A cattle vaccine, genetically engineered by a UC Davis veterinarian to combat a deadly viral disease, has just been approved for widespread use throughout Africa, bringing long-awaited relief to millions of impoverished herders and to the fragile African economy.As a child, Ethiopian-born virologist Tilahun Yilma learned how the disease "rinderpest" entered Ethiopia in 1888, killing 90 percent of the cattle and leaving more than 30 percent of the population to starve to death.Frustrated by the inability of existing vaccines to halt the disease that continues to plague Africa and Asia, Yilma, a professor in the UC Davis School of Veterinary Medicine, resolved to develop a better vaccine.Yilma plucked two genes from the rinderpest virus and nestled them in the vaccinia virus, the same virus used to make the smallpox vaccine. The genetically engineered vaccine, which doesn't require refrigeration, is scratched onto an animal's neck or abdomen, producing sufficient immune response to ward off the rinderpest virus. The herder later can simply peel the scab off of the immunization site, grind it up in saline solution and have 250,000 additional doses for future vaccinations.Although Yilma first developed the vaccine nearly a decade ago, scientific and political concerns about releasing a genetically engineered vaccine into the wild delayed approval for its widespread use until just recently.Yilma hopes the rinderpest vaccine will increase the food supply for subsistence level African herders and eventually enable countries with rinderpest to sell their livestock on the world market. He continues related research aimed at developing a vaccine for the virus that causes AIDS in humans.