As concern about New World screwworm grows, the Food and Drug Administration has granted emergency use authorization (EUA) to an anti-parasitic drug to prevent infestations by the parasite in cattle.
The injectable product from Boehringer Ingelheim, IVOMEC, can be administered to calves within 24 hours of birth, at the time of castration, or when a wound appears, according to FDA. Female dairy cattle producing milk for human consumption and calves that will be processed for veal are not eligible for treatment under the EUA.
IVOMEC is a brand name for the drug Ivermectin, which is widely used as an anti-parasitic in cattle, sheep, goats and pets for controlling both internal and external parasites. While it’s not new to the market, the EUA makes it the first over-the-counter option available to preventively treat for the flesh-eating parasite.
The EUA “provides cattle producers and veterinarians with an important preventive tool against New World screwworm,” said Steve Boren, vice president of U.S. livestock at Boehringer Ingelheim. “We appreciate the proactive approach of the FDA and USDA in response to this emerging animal health threat and remain dedicated to supporting veterinarians, producers, and government as we work together to protect cattle herds.”
New World screwworms are a parasitic fly whose larvae feed on the living tissue of warm‑blooded animals and can infiltrate an open wound as small as a tick bite.
Wet, open navels of newborn calves are a major concern, making the ability to preventively treat them a critical tool for ranchers and cattle producers to protect herds.
“Screwworm strikes cattle when they are most vulnerable, including at birth, and demands more labor‑intensive management on the ground," said Dr. Gustavo Sabatini, global technical manager for ruminant parasiticides at Boehringer Ingelheim. He has worked in regions where the parasite is endemic.
"That’s why prevention is essential – not only to protect animal health, but also to safeguard the food supply and the livelihoods of cattle producers.”
Sabatini recently testified before the Texas House Agriculture and Livestock Committee on NWS preparedness alongside federal and state animal health officials and industry groups. Texas Gov. Greg Abbott issued a disaster declaration last week to prevent a New World screwworm infestation.
While New World screwworm has not been detected in the U.S., USDA’s most recent reporting map released Thursday evening shows 4,940 cases detected in Mexico, including 714 cases considered active.
Merck’s Exzolt product received conditional approval from the FDA in December for the prevention and treatment of infestations caused by New World screwworm in beef cattle two months of age and older, as well as replacement dairy heifers less than 20 months of age.
Conditional approval of the topical pour-on product means FDA has determined it is “safe and has a reasonable expectation of effectiveness for its intended use,” and the company has up to five years to generate the additional effectiveness data needed to support a full FDA approval.
The EUA for IVOMEC's use to treat the parasite “will be effective until it is revoked or the [Health and Human Services] Secretary terminates the declaration that the potential public health emergency presented by NWS justifies the emergency use authorization of animal drugs for NWS,” according to the FDA release.
Three total screwworm cases had been detected in the Mexican state of Nuevo Leon – which borders Texas – as of Feb. 3, although none were considered active. There were also 21 total and 7 active cases in the Mexican state of Tamaulipas, according to the USDA tracking page.
Federal and state officials recently stepped up preparedness efforts by convening for a two-part simulation exercise meant to test national readiness for New World screwworm and other threats.
The Department of Homeland Security, Centers for Disease Control and Prevention, Agriculture Department, and Interior Department, along with 80 in-person and 170 virtual attendees, gathered to assess three different scenarios for the spread of pest — cattle smuggling, wild animal infections, or infested humans.
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