Deadly fly larvae infests federally endangered Key deer population, more than 40 are euthanized

A Key deer stands in shallow water on Big Pine Key.
A Key deer stands in shallow water on Big Pine Key. U.S. Fish and Wildlife Service

The death of dozens of federally endangered Key deer in the past few weeks prompted federal and state officials to set up a checkpoint in Key Largo Monday to inspect all animals leaving Monroe County for signs of a deadly parasitic fly larvae.

Health officials have had to euthanize more than 40 Key deer infected with screwworm fly maggots since September, and they don’t want the infestation to spread to pets and livestock outside of the county, said Dan Clark, manager of the National Key Deer Refuge on Big Pine Key.

A state quarantine has been put in place so animals in the Keys cannot leave Monroe County without passing through a Florida Department of Agriculture and Consumer Services checkpoint at mile marker 106. The checkpoint will likely be in place through the end of the year, at least.

There have been “a few reported cases of pets that have had screwworms,” according to a state Department of Agriculture press release.

This is the first local infestation of screwworm in the United States in more than 30 years, according to the United States Department of Agriculture. Florida Commissioner of Agriculture Adam H. Putnam declared an “agricultural state of emergency in Monroe County” on Monday.

The screwworm fly is not widely present in the United States, but it is found in most South American countries and in five countries in the Caribbean.

Screwworm flies lay their eggs in the wounds of injured animals. The larvae hatches and then feed on the wound, which then becomes larger, according to a fact sheet from the Center for Food Security and Public Health at Iowa State University.

Humans can be infected the same way the flies infect animals, the fact sheet states.

“This foreign animal disease poses a grave threat to wildlife, livestock and domestic pets in Florida. Though rare, it can even infect humans. We’ve eradicated this from Florida before, and we’ll do it again,” Putnam said. “We will work with our partners on the federal, state and local level to protect our residents, animals and wildlife by eliminating the screwworm from Florida. The public’s assistance is crucial to the success of this eradication program.”

The adult screwworm fly is about the size of a common housefly, or slightly larger, but different in color and appearance, according to the state Department of Agriculture. Adults have orange eyes and a metallic dark blue to blue-green or gray bodies. They have three dark stripes running down their back, with the middle stripe shorter than the outer two.

This is a developing story.

David Goodhue: 305-440-3204