Comparative parasitaemia and haematology of mice, rats and rabbits experimentally infected with Trypanosoma brucei brucei and their responses to diminazene diaceturate (Veriben®) therapy

ObjectiveTo compare parasitaemia and haematological changes of Trypanosoma brucei brucei infection in mice, rats and rabbits and their chemotherapeutic responses to diminazene diaceturate (Veriben®) therapy under the same experimental conditions.MethodsA total of 20 adult BALB/c mice, 20 Wister albino rats and 20 New Zealand rabbits of both sexes were used for this study. Each rodent group was divided into four groups (A, B, C and D) of five animals each. Animals in Groups A and C were individually infected with 0.5 mL of blood from donor rats containing 1.5 × 106Trypanosoma brucei brucei, while Groups B and D remained uninfected. Experimental animals were treated thus [Group A (infected and untreated control), Group B (uninfected and untreated control), Group C (infected and treated) and Group D (uninfected and treated)]. All treatments commenced 12 days after infection. Parasitaemia and haematological parameters were determined every four days till the end of the experiment.ResultsThe prepatent period for mice and rats was 4 days while that of rabbits was 8 days. Observed clinical signs consisted of pallor of mucous membranes, lethargy and starry hair coat observed mainly among mice and rats, while the rabbits had mainly mild pallor of the ocular mucous membranes. Parasitaemia in Groups A rose significantly by Day 20 post-infection (p.i.) in the mice, Day 24 in the rats and Day 28 in rabbits. By these respective days, all the infected untreated animals in Group A died of the infection. However in Group C, parasitaemia declined significantly (P < 0.05) among mice, rats and rabbits and were completely eliminated from peripheral circulation by Days 20, 20 and 24 (p.i.) respectively, with no death. An inverse relationship was observed between parasitaemia and the haematological parameters for all the species of the rodents. As parasitaemia increased, the packed cell volume, red blood cell count, haemoglobin concentrations and white blood cell counts of mice, rats and the rabbits experienced a significant decline (P < 0.05) in Group A, leading to anaemia. These decline in haematological parameters were however the most severe in rats and mice than in rabbits.ConclusionsMice and rats are better animal models for studying the progression of the disease than rabbits and diminazene diaceturate (Veriben®) is capable of eliminating parasitaemia and modulating haematological changes in mice, rats and rabbits.