The ancient and divergent origins of the human pathogenic trypanosomes, Trypanosoma brucei and T. cruzi

Morphological and molecular characteristics of a Trypanosoma sp. from triatomines (Triatoma rubrofasciata) in China

BACKGROUND

Triatomines (kissing bugs) are natural vectors of trypanosomes, which are single-celled parasitic protozoans, such as Trypanosoma cruzi, T. conorhini and T. rangeli. The understanding of the transmission cycle of T. conorhini and Triatoma rubrofasciata in China is not fully known.

METHODS

The parasites in the faeces and intestinal contents of the Tr. rubrofasciata were collected, and morphology indices were measured under a microscope to determine the species. DNA was extracted from the samples, and fragments of 18S rRNA, heat shock protein 70 (HSP70) and glycosomal glyceraldehyde-3-phosphate dehydrogenase (gGAPDH) were amplified and sequenced. The obtained sequences were then identified using the BLAST search engine, followed by several phylogenetic analyses. Finally, laboratory infections were conducted to test whether Tr. rubrofasciata transmit the parasite to rats (or mice) through bites. Moreover, 135 Tr. rubrofasciata samples were collected from the Guangxi region and were used in assays to investigate the prevalence of trypanosome infection.

RESULTS

Trypanosoma sp. were found in the faeces and intestinal contents of Tr. rubrofasciata, which were collected in the Guangxi region of southern China and mostly exhibited characteristics typical of epimastigotes, such as the presence of a nucleus, a free flagellum and a kinetoplast. The body length ranged from 6.3 to 33.9 µm, the flagellum length ranged from 8.7 to 29.8 µm, the nucleus index was 0.6 and the kinetoplast length was -4.6. BLAST analysis revealed that the 18S rRNA, HSP70 and gGAPDH sequences of Trypanosoma sp. exhibited the highest degree of similarity with those of T. conorhini (99.7%, 99.0% and 99.0%, respectively) and formed a well-supported clade close to T. conorhini and T. vespertilionis but were distinct from those of T. rangeli and T. cruzi. Laboratory experiments revealed that both rats and mice developed low parasitaemia after inoculation with Trypanosoma sp. and laboratory-fed Tr. rubrofasciata became infected after feeding on trypanosome-positive rats and mice. However, the infected Tr. rubrofasciata did not transmit Trypanosoma sp. to their offspring. Moreover, our investigation revealed a high prevalence of Trypanosoma sp. infection in Tr. rubrofasciata, with up to 36.3% of specimens tested in the field being infected.

CONCLUSIONS

Our study is the first to provide a solid record of T. conorhini from Tr. rubrofasciata in China with morphological and molecular evidence. This Chinese T. conorhini is unlikely to have spread through transovarial transmission in Tr. rubrofasciata, but instead, it is more likely that the parasite is transmitted between Tr. rubrofasciata and mice (or rats). However, there was a high prevalence of T. conorhini in the Tr. rubrofasciata from our collection sites and numerous human cases of Tr. rubrofasciata bites were recorded. Moreover, whether these T. conorhini strains are pathogenic to humans has not been investigated.

Trypanosoma sp. infection in Boa constrictor snakes: morphological, hematological, clinical biochemistry, molecular, and phylogenetic characteristics

There are few reports of Trypanosoma in snakes, as well as little information about its pathogenicity in these animals. Thus, the present study aimed to characterize Trypanosoma found in Boa constrictor snakes, to verify the influence of the parasitism on hematological and clinical biochemistry parameters, and to perform a phylogenetic study of the isolates. Blood samples from sixty-one boas were analyzed for the presence of trypanosomatids and by hematological and clinical biochemistry assays. The flagellates that were found in this analysis were used for cell culture, morphometry, and molecular analysis. Later, molecular typing phylogenetic studies were performed. Nine positive animals (14.75%) were identified by microscopy analysis. The hematological results showed that parasitized animals presented significantly lower levels of packed cell volume, hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin. In the leukogram, eosinophils and heterophils counts were higher in parasitized animals. Considering the molecular analyses, the isolates presented a higher identity of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and the 18S small subunit ribosomal RNA (SSU rRNA) gene fragments with Trypanosoma serpentis. The phylogenetic tree, using the GAPDH, clustered all isolates with T. serpentis and Trypanosoma cascavelli. This is the first description of T. serpentis parasitizing boas and of the clinical changes caused by trypanosomatid infection in snakes.

Parasitological and molecular detection of Trypanosoma evansi in a dog from Tocache, San Martin, Peru

This study presents the first case report of canine trypanosomiasis caused by Trypanosoma evansi in Peru. The case was admitted to a veterinary clinic in the Peruvian Amazon region of San Martin with severe clinical symptomatology which resulted in the dog's death. Microscopy screening showed the presence of trypomastigotes in blood and bone marrow and postmortem histopathology found damage at the cardiac, lung, kidney and spleen levels. Collected specimens were tested by nested-PCR which were positive for Trypanosoma spp., but negative for T. cruzi. High-throughput sequencing determined that the infecting species was closely related to T. equiperdom/evansi and subsequent phylogenetic analysis confirmed that the sample was related to T. evansi. The presence of T. evansi in the area highlights the need for increased surveillance to assess the impact of surra in the region and to develop measures to prevent socioeconomic damage resulting from infections in domestic and farm animals as well as prevent zoonotic transmission.

Species diversity of phlebotomine sand flies and sympatric occurrence of Leishmania (Mundinia) martiniquensis, Leishmania (Leishmania) donovani complex, and Trypanosoma spp. in the visceral leishmaniasis focus of southern Thailand

Autochthonous leishmaniasis in Thailand has recently been a public health concern due to an increasing number of new clinical cases. Most indigenous cases were diagnosed with Leishmania (Mundinia) martiniquensis, and Leishmania (Mundinia) orientalis. However, some doubts regarding vector misidentification have arisen and need to be elucidated. Accordingly, we aimed to assess the species composition of sand flies and determine the molecular prevalence of trypanosomatids in the transmission area of leishmaniasis in southern Thailand. In the present study, a total of 569 sand flies were caught from the vicinity of a visceral leishmaniasis patient's house in Na Thawi District, Songkhla Province. Of these, 229 parous and gravid females consisted of Sergentomyia khawi, Se. barraudi, Phlebotomus stantoni, Grassomyia indica, and Se. hivernus, accounting for 31.4%, 30.6%, 29.7%, 7.9%, and 0.4%, respectively. However, Se. gemmea, which has previously been proposed as the most abundant species and putative vector of visceral leishmaniasis, was not found in the present study. Based on ITS1-PCR and sequence analysis, two specimens of Gr. indica and Ph. stantoni showed positive amplification of L. martiniquensis and L. donovani complex, respectively, the first one being presumed indigenous and the second one being not. Anuran Trypanosoma was also molecularly detected using SSU rRNA-PCR and ubiquitously found in sixteen specimens of four dominant sand fly species except for Se. hivernus. The obtained sequences could be phylogenetically categorized into the two major amphibian clades (An04/Frog1 and An01+An02/Frog2). The existence of the monophyletic subgroup and distinct lineage suggests them as novel Trypanosoma species. The TCS network analysis of these anuran Trypanosoma sequences also revealed high haplotype diversity (Hd = 0.925 ± 0.050), but low nucleotide diversity (π = 0.019 ± 0.009). Furthermore, the living anuran trypanosomes were microscopically demonstrated in a single specimen of Gr. indica, supporting the vectorial capacity. Importantly, our data confirmed the scarcity of Se. gemmea and also uncovered, for the first time, the co-circulation of L. martiniquensis, L. donovani complex, and suspected novel anuran Trypanosoma spp. in phlebotomine sand files, implicating their potential role as vectors of trypanosomatid parasites. Therefore, the novel data from this study would greatly facilitate the comprehension of the complexity of trypanosomatid transmission and the establishment of prevention and control measures for this neglected disease more effectively.

Molecular prevalence, associated risk factors and genetic characterization of Trypanosoma evansi in camels

Surra is a major infectious disease of camels being caused by Trypanosoma evansi (T. evansi) in developing countries, including Egypt. However, the identification of changes in the T. evansi prevalence in Egypt is important. In this study, the prevalence of T. evansi and its associated risk factors as well as the genetic characterization of the parasite were estimated. Blood samples were collected from 163 camels from two governorates in Lower Egypt. PCR targeting RoTat 1.2VSG was used for the detection of T. evansi and internal transcribed spacer 1 (ITS-1) was used for sequencing analysis and genetic characterization. Overall prevalence was 19.6% using RoTat 1.2VSG. The risk of the infection in females was 4 times higher than in males (P = 0.0004, OR = 4; 95% CI = 0.79-8.96) and in camels with a history of clinical signs it was 2.3 times higher than camels without clinical signs (P = 0.04, OR = 2.3, 95% CI = 1.035-5.15). Analysis of the ITS-1 sequences of four T. evansi isolates showed little heterogeneity compared to similar sequences in the database. Sequence and phylogenetic analysis, based on the ITS-1 region, confirmed the presence of two distinct genotypes of T. evansi in Egyptian camels with more than 99% similarity with T. evansi isolates from different countries across the ITS-1 region and were closely related to Filipino and Chinese isolates. The results of the study can be used for the observation and prevention of disease and updating the epidemiological data.

Pseudokinase NRP1 facilitates endocytosis of transferrin in the African trypanosome

Trypanosoma brucei causes human African trypanosomiasis (HAT) and nagana in cattle. During infection of a vertebrate, endocytosis of host transferrin (Tf) is important for viability of the parasite. The majority of proteins involved in trypanosome endocytosis of Tf are unknown. Here we identify pseudokinase NRP1 (Tb427tmp.160.4770) as a regulator of Tf endocytosis. Genetic knockdown of NRP1 inhibited endocytosis of Tf without blocking uptake of bovine serum albumin. Binding of Tf to the flagellar pocket was not affected by knockdown of NRP1. However the quantity of Tf per endosome dropped significantly, consistent with NRP1 promoting robust capture and/or retention of Tf in vesicles. NRP1 is involved in motility of Tf-laden vesicles since distances between endosomes and the kinetoplast were reduced after knockdown of the gene. In search of possible mediators of NRP1 modulation of Tf endocytosis, the gene was knocked down and the phosphoproteome analyzed. Phosphorylation of protein kinases forkhead, NEK6, and MAPK10 was altered, in addition to EpsinR, synaptobrevin and other vesicle-associated proteins predicted to be involved in endocytosis. These candidate proteins may link NRP1 functionally either to protein kinases or to vesicle-associated proteins.

Preclinical advances and the immunophysiology of a new therapeutic chagas disease vaccine

INTRODUCTION

Chronic infection with the protozoal parasite Trypanosoma cruzi leads to a progressive cardiac disease, known as chronic Chagasic cardiomyopathy (CCC). A new therapeutic Chagas disease vaccine is in development to augment existing antiparasitic chemotherapy drugs.

AREAS COVERED

We report on our current understanding of the underlying immunologic and physiologic mechanisms that lead to CCC, including parasite immune escape mechanisms that allow persistence and the subsequent inflammatory and fibrotic processes that lead to clinical disease. We report on vaccine design and the observed immunotherapeutic effects including induction of a balanced T_H1/T_H2/T_H17 immune response that leads to reduced parasite burdens and tissue pathology. Further, we report vaccine-linked chemotherapy, a dose sparing strategy to further reduce parasite burdens and tissue pathology.

EXPERT OPINION

Our vaccine-linked chemotherapeutic approach is a multimodal treatment strategy, addressing both the parasite persistence and the underlying deleterious host inflammatory and fibrotic responses that lead to cardiac dysfunction. In targeting treatment towards patients with chronic indeterminate or early determinate Chagas disease, this vaccine-linked chemotherapeutic approach will be highly economical and will reduce the global disease burden and deaths due to CCC.

Molecular detection of Trypanosoma (Trypanosomatidae) in bats from Thailand, with their phylogenetic relationships

The vast majority of trypanosome species is vector-borne parasites, with some of them being medically and veterinary important (such as Trypanosoma cruzi and Trypanosoma brucei) and capable of causing serious illness in vertebrate hosts. The discovery of trypanosomes in bats emphasizes the importance of bats as an important reservoir. Interestingly, there is a hypothesis that bats are ancestral hosts of T. cruzi. Trypanosome diversity has never been investigated in bats in Thailand, despite being in a biodiversity hot spot. To gain a better understanding of the diversity and evolutionary relationship of trypanosomes, polymerase chain reaction-based surveys were carried out from 2018 to 2020 in 17 sites. A total of 576 bats were captured, representing 23 species. A total of 38 (6.6%) positive samples was detected in ten bat species. Trypanosoma dionisii and Trypanosoma noyesi were identified from Myotis siligorensis and Megaderma spasma, respectively. The remaining 18S rRNA sequences of trypanosomes were related to other trypanosomes previously reported elsewhere. The sequences in the current study showed nucleotide identity as low as 90.74% compared to those of trypanosomes in the GenBank database, indicating the possibility of new species. All bat trypanosomes identified in the current study fall within the T. cruzi clade. The current study adds to evidence linking T. noyesi to a bat trypanosome and further supports the bat host origin of the T. cruzi clade. To the best of authors' knowledge, this is the first study on bat trypanosomes in Thailand and their phylogenetic relationships with global isolates.

"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.

Highly Similar Sequence and Structure Yet Different Biophysical Behavior: A Computational Study of Two Triosephosphate Isomerases

Homodimeric triosephosphate isomerases (TIMs) from Trypanosoma cruzi (TcTIM) and Trypanosoma brucei (TbTIM) have markedly similar amino-acid sequences and three-dimensional structures. However, several of their biophysical parameters, such as their susceptibility to sulfhydryl agents and their reactivation speed after being denatured, have significant differences. The causes of these differences were explored with microsecond-scale molecular dynamics (MD) simulations of three different TIM proteins: TcTIM, TbTIM, and a chimeric protein, Mut1. We examined their electrostatic interactions and explored the impact of simulation length on them. The same salt bridge between catalytic residues Lys 14 and Glu 98 was observed in all three proteins, but key differences were found in other interactions that the catalytic amino acids form. In particular, a cation-π interaction between catalytic amino acids Lys 14 and His 96 and both a salt bridge and a hydrogen bond between catalytic Glu 168 and residue Arg 100 were only observed in TcTIM. Furthermore, although TcTIM forms less hydrogen bonds than TbTIM and Mut1, its hydrogen bond network spans almost the entire protein, connecting the residues in both monomers. This work provides new insight into the mechanisms that give rise to the different behavior of these proteins. The results also show the importance of long simulations.

Trypanosoma cruzi genetic diversity: impact on transmission cycles and Chagas disease

Trypanosoma cruzi, the agent of Chagas disease (ChD), exhibits remarkable biological and genetic diversity, along with eco-epidemiological complexity. In order to facilitate communication among researchers aiming at the characterisation of biological and epidemiological aspects of T. cruzi, parasite isolates and strains were partitioned into seven discrete typing units (DTUs), TcI-TcVI and TcBat, identifiable by reproducible genotyping protocols. Here we present the potential origin of the genetic diversity of T. cruzi and summarise knowledge about eco-epidemiological associations of DTUs with mammalian reservoirs and vectors. Circumstantial evidence of a connection between T. cruzi genotype and ChD manifestations is also discussed emphasising the role of the host’s immune response in clinical ChD progression. We describe genomic aspects of DTUs focusing on polymorphisms in multigene families encoding surface antigens that play essential functions for parasite survival both in the insect vector and the mammalian host. Such antigens most probably contributed to the parasite success in establishing infections in different hosts and exploring several niches. Gaps in the current knowledge and challenges for future research are pointed out.

Novel Cytoskeleton-Associated Proteins in Trypanosoma brucei Are Essential for Cell Morphogenesis and Cytokinesis

Trypanosome brucei, the causative agent of African sleeping sickness, harbours a highly ordered, subpellicular microtubule cytoskeleton that defines many aspects of morphology, motility and virulence. This array of microtubules is associated with a large number of proteins involved in its regulation. Employing proximity-dependent biotinylation assay (BioID) using the well characterised cytoskeleton-associated protein CAP5.5 as a probe, we identified CAP50 (Tb927.11.2610). This protein colocalises with the subpellicular cytoskeleton microtubules but not with the flagellum. Depletion by RNAi results in defects in cytokinesis, morphology and partial disorganisation of microtubule arrays. Published proteomics data indicate a possible association of CAP50 with two other, yet uncharacterised, cytoskeletal proteins, CAP52 (Tb927.6.5070) and CAP42 (Tb927.4.1300), which were therefore included in our analysis. We show that their depletion causes phenotypes similar to those described for CAP50 and that they are essential for cellular integrity.

Associations between Afrotropical bats, eukaryotic parasites, and microbial symbionts

Skin is the largest mammalian organ and the first defensive barrier against the external environment. The skin and fur of mammals can host a wide variety of ectoparasites, many of which are phylogenetically diverse, specialized, and specifically adapted to their hosts. Among hematophagous dipteran parasites, volatile organic compounds (VOCs) are known to serve as important attractants, leading parasites to compatible sources of blood meals. VOCs have been hypothesized to be mediated by host‐associated bacteria, which may thereby indirectly influence parasitism. Host‐associated bacteria may also influence parasitism directly, as has been observed in interactions between animal gut microbiota and malarial parasites. Hypotheses relating bacterial symbionts and eukaryotic parasitism have rarely been tested among humans and domestic animals, and to our knowledge have not been tested in wild vertebrates. In this study, we used Afrotropical bats, hematophagous ectoparasitic bat flies, and haemosporidian (malarial) parasites vectored by bat flies as a model to test the hypothesis that the vertebrate host microbiome is linked to parasitism in a wild system. We identified significant correlations between bacterial community composition of the skin and dipteran ectoparasite prevalence across four major bat lineages, as well as striking differences in skin microbial network characteristics between ectoparasitized and nonectoparasitized bats. We also identified links between the oral microbiome and presence of malarial parasites among miniopterid bats. Our results support the hypothesis that microbial symbionts may serve as indirect mediators of parasitism among eukaryotic hosts and parasites.

see also the Perspective by Kelly A. Speer

The neglected diversity: Description and molecular characterisation of Trypanosoma haploblephari Yeld and Smit, 2006 from endemic catsharks (Scyliorhinidae) in South Africa, the first trypanosome sequence data from sharks globally

With over 200 species of sharks reported from South African waters, the potential of discovering new blood parasites is very high. Unfortunately, this remains a poorly explored area of research, particularly in this biogeographical region. To date, only a single trypanosome species, Trypanosoma haploblephari Yeld and Smit, 2006, has been described from elasmobranchs off the coast of South Africa infecting the catsharks Haploblepharus pictus (Müller & Henle) and Haploblepharus edwardsii (Schinz). With only a single trypanosome species described and absence of molecular information, a study was conducted to provide further morphological and molecular information on T. haploblephari, a species considered not to demonstrate any pleomorphism. Thin blood smears were prepared, and blood was collected in molecular-grade ethanol from the caudal vein of two shark species, H. pictus and Poroderma pantherinum (Müller & Henle). Trypanosomes were morphologically described and molecularly characterised based on analysis of fragments of the 18S ribosomal gene. The presence of T. haploblephari in H. pictus was confirmed using the original description based on morphology, type host and locality, which allowed for the molecular characterisation of the species. In addition, this species was found parasitising P. pantherinum, its morphology considerably different in this host species as compared to that in the species of Haploblepharus, demonstrating that T. haploblephari may show extreme pleomorphism. This paper provides both morphological and molecular data for both morphotypes of T. haploblephari, with molecular comparisons to the only two other elasmobranch species of trypanosome for which sequence data is available. To elucidate the relationship of trypanosomes from aquatic hosts in general, more efforts need to be placed on elasmobranchs, as current phylogenetic studies are predominantly focused on trypanosomes infecting freshwater fishes.

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First molecular characterization of trypanosomes in endemic sharks in South Africa.

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Illustration of extreme morphological plasticity in trypanosomes.

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Phylogenetic analysis of marine and freshwater fish trypanosomes.

Molecular Identification of Trypanosoma evansi Isolated from Arabian Camels (Camelus dromedarius) in Riyadh and Al-Qassim, Saudi Arabia

We analyzed the blood from 400 one-humped camels, Camelus dromedarius (C. dromedarius), in Riyadh and Al-Qassim, Saudi Arabia to determine if they were infected with the parasite Trypanosoma spp. Polymerase chain reaction (PCR) targeting the internal transcribed spacer 1 (ITS1) gene was used to detect the prevalence of Trypanosoma spp. in the camels. Trypanosoma evansi (T. evansi) was detected in 79 of 200 camels in Riyadh, an infection rate of 39.5%, and in 92 of 200 camels in Al-Qassim, an infection rate of 46%. Sequence and phylogenetic analyses revealed that the isolated T. evansi was closely related to the T. evansi that was detected in C. dromedarius in Egypt and the T. evansi strain B15.1 18S ribosomal RNA gene identified from buffalo in Thailand. A BLAST search revealed that the sequences are also similar to those of T. evansi from beef cattle in Thailand and to T. brucei B8/18 18S ribosomal RNA from pigs in Nigeria.

Mitochondrial DNAs provide insight into trypanosome phylogeny and molecular evolution

Background

Trypanosomes are single-celled eukaryotic parasites characterised by the unique biology of their mitochondrial DNA. African livestock trypanosomes impose a major burden on agriculture across sub-Saharan Africa, but are poorly understood compared to those that cause sleeping sickness and Chagas disease in humans. Here we explore the potential of the maxicircle, a component of trypanosome mitochondrial DNA to study the evolutionary history of trypanosomes.

Results

We used long-read sequencing to completely assemble maxicircle mitochondrial DNA from four previously uncharacterized African trypanosomes, and leveraged these assemblies to scaffold and assemble a further 103 trypanosome maxicircle gene coding regions from published short-read data. While synteny was largely conserved, there were repeated, independent losses of Complex I genes. Comparison of pre-edited and non-edited genes revealed the impact of RNA editing on nucleotide composition, with non-edited genes approaching the limits of GC loss. African tsetse-transmitted trypanosomes showed high levels of RNA editing compared to other trypanosomes. The gene coding regions of maxicircle mitochondrial DNAs were used to construct time-resolved phylogenetic trees, revealing deep divergence events among isolates of the pathogens Trypanosoma brucei and T. congolense.

Conclusions

Our data represents a new resource for experimental and evolutionary analyses of trypanosome phylogeny, molecular evolution and function. Molecular clock analyses yielded a timescale for trypanosome evolution congruent with major biogeographical events in Africa and revealed the recent emergence of Trypanosoma brucei gambiense and T. equiperdum, major human and animal pathogens.

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.

A review of the systematics, species identification and diagnostics of the Trypanosomatidae using the maxicircle kinetoplast DNA: from past to present

The Trypanosomatid family are a diverse and widespread group of protozoan parasites that belong to the higher order class Kinetoplastida. Containing predominantly monoxenous species (i.e. those having only a single host) that are confined to invertebrate hosts, this class is primarily known for its pathogenic dixenous species (i.e. those that have two hosts), serving as the aetiological agents of the important neglected tropical diseases including leishmaniasis, American trypanosomiasis (Chagas disease) and human African trypanosomiasis. Over the past few decades, a multitude of studies have investigated the diversity, classification and evolutionary history of the trypanosomatid family using different approaches and molecular targets. The mitochondrial-like DNA of the trypanosomatid parasites, also known as the kinetoplast, has emerged as a unique taxonomic and diagnostic target for exploring the evolution of this diverse group of parasitic eukaryotes. This review discusses recent advancements and important developments that have made a significant impact in the field of trypanosomatid systematics and diagnostics in recent years.

Trypanosoma brucei and Trypanosoma cruzi DNA Mismatch Repair Proteins Act Differently in the Response to DNA Damage Caused by Oxidative Stress

MSH2, associated with MSH3 or MSH6, is a central component of the eukaryotic DNA Mismatch Repair (MMR) pathway responsible for the recognition and correction of base mismatches that occur during DNA replication and recombination. Previous studies have shown that MSH2 plays an additional DNA repair role in response to oxidative damage in Trypanosoma cruzi and Trypanosoma brucei. By performing co-immunoprecipitation followed by mass spectrometry with parasites expressing tagged proteins, we confirmed that the parasites' MSH2 forms complexes with MSH3 and MSH6. To investigate the involvement of these two other MMR components in the oxidative stress response, we generated knockout mutants of MSH6 and MSH3 in T. brucei bloodstream forms and MSH6 mutants in T. cruzi epimastigotes. Differently from the phenotype observed with T. cruzi MSH2 knockout epimastigotes, loss of one or two alleles of T. cruzi msh6 resulted in increased susceptibility to H₂O₂ exposure, besides impaired MMR. In contrast, T. brucei msh6 or msh3 null mutants displayed increased tolerance to MNNG treatment, indicating that MMR is affected, but no difference in the response to H₂O₂ treatment when compared to wild type cells. Taken together, our results suggest that, while T. cruzi MSH6 and MSH2 are involved with the oxidative stress response in addition to their role as components of the MMR, the DNA repair pathway that deals with oxidative stress damage operates differently in T. brucei.

An Evolutionary View of Trypanosoma Cruzi Telomeres

Like in most eukaryotes, the linear chromosomes of Trypanosoma cruzi end in a nucleoprotein structure called the telomere, which is preceded by regions of variable length called subtelomeres. Together telomeres and subtelomeres are dynamic sites where DNA sequence rearrangements can occur without compromising essential interstitial genes or chromosomal synteny. Good examples of subtelomeres involvement are the expansion of human olfactory receptors genes, variant surface antigens in Trypanosoma brucei, and Saccharomyces cerevisiae mating types. T. cruzi telomeres are made of long stretches of the hexameric repeat 5′-TTAGGG-OH-3′, and its subtelomeres are enriched in genes and pseudogenes from the large gene families RHS, TS and DGF1, DEAD/H-RNA helicase and N-acetyltransferase, intermingled with sequences of retrotransposons elements. In particular, members of the Trans-sialidase type II family appear to have played a role in shaping the current T. cruzi telomere structure. Although the structure and function of T. cruzi telomeric and subtelomeric regions have been documented, recent experiments are providing new insights into T. cruzi's telomere-subtelomere dynamics. In this review, I discuss the co-evolution of telomere, subtelomeres and the TS gene family, and the role that these regions may have played in shaping T. cruzi's genome.

On the Function of Trans-Splicing: No Evidence for Widespread Proteome Diversification in Trypanosomes

A long-standing mystery of genomic/transcriptomic structure involves spliced leader trans-splicing (SLTS), in which short RNA “tags” transcribed from a distinct genomic locus is added near the 5′ end of RNA transcripts by the spliceosome. SLTS has been observed in diverse eukaryotes in a phylogenetic pattern implying recurrent independent evolution. This striking convergence suggests important functions for SLTS, however no general novel function is known. Recent findings of frequent alternative SLTS (ALT-TS) suggest that ALT-TS could impart widespread functionality. Here, we tested the hypothesis that ALT-TS diversifies proteomes by comparing splicing patterns in orthologous genes between two deeply diverged trypanosome parasites. We also tested proteome diversification functions of ALT-TS by utilizing ribosome profiling sequence data. Finally, we investigated ALT-TS as a mechanism to regulate the expression of unproductive transcripts. Although our results indicate the functional importance of some cases of trans-splicing, we find no evidence for the hypothesis that proteome diversification is a general function of trans-splicing.

Evolutionary Insight into the Trypanosomatidae Using Alignment-Free Phylogenomics of the Kinetoplast

Advancements in next-generation sequencing techniques have led to a substantial increase in the genomic information available for analyses in evolutionary biology. As such, this data requires the exponential growth in bioinformatic methods and expertise required to understand such vast quantities of genomic data. Alignment-free phylogenomics offer an alternative approach for large-scale analyses that may have the potential to address these challenges. The evolutionary relationships between various species within the trypanosomatid family, specifically members belonging to the genera Leishmania and Trypanosoma have been extensively studies over the last 30 years. However, there is a need for a more exhaustive analysis of the Trypanosomatidae, summarising the evolutionary patterns amongst the entire family of these important protists. The mitochondrial DNA of the trypanosomatids, better known as the kinetoplast, represents a valuable taxonomic marker given its unique presence across all kinetoplastid protozoans. The aim of this study was to validate the reliability and robustness of alignment-free approaches for phylogenomic analyses and its applicability to reconstruct the evolutionary relationships between the trypanosomatid family. In the present study, alignment-free analyses demonstrated the strength of these methods, particularly when dealing with large datasets compared to the traditional phylogenetic approaches. We present a maxicircle genome phylogeny of 46 species spanning the trypanosomatid family, demonstrating the superiority of the maxicircle for the analysis and taxonomic resolution of the Trypanosomatidae.

Phylogenetic Studies

Phylogenetics is an important component of the systems biology approach. Knowledge about evolution of the genus Leishmania is essential to understand various aspects of basic biology of these parasites, such as parasite-host or parasite-vector relationships, biogeography, or epidemiology. Here, we present a comprehensive guideline for performing phylogenetic studies based on DNA sequence data, but with principles that can be adapted to protein sequences or other molecular markers. It is presented as a compilation of the most commonly used genetic targets for phylogenetic studies of Leishmania, including their respective primers for amplification and references, as well as details of PCR assays. Guidelines are, then, presented to choose the best targets in relation to the types of samples under study. Finally, and importantly, instructions are given to obtain optimal sequences, alignments, and datasets for the subsequent data analysis and phylogenetic inference. Different bioinformatics methods and software for phylogenetic inference are presented and explained. This chapter aims to provide a compilation of methods and generic guidelines to conduct phylogenetics of Leishmania for nonspecialists.

Haematological alterations in non-human hosts infected with Trypanosoma cruzi: a systematic review

American trypanosomiasis is a neglected tropical disease whose spectrum has not been quite understood, including the impact of Trypanosoma cruzi infection on the haematological parameters of different vertebrate hosts. Thus, this study was designed to compare the pattern of haematological changes induced by T. cruzi infection in order to identify possible species-specific differences among taxons. We also aimed at evaluating the use of this parameter as a tool for diagnosis during the acute phase, when symptoms are usually masked. For this purpose, we performed a systematic search on PubMed and Scopus databases to retrieve original studies published until August 2016. Thirty-one studies were selected using Prisma strategy, which were then submitted to data extraction and methodological bias analysis. Half of the studies showed that the number of erythrogram decreased in infected animals, indicating anaemia. In 68.2% of the studies, the total amount of leukogram values increased, suggesting infection. The main methodological limitations were insufficient information for T. cruzi strains identification, inoculation routes and parasitological characterization. Most of the mammalian species analysed showed the same pattern of haematological changes following T. cruzi infection, indicating that haematological parameters might direct the diagnosis of Chagas disease in the initial phase.

Diversity and evolution of anuran trypanosomes: insights from the study of European species

Background

Amphibian trypanosomes were the first ever described trypanosomatids. Nevertheless, their taxonomy remains entangled because of pleomorphism and high prevalence of mixed infections. Despite the fact that the first species in this group were described in Europe, virtually none of the trypanosomes from European anurans was analyzed using modern molecular methods.

Methods

In this study, we explored the diversity and phylogeny of trypanosomes in true frogs from Europe using light microscopy and molecular methods.

Results

A comparison of observed morphotypes with previous descriptions allowed us to reliably identify three Trypanosoma spp., whereas the remaining two strains were considered to represent novel taxa. In all cases, more than one morphotype per blood sample was observed, indicating mixed infections. One hundred and thirty obtained 18S rRNA gene sequences were unambiguously subdivided into five groups, correspondent to the previously recognized or novel taxa of anuran trypanosomes.

Conclusions

In this work we studied European frog trypanosomes. Even with a relatively moderate number of isolates, we were able to find not only three well-known species, but also two apparently new ones. We revealed that previous assignments of multiple isolates from distant geographical localities to one species based on superficial resemblance were unjustified. Our work also demonstrated a high prevalence of mixed trypanosome infections in frogs and proposed a plausible scenario of evolution of the genus Trypanosoma.

Shape-shifting trypanosomes: Flagellar shortening followed by asymmetric division in Trypanosoma congolense from the tsetse proventriculus

Trypanosomatids such as Leishmania and Trypanosoma are digenetic, single-celled, parasitic flagellates that undergo complex life cycles involving morphological and metabolic changes to fit them for survival in different environments within their mammalian and insect hosts. According to current consensus, asymmetric division enables trypanosomatids to achieve the major morphological rearrangements associated with transition between developmental stages. Contrary to this view, here we show that the African trypanosome Trypanosoma congolense, an important livestock pathogen, undergoes extensive cell remodelling, involving shortening of the cell body and flagellum, during its transition from free-swimming proventricular forms to attached epimastigotes in vitro. Shortening of the flagellum was associated with accumulation of PFR1, a major constituent of the paraflagellar rod, in the mid-region of the flagellum where it was attached to the substrate. However, the PFR1 depot was not essential for attachment, as it accumulated several hours after initial attachment of proventricular trypanosomes. Detergent and CaCl₂ treatment failed to dislodge attached parasites, demonstrating the robust nature of flagellar attachment to the substrate; the PFR1 depot was also unaffected by these treatments. Division of the remodelled proventricular trypanosome was asymmetric, producing a small daughter cell. Each mother cell went on to produce at least one more daughter cell, while the daughter trypanosomes also proliferated, eventually resulting in a dense culture of epimastigotes. Here, by observing the synchronous development of the homogeneous population of trypanosomes in the tsetse proventriculus, we have been able to examine the transition from proventricular forms to attached epimastigotes in detail in T. congolense. This transition is difficult to observe in vivo as it happens inside the mouthparts of the tsetse fly. In T. brucei, this transition is achieved by asymmetric division of long trypomastigotes in the proventriculus, yielding short epimastigotes, which go on to colonise the salivary glands. Thus, despite their close evolutionary relationship and shared developmental route within the vector, T. brucei and T. congolense have evolved different ways of accomplishing the same developmental transition from proventricular form to attached epimastigote.

Tsetse-transmitted trypanosomes are parasitic protists that cause severe human and livestock diseases in tropical Africa. During their developmental cycle in the tsetse fly, these trypanosomes undergo complex cycles of differentiation and proliferation. Here we have investigated part of the developmental cycle of the major livestock pathogen Trypanosoma congolense as it moves from the fly midgut via the foregut to the mouthparts, where it reacquires infectivity to mammalian hosts. This transition is difficult to observe in vivo because of the small numbers of migratory trypanosomes and their inaccessibility in the fly. However, prior to migration, trypanosomes accumulate in the proventriculus, the valve that separates the foregut from the midgut, and we were able to observe the behaviour of these cells in vitro. On release from the proventriculus, these trypanosomes readily attach to a glass microscope slide and then undergo drastic remodelling to become short, stout cells, before each produces a small daughter cell. Each mother cell goes on to produce at least one further daughter trypanosome in the same way, while the daughter cells also proliferate as attached cells. We assume that these events would normally happen in vivo inside the tsetse proboscis. In T. brucei the equivalent developmental transition takes place in the proventriculus or foregut in free-swimming rather than attached cells, and is achieved via an asymmetric division. Thus, despite their close evolutionary relationship, these two trypanosome species have evolved different ways of accomplishing what is essentially the same developmental transition.

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.

Identification of the critical residues responsible for differential reactivation of the triosephosphate isomerases of two trypanosomes

The reactivation of triosephosphate isomerase (TIM) from unfolded monomers induced by guanidine hydrochloride involves different amino acids of its sequence in different stages of protein refolding. We describe a systematic mutagenesis method to find critical residues for certain physico-chemical properties of a protein. The two similar TIMs of Trypanosoma brucei and Trypanosoma cruzi have different reactivation velocities and efficiencies. We used a small number of chimeric enzymes, additive mutants and planned site-directed mutants to produce an enzyme from T. brucei with 13 mutations in its sequence, which reactivates fast and efficiently like wild-type (WT) TIM from T. cruzi, and another enzyme from T. cruzi, with 13 slightly altered mutations, which reactivated slowly and inefficiently like the WT TIM of T. brucei. Our method is a shorter alternative to random mutagenesis, saturation mutagenesis or directed evolution to find multiple amino acids critical for certain properties of proteins.

High Trypanosoma spp. diversity is maintained by bats and triatomines in Espírito Santo state, Brazil

The aim of this study was to reevaluate the ecology of an area in the Atlantic Forest, southeast Brazil, where Chagas disease (CD) has been found to occur. In a previous study, immediately after the occurrence of a CD case, we did not observe any sylvatic small mammals or dogs with Trypanosoma cruzi cruzi infections, but Triatoma vitticeps presented high T. c. cruzi infection rates. In this study, we investigated bats together with non-volant mammals, dogs, and triatomines to explore other possible T. c. cruzi reservoirs/hosts in the area. Seventy-three non-volant mammals and 186 bats were captured at three sites within the Guarapari municipality, Espírito Santo state. Rio da Prata and Amarelos sites exhibited greater richness in terms of non-volant mammals and bats species, respectively. The marsupial Metachirus nudicaudatus, the rodent Trinomys paratus, and the bats Artibeus lituratus and Carollia perspicillata were the most frequently captured species. As determined by positive hemocultures, only two non-volant mammals were found to be infected by Trypanosoma species: Monodelphis americana, which was infected by T. cascavelli, T. dionisii and Trypanosoma sp., and Callithrix geoffroyi, which was infected by T. minasense. Bats presented T. c. cruzi TcI and TcIII/V, T. c. marinkellei, T. dionisii, T. rangeli B and D, and Trypanosoma sp. infections. Seven dogs were infected with T. cruzi based only on serological exams. The triatomines T. vitticeps and Panstrongylus geniculatus were found to be infected by trypanosomes via microscopy. According to molecular characterization, T. vitticeps specimens were infected with T. c. cruzi TcI, TcII, TcIII/V, and TcIV, T. c. marinkellei and T. dionisii. We observed high trypanosome diversity in a small and fragmented region of the Atlantic Forest. This diversity was primarily maintained by bats and T. vitticeps. Our findings show that the host specificity of the Trypanosoma genus should be thoroughly reviewed. In addition, our data show that CD cases can occur without an enzootic cycle near residential areas.

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.

The diversity of the Chagas parasite, Trypanosoma cruzi, infecting the main Central American vector, Triatoma dimidiata, from Mexico to Colombia

Little is known about the strains of Trypanosoma cruzi circulating in Central America and specifically in the most important vector in this region, Triatoma dimidiata. Approximately six million people are infected with T. cruzi, the causative agent of Chagas disease, which has the greatest negative economic impact and is responsible for ~12,000 deaths annually in Latin America. By international consensus, strains of T. cruzi are divided into six monophyletic clades called discrete typing units (DTUs TcI-VI) and a seventh DTU first identified in bats called TcBat. TcI shows the greatest geographic range and diversity. Identifying strains present and diversity within these strains is important as different strains and their genotypes may cause different pathologies and may circulate in different localities and transmission cycles, thus impacting control efforts, treatment and vaccine development. To determine parasite strains present in T. dimidiata across its geographic range from Mexico to Colombia, we isolated abdominal DNA from T. dimidiata and determined which specimens were infected with T. cruzi by PCR. Strains from infected insects were determined by comparing the sequence of the 18S rDNA and the spliced-leader intergenic region to typed strains in GenBank. Two DTUs were found: 94% of infected T. dimidiata contained TcI and 6% contained TcIV. TcI exhibited high genetic diversity. Geographic structure of TcI haplotypes was evident by Principal Component and Median-Joining Network analyses as well as a significant result in the Mantel test, indicating isolation by distance. There was little evidence of association with TcI haplotypes and host/vector or ecotope. This study provides new information about the strains circulating in the most important Chagas vector in Central America and reveals considerable variability within TcI as well as geographic structuring at this large geographic scale. The lack of association with particular vectors/hosts or ecotopes suggests the parasites are moving among vectors/hosts and ecotopes therefore a comprehensive approach, such as the Ecohealth approach that makes houses refractory to the vectors will be needed to successfully halt transmission of Chagas disease.

The evolution of trypanosomatid taxonomy

Trypanosomatids are protozoan parasites of the class Kinetoplastida predominately restricted to invertebrate hosts (i.e. possess a monoxenous life-cycle). However, several genera are pathogenic to humans, animals and plants, and have an invertebrate vector that facilitates their transmission (i.e. possess a dixenous life-cycle). Phytomonas is one dixenous genus that includes several plant pathogens transmitted by phytophagous insects. Trypanosoma and Leishmania are dixenous genera that infect vertebrates, including humans, and are transmitted by hematophagous invertebrates. Traditionally, monoxenous trypanosomatids such as Leptomonas were distinguished from morphologically similar dixenous species based on their restriction to an invertebrate host. Nonetheless, this criterion is somewhat flawed as exemplified by Leptomonas seymouri which reportedly infects vertebrates opportunistically. Similarly, Novymonas and Zelonia are presumably monoxenous genera yet sit comfortably in the dixenous clade occupied by Leishmania. The isolation of Leishmania macropodum from a biting midge (Forcipomyia spp.) rather than a phlebotomine sand fly calls into question the exclusivity of the Leishmania-sand fly relationship, and its suitability for defining the Leishmania genus. It is now accepted that classic genus-defining characteristics based on parasite morphology and host range are insufficient to form the sole basis of trypanosomatid taxonomy as this has led to several instances of paraphyly. While improvements have been made, resolution of evolutionary relationships within the Trypanosomatidae is confounded by our incomplete knowledge of its true diversity. The known trypanosomatids probably represent a fraction of those that exist and isolation of new species will help resolve relationships in this group with greater accuracy. This review incites a dialogue on how our understanding of the relationships between certain trypanosomatids has shifted, and discusses new knowledge that informs the present taxonomy of these important parasites.

Co-infection of Trypanosoma pestanai and Anaplasma phagocytophilum in a dog from Germany

Infections with arthropod-borne pathogens are an increasing threat world-wide that requires heightened vigilance from veterinary and medical practitioners, especially when they involve new or unusual organisms. A dog was presented to a local veterinary clinic in Germany with malaise, pale mucous membranes and stiff joints. Clinical assessment revealed pyrexia, leukopenia and thrombocytopenia. On suspicion of a tick-borne infection, blood samples were examined for clinical and biochemical parameters and subjected to a Anaplasma phagocytophilum-, Borrelia spp.- and Ehrlichia canis-specific real-time PCR. Additionally, a sample of the pre-therapeutic buffy coat was co-cultured with the Ixodes scapularis cell-line ISE6 for 20days. Only the PCR specific for A. phagocytophilum DNA yielded a positive result, and furthermore, Anaplasma morulae were visible in granulocytes and tick cells. After co-culturing, extracellular trypomastigote and epimastigote stages of Trypanosoma sp. with an average length of 29.7μm were observed, featuring a pointed posterior end. Sequence analysis of a 2080bp fragment of the 18S rRNA gene showed 99% identity to the 18S rRNA gene of Trypanosoma pestanai, previously described from a European badger (Meles meles) in France. The dog's condition improved rapidly in response to doxycycline treatment for three weeks. The clinical status normalized and clinical blood parameters were found to be within the reference ranges. To our knowledge this is the first description of T. pestanai infection in a dog, the first detection of T. pestanai in Germany and the first documented co-infection with these two pathogens. Co-infections with unusual opportunistic vector-borne pathogens should be considered, if acute canine granulocytic anaplasmosis is evident.

Blood transcriptomes reveal novel parasitic zoonoses circulating in Madagascar's lemurs

Zoonotic diseases are a looming threat to global populations, and nearly 75% of emerging infectious diseases can spread among wildlife, domestic animals and humans. A 'One World, One Health' perspective offers us an ideal framework for understanding and potentially mitigating the spread of zoonoses, and the island of Madagascar serves as a natural laboratory for conducting these studies. Rapid habitat degradation and climate change on the island are contributing to more frequent contact among humans, livestock and wildlife, increasing the potential for pathogen spillover events. Given Madagascar's long geographical isolation, coupled with recent and repeated introduction of agricultural and invasive species, it is likely that a number of circulating pathogens remain uncharacterized in lemur populations. Thus, it is imperative that new approaches be implemented for de novo pathogen discovery. To this end, we used non-targeted deep sequencing of blood transcriptomes from two species of critically endangered wild lemurs (Indri indri and Propithecus diadema) to characterize blood-borne pathogens. Our results show several undescribed vector-borne parasites circulating within lemurs, some of which may cause disease in wildlife, livestock and humans. We anticipate that advanced methods for de novo identification of unknown pathogens will have broad utility for characterizing other complex disease transmission systems.

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.

Insights from paleomicrobiology into the indigenous peoples of pre-colonial America - a review

This review investigates ancient infectious diseases in the Americas dated to the pre-colonial period and considers what these findings can tell us about the history of the indigenous peoples of the Americas. It gives an overview, but focuses on four microbial pathogens from this period: Helicobacter pylori, Mycobacterium tuberculosis, Trypanosoma cruzi and Coccidioides immitis, which cause stomach ulceration and gastric cancer, tuberculosis, Chagas disease and valley fever, respectively. These pathogens were selected as H. pylori can give insight into ancient human migrations into the Americas, M. tuberculosis is associated with population density and urban development, T. cruzi can elucidate human living conditions and C. immitis can indicate agricultural development. A range of methods are used to diagnose infectious disease in ancient human remains, with DNA analysis by polymerase chain reaction one of the most reliable, provided strict precautions are taken against cross contamination. The review concludes with a brief summary of the changes that took place after European exploration and colonisation.

Evolutionary diversification of the trypanosome haptoglobin-haemoglobin receptor from an ancestral haemoglobin receptor

The haptoglobin-haemoglobin receptor of the African trypanosome species, Trypanosoma brucei, is expressed when the parasite is in the bloodstream of the mammalian host, allowing it to acquire haem through the uptake of haptoglobin-haemoglobin complexes. Here we show that in Trypanosoma congolense this receptor is instead expressed in the epimastigote developmental stage that occurs in the tsetse fly, where it acts as a haemoglobin receptor. We also present the structure of the T. congolense receptor in complex with haemoglobin. This allows us to propose an evolutionary history for this receptor, charting the structural and cellular changes that took place as it adapted from a role in the insect to a new role in the mammalian host.

DOI:http://dx.doi.org/10.7554/eLife.13044.001

Trypanosomes are single-celled parasites that infect a range of animal hosts. These parasites need a molecule called haem to grow properly and are mostly spread by insects that feed on the blood of mammals. Most haem in mammals is found in red blood cells and is bound to a protein called haemoglobin. When it is released from these cells, haemoglobin forms a complex with another protein called haptoglobin as well.

The best-studied trypanosomes from Africa have a receptor protein on their surface that recognizes the haptoglobin-haemoglobin complex and allows the parasites to obtain haem from their hosts. An African trypanosome called T. brucei causes sleeping sickness in humans, and has a receptor that can only recognize haemoglobin when it is in complex with haptoglobin. However, few trypanosome receptors have been studied to date, and so it was not clear if they all work in the same way.

Trypanosoma congolense is a trypanosome that has a big impact on livestock farmers in sub-Saharan Africa and infects cattle, pigs and goats. Lane-Serff, MacGregor et al. now report that the receptor protein from T. congolense can bind to haemoglobin on its own. A technique called X-ray crystallography was used to reveal the three-dimensional structure of the T. congolense receptor and haemoglobin in fine detail. Further experiments then confirmed that the receptor actually binds more strongly to haemoglobin than it does to the haptoglobin-haemoglobin complex.

Experiments with living parasites showed that T. congolense produces its receptor when it is in the mouthparts of its insect host, the tsetse fly. This is unlike what occurs in T. brucei, which only produces its receptor while it is in the bloodstream of its mammalian host. Lane-Serff, MacGregor et al. suggest that T. congolense’s receptor is more like the receptor found in ancestor of the trypanosomes. This means that, at least once during the evolution of these parasites, this receptor evolved from being a haemoglobin receptor produced in the tsetse fly to a haptoglobin-haemoglobin receptor produced in an infected mammal.

The next step is to investigate the details of the role played by the T. congolense receptor when the parasite is in the tsetse fly. It will also be important to understand how this parasite is still able to grow in the mammalian host’s bloodstream even though it does not produce much of the receptor during this stage.

DOI:http://dx.doi.org/10.7554/eLife.13044.002

Evasion of the Immune Response by Trypanosoma cruzi during Acute Infection

Trypanosoma cruzi is the etiologic agent of Chagas disease, a neglected tropical disease that affects millions of people mainly in Latin America. To establish a life-long infection, T. cruzi must subvert the vertebrate host's immune system, using strategies that can be traced to the parasite's life cycle. Once inside the vertebrate host, metacyclic trypomastigotes rapidly invade a wide variety of nucleated host cells in a membrane-bound compartment known as the parasitophorous vacuole, which fuses to lysosomes, originating the phagolysosome. In this compartment, the parasite relies on a complex network of antioxidant enzymes to shield itself from lysosomal oxygen and nitrogen reactive species. Lysosomal acidification of the parasitophorous vacuole is an important factor that allows trypomastigote escape from the extremely oxidative environment of the phagolysosome to the cytoplasm, where it differentiates into amastigote forms. In the cytosol of infected macrophages, oxidative stress instead of being detrimental to the parasite, favors amastigote burden, which then differentiates into bloodstream trypomastigotes. Trypomastigotes released in the bloodstream upon the rupture of the host cell membrane express surface molecules, such as calreticulin and GP160 proteins, which disrupt initial and key components of the complement pathway, while others such as glycosylphosphatidylinositol-mucins stimulate immunoregulatory receptors, delaying the progression of a protective immune response. After an immunologically silent entry at the early phase of infection, T. cruzi elicits polyclonal B cell activation, hypergammaglobulinemia, and unspecific anti-T. cruzi antibodies, which are inefficient in controlling the infection. Additionally, the coexpression of several related, but not identical, epitopes derived from trypomastigote surface proteins delays the generation of T. cruzi-specific neutralizing antibodies. Later in the infection, the establishment of an anti-T. cruzi CD8(+) immune response focused on the parasite's immunodominant epitopes controls parasitemia and tissue infection, but fails to completely eliminate the parasite. This outcome is not detrimental to the parasite, as it reduces host mortality and maintains the parasite infectivity toward the insect vectors.

Phylogenomic reconstruction supports supercontinent origins for Leishmania

Leishmania, a genus of parasites transmitted to human hosts and mammalian/reptilian reservoirs by an insect vector, is the causative agent of the human disease complex leishmaniasis. The evolutionary relationships within the genus Leishmania and its origins are the source of ongoing debate, reflected in conflicting phylogenetic and biogeographic reconstructions. This study employs a recently described bioinformatics method, SISRS, to identify over 200,000 informative sites across the genome from newly sequenced and publicly available Leishmania data. This dataset is used to reconstruct the evolutionary relationships of this genus. Additionally, we constructed a large multi-gene dataset, using it to reconstruct the phylogeny and estimate divergence dates for species. We conclude that the genus Leishmania evolved at least 90-100 million years ago, supporting a modified version of the Multiple Origins hypothesis that we call the Supercontinent hypothesis. According to this scenario, separate Leishmania clades emerged prior to, and during, the breakup of Gondwana. Additionally, we confirm that reptile-infecting Leishmania are derived from mammalian forms and that the species that infect porcupines and sloths form a clade long separated from other species. Finally, we firmly place the guinea-pig infecting species, Leishmaniaenriettii, the globally dispersed Leishmaniasiamensis, and the newly identified Australian species from a kangaroo, as sibling species whose distribution arises from the ancient connection between Australia, Antarctica, and South America.

The diversity and expansion of the trans-sialidase gene family is a common feature in Trypanosoma cruzi clade members

Trans-sialidase (TS) is a polymorphic protein superfamily described in members of the protozoan genus Trypanosoma. Of the eight TS groups recently described, TS group I proteins (some of which have catalytic activity) are present in the distantly related Trypanosoma brucei and Trypanosoma cruzi phylogenetic clades, whereas other TS groups have only been described in some species belonging to the T. cruzi clade. In the present study we analyzed the repertoire, distribution and phylogenetic relationships of TS genes among species of the T. cruzi clade based on sequence similarity, multiple sequence alignment and tree-reconstruction approaches using TS sequences obtained with the aid of PCR-based strategies or retrieved from genome databases. We included the following representative isolates of the T. cruzi clade from South America: T. cruzi, T. cruzi Tcbat, Trypanosoma cruzi marinkellei, Trypanosoma dionisii, Trypanosoma rangeli and Trypanosoma conorhini. The cloned sequences encoded conserved TS protein motifs Asp-box and VTVxNVxLYNR but lacked the FRIP motif (conserved in TS group I). The T. conorhini sequences were the most divergent. The hybridization patterns of TS probes with chromosomal bands confirmed the abundance of these sequences in species in the T. cruzi clade. Divergence and relationship analysis placed most of the TS sequences in the groups defined in T. cruzi. Further examination of members of TS group II, which includes T. cruzi surface glycoproteins implicated in host cell attachment and invasion, showed that sequences of T. cruzi Tcbat grouped with those of T. cruzi genotype TcI. Our analysis indicates that different members of the T. cruzi clade, with different vertebrate hosts, vectors and pathogenicity, share the extensive expansion and sequence diversification of the TS gene family. Altogether, our results are congruent with the evolutionary history of the T. cruzi clade and represent a contribution to the understanding of the molecular evolution and role of TS proteins in trypanosomes.

Trypanosomes Modify the Behavior of Their Insect Hosts: Effects on Locomotion and on the Expression of a Related Gene

Background

As a result of evolution, the biology of triatomines must have been significantly adapted to accommodate trypanosome infection in a complex network of vector-vertebrate-parasite interactions. Arthropod-borne parasites have probably developed mechanisms, largely still unknown, to exploit the vector-vertebrate host interactions to ensure their transmission to suitable hosts. Triatomines exhibit a strong negative phototaxis and nocturnal activity, believed to be important for insect survival against its predators.

Methodology/Principal Findings

In this study we quantified phototaxis and locomotion in starved fifth instar nymphs of Rhodnius prolixus infected with Trypanosoma cruzi or Trypanosoma rangeli. T. cruzi infection did not alter insect phototaxis, but induced an overall 20% decrease in the number of bug locomotory events. Furthermore, the significant differences induced by this parasite were concentrated at the beginning of the scotophase. Conversely, T. rangeli modified both behaviors, as it significantly decreased bug negative phototaxis, while it induced a 23% increase in the number of locomotory events in infected bugs. In this case, the significant effects were observed during the photophase. We also investigated the expression of Rpfor, the triatomine ortholog of the foraging gene known to modulate locomotion in other insects, and found a 4.8 fold increase for T. rangeli infected insects.

Conclusions/Significance

We demonstrated for the first time that trypanosome infection modulates the locomotory activity of the invertebrate host. T. rangeli infection seems to be more broadly effective, as besides affecting the intensity of locomotion this parasite also diminished negative phototaxis and the expression of a behavior-associated gene in the triatomine vector.

The control of Chagas disease, an infection that affects ca. 8 million people in Latin America, is mostly based on vector control activities. Understanding vector biology and how these insects interact with their environment, hosts and pathogens is crucial to improve vector control strategies. The behavior of triatomines has been largely studied, yet few reports have focused on the behavioral effects of the interaction that these insects endure with their natural parasites. Trypanosoma cruzi and Trypanosoma rangeli are two protozoan parasites found naturally infecting Rhodnius species. In this study, we showed for the first time that the locomotory activity of Rhodnius prolixus, a relevant vector of Chagas disease, is affected by trypanosome infection. T. cruzi was found to decrease bug locomotory activity during night hours, while T. rangeli promoted a generally increased insect locomotion. In addition, we searched for the R. prolixus orthologue (Rpfor) of a gene associated with the modulation of insect activity (foraging gene) and found that Rpfor expression was also affected by trypanosome infection.

Ecological host fitting of Trypanosoma cruzi TcI in Bolivia: mosaic population structure, hybridization and a role for humans in Andean parasite dispersal

An improved understanding of how a parasite species exploits its genetic repertoire to colonize novel hosts and environmental niches is crucial to establish the epidemiological risk associated with emergent pathogenic genotypes. Trypanosoma cruzi, a genetically heterogeneous, multi-host zoonosis, provides an ideal system to examine the sylvatic diversification of parasitic protozoa. In Bolivia, T. cruzi I, the oldest and most widespread genetic lineage, is pervasive across a range of ecological clines. High-resolution nuclear (26 loci) and mitochondrial (10 loci) genotyping of 199 contemporaneous sylvatic TcI clones was undertaken to provide insights into the biogeographical basis of T. cruzi evolution. Three distinct sylvatic parasite transmission cycles were identified: one highland population among terrestrial rodent and triatomine species, composed of genetically homogenous strains (Ar = 2.95; PA/L = 0.61; DAS = 0.151), and two highly diverse, parasite assemblages circulating among predominantly arboreal mammals and vectors in the lowlands (Ar = 3.40 and 3.93; PA/L = 1.12 and 0.60; DAS = 0.425 and 0.311, respectively). Very limited gene flow between neighbouring terrestrial highland and arboreal lowland areas (distance ~220 km; FST = 0.42 and 0.35) but strong connectivity between ecologically similar but geographically disparate terrestrial highland ecotopes (distance >465 km; FST = 0.016-0.084) strongly supports ecological host fitting as the predominant mechanism of parasite diversification. Dissimilar heterozygosity estimates (excess in highlands, deficit in lowlands) and mitochondrial introgression among lowland strains may indicate fundamental differences in mating strategies between populations. Finally, accelerated parasite dissemination between densely populated, highland areas, compared to uninhabited lowland foci, likely reflects passive, long-range anthroponotic dispersal. The impact of humans on the risk of epizootic Chagas disease transmission in Bolivia is discussed.

The flagellar adenylate kinases of Trypanosoma cruzi

Adenylate kinases (ADK) are key enzymes involved in cell energy management. Trypanosomatids present the highest number of variants in a single cell in comparison with the rest of the living organisms. In this work, we characterized two flagellar ADKs from Trypanosoma cruzi, called TcADK1 and TcADK4, which are also located in the cell cytosol. Interestingly, TcADK1 presents a stage-specific expression. This variant was detected in epimastigotes cells, and was completely absent in trypomastigotes and amastigotes, while TcADK4 is present in the major life cycle stages of T. cruzi. Both variants are also regulated, in opposite ways, along the parasite growth curve suggesting that their expression depends on the intra- and extracellular conditions. Both, TcADK1 and TcADK4 present N-terminal extension that could be responsible for their subcellular localization. The presence of ADK variants in the flagellum would be critical for the provision of energy in a process of high ATP consumption such as cell motility.

High local diversity of Trypanosoma in a common bat species, and implications for the biogeography and taxonomy of the T. cruzi clade

The Trypanosoma cruzi clade is a group of parasites that comprises T. cruzi sensu lato and its closest relatives. Although several species have been confirmed phylogenetically to belong to this clade, it is uncertain how many more species can be expected to belong into this group. Here, we present the results of a survey of trypanosome parasites of the bat Artibeus jamaicensis from the Panamá Canal Zone, an important seed disperser. Using a genealogical species delimitation approach, the Poisson tree processes (PTP), we tentatively identified five species of trypanosomes - all belonging to the T. cruzi clade. A small monophyletic group of three putative Trypanosoma species places at the base of the clade phylogeny, providing evidence for at least five independent colonization events of these parasites into the New World. Artibeus jamaicensis presents a high diversity of these blood parasites and is the vertebrate with the highest number of putative trypanosome species reported from a single locality. Our results emphasize the need for continued efforts to survey mammalian trypanosomes.

A draft genome for the African crocodilian trypanosome Trypanosoma grayi

The availability of genome sequence data has greatly enhanced our understanding of the adaptations of trypanosomatid parasites to their respective host environments. However, these studies remain somewhat restricted by modest taxon sampling, generally due to focus on the most important pathogens of humans. To address this problem, at least in part, we are releasing a draft genome sequence for the African crocodilian trypanosome, Trypanosoma grayi ANR4. This dataset comprises genomic DNA sequences assembled de novo into contigs, encompassing over 10,000 annotated putative open reading frames and predicted protein products. Using phylogenomic approaches we demonstrate that T. grayi is more closely related to Trypanosoma cruzi than it is to the African trypanosomes T. brucei, T. congolense and T. vivax, despite the fact T. grayi and the African trypanosomes are each transmitted by tsetse flies. The data are deposited in publicly accessible repositories where we hope they will prove useful to the community in evolutionary studies of the trypanosomatids.