Tritrichomonas – Systematics of an enigmatic genus

Genetic diversity of Trichomonads from Milu deer (Elaphurus davidianus) in China

The Milu deer, or Père David's deer (Elaphurus davidianus), a rare endemic species in China, represents a case of successful reintroduction of a species previously considered extinct in the wild. Trichomonads, protozoan symbionts capable of infecting vertebrates, are transmitted via the fecal-oral route; they are a subgroup of Parabasalia and include some pathogenic species that pose zoonotic risks. Until now, data on the diversity and prevalence of trichomonads in Chinese Milu deer have not been reported. To better understand the colonization status of trichomonads, fecal samples from 112 Milu deer across five nature reserves in China were collected. The ITS-1/5.8S/ITS-2 sequences were amplified using PCR to investigate the colonization rate of trichomonads and to assess evolutionary relationships and genetic characteristics through phylogenetic analysis. An occurrence of 38.39% was recorded in Milu deer, with sample collection sites (OR = 55.159, 95% CI = 3.166-961.113, p = 0.006), high relative humidity and average annual rainfall (OR = 11.675, 95% CI = 1.747-77.781, p = 0.011) identified as significant risk factors for trichomonads colonization. Undescribed trichomonads from four genera were identified, including Simplicimonas spp., Hypotrichomonas spp., Hexamastix spp., and Tetratrichomonas spp. To our knowledge, this is the first study to report on trichomonads in Milu deer in China. This study aims to enhance understanding of trichomonad colonization and associated risk factors, providing scientific guidance for the ex-situ conservation of Milu deer.

High-Throughput Sequencing of faeces provides evidence for dispersal of parasites and pathogens by migratory waterbirds

Examination of faecal material has demonstrated how a broad range of organisms are distributed by bird movements. Such research has largely focused on dispersal of plant seeds by frugivores and of freshwater organisms by waterbirds. However, with few exceptions (e.g. avian influenza, Ebola virus), there is a dearth of evidence for transport of parasites and pathogens. High-throughput sequencing methods now provide a powerful means of addressing this knowledge gap by elucidating faecal contents in unprecedented detail. We collected faeces excreted by a range of migratory waterbirds in south-west Spain and pooled faecal DNA to create libraries reflective of feeding behavior. We created sets of libraries using high-throughput metagenomic and amplicon sequencing. For the latter we employed two sets of primers to broadly target the V4 region of the 18S rRNA gene (one set amplifying the region across all eukaryotes, the other excluding amplification of metazoans). Libraries revealed a wide diversity of eukaryotes, including parasites of the faecal producers themselves, parasites of food items, or those incidentally ingested. We also detected novel microbial eukaryotic taxa and found that parasite assemblage profiles were relatively distinct. Comparing the performance of the methods used supports their joint use for future studies of diversity and abundance. Because viable stages of many parasites are likely to be present in faeces, our results suggest significant levels of bird-mediated dispersal of parasites (both from avian and other hosts). Our methods revealed much hidden biodiversity, and allowed identification of the individuals who produced the faecal samples to species level, facilitating the study of interaction networks.

TriTOX: A novel Trichomonas vaginalis assay platform for high-throughput screening of compound libraries

Trichomonas vaginalis is a neglected urogenital parasitic protist that causes 170 million cases of trichomoniasis annually, making it the most prevalent non-viral, sexually transmitted disease. Trichomoniasis treatment relies on nitroheterocyclics, such as metronidazole. However, with increasing drug-resistance, there is an urgent need for novel anti-trichomonals. Little progress has been made to translate anti-trichomonal research into commercialised therapeutics, and the absence of a standardised compound-screening platform is the immediate stumbling block for drug-discovery. Herein, we describe a simple, cost-effective growth assay for T. vaginalis and the related Tritrichomonas foetus. Tracking changes in pH were a valid indicator of trichomonad growth (T. vaginalis and T. foetus), allowing development of a miniaturised, chromogenic growth assay based on the phenol red indicator in 96- and 384-well microtiter plate formats. The outputs of this assay can be quantitatively and qualitatively assessed, with consistent dynamic ranges based on Z' values of 0.741 and 0.870 across medium- and high-throughput formats, respectively. We applied this high-throughput format within the largest pure-compound microbial metabolite screen (812 compounds) for T. vaginalis and identified 43 hit compounds. We compared these identified compounds to mammalian cell lines, and highlighted extensive overlaps between anti-trichomonal and anti-tumour activity. Lastly, observing nanomolar inhibition of T. vaginalis by fumagillin, and noting this compound has reported activity in other protists, we performed in silico analyses of the interaction of fumagillin with its molecular target methionine aminopeptidase 2 for T. vaginalis, Giardia lamblia and Entamoeba histolytica, highlighting potential for fumagillin as a broad-spectrum anti-protistal against microaerophilic protists. Together, this new platform will accelerate drug-discovery efforts, underpin drug-resistance screening in trichomonads, and contributing to a growing body of evidence highlighting the potential of microbial natural products as novel anti-protistals.

Whole genome sequencing of a feline strain of Tritrichomonas foetus reveals massive genetic differences to bovine and porcine isolates

Tritrichomonas foetus is a protozoan parasite that colonizes the reproductive tract of cattle as well as the gastrointestinal tract of cats. Bovine tritrichomonosis is a sexually transmitted disease whereas feline tritrichomonosis is thought to be transmitted by the fecal-oral route. Furthermore, T. foetus is known as an essentially apathogenic commensal located in the nasal cavity of pigs. Transmission of T. foetus between the different hosts has to be considered a realistic scenario that may have important implications for the epidemiology of infections and disease. In our study, we generated whole genome sequencing (WGS) data from bovine, feline and porcine T. foetus strains to investigate the genetic (dis)similarities among these diverse strains. As a reference, we used a previously released draft assembly from a bovine T. foetus strain K isolated from an infected bull in Brazil. In particular, we identified single nucleotide polymorphisms (SNPs) and the insertion-deletion (indel) variations within the genomes of the different strains. Interestingly, only a low degree of polymorphism (68 SNPs and indels) was found between the bovine and the porcine strains in terms of variants with a predicted impact of moderate or high and where one species is homozygous for one allele and the other homozygous for the other allele. Conversely, however, a 964 times higher number of such differences was detected by comparing the feline with either the bovine (65,569) or the porcine (65,615) strain. These data clearly indicated a close phylogenetic relationship between bovine and porcine T. foetus but a remarkable genetic distinctness of these two strains from the feline strain. The latter observation was confirmed by PCR-based sequencing of 20 in silico-selected indel markers and five in silico-selected SNP markers that uniformly demonstrated a relatively distant phylogenetic relationship of three independent feline T. foetus isolates in comparison to the bovine and porcine strains investigated. In summary, our comparative genome sequencing approach provided further insights into the genetic diversity of T. foetus in relation to the different host origins of the parasite. Furthermore, our study identified a large number of SNP- and indel-containing sequences that may be useful molecular markers for future epidemiological studies aimed at the elucidation of the transmission patterns of T. foetus within different host species.

Insight into the biology of Mycobacterium mucogenicum and Mycobacterium neoaurum clade members

Nontuberculous mycobacteria, NTM, are of growing concern and among these members of the Mycobacterium mucogenicum (Mmuc) and Mycobacterium neoaurum (Mneo) clades can cause infections in humans and they are resistant to first-line anti-tuberculosis drugs. They can be isolated from different ecological niches such as soil, tap water and ground water. Mycobacteria, such as Mmuc and Mneo, are classified as rapid growing mycobacteria, RGM, while the most familiar, Mycobacterium tuberculosis, belongs to the slow growing mycobacteria, SGM. Modern “omics” approaches have provided new insights into our understanding of the biology and evolution of this group of bacteria. Here we present comparative genomics data for seventeen NTM of which sixteen belong to the Mmuc- and Mneo-clades. Focusing on virulence genes, including genes encoding sigma/anti-sigma factors, serine threonine protein kinases (STPK), type VII (ESX genes) secretion systems and mammalian cell entry (Mce) factors we provide insight into their presence as well as phylogenetic relationship in the case of the sigma/anti-sigma factors and STPKs. Our data further suggest that these NTM lack ESX-5 and Mce2 genes, which are known to affect virulence. In this context, Mmuc- and Mneo-clade members lack several of the genes in the glycopeptidolipid (GLP) locus, which have roles in colony morphotype appearance and virulence. For the M. mucogenicum type strain, Mmuc^T, we provide RNASeq data focusing on mRNA levels for sigma factors, STPK, ESX proteins and Mce proteins. These data are discussed and compared to in particular the SGM and fish pathogen Mycobacterium marinum. Finally, we provide insight into as to why members of the Mmuc- and Mneo-clades show resistance to rifampin and isoniazid, and why Mmuc^T forms a rough colony morphotype.

Multilocus analysis reveals further genetic differences between Tritrichomonas foetus from cats and cattle

Tritrichomonas foetus isolates from feline and bovine origin has been previously shown to carry a certain degree of genetic heterogeneity. Here, novel candidate molecular markers were developed by means of multilocus sequence typing of the gap2 gene (encoding for T. foetus glyceraldehyde-3-phosphate dehydrogenase), ITS region, the TR7/TR8 variable-length repeat and microsatellite genotyping. These markers were used to characterize T. foetus field isolates from bulls and domestic cats and to compare phylogenetically with the following ATCC isolates: T. foetus isolated from cattle and pig (syn. Tritrichomonas suis), Tritrichomonas mobilensis, Tetratrichomonas gallinarum and Pentatrichomonas hominis. Among them, TFMS10 and TFMS7 were found to be the most polymorphic markers. Moreover, an 809 bp fragment of the gap2 gene was successfully amplified from all the trichomonads included in this study and the sequence analysis revealed differences between T. foetus porcine and feline genotypes and T. mobilensis in comparison to the bovine T. foetus ATCC isolate. The TR7/TR8 repeat pattern was not reproducible, being only consistent the fragments of approximately 110 and 217 bp. Sequence analysis of the latter revealed the existence of 3 SNPs resulting in 98.6 % homology between bovine and feline isolates. A search for similar sequences was carried out to develop a Restriction Length Fragment Polymorphism analysis. A 503 bp region, named TF1, revealed the existence of two BbvI restriction enzyme sites that were able to generate different length fragments for T. foetus feline and bovine isolates. Finally, the neighbour-joining analyses showed that T. foetus porcine genotype clusters together with bovine genotype, whereas T. mobilensis and the feline genotype form a separate cluster.

Development and comparative evaluation of different LAMP and PCR assays for coprological diagnosis of feline tritrichomonosis

The protozoan parasite Tritrichomonas foetus may cause severe diarrhea in cats all over the world. In order to evaluate the methodology in coprological molecular diagnosis of feline tritrichomonosis, we compared previously published ("old") and newly developed ("novel") loop-mediated isothermal amplification (LAMP) (targeted to the T. foetus β-tubulin and the elf1α 1 gene, respectively) as well as an old conventional and an old and novel real-time PCR (all targeted to overlapping regions of T. foetus rDNA) assays regarding their diagnostic sensitivities and specificities. Here, the novel real-time PCR yielded the best methodical performance in that a sensitivity with a detection limit of <0.1 trophozoites (corresponding to ca.<0.13 trophozoites per mg feces) and a maximal specificity for diagnosis of Tritrichomonas spp. was achieved. The other test systems exhibited either an approximately 10-times lower sensitivity (<1 trophozoite corresponding to ca.<1.3 trophozoites per mg feces) (conventional PCR and both LAMP assays) or a lower specificity (old real-time PCR). Conversely, the diagnostic performance assessed with clinical fecal samples from cats demonstrated identical sensitivities (8 of 20 samples tested were positive) for the novel PCR and both LAMP assays. Diagnostic sensitivities were significantly higher than those found for the old real-time (5 positive samples) and conventional PCR (6 positive samples), respectively. Accordingly, our data suggested the novel PCR and both LAMP assays to be well suited molecular tools for direct (i.e. without including an in vitro cultivation step) coprological diagnosis of tritrichomonosis in cats. Interestingly, relative high (novel LAMP, 7 positive samples) to at least moderate (old LAMP, 6 positive samples and 1 sample with equivocal score) diagnostic sensitivities were also achieved by testing clinical samples upon simple visual inspection of colorimetric changes during the LAMP amplification reactions. Accordingly, both LAMP assays may serve as practical molecular tools to perform epidemiological studies on feline (and bovine as well as porcine) tritrichomonosis under simple laboratory conditions.

Genetic Indicators of Drug Resistance in the Highly Repetitive Genome of Trichomonas vaginalis

Trichomonas vaginalis, the most common nonviral sexually transmitted parasite, causes ∼283 million trichomoniasis infections annually and is associated with pregnancy complications and increased risk of HIV-1 acquisition. The antimicrobial drug metronidazole is used for treatment, but in a fraction of clinical cases, the parasites can become resistant to this drug. We undertook sequencing of multiple clinical isolates and lab derived lines to identify genetic markers and mechanisms of metronidazole resistance. Reduced representation genome sequencing of ∼100 T. vaginalis clinical isolates identified 3,923 SNP markers and presence of a bipartite population structure. Linkage disequilibrium was found to decay rapidly, suggesting genome-wide recombination and the feasibility of genetic association studies in the parasite. We identified 72 SNPs associated with metronidazole resistance, and a comparison of SNPs within several lab-derived resistant lines revealed an overlap with the clinically resistant isolates. We identified SNPs in genes for which no function has yet been assigned, as well as in functionally-characterized genes relevant to drug resistance (e.g., pyruvate:ferredoxin oxidoreductase). Transcription profiles of resistant strains showed common changes in genes involved in drug activation (e.g., flavin reductase), accumulation (e.g., multidrug resistance pump), and detoxification (e.g., nitroreductase). Finally, we identified convergent genetic changes in lab-derived resistant lines of Tritrichomonas foetus, a distantly related species that causes venereal disease in cattle. Shared genetic changes within and between T. vaginalis and Tr. foetus parasites suggest conservation of the pathways through which adaptation has occurred. These findings extend our knowledge of drug resistance in the parasite, providing a panel of markers that can be used as a diagnostic tool.

Trichomonas

The most widely known trichomonad in veterinary medicine is Tritrichomonas foetus. It is the etiologic agent of bovine tritrichomonosis, a sexually transmitted disease in extensively managed herds throughout many geographic regions worldwide. The same trichomonad species is also regarded as the causative agent of chronic diarrhea in the domestic cat, although more recent studies observed molecular differences between bovine- and feline-derived T. foetus. Trichomonosis in cats has a worldwide distribution and is mainly present among cats from high-density housing environments. Other trichomonads are found as inhabitants of the gastrointestinal tract in birds, such as Trichomonas gallinae. Particularly, Columbiformes, Falconiformes, Strigiformes, and wild Passeriformes can be severely affected by avian trichomonads. Diagnosis of trichomonosis is often complicated by the fragility of the parasite. To ensure valid test results, it is essential to collect and handle specimens in the right way prior to analysis. Cultivation tests, the specific amplification of parasites, or a combination of both test methods is the most efficient and most commonly used way to diagnose trichomonosis in animals. Bovine tritrichomonosis is mainly controlled by the identification and withdrawal of infected animals from bovine herds. The control of feline and avian trichomonosis relies mainly on preventive measures.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): Trichomonosis

Trichomonosis has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on the eligibility of trichomonosis to be listed, Article 9 for the categorisation of trichomonosis according to disease prevention and control rules as in Annex IV and Article 8 on the list of animal species related to trichomonosis. The assessment has been performed following a methodology composed of information collection and compilation, expert judgement on each criterion at individual and, if no consensus was reached before, also at collective level. The output is composed of the categorical answer, and for the questions where no consensus was reached, the different supporting views are reported. Details on the methodology used for this assessment are explained in a separate opinion. According to the assessment performed, trichomonosis can be considered eligible to be listed for Union intervention as laid down in Article 5(3) of the AHL. The disease would comply with the criteria as in sections 3, 4 and 5 of Annex IV of the AHL, for the application of the disease prevention and control rules referred to in points (c), (d) and (e) of Article 9(1). The animal species to be listed for trichomonosis according to Article 8(3) criteria is cattle as susceptible and reservoir.

Report of the first clinical case of intestinal trichomoniasis caused by Tritrichomonas foetus in a cat with chronic diarrhoea in Brazil

Background

Tritrichomonas foetus is an emergent and important enteric pathogen of cats, which causes prolonged diarrhoea in cats.

Case presentation

This study describes a T. foetus infection in a seven-month-old, entire male domestic shorthair kitten with a six-month history of persistent large intestinal diarrhoea, faecal incontinence, prostration, apathy and weight loss. Parasites were microscopically observed and confirmed by PCR and DNA sequencing. Molecular analyses were carried out comparing the sequence obtained in this study with T. foetus and T. suis. Retrieved from GenBank. After treatment with ronidazole, the cat showed resolution of clinical signs.

Conclusions

This is the first clinical case of T. foetus infection in a chronic diarrheic cat in Brazil and South America, confirming the presence of this pathogen in this part of the world and highlighting the importance of this protozoa being considered in the differential diagnosis of cats presenting diarrhoea of the large intestine. Our case report enriches our knowledge on the geographical distribution of T. foetus in cats in Brazil and provides further understanding of the clinical significance of feline intestinal trichomoniasis in this country.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-017-1026-3) contains supplementary material, which is available to authorized users.

The conundrum of feline Trichomonosis

Practical relevance: Trichomonosis of the large intestine of the cat was described as a cause of chronic diarrhea over 20 years ago. The trichomonad was identified as Tritrichomonas foetus, with a genotype that is distinct from venereal T foetus of cattle. Clinical challenges: Despite multiple means for diagnosis of the infection, including light microscopy, protozoal culture and PCR amplification using species-specific primers, tests with even greater sensitivity are needed. Feline trichomonosis is resistant to all commonly used antiprotozoal drugs. Ronidazole is currently the only drug demonstrated to be effective in eliminating the infection from cats; however, this drug has a narrow safety margin and clinical resistance is increasingly recognized. The more we learn about trichomonosis in cats, the more complicated and controversial the infection has become, ranging from what we should call the organism to whether we should even bother trying to treat it. Global importance: Feline trichomonosis is recognized to occur worldwide and is regarded as one of the most common infectious causes of colitis in the domestic cat. The infection is widespread in catteries and shelters; and, while remission of diarrhea may occur over time, persistence of the infection is common. Evidence base: This review provides a comprehensive examination of what is currently known about feline trichomonosis and pinpoints areas, based on the authors' opinion, where further research is needed.

What is the importance of zoonotic trichomonads for human health?

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Trichomonads represent emerging species of medical and veterinary importance.

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Clinical and molecular evidence suggest a zoonotic potential for trichomonads.

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Close relationship between avian and human trichomonads revealed in outbreaks.

Trichomonads are common parasites of many vertebrate and invertebrate species, with four species classically recognized as human parasites: Dientamoeba fragilis, Pentatrichomonas hominis, Trichomonas vaginalis, and Trichomonas tenax. The latter two species are considered human-specific; by contrast, D. fragilis and P. hominis have been isolated from domestic and farm mammals, demonstrating a wide host range and potential zoonotic origin. Several new studies have highlighted the zoonotic dimension of trichomonads. First, species typically known to infect birds and domestic mammals have been identified in human clinical samples. Second, several phylogenetic analyses have identified animal-derived trichomonads as close sister taxa of the two human-specific species. It is our opinion, therefore, that these observations prompt further investigation into the importance of zoonotic trichomonads for human health.

Intestinal Tritrichomonas foetus infection in cats: a retrospective study of 104 cases

The clinical presentation and response to treatment of cats infected with Tritrichomonas foetus have not been sufficiently described in a large number of pet cats. The aim of this study was to collect and analyze clinical data from pet cats diagnosed with intestinal T foetus infection. Clinical information was collected for 104 cats that tested polymerase chain reaction-positive for T foetus. The most common clinical sign was diarrhea (98%) with a median duration of 135 days (range 1-2880 days). Forty-nine of 83 (59%) cats had diarrhea since adoption. Other clinical signs included anorexia (22%), depression (24%), weight loss or failure to gain weight (20%), vomiting (19%), abdominal pain (9%) and increased appetite (3%). A total of 45 cats had completed treatment with ronidazole, 29 of which (64%) showed a good clinical response to treatment. Sixteen (36%) cats had either partial or no improvement, or a relapse shortly after discontinuation of treatment.

Comparative analysis of Tritrichomonas foetus (Riedmüller, 1928) cat genotype, T. foetus (Riedmüller, 1928) cattle genotype and Tritrichomonas suis (Davaine, 1875) at 10 DNA loci

The parasitic protists in the genus Tritrichomonas cause significant disease in domestic cattle and cats. To assess the genetic diversity of feline and bovine isolates of Tritrichomonas foetus (Riedmüller, 1928) Wenrich and Emmerson, 1933, we used 10 different genetic regions, namely the protein coding genes of cysteine proteases 1, 2 and 4-9 (CP1, 2, 4-9) involved in the pathogenesis of the disease caused by the parasite. The cytosolic malate dehydrogenase 1 (MDH1) and internal transcribed spacer region 2 of the rDNA unit (ITS2) were included as additional markers. The gene sequences were compared with those of Tritrichomonas suis (Davaine, 1875) Morgan and Hawkins, 1948 and Tritrichomonas mobilensisCulberson et al., 1986. The study revealed 100% identity for all 10 genes among all feline isolates (=T. foetus cat genotype), 100% identity among all bovine isolates (=T. foetus cattle genotype) and a genetic distinctness of 1% between the cat and cattle genotypes of T. foetus. The cattle genotype of T. foetus was 100% identical to T. suis at nine loci (CP1, 2, 4-8, ITS2, MDH1). At CP9, three out of four T. suis isolates were identical to the T. foetus cattle genotype, while the T. suis isolate SUI-H3B sequence contained a single unique nucleotide substitution. Tritrichomonas mobilensis was 0.4% and 0.7% distinct from the cat and cattle genotypes of T. foetus, respectively. The genetic differences resulted in amino acid changes in the CP genes, most pronouncedly in CP2, potentially providing a platform for elucidation of genotype-specific host-pathogen interactions of T. foetus. On the basis of this data we judge T. suis and T. foetus to be subjective synonyms. For the first time, on objective nomenclatural grounds, the authority of T. suis is given to Davaine, 1875, rather than the commonly cited Gruby and Delafond, 1843. To maintain prevailing usage of T. foetus, we are suppressing the senior synomym T. suisDavaine, 1875 according to Article 23.9, because it has never been used as a valid name after 1899 and T. foetus is widely discussed as the cause of bovine trichomonosis. Thus bovine, feline and porcine isolates should all be given the name T. foetus. This promotes the stability of T. foetus for the veterinary and economically significant venereal parasite causing bovine trichomonosis.