Isolation of Trypanosoma (Megatrypanum) theileri from dairy cattle in Taiwan

Aflagellar Epimastigote of Trypanosoma caninum: Biological and Ultrastructural Study of this Atypical Evolutionary Form

PURPOSE

Trypanosoma caninum exhibits atypical epimastigote forms under axenic conditions. This study aimed to analyze this evolutionary form under different cultivation conditions and provide more information about this evolutionary form.

METHODS

We selected a T. caninum isolate with a high percentage of aflagellar epimastigote forms in axenic cultures. Two separate growth curves were generated for T. caninum cultured in Schneider axenic medium and co-cultured with the DH82 cell line, followed by analysis and quantification of evolutionary forms using bright field microscopy. In addition, ultrastructural analysis of T. caninum was performed under both cultivation conditions.

RESULTS

The growth curves of T. caninum under axenic and co-cultivation conditions exhibited similar profiles. However, in the axenic culture, the number of parasites was three times higher at the peak of the exponential phase than in the co-culture. In contrast to that in the axenic culture, in which only the epimastigote forms were observed along the entire curve, during co-cultivation with the DH82 cell line, differentiation was observed for the trypomastigote and spheromastigote forms in low proportions. These results demonstrated that when cultured alone, the T. caninum isolate preserved the aflagellar epimastigote form, but in the presence of DH82 canine macrophages, they differentiated into evolutionary forms, particularly trypomastigote forms. Moreover, this study is the first to describe the presence of lipid bodies, structure described as the parasite's nutritional reserve, throughout the body of T. caninum.

CONCLUSIONS

These findings describe biological and ultrastructural aspects of epimastigote aflagellar and suggest that this evolutionary form may be involved in the biological cycle of T. caninum, still unknown.

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

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

Genetic and seasonal variations of Trypanosoma theileri and the association of Trypanosoma theileri infection with dairy cattle productivity in Northern Japan

Trypanosoma theileri is considered a non- or low-pathogenic trypanosome that generally causes latent infection in apparently healthy cattle; however, T. theileri propagates in the bloodstream and may cause clinical disease in pregnant animals or co-infection with bovine leukemia virus or Theileria orientalis. In the current study, a monthly survey of T. theileri infection over one year was carried out in a research dairy farm in Hokkaido, Japan to determine the 1) seasonal variations in the prevalence, 2) genetic characterization of T. theileri, and 3) associations of milk and blood parameters in dairy cattle with T. theileri infection, including data of metabolic profile tests and dairy herd performance tests, using linear mixed models. We found that 1) the prevalence of T. theileri infection was significantly higher in summer and winter than in other seasons; 2) T. theileri possibly showed genetic diversity in Eastern Hokkaido; and 3) T. theileri infection was associated with significantly lower levels of blood urea nitrogen, milk protein, and solids-not-fat, which are caused by a low rumen fermentation level. This is the first study to report the negative impact of T. theileri infection in dairy cattle, and our study indicates that control of T. theileri infection can improve the productivity of dairy cattle.

Molecular characterization of a new Trypanosoma (Megatrypanum) theileri isolate supports the two main phylogenetic lineages of this species in Japanese cattle

Trypanosoma (Megatrypanum) theileri is a cosmopolitan, usually non-pathogenic, trypanosome of cattle transmitted by blood-sucking arthropods, mainly tabanid flies. Several T. theileri strains isolated from domestic and wild ruminants via co-culturing with mammalian feeder cells or blood cells have been characterized morphologically and genetically. Here, we cultured a new trypanosome isolate from a Holstein cow in Hokkaido, Japan, and performed morphological and molecular characterization studies. The new isolate (Obihiro strain) was co-cultivated with Madin-Darby bovine kidney (MDBK) cells in GIT medium supplemented with 10% fetal bovine serum. Trypomastigotes and epimastigotes, but not intracellular parasites, were identified in the culture. Analysis of the V7-V8 region of 18S rRNA sequences showed that the Obihiro strain is positioned within the subgenus Megatrypanum. A dendrogram based on whole internal transcribed spacer rDNA sequence showed that the Obihiro strain clustered in the lineage TthII together with the Japanese isolates of T. theileri, Esashi 9, and Esashi 12, and isolates from Zambia and the USA. T. theileri of the KM strain and a T. theileri-like trypanosome isolated from deer (TSD1 strain) clustered in the lineage TthI, separate from the Obihiro strain. Based on a partial cathepsin L-like protein gene analysis, the Obihiro strain clustered with isolates of the TthIIF genotype, which includes T. theileri from Vietnam, Sri Lanka, and Brazil. Our analyses of the T. theileri Obihiro strain provide relevant insights into its genetic diversity in Japanese cattle and corroborate the host specificity of cattle and deer trypanosomes of the subgenus Megatrypanum.

Biological study of Trypanosoma caninum under co-culture with different feeder layer cells

Trypanosoma caninum is a parasite isolated from domestic dogs, of which several biological aspects remain unknown, including evolutive forms found in vertebrate hosts. The objective of this study was to evaluate co-cultures of T. caninum with different cell lines as feeder layers to monitor the differentiation process and investigate infective potential. The study was performed using DH-82, MDCK, and Lulo cell lines. T. caninum from axenic culture was added to the cultured adherent cells. At intervals over 30 days, aliquots of the supernatant were collected for quantification and assessment of differentiation. Infectivity assays were performed on the aforementioned cell lines seeded on glass coverslips and evaluated after 6, 24, and 72 h. In the supernatant of the feeder layer, T. caninum presented similar growth profiles, with epimastigote and trypomastigote forms in binary and multiple divisions. During co-culture with DH-82 and MDCK cells, a higher level of differentiation to trypomastigotes was observed. This study shows that the differentiation process of this parasite can vary according to culture conditions and that DH-82 and MDCK lineages could be applied to the study of trypomastigote forms. All forms of T. caninum described until now (aflagellar epimastigotes, typical epimastigotes, or trypomastigotes) were unable to infect the cell line Finally, this study provides additional data about morphobiological aspects. Although the biological cycle of T. caninum has not been established, the present data suggest the importance of feeder layers in promoting the growth and differentiation of this new parasite.

Genetic diversity and molecular survey of Trypanosoma (Megatrypanum ) theileri in cattle in Brazil’s western Amazon region

Abstract Trypanosoma (Megatrypanum) theileri is a flagellated protozoan that infects ruminants and it displays high genetic diversity. In this study, we investigated the prevalence rates of this protozoan based on hemoculture and molecular diagnosis. The isolates of T. theileri thus obtained were characterized by molecular markers SSU rDNA and gGAPDH and molecular diagnosis based on Cathepsin L-like gene (PCR-TthCATL). The PCR-TthCATL and hemoculture indicated an overall prevalence rate of 8.13%, and the CATL derived sequence named IB was identified for the first time in cattle in the western Amazon region, as well as IF in Brazil. We also describe a possible new PCR-TthCATL derived sequence in cattle, designated IL.

An Alternative Strategy for Trypanosome Survival in the Mammalian Bloodstream Revealed through Genome and Transcriptome Analysis of the Ubiquitous Bovine Parasite Trypanosoma (Megatrypanum) theileri

There are hundreds of Trypanosoma species that live in the blood and tissue spaces of their vertebrate hosts. The vast majority of these do not have the ornate system of antigenic variation that has evolved in the small number of African trypanosome species, but can still maintain long-term infections in the face of the vertebrate adaptive immune system. Trypanosoma theileri is a typical example, has a restricted host range of cattle and other Bovinae, and is only occasionally reported to cause patent disease although no systematic survey of the effect of infection on agricultural productivity has been performed. Here, a detailed genome sequence and a transcriptome analysis of gene expression in bloodstream form T. theileri have been performed. Analysis of the genome sequence and expression showed that T. theileri has a typical kinetoplastid genome structure and allowed a prediction that it is capable of meiotic exchange, gene silencing via RNA interference and, potentially, density-dependent growth control. In particular, the transcriptome analysis has allowed a comparison of two distinct trypanosome cell surfaces, T. brucei and T. theileri, that have each evolved to enable the maintenance of a long-term extracellular infection in cattle. The T. theileri cell surface can be modeled to contain a mixture of proteins encoded by four novel large and divergent gene families and by members of a major surface protease gene family. This surface composition is distinct from the uniform variant surface glycoprotein coat on African trypanosomes providing an insight into a second mechanism used by trypanosome species that proliferate in an extracellular milieu in vertebrate hosts to avoid the adaptive immune response.

Detection of an Unknown Trypanosoma DNA in a Phlebotomus stantoni (Diptera: Psychodidae) Collected From Southern Thailand and Records of New Sand Flies With Reinstatement of Sergentomyia hivernus Raynal & Gaschen, 1935 (Diptera: Psychodidae)

Although female sand flies are best known as the vectors of Leishmania parasites and viruses, several previous reports have demonstrated that these insects can also act as vectors for the trypanosomes of bats, lizards, and snakes. In this report, we created an inventory of Phlebotomine sand flies from southern Thailand. A novel trypanosome was found in a specimen of Phlebotomus stantoni, and two sand fly species newly recorded in the country, Sergentomyia khawi and Sergentomyia hivernus, were described. PCR primer pairs specific for the internal transcribed spacer 1 (ITS1) and the small subunit ribosomal DNA (SSU rDNA) gene of trypanosomatids were used to demonstrate the presence of the parasite in the sand fly. In addition, the Cytochrome b (CytB) gene was used to identify the sand fly species. Among the 45 samples of the sand fly that were collected, seven samples were Ph. stantoni sand flies and a single sample was positive for Trypanosoma sp. through PCR analysis. This study represents the first detection of Trypanosoma sp. in a sand fly from Thailand. The ITS1 and SSU rDNA sequences indicated that this specimen is suspected to be a novel Trypanosoma species. Further studies of this suspected new Trypanosoma species, including its vertebrate hosts and pathogenic potential, are therefore necessary.

Evidence of intracellular stages in Trypanosoma (Megatrypanum) theileri in non-phagocytic mammalian cells

Trypanosoma (subgenus Megatrypanum) theileri was first identified over one hundred years ago, and is a widespread parasite in cattle. Its life cycle within the mammalian host has rarely been reported. Whether there is an intracellular stage in tissues is unknown and such a stage has not been demonstrated experimentally. Intriguingly, using Giemsa staining with light microscopy and transmission electron microscopy examination, we found that the parasite was able not only to attach to cells but also to invade several phagocytic and non-phagocytic mammalian cells. Based on these findings, we conducted further investigations using a special antibody in immunofluorescence confocal images. Moreover, we examined a series of possible events of cell invasion in T. theileri. The results revealed that GM1, a marker of membrane rafts, was implicated in the mechanism of entry by this parasite. After incubation with tissue culture trypomastigotes, the gelatinolytic activity was significantly increased and accumulated at the attachment sites. Using ultrastructural localization detection by CytoTracker live imaging and confocal immunofluorescence microscopy, we found that lysosome fusion and the autophagy pathway were engaged in invaginating processes. T. theileri amastigotes also invaded cells and were enclosed by the lysosomes. Furthermore, tissue-cultured trypomastigotes were found to be capable of triggering intracellular free Ca(2+) transients and TGF-β-signaling. Our findings that intracellular amastigote stages exist in mammalian cells infected with T. theileri and that the invasion processes involved various host cell components and cell signalings were extremely surprising and warrant further investigation.

High genetic diversity in field isolates of Trypanosoma theileri assessed by analysis of cathepsin L-like sequences disclosed multiple and new genotypes infecting cattle in Thailand

In this study, we describe the first survey in Thailand of Trypanosoma theileri, a widespread and prevalent parasite of cattle that is transmitted by tabanid flies. Investigation of 210 bovine blood samples of Thai cattle from six farms by hematocrit centrifuge technique (HCT) revealed 14 samples with trypanosomes morphologically compatible to T. theileri. Additional animals were positive for T. theileri by PCR based on the Cathepsin L-like sequence (TthCATL-PCR) despite negative by HCT, indicating cryptic infections. Results revealed a prevalence of 26 ± 15% (95% CI) of T. theileri infection. Additionally, 12 samples positive for T. theileri were detected in cattle from other 11 farms. From a total of 30 blood samples positive by HCT and/or PCR from 17 farms, seven were characterized to evaluate the genetic polymorphism of T. theileri through sequence analysis of PCR-amplified CATL DNA sequences. All CATL sequences of T. theileri from Thai cattle clustered with sequences of the previously described phylogenetic lineages TthI and TthII, supporting only two major lineages of T. theileri in cattle around the world. However, 11 of the 29 CATL sequences analyzed showed to be different, disclosing an unexpectedly large polymorphic genetic repertoire, with multiple genotypes of T. theileri not previously described in other countries circulating in Thai cattle.