DATCP Resources on New World Screwworm

Check out these online resources to help stay aware and ahead of New World Screwworm (NWS).

New World Screwworm (Cochliomyia hominivorax/NWS) is a parasitic fly whose larvae feed on living tissue. After being eradicated from the U.S. in 1966, NWS has re‑emerged in Central America and Mexico. According to the U.S. Department of Agriculture (USDA), NWS has been detecte​d in​ the U.S. and in animals near the U.S.-Mexico border. USDA is working with affected states to respond with sterile fly releases, surveillance, and movement controls. At this time, NWS has not been detected in Wisconsin. 

See Links Below:

FDA Issues First Generic Injectable Cattle Dewormer EUA for Prevention of Screwworm

The U.S. Food and Drug Administration (FDA) has issued emergency use authorization (EUA) for the use of Bimectin (Bimeda-manufactured ivermectin) 1% injection products for the prevention of infestations caused by New World screwworm (NWS) in cattle when administered within 24 hours of birth, at the time of castration, or at the appearance of a wound.

“This authorization reflects the FDA’s commitment to expanding generic drug options against New World screwworm,” says Timothy Schell, director of the FDA’s Center for Veterinary Medicine. “By authorizing both generic and pioneer products, the Agency is ensuring producers aren’t dependent on a single manufacturer or product to protect their herds.”

To maintain the continued safety of the food supply and avoid drug residues, it is critical that cattle producers carefully follow the 35-day slaughter withdrawal time and not administer this drug in lactating dairy cows and calves that will be processed for veal.

Based on the totality of the scientific evidence available, the FDA has concluded it is reasonable to believe that Bimectin injection may be effective for the prevention of NWS myiasis in certain cattle when used as authorized, and the known and potential benefits of the product outweigh its known and potential risks.

Bimectin injection is a generic version of Ivomec, which was authorized in February 2026 for the prevention of NWS myiasis in cattle. The FDA previously approved Bimectin injection for the treatment and control of various parasites in cattle. This EUA is only for the Bimectin injection and does not authorize other dosage forms of Bimectin.

Hundreds Of Deer Found Dead In Southeastern Wisconsin Likely Due To Disease Spread 

An outbreak of epizootic hemorrhagic disease, or EHD, has likely spread in recent weeks to include at least three counties in southeastern Wisconsin and killed at least 600 white-tailed deer, according to the Department of Natural Resources.

Initial reports of an unusually high number of dead deer were received in July and were concentrated in Washington County.

The DNR sampled two deer in Washington County, one each in Richfield and West Bend, and received positive results for the virus that causes EHD.

As of mid-August, the DNR had received reports of about 100 dead deer.

By Aug. 31, the number had increased to more than 600 and included reports from Ozaukee and Waukesha counties, said Erin Larson, DNR deer herd health specialist.

What is epizootic hemorrhagic disease?

The disease is spread to deer from the bites of midges, a small insect.

Hemorrhagic disease typically affects deer in the late summer and fall, when the insects are most abundant. The disease kills deer by causing severe internal bleeding, a very high fever and organ damage.

The disease moves fast, and sick deer often die within three to 36 hours after symptoms show up, according to the Ohio Department of Natural Resources.

Due to the fever symptoms, deer affected by EHD often seek water in an attempt to cool.

What’s Happening with PRRS Right Now? 

Porcine reproductive and respiratory syndrome (PRRS) is not like other viruses. Despite decades of research and advanced biosecurity measures, the battle still wages on. In recent weeks, the PRRS incidence has increased and is higher than in previous years, says Dr. Gustavo Silva, DVM and associate professor of vet diagnostic and production animal medicine at the Iowa State University College of Veterinary Medicine.

The current rise is primarily driven by growing herds while breeding herds remain relatively low, he told the crowd at the Annual Swine Conference in Quincy, Ill.

“New variants move fast – and reach good farms, too,” Silva says.

Gone are the days of thinking you are “safe” from PRRS. New variants popping up unexpectedly in previously healthy hog regions of the country are challenging the pork industry to think differently.

“The virus is changing so we need to change how we deal with it,” Silva says. “How can we better use tools available today to make this battle a little more fair?”

Why is PRRS Trickier Than Ever?

PRRS is harder to control than other viruses. Not only does it rapidly evolve and have a high strain diversity, it can also move through multiple transmission routes from direct contact and aerosols to fomites and movement. It persists in pigs and survives longer in the cold than other viruses, Silva says.

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