The dynamics of trypanosome infections in natural populations of tsetse (Diptera: Glossinidae) studied using wing-fray and ovarian ageing techniques

Trypansosome infections in approximately 110,000 tsetse of 12 species or subspecies, at sites in six African countries, were studied over various periods from 1983 to 1994. Infection rates ranged from 0.2 percent in Glossina fuscipes quanzensis Pires at a site in Zaire, to 18 percent in Glossina tabaniformis Westwood at a site in Gabon. Statistical models were fitted to data for nine species or sub-species of tsetse (G. pallidipes Austen, G. morsitans morsitans Westwood, G. morsitans submorsitans Newstead, G. fuscipes fuscipes Newstead, G. fuscipes quanzensis Pires, G. palpalis palpalis Robineau-Desvoidv, G. palpalis gambiensis Vanderplank, G. tanchinoides Westwood and G. tabaniformis Westwood), recorded across eight sites. The prevalence of mature trypanosome infections increased with age, as determined by wing-fray category, for both Trypanosoma vivax-and T. congolense-type infections, although for G. palpalis, G. tabaniformis and G. tachinoides the rate of T. vivax-type infections decreased in older age categories. Infection rates for T. brucei were very low and statistical analysis was not possible for this species. Overall prevalences of Trypanosoma vivax-type infections were significantly higher in female than male flies in four tsetse species; G. pallidipes, G. palpalis, G. tabaniformis and G. tachinoides. At sites where ovarian ages were also determined, close correlations between wing-fray category and ovarian age were found

Tsetse control: Recent successes in Tanzania and Ethiopia

Trypanosomiasis remains the most important constraint to livestock production on the African continent. Chemotherapy, using curative and prophylactic drugs, is the main method of control of the disease in cattle. The exploitation of the trypanotolerance trait of some breeds of large and small ruminants provides a solution in certain production systems. Immunological approaches to control the disease through vaccination are still under investigation. Only the eradication of the tsetse fly vector can remove the treat of the disease. By coincidence two biologists defended their PhD theses on aspects of tsetse control almost at the same time at two universities in The Netherlands. On 19 December, 1995, Marc Vreysen from Belgium defended his thesis entitled: 'Radiation induced sterility to control tsetse flies. The effect of ionising radiation and hybridisation on tsetse biology and the use of the sterile insect technique in integrated tsetse control' at Wageningen Agricultural University. Three months later, on 22 February, 1996, Stephen Leak from the UK defended his thesis: 'A contribution to the epidemiology and understanding of tsetse-transmitted trypanosomiasis' at Utrecht University. In this article some of the results of these studies will be discussed. Emphasis will be on the applications of the control measures under field conditions at the respective study locations: Unguja island of Zanzibar, Tanzania and the Ghibe Valley in Ethiopia. For further reading a list of references is provided and readers who are interested in more details are invited to write to the authors

Advance of Glossina morsitans submorsitans and G. pallidipes along the Ghibe-river system in southwest Ethiopia

Tsetse fly populations have been monitored since January 1986 in two areas of the Ghibe valley in southwest Ethiopia, in order to assess trypanosomiasis risk to cattle. The two study areas are Abelti/Ghibe and Gullele/Tolley. Two species of tsetse fly were detected in the valley from 1986 to 1992; these were Glossina pallidipes and G. fuscipes. Both species appeared to be largely restricted to thicket vegetation along the gallery forest of the Ghibe river. In 1989, G. M. submorsitans was detected for the first time in the western, upstream study site-Gullele/Tolley. This species was not detected in the downstream, eastern area of Abelti/Ghibe until 1992. Since 1986, G. pallidipes has been found to be the most important vector of pathogenic trypanosomes to cattle in the Ghibe valley. However, G.M. submorsitans could be come more significant than G. pallidipes in the epidemiology of bovine trypanosomiasis in the area as it is a highly vector of trypanosomes and many potentially occupy a wider area of the savanna woodland in the valley than G. pallidipes

Potential demand for a mixed public-private animal health input: evaluation of a pour-on insecticide for controlling tsetse-transmitted trypanosomiasis in Ethiopia

The new pour-on insecticides that can be used to control tsetse-transmitted trypanosomiasis confer benefits to the owners of the cattle given treatments and other people keeping cattle in areas affected by the control. A study was conducted in southwest Ethiopia to assess farmers' perceptions of the public and private benefits of the pour-on and identify the household-level factors affecting its demand. Ninety-seven percent of the 166 survey respondents had received pour-on treatments when they were free and 67 percent paid for treatments the month before the survey. Farmers noted public and private benefits from using the pour-on, the most important of which were less trypanosomiasis, fewer problems with biting flies (including tsetse), and fewer problems with ticks. The probit model estimated to quantify the effects of different variables indicates that proportions of cows and oxen, distance to the treatment centre, and seasonal factors were significant determinants of demand

Factors affecting estimation of tsetse challenge and the expression of trypanotolerance

Factors affecting the expression of trypanotolerance are discussed. Some of the factors which could influence the feeding preference of tsetse are physical - skin thickness, skin rippling; visual - coat colour, size; olfactory - breath, urine, skin secretions; behaviour - tail flicking, head swings. It is suggested that whilst there are lower transmission potentials between trypanotolerant livestock and tsetse, the main differences between trypanotolerant and trypanosusceptible breeds of livestock are found in the way in which different cattle deal with the trypanosomes that are transferred during the bite of an infected tsetse

Evaluation of pour-on by Ethiopian farmers

Since April 1990 a tsetse control experiment with the synthetic pyrethroid Ectopour has been conducted in the Gullele-Tolley area of the Ghibe Valley, southwest Ethiopia. Monthly applications of the pour-on were given to about 2,000 cattle between April 1991 and July 1992 and about 3,000 cattle between July and November 1992. Since December 1992 the treatments have been made available to all farmers in the area on a cost recovery basis. Formerly the treatments were free to selected farmers. A survey of 200 household heads who keep cattle in the control area was conducted to assess the impact of the price increase on farmer's demand for the treatments. Respondents to the household survey were asked about the advantages of the pour-on. Farmers noted a variety of advantages such as less trypanosomiasis (gendi), fewer problems with ticks, the animals graze well and quietly, cows are quieter when milking, there are fewer problems with ox peckers bothering the animsl, and the animals' wounds heal faster