Host specificity, pathogenicity, and mixed infections of trypanoplasms from freshwater fishes

This work summarizes the results of the 8-year study focused on Trypanoplasma sp. parasitizing freshwater fishes in the vicinity of Kyiv, Ukraine. Out of 570 fish specimens of 2 different species analyzed, 440 individuals were found to be infected. The prevalence of infection ranged from 24 % in Abramis brama Linnaeus (freshwater bream) to 100 % in Cobitis taenia Linnaeus (spined loach). The level of parasitemia also varied between moderate in freshwater bream and very high in spined loach. Interestingly, no clinical manifestations of trypanoplasmosis were observed even in extremely heavily infected C. taenia. We hypothesize that different species may differ in evolutionary timing allowing for reciprocal adaptation of the members of the "host-parasite" system. Molecular analysis of the 18S rRNA sequences revealed that several specimens were simultaneously infected with at least two different trypanoplasm species. To the best of our knowledge, this is the first report of the mixed infection with fish trypanoplasms.

Molecular taxonomy of the suborder Bodonina (Order Kinetoplastida), including the important fish parasite, Ichthyobodo necator

Ichthyobodo necator is an important fish ectoparasite with a broad host and ecological range. A novel method, involving the use of an anesthetic, allowed the collection of large numbers of parasites from the skin and gills of hybrid striped bass (Morone saxatilis male x M. chrysops female). Genomic DNA from these samples was used to amplify and clone the 18S rRNA gene. The 18S rRNA gene was similarly cloned from Bodo caudatus, Bodo edax, Bodo saltans, an unidentified Bodo species, and Dimastigella trypaniformis. The resulting sequences were aligned with other representative kinetoplastid species using pileup and similarities in secondary structure. Phylogenetic relationships within the suborder Bodonina and representatives of the suborder Trypanosomatina were determined using maximum-likelihood statistics. The phylogenetic analyses strongly supported the order Kinetoplastida as a monophyletic assemblage consisting of at least two major lineages. One lineage consisted exclusively of L. necator, indicating that it may represent a new suborder. The second lineage consisted of all other kinetoplastid species. This second lineage appeared to contain at least 8 bodonine sublineages, none of which correlated with currently recognized families. For three sublineages, there was a close correspondence between the 18S phylogeny and the classical taxonomy of Dimastigella, Rhynchobodo, and Rhynchomonas. In contrast, Bodo and Cryptobia were polyphyletic, containing species in two or more sublineages that may represent separate genera.

Growth, morphology and division of flagellates of the genus Trypanoplasma (Protozoa, Kinetoplastida) in vitro

Nine strains of trypanoplasms were grown in axenic culture. Cultures of Trypanoplasma borreli Laveran and Mesnil, 1901 from fish hosts Blicca bjoerkna, Cyprinus carpio, Scardinius erythrophthalmus and Tinca tinca and of T. guerneyorum Minchin, 1909 from Esox lucius and Trypanoplasma spp. from the leech Piscicola geometra were maintained in biphasic blood-agar medium SNB-9 supplemented with vitamins and antibiotics. In culture, the flagellates transformed into smaller, elongated stages with a little-developed undulating membrane and into short flagella that were morphologically similar to stages in the leech vector. The cultures were passaged weekly at 17-20 degrees C, but they also grew at 4 degrees C. The flagellates divided by binary fission, which was initiated by the formation of two new anterior flagella. The original anterior flagellum of the mother individual was gradually apposed to the cell surface and became the recurrent flagellum of one of the daughter individuals. In the meantime, nuclear division took place, followed by transverse cleavage of the kinetoplast. The division was completed by longitudinal fission of the mother individual into two offspring. Multiple fission that resulted in rosettes, which then cleaved into several daughter cells, was also observed, as well as some dyskinetoplastic and other anomalous forms. In cultures isolated from tenches with high parasitaemia, non-dividing, long filiform stages were observed. Culture stages were not infective for susceptible fishes.