammation 4
• Resolution typically occurs within 1 week with appropriate treatment 5

Important Clinical Considerations

Diagnosis Requirements:

• Furuncular myiasis presents as painful, boil-like lesions in travelers returning from Central/South America or Mexico 1, 2
• Ophthalmomyiasis presents with severe local inflammation, foreign body sensation, periorbital edema, conjunctival erythema, and lacrimation 5
• Visual inspection and slit-lamp examination are essential for identifying larvae in ocular cases 5, 4

Common Pitfalls to Avoid:

• Do not damage the larva during extraction as retained fragments can cause ongoing inflammation 1
• Do not routinely prescribe antibiotics unless secondary bacterial infection is documented 2
• Recognize that vision may be reduced if the cornea is involved in ophthalmomyiasis 5

Geographic Context:

• Dermatobia hominis is indigenous to Mexico, Central and South America 1, 2
• Increasing cases in the United States are directly related to rising travel to endemic regions 1, 2
• Oestrus ovis has worldwide distribution but is particularly common in the Middle East and areas with sheep populations 5

Treatment Outcomes

Complete larval extraction results in resolution without need for prolonged therapy. 2 The prognosis is excellent when larvae are removed intact and promptly. 1, 4 For ophthalmomyiasis externa, inflammation resolves within approximately 1 week with mechanical removal and topical therapy. 5