Biochemical indicators of host response to natural trypanosomosis infection in indigenous Zebu cattle in Apac district, Northern Uganda

Abstract

Animal African Trypanosomosis (AAT) affects livestock production in sub–Saharan Africa with an annual financial burden of approximately $4 billion. Some cattle breeds have shown a degree of resistance to trypanosome infection, the so-called “trypanotolerance” phenotype. Breeding for trypanotolerance is a plausible approach to avert overdependence on chemotherapy and the related high costs of trypanocidal drugs. There is a need to identify biochemical markers of trypanotolerance to aid in the selective breeding for trypanotolerant animals. A cross-sectional study was carried out to collect samples from trypanosome infected and non-infected animals living in the same endemic district. A total of 1,726 cattle from 12 sites located in 4 sub counties of Apac district, Uganda, were screened for AAT. Whole blood and serum were collected for which hematological, clinical chemistry and cytokine profiling in relation to presence (or absence) of trypanosomes and the corresponding parasitaemia. PCR was executed to identify the infecting trypanosome species and reinforce the negative status of controls. The overall prevalence of AAT in the cattle in Apac district by microscopy detection was 7.9% (136/1726). ITS1 PCR analysis revealed that mono-species infections ( Trypanosoma brucei , T. congolense or and T. vivax ) represented 58% (68/117) of all infections, while mixed infections accounted for 42% (49/117). We identified 6 “trypanotolerant-like” (High parasitaemia but near-normal PCV), 6 susceptible (Parasitaemia with Low PCV) and compared these to 6 uninfected controls (normal PCV, no Tryps). Significant variation (ANOVA p < 0.05) was observed in the trypanotolerant-like, susceptible and control animals in the plasma levels of Albumin (ALB), Bilirubin (TBIL, DBIL), Creatinine (CREA) and Cholesterol (CHOL). Screening for trypanotolerance characteristics in naturally exposed animals is useful to identify deterministic serum/plasma biochemical markers that could be deployed to guide trypanotolerance selective breeding programs.