In June 2026, New World screwworm—a parasitic fly whose larvae infest open wounds—returned to the United States for the first time in decades, detected in livestock in southern Texas. The September 2026 FDA emergency approvals of three medications for cats marked the first-ever authorized treatment options for screwworm infection in companion animals. For cat owners across most of the U.S., the immediate risk remains low, but residents of Texas and New Mexico should know the danger signs and have access to emergency veterinary care.
The reemergence of screwworm in the United States reflects a shift in the disease landscape that pet owners previously did not face. At least one infected cat has been confirmed in northern Mexico, confirming that companion animals can carry screwworm infection alongside the livestock cases detected in Texas and New Mexico. Understanding the threat, the new treatment options, and your cat's geographic risk profile is the practical step forward.
Table of Contents
- What is New World screwworm and where is it now?
- Three new FDA emergency treatments are now available for cats
- Your actual risk depends on where you live
- What to do if you suspect screwworm infection
- Traditional parasites in cats haven't changed
What is New World screwworm and where is it now?
new World screwworm is a parasitic fly whose larvae develop inside open wounds on living animals. The infestation was eradicated from the continental U.S. by the 1960s.
In June 2026, USDA Animal and Plant Health Inspection Service confirmed the parasite's return, detecting larvae in a calf in southern Texas—marking the end of a 50-year absence. Since that initial detection, cases have been confirmed in livestock in both Texas and New Mexico. The geographic distribution remains limited to the southwestern border region, but surveillance is ongoing to catch any expansion before it spreads.
Three new FDA emergency treatments are now available for cats
Until september 2026, no veterinary medications existed specifically authorized for screwworm treatment or prevention in cats. The FDA issued emergency authorization for Capstar (nitenpyram) on September 3, 2026, making it the first over-the-counter option approved for both prevention and treatment of screwworm myiasis (the infection caused by the larvae) in cats weighing at least 2 pounds and 4 weeks or older.
Credelio CAT (lotilaner) chewable tablets and NexGard COMBO topical solution received emergency authorization shortly after for treating screwworm myiasis, giving veterinarians additional prescription options. Capstar is available in two tablet sizes (11.4 mg and 57 mg) with dosing based on body weight, and requires no prescription, making emergency prevention and treatment accessible without a veterinary visit in threatened areas.
Your actual risk depends on where you live
The geographic distribution of screwworm risk is not uniform across the United States. Pet owners in Texas and New Mexico face significantly elevated screwworm risk compared to other U.S. states; however, the overall risk to most American cat owners remains low.
This distinction matters: a cat owner in Seattle or Boston faces minimal risk and does not need preventive treatment. A cat owner in El Paso or southern New Mexico has a different calculus. Early detection and treatment dramatically improve outcomes in screwworm myiasis, which is why geographic awareness is actionable rather than merely cautionary. If you live in or regularly travel to Texas or New Mexico with a cat, emergency veterinary access and knowledge of the condition become practical precautions.
What to do if you suspect screwworm infection
If your cat develops an open wound, cut, bite, or sore—especially in Texas, New Mexico, or border regions—veterinary examination becomes urgent rather than routine. A wound that smells unusual, drains abnormally, or does not heal as expected after injury warrants immediate veterinary assessment. Screwworm myiasis can progress rapidly in untreated cases, which is why speed of diagnosis and treatment matters.
If your veterinarian suspects screwworm infection, treatment options now exist that did not before September 2026. Capstar can be purchased over-the-counter for treatment, while Credelio CAT and NexGard COMBO may be prescribed. Outside the high-risk zone, standard wound care and routine parasite prevention remain your defense.
Traditional parasites in cats haven't changed
The reemergence of screwworm does not alter the parasite prevention landscape for the vast majority of cat owners. Roundworms, hookworms, and tapeworms remain controllable through established preventive protocols that have not changed in 2026. Kittens should be dewormed every 2 weeks starting at 3 weeks of age, continuing until 9 weeks old, then monthly until 6 months.
Adult cats typically do not require additional deworming unless a specific infestation is detected. The screwworm reemergence is a localized, geographic issue for now. Your cat's existing parasite prevention regimen—whether flea-tick topicals, oral preventatives, or routine deworming—addresses the full range of common feline parasites and remains your best defense across the country.