Three hundred thousand cases of trypanosomiasis, or sleeping sickness, occur in Africa each year. Traditionally, the acute form of the disease has occurred in East Africa and the chronic form in West and Central Africa. However, new evidence suggests that the focus of both forms is expanding and they may soon overlap in Uganda.

An average of 25,000 new cases of acute and chronic sleeping sickness is reported annually, although this is generally thought to be an underestimate resulting from low detection rates. Sixty million people live in risk areas, and as many of these have poor access to diagnostic and health care facilities, under-reporting rates are high.

Two different sets of parasites are responsible for the acute and chronic forms of the disease.  Historically, refugee migration and movement of livestock have been key factors in transmission. A research team led by Sue Welburn and colleagues from the Royal (Dick) School of Veterinary Studies, Edinburgh, UK, looked at the distribution of both sets of parasites in Uganda.

The researchers took blood samples from patients with sleeping sickness, 231 in central Uganda and 91 in northwest Uganda and south Sudan, and screened them for both sets of parasites. They then observed the historic spread of sleeping sickness in the region, in terms of land area affected and population at risk.

All the samples from central Uganda had the parasite for the acute form of the disease, while all those from northwest Uganda and south Sudan had the parasite for the chronic form. However, the area of Uganda affected by acute sleeping sickness had increased over the past 20 years. Results showed that:

• The area of Uganda where there is acute sleeping sickness has increased two and a half times since the mid-1980s, while the population at risk from the disease has doubled.
• From 1998 onwards, an epidemic of acute sleeping sickness has spread into the north of the country, coinciding with the movement of domestic cattle in the region.
• Disease control activities aimed at controlling acute sleeping sickness have been largely unsuccessful.
• At the same time, refugee movements due to civil unrest on the Sudanese border have resulted in the persistence and spread and of chronic sleeping sickness.
• The main districts affected by the spread of the two diseases lie only 150 kilometres apart.
• The area currently at risk from acute sleeping sickness now overlaps with a region where there was a chronic sleeping sickness outbreak in 1957. 

The researchers conclude that the focus of the two diseases remains separate. However, they stress that if infected cattle continue to be traded northwards without control measures, the two diseases will overlap. Civil instability in some areas will make surveillance systems difficult to sustain, with grave implications for disease control in the region. They recommend:

• assessing the costs and benefits to the public health and livestock sectors of removing the reservoir of human sleeping sickness parasites in animals through livestock treatments
• treating livestock for sale in Uganda at their point of origin or before sale, and strengthening and enforcing this policy at district level
• putting into place surveillance systems for the continued monitoring of the disease in both humans and livestock
• immediately setting up a properly equipped screening laboratory, perhaps internationally funded but locally managed, alongside staff training
• giving priority to public health information campaigns, particularly among the poorest communities.

Source(s):
'Sleeping sickness in Uganda: a thin line between two fatal diseases', British Medical Journal 331, pages 1238-1241, by Kim Picozzi, Eric M Fèvre, Mark C Eisler, Ian Maudlin, Susan C Welburn, Martin Odiit and Mark Carrington, 2005
'Crisis, what crisis? Control of Rhodesian sleeping sickness', Trends in Parasitology 22, pages 123-128, by Susan C. Welburn, Paul G. Coleman, Eric M. Fevre, Martin Odiit, Ian Maudlin and Mark Eisler, 2006
HINARI subscribers can access the full-text article here. Full document.

Funded by: UK Department for International Development's (DFID) Animal Health Program, World Health Organisation, and the Cunningham Trust, the Wellcome Trust.

id21 Research Highlight: 9 May 2006

Further Information:
Sue Welburn
Centre for Infectious Diseases
Royal (Dick) School of Veterinary Studies
The University of Edinburgh
Edinburgh, EH9 1QH
Scotland, UK

Tel: +44 (0) 131 6506228
Fax: +44 (0) 131 6506289
Contact the contributor: sue.welburn@ed.ac.uk

Royal (Dick) School of Veterinary Studies, Edinburgh, UK

The Wellcome Trust - Livestock for Life Scheme

Other related links:
'Fighting sleeping sickness during the Angolan civil war'

'Animal to human: controlling diseases which affect poor people and livestock'

'Caught napping - cattle movements and a new sleeping sickness outbreak in Uganda'

'Livestock management in southern Sudan: can programmes be improved?'

'Natural resource management and human health: the forgotten link?'

'Community vetting? Explaining success in participatory animal health interventions'

'A better breeds? Improving livestock in West Africa'