The United States Department of Agriculture has deployed a novel biosecurity measure in response to an outbreak of the New World screwworm, a flesh-eating parasite, in the Florida Keys. The strategy, which involves the release of sterile male flies and the use of sniffer dogs, draws on lessons from Britain’s own experience with similar threats.
The New World screwworm, Cochliomyia hominivorax, is a devastating pest that infests warm-blooded animals, including humans. The larvae feed on living tissue, causing severe wounds and often death if untreated. The current outbreak, detected in Key deer and domestic pets, has raised fears of a wider spread across the southern United States.
The USDA’s response centres on the Sterile Insect Technique, a method pioneered in the 1950s. Millions of sterilised male flies are released from aircraft, mating with wild females and producing no offspring. This effectively breaks the reproductive cycle. The technique was used successfully to eradicate the screwworm from the United States in the 1960s and later from Libya and parts of Central America.
Complementing the aerial drops are canine detection teams. Dogs trained to sniff out screwworm-infested wounds are deployed to identify and isolate infected animals. The dogs, often beagles or Labrador retrievers, can screen large numbers of livestock and wildlife quickly and with high accuracy. Their use is a direct adaptation of biosecurity protocols developed in the United Kingdom during the foot-and-mouth disease outbreaks of 2001 and 2007.
The British experience demonstrated that rapid detection and quarantine are critical to containing zoonotic and epizootic diseases. The UK’s Animal and Plant Health Agency has since refined techniques involving sniffer dogs for a range of pests and pathogens. These methods are now being exported to other nations facing similar crises.
The USDA emphasises that the screwworm threat is not limited to the Americas. Climate change and increased global trade have expanded the potential range of the parasite. In 2018, the screwworm was detected in the Caribbean, and in 2019, an outbreak in the Canary Islands required Spain to deploy sterile flies and quarantine measures. The UK has maintained a contingency plan for screwworm introduction since a scare in 2016 when a British tourist returned from Peru with an infestation.
The current US operation is a test case for international coordination. The sterile flies are produced at a facility in Panama, a nation that has combated the screwworm for decades. The dogs are trained in Texas and Florida, drawing on British curriculum materials. The logistical challenge is considerable: the Florida Keys span over 1,700 islands, and the Key deer population is genetically vulnerable.
Critics question the long-term sustainability of the sterile insect technique, noting its cost and the need for continuous releases. However, the USDA argues that historical precedent supports its efficacy. The dogs offer a low-tech, high-impact supplement, especially in densely vegetated or urban areas where aerial spraying is impractical.
The broader lesson for the UK is that biosecurity is a networked enterprise. British expertise in detection and quarantine is being applied beyond Europe. The Government’s 2022 Biosecurity Strategy, which emphasised collaboration with international partners, is being operationalised through such exchanges.
As the Florida outbreak continues, the USDA expects to release up to 7 billion sterile flies per week. The dogs will work alongside ground teams for the next six months. The outcome will inform global protocols for managing emerging threats from parasitic arthropods.
The writer is Senior International Correspondent for this newspaper. The views expressed are her own.
