By Shelby Shank
Field Editor

While New World screwworm is widely known for the devastating damage it can cause to cattle and wildlife, experts warn the parasite can also pose serious threat to humans and pets.

New World screwworm causes a condition known as myiasis, the infestation of living tissue by fly larvae. Unlike other maggots that feed on dead tissue, the screwworm larvae feed on living flesh, causing painful and rapidly worsening wounds.

Dogs and cats are particularly vulnerable because minor injuries can attract screwworm flies. Pet owners are encouraged to check animals daily for wounds—including areas of previous tick bites—and monitor for foul odors, tissue damage or signs of fly larvae in wounds.

It’s also important to assess the pet’s environment for items that may cause injury, such as metal collars or chain, wire fencing and sharp vegetation that could create small wounds that may attract flies.

If left untreated, these infestations can quickly become fatal for pets.

Pet owners should watch for unusual behavior, such as wound licking or irritation. Animals may lose interest in food or become aggressive or lethargic due to irritability and associated infestations.

Although human cases are uncommon, health officials say awareness remains important.

According to the U.S. Department of Health and Human Services, one travel-related case had been reported in the U.S. as of January.

Experts note infections typically occur when individuals travel to areas where the parasite is present or when they are exposed to animals carrying the fly.

Regions or countries where screwworm is consistently present include South America, Cuba, Haiti and the Dominican Republic, and individuals working closely with livestock or wildlife in these areas may face increased risk.

Open wounds are one of the primary factors that attract screwworm flies. Even small injuries, like scratches, insect bites or surgical wounds, can provide an entry point for the parasite.

People with certain medical conditions, including peripheral vascular disease or diabetes, may also face elevated risk if wounds are slow to heal.

Recognizing the symptoms early is critical.

Signs of an infestation can include skin lesions that do not heal and worsen over time, painful or bleeding sores and a foul odor coming from a wound. In some cases, individuals may feel movement in the wound or notice larvae present in the affected tissue.

Infestations can also occur in the nose, mouth or eyes.

Preventative measures can help reduce risk, such as keeping wounds clean and covered is one of the most effective ways to prevent flies from laying eggs. Wearing loose-fitting, long-sleeved clothing and socks can also limit exposed skin in areas where screwworm flies may be present.

Although there are currently no confirmed cases of New World screwworm in Texas, experts note it’s still important to stay alert. Recognizing symptoms early and taking simple precautions can help protect both people and pets.

Healthcare providers should report potential human cases to their regional Zoonosis Control office immediately, followed by the CDC at 404-718-4745.

Suspected infestation in livestock and other domestic animals, contact the Texas Animal Health Commission at 800-550-8242.

For wildlife infestations, contact the local Texas Parks and Wildlife Department biologist or call 512-389-4505.

For more information from USDA, visit screwworm.gov.

Additional information is available at screwwormtx.org.