Jan Votýpka

Kinetoplast DNA Network: Evolution of an Improbable Structure

Kinetoplast DNA (kDNA) is the most structurally complex mitochondrial DNA in nature. Unique to the single mitochondrion of unicellular flagellates of the order Kinetoplastida, kDNA is best known as a giant network of thousands of catenated circular DNAs (an electron micrograph of a network is shown

A Historical Overview of the Classification, Evolution, and Dispersion of Leishmania Parasites and Sandflies

Background The aim of this study is to describe the major evolutionary historical events among Leishmania, sandflies, and the associated animal reservoirs in detail, in accordance with the geographical evolution of the Earth, which has not been previously discussed on a large scale. Methodology and Principal Findings Leishmania and sandfly classification has always been a controversial matter, and the increasing number of species currently described further complicates this issue. Despite several hypotheses on the origin, evolution, and distribution of Leishmania and sandflies in the Old and New World, no consistent agreement exists regarding dissemination of the actors that play roles in leishmaniasis. For this purpose, we present here three centuries of research on sandflies and Leishmania descriptions, as well as a complete description of Leishmania and sandfly fossils and the emergence date of each Leishmania and sandfly group during different geographical periods, from 550 million years ago until now. We discuss critically the different approaches that were used for Leishmana and sandfly classification and their synonymies, proposing an updated classification for each species of Leishmania and sandfly. We update information on the current distribution and dispersion of different species of Leishmania (53), sandflies (more than 800 at genus or subgenus level), and animal reservoirs in each of the following geographical ecozones: Palearctic, Nearctic, Neotropic, Afrotropical, Oriental, Malagasy, and Australian. We propose an updated list of the potential and proven sandfly vectors for each Leishmania species in the Old and New World. Finally, we address a classical question about digenetic Leishmania evolution: which was the first host, a vertebrate or an invertebrate? Conclusions and Significance We propose an updated view of events that have played important roles in the geographical dispersion of sandflies, in relation to both the Leishmania species they transmit and the animal reservoirs of the parasites.

Diversity and phylogeny of insect trypanosomatids: all that is hidden shall be revealed

Monoxenous trypanosomatids, which are usually regarded as benign dwellers of the insect alimentary tract, represent a relatively obscure group within the family Trypanosomatidae. This field of study has long been in disarray with the genus level taxonomy of this group remaining artificial, species criteria elusive, host specificity and occurrence poorly known, and their diversity mostly unexplored. The time has arrived to remedy this situation: a phylogenetic approach has been applied to taxa recognition and description, and a culture-independent (PCR-based) approach for detection and identification of organisms in nature has made it feasible to study the diversity of the group. Although more than 100 typing units have been discovered recently, these appear to represent a small segment of trypanosomatid biodiversity, which still remains to be uncovered.

Cutaneous leishmaniasis caused by Leishmania infantum transmitted by Phlebotomus tobbi

Transmission of cutaneous leishmaniasis (CL) caused by Leishmania infantum was studied in South Anatolia, Turkey. Small, non-ulcerating lesions prevailed and patients were negative in rK39 tests for antibody detection for human visceral leishmaniasis (VL). The most abundant sand fly species, Phlebotomus tobbi, was found positive for Leishmania promastigotes with a prevalence of 1.4% (13 out of 898 dissected females). The isolated strains were identical with those obtained from patients with CL and were typed as L. infantum. Phylogenetic analysis revealed similarity to MON-188 and a clear difference from the MON-1 clade. Blood-meal identification showed that P. tobbi feeds preferentially on cattle and humans. This finding, the high number of CL patients and relative scarcity of dogs in the focus, suggests that the transmission cycle could be anthroponotic.

Evolution of parasitism in kinetoplastid flagellates

Kinetoplastid protists offer a unique opportunity for studying the evolution of parasitism. While all their close relatives are either photo- or phagotrophic, a number of kinetoplastid species are facultative or obligatory parasites, supporting a hypothesis that parasitism has emerged within this group of flagellates. In this review we discuss origin and evolution of parasitism in bodonids and trypanosomatids and specific adaptations allowing these protozoa to co-exist with their hosts. We also explore the limits of biodiversity of monoxenous (one host) trypanosomatids and some features distinguishing them from their dixenous (two hosts) relatives.

TRANSIENT NATURE OF TOXOPLASMA GONDII-INDUCED BEHAVIORAL CHANGES IN MICE

Many parasites induce specific changes in host behavior that promote the transmission of their infective stages between hosts. Toxoplasmosis in rodents is known to be accompanied by specific behavioral changes (shift in activity level, learning capacity, and novelty discrimination) that can theoretically increase the chance of infected animals being eaten by the definitive host, the cat. However, toxoplasmosis is also accompanied by many pathological symptoms. It is not known whether the behavioral changes are products of manipulation activity of the parasite or only nonspecific by-products of pathological symptoms of toxoplasmosis. Here, we compared the dynamics of development of behavioral and pathological changes in Toxoplasma gondii-infected mice. The results showed that the maximum reduction of mouse activity corresponded with the peak of pathological symptoms, and also that maximum increase of reaction times corresponded with the peak of development of tissue cysts in the brains of infected mice. Behavioral changes were only transient and disappeared before the 12th wk postinoculation. The results suggest that the behavioral changes in infected mice reported by many authors and observed in our experiments could be nonspecific by-products of pathological symptoms of toxoplasmosis rather than specific products of manipulation activity by the parasite.

Trypanosoma avium of raptors (Falconiformes): phylogeny and identification of vectors

Avian trypanosomes are widespread parasites of birds, the transmission of which remains mostly unclear, with various blood-sucking insects mentioned as possible vectors. A search for vectors of trypanosomes of sparrowhawk (Accipiter nisus), buzzard (Buteo buteo), lesser-spotted eagle (Aquila pomarina) and kestrel (Falco tinnunculus) was performed in Czech and Slovak Republics. Black flies (Eusimulium spp.), hippoboscid flies (Ornithomyia avicularia), mosquitoes (Culex pipiens pipiens) and biting midges (Culicoides spp.), trapped while attempting to feed on raptor nestlings, were found to contain trypanosomatids in their intestine. Trypanosomes from the raptors and blood-sucking insects were isolated, and their 18S rRNA sequences were used for species identification and for the inference of intra- and interspecific relationships. Together with the trypanosome isolated from a black fly, the bird trypanosomes formed a well-supported Trypanosoma avium clade. The isolates derived from hippoboscid flies and mosquitoes are most likely also avian trypanosomes infecting birds other than the studied raptors. Analysis of the kinetoplast, that has features characteristic for the avian trypanosomes (minicircle size; dimensions of the kinetoplast disc), provided further evidence for the identification of vectors. It is suggested that all trypanosomes isolated from raptors included in this study belong to the T. avium complex and are transmitted by the ornithophilic simuliids such as Eusimulium securiforme.

Paratrypanosoma Is a Novel Early-Branching Trypanosomatid

The kinetoplastids are a widespread and important group of single-celled eukaryotes, many of which are devastating parasites of animals, including humans. We have discovered a new insect trypanosomatid in the gut of Culex pipiens mosquitoes. Glyceraldehyde-3-phosphate dehydrogenase- and SSU rRNA-based phylogenetic analyses show this parasite to constitute a distinct branch between the free-living Bodo saltans and the obligatory parasitic clades represented by the genus Trypanosoma and other trypanosomatids. From draft genome sequence data, we identified 114 protein genes shared among the new flagellate, 15 trypanosomatid species, B. saltans, and the heterolobosean Naegleria gruberi, as well as 129 protein genes shared with the basal kinetoplastid Perkinsela sp. Individual protein phylogenies together with analyses of concatenated alignments show that the new species, here named Paratrypanosoma confusum n. gen., n. sp., branches with very high support at the base of the family Trypanosomatidae. P. confusum thus represents a long-sought-after missing link between the ancestral free-living bodonids and the derived parasitic trypanosomatids. Further analysis of the P. confusum genome should provide insight into the emergence of parasitism in the medically important trypanosomatids.

Phylogenetic analysis of Sarcocystis spp. of mammals and reptiles supports the coevolution of Sarcocystis spp. with their final hosts

Sequences of the small subunit rRNA genes were obtained for two coccidians, Sarcocystis dispersa and an unnamed Sarcocystis sp. which parasitise the European barn owl and an African viperid snake as their final host, respectively, and share mouse as their intermediate host. Phylogenetic analysis of the sequence data showed that Sarcocystis sp. from the viperid snake is most closely related to another Sarcocystis sp. isolated from an American crotalid snake, while S. dispersa grouped with other bird-transmitted species. The available dataset failed to resolve the evolutionary relationships among four major branches into which all Sarcocystidae and Isospora spp. were split. However, within these branches, the phylogenetic relationships of the majority of analysed members of the genus Sarcocystis reflected coevolution with their final, rather than intermediate hosts.

Leishmania tropica in the black rat (Rattus rattus): persistence and transmission from asymptomatic host to sand fly vector Phlebotomus sergenti

Black rats (Rattus rattus) receiving Leishmania tropica injected intradermally into the ear were studied for the persistence of parasites and infectivity to natural sand fly vector. The mammalian host, the parasite, and the vector all originated from the endemic focus of Urfa, Turkey. Rats did not develop lesions or any apparent signs of disease, although at the site of inoculation they harboured live parasites capable of infecting sand flies. The number of L. tropica amastigotes detected in the inoculated ear by quantitative real-time PCR ranged from 5 x 10(3) to 10(6). Parasite DNA was also present in the tail and contralateral ear, sites distant from inoculation. After feeding on the ears of asymptomatic rats, Phlebotomus sergenti became infected with L. tropica. The average infection rate was 2.9%, and rats were infective for sand flies even 24 months post infection. The infectivity of the vertebrate host for insect vector was therefore not linked to the symptomatic stage of the infection. Such lack of correlation between clinical symptoms and infectivity to sand flies was reported previously for Leishmania infantum, the agent of visceral leishmaniasis; for species causing cutaneous leishmaniasis, however, this is the first evidence of transmission from a host without any visible cutaneous changes. If confirmed in the field, transmission from the asymptomatic host would be of great epidemiological significance.