MIAMI, Sept. 23, 2025 /PRNewswire/ -- The New World Screwworm parasite, a serious threat to both humans and animals, has now surfaced in the U.S. On August 4, 2025, the first human case was confirmed in Maryland, in a resident returning from El Salvador. To date, no other U.S. cases have been reported beyond this traveler. The current outbreak began breaching the biological barrier in July 2023, spreading north from Central America into Mexico. The USDA has repeatedly halted the importation of cattle, horses, and bison from Mexico, with the most recent blockade in May 2025. Wags Animal Hospital urges pet owners to be alert, prepared, and proactive as this flesh-eating parasite poses risks to any warm-blooded animal. The condition is potentially fatal, but treatable.
The New World Screwworm is the larval stage (maggot stage) of the Cochliomyia hominivorax fly. The fly finds a wound as small as a tick bite, then lays 200–300 eggs at a time, with a lifetime capacity of up to 3,000 eggs. These hatch into larvae that feed on live flesh, unlike most fly maggots that target dead tissue. Larvae are visible by day three.
Pet owners may notice bloody discharge, foul odor, worsening wounds, lethargy, and anorexia. Without treatment, fatalities are expected within 7–14 days due to disease progression, secondary infections, and inflammatory responses. The full life cycle of the screwworm takes 21–30 days, repeating itself as larvae pupate in the ground and emerge as adult flies.
The economic and physical impact of the New World Screwworm is significant. In the 1950s and 1960s, the parasite spread from Louisiana to California, affecting 7 million cattle and costing the U.S. economy the equivalent of $1.8 billion in today's dollars. For perspective, the Highly Pathogenic Avian Influenza recently disrupted the egg supply chain, causing billions in losses and spiking consumer prices. A similar scenario could unfold with beef if screwworm invasions expand.
Prevention and Treatment
Historically, the parasite was eradicated in the U.S. using the Sterile Insect Technique (SIT), in which genetically modified male flies are released to break the reproductive cycle. This program, effective in the 1970s, 1980s, and during a Florida Keys outbreak in 2016, is being revived today. The U.S. currently co-operates a SIT facility in Panama and is developing another in South Texas to protect our border.
The USDA has adopted a five-pronged approach:
To protect pets, treatment is straightforward with certain commonly applied flea/tick prevention products. Wags Animal Hospital carries the prevention needed to treat this disease. Early detection and intervention are critical to avoid the need for surgical care or managing secondary infections. If screwworm infestation is suspected, pet owners should:
"The New World Screwworm affects all of us (whether you walk on two or four legs). Early detection and intervention are key. If we work together, we can protect our communities for years to come." - Dr. Ori Eizenberg Weinger, DVM, Wags Animal Hospital
For questions, concerns, or to schedule an appointment, please contact Wags Animal Hospital, located in Brickell Key, Miami.
About Wags Animal Hospital
At Wags Animal Hospital, we strive to provide personalized medical care, work with clients to help them understand their pets' needs and provide exceptional customer service, all while incorporating the latest advancements in veterinary medicine into our daily operations. Our experienced veterinarians are passionate about helping pets live long, healthy and happy lives. We offer a wide range of services, from wellness and dental checks to advanced treatments, ensuring that dogs and cats receive the best-possible care in a calm and stress-free environment. For more information, reach out to Wags Animal Hospital at 919-624-1124 or email [email protected].
SOURCE Wags Animal Hospital
Share this article