Histopathological, immunohistochemical and polymerase chain reaction diagnosis of Trypanosoma vivax in various organs of experimentally infected Creole sheep.

Trypanosoma vivax is one of the major species implicated in animal trypanosomoses in West Africa, significantly affecting livestock economies in Sub-Saharan Africa and also in endemic regions of South America. Post-mortem diagnosis of T. vivax remains challenging due to non-specific lesions and limitations of conventional parasitological and molecular techniques. This study aimed to evaluate and validate immunohistochemical approaches using polyclonal anti-T. vivax antibodies for the post-mortem diagnosis of T. vivax in formalin-fixed, paraffin wax-embedded tissues of experimentally infected Creole sheep, and to correlate the findings with histopathology and polymerase chain reaction (PCR) results. Twelve organs from three experimentally infected sheep were examined using histology and immunohistochemistry (IHC), and seven organs were additionally analysed by conventional PCR. IHC was performed successfully using two different detection systems targeting T. vivax trypomastigotes within tissue sections. Histologically, T. vivax was detected in various small and medium-sized blood vessels across multiple organs. The protozoan was immunolabelled in the kidneys, rete mirabile, lymph nodes, brain, pancreas, lungs and heart of only two sheep and was detectable in the blood vessels of the liver across all examined animals. This is the first experiment demonstrating immunolabelling of T. vivax in preserved tissues. The PCR findings showed that optimal results were achieved on individual technical triplicates of 100 ng or on a pooled sample of 300 ng. Overall, histology, IHC and PCR showed complementary diagnostic performance. The combined application of these techniques enhances the accuracy of post-mortem diagnosis of T. vivax, particularly under conditions where fresh blood samples are unavailable.