Vets warned ahead of expected US screwworm outbreak

United States veterinarians have been urged to prepare themselves for being “on the frontlines” of detecting and combating a potential outbreak of the New World screwworm (NWS) fly.

The parasitic blowfly – whose flesh-eating larvae feed on the live tissue of warm-blooded animals, which can be fatal if left untreated – was officially eradicated from the U.S. in 1966.

However, a surge in cases throughout Central America and Mexico – including a case in September less than 70 miles from the U.S. border – has officials preparing for its return.

Vet Will McCauley, director of industry and government relations at Medgene, who also sits on the Texas Veterinary Medical Association’s board of directors, has urged colleagues to ensure they and their clients are ready for screwworm.

Back with a vengeance’

He said: “It’s coming back with a vengeance, so veterinarians need to be very active and very engaged in educating their clients and the public about this threat and then getting ready to really be on the frontlines of the monitoring efforts, the surveillance efforts and the response efforts once the screwworm gets here.”

Dr McCauley added it’s “very important to get up to speed on this parasite, know how it spreads, how we will counteract it,” and he called on vets to take advantage of educational opportunities offered by the USDA and other groups.

Vet and cattle rancher Monica Janacek issued a similar message. She said: “As boots-on-the-ground veterinarians, we must educate our clients on this threat.

“As local animal health experts, we must stay up to date on what to do at the point of care and the appropriate agencies to reach out to so that all efforts are coordinated properly.”

“There is no need for panic,” she added, pointing to a successfully eradicated 2016 outbreak in the Florida Keys.

‘A danger to all’

Dr Janacek also offered a tip for identifying NWS having encountered it while travelling in South America: “The smell of an infested wound is unlike anything you may encounter as a veterinarian… You typically can smell the NWS infested wound before you see it, and the characteristic smell is almost pathognomonic for diagnosis.”

Christine Prior, owner and vet at Town and Country Animal Hospital in Henderson, Texas, said that because NWS can affect pets, livestock and wildlife alike, “all veterinarians need to be on the lookout for the possibilities of screwworm presence.”

She continued: “If there is one screwworm found in an area there are more that are causing problems that just haven’t been found. Screwworms pose a danger to all living creatures, including humans.”

Due to a lack of animal drugs approved by the U.S. Food and Drug Administration for treating NWS infestations, its Center for Veterinary Medicine maintains a list of drugs that may be helpful for extra-label use.

‘No silver bullet’

Dectomax-CA1, which prevents and treats infestation in cattle for 21 days, was recently granted conditional approval.

Dr McCauley said the deployment of sterile male flies offers a long-term method of driving back outbreaks, but “we’re looking at a fairly long runway for that.”

An existing facility in Panama can breed 100 million insects per week, but Dr McCauley said around six times that production capacity is needed, to which end facilities in Mexico and Texas are being built.

In the meantime, he said vaccines, parasiticides, traps and repellents are all being explored.

“There’s no silver bullet,” he added. “There’s not going to be one solution, it’s going to be a collection of counter measures.”