On April 26, 2017, the U.S. Department of Agriculture’s (USDA) announced that the New World screwworm (NWS) had been eradicated from the United States for the second time. The eradication effort involved the release of 154 million sterile flies, 17,000 animal inspections, and about 700 hours of surveillance.

Most of the animals known to have been killed during the infestation with screwworm fly larvae were Key deer, an endangered sub­species of white-tailed deer. Small numbers of other animals also were affected, including at least three dogs, two cats, a pig, and a raccoon with confirmed infestations, according to information from the Florida Department of Agriculture and Consumer Services.

Self-sustaining screwworm populations were eradicated in the U.S. by 1966, although reinfestations occurred through 1982, and two isolated infestations occurred in dogs in 2007 and 2010, USDA information states. Both dogs had traveled to or through Florida.

The USDA eradication program to remove the NWS began in 1957 and finally succeeded in pushing them out of the U.S. nine years later. The program involves releasing sterile flies into the wild to interrupt their breeding cycle. However, the risk of NWS being reintroduced into the U.S. is still a threat today, as NWS endemic to Cuba, Haiti, the Dominican Republic, and various South American countries.

New World screwworm (NWS, Cochliomyia hominivorax) is a devastating pest. NWS maggots 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.