2 June 2000

With the consumption of livestock products set to double in the next decade, worms are threatening to decimate the world's sheep flocks. So scientists have gone prospecting for a solution in East Africa.

The Masai sheep herders of East Africa don't know it yet, but they are sitting on a genetic gold mine of benefit to farmers from Romney Marsh to Tasmania, the Welsh hills to the Falkland Islands. Their distinctive pure-bred sheep covered in red hair, a familiar site in the Rift Valley of Kenya, may soon prove to be the most valued rare breed of farm animals in the world.

The "red Masai" sheep, one of the forgotten flocks of Africa, have an unrivalled resistance to the biggest scourge of sheep - the billion-dollar problem of intestinal worms. And geneticists in Kenya believe their resistance lies in a handful of genes that could be transferred into other flocks worldwide. British veterinary scientists are watching their work with anticipation. So should hard-pressed British sheep farmers.

And their story has a wider importance. The red Masai are a potent example of the hidden genetic value locked up in obscure animal breeds round the world, a "barnyard biodiversity" of growing importance as modern methods of fighting animal diseases falter. Saving them will help feed as well as clothe the world.

For 40 years, farmers in rich countries have fought sheep worms with drugs. But, says Leyden Baker of the Nairobi-based International Livestock Research Institute (ILRI), "the resistance of worms to the drugs is growing. We could soon be losing 30 or 40 per cent of wool and meat production because of premature deaths and sickness."

The drugs are the internal counterpart to chemical sheep dip, which attacks infestations in sheep fleece. And, like sheep dip, there are also growing environmental and health concerns because the drugs tend to build up in meat and pastures. For such reasons, ILRI has spent a decade searching for an alternative to the drugs by scouring Africa for native breeds of sheep that show the strongest genetic resistance to the worms. Two years ago, they settled on the red Masai.

"It is a remarkable animal," says Michael Stear of Glasgow University's veterinary school. "The red Masai thrives in conditions that would kill many other sheep breeds." In particular, it shrugs off a virulent African worm called Haemonchus contortus that sucks blood from the gut, leaving other sheep sick and anaemic.

Despite its unique attribute, there hasn't been a rush to add the Masai sheep to flocks round the world because of an equally obvious disadvantage. They grow hair and not wool. So the holy grail is to find the gene or genes that give resistance.

Two years ago, Baker and his team starting buying pure-bred red Masai from markets in the Rift Valley. It took six months to buy 400. Today, more than 1,000 sheep containing varying amounts of red Masai genes graze in the paddocks at ILRI. Baker has crossbred them with South African Dorper sheep that grow white wool in an African climate, but have an especially low resistance to worms.

By juggling the breeding over several generations, tracking which offspring become resistant and which do not, and then analysing their genetic makeup, Baker hopes to pinpoint the genes in the red Masai sheep that control resistance. "By the middle of next year we should be ready to begin the analysis. Within two years we should have preliminary results," he says.

And it could be a lot sooner than that. To speed up the process, ILRI is collaborating with Derek Wakelin at the University of Nottingham to screen mice in the hope of identifying those parts of the mouse genetic makeup that carry genes for resistance to the worms. "We don't know yet if the same genes would do the job in sheep as in mice. But we could get lucky. And the great thing about mice is that you can get results much more quickly," says Baker.

If his luck is in, he could by the end of the year have a hotline to the important sheep genes. He may also be able to draw on help from Europe, where Michael Stear has isolated a couple of genes that give Scottish Blackfaced sheep some resistance to British worms.

Once found, the genes could be inserted into single-cell sheep embryos to start the mass-production of the first worm-resistant woolly sheep. Or the genetic information may be used to develop vaccines against the parasites.

How did the red Masai come by their unique resistance? Clearly long exposure to virulent African worms has helped. But the history of the Masai people might have added a dimension. They came to East Africa from further north about 600 years ago, bringing their sheep with them. The new environment may have set off a rapid phase of natural selection in which only the sheep that could survive the worms prospered and bred, says Baker.

Whatever its origins, their ability to shrug off gut worms could be worth a billion dollars in extra meat and wool from the world's sheep flocks. But this is not simply a case of rich countries mining poor communities for genes. The benefits will flow to farmers from developing countries too, insists Baker. Worms do more damage in Africa than anywhere else because farmers cannot afford the drugs. Sheep farmers in Britain may be facing hard times, but in Africa many go hungry.

Will the Masai be rewarded for preserving an ancient breed until scientists discovered why they needed the breed? Ownership of genetic resources is a hot international issue. The disputes reverberate down the road from ILRI's labs at the headquarters of the UN Environment Programme in Nairobi, which houses the secretariat of the UN's Biodiversity Convention.

"I say it is the Masai people who own those genes - not us or the Kenyan government or the global community," insists Baker, though it is not yet clear whether his bosses agree with him. With an estimated 4,000 breeds of often obscure domesticated animals scattered around the world, the battle over the genes of the red Masai could become the first of many.

Some scientists believe that the world's next agricultural revolution will be in livestock. Consumption of livestock products is expected to double in the next decade, far faster than demand for plant crops. And the focus of that extra production will be in developing countries. But scientists are ill-prepared for the challenge. The Western breeds of cattle and sheep that dominate the world's flocks are often entirely unsuited to life in the tropics. And Western animal breeders have not looked at the potential in traditional African breeds to confer useful genetic traits in animals from both the tropics and cooler climates.

"Although livestock in African environments often appear, through Western eyes, to be malnourished and stunted, and they may lack the genes for high milk or meat production, they are nonetheless exquisitely adapted through natural selection to survive and be productive," Tony Irvin, a former research director at ILRI, told a biotechnology conference in The Hague earlier this year. Examples include the resistance of West African N'dama cattle to the parasite trypanosomiasis, as well as the red Masai's insouciance to intestinal worms.

Irvin believes that "combining the resistance genes of livestock from developing countries with the production genes of developed country livestock could one day provide the optimal animals for both tropical and temperate environments." Just as unregarded old grain varieties have yielded genes that save green-revolution crops of wheat and maize from diseases, so neglected breeds of domesticated animals will confer their genes on the Friesians and Merinos of their livestock counterparts. But that assumes that the traditional breeds are still around.

The barnyard biodiversity produced by 12,000 years of animal breeding by farmers is threatened by the relentless standardisation on a few animal varieties often most suited to temperate conditions and Western farming methods. The UN estimates that 30 per cent of the world's breeds of domesticated animals are threatened. Many may contain unique genes able to benefit the world as the red Masai promises to do.

To help find them before it is too late, ILRI scientists have been drawing up the first maps of the genetic diversity of traditional livestock breeds. These have recently revealed an unexpected biodiversity hotspot among West African humpless cattle such as the N'dama. For historians, says ILRI's Olivier Hanotte, this suggests that the region was an early centre for the domestication of cattle, distinct from the two previously known centres in the Euphrates and Indus valleys. For agricultural scientists, he says, "it means this is a place we should go prospecting for genes".

Humanity took millennia to create the rich genetic wealth tied up in domesticated animals. It is a stunning example of man-made biological diversity, of which the red Masai sheep of East Africa are just one example. But as the modern world loads much of this heritage into the dustbin of history, many believe that only the skills of genetic engineers can salvage the most priceless relics.

Forwarded by: Phelix A.O. Majiwa, Ph.D.
International Livestock Research Institute
Box 30709, Naivasha Road
Nairobi, Kenya
tel -  254-2-630743   fax - 254-2-631499
Via USA tel: 1- 650-833-6660  fax 1-650-833-6661
email: p.majiwa@cgiar.org
http://www.cgiar.org/ilri

ILRI is one of 16 international agricultural research
institutes supported by the Consultative Group on International
Agricultural Research (CGIAR)

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