AUSTIN, Texas — Texas hunters and those who enjoy the outdoors are being warned about an invasive parasite not seen in the United States since the 1960s.
The Texas Parks and Wildlife Department is urging those to monitor for animals affected by New World Screwworm, an invasive flesh-eating fly recently detected in Mexico.
Officials said they detected a cow with screwworms at a checkpoint near the Mexico-Guatemala border. According to the department, the latest detection follows a gradual northward movement of screwworms through both South and Central America.
What are screwworms?
According to the Centers for Disease Control and Prevention, New World screwworms are fly larvae that infest the tissue or flesh of warm-blooded animals. They’re primarily found in South America and the Caribbean.
While screwworms primarily infest livestock, they can also affect humans and wildlife including deer and birds. People who visit those areas and have an open wound are at greater risk of becoming infected.
Infestations start when female flies lay eggs on open wounds or other parts. Wounds can be as small as a tick bite that attracts a female fly to feed and lay her eggs. A female can lay 200 to 300 eggs at once and 3,000 eggs during her short lifespan.
The eggs hatch into maggots that then burrow into the wound to feed on living flesh before emerging as adult screwworm flies.
Symptoms of screwworm
The CDC says infestations are very painful and that maggots could be visible in an open wound. They can also be in your nose, eyes, or mouth.
Symptoms include:
- Unexplained wounds or sores that do not heal
- Skin wounds or sores that worsen over time
- Bleeding from open sores
- Feeling larvae movement within a skin wound or sore, nose, mouth, or eyes
- Seeing maggots around or in open sores
- A foul-smelling odor from the site of the infestation
- Fever or chills from a secondary bacterial infection
Officials say you should clean and cover all wounds in addition to applying insect repellant while outside to prevent infection.
Screwworms in the United States
The invasive parasites became a major problem in the United States by the 1950s.
According to the University of Texas at Austin, screwworms were causing about $200 million a year in devastation to livestock ranchers, equal to about $1.8 billion today. After researchers learned about the flies’ mating habits, a technique that would sterilize the flies came to the United States in 1955.
In 1960, Texas and New Mexico became involved in the sterilization process, which led to a South Texas plant producing around 200 million sterile flies a week. Four years later, screwworms were eradicated from Texas. By 1966, officials said the screwworms had been eradicated from the United States.
If you spot an animal you suspect may be infected, contact the Texas Animal Health Commission or the U.S. Department of Agriculture immediately.