Reviewed by: Cindy Hatcher
What is the New World screwworm + what Alabamians should know
Reading time: 5 minutes
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If you pay attention to the news, you’ve likely seen countless articles about the New World screwworm, an invasive parasitic fly that recently reemerged in Texas—despite being eradicated from the United States in 1966. While Alabama is not currently in the hot zone, researchers say it’s exactly the kind of threat worth watching closely.
To learn more about the New World screwworm and the threat it poses, we spoke with Dr. Kathryn E. Reif, a parasitology and vector-borne disease expert at Auburn University’s College of Veterinary Medicine who has spent her career studying arthropods like ticks—and the diseases they carry.
What is the New World screwworm?
Despite its alarming name, the New World screwworm isn’t a worm at all—it’s actually a species of parasitic fly known scientifically as Cochliomyia hominivorax. Endemic to South America, Central America and parts of the Caribbean, the New World screwworm was officially eradicated from the United States in 1966. However, the species has recently reemerged in parts of Texas, with 25 cases confirmed as of Monday, June 29.
At first glance, the New World Screwworm looks like your run-of-the-mill housefly. So what makes this species so dangerous? According to Dr. Reif, the key issue is where the fly lays its eggs:
“What’s unique about the New World screwworm is that the female fly deposits her eggs in open wounds on living tissue; not decaying carcasses. Once the eggs hatch, the larvae feed directly on the host’s tissue from inside the wound. It’s kind of like the morbid version of the Hungry, Hungry Caterpillar—except this time it’s in living tissue.”
Kathryn E. Reif, MSPH, PhD
Since the female New World screwworm can lay several thousand eggs during its lifespan, even a single untreated case can quickly trigger a chain reaction that attracts even more flies to the infected animal. While it is often thought of as a livestock problem, the New World screwworm will readily infest pets and people too—and to make matters worse, the fly can be drawn to wounds as small as a tick bite.
What Alabamians need to know about the New World screwworm
When you want to learn more about an invasive parasite like the New World screwworm, you go straight to the experts.
A parasitology and vector-borne disease expert at Auburn University, Dr. Kathryn E. Reif’s research focuses on ticks and other arthropods that impact animal and public health. After earning her Master of Science in Public Health from Tulane University and her PhD in pathobiology from Louisiana State University, Dr. Reif built a career studying parasites and the diseases they transmit. Her work has taken her from mosquito surveillance in New Orleans to tick-borne disease research at veterinary schools and laboratories across the country.
Today, Dr. Reif serves as an Associate Professor in the Department of Pathobiology and the Bailey-Goodwin Endowed Chair in Parasitology in the College of Veterinary Medicine at Auburn University, where she works with livestock producers, veterinarians and researchers to better understand emerging threats like the New World screwworm.
With 12 confirmed U.S. cases so far, officials are working to stop the New World screwworm from gaining a foothold. While sterile fly releases helped eradicate the pest decades ago, current production tops out at about 100 million flies per week—far short of the estimated 500 million that could be needed if the outbreak expands.
“We move animals around the country a lot, so there’s always a concern that we are moving an infested animal from one place to another. However, the USDA’s Animal & Plant Health Inspection Service has implemented strict quarantine and animal health certificates to help contain the spread. The bigger concern is if the fly gets a foothold in the wildlife population; if the New World screwworm gets into the wild deer and feral swine populations, we could see the outbreak spread rapidly.”
Kathryn E. Reif, MSPH, PhD
While Dr. Reif cautioned against panic, she noted that the reemergence of the New World screwworm is something that all livestock producers and veterinarians should keep top of mind. Dr. Reif’s guidance boils down to a few simple actions:
- Check animals regularly for wounds
- Treat even small injuries quickly
- Maintain parasite prevention, including ticks
- Contact a veterinarian immediately if maggots are seen in a living wound
- Avoid relying on social media for treatment advice
Stay up to date on the New World Screwworm
For the latest on confirmed cases, quarantine zones, animal movement requirements and federal response efforts, visit screwworm.gov, a centralized resource maintained by the USDA with guidance for livestock producers, veterinarians, pet owners and more.
Want to learn more about the New World screwworm and its potential threat? Click here to see how professors at Auburn University’s College of Veterinary Medicine are weighing in.
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