Self-cure of Trypanosoma brucei brucei infection in West African Dwarf sheep

Abstract

This study investigated the natural course of parasitaemia in West African Dwarf (WAD) sheep experimentally infected with Trypanosoma brucei brucei parasites and the potential for spontaneous regression without any therapeutic intervention. Ten (10) adult West African Dwarf sheep of both sexes were assigned to two groups of five sheep each. One of the groups was inoculated with approximately 1× 106 trypanosome parasites per animal, intravenously, while the second group served as uninfected control. Blood samples were collected daily until parasitaemia was established and for 7 days post establishment of parasitaemia and thereafter weekly till the end of the experiment in order to monitor the course of parasitaemia. The clinical signs, packed cell volume (PCV) and rectal body temperature were monitored. A pre-patent period of 28 days was observed with peak mean parasitaemia of 81.60 ± 27.71 million trypanosome parasites, on day 43 post inoculation. The parasitaemia declined in 60 % of the sheep from day 141 post-infection (PI) and reduced to 0.34±0.02. Clinical signs observed include weakness, mild anorexia and pale mucous membranes. The 40 % of animals that manifested clinical signs eventually died and their postmortem findings were indicative of severe anaemia and dehydration. Monitoring the sheep which recovered (for parasitaemia and clinical signs) up to 141 days PI showed there was no relapse. The Trypanosoma b. brucei infected WAD sheep used in the study were able to contain both parasitaemia and fever and recovered from the infection.