A chance discovery in Kenya could give relief to millions of farmers who have been losing their cattle to East Coast fever.
Researchers at International Livestock Research Institute (ILRI) in Kenya and Roslin Institute at the University of Edinburgh in Scotland have identified a genetic marker that predicts whether an individual cow is likely to survive infection with East Coast fever.
In its findings published last week in PLOS Genetics, the team says the allele (the variant of a given gene) they identified is not necessarily the specific gene that limits the growth of the animal’s cells when they are infected by the parasite, protecting them from the illness.
“For breeding, it doesn’t actually matter,” says Roslin’s David Wragg.
“You just need a way of saying, ‘This animal is a good one to breed from’, because its offspring are likely to survive the disease.”
"Tests showed the marker does this very well, with only one out of 20 animals with two copies of the allele succumbing to the disease.”
The scientists said further research to pin down the exact gene(s) responsible and their mechanism of action will enable scientists to edit the DNA of cattle to make them disease tolerant.
This new information presents an opportunity to craft breeding programmes that could develop cattle strains with resilience against the disease.
Even though a vaccine for East Coast fever exists and usually gives cattle lifelong immunity, making it is a “complex affair” that involves making a kind of ‘tick smoothie’ by crushing up hundreds of thousands of infected ticks in an industrial blender, which is time-consuming, is expensive costing up to 20 times more than other common livestock vaccines and can cause disease if mishandled.
“There are a lot of manufacturing and distribution issues associated with this vaccine. It is a difficult vaccine to produce, it is difficult and expensive to store and to deliver. And it must be administered by a skilled person,” Vish Nene, co-leader of the ILRI Animal and Human Health Programme said.
The other option is regularly dipping animals in acaricides — pesticides that kill ticks — but this is also labour-intensive, polluting.
“We are struggling to control this disease,” says Phil Toye, principal scientist in animal health at ILRI.
“If the cattle are susceptible, without treatment you can lose 100 percent of your herd in two or three weeks.”