By Gustavo M. Schuenemann and Risa Pesapane el.at
The New World Screwworm (NWS) is a parasitic infestation that has been effectively eradicated in the United States for the past 60 years. However, between June 3 and June 9, 2026, a recent outbreak was reported, with five confirmed cases in Texas (cattle and goat) and one confirmed case in New Mexico (dog). The USDA APHIS provides an up-to-date dashboard with current active cases and their locations. It is important to highlight that NWS is an animal health issue, and not a food safety issue. NWS is not transmitted through the consumption of meat, milk, or other animal products, and it does not pose a food safety risk through properly handled and prepared food products. However, it does negatively impact animal health and has economical consequences for the animal owner.
What is NWS?
It is a parasitic fly (Cochliomyia hominivorax) that lays eggs in and on open wounds and mucous membranes of warm-blooded animals. When larvae hatch (maggot), they burrow into the flesh of these animals and eat healthy living tissue causing the myiasis (infestation with fly maggots). This infestation is seasonal in livestock, with outbreaks linked to warm conditions that favor the fly’s life cycle and host availability, often peaking in the warmer spring and summer months, and being suppressed by cold winters. NWS can infest all warm-blooded animals, including livestock, pets, wildlife, humans, and even birds.
What to Look for in My Animals?
Be alert for the following clinical signs that may indicate NWS infestation:
- Unusual or irritated behavior (restlessness, excessive movement)
- Isolation from the herd or flock (reduced interaction)
- Frequent head shaking or rubbing against objects
- Foul odor with strong smell of tissue decay
- Visible fly larvae (maggots) in wounds or natural body openings
- Bloody or pus-like discharge from wounds
Source : osu.edu