Discussion

Aims: To determine: 1) prevalence of Trypanosoma brucei, and whether this had changed since the time of last evaluation (in 2006) in the Sambel Kunda, Central River Division of the Gambia, West Africa; and 2) the effect of T. brucei infection on BCS and clinicopathological parameters. Methods: All horses and donkeys competing at the Gambia Horse and Donkey Trust annual show, in December 2010, were examined. Jugular blood samples were collected for measurement of PCV/TSP. Direct buffy coat and blood smears were examined for presence of fixed trypanosomes (graded 0 - 3) and to determine total and differential white count by an operator blinded to the results of serology or to any clinical data. Samples of serum were frozen until immunofluorescence antibody testing (IFAT) for T. brucei was performed. Results: Complete data sets were obtained from 72 donkeys and 29 horses. Active trypanosome infection was documented in 27 donkeys and 8 horses (prevalence 35%). Seroconversion to T. brucei was documented in 43 donkeys and 24 horses (prevalence 68%). In 6 donkeys equivocal results to IFAT with concurrent parasitaemia suggested the presence of an early infection prior to seroconversion. A Mann Whitney test revealed significant reduction in PCV between grade 3 infestation (P<0.001) and grade
2 infestation (P<0.005) when compared to uninfected controls.
Conclusions: The findings of this study suggest that T. brucei is highly prevalent in apparently healthy horses and donkeys in the Gambia, and that this level has increased over the last 5 years such that the majority of the population is infected. Practical significance: Low level trypanosome parasitaemia may not be associated with overt evidence of disease, but higher grades are associated with marked anaemia. Acknowledgements: The Gambia Horse and Donkey Trust, The University of Glasgow.