Résumé
Animal African Trypanosomosis, caused by protozoan blood parasites mainly transmitted by Glossina, is a threat to livestock health in Africa. Whilst African zebu and European taurine suffer from trypanosomosis, West African taurine, such as N'Dama, exhibit trypanotolerance and remain productive in enzootic areas. Trypanosomosis affects haematological and biochemical variables in cattle. However, joint characterization of the temporal dynamics of these variables during trypanosomosis in tolerant or susceptible cattle had yet to be carried out. The purpose of this study was to show potential differences in the dynamics of profiles of haematological and biochemical variables between trypanotolerant and susceptible cattle breeds during an infection by Trypanosoma congolense. Three cattle breeds comprising N'Dama, West African Fulani zebu, and crossbred cattle (West African zebu x European taurine) were infected with Trypanosoma congolense and were monitored for six months post-infection.
As expected, N'Dama controlled anaemia and parasitaemia better than Fulani zebu and crossbred cattle. Lymphocytosis and monocytosis were observed in N'Dama, while lymphocyte and monocyte counts remained unchanged in Fulani zebu and crossbred cattle. Granulocyte counts decreased in Fulani zebu and crossbred cattle, but remained stable in N'Dama. Cholesterol and glucose concentrations decreased significantly after inoculation with trypanosomes, but relative variations were observed depending on the breed, with rapid recovery of cholesterol levels in N'Dama. The relative variation in haematological variables was positively correlated with those of cholesterol and glucose, and negatively correlated with parasitaemia. Parasitaemia was also negatively correlated with variations in cholesterol and glucose levels.
This study highlighted some striking differences in the evolution of white blood cells and certain biochemical traits in trypanotolerant N'Dama cattle in comparison with susceptible breeds. These associations indicated likely physio-pathological links between trypanotolerance, characterized by the mitigation of symptoms, anaemia and parasitaemia, an efficient immune response, exemplified by white blood cell profiles, and limitation of some metabolic disorders.