title: Spatial distribution and trypanosome infection of tsetse flies in the sleeping sickness focus of Zimbabwe in Hurungwe District.
abstract: In Zimbabwe, cases of human African trypanosomiasis (HAT) are caused by the unicellular protozoan Trypanosoma brucei, sub-species T. b. rhodesiense. They are reported from the tsetse-infested area in the northern part of the country, broadly corresponding to the valley of the Zambezi River. Tsetse-transmitted trypanosomes, in particular T. congolense and T. vivax, also cause morbidity and mortality in livestock, thus generating poverty and food insecurity. Two species of tsetse fly, Glossina morsistans morsitans and G. pallidipes, are known to be present in the Zambezi Valley, although their distributional patterns and densities have not been investigated in detail. The present study tries to address this gap by providing some insight into the dynamics of trypanosomiasis in humans and livestock.
  
  
  
  Tsetse distribution and trypanosome infections were studied using traps and fixed fly rounds located at 10 km intervals along a 110 km long transect straddling the southern escarpment of the Zambezi Valley. Three km long fly rounds were conducted on 12 sites, and were repeated 11 times over a 7-month period. Additional traps were deployed and monitored in selected sites. Microscopic examination of 2092 flies for trypanosome infections was conducted.
  
  
  
  Surveys confirmed the presence of G. morsitans morsitans and G. pallidipes in the Zambezi Valley floor. Moving south, the apparent density of tsetse flies appears to peak in the vicinity of the escarpment, then drops on the highlands. Only one fly was caught south of the old game fence separating protected and settled areas. A trypanosome infection rate of 6.31% was recorded in tsetse flies dissected. Only one infection of the T. brucei-type was detected.
  
  
  
  Tsetse fly distribution in the study area appears to be driven by ecological factors such as variation in land use and altitude-mediated climatic patterns. Although targeted control of tsetse flies have played a role in determining distribution, no major control operations have been implemented in the area for 15 years. Trypanosome infections in tsetse flies are consistent with HAT epidemiological data, which considers the situation to be generally 'low risk'. Nonetheless, underreporting is likely to conceal the true epidemiological picture, and efforts are needed to strengthen the diagnostic capacities of health facilities.
authors.affiliation: Tsetse Control Division, Department of Livestock and Veterinary Services, Ministry of Agriculture, Mechanization and Irrigation Development, Harare, Zimbabwe. shereni2005@yahoo.com.
authors.forename: William
authors.identifier: 0000-0002-9427-4349
authors.initials: W
authors.lastname: Shereni
authors.affiliation: The Royal (Dick) School of Veterinary Studies and the Roslin Institute, University of Edinburgh, Easter Bush Campus, Roslin, UK.
authors.forename: Neil E
authors.initials: NE
authors.lastname: Anderson
authors.affiliation: Tsetse Control Division, Department of Livestock and Veterinary Services, Ministry of Agriculture, Mechanization and Irrigation Development, Harare, Zimbabwe.
authors.forename: Learnmore
authors.initials: L
authors.lastname: Nyakupinda
authors.affiliation: Food and Agriculture Organization of the United Nations, Sub-Regional Office for Eastern Africa, Addis Ababa, Ethiopia.
authors.forename: Giuliano
authors.initials: G
authors.lastname: Cecchi
mesh_terms: D000818:Animals; D005260:Female; D006801:Humans; D007303:Insect Vectors / Q000469:parasitology*; D008297:Male; D014346:Trypanosoma brucei brucei; D014353:Trypanosomiasis, African / Q000453:epidemiology* / Q000469:parasitology / Q000662:veterinary; D014370:Tsetse Flies / Q000469:parasitology*; D015030:Zimbabwe / Q000453:epidemiology
keywords: African animal trypanosomiasis; Epidemiology; Glossina; Sleeping sickness; Tsetse; Zimbabwe