Trypanosomatid biodiversity in Costa Rica: genotyping of parasites from Heteroptera using the spliced leader RNA gene

Chagas disease in immunocompromised patients

SUMMARYAs Chagas disease remains prevalent in the Americas, it is important that healthcare professionals and researchers are aware of the screening, diagnosis, monitoring, and treatment recommendations for the populations of patients they care for and study. Management of Trypanosoma cruzi infection in immunocompromised hosts is challenging, particularly because, regardless of antitrypanosomal treatment status, immunocompromised patients with Chagas disease are at risk for T. cruzi reactivation, which can be lethal. Evidence-based practices to prevent and manage T. cruzi reactivation vary depending on the type of immunocompromise. Here, we review available data describing Chagas disease epidemiology, testing, and management practices for various populations of immunocompromised individuals, including people with HIV and patients undergoing solid organ and hematopoietic stem cell transplantation.

Multiple and frequent trypanosomatid co-infections of insects: the Cuban case study

Trypanosomatids are obligate parasites of animals, predominantly insects and vertebrates, and flowering plants. Monoxenous species, representing the vast majority of trypanosomatid diversity, develop in a single host, whereas dixenous species cycle between two hosts, of which primarily insect serves as a vector. To explore in-depth the diversity of insect trypanosomatids including their co-infections, sequence profiling of their 18S rRNA gene was used for true bugs (Hemiptera; 18% infection rate) and flies (Diptera; 10%) in Cuba. Out of 48 species (molecular operational taxonomic units) belonging to the genera Vickermania (16 spp.), Blastocrithidia (7), Obscuromonas (4), Phytomonas (5), Leptomonas/Crithidia (5), Herpetomonas (5), Wallacemonas (2), Kentomonas (1), Angomonas (1) and two unnamed genera (1 + 1), 38 species have been encountered for the first time. The detected Wallacemonas and Angomonas species constitute the most basal lineages of their respective genera, while Vickermania emerged as the most diverse group. The finding of Leptomonas seymouri, which is known to rarely infect humans, confirms that Dysdercus bugs are its natural hosts. A clear association of Phytomonas with the heteropteran family Pentatomidae hints at its narrow host association with the insect rather than plant hosts. With a focus on multiple infections of a single fly host, using deep Nanopore sequencing of 18S rRNA, we have identified co-infections with up to 8 trypanosomatid species. The fly midgut was usually occupied by several Vickermania species, while Herpetomonas and/or Kentomonas species prevailed in the hindgut. Metabarcoding was instrumental for analysing extensive co-infections and also allowed the identification of trypanosomatid lineages and genera.

Cultivation of monoxenous trypanosomatids: A minireview

Trypanosomatids are obligatory parasites, some of which are responsible for important human and animal diseases, but the vast majority of trypanosomatids are restricted to invertebrate hosts. Isolation and in vitro cultivation of trypanosomatids from insect hosts enable their description, characterization, and subsequently genetic and genomic studies. However, exact nutritional requirements are still unknown for most trypanosomatids and thus very few defined media are available. This mini review provides information about the role of different ingredients, recommendations and advice on essential supplements and important physicochemical parameters of culture media with the aim of facilitating first attempts to cultivate insect-infesting trypanosomatids, with a focus on monoxenous trypanosomatids.

Parasites of firebugs in Austria with focus on the "micro"-diversity of the cosmopolitan trypanosomatid Leptomonas pyrrhocoris

In this work, we investigated parasites of the firebug Pyrrhocoris apterus in Austria and demonstrated that in addition to the extensively studied Leptomonas pyrrhocoris, it can also be infected by Blastocrithidia sp. and by a mermithid, which for the first time has been characterized using molecular methods. This diversity can be explained by the gregarious lifestyle, as well as the coprophagous and cannibalistic behavior of the insect hosts that makes them susceptible to various parasites. In addition, we showed no tight association of the L. pyrrhocoris haplotypes and geographical locations (at least, considering the relatively small scale of locations in Austria) implying that the natural populations of L. pyrrhocoris are mixed due to the mobility of their firebug hosts.

The Roles of Mosquitoes in the Circulation of Monoxenous Trypanosomatids in Temperate Climates

Monoxenous (insect-restricted) trypanosomatids are highly diverse and abundant in nature. While many papers focus on the taxonomy and distribution of these parasites, studies on their biology are still scarce. In particular, this concerns trypanosomatids inhabiting the ubiquitous mosquitoes. To shed light on the circulation of monoxenous trypanosomatids with the participation of mosquitoes, we performed a multifaceted study combining the examination of naturally- and experimentally-infected insects using light and electron microscopy and molecular identification of parasites. Our examination of overwintering mosquitoes (genera Culex and Culiseta) revealed that their guts contained living trypanosomatids, which can be spread during the next season. Experimental infections with Crithidia spp. demonstrated that imagines represent permissive hosts, while larvae are resistant to these parasites. We argue that for the parasites with wide specificity, mosquitoes act as facultative hosts. Other trypanosomatids may have specific adaptations for vertical transmission in these insects at the expense of their potential to infect a wider range of hosts and, consequently, abundance in nature.

How monoxenous trypanosomatids revealed hidden feeding habits of their tsetse fly hosts

Tsetse flies are well-known vectors of trypanosomes pathogenic for humans and livestock. For these strictly blood-feeding viviparous flies, the host blood should be the only source of nutrients and liquids, as well as any exogenous microorganisms colonising their intestine. Here we describe the unexpected finding of several monoxenous trypanosomatids in their gut. In a total of 564 individually examined Glossina (Austenia) tabaniformis (Westwood) (436 specimens) and Glossina (Nemorhina) fuscipes fuscipes (Newstead) (128 specimens) captured in the Dzanga-Sangha Protected Areas, Central African Republic, 24 (4.3%) individuals were infected with monoxenous trypanosomatids belonging to the genera Crithidia Léger, 1902; Kentomonas Votýpka, Yurchenko, Kostygov et Lukeš, 2014; Novymonas Kostygov et Yurchenko, 2020; Obscuromonas Votýpka et Lukeš, 2021; and Wallacemonas Kostygov et Yurchenko, 2014. Moreover, additional 20 (3.5%) inspected tsetse flies harboured free-living bodonids affiliated with the genera Dimastigella Sandon, 1928; Neobodo Vickerman, 2004; Parabodo Skuja, 1939; and Rhynchomonas Klebs, 1892. In the context of the recently described feeding behaviour of these dipterans, we propose that they become infected while taking sugar meals and water, providing indirect evidence that blood is not their only source of food and liquids.

Field Isolation and Cultivation of Trypanosomatids from Insects

Monoxenous (one host) trypanosomatids from insects and other invertebrates can be introduced into axenic culture relatively easily and efficiently, allowing for their transfer from the field into the laboratory. Here we describe simple methods and alternative cultivation protocols, the wider application of which will allow substantial expansion of trypanosomatids available for research.

If host is refractory, insistent parasite goes berserk: Trypanosomatid Blastocrithidia raabei in the dock bug Coreus marginatus

Here we characterized the development of the trypanosomatid Blastocrithidia raabei in the dock bug Coreus marginatus using light and electron microscopy. This parasite has been previously reported to occur in the host hemolymph, which is rather typical for dixenous trypanosomatids transmitted to a plant or vertebrate with insect's saliva. In addition, C. marginatus has an unusual organization of the intestine, which makes it refractory to microbial infections: two impassable segments isolate the anterior midgut portion responsible for digestion and absorption from the posterior one containing symbiotic bacteria. Our results refuted the possibility of hemolymph infection, but revealed that the refractory nature of the host provokes very aggressive behavior of the parasite and makes its life cycle more complex, reminiscent of that in some dixenous trypanosomatids. In the pre-barrier midgut portion, the epimastigotes of B. raabei attach to the epithelium and multiply similarly to regular insect trypanosomatids. However, when facing the impassable constricted region, the parasites rampage and either fiercely break through the isolating segments or attack the intestinal epithelium in front of the barrier. The cells of the latter group pass to the basal lamina and accumulate there, causing degradation of the epitheliocytes and thus helping the epimastigotes of the former group to advance posteriorly. In the symbiont-containing post-barrier midgut segment, the parasites either attach to bacterial cells and produce cyst-like amastigotes (CLAs) or infect enterocytes. In the rectum, all epimastigotes attach either to the cuticular lining or to each other and form CLAs. We argue that in addition to the specialized life cycle B. raabei possesses functional cell enhancements important either for the successful passage through the intestinal barriers (enlarged rostrum and well-developed Golgi complex) or as food reserves (vacuoles in the posterior end).

Insect trypanosomatids in Papua New Guinea: high endemism and diversity

The extreme biological diversity of Oceanian archipelagos has long stimulated research in ecology and evolution. However, parasitic protists in this geographic area remained neglected and no molecular analyses have been carried out to understand the evolutionary patterns and relationships with their hosts. Papua New Guinea (PNG) is a biodiversity hotspot containing over 5% of the world's biodiversity in less than 0.5% of the total land area. In the current work, we examined insect heteropteran hosts collected in PNG for the presence of trypanosomatid parasites. The diversity of insect flagellates was analysed, to our knowledge for the first time, east of Wallace's Line, one of the most distinct biogeographic boundaries of the world. Out of 907 investigated specimens from 138 species and 23 families of the true bugs collected in eight localities, 135 (15%) were infected by at least one trypanosomatid species. High species diversity of captured hosts correlated with high diversity of detected trypanosomatids. Of 46 trypanosomatid Typing Units documented in PNG, only eight were known from other geographic locations, while 38 TUs (~83%) have not been previously encountered. The widespread trypanosomatid TUs were found in both widely distributed and endemic/sub-endemic insects. Approximately one-third of the endemic trypanosomatid TUs were found in widely distributed hosts, while the remaining species were confined to endemic and sub-endemic insects. The TUs from PNG form clades with conspicuous host-parasite coevolutionary patterns, as well as those with a remarkable lack of this trait. In addition, our analysis revealed new members of the subfamilies Leishmaniinae and Strigomonadinae, potentially representing new genera of trypanosomatids.

Barcoding in trypanosomes

Trypanosomes (genus Trypanosoma) are parasites of humans, and wild and domestic mammals, in which they cause several economically and socially important diseases, including sleeping sickness in Africa and Chagas disease in the Americas. Despite the development of numerous molecular diagnostics and increasing awareness of the importance of these neglected parasites, there is currently no universal genetic barcoding marker available for trypanosomes. In this review we provide an overview of the methods used for trypanosome detection and identification, discuss the potential application of different barcoding techniques and examine the requirements of the 'ideal' trypanosome genetic barcode. In addition, we explore potential alternative genetic markers for barcoding Trypanosoma species, including an analysis of phylogenetically informative nucleotide changes along the length of the 18S rRNA gene.

Molecular mechanisms of thermal resistance of the insect trypanosomatid Crithidia thermophila

In the present work, we investigated molecular mechanisms governing thermal resistance of a monoxenous trypanosomatid Crithidia luciliae thermophila, which we reclassified as a separate species C. thermophila. We analyzed morphology, growth kinetics, and transcriptomic profiles of flagellates cultivated at low (23°C) and elevated (34°C) temperature. When maintained at high temperature, they grew significantly faster, became shorter, with genes involved in sugar metabolism and mitochondrial stress protection significantly upregulated. Comparison with another thermoresistant monoxenous trypanosomatid, Leptomonas seymouri, revealed dramatic differences in transcription profiles of the two species with only few genes showing the same expression pattern. This disparity illustrates differences in the biology of these two parasites and distinct mechanisms of their thermotolerance, a prerequisite for living in warm-blooded vertebrates.

Description of Phytomonas oxycareni n. sp. from the Salivary Glands of Oxycarenus lavaterae

Phytomonas spp. (phytomonads) are a diverse and globally distributed group of unicellular eukaryotes that parasitize a wide range of plants and are transmitted by insect hosts. Here we report the discovery and characterisation of a new species of Phytomonas, named Phytomonas oxycareni n. sp., which was obtained from the salivary glands of the invasive species of true bug Oxycarenus lavaterae (Heteroptera). The new Phytomonas species exhibits a long slender promastigote morphology and can be found both within the lumen of the insect host's salivary glands as well as within the cells of the salivary gland itself. Sampling multiple individuals from the same population post-winter hibernation on two consecutive years revealed that infection was persistent over time. Finally, phylogenetic analyses of small subunit ribosomal RNA genes revealed that this species is sister to other species within the genus Phytomonas, providing new insight into the evolutionary history of the clade.

Genome of Leptomonas pyrrhocoris: a high-quality reference for monoxenous trypanosomatids and new insights into evolution of Leishmania

Many high-quality genomes are available for dixenous (two hosts) trypanosomatid species of the genera Trypanosoma, Leishmania, and Phytomonas, but only fragmentary information is available for monoxenous (single-host) trypanosomatids. In trypanosomatids, monoxeny is ancestral to dixeny, thus it is anticipated that the genome sequences of the key monoxenous parasites will be instrumental for both understanding the origin of parasitism and the evolution of dixeny. Here, we present a high-quality genome for Leptomonas pyrrhocoris, which is closely related to the dixenous genus Leishmania. The L. pyrrhocoris genome (30.4 Mbp in 60 scaffolds) encodes 10,148 genes. Using the L. pyrrhocoris genome, we pinpointed genes gained in Leishmania. Among those genes, 20 genes with unknown function had expression patterns in the Leishmania mexicana life cycle suggesting their involvement in virulence. By combining differential expression data for L. mexicana, L. major and Leptomonas seymouri, we have identified several additional proteins potentially involved in virulence, including SpoU methylase and U3 small nucleolar ribonucleoprotein IMP3. The population genetics of L. pyrrhocoris was also addressed by sequencing thirteen strains of different geographic origin, allowing the identification of 1,318 genes under positive selection. This set of genes was significantly enriched in components of the cytoskeleton and the flagellum.

Novel Trypanosomatid-Bacterium Association: Evolution of Endosymbiosis in Action

We describe a novel symbiotic association between a kinetoplastid protist, Novymonas esmeraldas gen. nov., sp. nov., and an intracytoplasmic bacterium, “Candidatus Pandoraea novymonadis” sp. nov., discovered as a result of a broad-scale survey of insect trypanosomatid biodiversity in Ecuador. We characterize this association by describing the morphology of both organisms, as well as their interactions, and by establishing their phylogenetic affinities. Importantly, neither partner is closely related to other known organisms previously implicated in eukaryote-bacterial symbiosis. This symbiotic association seems to be relatively recent, as the host does not exert a stringent control over the number of bacteria harbored in its cytoplasm. We argue that this unique relationship may represent a suitable model for studying the initial stages of establishment of endosymbiosis between a single-cellular eukaryote and a prokaryote. Based on phylogenetic analyses, Novymonas could be considered a proxy for the insect-only ancestor of the dixenous genus Leishmania and shed light on the origin of the two-host life cycle within the subfamily Leishmaniinae.

The parasitic trypanosomatid protist Novymonas esmeraldas gen. nov., sp. nov. entered into endosymbiosis with the bacterium “Ca. Pandoraea novymonadis” sp. nov. This novel and rather unstable interaction shows several signs of relatively recent establishment, qualifying it as a potentially unique transient stage in the increasingly complex range of eukaryotic-prokaryotic relationships.

New Approaches to Systematics of Trypanosomatidae: Criteria for Taxonomic (Re)description

While dixenous trypanosomatids represent one of the most dangerous pathogens for humans and domestic animals, their monoxenous relatives have frequently become model organisms for studies of diversity of parasitic protists and host-parasite associations. Yet, the classification of the family Trypanosomatidae is not finalized and often confusing. Here we attempt to make a blueprint for future studies in this field. We would like to elicit a discussion about an updated procedure, as traditional taxonomy was not primarily designed to be used for protists, nor can molecular phylogenetics solve all the problems alone. The current status, specific cases, and examples of generalized solutions are presented under conditions where practicality is openly favored over rigid taxonomic codes or blind phylogenetic approach.

Exploring the environmental diversity of kinetoplastid flagellates in the high-throughput DNA sequencing era

The class Kinetoplastea encompasses both free-living and parasitic species from a wide range of hosts. Several representatives of this group are responsible for severe human diseases and for economic losses in agriculture and livestock. While this group encompasses over 30 genera, most of the available information has been derived from the vertebrate pathogenic genera Leishmaniaand Trypanosoma. Recent studies of the previously neglected groups of Kinetoplastea indicated that the actual diversity is much higher than previously thought. This article discusses the known segment of kinetoplastid diversity and how gene-directed Sanger sequencing and next-generation sequencing methods can help to deepen our knowledge of these interesting protists.

Host-specificity of Monoxenous Trypanosomatids: Statistical Analysis of the Distribution and Transmission Patterns of the Parasites from Neotropical Heteroptera

Host-parasite relationships and parasite biodiversity have been the center of attention for many years; however the primary data obtained from large-scale studies remain scarce. Our long term investigations of trypanosomatid (Euglenozoa: Kinetoplastea) biodiversity from Neotropical Heteroptera have yielded almost one hundred typing units (TU) of trypanosomatids from one hundred twenty host species. Half of the parasites' TUs were documented in a single host species only but the rest were found parasitizing two to nine species of hosts, with logarithmic distribution best describing the observed distribution of parasites among hosts. Different host superfamilies did not show significant differences in numbers of trypanosomatid TUs they carry, with exception of Pyrrhocoroidea which showed higher parasite richness than any other group tested. Predatory reduviids shared significantly larger numbers of parasite TUs with phytophagous mirids and coreids than the numbers shared between any other groups. These results show that the specificity of trypanosomatid-heteropteran associations is not very strict: parasites seem to be transmissible between different host groups within the same niche and predatory hosts may acquire parasites from their prey.

Infection Dynamics and Immune Response in a Newly Described Drosophila-Trypanosomatid Association

Trypanosomatid parasites are significant causes of human disease and are ubiquitous in insects. Despite the importance of Drosophila melanogaster as a model of infection and immunity and a long awareness that trypanosomatid infection is common in the genus, no trypanosomatid parasites naturally infecting Drosophila have been characterized. Here, we establish a new model of trypanosomatid infection in Drosophila—Jaenimonas drosophilae, gen. et sp. nov. As far as we are aware, this is the first Drosophila-parasitic trypanosomatid to be cultured and characterized. Through experimental infections, we find that Drosophila falleni, the natural host, is highly susceptible to infection, leading to a substantial decrease in host fecundity. J. drosophilae has a broad host range, readily infecting a number of Drosophila species, including D. melanogaster, with oral infection of D. melanogaster larvae resulting in the induction of numerous immune genes. When injected into adult hemolymph, J. drosophilae kills D. melanogaster, although interestingly, neither the Imd nor the Toll pathway is induced and Imd mutants do not show increased susceptibility to infection. In contrast, mutants deficient in drosocrystallin, a major component of the peritrophic matrix, are more severely infected during oral infection, suggesting that the peritrophic matrix plays an important role in mediating trypanosomatid infection in Drosophila. This work demonstrates that the J. drosophilae-Drosophila system can be a powerful model to uncover the effects of trypanosomatids in their insect hosts.

Trypanosomatid parasites are ubiquitous in insects and are significant causes of disease when vectored to humans by blood-feeding insects. In recent decades, Drosophila has emerged as the predominant insect model of infection and immunity and is also known to be infected by trypanosomatids at high rates in the wild. Despite this, there has been almost no work on their trypanosomatid parasites, in part because Drosophila-specific trypanosomatids have been resistant to culturing. Here, we present the first isolation and detailed characterization of a trypanosomatid from Drosophila, finding that it represents a new genus and species, Jaenimonas drosophilae. Using this parasite, we conducted a series of experiments that revealed many of the unknown aspects of trypanosomatid infection in Drosophila, including host range, transmission biology, dynamics of infection, and host immune response. Taken together, this work establishes J. drosophilae as a powerful new opportunity to study trypanosomatid infections in insects.

Differential diagnosis of the honey bee trypanosomatids Crithidia mellificae and Lotmaria passim

Trypanosomatids infecting honey bees have been poorly studied with molecular methods until recently. After the description of Crithidia mellificae (Langridge and McGhee, 1967) it took about forty years until molecular data for honey bee trypanosomatids became available and were used to identify and describe a new trypanosomatid species from honey bees, Lotmaria passim (Evans and Schwarz, 2014). However, an easy method to distinguish them without sequencing is not yet available. Research on the related bumble bee parasites Crithidia bombi and Crithidia expoeki revealed a fragment length polymorphism in the internal transcribed spacer 1 (ITS1), which enabled species discrimination. In search of fragment length polymorphisms for differential diagnostics in honey bee trypanosomatids, we studied honey bee trypanosomatid cell cultures of C. mellificae and L. passim. This research resulted in the identification of fragment length polymorphisms in ITS1 and ITS1-2 markers, which enabled us to develop a diagnostic method to differentiate both honey bee trypanosomatid species without the need for sequencing. However, the amplification success of the ITS1 marker depends probably on the trypanosomatid infection level. Further investigation confirmed that L. passim is the dominant species in Belgium, Japan and Switzerland. We found C. mellificae only rarely in Belgian honey bee samples, but not in honey bee samples from other countries. C. mellificae was also detected in mason bees (Osmia bicornis and Osmia cornuta) besides in honey bees. Further, the characterization and comparison of additional markers from L. passim strain SF (published as C. mellificae strain SF) and a Belgian honey bee sample revealed very low divergence in the 18S rRNA, ITS1-2, 28S rRNA and cytochrome b sequences. Nevertheless, a variable stretch was observed in the gp63 virulence factor.

Kentomonas gen. n., a new genus of endosymbiont-containing trypanosomatids of Strigomonadinae subfam. n

Compared to their relatives, the diversity of endosymbiont-containing Trypanosomatidae remains under-investigated, with only two new species described in the past 25 years, bringing the total to six. The possible reasons for such a poor representation of this group are either their overall scarcity or susceptibility of their symbionts to antibiotics that are traditionally used for cultivation of flagellates. In this work we describe the isolation, cultivation, as well as morphological and molecular characterization of a novel endosymbiont-harboring trypanosomatid species, Kentomonas sorsogonicus sp. n. The newly erected genus Kentomonas gen. n. shares many common features with the genera Angomonas and Strigomonas, such as the presence of an extensive system of peripheral mitochondrial branches distorting the corset of subpellicular microtubules, large and loosely packed kinetoplast, and a rudimentary paraflagellar rod. Here we also propose to unite all endosymbiont-bearing trypanosomatids into the new subfamily Strigomonadinae subfam. n.

Molecular revision of the genus Wallaceina

This work is focused on the molecular revision of the genus Wallaceina established in the very twilight of the classical morphotype-based approach to classification of the Trypanosomatidae. The genus was erected due to the presence of a unique variant of endomastigotes. In molecular phylogenetic studies four described species of Wallaceina were shown to be extremely close to each other and to some other undescribed isolates clustered within Leishmaniinae clade, while three recently included species formed a separate clade. Our results of morphological and molecular phylogenetic analyses demonstrated that all Leishmaniinae-bound wallaceinas are just different isolates of the same species that we rename back to Crithidia brevicula Frolov, Malysheva, 1989. To accommodate former Wallaceina spp. phylogenetically distant from the genus Crithidia, we propose a new generic name Wallacemonas Kostygov et Yurchenko, 2014.

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.

Monitoring Trypanosoma cruzi infection in triatomines using PCR in Mato Grosso do Sul, Brazil

INTRODUCTION

The aim of the present study was to assess the polymerase chain reaction (PCR) as a method for detecting Trypanosoma cruzi infection in triatomines that had been previously determined by microscopic examination in the State of Mato Grosso do Sul, Brazil.

METHODS

In total, 515 specimens were collected. Material from the digestive tract of each triatomine was analyzed for the presence of T. cruzi by microscopic examination and PCR using the 121/122 primer set.

RESULTS

Among the 515 specimens tested, 58 (11.3%) were positive by microscopy and 101 (19.61%) were positive by PCR and there was an association between the results of the techniques (χ2 = 53.354, p = 0.001). The main species of triatomine identified was T. sordida (95.5%)

CONCLUSIONS

The use of PCR in entomological surveillance may contribute to a better assessment of the occurrence of T. cruzi in triatomine populations.

Transcriptional responses in a Drosophila defensive symbiosis

Inherited symbionts are ubiquitous in insects and can have important consequences for the fitness of their hosts. Many inherited symbionts defend their hosts against parasites or other natural enemies; however, the means by which most symbionts confer protection is virtually unknown. We examine the mechanisms of defence in a recently discovered case of symbiont-mediated protection, where the bacterial symbiont Spiroplasma defends the fly Drosophila neotestacea from a virulent nematode parasite, Howardula aoronymphium. Using quantitative PCR of Spiroplasma infection intensities and whole transcriptome sequencing, we attempt to distinguish between the following modes of defence: symbiont-parasite competition, host immune priming and the production of toxic factors by Spiroplasma. Our findings do not support a model of exploitative competition between Howardula and Spiroplasma to mediate defence, nor do we find strong support for host immune priming during Spiroplasma infection. Interestingly, we recovered sequence for putative toxins encoded by Spiroplasma, including a novel putative ribosome-inactivating protein, transcripts of which are up-regulated in response to nematode exposure. Protection via the production of toxins may be a widely used and important mechanism in heritable defensive symbioses in insects.

Diversity of trypanosomatids (Kinetoplastea: Trypanosomatidae) parasitizing fleas (Insecta: Siphonaptera) and description of a new genus Blechomonas gen. n

To further investigate the diversity of Trypanosomatidae we have examined the species present within the flea (Siphonaptera) population in the Czech Republic. Out of 1549 fleas, 239 were found to be infected by trypanosomatids. Axenic cultures were established from 90 infected specimens and 29 of them were further characterized. Molecular phylogenetic analysis of the SL RNA, gGAPDH, and SSU rRNA genes revealed a striking diversity within this group and analyzed isolates were classified into 16 Typing units (TUs) of which 15 typified new species. In addition to one Trypanosoma species, two TUs grouped within the sub-family Leishmaniinae, two clustered together with Herpetomonas, wheras 11 TUs formed a novel clade branching off between Trypanosoma spp. and remaining trypanosomatids. We propose to recognize this clade as a new genus Blechomonas and a new subfamily Blechomonadinae, and provide molecular and morphological description of 11 TUs representing this genus. Our finding of such an ancient host-specific group sheds new light at the origin of Trypanosomatidae and the roots of dixenous parasitism. The strict host restriction of Blechomonas to Siphonaptera with adult fleas' dependence on blood meal may reflect passing of parasites from larvae through pupae to adults and implies potential transmission to the warm-blooded vertebrates.

Trypanosoma livingstonei: a new species from African bats supports the bat seeding hypothesis for the Trypanosoma cruzi clade

BACKGROUND

Bat trypanosomes have been implicated in the evolutionary history of the T. cruzi clade, which comprises species from a wide geographic and host range in South America, Africa and Europe, including bat-restricted species and the generalist agents of human American trypanosomosis T. cruzi and T. rangeli.

METHODS

Trypanosomes from bats (Rhinolophus landeri and Hipposideros caffer) captured in Mozambique, southeast Africa, were isolated by hemoculture. Barcoding was carried out through the V7V8 region of Small Subunit (SSU) rRNA and Fluorescent Fragment Length barcoding (FFLB). Phylogenetic inferences were based on SSU rRNA, glyceraldehyde phosphate dehydrogenase (gGAPDH) and Spliced Leader (SL) genes. Morphological characterization included light, scanning and transmission electron microscopy.

RESULTS

New trypanosomes from bats clustered together forming a clade basal to a larger assemblage called the T. cruzi clade. Barcoding, phylogenetic analyses and genetic distances based on SSU rRNA and gGAPDH supported these trypanosomes as a new species, which we named Trypanosoma livingstonei n. sp. The large and highly polymorphic SL gene repeats of this species showed a copy of the 5S ribosomal RNA into the intergenic region. Unique morphological (large and broad blood trypomastigotes compatible to species of the subgenus Megatrypanum and cultures showing highly pleomorphic epimastigotes and long and slender trypomastigotes) and ultrastructural (cytostome and reservosomes) features and growth behaviour (when co-cultivated with HeLa cells at 37°C differentiated into trypomastigotes resembling the blood forms and do not invaded the cells) complemented the description of this species.

CONCLUSION

Phylogenetic inferences supported the hypothesis that Trypanosoma livingstonei n. sp. diverged from a common ancestral bat trypanosome that evolved exclusively in Chiroptera or switched at independent opportunities to mammals of several orders forming the clade T. cruzi, hence, providing further support for the bat seeding hypothesis to explain the origin of T. cruzi and T. rangeli.

Growing diversity of trypanosomatid parasites of flies (Diptera: Brachycera): frequent cosmopolitism and moderate host specificity

Widely distributed, highly prevalent and speciose, trypanosomatid flagellates represent a convenient model to address topics such as host specificity, diversity and distribution of parasitic protists. Recent studies dealing with insect parasites of the class Kinetoplastea have been focused mainly on trypanosomatids from true bugs (Heteroptera), even though flies (Diptera, Brachycera) are also known as their frequent hosts. Phylogenetic position, host specificity and geographic distribution of trypanosomatids parasitizing dipteran hosts collected in nine countries on four continents (Bulgaria, Czech Republic, Ecuador, Ghana, Kenya, Madagascar, Mongolia, Papua New Guinea and Turkey) are presented. Spliced leader (SL) RNA gene repeats and small subunit (SSU) rRNA genes were PCR amplified from trypanosomatids infecting the gut of a total of forty fly specimens belonging to nine families. While SL RNA was mainly used for barcoding, SSU rRNA was utilized in phylogenetic analyses. Thirty-six different typing units (TUs) were revealed, of which 24 are described for the first time and represent potential new species. Multiple infections with several TUs are more common among brachyceran hosts than in true bugs, reaching one third of cases. When compared to trypanosomatids from heteropteran bugs, brachyceran flagellates are more host specific on the genus level. From seven previously recognized branches of monoxenous trypanosomatids, the Blastocrithidia and "jaculum" clades accommodate almost solely parasites of Heteroptera; two other clades (Herpetomonas and Angomonas) are formed primarily by flagellates found in dipteran hosts, with the most species-rich Leishmaniinae and the small Strigomonas and "collosoma" clades remaining promiscuous. Furthermore, two new clades of trypanosomatids from brachyceran flies emerged in this study. While flagellates from brachyceran hosts have moderate to higher host specificity, geographic distribution of at least some of them seems to be cosmopolitan. Moreover, the genus Angomonas, so far known only from South America, is present on other continents as well.

Discovery of trypanosomatid parasites in globally distributed Drosophila species

Microbial parasites of animals include bacteria, viruses, and various unicellular eukaryotes. Because of the difficulty in studying these microorganisms in both humans and disease vectors, laboratory models are commonly used for experimental analysis of host-parasite interactions. Drosophila is one such model that has made significant contributions to our knowledge of bacterial, fungal, and viral infections. Despite this, less is known about other potential parasites associated with natural Drosophila populations. Here, we surveyed sixteen Drosophila populations comprising thirteen species from four continents and Hawaii and found that they are associated with an extensive diversity of trypanosomatids (Euglenozoa, Kinetoplastea). Phylogenetic analysis finds that Drosophila-associated trypanosomatids are closely related to taxa that are responsible for various types of leishmaniases and more distantly related to the taxa responsible for human African trypanosomiasis and Chagas disease. We suggest that Drosophila may provide a powerful system for studying the interactions between trypanosomatids and their hosts.

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.

Molecular phylogenetic redefinition of Herpetomonas (Kinetoplastea, Trypanosomatidae), a genus of insect parasites associated with flies

In order to review the taxonomy of the genus Herpetomonas through phylogenetic and morphological analyses we barcoded 527 insect trypanosomatids by sequencing the V7V8 region of the small subunit ribosomal RNA (SSU rRNA) gene. Fifty two flagellates, 90% of them from Diptera, revealed to be related to known species of Herpetomonas. Sequences of entire glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) and SSU rRNA genes were employed for phylogenetic inferences including representatives of all genera of Trypanosomatidae. In the resulting phylogenetic trees, the selected flagellates clustered into a monophyletic assemblage that we are considering as the redefined genus Herpetomonas. Internal transcribed spacer 1 (ITS1) rDNA sequences and putative secondary structures of this region were compared for evaluation of inter- and intraspecific variability. The flagellates were classified in six already known species and five new species. In addition, two Leptomonas spp. were moved to Herpetomonas, now comprising 13 valid species, while four species were excluded from the genus. Light and electron microscopy revealed the extreme polymorphism of Herpetomonas, hindering genus and species identification by morphological characteristics. Our findings also showed that some species of Herpetomonas are generalist parasites of flies and appear to be as cosmopolitan as their hosts.

New species of insect trypanosomatids from Costa Rica and the proposal for a new subfamily within the Trypanosomatidae

Several new species of trypanosomatids (Euglenozoa, Kinetoplastea, Trypanosomatidae), isolated from the intestines of Neotropical insects (Heteroptera), were genotyped on the basis of spliced leader RNA, and also defined phylogenetically using gene sequences of small subunit ribosomal RNA and glycosomal glyceraldehyde phosphate dehydrogenase. The taxonomic descriptions also included characterization using morphometry and electron microscopy. Our phylogenetic analyses placed the new species within the clade, previously designated "SE" for "Slowly Evolving" sequences of ribosomal RNA genes, a clade that also includes numerous monoxenous parasites of insects from the genera Crithidia, Leptomonas, and Wallaceina, as well as the dixenous genus Leishmania. Based on the high phylogenetic support for this clade, which is consistently recovered in all recent phylogenetic reconstructions, a proposal is put forward to recognize this natural taxon as a new subfamily, Leishmaniinae, within the family Trypanosomatidae.

The integrative taxonomic approach reveals host specific species in an encyrtid parasitoid species complex

Integrated taxonomy uses evidence from a number of different character types to delimit species and other natural groupings. While this approach has been advocated recently, and should be of particular utility in the case of diminutive insect parasitoids, there are relatively few examples of its application in these taxa. Here, we use an integrated framework to delimit independent lineages in Encyrtus sasakii (Hymenoptera: Chalcidoidea: Encyrtidae), a parasitoid morphospecies previously considered a host generalist. Sequence variation at the DNA barcode (cytochrome c oxidase I, COI) and nuclear 28S rDNA loci were compared to morphometric recordings and mating compatibility tests, among samples of this species complex collected from its four scale insect hosts, covering a broad geographic range of northern and central China. Our results reveal that Encyrtus sasakii comprises three lineages that, while sharing a similar morphology, are highly divergent at the molecular level. At the barcode locus, the median K2P molecular distance between individuals from three primary populations was found to be 11.3%, well outside the divergence usually observed between Chalcidoidea conspecifics (0.5%). Corroborative evidence that the genetic lineages represent independent species was found from mating tests, where compatibility was observed only within populations, and morphometric analysis, which found that despite apparent morphological homogeneity, populations clustered according to forewing shape. The independent lineages defined by the integrated analysis correspond to the three scale insect hosts, suggesting the presence of host specific cryptic species. The finding of hidden host specificity in this species complex demonstrates the critical role that DNA barcoding will increasingly play in revealing hidden biodiversity in taxa that present difficulties for traditional taxonomic approaches.

Cosmopolitan distribution of a trypanosomatid Leptomonas pyrrhocoris

A trypanosomatid species, designated as Typing Unit 1 (TU1) by sequences of SL RNA gene repeats, has been found in the intestine of pyrrhocorids (Insecta: Heteroptera) in Europe, Mediterranean, Central America and some parts of Asia and Africa. Phylogenetic analysis of the SL repeat sequences has shown that the isolates group in the tree according to their geographic origin. The maximal sequence divergence was observed in parasites from Neotropics suggesting the origin within and subsequent migrations from this region. The global distribution of the parasite could have been facilitated by ubiquity of its hosts that include several genera of the family Pyrrhocoridae. In Europe the TU1 flagellates frequently occur in Pyrrhocoris apterus, the host of Leptomonas pyrrhocorisZotta, 1912, a species that had been insufficiently defined by host and light microscopy level morphology. Herein, the Zotta's species description has been amended to include the TU1 SL RNA repeat, SSU rRNA, glycosomal GAPDH gene sequences, as well as ultrastructure. In addition, Leptomonas scantii n. sp. with an overlapping host range has been described. Moreover, 10 typing units of trypanosomatids found in the pyrrhocorid hosts demonstrate the extent of variability of trypanosomatids occurring in one host family.

Trypanosomatids are common and diverse parasites of Drosophila

Drosophila melanogaster is an important model system of immunity and parasite resistance, yet most studies use parasites that do not naturally infect this organism. We have studied trypanosomatids in natural populations to assess the prevalence and diversity of these gut parasites. We collected several species of Drosophila from Europe and surveyed them for trypanosomatids using conserved primers for two genes. We have used the conserved GAPDH sequence to construct a phylogenetic tree and the highly variable spliced leader RNA to assay genetic diversity. All 5 of the species that we examined were infected, and the average prevalence ranged from 1 to 6%. There are several different groups of trypanosomatids, related to other monoxenous Trypanosomatidae. These may represent new trypanosomatid species and were found in different species of European Drosophila from different geographical locations. The detection of a little studied natural pathogen in D. melanogaster and related species provides new opportunities for research into both the Drosophila immune response and the evolution of hosts and parasites.

Infection rates of Triatoma protracta (Uhler) with Trypanosoma cruzi in Southern California and molecular identification of trypanosomes

We report Trypanosoma cruzi infection rates of the native kissing bug Triatoma protracta in southern California. The rates are within the historically reported range, but differ significantly between the two sites (19% in Escondido and 36% in Glendora). Identification of T. cruzi in T. protracta was conducted for the first time by using partial 18S ribosomal RNA and 24Sα ribosomal RNA sequences. Incongruence of 24Sα ribosomal RNA phylogeny with current T. cruzi genotype classification supports non-clonality of some T. cruzi genotypes.

Two new species of trypanosomatid parasites isolated from Heteroptera in Costa Rica

Two new trypanosomatid species (Euglenozoa, Kinetoplastea) isolated from the intestinal tract of heteropteran insect hosts were described based on molecular phylogenetic analyses of Spliced Leader (SL) RNA gene repeats, glycosomal glyceraldehyde phosphate dehydrogenase, and small subunit ribosomal RNA genes, as well as by morphology. Leptomonas barvae n. sp., from a mirid host Collaria oleosa, was found to represent one of the closest monoxenous (one host) relatives of the dixenous (two hosts) parasitic genus Leishmania. This finding further supports the origin of these dixenous parasites from monoxenous progenitors in the Neotropics. Blastocrithidia largi n. sp., from a largid host Largus cinctus, is among a few members of this genus available in culture. The species is a close relative of Blastocrithidia triatomae and is a member of a new monophyletic phylogenetic group characterized by formation of straphanger cysts.

Characterization of spliced leader genes of Trypanosoma (Megatrypanum) theileri: phylogeographical analysis of Brazilian isolates from cattle supports spatial clustering of genotypes and parity with ribosomal markers

Trypanosoma (Megatrypanum) theileri from cattle and trypanosomes of other artiodactyls form a clade of closely related species in analyses using ribosomal sequences. Analysis of polymorphic sequences of a larger number of trypanosomes from broader geographical origins is required to evaluate the clustering of isolates as suggested by previous studies. Here, we determined the sequences of the spliced leader (SL) genes of 21 isolates from cattle and 2 from water buffalo from distant regions of Brazil. Analysis of SL gene repeats revealed that the 5S rRNA gene is inserted within the intergenic region. Phylogeographical patterns inferred using SL sequences showed at least 5 major genotypes of T. theileri distributed in 2 strongly divergent lineages. Lineage TthI comprises genotypes IA and IB from buffalo and cattle, respectively, from the Southeast and Central regions, whereas genotype IC is restricted to cattle from the Southern region. Lineage TthII includes cattle genotypes IIA, which is restricted to the North and Northeast, and IIB, found in the Centre, West, North and Northeast. PCR-RFLP of SL genes revealed valuable markers for genotyping T. theileri. The results of this study emphasize the genetic complexity and corroborate the geographical structuring of T. theileri genotypes found in cattle.

Kinetoplastid genomics: the thin end of the wedge

The completion of the genome sequencing projects for major pathogens Trypanosoma brucei, Trypanosoma cruzi and Leishmania major has enabled numerous studies that would have been difficult or impossible to perform otherwise. New technologies in sequencing and protein analyses promise further rapid expansion in our capabilities. The keys to successful use of these new tools are recognizing the power and limitations of studies performed thus far, grasping the unrealized potential of new and developing technologies, and creating access to a multidisciplinary set of skills that will facilitate research, particularly in the bioinformatic analysis of the reams of data that will be forthcoming. In this Discussion, we will provide an overview of kinetoplastid genomics studies with emphasis on studies advanced through genomic data, and a preview of what may come in the near future.

Discovery and barcoding by analysis of spliced leader RNA gene sequences of new isolates of Trypanosomatidae from Heteroptera in Costa Rica and Ecuador

Trypanosomatid diversity in Heteroptera was sampled using a culture-independent approach based on amplification and sequencing of Spliced Leader RNA gene repeats from environmental samples. By combining the data collected herein with that of previous work, the prevalence of parasites was found to be 22%-23%. Out of approximately 170 host species investigated nearly 60 were found to harbor trypanosomatids. The parasites found were grouped by cluster analysis into 48 typing units. Most of these were well separated from the known groups and, therefore, likely represent new trypanosomatid species. The sequences for each typing unit serve as barcodes to facilitate their recognition in the future. As the sampled host species represent a minor fraction of potential hosts, the entire trypanosomatid diversity is far greater than described thus far. Investigations of trypanosomatid diversity, host-specificity, and biogeography have become feasible using the approach described herein.

Sergeia podlipaevi gen. nov., sp. nov. (Trypanosomatidae, Kinetoplastida), a parasite of biting midges (Ceratopogonidae, Diptera)

Three strains of a trypanosomatid protozoan were isolated from the midguts of two naturally infected species of biting midges [Culicoides (Oecacta) festivipennis and Culicoides (Oecacta) truncorum] and characterized by light and electron microscopy and by molecular techniques. Morphological characteristics and sequences of the 18S rRNA, 5S rRNA, spliced leader RNA and glycosomal glyceraldehyde-3-phosphate dehydrogenase genes indicate that the studied flagellates represent a novel phylogenetic lineage within the Trypanosomatidae. Based on phylogenetic analyses, the novel endosymbiont-free, monoxenous trypanosomatid was classified as Sergeia podlipaevi gen. nov., sp. nov. Interestingly, it is closely related to another trypanosomatid species that parasitizes the sand fly Lutzomyia evansi, a blood-sucking dipteran from South America. The type strain of S. podlipaevi sp. nov., ICUL/CZ/2000/CER3, was obtained from Malpighian tubes. Of 2518 females of seven species of biting midges trapped in the Czech Republic, more than 1.5 % were infected by trypanosomatid parasites. An unrelated insect species, Culicoides (Monoculicoides) nubeculosus, was experimentally infected with S. podlipaevi, demonstrating that its host range extends to different subgenera of biting midges.