Work proceeds on foothill abortion vaccine

Tim Hearden/Capital Press University of California-Davis graduate student Roxann Brooks, center, discusses work on a foothill abortion vaccine as veterinarian Tom Talbot, left, and UC-Davis researcher Jeffrey Stott listen.

Researchers report on progress in fight against disease

By TIM HEARDEN

Capital Press

RED BLUFF, Calif. -- Scientists at the University of California-Davis are closing in on an interim vaccine for foothill abortion, a tick-borne malady that kills calf fetuses.

Researcher Jeffrey Stott of the UC-Davis School of Veterinary Medicine and his assistant, graduate student Roxann Brooks, told ranchers a vaccine could be in the field within the next two years.

"We're moving forward cautiously," Stott said in a presentation to the Tehama County Cattlemen's and CattleWomen's annual dinner here Jan. 8.

Finding an antidote has been elusive in the decades-long fight against foothill abortion, which is caused by bacteria brought on by a tick that bites cows and heifers in dry pastures. The disease causes an annual loss of 45,000 to 90,000 calves, according to UC-Davis researchers.

The bacteria doesn't make the cow sick. But if the animal is pregnant and the fetus has not developed immunity, the bacteria can kill the fetus in 90 to 105 days. There's been no evidence of the bacteria affecting other animals, such as horses or sheep.

Organizations such as the California Cattlemen's Association have held numerous fundraisers for research on foothill abortion, which has decreased reproductive activity and prevented ranchers from bringing cattle into California at certain times of the year.

Tom Talbot, a Bishop, Calif., veterinarian and past CCA president, expressed optimism that an antidote to the disease will be developed soon.

"We think we're getting close," Talbot told the gathering at the Tehama District Fairgrounds.

Some scientists have spent entire careers trying to develop a vaccine for foothill abortion, Stott told the Red Bluff gathering. They identified the tick as the transmitter in the early 1970s, and in the 1990s they isolated the bacteria.

The tick hasn't moved geographically over the years, Stott said. It's hearty, able to survive in extreme cold, and has a life expectancy of 10 to 15 years, he said.

The relatively small area in which the problem exists has discouraged some pharmaceutical companies from throwing money behind the vaccination efforts, Stott said.

However, UC-Davis has begun a licensing application process with the USDA and is talking to companies, he said.

Scientists believed they turned a corner several years ago when they began using mice to grow an organism that could be used as a vaccine, Stott said.

The researchers take cells from infected calf fetuses and insert them into mice, then take the spleens from the mice and use those cells to develop the vaccine, Stott said. It'll take another year of field tests to refine dosage levels, he said.

It could take another three or four years to develop a permanent vaccine, Stott said.

History

The disease's proper term is epizootic bovine abortion, or EBA. It became known as foothill abortion after ranchers in the 1930s and 1940s started sending their 2-year-old pregnant heifers to pasture in the foothills, where the grass was green. When the animals returned to valley pastures and aborted, ranchers started noticing it was the animals sent to the foothills that were affected.

In reality, the tick -- Ornithodorus coriaceus -- is everywhere in the intermountain West where juniper, pine and oak trees grow and it's dry, UC-Davis veterinarian John Maas has said. That includes areas throughout California as well as southeastern Oregon, Southern Idaho and across Nevada.

Online

UC-Davis School of Veterinary Medicine: http://www.vetmed.ucdavis.edu/

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