The New Year is starting with a fresh warning for those who work with animals in Texas. The state’s Parks and Wildlife Department is asking hunters and other outdoor enthusiasts to watch out for animals that may be impacted by dangerous “maneater” parasites from flies that lay eggs in open wounds, nostrils, eyes and mouths. 

The advisory, posted by the department on Dec. 30, was issued for outdoor enthusiasts in South Texas after the New World Screwworm was recently found in a cow in the southern Mexico state of Chiapas.

According to the Texas Parks and Wildlife Department, the New World Screwworm has been making its way further north through the Americas. 

“As a protective measure, animal health officials ask those along the southern Texas border to monitor wildlife, livestock and pets for clinical signs of NWS and immediately report potential cases,” the department said. 

What is the New World Screwworm?

According to the U.S. Department of Agriculture, the New World Screwworm “is a devastating pest.”

“When NWS fly larvae (maggots) burrow into the flesh of a living animal, they cause serious, often deadly damage to the animal,” the USDA says. “NWS can infest livestock, pets, wildlife, occasionally birds, and in rare cases, people.”

The Texas parks department says the maggots will lay eggs in “open wounds or orifices of live tissue such as nostrils, eyes or mouth.” Such an infestation is known as New World screwworm myiasis. 

“These eggs hatch into dangerous parasitic larvae, and the maggots burrow or screw into flesh with sharp mouth hooks. Wounds can become larger, and an infestation can often cause serious, deadly damage or death to the infected animal.” 

The scientific name for the parasite, Cochliomyia hominivorax, is roughly translated to “maneater,” according to the USDA’s Animal and Plant Health Inspection Service. 

“It is an appropriate name,” the agency added, saying that the screwworm was once prevalent in the U.S., with 230,000 cases reported just in 1935. But then scientists developed a way to release sterilized male blow flies, and since female blow flies only mate once, the agency says it “effectively removed that female and her potential offspring from the population.” 

It’s believed that the elimination of the New World Screwworm has saved U.S. agriculture workers nearly $900 million in lost livestock annually, the agency said. 

Where are New World Screwworms found?

New World Screwworms are endemic in Cuba, Haiti, the Dominican Republic and countries in South America. The USDA says that cases of the parasite, however, are also spreading north to Costa Rica, Nicaragua, Honduras, Guatemala and Mexico. 

“Although USDA eradicated NWS from the United States in 1966 using sterile insect technique, there is a constant risk of re-introduction into the United States,” the USDA’s Animal and Plant Health Inspection Service says. “To prevent the northward movement of this pest from South America to NWS-free areas in Central and North America, APHIS collaborates with Panama to maintain a barrier zone in eastern Panama.”

What to know about New World Screwworm Myiasis 

The Texas Parks and Wildlife Department says that female New World Screwworm flies are “drawn to the odor of a wound or natural opening on a live, warm-blooded animal.” There, just one fly can lay up to 300 eggs at a time, and she may lay up to 3,000 eggs during her lifetime. 

After eggs hatch, they become larvae or maggots that burrow into an opening to feed. Once they feed, they drop to the ground, burrow into the soil and emerge as adult flies. The adult flies can travel long distances, the department says, “and the movement of infested livestock or wildlife can increase the rate of spread.” 

Signs of NWS Myiasis include irritated or depressed behavior, loss of appetite, head shaking, the smell of decaying flesh, the presence of maggots in wounds and isolation from other animals or people. 

To prevent an infestation, Texas officials say to clean and cover all wounds when spending time outdoors, especially in NWS-affected areas, and to apply insect repellant to outdoor clothing.