Genetic variability and infective ability of the rabbit trypanosome, Trypanosoma nabiasi Railliet 1895, in southern Spain.

Trypanosomes are widespread haemoflagellate protozoans, commonly found in all groups of vertebrates and usually transmitted by arthropods. Non-pathogenic species are those that cause little or no apparent negative effects in the host and it is accepted that Trypanosoma nabiasi is the species that infects the domestic and wild rabbit, Oryctolagus cuniculus. Knowledge about genetic variability, in vitro cultivation and infectivity of this parasite is very scarce, so the aim of this study was to provide an insight on them. The parasite was detected in all the type of samples of 121 wild rabbits. Epimastigotes were visualized and isolated from all the organ cultures types except from skin, and twenty-six strains were isolated and grown in mass. Epimastigote infectivity was assessed in vitro and in vivo. Amastigotes were obtained in infected macrophages from cultured epimastigotes. Furthermore, trypomastigotes were found in the peripheral bloodstream of an experimentally infected naïve domestic rabbit with cultured epimastigotes at the fourth day after infection. The rising titre of antibodies led to the disappearance of the parasite from blood. In addition, this study reports the existence of two T. nabiasi genetic lineages in southern Spain. Phylogenetic analysis places T. nabiasi in the same clade as T. lewisi and other rodent trypanosomes of the subgenus Herpetosoma.