Sheep Industry News March 2025

ANIMAL HEALTH Continued from Page 17

Currently, 47 of 50 states are free of classical scrapie for greater than seven years, and in 2028, all states will have been scrapie free for seven years. Dr. David Schneider, Ph.D., of the USDA/Agricultural Research Service’s Animal Disease Research Unit in Pullman, Wash., pro vided an update to ongoing research on prion diseases in animals. These diseases include chronic wasting disease, scrapie and other transmissible spongiform encephalopathies. Chronic wasting disease was first reported in captive mule deer in 1967 in the Intermountain West, but in the 1980s was detected in free-ranging deer near the captive facility. Today CWD is found in 35 states and four provinces, with most cases in free-ranging white tailed deer, mule deer and elk. Since elk and deer are the natural hosts for CWD, Schneider’s lab administered an experimental transmission to domestic sheep by conducting an intracranial inoculation from CWD-infected cervids. The results were all positive for the disease, indicating that while using unnatural routes and big doses, sheep can be experi mentally susceptible to CWD prions. But would existing testing techniques be able to tell the dif ference between scrapie and CWD? To find out, this elk-origin CWD passed into the brain of sheep was then passed into mice. In one study, the CWD-positive sheep did not cause disease in these “ovinized” mice after an incubation of more than 600 days. Importantly, the mouse bioassay could differentiate between elk-origin CWD and the sheep-scrapie prion, but the initial tests took years to get results. Further refinement of the assay using dif ferent substrates has narrowed that time down to about a week, and further research offers promise to narrowing the time to a matter of hours. FUTURE Rosie Busch, DVM, of the University of California-Davis gave an update on the alphabet-soup of federal agencies working in veteri nary medicine. While noting that the likelihood of new antipara sitic drugs for sheep and goats in the United States is low, there is a push for approval of new antiparasitic drugs for small ruminants. The Food and Drug Administration has indicated that com panies may be able to use published literature and foreign data to satisfy some of the requirements for licensing of certain drugs in the United States, so this may be a pathway for additional small ruminant drugs to be used in this country. Animal Health Committee Co-Chair Jim Logan, DVM, con cluded the session by warning sheep producers that in light of the threats posed by foreign animal diseases, New World Screwworm, and bird flu, “If it’s something you haven’t seen before, it’s impor tant that you contact a veterinarian.” Logan advised producers not to intermingle backyard poultry with sheep and goats, and to keep their waterers separate. He noted that there is a zoonotic component of bird flu, which has also been detected in a lot of wildlife species.

ity, and sheep and goat vaccines. This program has five projects that target sheep and goat vaccine development, as well as outreach and education on emergency re sponse plans, foreign animal disease management and reporting. In addition, substantial investment is occurring in projects to enhance Foot-and-Mouth Disease preparedness across multiple species. SCRAPIE Detwiler noted that the United States has spent about 40 years working toward the elimination of scrapie – a disease caused by a misfolded protein called a prion. This fatal brain disease has an estimated annual cost to the nation’s sheep industry exceeding $10 million, but fortunately hasn’t been detected in the United States since 2021. With no vaccine and no treatment, the prion can survive in the environment for at least a couple of years. Infectivity occurs “in everything but the baa,” Detwiler said, since it has been detected in milk, blood, placenta, lymph nodes and the brain and spinal cords of infected sheep. Scrapie is an infectious disease with a genetic in fluence, with some sheep having a genetic susceptibility to scrapie, becoming infective after exposure to the prion. The scrapie eradica tion program has culled infected animals and selected for scrapie resistant sheep genotypes. COMPLETELY UPDATED Sheep Production Handbook Fully Searchable USB

Volume 8 Features New Chapter on Lamb Quality Updated Material in Every Chapter, including:

Only $19.95

Breeding & Selection • Dairy Sheep • Forages Health • Reproduction • Management • Wool Nutrition • Marketing • Predator Damage Control

Order at SheepUSA.org/shop

30 • Sheep Industry News • sheepusa.org