The United States Department of Agriculture has deployed a novel biological control strategy to combat an outbreak of New World screwworm, a flesh-eating parasitic fly, in southern Florida. The operation involves releasing sterile male screwworm flies to disrupt the breeding cycle, alongside trained detection dogs to locate infested animals. British veterinary experts from the Animal and Plant Health Agency have been consulted to provide technical advice on containment and eradication protocols.
The outbreak, first detected in July 2023 in the Florida Keys, marks the first recurrence of screwworm in the United States since the pest was eradicated in 1966. The parasite, Cochliomyia hominivorax, lays eggs in open wounds of warm-blooded animals. The larvae feed on living tissue, causing severe injury and often death if untreated. The current outbreak has primarily affected the Key deer population, an endangered species, but poses a risk to livestock and domestic pets.
The sterile insect technique is a proven method that involves releasing male flies irradiated to render them infertile. They mate with wild females, which then produce no offspring, gradually reducing the population. The USDA is producing sterile flies at a dedicated facility in Mexico and airlifting them to Florida for release. Detection dogs trained to identify screwworm scent are being used to inspect deer and other animals for infestations, allowing early treatment and quarantine.
British involvement stems from the UK’s experience with similar control programmes and its status as a major exporter of veterinary expertise. The Animal and Plant Health Agency has provided specialist training for dog handlers and guidance on surveillance protocols, reflecting close transatlantic cooperation on biosecurity. The consultation underscores the global dimension of the outbreak, given the screwworm’s historical spread from the Americas to other regions via animal movements.
Officials emphasise that the risk to humans is low, though cases of myiasis have been reported in rare instances. The USDA is maintaining a containment zone in the Keys and restricting movement of animals from the area. The success of the sterile insect technique will depend on sustained releases and public cooperation in reporting suspicious wounds on animals. The operation is expected to continue for several months, with full eradication anticipated by late 2024.
