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Dr William Olaho-Mukani

Dr William Olaho-Mukani talks about the problems sleeping sickness causes and proposed new ways to tackle it
Dr William Olaho-Mukani talks about the problems sleeping sickness causes and proposed new ways to tackle it

The need to control sleeping sickness

Dr William Olaho-Mukani is Director of Animal Resources in the Ugandan Ministry of Agriculture, Animal Industries and Fisheries (MAIF). As he explains, recent research findings suggest a new approach to tackling sleeping sickness that could reverse a deteriorating situation.

A worrying situation

In Uganda we currently have a very serious situation on our hands. Sleeping sickness is caused by a parasite that is transmitted by tsetse flies. The acute form of the disease, caused by the trypanosome Trypanosoma brucei rhodesiense, is transmitted to humans by tsetse that feed on infected cattle or wildlife. The disease in animals, known as nagana, was until recently confined to southeast Uganda and western Kenya. For more than a century, this disease has been claiming human lives in the south-east - several hundred thousand over the years. But since the late 1990s the rhodesiense form of the disease has been spreading northwards. Over the last few years, human cases of the disease have been found in new districts, beyond the traditional foci: Soroti in 1999, Kaberamaido in 2003, Lira in 2004 and most recently in Apac. It may have even gone further, perhaps to Gulu and Pader.

In Uganda we are the only country to also have the chronic form of sleeping sickness, caused by T. b. gambiense. This disease only affects humans and not cattle. It is currently only in the north-west of the country, close to the Sudanese border. But disturbingly, the foci for T. b. gambiense and T. b. rhodesiense have been converging, with now only 150 km between them at the closest point. If the two forms of the disease come together, diagnosis and treatment for sleeping sickness - which is already difficult - will be severely compromised.

The role of cattle

The northward spread of the rhodesiense form of the disease is linked to the movement of infected cattle, from endemic areas in the south to be sold further north. Research carried out over the last decade or so has revealed the major role that cattle play in the life cycle of the disease. Cattle often carry the parasites without themselves showing any symptoms. Tsetse flies feeding on these animals become infected with the parasites which can be passed to people - who get acute sleeping sickness. If not diagnosed and treated, these people die within a few months.

Only recently, with the development of new diagnostic tools, have we realised just how important the animal reservoir is for rhodesiense sleeping sickness. Latest estimates suggest nearly all cattle in endemic areas carry the parasites, which is of great concern.

A need for action

The Ugandan government and the international community are aware of the seriousness of the situation and the need to take decisive action. And the affected local communities are shouting for help. The World Health Organization (WHO) convened a meeting in Addis Ababa in September last year, and a number of recommendations were made to address the situation, but so far we have been unable to make much progress.

Patients in the late stages of sleeping sickness are costly to treat, especially given the very limited funds and facilities available at district level. Since cattle play such an important part in the epidemiology of the rhodesiense form of the disease, we hope to tackle the spread of the disease in a new way. As well as focusing on the disease in people, we could also treat cattle. Treatment of the disease in cattle is relatively simple and cost-effective with drugs and insecticides, which can eliminate the disease from the animal population and therefore prevent its spread. Field trials have recently been completed which suggest that, if 86 per cent of cattle were treated with drugs that kill the rhodesiense parasites, we could eliminate the animal reservoir. If there are no parasites in cattle, there will be no new cases of human sleeping sickness. So we plan to mount a large-scale block treatment campaign. Starting with those districts newly affected by rhodesiense sleeping sickness, we aim to treat all the cattle with trypanocide drugs. This should stem the northward spread of the disease, and prevent further human cases. We then intend to 'roll back' the disease by sweeping southwards towards more endemic areas, treating the cattle in each district.

Sustaining the achievements

Once the cattle are treated, we need to make sure they stay free of the trypanosome parasites. So we plan to work with commercial partners from veterinary pharmaceutical companies to encourage livestock owners to regularly spray their animals. Data from field trials show that, by targeting deltamethrin spray to certain parts of the body - the legs where tsetse flies mostly feed and the sites where ticks cluster - both these pests can be controlled using much less spray that is generally used. In fact, using the 'restricted application' spray method, it costs only around US$0.02 to spray one animal. If we can convince farmers of the benefits of spraying their animals regularly for just a few shillings we believe we will be able to sustain the achievements of the block treatment campaign.

After a recent meeting with potential partners - from both the public and private sectors - we are extremely hopeful that we will soon be able to start this block treatment campaign. Our objective is ambitious: we plan to not only stop the northward spread of rhodesiense sleeping sickness but to eliminate this disease completely from our country.

Date published: July 2006

 

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