U.S. Authorities Intensify Measures Against New World Screwworm Outbreak

U.S. health authorities are intensifying their response to the New World screwworm, a flesh-eating parasite recently found in livestock. While primarily affecting animals, it can also pose risks to humans. The CDC and FDA are coordinating efforts to monitor and control the outbreak, with new treatments approved for pets. Awareness and preventive measures are crucial for those working with animals in affected regions. This article explores the nature of the parasite, current cases, and how to protect both pets and livestock.

By Narendra Chaudhary Jun 17, 2026, 08:17 IST

Introduction to the New World Screwworm

Health officials in the United States are ramping up their response to the New World screwworm, a parasitic threat that has recently emerged in livestock across southern Texas and parts of New Mexico. Although primarily a concern for animals, experts warn that under certain circumstances, this parasite can also affect humans. In light of this, the U.S. Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA) have initiated a comprehensive response. The CDC has activated its Emergency Operations Center to oversee surveillance, prevention, and response efforts in collaboration with the U.S. Department of Agriculture (USDA) and state health agencies. While the general public's risk remains minimal, officials are advising veterinarians, healthcare professionals, and animal owners to stay alert.

Understanding the New World Screwworm

What is the New World Screwworm?

The New World screwworm is the larval form of the fly species Cochliomyia hominivorax, which lays its eggs in open wounds or natural openings of warm-blooded animals. These eggs hatch into larvae within hours, which then invade healthy tissue, leading to a painful condition known as myiasis. Unlike many parasites that thrive on dead tissue, screwworm larvae consume living flesh, making infestations particularly harmful if not addressed promptly. The parasite poses a significant threat to:

Cattle
Sheep
Goats
Horses
Dogs and cats
Wildlife

While human infections are rare, they can occur if flies deposit eggs in untreated wounds or body openings.

Current Situation in the U.S.

As reported by the USDA, there have been 12 confirmed cases of New World screwworm in domestic animals, including cattle, goats, and sheep, in southern Texas and one county in New Mexico as of June 11. Importantly, the CDC has indicated that no human cases have been documented during this outbreak. Officials have clarified that the parasite does not transmit from person to person or from infected animals to humans; infection occurs only when an adult fly lays eggs in an open wound or body opening.

FDA Approves First Generic Treatment for Pets

FDA Authorizes First Generic Treatment for Pets

In a crucial step to enhance outbreak management, the FDA has granted Emergency Use Authorization (EUA) for the first generic treatment aimed at New World screwworm infestations in companion animals. The approved medication consists of generic nitenpyram tablets, suitable for use in dogs, puppies, cats, and kittens. These tablets can be purchased over the counter and are dosed based on the animal's weight. The medication acts quickly, eliminating most screwworm larvae within hours. Pet owners are advised to give a second dose six hours after the first to ensure maximum effectiveness. However, experts warn that this treatment does not eliminate dead larvae or prevent future infestations, making veterinary care essential for proper wound management, removal of remaining larvae, and monitoring for secondary infections. The FDA also cautions against using this drug in animals weighing less than two pounds or younger than four weeks.

Protecting Pets and Livestock

How to Protect Pets and Livestock

Health officials recommend several preventive strategies:

Regularly check animals for cuts, wounds, or unusual swelling.
Promptly clean and treat any wounds.
Seek veterinary assistance if maggots or unusual tissue damage are observed.
Maintain cleanliness in animal housing and minimize fly exposure.
Immediately report any suspected screwworm cases to animal health authorities.

Human Health Concerns

Should Humans Be Concerned?

While the current public health risk is low, experts emphasize the importance of awareness, particularly for individuals working with livestock or animals in affected areas. The U.S. successfully eradicated the New World screwworm decades ago, and officials are optimistic about achieving this again through swift surveillance, timely treatment, and coordinated public health efforts. Early detection, responsible wound care, and prompt veterinary intervention are crucial defenses against this harmful parasite.