Indiana warns of dangerous fly pest called New World screwworm

The Indiana State Board of Animal Health has issued a warning about a harmful insect pest called the New World screwworm. The pest has been found in Texas and New Mexico, and officials are worried it could spread to Indiana. Animal owners, farmers, and pet owners are being asked to watch their animals closely and follow new rules about moving animals into the state.

New World screwworms are flies that lay their eggs in open wounds on warm-blooded animals. When the eggs hatch, the larvae — also called maggots — burrow into the flesh in a spiral, screw-like pattern and feed on living tissue. In rare cases, the larvae can also infest humans. The flies have orange eyes, a shiny blue or green body, and three dark stripes on their backs.

The Indiana State Board of Animal Health issued its advisory on June 9. It said that even though screwworms have not been found in Indiana yet, they could be brought into the state by people or animals that traveled from an infested area. Because of this risk, new movement rules are now in place for animals coming from Texas and New Mexico.

Under the new rules, any livestock or pet coming from an infested area must have paperwork from a USDA-approved veterinarian. This certificate must be issued within five days of the animal traveling to Indiana. Livestock and poultry must also show proof that they were treated for screwworms within 14 days of travel, while cats and dogs must be treated within five days.

Animal owners should look for warning signs on their pets and livestock. These signs include unusual flies or maggots near wounds, sores that keep growing or smell like decay, and animals acting uncomfortable — like shaking their heads or seeming irritated. If the infestation is not treated quickly, it can cause rapid health decline and even death, according to Texas A&M University.

Screwworms were mostly wiped out in the United States back in the late 1960s. Scientists did this by releasing large numbers of sterile male flies into the wild. Because female screwworm flies only mate once in their lives, they produce no eggs after mating with a sterile male. The USDA has been dropping sterile flies over south Texas since February to slow the current outbreak.

Local fairs and community events are also paying attention to the advisory. Porter County Fair volunteer Andrew Lucas said the fair follows guidance from the Indiana State Board of Animal Health and Purdue University. 'Our 4-Hers go through animal health and quality training. We are ready to follow any guidance handed down from these partners,' Lucas said.

People who live in rural areas with farms and outdoor animals face a greater risk if screwworms are ever found nearby. The Lake County Health Department advises residents to keep cuts and wounds clean and covered, and to see a doctor if a wound becomes infected or does not heal. Pet owners should make sure their animals get regular veterinary checkups.

In rare cases, screwworms can affect humans. In August 2025, the United States recorded its first human screwworm case in decades when a Maryland resident who had recently traveled to El Salvador came home with larvae living inside their tissue. The infection was treated successfully, but officials say anyone who suspects an infestation should seek medical help right away.

If a pet or farm animal may be infested, the owner should contact a veterinarian immediately. The vet should then report the suspected case to the Indiana State Board of Animal Health and the Indiana Department of Natural Resources. Healthcare providers who think a human patient may be infected should contact the Indiana Department of Health for instructions on how to submit samples for testing.