Veterinary prof to lead wild sheep research endowment

PULLMAN, Wash. – Washington State University veterinary professor Thomas Besser has been named the Rocky Crate D.V.M. and Wild Sheep Foundation Endowed Chair in Wild Sheep Disease Research.

Besser succeeds Professor Subramaniam Srikumaran who held this position since its beginning in 2004 and is transitioning to retirement. The endowment was the first endowed chair in the WSU College of Veterinary Medicine.

“The Wild Sheep Foundation is pleased to continue our 23-year collaboration with Washington State University,” stated WSF Conservation Director Kevin Hurley.”

“I am honored to be appointed to Dr. Crate’s chair,” said Besser.  “Pneumonia is a very nasty disease that has severely limited the recovery of bighorn sheep in the western U.S. We’ve learned a lot about the disease in the past few years, and I am looking forward to trying new approaches to preventing the disease in bighorn herds that haven’t yet been affected, and in limiting the damage in herds that have. We are getting ready to start clinical trials that may lead to effective, manageable approaches for all parties, including domestic sheep producers.”

Tom Besser
Tom Besser

Besser knows the world of cattle and sheep diseases well. His training began in 1981 when he came to WSU as a food animal medicine and surgery intern. He completed a residency and joined the food animal faculty in 1986, then moved to the Washington Animal Disease Diagnostic Laboratory in 1990. His work on the bighorn sheep pneumonia problem ranges from basic investigations of the infectious process and immunity, to development of practical approaches to management of both domestic sheep and bighorn sheep to alleviate the disease.

“For decades, people smarter than I pursued a vaccine for controlling organisms that seemingly cause a fatal pneumonia in wild sheep with little success,” he said. “It now appears that for a long list of reasons, a vaccine strategy for wild sheep is not the best way to control the agent that starts the disease process, a bacteria named Mycoplasma ovipneumoniae. We call this bacterium, ‘Movi’ [pronounced em-OH-vee] for short.”

The bacterium is found in domestic sheep and goats, where it causes relatively mild disease, but when it is transmitted to bighorn sheep – which can occur whenever they come into contact, on public rangelands or private lands – the bighorn sheep may develop a severe, often fatal pneumonia that can decimate 80 percent of some herds.

“In just the last five years, we’ve come to understand this complex disease process much better, and now I think we are now at the point where we can begin to try out some possible solutions. That progress is specifically why I took this position now instead of retiring this year.”

Besser explained that Movi  is found in most domestic sheep flocks and causes few problems there, except in weaned lambs which can develop a similar, but much milder, pneumonia.

Experiments have shown that contacts between domestic sheep carrying Movi and bighorn sheep nearly always result in fatal bighorn sheep pneumonia. However, similar contacts with domestic sheep that don’t carry Movi do not trigger epidemic pneumonia. So part of his research plan is to develop efficient ways to eliminate Movi from domestic sheep flocks, in order to greatly reduce or eliminate the risk of pneumonia if contact with bighorn sheep occurs.

“This year, we are working with the University of Idaho Sheep Center to see if we can eliminate Movi from part of their domestic sheep flock. As long as domestic sheep carry Movi, they represent a significant risk to bighorn sheep they might contact, so it would be a great help if domestic sheep flocks near bighorn ranges would work to eliminate Movi from their animals.

“I am also working with wildlife agency biologists and veterinarians to try to eliminate the carriers of Movi from affected wild sheep populations, to stop the on-going pneumonia losses they often experience.”

Privately funded, the Rocky Crate chair position is dedicated exclusively to research on wild sheep diseases and graduate education. Investment of additional Crate funds provides permanent funding for the program chair’s research activities.

“It is also important to recognize that the Wild Sheep Foundation and state chapters of the organization that have also been generous annual contributors to this disease research,” explained Besser.

Crate was a 1969 WSU veterinary alumnus, avid big game hunter and Wild Sheep Foundation member. In 1998, Crate donated more than $1.5 million from his estate to the university and the Foundation before his death due to cancer.

The WSU Department of Veterinary Microbiology and Pathology is internationally recognized as a leader in bighorn sheep disease research.

Wild sheep hunters and FWS are the world’s most generous contributors to wildlife conservation. Their mission is to increase healthy populations of indigenous wild sheep, to safeguard against their decline or extinction, and to fund programs for professional management of these populations.




Charlie Powell, Public Information Officer, call or text (509) 595-2017 or

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