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African farmers to benefit from genes resistant to cattle 'sleeping sickness'

By Martin Leggett - 16 May 2011 19:0:0 GMT
African farmers to benefit from genes resistant to cattle 'sleeping sickness'

A study pooling the resources of the International Livestock Research Institute (based in Kenya) and scientists from the Universities of Liverpool, Manchester and Edinburgh (all in the UK) is shining a light - at the end of a very long tunnel - for Africa's livestock farmers.

Across a huge tract of Africa, domesticated cattle are plagued by the trypanosome parasite. These tiny boring  protozoa are carried by the tsete fly, crippling infected animals - and so hobbling the efforts of livestock farmers to pull themselves out of poverty. But this study - published today in the Proceedings of the National Academy of Sciences - claims to have achieved a breakthrough in tacking those burdens, with the discovery of two specific genes which may offer protection from the parasite.

The cattle that are are prone to the trypanosome parasite are the Boran cattle breed - the most widely reared livestock in a large part of Africa. Farmers rely on them for food, milk and plowing, in an area stretching from Senegal across to Tanzania, and from Chad all the way down to Zimbabwe. They are distinctively humped, and prized for their large size and productivity. In contrast, a hump-less West African cattle breed, the N'Dama, are smaller, produce less milk, and a little more flighty than their bigger Boran cousins. But they are resistant to trypanosome.

In an ideal world, the cattle that sub-Saharan African farmers uses would combine the 'best of both worlds' - the productivity of the Boran, and the disease-resistance of the N'Dama. And that is the goal the team's research may enable through their new paper, by isolating the genes responsible for resistance the cattle equivalent of 'sleeping sickness.' With these genes documented, a new hybrid cattle breed could be readied within 5 to 10 years. Senior author Steve Kemp said ''The two genes discovered in this research could provide a way for cattle breeders to identify the animals that are best at resisting disease when infected with the causative trypanosome parasites.''

But pinpointing those genes was far from simple. The team had to pull in research looking at the trypanosome parasite problem from several different angles - and then to crunch the numbers from those studies via massive data-trawling programs. ''This may be the first example of scientists bringing together different ways of getting to the bottom of the genetics of a very complex trait,'' said Kemp. ''Combined, the data were like a Venn diagram overlaying different sets of evidence. It was the overlap that interested us.''

A separate strand of their research has now confirmed that the genes they identified were most likely evolved in the older N'Dama cattle in response to trypanosome. The next step will be to bread a small herd of disease-resistant cattle. From that small genetic pool, the rolling out the improved cattle across the continent would be a decades-long process - but one of immense benefit to the rural livelihoods in Africa. With millions of lives in the balance, on a  continent seeking transformation, as Kemp says ''it's time we got started.''