The United States has deployed a combined force of sniffer dogs and sterilised flies in the Florida Keys to combat an outbreak of New World screwworm, a parasitic fly whose larvae infest the flesh of living mammals. The infestation, confirmed in Key deer and a single domestic dog, marks the first appearance of the pest in the continental United States in over 30 years. Teams from the UK’s Animal and Plant Health Agency are on standby to assist if the outbreak spreads.
The screwworm, Cochliomyia hominivorax, is distinct from common blowflies. It lays eggs in open wounds, producing larvae that feed on living tissue, often causing fatal infections. The current strategy involves releasing laboratory-sterilised male flies to disrupt breeding, mirroring a technique pioneered in the 1950s that eradicated the pest from North and Central America. Beagles trained to detect the distinctive odour of infested animals are also searching for additional cases.
The Florida Department of Agriculture has established a quarantine zone in the Keys, restricting the movement of livestock and pets. Officials have urged residents and veterinarians to inspect animals for suspicious wounds. The UK’s National Reference Laboratory for arthropod-borne diseases has prepared diagnostic support and risk assessments at the request of the World Organisation for Animal Health.
Dr Richard Sands, a veterinary entomologist at the University of Reading, described the situation as a “taut strategic moment”. “The sterile insect technique is elegant but requires discipline,” he said. “If the outbreak breaches Florida, it could threaten the UK’s livestock sector, particularly through imported animals.” The UK ceased sustained screwworm surveillance in 2015, but experts note that the species could establish in Southern Europe and the Mediterranean given warmer conditions.
The USDA emphasised that human risk is low, though cases have been recorded in rural areas. The Puerto Rican outbreak in 2010 cost an estimated $1.2 billion in livestock losses. A senior British government source confirmed that contractual agreements with US laboratories allow for rapid sharing of sterilised flies if needed.
The intervention represents a classic exercise of soft power: the UK’s readiness to deploy expertise without fanfare reflects its broader commitment to biological security. For now, the scent hounds and sterile flies remain the front line of defence.
