By Kerin Clark, Wyoming Farm Bureau Federation (Written May 2009)

Former Wyoming State Veterinarian Dr. Walt Cook spoke about animal diseases at the May 29th Wyoming Farm Bureau Foundation Symposium.  Dr. Cook did speak about brucellosis, a topic that takes the forefront of most animal disease discussions, but he also explained some of the other animal diseases of concern in Wyoming.


“We are seeing a resurgence in many states,” Dr. Walt Cook said.  “It was considered almost eradicated ten years ago.  In the state veterinarian’s office, it is one of the diseases I worry most about.”

Cook explained that the number of infected animals in large herds is often very low.  “We are starting to be concerned about reverse zoonosis (humans giving it to cattle),” He continued.  “That is why they think it is low numbers because it is more human to cattle transmission.”

“Believe me tuberculosis restrictions are much worse than brucellosis,” Cook continued.  “Cattle would have to be tested two weeks ahead of time before transportation.”

The Wyoming Livestock Board instituted an order requiring testing of rodeo cattle.  The rule says the animals must be tuberculosis tested within last 12 months; there are exceptions if less than two months of age they don’t need to be tested or if direct from herd of origin and no contact with rodeo or dairy animals.


Trichomoniasis is a venereal disease of cattle causing early fetal death and infertility resulting in extended calving seasons.  The disease is carried by infected bulls.  According to Dr. Cook, trichomoniasis is a hard disease to catch.  “Treatments are unreliable and vaccines are not effective,” Cook explained.

We have a new PCR test so the new rules allow single PCR if entire bull herd is tested “Trich is a huge disease in Wyoming,” Cook stated.  “It seems like we are seeing it more and more."


Scrapie is a fatal neurologic disease of sheep and goats. According to Dr. Cook, scrapie is more commonly found in black faced sheep. Imported black-faced sheep have a genetic susceptibility testing requirement.

“Wyoming identified a case of scrapie from Oklahoma thus preventing a Wyoming outbreak so the WLSB kept the testing rule in place,” Cook stated.

Cook outlined the Scrapie programs available.  They are:  1) Genetic susceptibility screening, 2) Incentive to replace susceptible with resistant rams, 3) Genetic susceptibility screening for seed stock/ram sales, 4) Testing imported black-faced sheep.

“We are also hoping to get approval to do a large tag retention study,” Dr. Cook stated. “Those scrapie tags do not stay in place long.”


Bluetongue is an infectious, non-contagious insect borne disease of domestic and wild ruminants, including sheep.  Death occurs in 2-30% of those infected.

“Wyoming had an outbreak in September 2007,” Dr. Cook explained.  “Most flocks had low numbers of infections, but a few flocks lost 10-30% with many more sheep sick.”

“Options are limited with bluetongue control,” He continued.  “We cannot get a vaccine into Wyoming right now.  There is a vaccine in California, but the paperwork is so onerous to bring into Wyoming that the California Wool Growers won’t do it for the market out here.”

According to Dr. Cook, Wyoming will have to concentrate on vector control.

Equine Viral Arteritis

“This disease came into Wyoming a couple of years ago,” Dr. Cook explained.  “It is mainly known for causing abortion.  Foals can be infected before birth and the disease is transmitted through respiratory, venereal, congenital or indirect routes.”

It is a live horse and semen issue.  The Wyoming Livestock Board has no specific rules, but recommends you use the vaccine appropriately and control with breeding management.

Contagious Equine Metritis

Contagious Equine Metritis (CEM) is an acute, highly contagious venereal disease in horses.  It is not found much in the United States and is considered a foreign animal disease.

“There is not a good vaccine out there so we are much more worried about this disease,” Dr. Cook explained.  “Transmission is through sexual contact, AI or fomites.”

“The biggest issue with CEM is diagnosis is extremely involved, expensive and labor intensive,” He continued.  “You test the stallion, then he breeds two mares, then test the mares and stallion again.  It is a several month long process.”

According to Dr. Cook, Wyoming has a single potentially exposed stud undergoing testing.  Nationwide there are 21 positive studs, five positive mares and 913 additional exposed horses.  Control methods involve identification of carriers with treatment and/or removal from the breeding program.

“We appreciate Dr. Cook joining us at the Symposium,” Ken Hamilton, WyFB executive vice president said.  “What a great opportunity livestock producers had to visit one-on-one with him about animal health in the state of Wyoming.”