Pathogenicity of Ethiopian Trypanosoma evansi Type A and B in Swiss Albino Mice Model
Surra caused by Trypanosoma evansi is one of the important pathogenic parasitic diseases of camels, equines, other domestic and wild animals. T. evansi type A is endemic to Africa, Latin America, and Asia while T. evansi type B is so far identified only in Ethiopian and Kenyan camels. Little is known about the pathogenicity of T. evansi. This study was conducted to determine the pathogenicity of T. evansi type A and B in Swiss albino mice colony. We genetically characterized two T. evansi type A and two T. evansi type B isolated from camels in Tigray and Afar. Six mice were infected by each of the isolates and compared with 6 uninfected mice (control). Parasitemia was followed on Matching Method. Weight and PCV of each mouse were measured pre-infection and after 6 days post-infection. Each mouse was examined for visible clinical signs. Highly parasitaemic mice were euthanized on diethyl ether to collect vital organs for gross and histopathologic examination. Major clinical signs in infected mice were rough hair coats, pale mucous membranes of the eye, and incoordination. Compared to the control, there were no significant reductions in the body weight of mice (T. evansi type A, p= 0.493, T. evansi type B, p=0.299), but there was significant reduction in the mean PCV values in both T. evansi type A (p= 0.0001) and T. evansi type B (p= 0.0008) stocks. Splenomegaly, hepatomegaly, edema and pneumonia were the prominent lesions observed at necropsy. Microscopic lesions seen in vital organs were congestion, capillaries distended with red blood cells, cellular infiltration, accumulation of hemosiderin, necrosis and degenerative changes. The clinical signs and gross and histopathologic lesions were comparable between mice infected by T. evansi type A and B. In conclusion, T. evansi type A and B showed similar in vivo pathogenicity. As a result, a special model for comparative pathological study on host-trypanosome interaction is essential.