‘Baa baa’ blood test to save lives in Third World

The newest revolution in microbiology testing walks on four legs and says “baa,” according to Stanford University School of Medicine researchers.

Hair sheep, a less-hirsute version of the familiar woolly barnyard resident, are perfect blood donors for the microbiology tests necessary to diagnose infectious disease in the developing world, according to a new study published July 3.

Microbes from a patient’s urine or sputum are usually identified by growing them in culture dishes filled with gelatinous agar and a small amount of blood. In the developed world, microbiologists use sheep or horse blood. But in many parts of the developing world, horses are prohibitively expensive, and regular sheep, with their constant need for shearing and tendency to get infections, are difficult to keep alive.

Many labs in the developing world use human blood, often donated by lab technicians. But diagnostic tests aren’t standardized for human blood, said Dr. Ellen Yeh, a resident in pathology at Stanford and first author on the paper.

“You don’t get the same test results when you use human blood versus sheep blood,” she said. In addition, the use of human donors increases technicians’ risk of infection with blood-borne diseases, she said.

Ellen Jo Baron, professor of pathology at the medical school and senior author on the paper, first encountered hair sheep in Botswana, Africa. The sheep resist parasites, don’t need to be sheared, and do well in the tropical climates prevalent in much of the developing world. The sheep can also provide milk and meat in addition to their role as blood donors, she said.

Calling in a favor from a colleague with a hobby farm near Walnut Creek, Baron and her colleagues collected blood from hair sheep — the animals are remarkably mellow about the donations, she said — and created test cultures and diagnostic tests.

“It worked for every single thing,” Baron said.

The researchers also found that they could collect the blood in donation bags, much like those human donors might see at the Red Cross, cutting down on cumbersome processing techniques currently used in developing countries.

“It’s very important,” said Bruce Hanna, professor of pathology and microbiology at the New York University School of Medicine, who was not involved in the study. “This paper found an alternative that is able to be produced in Africa and provides identical results to the standardized products that are used in this country.”

The technology will save lives in the tropics at low cost by quickly identifying bacteria to tailor cost-effective antibiotic use — a precious commodity overseas, according to Dr. Michele Barry, senior associate dean for global health at Stanford School of Medicine.

The only hurdle is getting the sheep to labs that need them. Two veterinary labs in Botswana already provide hair sheep blood to local labs based on Baron’s initial results. She is lobbying the charity Heifer International to add hair sheep to its catalogue so microbiologists can donate and send the animals to the developing world.