A foreign maggot species that feeds on the living flesh of animals and humans has recently been found in South Florida. The invasive species, called New World screwworms, are fly larvae (maggots) that can infest livestock and other warm-blooded animals, including people.
Screwworms 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. The New World screwworm (Cochliomyia hominivorax) has not been widely present in the United States since the 1960s, but is still found in most of South America and in five Caribbean countries.
According to Dan Clark, Manager of the Florida Keys Wildlife Refuges Complex, more than 50 endangered Key deer were in such deteriorated conditions after being eaten alive by the maggots that euthanasia was necessary, with at least eight having been euthanized between last Sunday and Monday.
In response to the recent screwworm infestation, the U.S. Department of Agriculture and the Florida Department of Agriculture and Consumer Services, as well as partnering agencies, are implementing an aggressive eradication effort in order not only to protect the Key deer, but also to protect human health, Florida’s livestock industry, and other animals including pets should the pest spread.
Although the occurrence of screwworms in humans is less common than in livestock or other mammals, people are urged to keep wounds clean and closely monitor open cuts and wounds for the presence of maggots. Anyone who suspects the presence of screwworms should contact a physician immediately.
The adult screwworm fly is the size of a common housefly, or slightly larger, but different in color and appearance. The screwworm fly has orange eyes and a metallic dark blue to blue-green or gray body. It also has three dark stripes running down its back, with the middle stripe shorter than the outer two.
A female screwworm fly typically mates once in her lifetime and lays her eggs on or near an open wound or the mucous membranes of an animal’s nose, mouth or ears. In her lifespan, the screwworm fly can produce thousands of offspring. The eggs hatch into larvae within a day and then feed on the animal’s tissue for five to seven days before maturing. The mature larvae then tunnel into the ground and emerge as adults, ready to mate and continue the cycle.
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.