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Based on data collected during regular, biconical trap sampling of Glossina palpalis palpalis (R.-D.) over two and a half years during and after two insecticide programmes in Ivory Coast, various analytical techniques were developed which allow the estimation of mortality rates and life-time fertility from ovarian age distributions of female flies. Data from trapping-out experiments were used to calculate the natural resilience of local populations. The results reveal that the dynamics of the populations showed considerable local variation, with two major types of sites. At those sites with large numbers of domestic pigs, the fly population was dense and showed a high degree of natural resilience and a low mean mortality rate, so that it could be selfsustaining through reproduction alone. At sites with few pigs, the fly population was scarce and showed a lower degree of natural resilience and a higher mean mortality rate such that the population couJd only be maintained by continuous input of immigrant flies. Studies of the natural dynamics of tsetse can be used to predict the likely effectiveness of alternative control schemes; fly mortality rates must be permanently increased in order to reduce fly numbers or infection rates to below some threshold for disease transmission.

Oral DFMO at the dose of 125 mg/kg body weight given every 6 h for 14 days may not produce adequate therapeutic plasma and CSF levels for patients with late-stage T.b. gambiense sleeping sickness.

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.

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