The burden and spatial distribution of bovine African trypanosomes in small holder crop-livestock production systems in Tororo District, south-eastern Uganda

Abstract

Background: African animal trypanosomiasis (AAT) is considered to be one of the greatest constraints to livestock production and livestock-crop integration in most African countries. South-eastern Uganda has suffered for more than two decades from outbreaks of zoonotic Human African Trypanosomiasis (HAT), adding to the burden faced by communities from AAT. There is insufficient AAT and HAT data available (in the animal reservoir) to guide and prioritize AAT control programs that has been generated using contemporary, sensitive and specific molecular techniques. This study was undertaken to evaluate the burden that AAT presents to the small-scale cattle production systems in south-eastern Uganda.

Methods: Randomised cluster sampling was used to select 14% (57/401) of all cattle containing villages across Tororo District. Blood samples were taken from all cattle in the selected villages between September-December 2011; preserved on FTA cards and analysed for different trypanosomes using a suite of molecular techniques. Generalized estimating equation and Rogen-Gladen estimator models were used to calculate apparent and true prevalences of different trypanosomes while intra cluster correlations were estimated using a 1-way mixed effect analysis of variance (ANOVA) in R statistical software version 3.0.2.

Results: The prevalence of all trypanosome species in cattle was 15.3% (95% CI; 12.2-19.1) while herd level trypanosome species prevalence varied greatly between 0-43%. Trypanosoma vivax (17.4%, 95% CI; 10.6-16.8) and Trypanosoma brucei rhodesiense (0.03%) were respectively, the most, and least prevalent trypanosome species identified.

Conclusions: The prevalence of bovine trypanosomes in this study indicates that AAT remains a significant constraint to livestock health and livestock production. There is need to implement tsetse and trypanosomiasis control efforts across Tororo District by employing effective, cheap and sustainable tsetse and trypanosomiasis control methods that could be integrated in the control of other endemic vector borne diseases like tick-borne diseases.

Figure 1

Prevalence of T.brucei s.l. in cattle in 57 villages of Tororo District, Uganda. T.brucei s.l. prevalence was categorized into five classes for which symbols differ in size and colour. County boundaries were included for ease of assessment of the location of sample sites within the district. The estimated number of cases per 100 animals is presented within the symbols. Only names of villages with the highest prevalence estimates are added.

Figure 2

Spatial distribution of bovine trypanosome species and land cover. The overall prevalence of different trypanosome species in each village was categorized into five classes for which symbols differ in size and colour. County boundaries were included for ease of assessment of the location of sample sites within the district. The estimated number of cattle infected with different trypanosome species per 100 animals are presented within the symbols. Only name labels of villages with the highest prevalence estimates were added to avoid overcrowding the map. A background layer of land cover classes (GLC2000) was added to assess the likely effect of land use on trypanosome prevalence.