Just as horrible as its name indicates, a screwworm infestation begins when an adult female lays between 100 to 400 eggs inside an open wound. Larvae then hatch and "screw down" into the host organism, feeding on flesh along the way. After causing substantial damage, distress and sometimes death to the animal, the screwworms fall away from their host to pupate and turn into flies.
Once eradicated from Florida, officials are now warning residents who own warm-blooded animals like livestock or pets that the screwworm is back.
"The screwworm is a potentially devastating animal disease that sends shivers down every rancher's spine," Commissioner of Agriculture Adam H. Putnam said in a press release from the Florida Department of Agriculture. "It's been more than five decades since the screwworm last infested Florida, and I've grown up hearing the horror stories from the last occurrence."
Wildlife officials studying the endangered Key deer from a wildlife refuge in Big Pine Key, Florida, discovered several individuals struck with the New World screwworm. The infestation is worrisome because of its ability to quickly spread.
Officials are calling for residents to be alert to the possible signs of an animal infected with screwworm, as some pets also have exhibited signs of infection. Symptoms include a festering wound or sore, unexplained lumps under the skin, and an unusual discharge or foul odor.
To help contain the Big Pine Key infestation, the state also is implementing a highway "Animal Zone Health Checkpoint" to prevent potentially-infected pets from moving north.
The 1950s outbreak
In the mid-1950's during the worm's last appearance, entomologists studying ways to counter the insect's devastating $200 million-dollar annual impact discovered they could render males sterile through exposure to X-rays. Because female screwworm flies only mate once, releasing millions of sterilized males into infested areas would effectively break the life cycle.
When Florida embraced the sterilization method in 1958, it took less than one year for screwworm populations to be completely wiped out.
“This foreign animal disease poses a grave threat to wildlife, livestock and domestic pets in Florida," Putnam added. "Though rare, it can even infect humans. We've eradicated this from Florida before, and we'll do it again."