First FDA-Approved Solution Targets New World Screwworm in Cattle Herds

Zoetis Inc. announced today the first and only parasite control product for New World screwworm (NWS). Dectomax-CA1 Injectable received conditional approval from the U.S. Food and Drug Administration (FDA) for the prevention and treatment of infestations caused by the larvae of Cochliomyia hominivorax (New World screwworm) and prevention of reinfestation for 21 days. The conditional approval applies to beef cattle, female dairy cattle less than 20 months of age, pregnant beef cows, newborn calves, and bulls.

NWS remains a looming threat for U.S. livestock producers as it continues its northward expansion. Positive cases of the pest – which had previously been eradicated in most of Central America – have been reported in Sabinas Hidalgo, Mexico, less than 70 miles from the U.S. border. The USDA’s Animal and Plant Health Inspection Service estimate that a NWS outbreak similar to the 1976 outbreak in Texas could cost Texas producers $732 million per year and the Texas economy a loss of $1.8 billion.

“New World screwworm has the potential to bring unprecedented economic and animal health harm to livestock producers,” said Mike Lormore, director of cattle and pork technical services at Zoetis. “Our top priority is to support keeping animals healthy and provide timely, efficacious solutions to our customers and partners. With this conditional approval, Dectomax-CA1 Injectable can now be used as part of safe, effective control measures against New World screwworm.”

Availability

In the first half of 2026, producers and veterinarians will see the 250-milliliter and 500-milliliter bottles of Dectomax Injectable with a new label for Dectomax-CA1 (doramectin injection). Dectomax-CA1 is the same doramectin formulation as Dectomax Injectable.

Dectomax-CA1 is conditionally approved by the FDA pending a full demonstration of effectiveness under NADA 141-616.

Dectomax and Dectomax-CA1 Injectable for use in cattle have a 35-day pre-slaughter withdrawal period. Do not use in female dairy cattle 20 months of age or older. Do not use in calves to be processed for veal. Dectomax Injectable for use in swine has a 24-day pre-slaughter withdrawal period. Use of Dectomax or Dectomax-CA1 in dogs may result in fatalities. Consult your veterinarian for assistance in the diagnosis, treatment, and control of parasitism.

Strategic Prevention

Livestock producers are encouraged to work closely with their herd veterinarian to implement strategic prevention and control measures. Early detection of NWS and rapid response are critical to protecting the health of animals and the livestock industry.

Adult NWS flies have orange eyes, metallic blue or green bodies, and three dark stripes down their back. They are similar in size to the common housefly. The larvae are tapered on both ends, and appear pale in color with encircling bands of dark spines. The larvae feed on live flesh, burrowing into open wounds and mucous membranes. They are visible by the third day of infection. 

Producers are encouraged to immediately report any suspicious wounds, maggots, or infestations to their local accredited veterinarian, state animal health official, or the USDA’s Animal and Plant Health Inspection Service.