Transmission route-dependent genetic diversity of selected protozoan parasites as reflected by the phylogenetic analysis of the 18S rRNA gene

In this pilot study, the genetic diversity of protozoan parasites was analysed according to their different transmission routes (life cycle strategies), focusing on those species which were recently discovered or molecularly analysed for the first time in Hungary or its geographical region. The results showed that among four apicomplexan parasites (Babesia gibsoni, Cytauxzoon europaeus, Sarcocystis morae and Hepatozoon felis) the latter had the highest genetic diversity as reflected by its 18S rRNA gene sequences showing high (1.75%) maximum intraspecific pairwise distance, and also, based on its phylogenetic clustering. This is probably related to the long evolutionary history of H. felis, the absence of its intravascular division and other life cycle characteristics precluding direct transmission between hosts. On the other hand, among non-apicomplexan protozoa (Trichomonas gallinae, Pentatrichomonas hominis, Tritrichomonas foetus and Acanthamoeba castellanii), the latter proved to have the highest genetic diversity (7.73%), most likely due to its long evolutionary history, lateral gene transfer, homologous recombination and the absence of direct host-to-host dispersal. Transmission mode had a significant impact on the genetic diversity among protozoan parasites, depending on life cycle strategies and consequent frequency/chance of sexual reproduction vs binary fission. In particular, the absence of direct transmission between hosts is a common trait of H. felis and A. castellanii, contributing to their high genetic diversity.