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Analysis of risk factors for T. brucei rhodesiense sleeping sickness within villages in south-east Uganda

25 Jul 2008

Paul Chinnock

Source: BMC Infectious Diseases (see original article)

Citation: Zoller T, Fèvre EM, Welburn SC, Odiit M, Coleman PG. Analysis of risk factors for T. brucei rhodesiense sleeping sickness within villages in south-east Uganda (2008). BMC Infect Dis; 30(8):88.

Human African trypanosomiasis (HAT, or sleeping sickness)is a major and increasing concern in many parts of Africa. An estimated 300,000 new human infections occur every year, with an estimated 46,000 deaths. It is also a serious problem for the health of livestock. In those parts of East Africa which are afflicted by HAT the organism responsible is Trypanosoma brucei rhodesiense, which is transmitted by the testse fly Glossina fuscipes fuscipes.

The distribution of the disease is patchy but research has established the geographical areas in which communities are most at risk. However, knowledge has so far been lacking at village level. In other words, it is not clear which people in a typical village – as a consequence of their behaviour or where their house is located – are most likely to get sleeping sickness.

Working in southeast Uganda, Zoller et al. used a questionnaire-based case-control study conducted in 17 villages endemic for HAT. They also analysed spatial risk factors in four high-risk villages. Two-thirds of the infections were in men. The investigators identified having a family member with a history of HAT and the proximity of a homestead to a nearby wetland area as the strongest risk factors for infection.

There were some surprising findings. Water contact activities (e.g. washing clothes or fetching water) have been believed to carry a high risk for infection, as it would be expected to bring people into more frequent contact with the tsetse fly. This study however found no direct association between these activities and HAT infection. In contrast the presence of cattle close to the homestead emerged as a risk factor. Those people who spend a significant amount of time outside the village seem to have a lower risk for HAT infection. Growing cassava seemed to increase risk, whereas growing bananas appeared to be protective.

The authors say that their findings will be useful as a basis for designing further studies, as well as for developing control and intervention programmes.

2008 Zoller et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Source

Title:
Analysis of risk factors for T. brucei rhodesiense sleeping sickness within villages in south-east Uganda.

Authors:
Zoller T, Fèvre EM, Welburn SC, Odiit M, Coleman PG

References:
BMC Infect. Dis. 2008: Vol. 8, pp. 88

Abstract:
BACKGROUND: Sleeping sickness (HAT) caused by T.b. rhodesiense is a major veterinary and human public health problem in Uganda. Previous studies have investigated spatial risk factors for T.b. rhodesiense at large geographic scales, but none have properly investigated such risk factors at small scales, i.e. within affected villages. In the present work, we use a case-control methodology to analyse both behavioural and spatial risk factors for HAT in an endemic area. METHODS: The present study investigates behavioural and occupational risk factors for infection with HAT within villages using a questionnaire-based case-control study conducted in 17 villages endemic for HAT in SE Uganda, and spatial risk factors in 4 high risk villages. For the spatial analysis, the location of homesteads with one or more cases of HAT up to three years prior to the beginning of the study was compared to all non-case homesteads. Analysing spatial associations with respect to irregularly shaped geographical objects required the development of a new approach to geographical analysis in combination with a logistic regression model. RESULTS: The study was able to identify, among other behavioural risk factors, having a family member with a history of HAT (p = 0.001) as well as proximity of a homestead to a nearby wetland area (p < 0.001) as strong risk factors for infection. The novel method of analysing complex spatial interactions used in the study can be applied to a range of other diseases. CONCLUSION: Spatial risk factors for HAT are maintained across geographical scales; this consistency is useful in the design of decision support tools for intervention and prevention of the disease. Familial aggregation of cases was confirmed for T. b. rhodesiense HAT in the study and probably results from shared behavioural and spatial risk factors amongmembers of a household.

PMID: 18590541
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