Comparative Pathogenicity and Semi-quantitative Multi-organ Histopathology of Trypanosoma congolense and Trypanosoma brucei Infection in Mice

Background

African animal trypanosomosis remains a persistent constraint on livestock production in sub-Saharan Africa, yet the combined influence of parasite species, inoculation route and host immune response on disease severity has rarely been examined within a single controlled experiment. We compared Trypanosoma congolense and Trypanosoma brucei infections in BALB/c mice following intraperitoneal or intramuscular inoculation. Four infected groups of fifteen mice and five uninfected controls were followed for parasitaemia, body weight, rectal temperature and survival. Packed cell volume, endpoint haematological indices, serum IFN-γ and IL-10 concentrations, and semi-quantitative liver, spleen and kidney pathology scores were assessed.

Results

Survival differed markedly between groups (log-rank p < 0.0001). Intraperitoneal T. congolense infection had the shortest median survival of nine days, whereas intramuscular T. brucei infection showed the longest survival among the infected groups. Patency and peak parasitaemia were broadly comparable, indicating that parasite burden did not correspond to the observed survival differences. Infected animals showed anaemia and thrombocytopenia. IFN-γ was higher in infected animals than in controls but did not distinguish the four infected groups. IL-10 showed a stronger species-associated pattern, with higher concentrations in T. congolense-infected mice than in T. brucei-infected mice. Liver, spleen and kidney pathology scores were significantly higher in infected animals than in controls but did not differ significantly among the infected groups.

Conclusions

Parasite species and inoculation route influenced the tempo of experimental murine trypanosomosis. These discordances between survival, parasitaemia, lesion severity and cytokine profiles suggest that species-associated host responses may contribute to disease outcome, although further mechanistic investigation is required.