Last fall, the state of Florida reported the first local infestation of New World screwworm in the United States in at least three decades and five decades in Florida. The outbreak began in some endangered Key deer from a wildlife refuge in Big Pine Key, Florida and eventually was reported in a dog in the city of Homestead on Florida’s mainland.

Screwworm larva/ Agricultural Research Service
Screwworm larva/ Agricultural Research Service

Since the outbreak began in October, at least 13 Keys had known infestations mostly in the key deer population, with five confirmed infestations in domestic animals. In fact, at least 10 percent of the Key deer population have been euthanized due to screwworm infestation.

The United States Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) reported this week that they are near eradication of New World Screwworm from the Florida Keys.

They created an interactive screwworm “story map” so the public can look at all the steps they’ve taken to rid the United States of this dangerous pest, and save the Florida Key deer.


LISTEN: Screwworms: An interview with UF professor, Dr. Phillip Kaufman

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 or, in the case of newborns, the navel. They feed on the animal’s living flesh and, if not treated, infestations can be fatal. While New World screwworm (Cochliomyia hominivorax) has not been widely present in the United States since the 1960s, it is still found in most of South America and in five Caribbean countries.

In the 1950s, USDA’s Agricultural Research Service developed a new method to eradicate the pest using a form of biological control called the sterile insect technique. Infertile male flies are released in infested areas. When they mate with local females, no offspring result. With fewer fertile mates available in each succeeding generation, the fly breeds itself out of existence.

USDA began using this technique in Florida in 1957 and eradicated the flies from the entire southeastern United States by 1959. The technique was next applied to the more extensively infested Southwest in 1962. By 1966, self-sustaining screwworm populations were eliminated from the United States.