What is in this article?:
- Ethiopian in exile seeks to vanquish cattle plague
- Powerful new vaccine
- The deadly rinderpest disease brought a young Tilahun Yilma to UC Davis in 1965 as an undergraduate student, intent on becoming a veterinarian and returning to Ethiopia to combat the disease.
Friends and colleagues call him “Yilma.” It was his father’s name and means to germinate and grow.
Tilahun, his first name, means to be an umbrella, provide refuge.
Since his birth, it seems, his life has been woven with the warp and weft of ambition and benevolence, fitting for a man who is both scientist and politician, high-achiever and generous benefactor, American and Ethiopian.
And somehow, threaded throughout the tapestry, has been a deadly cattle disease called rinderpest. Virtually unheard of these days in the Western world, it is the source of great suffering and poverty in the fragile developing nations of Africa and Asia.
Yilma, now a professor and microbiologist in the UC Davis School of Veterinary Medicine, first learned of rinderpest from his grandmother who spoke of “Yekebit Elkkit,” the Year of the Annihilation of Cattle. It was in that year, 1888, that Italian troops invading Ethiopia introduced the deadly virus to Africa.
Carried by just three infected cows, rinderpest — meaning cattle plague in German — spread from Ethiopia’s west coast across the Sahel Desert, killing in one year 90 percent of the country’s domesticated cattle, plus countless wild buffalo, giraffe and antelope. An estimated 30 percent 60 percent of Ethiopia’s human population starved to death that year.
Decades later it was rinderpest that brought a young Yilma to UC Davis in 1965 as an undergraduate student, intent on becoming a veterinarian and returning to Ethiopia to combat the disease.
In 1970, with D.V.M. in hand, Yilma joined the international effort to vaccinate Africa’s nomadic herds against rinderpest. For two years, he and colleagues trekked the isolated trails of the nomadic herders along the Ethiopia-Somalia border. The vaccine they administered was effective but impractical for Africa’s rugged conditions. Unstable in the extreme heat, it had to be refrigerated and required syringes, needles and a veterinarian.
More than 125 million cattle were vaccinated during that campaign, and it appeared that rinderpest had been eradicated from Africa. But in 1980 the disease surfaced again in Nigeria, sweeping back across the Sahel all the way to the Red Sea. By then Ethiopia and Somalia were embroiled in warfare, preventing vaccination of livestock to halt the disease.
This time, rinderpest killed an estimated $400 million worth of cattle and caused more than $2 billion in related losses that sapped Africa’s already frail economy. The nomadic herders lost their food supply, and the rinderpest-infected countries were forbidden to sell cattle on the international market.
Despite the failure of the first rinderpest vaccination campaign, Yilma was still intent on conquering the disease when he returned to UC Davis in 1986 as a professor of virology. Intrigued by the potential of the new recombinant DNA technologies, he was convinced that he could develop a rinderpest vaccine for Africa and Asia — one that was simple and inexpensive to produce, easy to administer and would not require refrigeration.
In 1988, after just one year’s work, he announced in the journal Science development of a new genetically engineered vaccine for rinderpest. Although produced through recombinant DNA technology, the vaccine was elegantly simple.
Yilma had identified proteins on the surface of the rinderpest virus that cause an immune response in cattle. He selected the genes that code for two of those proteins, which allow the virus to attach to the cow’s cells and spread from cell to cell. He then plucked those two genes out of the rinderpest virus and nestled them in a weakened form of the vaccinia virus, used earlier to make the smallpox vaccine. This genetically engineered vaccine stimulates the cow’s body to launch an immune response to rinderpest without actually infecting the animal with the disease. If the animal is later exposed to rinderpest, it is already equipped with the antibodies needed to quickly fight off the disease.