Interaction between Trypanosoma brucei and Haemonchus contortus infection in West African Dwarf Goats
In order to investigate the immunomodulatory influence of concurrent T. brucei and H. contortus infection in West African Dwarf (WAD) goats, 28 infected and 7 uninfected (control) of 8-9 months old male WAD goats were studied. The infected goats were separated into resistant (Class 1) and susceptible (Class 2) Faecal Eggs Count (FEC) phenotypes. They were infected with 3000 infective larvae (L3) of H. contortus and 5 x 106T. brucei. Another group of these phenotypes received only the H. contortus challenge. The responses were measured by parasitological response through FEC and Worm Burden (WB), and by host immune response through IgG levels. Class 2 animals with or without T. brucei infection exhibited non-significant (P > 0.05) higher FEC compared to those of Class 1. Worm burdens were not significantly different between FEC classes but were different (P=0.038) in relation to T. brucei infection. There was an overall increase in worm burdens of T. brucei infected goats, more pronounced in Class 2 than in Class 1. There was a significant upward drift of antibody levels with time across all groups without significant interactions. However, there was a significant effect of FEC Class (P=0.017) and trypanosome infection (P=0.041) with no significant interaction. Animals in Class 1 had generally higher antibody levels than those in Class 2, irrespective of T. brucei infection. Infection status had a highly significant (P=0.0001) effect on IgG. H. contortus only infected goats had the highest antibody levels and trypanosome infection reduced this response, irrespective of FEC phenotype. There was a highly significant (P=0.001) positive correlation (r = +0.719) between FEC and total worm counts. This work showed that the two response phenotypes identified in earlier immunizing infections were still clearly recognizable following homologous challenge and dual infections. This suggests that under field conditions where repeated H. contortus challenge occurs and trypanosomosis is endemic, the phenotypes could remain unchanged.
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Keywords: Haemoparasite, Gastrointestinal parasite, concurrent infection, immune response, domestic animals