A genetic discovery could help fight an African cattle disease

IT BEGINS WITHECFECF a bite near the cow’s ear. In the next few days, the animal’s lymphocytes multiply. Its lymph nodes swell. It stops feeding and starts coughing as fluid fills its lungs. It develops a fever as high as 41°C. A few weeks after the bite, it dies.Such a story is common in African countries where East Coast Fever () is rampant. , which is caused by protozoan parasites spread by ticks, kills around 1m cattle a year. It also prevents the introduction of faster-growing, higher-yielding European breeds, which are much more susceptible to the illness than their African kin. Though a vaccine is available, and the ticks can be attacked with sprayed pesticides (see picture), both of these approaches are costly. Most farmers thus continue to use less-productive local varieties—curtailing their incomes and reducing agricultural output. The difference is stark: a Kenyan cow produces around a tenth as much milk as one in Britain.