New World Screwworm

The New World screwworm (Cochliomyia hominivorax) poses a serious threat to animals and people in places where it is present. A species of blowfly, New World screwworm larvae (maggots) feed on living tissue of warm-blooded animals and humans, which can cause severe tissue damage if not treated swiftly. The most commonly affected animal species are cattle, dogs, and pigs, but other species of livestock, companion animals, and wildlife can be affected. Infestations in humans, while less common, can also occur.

The fly was eradicated in the United States during the 1960s following a concerted effort by the U.S. Department of Agriculture (USDA) using the sterile insect technique, and it was later eradicated throughout Mexico and Central America. However, New World screwworm has re-emerged across Central America and Mexico in the past few years, and it reached the United States, in Texas, in June 2026. 

A broad swath of federal and state government agencies, health departments, agriculture departments, wildlife groups, non-governmental organizations, research institutions, and industry partners are collaborating to slow the fly’s northward range expansion and engage in domestic response preparation.
 

Screwworm Abatement Through a Public Health Lens: Outcomes and Observations From an Emergency Preparedness Exercise 

In April 2026, the Entomological Society of America (ESA) and the U.S. Centers for Disease Control and Prevention (CDC) brought together more than 100 experts from public health, animal health, government, academia, and industry for an emergency preparedness exercise on New World screwworm. This report summarizes the key outcomes, lessons learned, and recommendations for strengthening collaboration, communication, and response readiness to address screwworm's threat to public health.

Special Collection: Re-invasion of the New World Screwworm in Central and North America

This special collection from the Journal of Medical Entomology and the Journal of Economic Entomology brings together the latest research and perspectives addressing the scientific, operational, and policy challenges of eradication and response. Featuring freely available articles from leading experts, the collection explores advances in surveillance, risk assessment, sterile insect technique programs, and emerging tools needed to protect livestock, wildlife, companion animals, and public health.
 

Podcast: New World Screwworm: Separating Fact from Fear

In this episode of ESA's podcast, Stridulation Station, entomologist Jennifer Gordon, Ph.D., sits down with University of Florida medical and veterinary entomologist Edwin Burgess, Ph.D., to discuss what New World screwworm is, why it poses a serious threat to livestock and wildlife, how it spreads, and why the risk to humans remains extremely low. They explore the fascinating sterile insect technique that successfully eradicated the pest from the United States decades ago, how "sterile flies" are helping fight its return, and why experts are confident it can be controlled again. They also tackle common misconceptions about sterilized flies, food safety, surveillance efforts, and the role of agricultural producers, scientists, veterinarians, and government in responding to the current outbreak. 

Additional Resources