A COMPARATIVE STUDIES ON THE INFECTIVITY AND PATHOGENICITY OF EXPERIMENTAL TRYPANOSOMA BRUCEI BRUCEI INFECTION IN MICE, RATS, RABBITS AND GUINEA FOWLS
The study compared the infectivity and pathogenecity of experimental Trypanosoma bruceibrucei infection in mice, rats, rabbits and guinea fowls. A total of 10 each of the following animals‟ mice, rats, rabbits and guinea fowls of both sexes were used for the study. Each group of the animal species was divided into two groups (infected and control) of five animals each. The mice, rats, rabbits and guinea fowls in the infected groups were individually inoculated with blood containing 1 x106Trypanosoma brucei brucei (Fadere stock). All animals in the control groups were not infected. Patent parasitaemia as determined by haematocrit centrifugation technique was between 3-4 days in the mice and rats, while it was 7-8 days in rabbits. No parasitaemia was seen in the infected Guinea fowl throughout the study. The mean body weights of mice, rats and rabbits decreased in the infected group as compared to the control group. All animals in the infected group with the exception of guinea fowls showed increase in body temperature. In the mice and rats there were significance diferrences (SD) (p < 0.05) in the overall mean PCV, HGB and RBC between the infected groups (IG) as compared to the control group (CG). In the rabbits there were SSD (P < 0.05) in the overall mean PCV, HGB and RBC between the IG (36.1 ± 0.6%, 12.11 ± 0.8 g/dl and 5.9 ± 0.4×106) and CG (43.7 ± 0.5%, 14.1 ± 0.9 g/dl and 7.23 ± 0.3×106 respectively). There was no SD (P > 0.05) between the overall mean PCV, HGB and RBC of the infected guinea fowls and those of the control group throughout the period of the experiment. Also, no mortality was recorded among the infected guinea fowls as consequence of the infection. A decrease in mean total white blood cell (WBC) counts of the rats and the rabbits were observed while mice and guinea fowls groups showed no significance difference between the WBC of the infected and control groups. Microscopic lesions observed in the mice, rats and rabbits included congested central vein and perivascular cuffing, congestion and mononuclear cellular infilteration around blood vessels of the lungs, depletion of lymphoid cells, congested inter tubular spaces and focal necrosis of renal tubular epithelium. In the guinea fowls, the spleen revealed heamosiderosis. The study thus demonstrated that mice, rats and rabbits are, in order of susceptibility better laboratory models than the guinea fowls which tend to show some measure of resistance to Trypanosoma brucei brucei used in the experiment. Therefore rabbits could be use in our laboratory to preserve Trypanosoma brucei brucei.
1.1 Background of the Study
Trypanosomosis is a disease of man, domestic (Fajinmi et al., 2011; WHO 2015) and wild animals (Abenga et al., 2006; Mbaya et al., 2009; 2011). It is transmitted by tsetse flies (Glossina spp.) and characterized by anaemia, oedema, cachexia, intermittent fever and death (Yakubu et al., 2014). In Africa including Asia and South America it is transmitted by several biting flies like Tabanus, Hippobosca, Stomoxys (WHO 2015; Yakubu et al., 2014).
The Trypanosoma species affecting man and his domestic animals have been subdivided into two groups, the haematic group (Trypanosoma congolense, T. vivax) which remain in the blood plasma and the tissue invading group (T. brucei brucei, T. brucei gambiense, T. brucei rhodesiense and T. equiperdum) that are found in extra and intra vascular spaces (Abubakar et al., 2005; Chretien and Smoak, 2005; Ngure et al., 2008). Because of their presence in the blood, these invading parasites produce numerous changes in the cellular and biochemical constituents of blood (Taiwo et al., 2003). Infection with Trypanosoma brucei infection like other Trypanosoma infection precipitate red blood cell destruction which results in anaemia as well as tissue damage (Ekanem and Yusuf, 2008; Akanji et al., 2009).
Clinically, the effects of trypanosomosis in animals range from anaemia, immunosuppression, depression with inability to rise, pyrexia directly associated with parasitaemia, paleness of mucous membrane, rapid pulse beat, retarded growth, roughness of haircoats. Reduced capacity to work leading to morbidity and mortality in the absence of treatment (Batista et al., 2012; Silva et al., 2013).
In addition are enlargement of peripheral lymph nodes, reduced milk production, low meat quality, and weight loss as well as reproductive disorders such as infertility, abortion, stillbirth.