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.

Tsetse movement in wind fields: possible epidemiological and entomological implications for trypanosomiasis and its control.

This paper presents evidence that tsetse flies (Glossina) can be dispersed by wind. This dispersal in West Africa is suggested to be along a south-west north-east axis. The implications of wind dispersal of Glossina for chemical and genetic control operations is discussed. Field experiments necessary to test this hypothesis are recommended. A study of human trypanosomiasis foci in West Africa has revealed that foci are orientated in roughly parallel lines in a south-west north-east direction. This directionally was significant when compared with 7 other compass points. It is proposed that foci could be populated by infected flies dispersed from the south west, where denser populations exist, on the prevailing winds in the late dry/early rainy season. The significance of these ideas in relation to the epidemiology of Trypanosoma brucei rhodesiense in Ethiopia and T. evansi are discussed.

A history of Rhodesian sleeping sickness in the Lambwe Valley.

The main events in the spread of Rhodesian sleeping sickness around the eastern shores of Lake Victoria during the 1930s and 1940s are summarized and the history of the disease in the Lambwe Valley area of western Kenya is described since its appearance there in 1959. The area was very receptive to the introduction and dispersal of T. rhodesiense on account of a close association between human communities and their domestic livestock, a large tsetse (Glossina pallidipes) population, and game animals. The possible origins of the first Lambwe Valley disease focus and the epidemiological significance of the main elements of the Lambwe environment (man, tsetse, game animals) are discussed in relation to the consolidation and spread of the disease throughout the area.Between 1968 and 1971 there was a marked decline in the incidence of the disease, probably as a result of tsetse-control operations that included ground and aerial application of insecticides, bush clearance, and the efforts of the Kenya Game Department to enforce the by-laws of the Lambwe Valley Game Reserve. However, it is considered that the situation remains potentially dangerous, mainly because populations of tsetse are recovering from the effects of aerial spraying and because there is evidence that the tsetse habitats are encroaching on farming land.

The hosts and trypanosome infection rates of Glossina pallidipes in the Lambwe and Roo valleys.

Several thousand Glossina pallidipes flies were dissected to determine trypanosome infection rates in the Lambwe Valley and to collect information on the hosts of this tsetse. A total of 1 450 (19.3%) flies had mature trypanosome infections but the rate varied between 9.6% and 30.9% in the Lambwe Valley. In the Roo Valley the rate was 19.7-28.6%. Blood-meal squashes from tsetse collected in the Roo Valley and Obaluanda areas and in the Ruma, Otuok, and Rari thickets showed that the important hosts were bushbuck and bushpig. Analyses showed that T. brucei subgroup infection rates in the Roo Valley near two small dams (3.7% and 4.0%) were higher than might have been expected; in another part of the Roo Valley the rate was only 0.8%. To account for such a large difference it is concluded that the dissecting techniques were probably at fault, leading to an overestimation of T. brucei subgroup infection rates in the Roo Valley tsetse. In the main Lambwe Valley there was a tendency for the tsetse trypanosome infection rates to increase towards the southern part of the valley where game animals were numerous and readily available to tsetse in the favourable thicket habitats.

Observations on the relative attractiveness to Glossina pallidipes of different animal baits, a tsetse trap, and a fly-round patrol.

Studies conducted in the Lambwe Valley, Kenya, have shown that in the absence of wild hosts, Glossina pallidipes was more attracted to a calf than to a sheep, a goat, a man, or a tsetse trap, although the latter attracted more flies than the nonbovid baits. Other investigations have shown that a newly developed tsetse trap was much more efficient at catching G. pallidipes than a standard fly-round patrol technique. An added advantage of the trap was that the sex ratio of flies caught by it was more representative of that existing in the fly population. Fly-round patrols always caught many more male than female flies.

The influence of game animals on the distribution and feeding habits of glossina pallidipes in the Lambwe Valley.

The role of game animals as important hosts of some species of tsetse, including Glossina pallidipes, has been studied in detail in the Lambwe Valley area of Kenya. A large population of G. pallidipes existed in association with a varied community of game animals in the study area, and the investigation was designed to determine which of the hosts available to G. pallidipes were actively selected and whether the preferred hosts influenced the distribution of the tsetse population. Bushbuck (Tragelaphus scriptus) was found to be the preferred host of G. pallidipes and there was a positive correlation between the distribution of these two species. Buffalo and roan antelope were also selected for food but, because of their behavioural characteristics, neither was continually available to the tsetse population and they had no influence on its distribution.

A technique for the bioassay of insecticide deposits on leaf and bark samples in relation to tsetse control operations.

During tsetse control operations it may be necessary to determine the effective toxicity and persistence of insecticide residues on vegetation. A simple method for preparing samples of twig bark for bioassay and an exposure apparatus that has been found very satisfactory for exposing tsetse flies to residues on leaves and bark are described. The apparatus is easily manipulated and involves little handling of the test material.