New World screwworm confirmed in Florida

While not found in livestock yet, additional surveillance efforts underway as pest is being eradicated in affected zone.

The U.S. Department of Agriculture’s Animal & Plant Health Inspection Service (APHIS) confirmed the presence of New World screwworm in Key deer from National Key Deer Refuge in Big Pine Key, Fla.

USDA’s National Veterinary Services Laboratories in Ames, Iowa, confirmed this is a local infestation of New World screwworm (Cochliomyia hominivorax). This is the first local infestation in the U.S. in more than 30 years. In response to this infestation, Florida commissioner of agriculture Adam H. Putnam declared an agricultural state of emergency in Monroe County, Fla.

Additional deer from the same refuge and a few pets in the local area exhibited potentially similar infestations over the past two months, although no larvae were collected and tested in those cases, APHIS said. All of the potentially affected animals are from the same Key. There have been no human or livestock cases.

Animal health and wildlife officials at the state and federal levels are working jointly to address these findings. Response efforts will include fly trapping to determine the extent of the infestation, release of sterile flies to prevent reproduction and disease surveillance to look for additional cases in animals, APHIS said. The initial goal will be to keep the infestation from spreading to new areas while eradicating the New World screwworm flies from the affected Keys.

Residents who have warmblooded animals (pets, livestock, etc.) should watch their animals carefully and report any potential cases to 1-800-HELP-FLA (1-800-435-7352); non-Florida residents should call (850) 410-3800. Visitors to the area should ensure that any pets they have with them are also checked, in order to prevent the spread of this infestation.

New World screwworms are fly larvae (maggots) that can infest livestock and other warmblooded animals, including people. They most often enter an animal through an open wound and feed on the animal’s flesh. While they can fly much farther under ideal conditions, adult flies generally do not travel more than a couple of miles if there are suitable host animals in the area. New World screwworm is more likely to spread long distances when infested animals move to new areas and carry the pest there.

In the 1950s, USDA developed a new method to help eradicate screwworms using a form of biological control called the sterile insect technique, which releases infertile male flies in infested areas. When they mate with local females, no offspring result. With fewer fertile mates available in each succeeding generation, the fly, in essence, breeds itself out of existence. USDA used this technique to eradicate the screwworm from the U.S. and worked with other countries in Central America and the Caribbean to eradicate it there as well.

Today, USDA and its partners maintain a permanent sterile fly barrier at the Darien Gap between Panama and Colombia to prevent the establishment of any screwworm flies that enter from South America.

In response to the announcement, experts with the University of Florida Institute of Food & Agricultural Sciences (IFAS) and College of Veterinary Medicine are taking steps to educate ranchers, property owners and residents about the pest and assist in eradication efforts in the Florida Keys, where the fly’s larvae were found to be infesting wild deer.

Jack Payne, University of Florida senior vice president for agriculture and natural resources, noted that the outbreak appears to be limited to a small area but affirmed that strong, immediate action is needed to manage the outbreak and resolve the situation. He confirmed that IFAS personnel will be assisting colleagues with USDA and the Florida Department of Agriculture & Consumer Services.

“Florida producers know all too well that we can almost never completely rule out the reappearance of pests and pathogens that were believed to be eradicated,” Payne said. “The good news is, IFAS has dealt with this kind of unexpected crisis before, and we’re already fully engaged in this effort.”

James Lloyd, dean of the University of Florida College of Veterinary Medicine, echoed Payne’s sentiments and noted that a college faculty member, parasitologist Heather Walden, was involved in confirming the initial identification of specimens collected from infected deer.

“There’s no cause for alarm, but we are very concerned because the New World screwworm fly historically was one of the most serious pests affecting Florida livestock production,” Lloyd said. He added that no screwworm cases have been reported in livestock or people as part of this outbreak.

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