Looking for clues about disease affecting cattle and people

Clay Caswell (left), assistant professor of bacteriology, seeks to better understand brucellosis with Ph.D. students James Budnick and Lauren Sheehan.

Clay Caswell (left), assistant professor of bacteriology, seeks to better understand brucellosis with Ph.D. students James Budnick and Lauren Sheehan.

A Virginia Tech researcher is hoping to better understand a bacterium responsible for both spontaneous abortions in cattle and an inconsistent and sometimes fatal fever in humans.

Clay Caswell, assistant professor of bacteriology at the Virginia-Maryland College of Veterinary Medicine and an affiliate of the Fralin Life Science Institute, has focused his attention on Brucella. While his colleagues at the veterinary college have spent years developing more-effective vaccines, Caswell is taking a different approach to better understand the molecular basis for Brucella infection.

Brucella lives inside a host immune cell called a ‘macrophage,’ “ said Caswell, who is studying how two small regulatory RNAs allow the bacterium to survive there. “The paradox is that it’s living inside the very cell that’s trying to destroy it.”

Caswell has received funding from the Virginia Agricultural Experiment Station to characterize a novel genetic pathway linked to the bacterium’s virulence. He has also been awarded recent grants from the American Heart Association and the National Institutes of Health to develop the basic science needed to develop treatments in humans who are exposed through unpasteurized milk and other means.

“Brucellosis is the most common zoonosis in the world,” Caswell said. There is no human vaccine for the disease, which infects approximately 500,000 people worldwide every year.

“It is very hard to treat, often requiring two rounds of antibiotics, with a relapse rate of up to 15 percent and the potential for chronic infections. It has a low mortality rate, but when it is fatal, it is often due to a heart infection,” Caswell said.

Other researchers at the veterinary college are developing more-effective brucellosis vaccines for cattle. The U.S. Department of Agriculture granted a provisional license for a vaccine developed by Gerhardt Schurig, professor of immunology and former dean, in 1996 and a full license in 2001. Today, the cattle vaccine developed at the veterinary college is used by farmers and veterinarians worldwide.

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