Cost-effectiveness analysis of alternative treatments of African gambiense trypanosomiasis in Uganda.

African trypanosomiasis, or sleeping sickness, is a tropical disease caused by trypanosome parasites transmitted by tsetse flies. The focus of this paper is on the cost-effectiveness of alternative drug treatments for patients in the late stage of the disease. Melarsoprol has been used for many decades. More recently, eflornithine has been developed. It has fewer side effects and improves the overall cure rate. It is much more expensive than melarsoprol, however. The objective of the present cost-effectiveness is to identify the costs and benefits that would be involved in switching from melarsoprol to eflornithine in the treatment of late stage sleeping sickness. Benefits are expressed in lives saved as well as in disability adjusted life years (DALYs). The analysis is applied to the case of Uganda. The implications for affordability are also considered, by taking account of how the treatment costs would be shared between the national government, donors and patients. The baseline results indicate that melarsoprol treatment is associated with an incremental cost per life and DALY saved of $209 and $8, respectively. Each additional life saved by switching from melarsoprol alone to a combination of melarsoprol and eflornithine would cost an extra $1,033 per life saved, and an extra $40.9 per DALY gained. Shifting from this second alternative to treatment of all patients with eflornithine leads to an incremental cost per life saved of $4,444 and an incremental cost of $166.8 per DALY gained.

Current situation of African trypanosomiasis.

African trypanosomiasis (sleeping sickness) is fatal, if untreated, and occurs in 36 African countries, south of the Sahara, where some 50 million people are at risk of acquiring infection. In the absence of adequate control measures epidemics occur, which are costly and difficult to control. The history of sleeping sickness has been characterized by waves of epidemics, resurgences and outbreaks. Nevertheless, sleeping sickness has been brought practically under control in the early 1950s, in West and Central Africa, through systematic surveillance of the population at risk and in East Africa, mainly by vector control. Following the attainment of independence from colonial rule in subsequent years, failure by national health authorities to give due attention to sleeping sickness control, due to civil and political unrest, lack of adequate resources and competing national health priorities, has resulted in epidemics and the recrudescence of many old foci and the appearance of new ones. Thus, sleeping sickness is currently a major concern among many countries, particularly in East and Central Africa. During the past decade, progress has been achieved through research in the development of new tools for diagnosis, which are simple to use by national health personnel and for vector control, which can be used at the community level. Eflornithine, a new drug, has been registered for the treatment of gambiense sleeping sickness, and although it is expensive, it is relatively safe and provides an alternative therapy to the existing treatment, which may cause severe adverse effects. These tools have raised hopes for improved control, but their integration into health care systems, which could improve surveillance of the population at risk, has been slow. In view of the worsening economic situation of endemic countries, and the focus of attention and resources on the AIDS pandemic, prospects of any significant improvement in the sleeping sickness situation would largely depend on the successful mobilization of external resources.

Perspectives in research on and control of African trypanosomiasis.

African trypanosomiasis affects both man and his domestic animals, and is fatal if untreated. The risk of epidemics makes the disease a major public health problem in 36 sub-Saharan African countries, where some 50 million people are at risk of contracting the disease. Continued suppression of the disease through medical surveillance is indispensable to prevent epidemics which are difficult and costly to control. Recent epidemics and flare-ups have occurred in certain countries due to breakdown in medical surveillance occasioned by political, social and economic factors. The development of new tools through research over the last decade has improved the diagnosis of patients and vector control. The development of eflornithine (DFMO) for the treatment of gambiense sleeping sickness is a major breakthrough in view of its safety compared with current treatment alternatives, and it has been nicknamed the 'resurrection drug'. In spite of these achievements, however, there is no radical solution to the problem of sleeping sickness. The use by the endemic countries of improved tools for disease control depends upon the availability of resources from national, bilateral and multilateral sources, and commitment of the countries concerned.

Current knowledge on epidemiology and control of sleeping sickness.

African trypanosomiasis (sleeping sickness) occurs in some 200 known foci within tsetse inhabited areas in sub-saharan Africa, where an estimated 50 million people are at risk of acquiring infection. Only 25,000 new patients are reported each year but this is an underestimate. Where medical surveillance was inadequate or lacking, serious epidemics could occur and this potential risk makes the disease one of the serious health problems in sub-saharan Africa. The chronic gambiense form of sleeping sickness occurs in West and Central Africa, while the acute rhodesiense form occurs in East and Southern Africa. Recent advances in science have improved knowledge on the epidemiology of the disease and provided tools for improved diagnosis, treatment and vector control. The current strategy for control of the disease is based upon continuous suppression through diagnosis and treatment and limited vector control with community participation. Nevertheless, long-term solution to the problem of African trypanosomiasis lies in effective land-use management and rural development.

Trypanosome infection rates of Glossina spp. (Diptera: Glossinidae) in transitional forest-savanna near Bouaflé, Ivory Coast.

Tsetse, caught in biconical traps near Bouaflé, Ivory Coast in 1980-81, were examined for trypanosome infections. In a sample of 1138 non teneral Glossina palpalis s.l. there were infection rates of 12.2% (all infections) and 5.3% (mature infections). Female flies had a significantly higher infection rate than males. In G. palpalis only 3 (0.26%) salivary gland infections were detected, 62.3% of the mature infections were T. vivax-like and 71.4% of all infections were restricted to the midgut. The infection rate in forest/plantation caught G. palpalis was twice that of village caught flies. The infection rate increased with fly age and is correlated in female flies. In smaller samples of G.p. pallicera and G. fusca group flies the trypanosome infection rates were 37% and 46% respectively. In both these groups of flies 64.7% of infections were mature and were predominantly T. vivax-like and in females.

[Breeding sites of Glossina palpalis s.1. pupae in a transitional woodland area in Ivory Coast]. / Gîtes à pupes de Glossina palpalis s.1. dans une zone préforestière de Côte d'Ivoire.

Search for pupae of G. palpalis s.1. was conducted from February to December 1981 in the Bouaflé area, Ivory Coast. 1909 pupae were collected from 70 breeding sites after 518 hours of search. Pupae were found both in the dry and the rainy seasons. The vegetation and the nature of the soil seem to be two inseparable factors for the creation and the maintenance of Glossina breeding sites in the study area. In localities with high pig population density, a greater number of pupae were found either at the edge of the village or at a distance not exceeding 500 m from the houses. This observation confirms peridomestic behaviour of G. palpalis s.1. in these localities. On the contrary, in localities with low pig population density or without pigs, peridomestic breeding was not observed; all the pupae were found at a distance 500 m to 3 km away from the houses, in coffee and cocoa plantations and in woodlands. The epidemiological significance of the distribution of G. palpalis s.1. breeding sites in the study area is discussed.

Traps to control and estimate populations of Glossina species.

Biconical traps were used to capture continuously Glossina palpalis s.l. in Ivory Coast and G. morsitans centralis in Zambia for 19 and 20 days respectively. Both fly populations declined markedly during the continuous trapping period though populations subjected to intermittent trapping or where the traps were very widely spaced did not do so to the same extent. Fly density was estimated by applying the principles of removal trapping and were compared with other trapping studies. The results demonstrated that biconical traps removed 7% of the female component of the population each day and that this 7% removal value was itself a measure of absolute trapping efficiency; providing a novel means of population estimation. The potential of traps to control tsetse and thus break trypanosome transmission cycles or reduce 'challenge' on a self-help basis at the village level is discussed.

Differences in rate of wing fray between Glossina species.

Differences exist in the rate of wing fray, as shown by correlation with ovarian age as a time scale, and thus presumably flight activity, for Glossina pallidipes, G. f. fuscipes, G. morsitans, G. tachinoides, G. palpalis s.l. and G. palpalis gambiensis. The wings of females fray more slowly than males for all the above species. Female G. palpalis s.l. in the forest habitat of Ivory Coast seem on this basis to be considerably less active than other flies considered. G. p. gambiensis females are more active in the dry season, than the wet season in Upper Volta, as judged by wing fray and this is the first time a seasonal viration in rate of wing fray has been observed as far as we are aware.