The relationship between the parasitological prevalence of trypanosomal infections in cattle and herd average packed cell volume

The relationship between prevalence of trypanosomal infections (Trypanosoma congolense) and average packed cell volume (PCV) in herds of communally ma naged adult Angoni breed cattle was investigated in four districts of easte rn Zambia. In all areas, regression analyses showed that the herd average P CV decreased with increasing prevalence of trypanosomal infections. The slo pe of the equation between average PCV and trypanosome prevalence decreased with increasing prevalence of trypanosomal infections. For the same increa se in prevalence of trypanosomal infection, the decrease in herd PCV was hi gher in the areas with low to medium prevalence. Season of sampling also de termined the slope of the regression equation. For the same increase in pre valence of trypanosomal infection. the decrease in herd PCV was higher duri ng the dry compared to the rainy season suggesting that trypanosomosis is l ess well tolerated during the dry season. Results from the study suggest th at the relationship between the prevalence of trypanosomal infections and h erd average PCV could be a useful tool in the management of trypanosomosis and planning of its control. Reasons for the spatial and temporal variation s in the relationship are discussed. (C) 2001 Elsevier Science B.V. All rig hts reserved.