Cattle plague: A killer in the fold

30 April 2005

  • First published in The New Scientist Print Edition. Subscribe and get 4 free issues.
  • Thembi Mutch

 

 

Inguni Cow - stock photo

 

DON’T say there’s rinderpest in Somalia,” says Tim Leyland. “You’ll have armed gangs of Somali warlords turning up at your door.” He’s only half joking. As a rinderpest expert with the African Union in Nairobi, Kenya, he is all too aware of local sensitivities. Just talking about the disease makes many Somalis uncomfortable, because the repercussions for trade are so serious. It’s not easy doing scientific research on a deadly cattle plague when some of the major stakeholders are armed warlords who own thousands of cows.

But there’s no getting away from the fact that, if rinderpest remains anywhere on the planet, it is in Somalia. A global eradication campaign, waged for more than 50 years, has all but succeeded. In the past few years, former strongholds such as Pakistan, Yemen and Sudan have declared themselves rinderpest-free. The only area where the virus that causes rinderpest may be holed up is a pocket of arid land straddling the Kenya-Somalia border, known as the southern Somali pastoral ecosystem.

Working out whether it’s there – and stamping it out – ought to be relatively simple: follow the tried-and-tested combination of vaccination and surveillance that has been so successful elsewhere. The prize would be to eradicate a disease for only the second time in human history.

But with success tantalisingly close, the drive to eliminate rinderpest is faltering, a victim of scientific disagreements, infighting, funding crises and the inevitable logistical problems of working in one of the hottest and least developed places on Earth. Failure would have severe global consequences. If the virus breaks out of its Somali bolt-hole, it could reinfect cattle across the Horn of Africa and beyond – including a reintroduction into Asia and Europe via the Arabian peninsular.

It is hard to overstate what a disaster that would be. Rinderpest has arguably caused more misery and deprivation than most human diseases, and has the potential to do so again. Since it was first described in China more than 3000 years ago, rinderpest epidemics have swept across the Old World on a regular basis, leaving death and destitution in their wake. As the UN noted in 1992, rinderpest is one of a select group of diseases that have changed the course of human history. It contributed to the fall of the Roman Empire, Charlemagne’s conquest of Europe, the French Revolution, the impoverishment of Russia and the colonisation of Africa.

The disease is caused by a morbillivirus, the same family as measles. It infects cattle, yaks and buffaloes and many of their wild and domesticated relatives including antelopes and giraffes. Different strains of the virus vary greatly in their virulence, and some mild forms can pass unnoticed. But in its “classic” form rinderpest is a swift and ruthless killer. The virus causes a high fever, discharges from the nose and eyes, abscesses on the gums, bloody diarrhoea and death within days. Because animals stay infectious for two weeks and the virus requires only minimal contact to be transmitted, classic rinderpest can sweep through herds, killing up to 90 per cent of those it infects.

Cat-and-mouse game

Rinderpest is a particular problem in the Horn of Africa, where cattle are a way of life and milk is often more readily available than water. This part of Africa is home to more than 100 million cattle that provide a livelihood for several million nomadic farmers. In Somalia, more than 80 per cent of the population are dependent on cattle, and trading is worth $4 million a year. Cattle mean status, wealth and security. In many cases marriage cannot occur without the exchange of cattle, and when the rains fail, which is often, many people trade cattle for grain. In times of famine, the death of a cow is often considered more of a disaster than that of a female family member.

For these reasons, eradicating rinderpest has been a major goal of the UN’s Food and Agriculture Organization (FAO) since its inception in 1945. The effort intensified in 1992 with the establishment of the Global Rinderpest Eradication Programme (GREP), which set 2010 as the target for eradication.

To stamp out the virus requires a combination of surveillance and vaccination. First you identify areas where rinderpest is circulating and carry out a mass vaccination campaign. Then you stop vaccinating, watch, and wait. If there is an outbreak of the disease or antibodies against the virus turn up in blood samples from unvaccinated animals, you pounce on the area and blitz it with vaccine. Then you enter another period of “wait and see”. If neither disease nor antibodies are seen for two years then the area can be declared disease-free. It’s a cat-and-mouse game that can take up to 10 years.

GREP has been remarkably successful. “We have made great progress,” says Peter Roeder, who leads the programme from the FAO offices in Rome. As recently as 20 years ago, rinderpest regularly wreaked havoc across large swathes of Asia and Africa (see Maps). Now it has been eradicated almost everywhere, except – maybe – southern Somalia, where rinderpest antibodies were last found in cattle in 2002. The priority now is to ensure that southern Somalia, too, is rinderpest free. Yet the endgame is fraught with so many problems it is hard to know where to start.

The main problem is that no one really knows what’s going on in southern Somalia. The consensus is that rinderpest of some kind is circulating there, but its nature and extent are contentious.

In 2002, herders in southwest Somalia reported that some cattle were showing symptoms of rinderpest. Antibodies to the virus were found in blood samples from 17 per cent of unvaccinated cattle aged 1 to 3 years. But there is disagreement over what the results mean. According to epidemiologist Henry Wamwahi of Terra Nuova, an Italian NGO that runs the Somali eradication programme, some labs concluded that the antibodies were evidence of “classic” rinderpest, others that it was a previously unknown, mild strain. It’s not clear how the discrepancy arose, but there have been allegations that some labs deliberately botched the results to fit the expectations of their paymasters. One senior source, who asked not to be named, said: “Some players simply won’t believe the results from certain labs. Without trust it really is impossible to rely on the labs.”

Reports of rinderpest in wildlife only add to the confusion. In 2001 there was an outbreak in buffaloes in the Meru National Park in Kenya, 300 kilometres from the Somali border. There is also antibody evidence that wildlife in eastern Kenya have been repeatedly reinfected, though no reports of disease. Some scientists believe that this shows there is a reservoir of virus in wildlife. Others, however, argue that it means a strain of rinderpest is still circulating among cows, which in turn are infecting wildlife. The disease usually dies out in wildlife once it has been eradicated from cattle.

Ego problems

If, as some scientists believe, classic rinderpest is still circulating widely in the Somali ecosystem then a mass vaccination campaign is called for. But if rinderpest infection is negligible, then surveillance is the best option. The two sides are locked in an acrimonious debate. As the same anonymous source said: “The science involved really is not rocket science. The difficulty is people management. When we really don’t know what the best answer is, those with strong opinions and strong egos are the ones who win.”

Terra Nuova wants to mass-vaccinate. It has maps showing where antibody-positive cattle have been found and a team of trained vets on standby. It says the antibodies are evidence that classic rinderpest is circulating – the only other explanation for the antibodies would be a recent vaccination campaign, and there hasn’t been one. It believes that if it vaccinates now the country can be rinderpest-free in five to six years. And a major GREP funder, the European Union, is on its side.

Many experts, however, strongly disagree. For one thing mass vaccination is time-consuming and extremely expensive: ensuring the vaccine is kept chilled means hiring four-wheel drives or aeroplanes, and training lots of people.

Mass vaccination could even be counterproductive, according to Leyland and his colleague Andy Catley of the African Union’s International Bureau for Animal Resources in Nairobi, which runs the eradication programme in Sudan, Kenya and Ethiopia. That’s because it potentially conceals the disease. It is logistically impossible to vaccinate all the cattle in the southern Somali ecosystem, so pockets of disease would remain in cattle populations that were assumed to be disease-free. Herders would be lulled into a false sense of security by vaccination and drop their guard against rinderpest symptoms, allowing the disease to emerge again.

Leyland and Catley argue that surveillance is the only answer. As the architects of systems that helped eradicate rinderpest in Sudan, Afghanistan and Ethiopia, they know what works. “This approach is slower and more difficult than vaccination, but we absolutely know it works, with appropriate modifications for southern Somalia,” says Catley.

Roeder, the acknowledged world expert on rinderpest, agrees. “If we stop, watch and wait, we see if there is disease in the population that re-emerges,” he says. “By keeping the cattle unvaccinated we allow the disease to surface, if it is going to, then vaccinate in the infected areas.” And in any case, Roeder points out, mass vaccination only works if it is followed by a period of surveillance.

But surveillance isn’t easy, as it relies on building a community-based network of trained people on the ground who can spot symptoms and report them. That’s a daunting prospect in Somalia. The country has been gripped by civil war for more than 20 years, there is no functioning government and civil society has all but broken down. For surveillance campaigns to work, neighbouring communities must work together, not attack one another and steal each other’s cattle. And a leaky surveillance system is as good as useless. “Unless we’re able to sustain surveillance programmes, the epidemic will get going again and it will become a pandemic,” says Roeder.

Surveillance is also a hard sell. Past experience in the Horn of Africa has shown that it takes years to convince herders that vaccination is not the answer. They want quick solutions and don’t like being asked to wait for the disease to break cover. “Getting people to stop vaccinating always takes some persuading,” says Roeder.

But once a network has been established, surveillance definitely works. Despite facing similar problems to Somalia, southern Sudan looks to have eliminated rinderpest using a community-based approach, says Bryony Jones of Vétérinaires Sans Frontières. Somalia could emulate that success, she says – though she is under no illusion about the difficulties. “We have to insist our vets can swim, and animal health workers may need to walk for up to six days to investigate and deliver rinderpest reports as there are no phones, planes, or faxes. When the rivers are flooded, or in the hot dry season, these are serious treks.”

Whatever option is eventually pursued, it will be difficult. Organising surveillance or vaccination programmes is notoriously difficult in Africa. Somalia is on the eastern fringe of a 9 million square kilometre swathe of sub-Saharan Africa where 32 of the world’s poorest countries survive by keeping livestock. No one keeps written records of their cattle, the animals are rarely fenced in and rustling is common. Herders are hard people to keep tabs on. Their movements, already notoriously unpredictable, are becoming more so – as the climate behaves in erratic ways, and civil wars cut off certain areas, herders and livestock are forced to move to unusual, inaccessible places.

Funding is also an issue. So far GREP has consumed ¬270 million and no one is prepared to put a figure on how much more is needed. The International Bureau for Animal Resources has to rely on a variety of donors, who typically fund in one or two-year cycles and often dictate the direction of the programme. Yet everyone agrees that to eradicate rinderpest will take at least five years.

What’s needed, says Roeder, is a long-term funding commitment so the job can be completed. Otherwise GREP risks going the way of the first project to eradicate rinderpest from Africa, which started in 1962. By 1977, rinderpest was confined to two small enclaves in Africa, one on the Sudan-Ethiopia border and the other in Mali. But the final surveillance phase faltered, and with cattle in rinderpest-free areas no longer being vaccinated, the virus began spreading again. The result was the great African rinderpest pandemic of the late 1970s and early 1980s. Facing destitution, many herders committed suicide.

The fear is that if GREP goes the same way, the eradication programme will be stalled for good. “If this one fails, it is unlikely that the international community will ever again be disposed to consider funding another attempt,” says Roeder.

The consequences of failure are grave. Rinderpest in Africa equals famine, poverty, disease and political instability. Failure will mean human misery for years to come. As Peter Kisopia, director of Oxfam’s pastoralist programme in Nairobi, says: “Up to 2 million pastoralists in Kenya are squatting in slums in towns because of what rinderpest did to them over a decade ago. They don’t recover quickly from rinderpest.”

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