1. Avian flu detected in Idaho dairy cows as study explores role of virus RNA detection in bovine semen
By Stephanie Soucheray, MA
CIDRAP News
April 16, 2026
APHIS reported new detections of H5N1 avian flu, with positive tests revealing the virus in five Idaho dairy herds.
The milking cows were the first avian flu detections in cattle since a Wisconsin report in December 2025. The new detection comes almost exactly two years since US officials first recorded avian influenza in dairy cattle.
RNA detected in bull semen
In related news in Emerging Infectious Diseases, researchers examined bovine semen to determine if shedding of the virus in semen could result in silent viral spread within herds and across geographic regions through artificial insemination.
The study, published yesterday, was based on observations of natural breeding bulls on an H5N1-affected dairy farm in California, and was inconclusive in determining if semen was a good conduit for the virus, with limited evidence of seroconversion. The investigators found the RNA (genetic material) of highly pathogenic avian influenza (HPAI) H5N1 virus but not live virus in semen from a bull that was displaying no flu symptoms.
"Further research and risk assessments are needed to determine tissue tropism of HPAI H5N1 in reproductive organs and whether naturally infected bulls shed virus in semen, and, if so, evaluate the risk for disease spread on dairy farms and with artificial insemination programs," the authors wrote.
APHIS reported 3 commercial outbreaks this week
In other avian flu news, APHIS reported outbreaks on three commercial poultry operations this week, including two in South Dakota and one in Arkansas. In Charles Mix and Edmunds counties in South Dakota, commercial turkey facilities reported outbreaks affecting 46,300 and 13,800 birds, respectively. And in Clay County, Arkansas, a large outbreak affected 191,200 birds at a commercial broiler production.
In the past 30 days, there have been 41 confirmed avian flu outbreaks including 27 commercial flocks and 14 backyard flocks, affecting 1.6 million birds.
2. One Horse Euthanized, 55 Quarantined After EHM Reported At HITS Culpeper [VA]
By Melissa Wright
EDCC Health Watch
Chronicle of the Horse
April 18, 2026
One horse was euthanized Friday after developing clinical symptoms of equine herpesvirus myeloencephalopathy, the neurological form of equine herpesvirus-1, during a hunter/jumper show at Commonwealth Park in Culpeper, Virginia.
The horse, a 21-year-old Thoroughbred gelding, had been stabled in Barn 5 for the HITS Culpeper Commonwealth National Horse Show that began Wednesday. The barn, with 42 other horses in it, has now been quarantined by the Virginia state veterinarian. The euthanized horse's home barn in Loudoun County, Virginia, with 13 horses in it, has also been quarantined by the state vet.
"The gelding displayed clinical signs including lethargy, distal limb edema, and acute onset ataxia," according to an outbreak alert posted Friday on the national Equine Disease Communication Center website. "He was evaluated at HITS Culpeper by the referring veterinarian and was referred to an equine hospital. The horse was recumbent on arrival and was admitted directly to the isolation unit by dedicated personnel. The horse was subsequently euthanized."
A second horse in the quarantine area has tested negative for EHV-1 on the first of two tests administered, according to a statement issued Saturday by HITS Horse Shows.
3. How poultry producers can combat insecticide resistance
Producers who treat resistance management as a proactive strategy can maintain more effective control over time.
By Meredith Dawson
WATTagnet.com
April 16, 2026
Poultry producers who build rotation and resistance monitoring into their pest programs are better positioned to maintain control as pests continue to adapt to insecticides.
Resistance develops when insects are repeatedly exposed to the same active ingredients, explained MGK Technical Services Support Specialist Anna Hansen during the PEAK 2026 conference in Minneapolis, Minnesota, on April 14-16.
Insecticides are classified by mode of action and assigned group numbers printed on product labels. Rotating between group numbers, and not just between branded products, is the critical distinction producers need to understand, she continued.
For example, an effective rotation program moves between distinct chemical classes, such as pyrethroids (Group 3A) and neonicotinoids (Group 4A). Additionally, switching classes at least once a year is recommended.
Vasquez presses USDA for screwworm preparedness update [edited]
Letter to Rollins presses for answers on strategy to combat economic strain on ranchers and rising beef prices as summer outbreak season approaches.
Beef Magazine
April 16, 2026
On April 13, Rep. Gabe Vasquez (D-N.M.) sent a letter to Agriculture Secretary Brooke Rollins demanding answers on the Administration's preparedness strategy for a New World screwworm (NWS) outbreak as the warmer months approach. The letter also requested an update on the status of the sterile fly dispersal and production facilities in Texas. He was joined on the letter by six other members on the House Agriculture Committee.
"When extreme weather and disease shrink our U.S. cattle herds, ranchers struggle, and American consumers feel the pain at the grocery store with rising beef prices," said Vasquez. "Instead of undermining U.S. ranchers by importing foreign beef from Argentina, the USDA should be focused on doing everything it can to improve, strengthen and protect our domestic cattle herds - including taking steps to prevent outbreaks of the New World screwworm. It is critical that the Administration continue to work with Congress and industry to ensure that everyone is on the same page to effectively mitigate any widespread outbreak of NWS in the U.S. before it devastates American ranchers."
The letter requests a commitment from USDA to continue using sound science and research to inform any decisions on opening the border to cattle trade, information on how NWS prevention funds will be spent and an update on the operating status of technology aimed at limiting NWS outbreaks.
Full text: https://www.beefmagazine.com/policy/vasquez-presses-usda-for-screwworm-preparedness-update
USDA and U.S. Army Corps of Engineers Break Ground on New Texas Sterile Fly Production Facility [edited]
USDA Office of Communications Bulletin
April 17, 2026
Edinburg, TX - Today, U.S. Secretary of Agriculture Brooke L. Rollins and Lieutenant General William H. "Butch" Graham, U.S. Army Corps of Engineers (USACE) commanding general, led the groundbreaking for the new sterile fly production facility at Moore Air Base in Edinburg, Texas. USDA is partnering with USACE to construct this facility, which is a cornerstone of Secretary Rollins' five-pronged strategy (PDF, 1005 KB) to combat New World Screwworm (NWS), expanding the nation's domestic capacity to protect livestock, wildlife, and public health from this serious pest.
"Breaking ground on this facility marks a major investment in safeguarding America's livestock and the producers who feed this nation. This puts NWS sterile fly production in American hands, so we do not have to rely on other countries for the best offensive measure to push screwworm away from our borders," said Secretary Rollins. "The New World Screwworm threatens the health of our herds, the stability of rural economies, and the resilience of our supply chain. President Trump and his entire cabinet is committed to leveraging every resource necessary to contain this pest, protect American agriculture, and ensure the long-term security of our food supply chain."
The new facility is being built with an aggressive timeline designed to quickly expand the nation's sterile fly production capacity:
Initial operational capability targeted for November 2027, reaching production of 100 million sterile flies per week.
Construction continues immediately beyond initial operations to scale full production capacity to 300 million sterile flies per week.
USDA and USACE have slashed red tape, securing expedited procurement, and eliminating other barriers.
Together, USDA and USACE will oversee installation, and commissioning of specialized systems that will make this facility operable on time, delivering the critical sterile flies
we need to continue to defeat this pest.
Full text: https://content.govdelivery.com/accounts/USDAOC/bulletins/4136b7b
5. Emerging in Alaska, dominant H5N1 strain spread continent-wide through migratory birds
By St. Jude Children's Research Hospital
Edited by Gaby Clark, reviewed by Andrew Zinin
Phys.org
April 15, 2026
An international group of scientists mapped the spread of the current dominant strain of highly pathogenic avian influenza virus through North American bird populations in 2024. Led by scientists from St. Jude Children's Research Hospital, the collaboration provides a comprehensive view of this novel flu spreading through birds in North America. The investigators collected and sequenced samples from birds across the continent, letting them map the virus's spread. They also compared the virus from birds to those causing human infections, showing that current human vaccine stockpiles will likely work well against both. Closer evaluation of the viruses led the researchers to classify them as low risk for human-to-human spread in their current form. The study was published today in Nature Medicine. [See: https://www.nature.com/articles/s41591-026-04300-1 ]
A highly pathogenic H5N1 avian influenza virus entered North America in 2021, causing havoc in wild birds and the poultry industry. Since then, researchers across the continent have continued to test wild populations of waterfowl, such as ducks and geese (influenza's natural hosts), for any changes in the virus. In late 2024, the St. Jude group detected D1.1, a novel strain which became dominant in several sites. They coordinated with multiple institutions across Canada and the United States to map the strain's geographic penetration. The researchers observed that the strain first appeared in Alaska and British Columbia, then moved south and east via known migratory pathways.
"Combining information collected from multiple partners, we've documented the entire continental spread of a newly dominant strain of highly pathogenic avian influenza virus through wild bird populations," said corresponding author Richard Webby, Ph.D., St. Jude Department of Host-Microbe Interactions. "We've shown the value of connecting what are usually regional findings into a single comprehensive map to understand the strain's spread."
Full text: https://phys.org/news/2026-04-emerging-alaska-dominant-h5n1-strain.html
6. Four animal drugs cleared to fight New World screwworm
By AGDAILY Reporters
AgDaily.com
April 17, 2026
The U.S. Food and Drug Administration has issued emergency use authorizations for four animal drugs aimed at preventing and treating New World screwworm, a parasitic threat that can cause severe and often fatal tissue damage in livestock and other animals.
The authorizations include three products from Boehringer Ingelheim Animal Health USA: Ivomec (ivermectin), NexGard (afoxolaner), and NexGard Combo, along with an antiseptic wound spray with insecticide from Health and Hygiene Ltd.
These products are authorized for use across a wide range of species. In addition to cattle, treatments may be used in dogs and cats, as well as horses, sheep, goats, deer, birds, and even certain exotic and zoo animals, depending on the product.
The move follows a 2025 determination by the U.S. Department of Health and Human Services that New World screwworm presents "a significant potential for a public health emergency" with implications for national security and animal health.
Full text: https://www.agdaily.com/livestock/emergency-approval-expands-options-fight-screwworm-infestations/