LUSH green pastures stretch for miles around David Kinyanjui Njuguna’s compound near Muguga, just west of Nairobi. But his two cows are confined to a small mud-floored pen behind his house. Like many farmers across Kenya, Njuguna is reluctant to let his cattle graze freely for fear that they will be bitten by a brown ear tick (Rhipicephalus appendiculatus) lurking in the grass.
Such bites are likely to be lethal. The tick carries a parasite called Theileria parva, which causes East Coast fever (ECF), a devastating disease that kills more than a million cattle a year across eastern and southern Africa, and cuts the milk yield of millions more. Economic losses total more than $165 million a year. And Kenya, because of its climate and farming practices, is the hardest hit.
Now its veterinary researchers are hitting back with a major campaign to protect livestock against ECF. They have opted for an unusual – and risky -form of immunisation. In selected parts of the country, vets are infecting cattle with live, virulent T. parva while at the same time injecting the animals with antibiotics to keep the deadly parasite at bay.
Similar “infection and treatment” campaigns have been waged against animal diseases in the past. Early this century, for example, vets would immunise cattle against rinderpest by exposing them to the virus and giving them serum from an animal that had recovered from the infection. But today, ECF is the only animal disease being tackled in such a dangerous fashion. It has some serious drawbacks. All immunised cattle become carriers of the disease for life. And unless further measures are taken to protect the treated animals, the procedure can kill 1 in 20…
