A destructive parasite found in livestock and other warm-blooded animals was said to be eliminated during the late 20th Century. But they’re back!

The U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (USDA APHIS) confirmed the presence of the New World screwworm found in a stray dog in Florida’s mainland, according to Drovers CattleNetwork.

USDA, along with state and federal health agencies, has frequently engaged in efforts to eradicate screwworms from the Florida Keys, including with the release of sterile flies.

The sterile males mate unsuccessfully with wild females, and the breeding success eventually becomes so low that the species is eradicated from the target area.

The discovery of the pest does cause a concern for Florida. Officials hope the spreading will be eradicated before posing a threat to cattle and other livestock.

The screwworm eradication program has been underway in Florida since October 2016, according to Drovers.

“Screwworm larvae burrows into animal flesh and begins feeding on it, infection follows and, if not treated, those animals will likely be lost. Everyone should be mindful of the issue and be quick to act if they find it,” Tracy Tomascik, Texas Farm Bureau (TFB) associate director of Commodity and Regulatory Activities, said.