Weekly Vet Report: 9 Screwworm cases (including a dog), new OTC screwworm treatment authorized, & more

New World screwworm cases rise to 9, including first case in dog

The number of confirmed New World screwworm (NWS) cases in the United States has climbed to 9, according to the latest data from the US Department of Agriculture (USDA).

The outbreak began June 3, when USDA APHIS confirmed NWS in a calf in Zavala County, Texas, marking the parasite's first detection in the United States in decades. A second infected calf was identified in Zavala County on June 5, suggesting the parasite was already established in the area.

The situation expanded beyond a single county on June 7, when officials confirmed 2 additional cases: a bovine in La Salle County, Texas, and a dog in Lea County, New Mexico. The canine case marked the first confirmed companion-animal detection since NWS reemerged in the United States and the first case reported outside Texas.

Additional detections followed quickly. On June 8, USDA confirmed another bovine case in La Salle County and a goat in Gillespie County, Texas. A bovine case in Edwards County was reported June 9. The most recent detections, announced June 11, involved a bovine in Zavala County and a goat in Edwards County, bringing the total number of confirmed cases to 9.

To date, confirmed US cases include 6 cattle, 2 goats, and 1 dog across Texas and New Mexico.

FDA emergency-use-authorizes OTC NWS treatment for pets

As cases continue to rise, the FDA has expanded access to treatment options through its emergency use authorization (EUA) pathway. On June 11, the agency authorized generic nitenpyram tablets for the treatment of NWS myiasis in eligible dogs, cats, puppies, and kittens.

The over-the-counter product is the first generic animal drug authorized under the FDA's emergency-use pathway and the first OTC treatment authorized for NWS in companion animals. Nitenpyram, best known as the active ingredient in the flea treatment Capstar, kills most screwworm larvae within hours of administration.

However, the FDA emphasized that the product is a treatment, not a preventive. Veterinarians may still need to physically remove remaining larvae and provide wound care following treatment.

To date, no animal drug has received full FDA approval specifically for NWS. Instead, the agency has relied on EUAs, a temporary pathway that allows products to be used before receiving full FDA approval during a declared animal health emergency.

Generic pimobendan launches

Screwworm was not the only drug-related news this week. A generic version of pimobendan, the active ingredient in Vetmedin, has officially launched in the United States.

The chewable tablets are indicated for dogs with congestive heart failure caused by myxomatous mitral valve disease or dilated cardiomyopathy and are the first FDA-approved generic equivalent to Vetmedin available on the veterinary market.

Additional NWS resources and live updates

For veterinarians seeking additional guidance resources, and updates, dvm360's New World screwworm resource center includes treatment options by species, identification and sample-submission guidance, expert interviews, and other educational resources.

dvm360 is also actively tracking confirmed cases, FDA treatment authorizations, government and industry response, and other developments as the situation evolves. Click here for live updates.