Nucleotide sequence heterogeneity in the small subunit ribosomal RNA gene variable (V4) region among and within geographic isolates of Theileria from cattle, elk and white-tailed deer

Potential novel Colpodella spp. (phylum Apicomplexa) and high prevalence of Colpodella spp. in goat-attached Haemaphysalis longicornis ticks in Shandong province, China

Tick-borne Apicomplexan parasites pose a significant threat to both public health and animal husbandry. Identifying potential pathogenic parasites and gathering their epidemiological data are essential for prospectively preventing and controlling infections. In the present study, genomic DNA of ticks collected from two goat flocks (Goatflock1 and Goatflock2) and one dog group (Doggroup) were extracted and the 18S rRNA gene of Babesia/Theileria/Colpodella spp. was amplified by PCR and sequenced. Phylogenetic analysis was conducted based on the obtained sequences. The differences in pathogen positive rates between ticks of different groups were statistically analyzed using the Chi-square or continuity-adjusted Chi-square test. As a result, two pathogenic Theileria (T.) luwenshuni genotypes, one novel pathogenic Colpodella sp. HLJ genotype, and two potential novel Colpodella spp. (referred to as Colpodella sp. struthionis and Colpodella sp. yiyuansis in this study) were identified in the Haemaphysalis (H.) longicornis ticks. Ticks of Goatflock2 had a significantly higher positive rate of Colpodella spp. than those from Goatflock1 (χ2=92.10; P = 8.2 × 10-22) and Doggroup (χ2=42.34; P = 7.7 × 10-11), and a significantly higher positive rate of T. luwenshuni than Doggroup (χ2=5.38; P = 0.02). However, the positive rates of T. luwenshuni between Goatflock1 and Goatflock2 were not significantly different (χ2=2.02; P = 0.16), and so as the positive rates of both pathogens between Goatflock1 and Doggroup groups (P > 0.05). For either Colpodella spp. or T. luwenshuni, no significant difference was found in prevalence between male and female ticks. These findings underscore the potential importance of Colpodella spp. in domestic animal-attached ticks, as our study revealed two novel Colpodella spp. and identified Colpodella spp. in H. longicornis for the first time. The study also sheds light on goats' potential roles in the transmission of Colpodella spp. to ticks and provides crucial epidemiological data of pathogenic Theileria and Colpodella. These data may help physicians, veterinarians, and public health officers prepare suitable detection and treatment methods and develop prevention and control strategies.

A survey of piroplasms in white-tailed deer (Odocoileus virginianus) in the southeastern United States to determine their possible role as Theileria orientalis hosts

In 2017, clinical disease and mortality in cattle associated with Theileria orientalis Ikeda was reported in Virginia, U.S. The exotic tick, Haemaphysalis longicornis, is a competent vector for this species. White-tailed deer (Odocoileus virginianus) are commonly infested with H. longicornis in the eastern U.S. and are also infected with several genotypes of piroplasms such as a Theileria sp. (often called Theileria cervi-like), Babesia odocoilei, and Babesia sp. H10. However, it is currently unknown if deer are susceptible to T. orientalis and can act as potential hosts. In this study, we tested 552 white-tailed deer samples from the southeastern U.S. to determine the presence of T. orientalis. We used a PCR-RFLP to test 293 (53%) of these samples to distinguish between piroplasm genera. A total of 189 white-tailed deer were positive with Theileria, 47 were positive with Babesia, and 57 did not amplify. Because this assay does not determine species, we sequenced 30 random samples targeting a fragment of the 18S rRNA gene. Although a high diversity of Theileria and Babesia spp. were detected, none were T. orientalis. All 552 samples were then screened with a T. orientalis specific real-time PCR protocol, but none were positive for T. orientalis. Our data suggests that white-tailed deer are commonly infected with piroplasm species but not T. orientalis.

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Piroplasm parasites of 552 white-tailed deer were surveyed in the Eastern U.S.

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A high prevalence and diversity of Theileria and Babesia species were observed.

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No infections with exotic Theileria orientalis Ikeda was detected in white-tailed deer.

Evaluation of sporozoite and macroschizont antigen (Spm2) of Theileria annulata for its diagnostic potential

Theileria are tick-borne apicomplexan parasites, which mainly infect ruminants in tropical and subtropical regions of the world. The present study was directed to investigate the serological methods for the diagnosis of theileriosis in crossbred cattle. Blood samples (n = 176) were collected from the regional cattle populations of Bihar state situated at the Gangetic plains of India. Microscopic examination of blood smears from the cattle revealed the presence of tick-borne infectious organisms (Theileria and Anaplasma) in the region. PCR-based detection of Tams1 (Theileria annulata merozoite surface antigen) gene and the sequencing of 18S rRNA amplicon from the blood samples confirmed T. annulata as the primary causative agent of theileriosis in cattle of the Bihar region. Similarly, the amplification of the msp5 gene confirmed Anaplasma marginale infection. For the large-scale epidemiological investigation, sporozoite and macroschizont (spm2) partial gene from T. annulata was cloned in pET-28a (+) vector and overexpressed in E. coli BL21 cells. Overexpressed recombinant-Spm2 (43 kDa) was purified by Ni-NTA affinity chromatography and was used for immunodetection of theileriosis in cattle serum samples. Sequence analysis of the cloned partial spm2 gene in this study showed multiple SNPs (single nucleotide polymorphisms) in T. annulata. Recombinant-Spm2 antigen was explicitly recognised by the immunoglobulins (IgG) of the cattle naturally infected with Theileria. Further, an indirect enzyme-linked immunosorbent assay (ELISA) was developed using partial r-Spm2 antigen that exhibited high sensitivity (100 %) and specificity (90.9 %). Thus, this study suggests that partial r-Spm2 can be used as a diagnostic antigen for seroepidemiological studies of T. annulata infection in crossbred cattle.

Molecular screening for rickettsial bacteria and piroplasms in ixodid ticks surveyed from white-tailed deer (Odocoileus virginianus) and nilgai antelope (Boselaphus tragocamelus) in southern Texas

A survey of ixodid ticks parasitizing white-tailed deer (Odocoileus virginianus) and nilgai antelope (Boselaphus tragocamelus) was completed during the 2018–2019 public hunt season on the Laguna Atascosa National Wildlife Refuge (Cameron County, Texas) and the East Foundation's El Sauz Ranch in nearby Willacy County (Texas). Anocenter nitens was the predominant tick species identified with 5% of these ticks collected from nilgai. All life stages were encountered in high numbers on white-tailed deer, indicating that deer may be a primary host in this region. Amblyomma maculatum and Amblyomma inornatum were identified from both hosts, while Ixodes scapularis was encountered only on white-tailed deer. This is the first published record of A. inornatum on nilgai. A subset of ticks was used in PCR assays to detect Rickettsia spp., family Anaplasmataceae, Borrelia spp., and Theileria-Babesia spp. Borrelia spp. were not detected in any of the ticks analyzed. Rickettsia parkeri was detected in three A. maculatum adult ticks from deer, Rickettsia sp. endosymbiont sequences were present in all I. scapularis ticks, and Rickettsia amblyommatis was detected in three A. inornatum adult ticks from deer. Sequence analysis of Anaplasmataceae-positive amplicons from A. nitens and A. maculatum had low percent identity to published Anaplasma spp. sequences, suggesting a unique Anaplasma sp. may be circulating in the population. Anaplasma platys was detected from A. nitens larvae and an Ehrlichia sp. Delta strain was present in A. maculatum, both of unknown pathogenicity towards deer. Theileria cervi was detected in all stages of A. nitens ticks, and positive ticks originated from 27 of 31 deer and a single nilgai sampled from throughout the survey site. The primary vector for T. cervi is absent from this region, suggesting T. cervi is possibly maintained by a different tick species.

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Anocenter nitens predominates on white-tailed deer and nilgai in southern Texas.

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Theileria cervi was detected in Anocenter nitens ticks from deer and a single nilgai.

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Three Theileria cervi genotypes were detected in this region of southern Texas.

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Unique Anaplasma sp. detected in A. nitens; low identity to known Anaplasma sp.

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Amblyomma inornatum ticks were identified on nilgai; a first record on this host.

Theileria orientalis Ikeda in host-seeking Haemaphysalis longicornis in Virginia, U.S.A

The Asian longhorned tick, Haemaphysalis longicornis, has recently become established in the United States. In East Asia, Australia, and New Zealand, the native and previously introduced ranges, this tick is a vector of an important pathogen of cattle, Theileria orientalis. In 2017, the pathogenic Ikeda genotype of T. orientalis was associated with cattle mortalities in Virginia and in 2018 the exotic H. longicornis was detected at this same site. To investigate the possible role of this exotic tick in the epidemiology of theileriosis in Virginia, we tested host-seeking H. longicornis for piroplasm infections. We document the detection of exotic Theileria orientalis Ikeda genotype in 12.7 % (15/118) environmentally collected H. longicornis using both the 18S rRNA and major piroplasm surface protein (MPSP) gene targets. This is the first detection of a pathogen in H. longicornis in its introduced range in the United States and offers new insight into the animal health risks associated with the introduction of this exotic tick species to North America.

An appraisal of oriental theileriosis and the Theileria orientalis complex, with an emphasis on diagnosis and genetic characterisation

Oriental theileriosis, a tick-borne disease of bovids caused by members of the Theileria orientalis complex, has a worldwide distribution. Globally, at least 11 distinct genotypes of T. orientalis complex, including type 1 (chitose), type 2 (ikeda), type 3 (buffeli), types 4 to 8, and N1-N3, have been described based on the sequence of the major piroplasm surface protein (MPSP) gene. Of these 11 genotypes, mainly ikeda and chitose are known to be pathogenic and cause considerable morbidity (including high fever, anaemia, jaundice and abortion), production losses and/or mortality in cattle. Mixed infections with two or more genotypes of T. orientalis is common, but do not always lead to a clinical disease, posing challenges in the diagnosis of asymptomatic or subclinical forms of oriental theileriosis. The diagnosis of oriental theileriosis is usually based on clinical signs, the detection of piroplasms of T. orientalis in blood smears, and/or the use of serological or molecular techniques. This paper reviews current methods used for the diagnosis of T. orientalis infections and the genetic characterisation of members of the T. orientalis complex, and proposes that advanced genomic tools should be established for investigations of these and related haemoparasites.

Genetic characterization of Theileria species infecting bovines in India

Genetic characterization of Theileria species infecting bovines in India was attempted targeting the 18S ribosomal RNA region of the parasite. Blood samples of bovines (n = 452), suspected for haemoprotozoan infections, from 9 different states of the country were microscopically examined for Theileria species infection. Four Theileria spp. positive blood samples from each state were randomly utilized for PCR amplification of the 18S rRNA gene (approx. 1529 bp) followed by cloning and sequencing. The sequence data analysis of all the 36 isolates revealed that 33 isolates had high sequence similarity with published sequences of T. annulata, whereas 3 isolates (MF287917, MF287924 and MF287928) showed close similarity with published sequences of T. orientalis. Sequence homology within the isolates ranged between 95.8 and 100% and variation in the length of targeted region was also noticed in different isolates (1527-1538 nt). Phylogenetic tree created for T. annulata sequences revealed that a total of 24 Indian isolates formed a major clade and grouped together with isolates originating from countries like China, Spain, Turkey and USA. Remaining 09 isolates clustered in a separate group and were closely related to the TA5 isolate of T. annulata (a new genotype) originating from India and also with the isolates from East Asian countries like Japan and Malaysia. All the three T. orientalis isolates had minimal intraspecific variation (99-100% homology) amongst themselves. Further, in the phylogenetic analysis T. orientalis Indian isolates were found to cluster away from other 14 isolates of T. buffeli/sergenti/orientalis originating from different countries (Australia, China, Indonesia and Spain). However, these 3 isolates clustered together with the T. buffeli Indian isolate (EF126184). Present study confirmed the circulation of different genotypes of T. annulata in India, along with T. orientalis isolates.

Guidelines for the Detection of Babesia and Theileria Parasites

The genera Babesia and Theileria (phylum Apicomplexa, order Piroplasmida) are mainly transmitted by Ixodid ticks in which the sexual part of their life cycle followed by sporogony takes place. They include protozoan parasites that infect erythrocytes of a variety of vertebrate hosts, including domestic and wild animals, with some Babesia spp. also infecting humans. Babesia sporozoites transmitted in the tick's saliva during the bloodmeal directly infect erythrocytes, where they asexually multiply to produce pear-shaped merozoites in the process of merogony; whereas a pre-erythrocytic schizogonic life stage in leukocytes is found in Theileria and precedes merogony in the erythrocytes. The wide spectrum of Babesia and Theileria species and their dissimilar characteristics with relation to disease severity, transmission, epidemiology, and drug susceptibility stress the importance of accurate detection of babesiosis and theileriosis and their causative agents. These guidelines review the main methods currently used for the detection of Babesia and Theileria spp. for diagnostic purposes as well as epidemiological studies involving their vertebrate hosts and arthropod vectors. Serological methods were not included once they did not indicate current infection but rather exposure.

Diversity of Haemaphysalis-associated piroplasms of ruminants in Central-Eastern Europe, Hungary

Background

Increasing numbers of genetic variants are being recognized among piroplasms, but the precise taxonomical status, the tick vector and the geographical range of several species or genotypes are still unknown. Bovine piroplasmosis was reported to re-emerge in north-east Hungary. Because Theileria-infection was newly diagnosed in one cattle herd in the same region of the country, the aim of this study was to molecularly identify the relevant agent, to find its local vector tick species, and to examine the range of Babesia/Theileria spp. of ruminants in Haemaphysalis sp. ticks collected previously in Hungary.

Findings

Blood samples were drawn on two occasions from 90 dairy cattle in northern Hungary, and ticks were collected on their pastures. In addition, questing ticks (315 Haemaphysalis inermis, 259 H. concinna and 22 H. punctata), which originated mainly in the same region of the country from 2007, were included in the study. DNA was extracted from these samples, followed by molecular analysis for piroplasms.

In the cattle Theileria orientalis was identified, with 100 % sequence homology to isolates from Japan, China, South-Africa and Australia. Based on GenBank data this genotype has not been previously reported in Europe. The prevalence of infection in the herd remained almost constant in the main tick season, suggesting exposure in previous years.

Retrospective analysis of ticks revealed the presence of Babesia crassa in H. inermis, for the first time in Europe and in this tick species. On the other hand, H. concinna carried five different piroplasms, including B. motasi that was also newly detected in Central-Eastern Europe and in this tick species; whereas H. punctata harboured Theileria sp. OT3, hitherto known to occur in the Mediterranean region.

Conclusions

Results of this study broaden the range of piroplasms that are infective for ruminants in Central-Eastern Europe. Although bovine babesiosis and theileriosis was known to occur in Hungary, molecular evidence is provided here for the first time on the presence of Babesia and/or Theileria spp. of sheep, goats and cervids in Hungary.

Molecular and Phylogenetic analysis revealed new genotypes of Theileria annulata parasites from India

Background

Tick borne diseases impinge cattle worldwide causing mortality and resulting in huge economic losses. Theileriosis is one of the important tick borne diseases mainly caused by Theileria annulata and one of the commonly occurring infections among the livestock. T. annulata causes immense loss to the livestock industry and therefore, efficacious eradication and control strategies are needed for the control of the disease. Genetic diversity among T. annulata parasites is another important aspect which is overlooked in India. Thus, the present study aims to evaluate the prevalence along with genetic diversity and phylogeny of the prevailing T. annulata population of India.

Methods

Genomic DNA was extracted from cattle blood samples (n = 862) from different regions of Andhra Pradesh. Molecular diagnosis using T. annulata 18S rRNA based PCR was performed to detect parasites in cattle. Further, 18S rRNA gene was cloned and sequenced to determine similarity and diversity from the known T. annulata sequences.

Results

We observed an overall prevalence rate of 32.40 % T. annulata infection in Andhra Pradesh based on PCR assay. The sequence analysis revealed novel genotypes among the T. annulata strains from India. Thirteen strains showed closed proximity with a strain from China whereas one Indian strain showed similarity with a South African strain [Theileria sp (buffalo)] based on phylogenetic analysis. Nucleotide heterogeneity of the 18S rRNA sequence among the strains examined varied from 0.1 to 8.6 % when compared with the published strains.

Conclusion

The present study provides us with the molecular prevalence of theileriosis, and will support the accomplishment of actions or in design of strategy to control theileriosis transmission to cattle. Additionally, it highlights the emergence of strains with novel genotypes from India.

A review of Theileria diagnostics and epidemiology

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Serological and molecular assays exist for most economic important Theileria species.

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Molecular assays are constantly being improved with regard to sensitivity and specificity.

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The concept of what constitute a Theileria species impacts on accurate diagnostics.

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Analytical specificity of molecular assays are >800 000 parasites/L blood.

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Parasitemia ranges may determine practical limits of detection.

An extensive range of serological and molecular diagnostic assays exist for most of the economically important Theileira species such as T. annulata, T. equi, T. lestoquardi, T. parva, T. uilenbergi and other more benign species. Diagnostics of Theileria is considered with regard to sensitivity and specificity of current molecular and serological assays and their use in epidemiology. In the case of serological assays, cross-reactivity of genetically closely related species reduces the use of the gold standard indirect fluorescent antibody test (IFAT). Development of antigen-specific assays does not necessarily address this problem, since closely related species will potentially have similar antigens. Even so, serological assays remain an important line of enquiry in epidemiological surveys. Molecular based assays have exploded in the last decade with significant improvements in sensitivity and specificity. In this review, the current interpretation of what constitute a species in Theileria and its impact on accurate molecular diagnostics is considered. Most molecular assays based on conventional or real-time PCR technology have proven to be on standard with regard to analytical sensitivity. However, consideration of the limits of detection in regard to total blood volume of an animal indicates that most assays may only detect >400,000 parasites/L blood. Even so, natural parasitaemia distribution in carrier-state animals seems to be above this limit of detection, suggesting that most molecular assays should be able to detect the majority of infected individuals under endemic conditions. The potential for false-negative results can, however, only be assessed within the biological context of the parasite within its vertebrate host, i.e. parasitaemia range in the carrier-state that will support infection of the vector and subsequent transmission.

Phylogeny of Theileria buffeli genotypes identified in the South African buffalo (Syncerus caffer) population

Theileria buffeli/orientalis is a group of benign and mildly pathogenic species of cattle and buffalo in various parts of the world. In a previous study, we identified T. buffeli in blood samples originating from the African buffalo (Syncerus caffer) in the Hluhluwe-iMfolozi Game Park (HIP) and the Addo Elephant Game Park (AEGP) in South Africa. The aim of this study was to characterise the 18S rRNA gene and complete internal transcribed spacer (ITS1-5.8S-ITS2) region of T. buffeli samples, and to establish the phylogenetic position of this species based on these loci. The 18S rRNA gene and the complete ITS region were amplified from DNA extracted from blood samples originating from buffalo in HIP and AEGP. The PCR products were cloned and the resulting recombinants sequenced. We identified novel T. buffeli-like 18S rRNA and ITS genotypes from buffalo in the AEGP, and novel Theileria sinensis-like 18S rRNA genotypes from buffalo in the HIP. Phylogenetic analyses indicated that the T. buffeli-like sequences were similar to T. buffeli sequences from cattle and buffalo in China and India, and the T. sinensis-like sequences were similar to T. sinensis 18S rRNA sequences of cattle and yak in China. There was extensive sequence variation between the novel T. buffeli genotypes of the African buffalo and previously described T. buffeli and T. sinensis genotypes. The presence of organisms with T. buffeli-like and T. sinensis-like genotypes in the African buffalo could be of significant importance, particularly to the cattle industry in South Africa as these animals might act as sources of infections to naïve cattle. This is the first report on the characterisation of the full-length 18S rRNA gene and ITS region of T. buffeli and T. sinensis genotypes in South Africa. Our study provides invaluable information towards the classification of this complex group of benign and mildly pathogenic species.

Additional data for a new Theileria sp. from China based on the sequences of ribosomal RNA internal transcribed spacers

Theileria sinensis was recently isolated and named as an independent Theileria species that infects cattle in China. To date, this parasite has been described based on its morphology, transmission and molecular studies, indicating that it should be classified as a distinct species. To test the validity of this taxon, the two internal transcribed spacers (ITS1 and ITS2) and the 5.8S rRNA gene were cloned and sequenced from three T. sinensis isolates. The complete ITS sequences were compared with those of other Theileria sp. available in GenBank. Phylogenetic analyses based on sequence data for the complete ITS sequences indicate that T. sinensis lies in a distinct clade that is separate from that of T. buffeli/orientalis and T. annulata. Sequence comparisons indicate that different T. sinensis isolates possess unique sizes of ITS1 and ITS2 as well as species-specific nucleotide sequences. This analysis provides new molecular data to support the classification of T. sinensis as a distinct species from other known Theileria spp. based on ITS sequences.

Theileriosis in a reindeer (Rangifer tarandus tarandus) associated with a potentially novel Theileria sp

A 5-year-old male neutered reindeer (Rangifer tarandus tarandus) from Missouri was presented with a 3-week history of anorexia, respiratory distress, lethargy, and weight loss. Blood smear review revealed that a small percentage of RBCs contained small (1-2 μm in length) pleomorphic piroplasms (signet ring, rod- or pear-shaped, and elongate forms) with an eccentric magenta nucleus and basophilic cytoplasm. Nested PCR to specifically amplify a portion of the piroplasm small subunit ribosomal RNA (SSU rRNA) gene was performed on DNA extracted from an EDTA specimen of whole blood. Subsequent sequence analyses showed similarity between the reindeer hemoparasite and Theileria spp SSU rRNA gene sequences in the GenBank database, with highest similarity to those of a Theileria sp in a White-tailed deer from North Texas (AY735132, AY735133). The reindeer and North Texas Theileria sp are genetically distinct from, albeit closely related to, the White-tailed deer Theileria sp (subsequently referred to as T cervi). To the authors' knowledge, this is the first identification of Theileria of this genotype in a reindeer. Historically, T tarandirangiferis infection was found with associated mortality in reindeer in Russia, but reports predate molecular characterization. Hence, the relationship of T tarandirangiferis with either T cervi or this agent remains unknown. T cervi is not typically pathogenic in White-tailed deer in the US unless the animal is immune-compromised by stress or disease; however, mortality from T cervi infection in reindeer has been reported.

Phylogenetic analysis of benign Theileria species based on major piroplasm surface protein (MPSP) genes from ticks of grazing cattle in Korea

Complete major piroplasm surface protein (MPSP) gene sequences of benign Theileria parasites were isolated from ticks of grazing cattle in Korea. A total of 556 tick samples were collected in five provinces: Chungbuk, Jeonbuk, Jeonnam, Gyeongbuk, and Jeju during 2010-2011. Fifteen samples from Chungbuk and Jeonnam were positive for the Theileria MPSP gene by PCR amplification using a specific primer set. A phylogenetic tree was constructed with the amplified gene sequences and 26 additional sequences published in GenBank. The benign Theileria parasites were classified into eight types, those isolated from Korean cattle ticks belonged to Types 1 (Ikeda), 2 (Chitose), 4, and 8. Types 2 and 4 were the most common types, with the rate of 40%, followed by Types 1 and 8 (with the rate of 13% and 7%, respectively). Nucleotide sequence identities of 23 theilerial MPSP sequences (15 MPSP gene sequences amplified and 8 sequences published) ranged from 67.3 to 99.8%. Multiple alignments of the deduced amino acid sequences also showed that each type was characterized by specific amino acids: 7 for Type 1, 9 for Type 2, 4 for Type 4, and 3 for Type 8.

Molecular phylogenetic analysis of Theileria species detected from Japanese serows (Capricornis crispus) in Iwate Prefecture, Japan

In the present study, we tried to detect DNA for ribosomal RNA genes of piroplasma parasites from the liver or blood of 43 Japanese serows (Capricornis crispus) in Iwate Prefecture of Japan by polymerase chain reaction. Approximately 500-bp amplicons were obtained in 35 (81.4%) of the 43 samples by amplification for V4 hyper-variable regions of the 18S rRNA gene, and the amplicons were considered to be DNA of Theileria species. The complete nucleotide sequences (1,700 or 1709 bp) of the 18S rRNA gene were determined in 20 samples and were divided into 5 genotypes that were phylogenetically separated into two different lineages showing a polyphyletic relation. The Theileria DNAs of the two different lineages were considered to be those of distinct species.

Emergence of new types of Theileria orientalis in Australian cattle and possible cause of theileriosis outbreaks

Theileria parasites cause a benign infection of cattle in parts of Australia where they are endemic, but have, in recent years, been suspected of being responsible for a number of outbreaks of disease in cattle near the coast of New South Wales. The objective of this study was to identify and characterize the species of Theileria in cattle on six farms in New South Wales where disease outbreaks have occurred, and compare with Theileria from three disease-free farms in Queensland that is endemic for Theileria. Special reference was made to sub-typing of T. orientalis by type-specific PCR and sequencing of the small subunit (SSU) rRNA gene, and sequence analysis of the gene encoding a polymorphic merozoite/piroplasm surface protein (MPSP) that may be under immune selection. Nucleotide sequencing of SSU rRNA and MPSP genes revealed the presence of four Theileria genotypes: T. orientalis (buffeli), T. orientalis (ikeda), T. orientalis (chitose) and T. orientalis type 4 (MPSP) or type C (SSU rRNA). The majority of animals showed mixed infections while a few showed single infection. When MPSP nucleotide sequences were translated into amino acids, base transition did not change amino acid composition of the protein product, suggesting possible silent polymorphism. The occurrence of ikeda and type 4 (type C) previously not reported to occur and silent mutation is thought to have enhanced parasite evasion of the host immune response causing the outbreak.

Nucleotide sequence heterogeneity in the small subunit ribosomal RNA gene within Theileria equi from horses in Sudan

This is a molecular epidemiological investigation on Theileria equi, a causative agent of equine piroplasmosis. Blood samples were collected from 127 horses from different geographical locations in Sudan. The small subunit of rRNA gene (18S; ~1,600 bp) was amplified from 20 positive field samples and subsequently subjected to direct sequencing and analysis to reveal possible strain differences and the presence of a novel species or genotypes. Sequences were compared with published sequences mainly from South African and Spanish isolates. Eleven distinct T. equi sequences within 18S rRNA gene were identified to have occurred, and three genotypes were lying within the three previously identified groups. Alignments demonstrated extensive sequence variation in the hypervariable region of the 18S rRNA gene and many SNPs within the Sudanese T. equi isolates.

Molecular phylogenetic studies on Theileria spp. isolates (China) based on small subunit ribosomal RNA gene sequences

Six Theileria spp. from cattle, buffalo and black goat were identified in the Hubei province of China. In order to study the taxonomic status of these parasites, phylogenetic analysis of 18S rRNA genes were carried out. The 18S rRNA genes from each isolate were amplified by the polymerase chain reaction and the approximate 1.75 kb products were cloned and sequenced. Phylogenetic analysis of these gene sequences revealed that the five parasites from buffalo and cattle belonged to the Theileria sergenti/buffeli/orientalis group. The parasite from the Chinese goat (Macheng-Hubei, DQ286802) was closely related to Theileria luwenshuni isolated from sheep in the north of China. This represent the first report on the use of molecular phylogeny to classify Theileria spp. obtained in the Hubei province, showing that Theileria spp. from ruminants found in Hubei province belongs to the benign group of Theileria spp.

Sequence heterogeneity in the 18S rRNA gene within Theileria equi and Babesia caballi from horses in South Africa

A molecular epidemiological survey of the protozoal parasites that cause equine piroplasmosis was conducted using samples collected from horses and zebra from different geographical locations in South Africa. A total of 488 samples were tested for the presence of Theileria equi and/or Babesia caballi using the reverse line blot hybridization assay. Ten percent of the samples hybridized to the Theileria/Babesia genus-specific probe and not to the B. caballi or T. equi species-specific probes, suggesting the presence of a novel species or genotype. The small subunit of rRNA gene (18S; approximately 1600bp) was amplified and sequenced from 33 of these 488 samples. Sequences were compared with published sequences from the public sequence databases. Twelve distinct T. equi and six B. caballi 18S rRNA sequences were identified. Alignments demonstrated extensive sequence variation in the V4 hypervariable region of the 18S rRNA gene within T. equi. Sequence variation was also found in B. caballi 18S rRNA genes, although there was less variation than observed for T. equi. Phylogenetic analysis based on 18S rRNA gene sequences revealed three T. equi clades and two B. caballi clades in South Africa. The extent of sequence heterogeneity detected within T. equi and B. caballi 18S rRNA genes was unexpected since concerted evolution is thought to maintain homogeneity within repeated gene families, including rRNA genes, in eukaryotes. The findings reported here show that careful examination of variants of the 18S rRNA gene of T. equi and B. caballi is required prior to the development of molecular diagnostic tests to detect these parasites in horses. Species-specific probes must be in designed in regions of the gene that are both conserved within and unique to each species.

Sequence polymorphism in the ribosomal DNA internal transcribed spacers differs among Theileria species

The genomic region spanning the two ribosomal RNA internal transcribed spacers (ITS1 and ITS2) and the 5.8S rRNA gene was cloned and sequenced from sixteen Theileria isolates. Each Theileria species possessed ITS1 and ITS2 of unique size(s) and species specific nucleotide sequences. Varying degrees of ITS1 and ITS2 intra- and inter-species sequence polymorphism were found among ruminant Theileria species. The spacers were most polymorphic in the agent of tropical theileriosis, Theileria annulata, and were more conserved in two benign species, Theileria buffeli and Theileria sergenti Chitose. Phylogenetic analysis of the rDNA ITS1-5.8S rRNA gene-ITS2 region clearly separated each taxon, placing them in three clusters. One held T. annulata, Theileria parva, and Theileria mutans, with the latter two most closely related. The second held T. sergenti Ikeda, T. sergenti Chitose, and T. buffeli, with the latter two most closely related. The third cluster held the Theileria ovis isolates.

New data on epizootiology and genetics of piroplasms based on sequences of small ribosomal subunit and cytochrome b genes

As a continuation of our studies on molecular epizootiology of piroplasmosis in Spain and other countries, we present in this contribution the finding of new hosts for some piroplasms, as well as information on their 18S rRNA gene sequences. Genetic data were complemented with sequences of apocytochrome b gene (whenever possible). The following conclusions were drawn from these molecular studies: Theileria annulata is capable of infecting dogs, since it was diagnosed in a symptomatic animal. According to cytochrome b sequences, isolates from cows and dog present slight differences. The same isolates showed, however, identical sequence in the 18S rRNA gene. This exemplifies well the usefulness of the mitochondrial gene for examining infra-specific variation. Babesia bovis is an occasional parasite of equines, since it was detected in two symptomatic horses. We found evidence of genetic polymorphism occurring in the 18S rRNA gene of Spanish T. equi-like and B. ovis isolates. B. bennetti from Spanish seagull is loosely related to B. ovis, and might represent a genetically distinct branch of babesids. A partial sequence of a cytochrome b pseudogene was obtained for the first time in Babesia canis rossi from South Africa. The pseudogene is distantly related to B. bigemina cytochrome b gene. These new findings confirm the ability of some piroplasms to infect multiple hosts, as well as the existence of a relatively wide genetic polymorphisms with respect to the cytochrome b gene. On the other hand, the existence of mtDNA-like pseudogenes of possible nuclear location in piroplasms is interesting due to their possible impact on molecular phylogeny studies.

Description of Babesia duncani n.sp. (Apicomplexa: Babesiidae) from humans and its differentiation from other piroplasms

The morphologic, ultrastructural and genotypic characteristics of Babesia duncani n.sp. are described based on the characterization of two isolates (WA1, CA5) obtained from infected human patients in Washington and California. The intraerythrocytic stages of the parasite are morphologically indistinguishable from Babesia microti, which is the most commonly identified cause of human babesiosis in the USA. Intraerythrocytic trophozoites of B. duncani n.sp. are round to oval, with some piriform, ring and ameboid forms. Division occurs by intraerythrocytic schizogony, which results in the formation of merozoites in tetrads (syn. Maltese cross or quadruplet forms). The ultrastructural features of trophozoites and merozoites are similar to those described for B. microti and Theileria spp. However, intralymphocytic schizont stages characteristic of Theileria spp. have not been observed in infected humans. In phylogenetic analyses based on sequence data for the complete18S ribosomal RNA gene, B. duncani n.sp. lies in a distinct clade that includes isolates from humans, dogs and wildlife in the western United States but separate from Babesia sensu stricto, Theileria spp. and B. microti. ITS2 sequence analysis of the B. duncani n.sp. isolates (WA1, CA5) show that they are phylogenetically indistinguishable from each other and from two other human B. duncani-type parasites (CA6, WA2 clone1) but distinct from other Babesia and Theileria species sequenced. This analysis provides robust molecular support that the B. duncani n.sp. isolates are monophyletic and the same species. The morphologic characteristics together with the phylogenetic analysis of two genetic loci support the assertion that B. duncani n.sp. is a distinct species from other known Babesia spp. for which morphologic and sequence information are available.

The risks of translocating wildlife. Pathogenic infection with Theileria sp. and Elaeophora elaphi in an imported red deer

It is well known that the translocation of wild animals poses risks of the introduction of pathogens into populations, and regulations and recommendations regarding quarantine and screening protocols for wild animals do exist. Less is known about the infection of imported animals with local endemic pathogens. A red deer stag that had been imported from Germany was found recumbent and died from hemolytic anaemia and a process of exertional myopathy. Infection with Theileria sp. was detected in thin blood smears and confirmed by PCR and sequencing. In addition, massive parasitation by Elaeophora elaphi, a parasite endemic to Iberian red deer, was detected. Sequence comparison between the 18S rRNA gene sequence determined that the Theileria strain involved in this case had a 99.7% identity with a Theileria sp. strain obtained from sika-deer, and 95.3% identity with T. cervi. Using sequence distance analysis, the strain from red deer grouped with isolates from Cervus spp. as opposed to isolates from Odocoileus spp. and bovines. Both detected parasites are of little pathogenicity to local red deer, but were pathogenic for the imported red deer from Northern Europe. This case demonstrates that local endemic pathogens may pose naive translocated animals at risk, and illustrates the need for thorough examination and planification of translocation protocols.

Phylogenetic analysis of Theileria sp. from sika deer, Cervus nippon, in Japan

The 18S rRNA genes of Theileria species detected in sika deer, Cervus nippon centralis in Yamaguchi and Cervus nippon yesoensis in Hokkaido, were analyzed. The percent identities of the nucleotide sequences of Theileria from Cervus nippon centralis and Cervus nippon yesoensis were more than 99%. The percent identities of the Theileria sp. from sika deer and Theileria sergenti, Theileria buffeli and Theileria cervi were 97, 96 and 95%, respectively. Phylogenetic analysis of the gene sequences also revealed that Theileria sp. detected from sika deer comprise a clade that is clearly distinct from the clade comprised of Theileria from cattle.

Molecular epidemiological survey of benign Theileria parasites of cattle in Japan: detection of a new type of major piroplasm surface protein gene

Benign Theileria species of cattle are found in most parts of the world. The major piroplasm surface protein (MPSP), a conserved protein in all Theileria species, has been used as a maker for epidemiological and phylogenetical studies of benign Theileria species. Parasites with Ikeda- or Chitose-type MPSP genes are dominant in Japan, but we report here mixed infection cases of Theileria parasites with an additional MPSP type parasite infecting cattle in Abashiri District, Hokkaido. The MPSP gene sequence found in the additional type was closely related to MPSP genes of Theileria parasites found in Southeast Asian countries, including Thailand (Narathiwat) and Indonesia (Java). Theileria parasites from the blood sample were also distinguishable from the Ikeda or Chitose type parasites by the small subunit (SSU) rRNA gene sequence analysis, and they are grouped into the SSU rRNA types C/D found in Korea, North America, and Spain. The present finding of mixed infections of cattle with three different types of Theileria makes epidemiological feature of bovine theileriosis in Japan more complex. We have designed a set of primers specific to this MPSP type in order to conduct further epidemiological study.

Phylogenetic analysis of Theileria species transmitted by Haemaphysalis qinghaiensis

The phylogenetic relationships between six isolates of Theileria spp. infective to small ruminants, and two isolates of Theileria spp. infective to yak, all transmitted by Haemaphysalis qinghaiensis, together with the Theileria orientalis/sergenti/buffeli group and T. sinensis, were analyzed using the 18S ssrRNA gene sequence. The target DNA segment was amplified by polymerase chain reaction (PCR). The PCR product was used either for direct sequencing or was ligated to the PCR II vector for sequencing. The length of the 18S ssrRNA gene of all Theileria spp. involved in this study was around 1,740 bp. Two phylogenetic trees were inferred based on the 18S ssrRNA gene sequence of the Chinese isolates only, and Chinese isolates and other species of Theileria available in GenBank. In the first tree, the Theileria sp. infective to yaks was found to be T. sinensis. The Theileria sp. infective to small ruminants was found to be composed of two separate species of Theileria. Theileria sp. from Qinghai, Madang, Ningxian and Lintan, which was identical to the unidentified Theileria sp. described previously, is designated Theileria sp (China 1). The Theileria sp. from Longde, Zhangjiachuan and Lintan, which has not been described previously, is designated Theileria sp. (China 2) in order to avoid confusion. In the second tree, Theileria sp. (China 1) was closely related to benign Theileria, such as T. buffeli and T. sergenti, while Theileria sp. (China 2) was separated from other Theileria spp. The results indicate that H. qinghaiensis transmit at least three species of Theileria, two which are infective to sheep and goats, but not yak and one which is infective to yaks and cattle, but not to sheep and goats.

Molecular studies on Babesia, Theileria and Hepatozoon in southern Europe. Part I. Epizootiological aspects

Molecular epizootiology of piroplasmids (Babesia spp., Theileria spp.) and Hepatozoon canis was studied in mammals from southern Europe (mainly from Spain, but also from Portugal and France). Partial amplification and sequencing of the 18s rRNA gene was used for molecular diagnosis. In some particular cases (B. ovis and B. bovis) the complete 18s rRNA gene was sequenced. Blood samples were taken from domestic animals showing clinical symptoms: 10 dogs, 10 horses, 10 cows, 9 sheep and 1 goat. In addition, DNA samples were isolated from blood of 12 healthy dogs and from spleen of 10 wild red foxes (Vulpes vulpes). The results of the survey were the following: Piroplasmid infections: Approximately from 50 to 70% of wild or domestic mammals (symptomatic) were infected. Piroplasmids detected in ruminants were:COW: B. bovis, T. annulata and Theileria sp. (type C). Sheep and goat: B. ovis. Piroplasmids present in canids were: Babesia canis vogeli, Babesia canis canis, Theileria annae and B. equi. The only piroplasmid found in asymptomatic dogs was B. equi. Piroplasmids found in horse were: B. equi and B. canis canis.H. canis infections in canids: H. canis was absent of domestic dog samples, whereas all foxes studied were infected by this protozoa. Genetic analysis showed that most of piroplasmid and Hepatozoon isolates from southern Europe matched unambigously with previously described species, as demonstrated by the high level sequence identity between them, usually between 99 and 100%. Minor differences, usually detected in hypervariable regions of 18s rRNA gene are probably due to strain variations or rare genetic polymorphisms. A possible exception was B. bovis, which shows a relatively lower degree of homology (94%) with regard to other B. bovis isolates from several countries. The same is true for B. ovis, that showed a 94% identity with regard to Babesia sp. from South African cow and a 92% with rapport to B. bovis from Portugal.

Theileria buffeli infection of a Michigan cow confirmed by small subunit ribosomal RNA gene analysis

Theileria buffeli, generally a benign parasite of cattle, has been reported in animals from Texas, Missouri and North Carolina. To date, there have been no reports of the parasite in cattle residing in northern portions of the US. An 8-year-old cow (Maine Anjou x Angus cross-bred) in Michigan presented with hemoglobinuria and a packed cell volume of 9. Blood films stained with Giemsa showed numerous intraerythrocytic parasites morphologically consistent with T. buffeli. The parasite was confirmed to be T. buffeli by SSU rRNA gene sequence analysis (SSU rRNA sequence, Type A). This represents the first report of this parasite in an animal in Michigan.

Babesia leo n. sp. from lions in the Kruger National Park, South Africa, and its relation to other small piroplasms

Babesia leo, a small piroplasm isolated from lions in South Africa is described as a distinct species based on a phylogenetic analysis of the 18S rRNA gene. Intraerythrocytic trophozoite and merozoite stages of B. leo are morphologically indistinguishable from other small piroplasms of felids. Previous studies showed that B. leo was biologically and antigenically distinct from B. felis, which is known to infect wild and domestic felids in South Africa. Molecular characterization showed strong support for the phylogenetic seperation of B. leo as a distinct species from B. felis and other felid piroplasms. Phylogenetic analysis also showed that Babesia microti and all of the felid piroplasms from Africa with known 18S rRNA gene sequences available, including B. leo, formed a single, separate clade, sister to the other babesial and theilerial piroplasm parasites.

Description and epidemiology of Theileria youngi n. sp. from a northern Californian dusky-footed woodrat (Neotoma Fuscipes) population

An epidemiologic study designed to identify the small mammal reservoir for the zoonotic WA1-type babesial parasite resulted in the discovery of a small, intraerythrocytic piroplasm in smeared blood from dusky-footed woodrats (Neotoma fuscipes) in northern California. The woodrat parasites were isolated and compared to other piroplasm parasites based on their morphology, antigenicity, and genetic characteristics. These studies indicated that the woodrat parasites were not the WA1-type babesial agent but were of the genus Theileria. We accordingly named it Theileria youngi. The prevalence in the woodrat population was high (61%). Infection was unrelated to gender or age of the woodrats. Potential vectors for this tick-transmitted parasite included 3 species of ticks recovered from the woodrats. Dermacentor occidentalis, Ixodes woodi, and Ixodes pacificus. Mostly larval or nymphal stages were recovered, suggesting transstadial transmission is possible. This is the first piroplasm fully characterized from a dusky-footed woodrat.

Molecular characterisation of the Theileria buffeli/orientalis group

Benign bovine Theileria parasites known as either Theileria buffeli, Theileria orientalis or Theileria sergenti are classified on basis of their morphology, vector specificity, pathogenicity and 18S small subunit ribosomal RNA or major piroplasm protein (MPSP) sequences. Since most isolates have been characterized on only some of these criteria and the existing confusion in nomenclature, an analysis was performed on eight different isolates to combine 18S rRNA data with MPSP data and the results were compared with available biological parameters. A polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) approach for both genes was used in combination with reverse line blot hybridisation for the 18S rRNA gene. Both MPSP and 18S rRNA genes were cloned and sequenced from parasites displaying aberrant MPSP RFLP profiles. Phylogeny based on published and determined 18S rRNA and MPSP sequences did correlate within the same isolate but there was no obvious correlation between molecular and biological data. Based on these findings, we suggest that the appropriate name for all these parasites is Theileria buffeli. A more specific nomenclature should be assigned when new molecular markers may become available.

Theileriosis in a Missouri beef herd caused by Theileria buffeli: case report, herd investigation, ultrastructure, phylogenetic analysis, and experimental transmission

A 6-year-old Simmental cow infected with Theileria buffeli had a clinical disease characterized by theilerial parasitemia, macrocytic normochromic anemia with acanthocytosis and spherocytosis, lymphoid hyperplasia (lymphocytosis, edematous lymphadenomegaly), dysproteinemia, evidence of liver disease, and a low serum antibody titer against T. buffeli. The cow was in a herd in which all cattle originated in Missouri; 22/75 (29%) of cattle had a theilerial parasitemia and 26/75 (35%) had titers to T. buffeli of > or =1:160. Classification of the Missouri bovine organism as T. buffeli was based on DNA sequencing and comparison to sequences for T. buffeli and Theileria sp. type A obtained from GenBank. Intraerythrocytic veils and piroplasms were seen during transmission electron microscopy. The organism was successfully transmitted to two splenectomized calves, which developed mild anemias while parasitemic. Blood from the second calf was used as the source of T. buffeli antigen for an indirect immunofluorescence antibody test. Theilerial isolates from a Missouri white-tailed deer were also sequenced and resembled Theileria sp. types F and G and were not consistent with the bovine organism.

Theileria sp. Infections associated with bovine fatalities in the United States confirmed by small-subunit rRNA gene analyses of blood and tick samples

Theileria sp.-specific small subunit (SSU) rRNA gene amplification confirmed the presence of the organism in cattle and in Amblyomma americanum and Dermacentor variabilis ticks collected from a cattle herd in Missouri. Blood from the index animal had type A and type D Theileria SSU rRNA genes. The type D gene was also found in blood from two cohort cattle and tick tissues. The type A SSU rRNA gene was previously reported from bovine Theileria isolates from Texas and North Carolina; the type D gene was reported from a Texas cow with theileriosis.

Molecular phylogenetic studies on Theileria parasites based on small subunit ribosomal RNA gene sequences

Classification of Theileria parasites of south-east Asian countries is still ambiguous due to the lack of basic studies, especially their molecular genetic information. In this study, we included 6 known species and 14 unclassified Theileria parasite isolates: Theileria annulata, Theileria parva, Theileria taurotragi, Theileria sergenti, Theileria buffeli, Theileria types Sable, Theileria types A, B, B1, B2, C, D, E, F, G, G1, Theileria type Medan (Indonesia), Theileria type Ipoh (Malaysia) and Theileria type Thong Song (Thailand). Small subunit ribosomal RNA (srRNA) nucleotide sequence data were collected by PCR, cloning and dideoxy sequencing. The srRNA nucleotide sequences were aligned and analyzed by distance methods, maximum parsimony algorithms and maximum likelihood methods to construct phylogenetic trees. Bootstrap analysis was used to test the strength of the different phylogenetic reconstructions. The data indicated that all of the tree-building methods gave very similar results. This study identified two groups of Theileria, the pathogenic and benign groups, which are strongly supported by bootstrap analysis. The analysis also indicated that three subgroups (A, B and C) were generated within the benign Theileria group whereas the classification of Theileria type D and Thong Song is questionable. However, more basic information such as life cycle differences, vectors, modes of transmission, virulent and genetic/sexual compatability is essential for clearer taxonomic definition of the benign Theileria parasites.

Simultaneous detection of bovine Theileria and Babesia species by reverse line blot hybridization

A reverse line blot (RLB) assay was developed for the identification of cattle carrying different species of Theileria and Babesia simultaneously. We included Theileria annulata, T. parva, T. mutans, T. taurotragi, and T. velifera in the assay, as well as parasites belonging to the T. sergenti-T. buffeli-T. orientalis group. The Babesia species included were Babesia bovis, B. bigemina, and B. divergens. The assay employs one set of primers for specific amplification of the rRNA gene V4 hypervariable regions of all Theileria and Babesia species. PCR products obtained from blood samples were hybridized to a membrane onto which nine species-specific oligonucleotides were covalently linked. Cross-reactions were not observed between any of the tested species. No DNA sequences from Bos taurus or other hemoparasites (Trypanosoma species, Cowdria ruminantium, Anaplasma marginale, and Ehrlichia species) were amplified. The sensitivity of the assay was determined at 0.000001% parasitemia, enabling detection of the carrier state of most parasites. Mixed DNAs from five different parasites were correctly identified. Moreover, blood samples from cattle experimentally infected with two different parasites reacted only with the corresponding species-specific oligonucleotides. Finally, RLB was used to screen blood samples collected from carrier cattle in two regions of Spain. T. annulata, T. orientalis, and B. bigemina were identified in these samples. In conclusion, the RLB is a versatile technique for simultaneous detection of all bovine tick-borne protozoan parasites. We recommend its use for integrated epidemiological monitoring of tick-borne disease, since RLB can also be used for screening ticks and can easily be expanded to include additional hemoparasite species.