WHO Report on Global Surveillance of Epidemic-prone Infectious Diseases - African trypanosomiasis
- Between 1940 and 1960, the reported number of cases of sleeping sickness declined dramatically, from nearly 60 000 cases per year to almost zero. These data present a relatively accurate reflection of the trends during this period as there was systematic screening of populations at risk during these years (Fig. 8.2).
- Beginning in the mid-1970s and continuing until the present, there has been a steep increase in the number of cases reported. At the same time, population screening has been reduced to a very small number of people. This means that the number of reported cases is a gross underestimate of the current number of cases, since population screening is the main case-finding technique.
- Fig. 8.2 also illustrates the role that systematic population screening and subsequent treatment of cases play in the control of sleeping sickness. When the screening and treatment process stopped, it was followed by a dramatic increase in disease.
- The remoteness of the areas in which the disease occurs, and the focal nature of the disease, make it difficult to estimate the incidence and prevalence of the disease. In 1999, there were a total of 40 000 cases reported. However, only 3 to 4 million of the estimated 60 million people at risk of the disease were either actively screened, or had access to a health centre with diagnostic and treatment capability.
- In many countries there is no surveillance and the situation is poorly understood. These countries include Ghana, Nigeria, Sierra Leone, and Liberia.
- The number of cases in Angola is increasing rapidly. Access to epidemic areas is extremely difficult because of the state of war.
- The Democratic Republic of the Congo is the worst hit country. More than 70% of the reported cases come from this country. Prevalence of more than 70% have been found in the Bandundu and Equateur provinces. In these provinces sleeping sickness is the largest cause of mortality (7).
- The epidemic is progressing in Sudan, where only a few NGOs are treating the new cases.
- African trypanosomiasis is still a serious problem in the Cote d'Ivoire and in Guinea. In other West African countries, few cases have been reported and there is currently regular surveillance of at-risk areas.
- There is a continuing epidemic of rhodesiense sleeping sickness in the United Republic of Tanzania and Uganda.
- The number of new cases seeking treatment in the second stage of illness has been increasing for the past three years. In addition, the number of treatment failures during the second stage is increasing and is currently between 15 and 30%. The reason for this increase in treatment failure during the second stage remains unclear.
(7) Ekwanzala M et al. In the heart of darkness: sleeping sickness in Zaire. Lancet, 1996, 348:1427-1430.
Figure 8.2 Number of reported cases of African trypanosomiasis and population screened, 1940-1998