USDA Confirms New World Screwworm in Florida
October 7, 2016

The United States Department of Agriculture's Animal and Plant Health Inspection Service confirmed the presence of New World screwworm in Key deer from the National Key Deer Refuge in Big Pine Key, Fla. USDA's National Veterinary Services Laboratories in Ames, Iowa, confirms this is a local infestation of New World screwworm. This is the first local infestation in the United States 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 in the past two months, though no larvae were collected and tested in those cases. 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. 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 warm-blooded animals (pets, livestock, etc.) should watch their animals carefully and report any potential cases to 800-435-7352; non-Florida residents should call 850-410-3800. Visitors to the area should ensure any pets that are with them are also checked, in order to prevent the spread of this infestation.

While human cases of New World screwworm are rare, they have occurred, and public health officials are involved in the response. For more information about this disease in humans, please contact your local public health department. Using fly repellents and keeping skin wounds clean and protected from flies can help prevent infection with screwworm in both people and animals.

New World screwworms are fly larvae (maggots) that can infest livestock and other warm-blooded animals, including people. They most often enter an animal through an open wound and feed on the animal's living 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 screwworm 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 screwworm from the U.S. and worked with other countries in Central America and the Caribbean to eradicate it there as well.

The spread of the New World screwworm across the United States would be devastating to the U.S. sheep industry, as well as to all other livestock and humans.

An APHIS factsheet on the New World screwworm is available at www.aphis.usda.gov/publications/animal_health/2014/fs_new_world_screwworm.pdf. Also, during the 2013 American Sheep Industry Association Convention, William Edmiston, DVM, offered a presentation on Screwworm Myiasis. That presentation is available on the ASI website at www.sheepusa.org/ResearchEducation_Presentations_2013Convention.