Abstract

In Venezuela Trypanosoma evansi is responsible for trypanosomosis that affects equines, canines, bovines and wild animals such as capybaras. The pathology of the infections by this monomorphic trypanosome has been extensively studied by different authors in experimental and field conditions at level of light and electron microscopy. The aim of this study is to provide additional evidences about the development of an intracellular stage during experimental infections of albino mice with a Venezuelan isolated from Apure state. Samples of different organs from mice experimentally infected with 10⁴ trypanosomes were prepared for transmission and scanning electron microscopy. Results show the presence of T. evansi in the lumen of blood vessels and interacting with endothelial cells, Küpffer cells, macrophages, lymphocytes and neutrophils. A frequent finding was the detection of intracellular trypomastigotes in the cytoplasm of normal looking and necrotic cells of the adrenal cortex, liver, capillaries and spleen. Despite most of the intracellular trypomastigotes observed, presented the ultrastructural feature of trypomastigotes from subgenus Trypanozoon, only a very few number of trypanosomes showed an ultrastructure compatible with an epimastigote-like. Most of trypanosomes presented a normal ultrastructure, however ultrastructural patterns suggestive of apoptosis could also be evidenced. Results are discussed in the context of their impact in the diagnosis, treatment of the disease, evasion of immune system, immunosuppression as well as the persistence and prevalence of T. evansi in natural hosts.

Keywords: Experimental infection; Mice; Trypanosoma evansi; Venezuelan isolated; EcHF91; Intracellular stages; Trypomastigotes; Epimastigotes-like; Apoptosis; SEM; TEM