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Preventing the next plague

With countless birds dead, whether to culling or disease, the serious impact of Avian flu on the Asian poultry industry is beyond question. However, it is the danger to human health from this zoonotic disease that has really hit the headlines. More than 50 people in Southeast Asia have died from the disease, and the big fear is that the avian flu virus will mutate to allow direct human-to-human transmission. The result could be the first global flu pandemic in decades, potentially killing millions of people.

Cattle and people living in close proximity on a homestead in Busia, Kenya (Dave Elsworth)
Cattle and people living in close proximity on a homestead in Busia, Kenya
Dave Elsworth

There are over 200 zoonotic diseases that kill and debilitate large numbers of people and livestock every year. Rabies, brucellosis, bovine tuberculosis and sleeping sickness are just a few that are endemic in Africa. Most zoonotic diseases can be readily prevented, and yet millions of people, particularly the poor in developing countries, remain at risk. According to François Meslin of the World Health Organisation (WHO), "these are not diseases that are flaring up or have the potential to spread to the rest of the world. But we owe it to the people who suffer from them to work more closely together."

Not just for emergencies

By 'we', Meslin refers to human and animal health professionals. His point is that, in controlling any zoonotic disease, a more holistic approach is needed, with co-operation between the ministries responsible for livestock diseases and public health. "Unfortunately," he continues, "it often takes an emergency, such as avian flu or the emergence of the Nipah virus, to get sufficient resources mobilised and sectors brought together to work in unison rather than in competitive conflict." Cross-sectoral control efforts are evident in some countries. Tanzania is one such example with veterinary and medical researchers collaborating to control bovine tuberculosis, brucellosis and rabies. But, says Meslin, more needs to be done.

If prevention is better than cure, surely the responsibility lies with veterinary services to diagnose and treat livestock and thereby prevent the spread of zoonotic diseases to humans? Meslin agrees that veterinary services in many developing countries need strengthening, adding that the perspective of veterinarians also needs to change. Public health issues, he insists, should be included in veterinary training and practice.

Information is key...

Yet the occurrence of zoonotic disease continues to be under-reported. Eunice Forster, head of the Veterinary Public Health Unit in Accra, Ghana, stresses that insufficient data results in a lack of evidence to convince policymakers that these diseases need tackling. The number of human rabies cases reported each year in Ghana, for instance, is low when compared to the incidence of other diseases, but no one who has witnessed the distressing effects of the disease could argue that it was not a problem worth tackling, particularly when children are most vulnerable to being bitten. Vaccinating dogs is a relatively simple control measure for rabies, although, says Darryn Knobel, a researcher working on a rabies-control programme in Tanzania, it must be combined with ongoing education and awareness, to prevent a cyclical pattern of disease occurrence and decline. "Vaccination can be a victim of its own success in that, as the number of rabies cases drop, people become less aware of the dangers of the disease." Maintaining vigilance despite falling case numbers is essential.

Alexandra Shaw, an economist who has worked in human and animal health for many years, is aware that Africa's human and veterinary health services are over-stretched and that it can be difficult to mobilise resources to deal with so many diseases. "But treating livestock is highly effective," she says, "and it provides enormous potential to intervene in a very cost-effective way." For example, to treat one patient with sleeping sickness with drugs over a one-month period costs US$250, provided that the drugs are available. Treatments for rabies, brucellosis and bovine tuberculosis are equally costly. Treating livestock is much cheaper and therefore a far more cost-effective option as well as resulting in additional benefits in terms of improved livestock productivity and farmers' livelihoods.

...but better understanding required

Farming family in Busia, Kenya (Dave Elsworth)
Farming family in Busia, Kenya
Dave Elsworth

For many zoonotic diseases much more needs to be known before effective interventions for control can be drawn up. Brucellosis, for instance, tends to be quite widespread in developing countries but very little information is currently available on the disease or its economic impact. A study conducted by the University of Nairobi, and funded by the DFID Livestock Production Programme (LPP), is bringing together veterinary and public health researchers to understand more about the prevalence of brucellosis and the livelihood factors that contribute to contracting the disease. "The results from this study will be beneficial to both the veterinary and public health departments," says Dr James Wabacha, one of the veterinary researchers involved in the study. "And with that information we will then be able to put the appropriate interventions in place."

Better understanding of bovine tuberculosis (BTB) is also essential, says Sarah Cleaveland of the Centre for Tropical Veterinary Medicine at the University of Edinburgh. Treating livestock against the disease is currently not an option although vaccines are under development. The emphasis is therefore on the human health side to monitor the disease and determine whether people suffering with BTB respond as well to treatment as those with the classic form of TB. "It is a difficult disease to work with," says Cleaveland, "and there are still some important questions to answer. But policymakers are paying attention and I think the need for understanding these zoonotic diseases is becoming clearer."

The research featured in this article was highlighted at a workshop held in Nairobi organised by the Animal Health Programme (AHP) of the UK Department for Development (DFID).

Date published: July 2005

 

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