The control of sleeping sickness in Nigeria

Beyond Tsetse--Implications for Research and Control of Human African Trypanosomiasis Epidemics

Epidemics of both forms of human African trypanosomiasis (HAT) are confined to spatially stable foci in Sub-Saharan Africa while tsetse distribution is widespread. Infection rates of Trypanosoma brucei gambiense in tsetse are extremely low and cannot account for the catastrophic epidemics of Gambian HAT (gHAT) seen over the past century. Here we examine the origins of gHAT epidemics and evidence implicating human genetics in HAT epidemiology. We discuss the role of stress causing breakdown of heritable tolerance in silent disease carriers generating gHAT outbreaks and see how peculiarities in the epidemiologies of gHAT and Rhodesian HAT (rHAT) impact on strategies for disease control.

An assessment of the economic importance of the tsetse species of Southern Nigeria and the Southern Cameroons based on their trypanosome infection rates and ecology

Previous records and new data on infection rates in species of Glossina inhabiting southern Nigeria and the Southern Cameroons are presented, and the probable economic importance of each species is assessed.

The trypanosome infection rates were highest in those species of tsetse which fed largely on Bovidae.

The rarity of human trypanosomiasis in southern Nigeria and the Southern Cameroons is attributed largely to impersonal man/fly contact; under such conditions a low proportion of infected flies is to be expected. G. palpalis (R.-D.) is not an important vector of sleeping sickness, as it is in northern Nigeria. The incidence of infection in G. palpalis was generally very low; cases of bovine trypanosomiasis do occur in areas where G. palpalis is the only tsetse species present, but it is not considered to be an important vector.

Little information is available on G. tachinoides Westw. and G. caliginea Aust. in southern Nigeria; both have probably been at least partly responsible for some of the rare outbreaks of sleeping sickness reported from the south. G. tachinoides may be of some significance as a vector of animal trypanosomiasis.

The infection rate in G. longipalpis Wied. at the West African Institute for Trypanosomiasis Research Field Station at Ugbobigha was 21·5 per cent.; this species is believed to be of major economic importance because its presence must prevent the keeping of cattle in large areas of potential grazing.

At least 13 per cent, of examples of G. medicorum Aust., G. fusca (Wlk.) and G. nigrofusca Newst. were infected in the populations examined, and the first two species are considered to be of economic importance because they penetrate potential grazing areas.

G. pallicera Big., G. tabaniformis Westw. and G. haningtoni Newst. are confined to rain-forest and were found to be lightly infected; they are therefore not considered to be of economic importance, except possibly as a source of infection to cattle on trade routes.

No data are available for G. nashi Potts.