Establishment of a Chronic Trypanosoma Equiperdum Infection Model in Mice

Dourine, caused by chronic infection with Trypanosoma equiperdum, is one of the African trypanosomiasis in equids. Since the pathogenesis of dourine has not yet been elucidated, experimental studies using mouse infection models are needed. However, mice cannot be infected with most T. equiperdum strains or rapidly develop parasitemia if infection is established and die within a few days. A sequential method of isolating parasites from dourine-affected horses and adapting them to in vitro cultures using soft agarose media was recently developed. Various T. equiperdum strains adapted to in vitro conditions have since been established using this technique. We used one of these strains, the T. equiperdum IVM-t2 strain. In the present study, we inoculated mice with the IVM-t2 strain and successfully produced a chronic infection model in mice. In the clinical examination, periodic parasitemia and skin plaques, which are characteristic clinical signs of dourine-affected horses, were observed. A histopathological examination revealed that some of the lesions observed in infected horses, such as vaginitis, trypanosomal sand, and peripheral neuritis, were reproduced in mice. This mouse model will be a valuable tool for pathological, immunological, and parasitological in vivo research, and will contribute to investigations on the mechanisms underlying the disease process and the host-protozoa relationship.

Humoral immune response and delayed-type hypersensitivity in rabbits infected with Trypanosoma equiperdum

Trypanosoma equiperdum is the causative agent of dourine, a parasitic venereal disease of equids. In this work, rabbits were infected with T. equiperdum strain OVI; serological tests (complement fixation test, ELISA and immunoblotting), used for the diagnosis of dourine in horses, were applied to study rabbit humoral immune response and to characterise T. equiperdum antigen pattern recognised by antibodies from infected rabbits. Moreover a protein extract of T. equiperdum strain OVI was produced and tested in skin tests on infected rabbits to detect the cell-mediated response induced by T. equiperdum, in order to evaluate its use in the field diagnosis of dourine. Sera of infected rabbits recognized in immunoblotting Trypanosoma protein bands with molecular weight below 37 kDa, providing a serological response comparable with that already observed in dourine infected horses. Moreover the trypanosome protein extract was capable to produce in vivo delayed-type hypersensitivity (DHT Type IV) in rabbits and proved itself to be non-toxic and non-sensitizing.