Trypanosoma evansi and T. equiperdum: distribution, biology, treatment and phylogenetic relationship (a review)

Adaptations of Trypanosoma brucei to gradual loss of kinetoplast DNA: Trypanosoma equiperdum and Trypanosoma evansi are petite mutants of T. brucei

“…No maxicircle genes could be amplified from three other strains labeled as T. equiperdum (American Type Culture Collection nos. ATCC30023, STIB784, and AnTat 4.1; Table 2), yet the presence of maxicircle genes is the only molecular feature that would distinguish T. equiperdum from T. evansi (6,9,12). The absence of the maxicircle genes in all tested T. evansi strains was anticipated (Table 2).…”

“…For Ͼ100 years T. brucei, T. equiperdum, and T. evansi have been considered separate species, based on differences in the mode of transmission, host range and pathogenicity, and longstanding understanding that T. equiperdum retains at least a part of maxicircle kDNA, whereas T. evansi completely lost it (6,9,12). Our data show that the Dk/Ak strains of T. equiperdum and T. evansi have evolved from T. brucei after losing the capacity to faithfully replicate their kDNA.…”

“…Apart from causing different clinical diseases, T. equiperdum (dourine) and T. evansi (surra) differ only in that the former contains at least fragments of kDNA maxicircles (Dk), missing from T. evansi (Ak). Hundreds of studies on the epidemiology, pathology, and prevalence of both diseases have been published (6,9,13). Yet the existence of T. equiperdum has been questioned, because no new strains have been isolated for a long time (ref.…”

“…The reduction of a heteroxenous life cycle to a monoxenous one has had dramatic consequences, such as the elimination of the tsetse vector (or any other similar insect vector) from the life cycle, which paradoxically allowed trypanosomes to leave the African tsetse belt and spread to other continents (8). Recombination or genetic exchange does not occur in Dk/Ak trypanosomes (6,9).…”

“…A widely accepted paradigm holds that T. evansi evolved, via T. equiperdum, when camels infected with T. brucei moved to tsetsefree areas (10). T. equiperdum and T. evansi are responsible for dourine and surra, respectively, economically significant diseases infecting horses, camels, and water buffaloes, transmitted in the BS by bloodsucking insects or coitus (9). Surra is the most widespread and serious disease of camels.…”