A new lineage of trypanosomes from Australian vertebrates and terrestrial bloodsucking leeches (Haemadipsidae)

Metatranscriptomic profiling reveals diverse tick-borne bacteria, protozoans and viruses in ticks and wildlife from Australia

Tick-borne zoonoses are emerging globally due to changes in climate and land use. While the zoonotic threats associated with ticks are well studied elsewhere, in Australia, the diversity of potentially zoonotic agents carried by ticks and their significance to human and animal health is not sufficiently understood. To this end, we used untargeted metatranscriptomics to audit the prokaryotic, eukaryotic and viral biomes of questing ticks and wildlife blood samples from two urban and rural sites in New South Wales, Australia. Ixodes holocyclus and Haemaphysalis bancrofti were the main tick species collected, and blood samples from Rattus rattus, Rattus fuscipes, Perameles nasuta and Trichosurus vulpecula were also collected and screened for tick-borne microorganisms using metatranscriptomics followed by conventional targeted PCR to identify important microbial taxa to the species level. Our analyses identified 32 unique tick-borne taxa, including 10 novel putative species. Overall, a wide range of tick-borne microorganisms were found in questing ticks including haemoprotozoa such as Babesia, Theileria, Hepatozoon and Trypanosoma spp., bacteria such as Borrelia, Rickettsia, Ehrlichia, Neoehrlichia and Anaplasma spp., and numerous viral taxa including Reoviridiae (including two coltiviruses) and a novel Flaviviridae-like jingmenvirus. Of note, a novel hard tick-borne relapsing fever Borrelia sp. was identified in questing H. bancrofti ticks which is closely related to, but distinct from, cervid-associated Borrelia spp. found throughout Asia. Notably, all tick-borne microorganisms were phylogenetically unique compared to their relatives found outside Australia, and no foreign tick-borne human pathogens such as Borrelia burgdorferi s.l. or Babesia microti were found. This work adds to the growing literature demonstrating that Australian ticks harbour a unique and endemic microbial fauna, including potentially zoonotic agents which should be further studied to determine their relative risk to human and animal health.

"Visiting old, learn new": taxonomical overview of chiropteran trypanosomes from the morphology to the genes

Bats (the order Chiroptera) account for more than 20% of all mammalian species in the world; remarkably, they are the only mammals capable of true and sustained flight using their wing-like forelimbs. Since the beginning of the twentieth century, various morphotypes (or genotypes in the last decade) of haemoflagellates in the genus Trypanosoma (Euglenozoa: Kinetoplastea: Trypanosomatidae) have been reported worldwide in the blood of bats. Of note, the latent nature of chiropteran trypanosome infection with low levels of parasitaemia, together with the apparent morphological variation of the bloodstream forms related to phenotypical plasticity and the morphological resemblance of different parasite species, has hampered the taxonomic classification of bat trypanosomes based on morphological criteria. This said, 50 years ago, Hoare (1972) provisionally divided bat trypanosomes into two major morphotypes: the megadermae group (corresponding to the subgenus Megatrypanum in the traditional taxonomic system; 8 species) and the vespertilionis group (similar to the subgenus Schizotrypanum; 5 species). Importantly, the biological and biochemical analyses of bat trypanosomes isolated by haemoculture, together with the molecular genetic characterisation using various gene markers, allowed the establishment of clear phylogenetic and taxonomic relationships of various isolates from different continents in the last two decades. Here, we review the historical taxonomic approaches used to define chiropteran trypanosomes, as well as the ones currently employed to shed light on the diversity and evolutional tracks of the globally distributed chiropteran trypanosomes.

First Report of Trypanosoma theileri in Equine Host and Tabanus sp. in Malaysia

Trypanosoma (Megatrypanum) theileri is a non-pathogenic or weakly pathogenic parasite of domestic cattle that is cyclically transmitted by blood-sucking insects, mainly tabanid flies. It has been reported in several countries like Brazil, Venezuela, Japan, Taiwan, Thailand, Vietnam, and the Philippines. Although the ruminant industry is actively expanded in Malaysia, T. theileri and T. theileri-like trypanosomes have never been reported from Malaysia. The low pathogenicity of this species might be the main reason for overlooking T. theileri in this country. This paper describes an unforeseen finding of T. theileri from the outbreak of T. evansi in the state of Kelantan, Malaysia. This is the first time T. theileri reported in Malaysia, and also the first time T. theileri is reported in equid. Clinical signs compatible with infection by blood protozoa were observed; however, it was uncertain whether they were due to T. theileri infection. The detection of T. theileri from the blood sample and Tabanus sp. were confirmed through molecular analysis with PCR and DNA sequencing. In the present study, T. theileri from one horse and one Tabanus sp. were clustered with sequences of the previously described phylogenetic lineages from Japan, Chad and Brazil cattle. Even though this species is claimed to be host-specific with ruminant host restriction, the finding from this study suggested that T. theileri can infect equine whilst other isolates are known to infect ruminant species only. It is suspected there were two genotypes of T. theileri circulating in at least two districts of Kelantan. Thus, further study on multiple DNA regions should be conducted to determine the strains of detected T. theileri in Malaysia. Its impact on the horse and cattle industry should also be revised.

A new species of mammalian trypanosome, Trypanosoma (Megatrypanum) bubalisi sp. nov., found in the freshwater leech Hirudinaria manillensis

Leeches have long been considered potential vectors for the aquatic lineage of trypanosomes, while bloodsucking insects are generally considered as the vectors for the terrestrial lineage of trypanosomes. The freshwater leech, Hirudinaria manillensis, is a widely distributed species in southern China and could potentially act as the vector for trypanosomes. Prior to this study, no trypanosomes had been reported from this leech. However, in this study, leeches were collected from three different places in Guangdong province, China, and a large number of flagellates were isolated and successfully cultured in vitro. Based on morphology, these flagellates looked like a typical trypanosome species. Analysis was carried out on the molecular sequences of the 18S rRNA gene and the glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) gene. To our surprise, these flagellates were identified as likely to be a mammalian trypanosome belonging to the clade containing Trypanosoma (Megatrypanum) theileri but they are significantly different from the typical TthI and TthII stocks. Analyses of blood composition indicated that the source of the blood meal in these leeches was from the water buffalo (Bubalus bubalis). To further test if this flagellate from the freshwater leech was indeed a mammalian trypanosome, we transferred the trypanosomes cultured at 27-37 °C and they were able to successfully adapt to this mammalian body temperature, providing further supporting evidence. Due to the significant genetic differences from other related trypanosomes in the subgenus Megatrypanum, we propose that this flagellate, isolated from H. manillensis, is a new species and have named it Trypanosoma bubalisi. Our results indicate that freshwater leeches may be a potential vector of this new mammalian trypanosome.

Genetic diversity of cervid Trypanosoma theileri in Honshu sika deer (Cervus nippon) in Japan

The taxonomy of ruminant Trypanosoma theileri and its relatives (Kinetoplastida: Trypanosomatidae) is controversial, with recent phylogenetic studies segregating T. theileri in cattle and other ruminants worldwide into two major genetic lineages (the TthI and TthII clades) based on genetic markers. In the present study, T. theileri-like trypanosomes isolated from Honshu sika deer (Cervus nippon) in the western Japan (YMG isolate) were genetically characterized using a number of genetic markers. Sika deer trypanosomes of the YMG isolate were genetically different from the Trypanosoma sp. TSD1 isolate previously recorded from Hokkaido sika deer in northern Japan, with the former trypanosome isolate being genetically closer to European cervid trypanosomes and the bovine T. theileri TthII lineage. In contrast, the latter isolate exhibited greater relatedness to North American cervid trypanosomes and the bovine T. theileri TthI lineage, although a clear genetic distinction between these was apparent. Furthermore, trypanosomes in Honshu sika deer from the central part of Japan harboured additional genetic diversity and were closer to either TSD1 or YMG isolates, while distinct from known T. theileri-related genotypes. Importantly, cervids and wild ruminants worldwide might harbour divergent descendants of a T. theileri ancestor, which exhibit rigid host specificity to either bovines or cervid species.

Diversity and Epidemiology of Bat Trypanosomes: A One Health Perspective

Bats (order Chiroptera) have been increasingly recognised as important reservoir hosts for human and animal pathogens worldwide. In this context, molecular and microscopy-based investigations to date have revealed remarkably high diversity of Trypanosoma spp. harboured by bats, including species of recognised medical and veterinary importance such as Trypanosoma cruzi and Trypanosoma evansi (aetiological agents of Chagas disease and Surra, respectively). This review synthesises current knowledge on the diversity, taxonomy, evolution and epidemiology of bat trypanosomes based on both molecular studies and morphological records. In addition, we use a One Health approach to discuss the significance of bats as reservoirs (and putative vectors) of T. cruzi, with a focus on the complex associations between intra-specific genetic diversity and eco-epidemiology of T. cruzi in sylvatic and domestic ecosystems. This article also highlights current knowledge gaps on the biological implications of trypanosome co-infections in a single host, as well as the prevalence, vectors, life-cycle, host-range and clinical impact of most bat trypanosomes recorded to date. Continuous research efforts involving molecular surveillance of bat trypanosomes are required for improved disease prevention and control, mitigation of biosecurity risks and potential spill-over events, ultimately ensuring the health of humans, domestic animals and wildlife globally.

Molecular Detection of Trypanosoma spp. in Questing and Feeding Ticks (Ixodidae) Collected from an Endemic Region of South-West Australia

A growing number of indigenous trypanosomes have been reported to naturally infect a variety of Australian wildlife with some species of Trypanosoma implicated in the population decline of critically endangered marsupials. However, the mode of transmission of Australian trypanosomes is unknown since their vectors remain unidentified. Here we aimed to fill this current knowledge gap about the occurrence and identity of indigenous trypanosomes in Australian invertebrates by conducting molecular screening for the presence of Trypanosoma spp. in native ticks collected from south-west Australia. A total of 231 ticks (148 collected from vegetation and 83 retrieved directly from 76 marsupial hosts) were screened for Trypanosoma using a High-Resolution Melt (HRM) qPCR assay. An overall Trypanosoma qPCR positivity of 37% (46/125) and 34% (26/76) was detected in questing ticks and host-collected (i.e., feeding) ticks, respectively. Of these, sequencing revealed 28% (35/125) of questing and 28% (21/76) of feeding ticks were infected with one or more of the five species of trypanosome previously reported in this region (T. copemani, T. noyesi, T. vegrandis, T. gilletti, Trypanosoma sp. ANU2). This work has confirmed that Australian ticks are capable of harbouring several species of indigenous trypanosome and likely serve as their vectors.

18S rRNA gene sequence-structure phylogeny of the Trypanosomatida (Kinetoplastea, Euglenozoa) with special reference to Trypanosoma

Parasites of the order Trypanosomatida are known due to their medical relevance. Despite the progress made in the past decades on understanding the evolution of this group of organisms, there are still many open questions that require robust phylogenetic markers to increase the resolution of trees. Using two known 18S rRNA gene template structures (from Trypanosoma cruzi Chagas, 1909 and Trypanosoma brucei Plimmer and Bradford, 1899), individual 18S rRNA gene secondary structures were predicted by homology modeling. Sequences and their secondary structures, automatically encoded by a 12-letter alphabet (each nucleotide with its three structural states, paired left, paired right, unpaired), were simultaneously aligned. Sequence-structure trees were generated by neighbor joining and/or maximum likelihood. The reconstructed trees allowed us to discuss not only the big picture of trypanosomatid phylogeny but also a comprehensive sampling of trypanosomes evaluated in the context of trypanosomatid diversity. The robust support (bootstrap > 75) for well-known clades and critical branches suggests that the simultaneous use of 18S rRNA sequence and secondary structure data can reconstruct robust phylogenetic trees and can be used by the trypanosomatid research community for future analysis.

BASELINE HEALTH PARAMETERS FOR A NEWLY ESTABLISHED POPULATION OF LONG-NOSED POTOROO (POTOROUS TRIDACTYLUS) AT BOODEREE NATIONAL PARK, AUSTRALIA

Over two field seasons during 2014-15, 35 long-nosed potoroos (Potorous tridactylus) were captured in state forests in South Eastern New South Wales for translocation to Booderee National Park, Jervis Bay Territory, Australia. Animals were anesthetized for physical examination and collection of samples to assess general health and screen for select diseases identified during a disease risk assessment. Morphologic, hematologic, and biochemical parameters were determined, and parasites were identified where possible. Trypanosoma gilletti, Trypanosoma vegrandis, and novel genotypes most similar to a Trypanosoma wallaby-derived isolate (ABF) were identified from blood samples by PCR; the first time Trypanosoma has been described in this species. Also reported is the first confirmation of the Australian paralysis tick, Ixodes holocyclus, from the long-nosed potoroo. Surveillance showed that Cryptococcus sp. may form part of the normal nasal flora for long-nosed potoroo. Salmonella enterica serotype Dublin and Salmonella enterica subsp. enterica was identified from rectal swabs of otherwise healthy animals. The data provide baseline health and disease parameters for this newly established population and the source population and will inform future translocation and conservation management activities. These data expand current knowledge on aspects of the biology and microbiology of the long-nosed potoroo, both locally and nationally.

A new subspecies of Trypanosoma cyclops found in the Australian terrestrial leech Chtonobdella bilineata

Previously, it was suggested that haemadipsid leeches represent an important vector of trypanosomes amongst native animals in Australia. Consequently, Chtonobdella bilineata leeches were investigated for the presence of trypanosome species by polymerase chain reaction (PCR), DNA sequencing and in vitro isolation. Phylogenetic analysis ensued to further define the populations present. PCR targeting the 28S rDNA demonstrated that over 95% of C. bilineata contained trypanosomes; diversity profiling by deep amplicon sequencing of 18S rDNA indicated the presence of four different clusters related to the Trypanosoma (Megatrypanum) theileri. Novy–MacNeal–Nicolle slopes with liquid overlay were used to isolate trypanosomes into culture that proved similar in morphology to Trypanosoma cyclops in that they contained a large numbers of acidocalcisomes. Phylogeny of 18S rDNA/GAPDH/ND5 DNA sequences from primary cultures and subclones showed the trypanosomes were monophyletic, with T. cyclops as a sister group. Blood-meal analysis of leeches showed that leeches primarily contained blood from swamp wallaby (Wallabia bicolour), human (Homo sapiens) or horse (Equus sp.). The leech C. bilineata is a host for at least five lineages of Trypanosoma sp. and these are monophyletic with T. cyclops; we propose Trypanosoma cyclops australiensis as a subspecies of T. cyclops based on genetic similarity and biogeography considerations.

Blood Parasites in Endangered Wildlife-Trypanosomes Discovered During a Survey of Haemoprotozoa from the Tasmanian Devil

The impact of emerging infectious diseases is increasingly recognised as a major threat to wildlife. Wild populations of the endangered Tasmanian devil, Sarcophilus harrisii, are experiencing devastating losses from a novel transmissible cancer, devil facial tumour disease (DFTD); however, despite the rapid decline of this species, there is currently no information on the presence of haemoprotozoan parasites. In the present study, 95 Tasmanian devil blood samples were collected from four populations in Tasmania, Australia, which underwent molecular screening to detect four major groups of haemoprotozoa: (i) trypanosomes, (ii) piroplasms, (iii) Hepatozoon, and (iv) haemosporidia. Sequence results revealed Trypanosoma infections in 32/95 individuals. Trypanosoma copemani was identified in 10 Tasmanian devils from three sites and a second Trypanosoma sp. was identified in 22 individuals that were grouped within the poorly described T. cyclops clade. A single blood sample was positive for Babesia sp., which most closely matched Babesia lohae. No other blood protozoan parasite DNA was detected. This study provides the first insight into haemoprotozoa from the Tasmanian devil and the first identification of Trypanosoma and Babesia in this carnivorous marsupial.

Klebsiella pneumoniae: A pathogenic bacteria transmitted through Hirudo nipponia that may cause illness in humans

Hirudo nipponia, or the leech, is not only an important economic pillar for farmers, but is also a precious raw material for medicinal materials. However, in recent years, H. nipponia has suffered from disease with symptoms including systemic oedema and hyperaemia. It has not yet been demonstrated which pathogen causes this disease and whether this could be transmitted to humans. In this study, Klebsiella pneumoniae was isolated and identified and the pathogenicity of the isolated strain was confirmed. Furthermore, by comparing the sequence of the pathogen isolated from leeches to the same pathogen infecting humans, we identified that the isolated strain is a threat to human health. This work emphasizes the importance of the first discovery of pathogenic bacteria from leeches similar to human pathogens, as well as the need for identifying zoonosis for both humans and aquatic animals.

Native and Introduced Trypanosome Parasites in Endemic and Introduced Murine Rodents of Sulawesi

The Indonesian island of Sulawesi is a globally significant biodiversity hotspot with substantial undescribed biota, particularly blood-borne parasites of endemic wildlife. Documenting the blood parasites of Sulawesi's murine rodents is the first fundamental step towards the discovery of pathogens likely to be of concern for the health and conservation of Sulawesi's endemic murines. We screened liver samples from 441 specimens belonging to 20 different species of murine rodents from 2 mountain ranges on Sulawesi, using polymerase chin reaction (PCR) primers targeting the conserved 18S rDNA region across the protozoan class Kinetoplastea. We detected infections in 156 specimens (10 host species) with a mean prevalence of 35.4% (95% confidence interval [CI] = 30.9-39.8%). Sequences from these samples identified 4 infections to the genus Parabodo, 1 to Blechomonas, and the remaining 151 to the genus Trypanosoma. Within Trypanosoma, we recovered 17 haplotypes nested within the Trypanosoma theileri clade infecting 117 specimens (8 host species) and 4 haplotypes nested within the Trypanosoma lewisi clade infecting 34 specimens (6 host species). Haplotypes within the T. theileri clade were related to regional Indo-Australian endemic trypanosomes, displayed geographic structuring but with evidence of long-term connectivity between mountains, and had substantial phylogenetic diversity. These results suggest T. theileri clade parasites are native to Sulawesi. Conversely, T. lewisi clade haplotypes were recovered from both endemic and introduced rodents, demonstrated complete geographic separation between clades, and had low genetic diversity. These results suggest that the T. lewisi clade parasites invaded Sulawesi recently and likely in 2 separate invasion events. Our results provide the first records of metakinetoplastids in Sulawesi's rodents and highlight the need for more extensive sampling for pathogens in this biodiversity hotspot.

First report of Trypanosoma dionisii (Trypanosomatidae) identified in Australia

Trypanosomes are blood-borne parasites that can infect a variety of different vertebrates, including animals and humans. This study aims to broaden scientific knowledge about the presence and biodiversity of trypanosomes in Australian bats. Molecular and morphological analysis was performed on 86 blood samples collected from seven different species of microbats in Western Australia. Phylogenetic analysis on 18S rDNA and glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) sequences identified Trypanosoma dionisii in five different Australian native species of microbats; Chalinolobus gouldii, Chalinolobus morio, Nyctophilus geoffroyi, Nyctophilus major and Scotorepens balstoni. In addition, two novels, genetically distinct T. dionisii genotypes were detected and named T. dionisii genotype Aus 1 and T. dionisii genotype Aus 2. Genotype Aus 2 was the most prevalent and infected 20.9% (18/86) of bats in the present study, while genotype Aus 1 was less prevalent and was identified in 5.8% (5/86) of Australian bats. Morphological analysis was conducted on trypomastigotes identified in blood films, with morphological parameters consistent with trypanosome species in the subgenus Schizotrypanum. This is the first report of T. dionisii in Australia and in Australian native bats, which further contributes to the global distribution of this cosmopolitan bat trypanosome.

Molecular surveillance reveals bats from eastern Colombia infected with Trypanosoma theileri and Trypanosoma wauwau-like parasites

Several species of trypanosomes can infect bats (Chiroptera), but current information about bat trypanosomes in Colombia is scarce. The objectives of this study were to estimate the infection rate and to characterize the trypanosome species infecting bats from three rural regions near the municipality of Cumaribo in Vichada, Colombia. Blood samples were collected from 39 bats. DNA was extracted from the blood samples and analyzed using nuclear genetic markers (SSU rDNA, ITS rDNA, and cathepsin genes) to discriminate among trypanosome species. Trypanosomes were detected in 66.7 % (26/39) of blood samples using PCR; 61.5 % (24/39) of infections were identified as Trypanosoma theileri and 5.1 % (2/39) as T. wauwau-like parasites. The phylogeographic analysis revealed that our T. theileri sequences were associated with the TthIIB genotype from cattle in Brazil and Venezuela. The T. wauwau-like parasites represent a new genotype of the species and were found in Molossus molossus and Platyrrhinus helleri bats. These data represent the first evidence of this trypanosome in both Colombia, and in these species of bats. Bat infections with T. theileri suggest an important role of these hosts in maintaining this genotype, probably acquired by ingesting insect vectors. The T. wauwau-like genotype in new mammalian host species supports the 'bat seeding' hypothesis of the T. cruzi clade. The epidemiological and evolutionary implications of these findings are discussed.

Meta-transcriptomic identification of Trypanosoma spp. in native wildlife species from Australia

Background

Wildlife species carry a remarkable diversity of trypanosomes. The detection of trypanosome infection in native Australian fauna is central to understanding their diversity and host-parasite associations. The implementation of total RNA sequencing (meta-transcriptomics) in trypanosome surveillance and diagnosis provides a powerful methodological approach to better understand the host species distribution of this important group of parasites.

Methods

We implemented a meta-transcriptomic approach to detect trypanosomes in a variety of tissues (brain, liver, lung, skin, gonads) sampled from native Australian wildlife, comprising four marsupials (koala, Phascolarctos cinereus; southern brown bandicoot, Isoodon obesulus; swamp wallaby, Wallabia bicolor; bare-nosed wombat, Vombatus ursinus), one bird (regent honeyeater, Anthochaera phrygia) and one amphibian (eastern dwarf tree frog, Litoria fallax). Samples corresponded to both clinically healthy and diseased individuals. Sequencing reads were de novo assembled into contigs and annotated. The evolutionary relationships among the trypanosomatid sequences identified were determined through phylogenetic analysis of 18S rRNA sequences.

Results

We detected trypanosome sequences in all six species of vertebrates sampled, with positive samples in multiple organs and tissues confirmed by PCR. Phylogenetic analysis indicated that the trypanosomes infecting marsupials were related to those previously detected in placental and marsupial mammals, while the trypanosome in the regent honeyeater grouped with avian trypanosomes. In contrast, we provide the first evidence for a trypanosome in the eastern dwarf tree frog that was phylogenetically distinct from those described in other amphibians.

Conclusions

To our knowledge, this is the first meta-transcriptomic analysis of trypanosomes in native Australian wildlife, expanding the known genetic diversity of these important parasites. We demonstrated that RNA sequencing is sufficiently sensitive to detect low numbers of Trypanosoma transcripts and from diverse hosts and tissues types, thereby representing an effective means to detect trypanosomes that are divergent in genome sequence.

First record of infestation by nasal leeches, Limnatis nilotica (Hirudinida, Praobdellidae), from cattle in Italy

In July 2017, twenty cattle of a free-grazing herd were found to be infested with leeches in the mouth. Main signs were bloody sialorrhea and/or a purple-red colour of the lower lip. Leeches, in a variable number (1 to 3) per animal, were found at the lingual frenulum or on the sublingual vestibular mucosa and were morphologically identified as Limnatis nilotica. To the best of our knowledge, this is the first report of cattle infestation by L. nilotica in Italy. Besides recalling the attention to leech infestation and suggesting its inclusion in the differential diagnosis of animals with suggestive signs, this short report also provides practitioners with easy-going morphological keys for proper diagnosis and discrimination among species.

'Hang on a Tick' - Are Ticks Really the Vectors for Australian Trypanosomes?

Trypanosomes are global blood parasites that infect a wide range of vertebrate hosts. Several species of Trypanosoma cause disease in humans and domesticated animals, and the majority are transmitted between hosts by haematophagous invertebrate vectors. Ticks have long been speculated as vectors for Australian trypanosomes. Recent studies using advanced molecular techniques have refocused attention on these arthropods, and whilst they have renewed discussions about Trypanosoma species and their vectors, these reports have simultaneously led to premature conclusions concerning the role of ticks as vectors. Here the controversy surrounding ticks as trypanosome vectors is discussed. We highlight the unanswered questions concerning the role played by ticks in trypanosome transmission and suggest future approaches to resolving these key knowledge gaps.

Ideating iDNA: Lessons and limitations from leeches in legacy collections

Indirect methods for conducting faunal inventories present great promise, and genomic inventories derived from environmental sources (eDNA) are improving. Invertebrate ingested DNA (iDNA) from terrestrial leeches in the family Haemadipsidae has shown potential for surveying vertebrates and biodiversity monitoring in protected areas. Here we present an initial, and critical, evaluation of the limitations and biases of current iDNA protocols for biodiversity monitoring using both standard and NGS barcoding approaches. Key findings include the need for taxon relevant multi-locus markers and reference databases. In particular, the limitations of available reference databases have profound potential to mislead and bias eDNA and iDNA results if not critically interpreted. Nevertheless, there is great potential for recovery of amplifiable DNA from gut contents of invertebrate museum specimens which may reveal both temporal patterns and cryptic diversity in protected areas with increased efficiency. Our analyses of ingested DNA (iDNA) from both freshly stored and previously collected (legacy) samples of terrestrial leeches successfully identified vertebrates from Myanmar, Australia and Madagascar and indicate the potential to characterize microbial communities, pathogen diversity and interactions at low cost.

Haematozoa of wild catfishes in northern Australia

Very little is known about the diversity, prevalence, or pathogenicity of haematozoa in Australian freshwater fishes. Blood smears from 189 native catfishes, of six different species, from northern Australia were examined for haematozoa. Haematozoan infections were observed only in fishes from Queensland, at an overall prevalence of 0.191 (95% CI = 0.134-0.265). Intraerythrocytic haemogregarines were present in Neoarius graeffei from the Brisbane River at a prevalence of 0.35 (0.181-0.567). Trypanosomes were present in Tandanus species from four rivers, at prevalences ranging from 0.111 (0.020-0.330) to 1 (0.635-1), and in N. graeffei from one river in Queensland, at a prevalence of 0.063 (0.003-0.305). The haematozoans observed appeared to have little impact on their hosts. Tandanus spp. were significantly more likely to be infected with trypanosomes, suggesting a high parasite-host specificity. This is the first widespread survey of wild Australian freshwater catfishes for haematozoa, resulting in the first report of haemogregarines from Australian freshwater fish, and the first report of trypanosomes from Neoarius graeffei and Tandanus tropicanus.

Next generation sequencing reveals widespread trypanosome diversity and polyparasitism in marsupials from Western Australia

In Western Australia a number of indigenous Trypanosoma spp. infect susceptible native marsupials, such as the woylie (Bettongia penicillata), brushtail possum (Trichosurus vulpecula), and chuditch (Dasyurus geoffroii). Two genotypes of Trypanosoma copemani (identified as G1 and G2) have been found in the woylie, and G2 has been implicated in the decline of this host species, making its presence of particular interest. Here we used targeted amplicon next generation sequencing (NGS) of the Trypanosoma 18S rDNA loci on 70 Trypanosoma-positive marsupial blood samples, to identify T. copemani genotypes and multiple Trypanosoma infections (polyparasitism) in woylies and cohabiting species in Western Australia. Polyparasitism with Trypanosoma spp. was found in 50% of the wildlife sampled, and within species diversity was high, with 85 zero-radius operational taxonomic units (ZOTUs) identified in nine putative parasite species. Trypanosoma copemani was assigned 17 ZOTUs and was identified in 80% of samples. The most abundant ZOTU isolated (63%) differed slightly from the published genotype of G1, and G2 was the second most abundant ZOTU (14%). Trypanosome diversity was significantly greater in woylies than in brushtail possums, and parasite community composition also differed significantly between these host species. One novel Trypanosoma spp. genotype (Trypanosoma sp. ANU2) was found in 20% of samples. A species of Crithidia was detected in a woylie, and two avian trypanosomes (Trypanosoma avium and Trypanosoma sp. AAT) were identified in woylies for the first time.

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Extensive trypanosome diversity and polyparasitism in south Western Australia.

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A significant difference between trypanosomes infecting woylies and brushtail possums.

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Evidence that the current species-level taxonomy of Australian trypanosomes may need revision.

Wildlife parasitology in Australia: past, present and future

Wildlife parasitology is a highly diverse area of research encompassing many fields including taxonomy, ecology, pathology and epidemiology, and with participants from extremely disparate scientific fields. In addition, the organisms studied are highly dissimilar, ranging from platyhelminths, nematodes and acanthocephalans to insects, arachnids, crustaceans and protists. This review of the parasites of wildlife in Australia highlights the advances made to date, focussing on the work, interests and major findings of researchers over the years and identifies current significant gaps that exist in our understanding. The review is divided into three sections covering protist, helminth and arthropod parasites. The challenge to document the diversity of parasites in Australia continues at a traditional level but the advent of molecular methods has heightened the significance of this issue. Modern methods are providing an avenue for major advances in documenting and restructuring the phylogeny of protistan parasites in particular, while facilitating the recognition of species complexes in helminth taxa previously defined by traditional morphological methods. The life cycles, ecology and general biology of most parasites of wildlife in Australia are extremely poorly understood. While the phylogenetic origins of the Australian vertebrate fauna are complex, so too are the likely origins of their parasites, which do not necessarily mirror those of their hosts. This aspect of parasite evolution is a continuing area for research in the case of helminths, but remains to be addressed for many other parasitic groups.

A comparative molecular and 3-dimensional structural investigation into cross-continental and novel avian Trypanosoma spp. in Australia

BACKGROUND

Molecular and structural information on avian Trypanosoma spp. throughout Australia is limited despite their intrinsic value in understanding trypanosomatid evolution, diversity, and structural biology. In Western Australia tissue samples (n = 429) extracted from 93 birds in 25 bird species were screened using generic PCR primers to investigate the diversity of Trypanosoma spp. To investigate avian trypanosome structural biology the first 3-dimensional ultrastructural models of a Trypanosoma spp. (Trypanosoma sp. AAT) isolated from a bird (currawong, Strepera spp.) were generated using focussed ion beam milling combined with scanning electron microscopy (FIB-SEM).

RESULTS

Here, we confirm four intercontinental species of avian trypanosomes in native Australian birds, and identify a new avian Trypanosoma. Trypanosome infection was identified in 18 birds from 13 different bird species (19%). A single new genotype was isolated and found to be closely related to T. culicavium (Trypanosoma sp. CC2016 B002). Other Trypanosoma spp. identified include T. avium, T. culicavium, T. thomasbancrofti, Trypanosoma sp. TL.AQ.22, Trypanosoma sp. AAT, and an uncharacterised Trypanosoma sp. (group C-III sensu Zidková et al. (Infect Genet Evol 12:102-112, 2012)), all previously identified in Australia or other continents. Serially-sectioning Trypanosoma sp. AAT epimastigotes using FIB-SEM revealed the disc-shaped kinetoplast pocket attached perpendicular to the branching mitochondrion. Additionally, the universal minicircle sequence within the kinetoplast DNA and the associated binding protein were determined in Trypanosoma sp. AAT.

CONCLUSIONS

These results indicate that bird trypanosomes are relatively conserved across continents, while being locally diverse, which supports the hypothesis that bird trypanosomes exist as fewer species than described in the literature. Evidence exists that avian Trypanosoma spp. are infecting mammals and could be transmitted by haemadipsid leeches. Trypanosoma sp. AAT is most likely a separate species currently found only in Australia and the first 3-dimentional ultrastructural analysis of an avian trypanosome provides interesting information on their morphology and organelle arrangement.

Host-Parasite Relationships and Life Histories of Trypanosomes in Australia

Trypanosomes constitute a group of flagellate protozoan parasites responsible for a number of important, yet neglected, diseases in both humans and livestock. The most significantly studied include the causative agents of African sleeping sickness (Trypanosoma brucei) and Chagas disease (Trypanosoma cruzi) in humans. Much of our knowledge about trypanosome host-parasite relationships and life histories has come from these two human pathogens. Recent investigations into the diversity and life histories of wildlife trypanosomes in Australia highlight that there exists a great degree of biological and behavioural variation within and between trypanosomes. In addition, the genetic relationships between some Australian trypanosomes show that they are unexpectedly more closely related to species outside Australia than within it. These findings have led to a growing focus on the importance of understanding parasites occurring naturally in wildlife to (1) better document parasite biodiversity, (2) determine evolutionary relationships and degree of host specificity, (3) understand host-parasite interactions and the role of parasites in the natural ecosystem and (4) identify biosecurity issues of emerging disease in both wildlife and human populations. Here we review what is known about the diversity, life histories, host-parasite interactions and evolutionary relationships of trypanosomes in Australian wildlife. In this context, we focus upon the genetic proximity of key Australian species to the pathogenic T. cruzi and discuss similarities in their biology and behaviour that present a potential risk of human disease transmission by Australian vectors and wildlife.

Biodiversity of parasite assemblages in the genus Petrogale and its relation to the phylogeny and biogeography of their hosts

Parasites form an integral part of overall biodiversity although they are often overlooked in conservation management, where emphasis is primarily directed towards the host. Parasites are often highly specialised to particular hosts, and thus may be just as threatened as the host they inhabit. For many of Australia’s wildlife species, little is known about their associated parasite communities. To begin to address this knowledge gap, we documented the parasite fauna described in the genetically diverse marsupial genus Petrogale, which contains seven species of conservation concern. The literature evaluation showed parasites of Petrogale to be highly diverse, with 17 species of protozoa, 8 species of cestodes, 102 species of nematodes and 30 species of ectoparasites identified in 16 of 17 Petrogale host species. A comparison of the parasite communities amongst Petrogale host species indicated a highly significant correlation between the parasite community similarity, and the phylogeny (P = 0.008) and biogeography (P = 0.0001) of their Petrogale hosts, suggesting high host specificity within their associated parasite assemblages. Five Petrogale species have established species recovery programs and their parasite communities should also be considered threatened, and management of parasite diversity required as part of these conservation programs.

Field and experimental evidence of a new caiman trypanosome species closely phylogenetically related to fish trypanosomes and transmitted by leeches

Trypanosoma terena and Trypanosoma ralphi are known species of the South American crocodilians Caiman crocodilus, Caiman yacare and Melanosuchus niger and are phylogenetically related to the tsetse-transmitted Trypanosoma grayi of the African Crocodylus niloticus. These trypanosomes form the Crocodilian clade of the terrestrial clade of the genus Trypanosoma. A PCR-survey for trypanosomes in caiman blood samples and in leeches taken from caimans revealed unknown trypanosome diversity and frequent mixed infections. Phylogenies based on SSU (small subunit) of rRNA and gGAPDH (glycosomal Glyceraldehyde Phosphate Dehydrogenase) gene sequences revealed a new trypanosome species clustering with T. terena and T. ralphi in the crocodilian clade and an additional new species nesting in the distant Aquatic clade of trypanosomes, which is herein named Trypanosoma clandestinus n. sp. This new species was found in Caiman yacare, Caiman crocodilus and M. niger from the Pantanal and Amazonian biomes in Brazil. Large numbers of dividing epimastigotes and unique thin and long trypomastigotes were found in the guts of leeches (Haementeria sp.) removed from the mouths of caimans. The trypanosomes recovered from the leeches had sequences identical to those of T. clandestinus of caiman blood samples. Experimental infestation of young caimans (Caiman yacare) with infected leeches resulted in long-lasting T. clandestinus infections that permitted us to delineate its life cycle. In contrast to T. terena, T. ralphi and T. grayi, which are detectable by hemoculturing, microscopy and standard PCR of caiman blood, T. clandestinus passes undetected by these methods due to very low parasitemia and could be detected solely by the more sensitive nested PCR method. T. clandestinus n. sp. is the first crocodilian trypanosome known to be transmitted by leeches and positioned in the aquatic clade closest to fish trypanosomes. Our data show that caimans can host trypanosomes of the aquatic or terrestrial clade, sometimes simultaneously.

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Species richness and geographical range of caiman trypanosomes.

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Trypanosoma clandestinus n. sp. is transmitted by leeches.

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T. clandestinus nests in the Aquatic clade closest to fish trypanosomes.

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Caimans were infected by the bite of leeches carrying T. clandestinus.

Phylogeny and Morphological Variability of Trypanosomes from African Pelomedusid Turtles with Redescription of Trypanosoma mocambicum Pienaar, 1962

Little is known about host specificity, genetic diversity and phylogenetic relationships of African turtle trypanosomes. Using PCR targeting the SSU rRNA gene, we detected trypanosomes in 24 of 134 (17.9%) wild caught African pelomedusid turtles: Pelusios upembae (n=14), P. bechuanicus (n=1), P. rhodesianus (n=3) and P. subniger (n=6). Mixed infection of Trypanosoma species was confirmed by PCR in three specimens of P. upembae, and in one specimen each of P. bechuanicus, P. rhodesianus, and P. subniger. Microscopic examination of stained blood smears revealed two distinct forms (broad and slender) of trypomastigotes. The broad form coincided in morphology with T. mocambicumPienaar, 1962. Accordingly, we have designated this form as the neotype of T. mocambicum. In phylogenetic analysis of the SSU rRNA gene, all the new turtle trypanosome sequences grouped in a single clade within the strongly supported "aquatic" clade of Trypanosoma species. The turtle trypanosome clade was further subdivided into two subclades, which did not correlate with host turtle species or trypanosome morphology. This study provides the first sequence data of Trypanosoma species isolated from freshwater turtles from tropical Africa and extends knowledge on diversity of trypanosomes in the Afrotropical zoogeographical realm.

Investigation of the morphological diversity of the potentially zoonotic Trypanosoma copemani in quokkas and Gilbert's potoroos

Trypanosomes are blood-borne parasites that can cause severe disease in both humans and animals, yet little is known of the pathogenicity and life-cycles of trypanosomes in native Australian mammals. Trypanosoma copemani is known to be infective to a variety of Australian marsupials and has recently been shown to be potentially zoonotic as it is resistant to normal human serum. In the present study, in vivo and in vitro examination of blood and cultures from Australian marsupials was conducted using light microscopy, immunofluorescence, scanning electron microscopy and fluorescence in situ hybridization. Promastigote, sphaeromastigote and amastigote life-cycle stages were detected in vivo and in vitro. Novel trypanosome-like stages were also detected both in vivo and in vitro representing an oval stage, an extremely thin stage, an adherent stage and a tiny round stage. The tiny round and adherent stages appeared to adhere to erythrocytes causing potential haematological damage with clinical effects similar to haemolytic anaemia. The present study shows for the first time that trypomastigotes are not the only life-cycle stages circulating within the blood stream of trypanosome infected Australian native marsupials and provides insights into possible pathogenic mechanisms of this potentially zoonotic trypanosome species.

Phytomonas: trypanosomatids adapted to plant environments

Over 100 years after trypanosomatids were first discovered in plant tissues, Phytomonas parasites have now been isolated across the globe from members of 24 different plant families. Most identified species have not been associated with any plant pathology and to date only two species are definitively known to cause plant disease. These diseases (wilt of palm and coffee phloem necrosis) are problematic in areas of South America where they threaten the economies of developing countries. In contrast to their mammalian infective relatives, our knowledge of the biology of Phytomonas parasites and how they interact with their plant hosts is limited. This review draws together a century of research into plant trypanosomatids, from the first isolations and experimental infections to the recent publication of the first Phytomonas genomes. The availability of genomic data for these plant parasites opens a new avenue for comparative investigations into trypanosomatid biology and provides fresh insight into how this important group of parasites have adapted to survive in a spectrum of hosts from crocodiles to coconuts.

Novel genotypes of Trypanosoma binneyi from wild platypuses (Ornithorhynchus anatinus) and identification of a leech as a potential vector

Little is known about the prevalence and pathogenesis of trypanosomes in Australian monotremes, and few genetic characterisation studies have been conducted with these haemoparasites. During the present investigation, molecular and microscopic methods were used to screen peripheral blood (n=28) and ectoparasites (n=10 adult ticks; n=5 tick nymphs; n=1 leech; and n>500 tick eggs) collected from wild Tasmanian platypuses (Ornithorhynchus anatinus), for the presence of trypanosomatid-specific DNA and/or trypomastigotes. The genes for the small ribosomal subunit RNA (18S rDNA) and glycosomal glyceraldehyde phosphate dehydrogenase (gGAPDH) were amplified and sequenced, prior to conducting phylogenetic analyses. The detection rate of the parasite-specific 18S rDNA in platypus blood was 85.7% (n=24/28), and the leech was also positive at both loci. Microscopically, high parasitaemia and the presence of abundant trypomastigotes, morphologically consistent with Trypanosoma binneyi Mackerras (1959), were observed in the blood films. Phylogenetic analyses at the 18S locus revealed the existence of four trypanosomatid-like genotypes, with variable similarity to two previously-described genotypes of T. binneyi (range of genetic p-distance: 0.0-0.5%). For the gGAPDH locus, for which only one T. binneyi sequence is available in GenBank, three genotypes closely related T. binneyi were identified (range of genetic p-distance: 0.1-0.4%). The leech-derived trypanosome isolate was virtually identical (at the two loci studied) to the other parasites sequenced from infected platypuses; however, the molecular or morphological identification of the leech species was not possible. Although further studies are required, the molecular detection of trypanosomes in an aquatic leech removed from a platypus, suggests the possibility that these haematophagous hirudineans may be a vector for T. binneyi (and closely related genotypes).

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.

Free-living ciliates as potential reservoirs for eukaryotic parasites: occurrence of a trypanosomatid in the macronucleus of Euplotes encysticus

Background

Flagellates of the family Trypanosomatidae are obligate endoparasites, which can be found in various hosts. Several genera infect insects and occur as monoxenous parasites especially in representatives of Diptera and Hemiptera. These trypanosomatid flagellates probably share the worldwide distribution of their hosts, which are often infested by large numbers of endoparasites. Traditionally, their taxonomy was based on morphology, host origin, and life cycle. Here we report the characterization of a trypanosomatid infection detected in a protozoan, a ciliate collected from a polluted freshwater pond in a suburb of New Delhi (India).

Methods

Live observations and morphological studies applying light, fluorescence and transmission electron microscopy were conducted. Molecular analyses of host and parasite were performed and used for phylogenetic reconstructions and species (host) or genus level (parasite) identification.

Results

Although the morphological characteristics were not revealing, a high similarity of the trypanosomatids 18S rRNA gene sequence to Herpetomonas ztiplika and Herpetomonas trimorpha (Kinetoplastida, Trypanosomatidae), both parasites of biting midges (Culicoides kibunensis and Culicoides truncorum, respectively) allowed the assignment to this genus. The majority of the host population displayed a heavy infection that significantly affected the shape of the host macronucleus, which was the main site of parasite localization. In addition, the growth rate of host cultures, identified as Euplotes encysticus according to cell morphology and 18S rRNA gene sequence, was severely impacted by the infection.

Conclusions

The host-parasite system described here represents a recent example of free-living protists acting as environmental reservoirs for parasitic eukaryotic microorganisms.

Temporal and spatial dynamics of trypanosomes infecting the brush-tailed bettong (Bettongia penicillata): a cautionary note of disease-induced population decline

BACKGROUND

The brush-tailed bettong or woylie (Bettongia penicillata) is on the brink of extinction. Its numbers have declined by 90% since 1999, with their current distribution occupying less than 1% of their former Australian range. Woylies are known to be infected with three different trypanosomes (Trypanosoma vegrandis, Trypanosoma copemani and Trypanosoma sp. H25) and two different strains of T. copemani that vary in virulence. However, the role that these haemoparasites have played during the recent decline of their host is unclear and is part of ongoing investigation.

METHODS

Woylies were sampled from five locations in southern Western Australia, including two neighbouring indigenous populations, two enclosed (fenced) populations and a captive colony. PCR was used to individually identify the three different trypanosomes from blood and tissues of the host, and to investigate the temporal and spatial dynamics of trypanosome infections.

RESULTS

The spatial pattern of trypanosome infection varied among the five study sites, with a greater proportion of woylies from the Perup indigenous population being infected with T. copemani than from the neighbouring Kingston indigenous population. For an established infection, T. copemani detection was temporally inconsistent. The more virulent strain of T. copemani appeared to regress at a faster rate than the less virulent strain, with the infection possibly transitioning from the acute to chronic phase. Interspecific competition may also exist between T. copemani and T. vegrandis, where an existing T. vegrandis infection may moderate the sequential establishment of the more virulent T. copemani.

CONCLUSION

In this study, we provide a possible temporal connection implicating T. copemani as the disease agent linked with the recent decline of the Kingston indigenous woylie population within the Upper Warren region of Western Australia. The chronic association of trypanosomes with the internal organs of its host may be potentially pathogenic and adversely affect their long term fitness and coordination, making the woylie more susceptible to predation.

Trypanosomes of Australian mammals: A review

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Trypanosomes of Australian marsupials, rodents, bats and monotremes are reviewed.

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22% of the indigenous terrestrial and arboreal mammals have been screened.

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Trypanosomes have been identified from 28 mammal species.

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Eight native trypanosome species have been described from Australian mammals

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Potential pathogenic risks and threatening biosecurity concerns are discussed.

Approximately 306 species of terrestrial and arboreal mammals are known to have inhabited the mainland and coastal islands of Australia at the time of European settlement in 1788. The exotic Trypanosoma lewisi was the first mammalian trypanosome identified in Australia in 1888, while the first native species, Trypanosoma pteropi, was taxonomically described in 1913. Since these discoveries, about 22% of the indigenous mammalian fauna have been examined during the surveillance of trypanosome biodiversity in Australia, including 46 species of marsupials, 9 rodents, 9 bats and both monotremes. Of those mammals examined, trypanosomes have been identified from 28 host species, with eight native species of Trypanosoma taxonomically described. These native trypanosomes include T. pteropi, Trypanosoma thylacis, Trypanosoma hipposideri, Trypanosoma binneyi, Trypanosoma irwini, Trypanosoma copemani, Trypanosoma gilletti and Trypanosoma vegrandis. Exotic trypanosomes have also been identified from the introduced mammalian fauna of Australia, and include T. lewisi, Trypanosoma melophagium, Trypanosoma theileri, Trypanosoma nabiasi and Trypanosoma evansi. Fortunately, T. evansi was eradicated soon after its introduction and did not establish in Australia. Of these exotic trypanosomes, T. lewisi is the sole representative that has been reported from indigenous Australian mammals; morphological forms were recorded from two indigenous species of rodents (Hydromys chrysogaster and Rattus fuscipes). Numerous Australian marsupial species are potentially at risk from the native T. copemani, which may be chronically pathogenic, while marsupials, rodents and monotremes appear at risk from exotic species, including T. lewisi, Trypanosoma cruzi and T. evansi. This comprehensive review of trypanosome biodiversity in Australia highlights the negative impact of these parasites upon their mammalian hosts, as well as the threatening biosecurity concerns.

Pruritis and palpable purpura from leeches in the Australian Rainforest

Leeches are prevalent in the Australian Rainforest. We report two cases of leech bites resulting in pruritis and palpable purpura. The dermatologic sequelae of leech bites, differential diagnosis of pruritic palpable purpura, leech bite treatment, prevention, and complications are reviewed.

Morphological and molecular characterization and phylogenetic relationships of a new species of trypanosome in Tapirus terrestris (lowland tapir), Trypanosoma terrestris sp. nov., from Atlantic Rainforest of southeastern Brazil

Background

The Lowland tapir (Tapirus terrestris) is the largest Brazilian mammal and despite being distributed in various Brazilian biomes, it is seriously endangered in the Atlantic Rainforest. These hosts were never evaluated for the presence of Trypanosoma parasites.

Methods

The Lowland tapirs were captured in the Brazilian southeastern Atlantic Rainforest, Espírito Santo state. Trypanosomes were isolated by hemoculture, and the molecular phylogeny based on small subunit rDNA (SSU rDNA) and glycosomal-3-phosphate dehydrogenase (gGAPDH) gene sequences and the ultrastructural features seen via light microscopy and scanning and transmission electron microscopy are described.

Results

Phylogenetic trees using combined SSU rDNA and gGAPDH data sets clustered the trypanosomes of Lowland tapirs, which were highly divergent from other trypanosome species. The phylogenetic position and morphological discontinuities, mainly in epimastigote culture forms, made it possible to classify the trypanosomes from Lowland tapirs as a separate species.

Conclusions

The isolated trypanosomes from Tapirus terrestris are a new species, Trypanosoma terrestris sp. n., and were positioned in a new Trypanosoma clade, named T. terrestris clade.

Electronic supplementary material

The online version of this article (doi:10.1186/1756-3305-6-349) contains supplementary material, which is available to authorized users.

Genome organization is a major component of gene expression control in response to stress and during the cell division cycle in trypanosomes

The trypanosome genome is characterized by RNA polymerase II-driven polycistronic transcription of protein-coding genes. Ten to hundreds of genes are co-transcribed from a single promoter; thus, selective regulation of individual genes via initiation is impossible. However, selective responses to external stimuli occur and post-transcriptional mechanisms are thought to account for all temporal gene expression patterns. We show that genes encoding mRNAs that are differentially regulated during the heat-shock response are selectively positioned in polycistronic transcription units; downregulated genes are close to transcription initiation sites and upregulated genes are distant. We demonstrate that the position of a reporter gene within a transcription unit is sufficient to reproduce this effect. Analysis of gene ontology annotations reveals that positional bias is not restricted to stress-response genes and that there is a genome-wide organization based on proximity to transcription initiation sites. Furthermore, we show that the relative abundance of mRNAs at different time points in the cell division cycle is dependent on the location of the corresponding genes to transcription initiation sites. This work provides evidence that the genome in trypanosomes is organized to facilitate co-coordinated temporal control of gene expression in the absence of selective promoters.

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.

The evolution of Trypanosoma cruzi: the 'bat seeding' hypothesis

Recent discussions on the evolution of Trypanosoma cruzi have been dominated by the southern super-continent hypothesis, whereby T. cruzi and related parasites evolved in isolation in the mammals of South America, Antarctica and Australia. Here, we consider recent molecular evidence suggesting that T. cruzi evolved from within a broader clade of bat trypanosomes, and that bat trypanosomes have successfully made the switch into other mammalian hosts in both the New and Old Worlds. Accordingly, we propose an alternative hypothesis--the bat seeding hypothesis--whereby lineages of bat trypanosomes have switched into terrestrial mammals, thereby seeding the terrestrial lineages within the clade. One key implication of this finding is that T. cruzi may have evolved considerably more recently than previously envisaged.

Vector of Trypanosoma copemani identified as Ixodes sp

A total of 41 ticks were collected from 15 quokkas on Bald Island and 2 ticks from a Gilbert's potoroo from Two Peoples Bay. Three species of Ixodid ticks Ixodes australiensis, Ixodes hirsti and Ixodes myrmecobii were identified on the quokkas known to have a high prevalence of Trypanosoma copemani. Tick faeces from ticks isolated from 8 individual quokkas and a Gilbert's potoroo were examined with one identified as positive for trypanosomes. Faecal examination revealed trypanosomes similar to in vitro life-cycle stages of T. copemani. In total 12 ticks were dissected and trypanosomes found in sections of their midgut and haemolymph, 49 and 117 days after collection. Tick faeces, salivary glands and midguts from I. australiensis were screened using an 18S rRNA PCR with amplification seen only from the midguts. Sequencing showed 100% homology to T. copemani (genotype A) and 99·9% homology to the wombat (AII) isolate of T. copemani. Trypanosomes were only detected in I. australiensis as neither I. hirsti nor I. myrmecobii survived the initial 30-day storage conditions. We therefore identify a vector for T. copemani as I. australiensis and, given the detection of trypanosomes in the faeces, suggest that transmission is via the faecal-oral route.

Evidence for a role of the host-specific flea (Paraceras melis) in the transmission of Trypanosoma (Megatrypanum) pestanai to the European badger

We investigated the epidemiology of Trypanosoma pestanai infection in European badgers (Meles meles) from Wytham Woods (Oxfordshire, UK) to determine prevalence rates and to identify the arthropod vector responsible for transmission. A total of 245 badger blood samples was collected during September and November 2009 and examined by PCR using primers derived from the 18S rRNA of T. pestanai. The parasite was detected in blood from 31% of individuals tested. T. pestanai was isolated from primary cultures of Wytham badger peripheral blood mononuclear cells and propagated continually in vitro. This population was compared with cultures of two geographically distinct isolates of the parasite by amplified fragment length polymorphism (AFLP) and PCR analysis of 18S rDNA and ITS1 sequences. High levels of genotypic polymorphism were observed between the isolates. PCR analysis of badger fleas (Paraceras melis) collected from infected individuals at Wytham indicated the presence of T. pestanai and this was confirmed by examination of dissected specimens. Wet smears and Giemsa-stained preparations from dissected fleas revealed large numbers of trypanosome-like forms in the hindgut, some of which were undergoing binary fission. We conclude that P. melis is the primary vector of T. pestanai in European badgers.

Diagnóstico y caracterización molecular de infecciones naturales por Trypanosoma spp. en bovinos de la Orinoquía Colombiana

Debido a las limitaciones que tienen los métodos directos para el diagnóstico de tripanosomas en bajas cantidades, los métodos moleculares permiten la identificación de la especie con una pequeña cantidad del ADN del parásito. Se realizó un estudio en la Estación Experimental Carimagua ubicada en la altillanura plana de la Orinoquía Colombiana, con una población de 500 bovinos de cría de las razas Cebú y Sanmartinero nacidos en la zona, se seleccionaron de manera aleatoria 70 animales clínicamente sanos, con el fin de establecer la presencia de Trypanosoma spp. y realizar un diagnóstico diferencial entre especies. Se tomaron muestras de sangre en las cuales, se separaron glóbulos blancos mediante la técnica de Buffy Coat, y se realizó PCR semi-anidado sobre la región 18S del rDNA. Sobre los productos obtenidos se realizó el RFLPS y su comparación con estándares internacionales. Cinco muestras por PCR fueron positivas a Trypanosoma spp., de las cuales una correspondió a T. vivax y 4 a T. theileri. Los resultados obtenidos permiten estimar sobre la población analizada, una prevalencia del Trypanosoma spp. de 7,14 % en animales aparentemente sanos, no diagnosticables por pruebas de detección directa usadas tradicionalmente, lo que constituye un potencial problema para la ganadería bovina de la zona, dada la posibilidad de desarrollar cuadros clínicos de la enfermedad y de su potencial transmisibilidad a animales susceptibles. Contar con métodos que determinen especies del Trypanosoma spp., permitirá igualmente un mejor manejo y comprensión del problema de campo. Las metodologías descritas, son la primera aproximación molecular de Trypanosoma spp. realizada en ganaderías de la Orinoquía Colombiana y ponen de manifiesto su importancia en el diagnóstico de la enfermedad. Diagnosis and molecular characterization of natural cattle infections produced by Trypanosoma spp. in the Colombian Orinoco region.Because of the limitations of direct methods for the diagnosis of trypanosomes in small quantities, molecular methods which allow identification of the species with a small amount of parasite DNA were analyzed. A study was conducted at the Carimagua Experimental Station, located in the flat high plains of Orinoco Colombia. From 500 'Sanmartinero' and 'Zebú' breeding cattle, native to the area, 70 clinically healthy animals were randomly selected, to establish the presence of Trypanosoma spp. and to perform differential diagnosis between species. Blood samples were taken and linfocites were separated by the Buffy Coat technique. Seminested PCR was performed on the 18S rDNA region. RFLP was run on the obtained products and a comparison with international standards was made. Five samples were positive for Trypanosoma spp. by PCR. One of them corresponded to T. vivax and four to T. theileri. The results obtained estimate a prevalence of 7.14% in apparently healthy animals, otherwise not detected by traditional direct tests currently in use. This poses a potential problem for cattle in the area, given the chance of developing clinical symptoms of the disease and the likelihood of transmission to susceptible animals. Having methods to detect presence of the species Trypanosoma spp., also permits better management and understanding of the field problem. The methods described are the first molecular approach to study Trypanosoma spp. in cattle in the Colombian Orinoco region and highlight the importance of diagnosis of the disease. 

Novel trypanosome Trypanosoma gilletti sp. (Euglenozoa: Trypanosomatidae) and the extension of the host range of Trypanosoma copemani to include the koala ( Phascolarctos cinereus)

Trypanosoma irwini was previously described from koalas and we now report the finding of a second novel species, T. gilletti, as well as the extension of the host range of Trypanosoma copemani to include koalas. Phylogenetic analysis at the 18S rDNA and gGAPDH loci demonstrated that T. gilletti was genetically distinct with a genetic distance (± s.e.) at the 18S rDNA locus of 2.7 ± 0.5% from T. copemani (wombat). At the gGAPDH locus, the genetic distance (± s.e.) of T. gilletti was 8.7 ± 1.1% from T. copemani (wombat). Trypanosoma gilletti was detected using a nested trypanosome 18S rDNA PCR in 3/139 (∼2%) blood samples and in 2/29 (∼7%) spleen tissue samples from koalas whilst T. irwini was detected in 72/139 (∼52%) blood samples and T. copemani in 4/139 (∼3%) blood samples from koalas. In addition, naturally occurring mixed infections were noted in 2/139 (∼1.5%) of the koalas tested.