screwworm

Screwworm refers to the larval stage of certain flesh flies that cause myiasis in warm-blooded animals, including humans. The term is commonly used for two species: the New World screwworm fly, Cochliomyia hominivorax, and the Old World screwworm fly, Chrysomya bezziana. The larvae invade living tissue, creating deep, expanding wounds that can destroy tissue if untreated.

Life cycle: Eggs are laid on exposed wounds or natural openings. Hatching occurs within 24 to 48 hours. The larvae feed on living tissue for about five to seven days, causing tissue destruction and secondary infection. Mature larvae drop to the soil and pupate; adults emerge after a period dependent on temperature. Females may lay hundreds of eggs in batches. The cycle can continue through multiple generations in suitable climates.

Distribution and impact: Screwworms have been a major veterinary pest for cattle and other livestock in many regions. They can also infest humans who have wounds or natural openings. The New World screwworm was largely eradicated from North America and much of Central and South America through sterile insect technique programs, with ongoing surveillance to prevent reintroduction. The Old World screwworm remains a concern in parts of Africa, Asia, the Middle East, and Australia where it occurs or has occurred. Economic losses arise from decreased productivity, treatment costs, and damage to hides and meat.

Diagnosis and control: Diagnosis is based on observation of larvae in wounds or identification of adult flies. Treatment for animals includes removal of larvae, wound debridement, topical or injectable antiparasitics, and antibiotics to prevent secondary infection. Prevention relies on proper wound care, sanitation, fly control measures, and, in some regions, release of sterile flies to disrupt reproduction.