Genetic diversity within Theileria orientalis parasites detected in Sri Lankan cattle

Genetic diversity and phylogeography of the global Theileria orientalis isolates inferred from MPSP gene sequences

BACKGROUND/OBJECTIVE

Theileria orientalis is a non-transforming Theileria species infecting cattle and water buffaloes. Several outbreaks of oriental theileriosis accompanied by considerable economic loss were documented in Asia, Australia, and New Zealand. The major piroplasm surface protein (MPSP) gene has frequently been used to molecularly characterize T. orientalis isolates worldwide. Various MPSP genotypes were detected with significant virulence variations. The present study provides the first in silico analysis for all globally published T. orientalis MPSP isolates to evaluate their phylogeny, diversity, and population structure.

METHODS

All studies that tested T. orientalis isolates using PCR-MPSP protocols were systematically collected from various databases. Theileria orientalis MPSP-sequenced isolates on the GenBank were collected and the sequences were tested for their phylogenetic relatedness, genetic diversity, recombination, natural selection, and population structure using various software.

RESULTS

The collected T. orientalis-MPSP isolates (n = 795) were clustered into 12 genotypes, including types 1 (Chitose), 2 (Ikeda), 3 (Buffeli), 4, 5, 7, 8, and N1-N5. The previously identified type 6 belonged to a separate species (Theileria sinensis). The previously identified type 9 was transferred to type 4. Two unidentified isolates from water buffaloes in India were clustered into a new suggested genotype "type N5". Of the 12 genotypes, Ikeda (type 2) is the most virulent in cattle. However, a few clinical cases have also been linked to types 1 (Chitose) and 7. In water buffaloes, T. orientalis outbreaks have been linked to genotypes N2 and N5. Geographic mapping of various genotypes revealed the dispersal of types 1 and 3 worldwide. Overall, the 795 isolates comprised 532 haplotypes and displayed very high nucleotide (π = 0.14) and haplotype (Hd = 0.995) diversities. As a result, a very low sequence conservation value (C = 0.207) was determined. The twelve genotypes displayed comparable haplotype diversities accompanied by statistically significant negative Tajima's D and Fu's Fs values suggesting population expansion. A high value for the minimum number of recombination events (Rm = 65) was estimated for the 795 isolates, and this value varied from 0 to 23 at the genotype level. Most types also displayed significant positive selection (dn/ds ratio > 1). This suggests that both recombination and positive selection occur in T. orientalis MPSP gene, which could explain the very high genetic diversity among various T. orientalis types. Different patterns were detected for the gene flow among T. orientalis populations from various hosts and geographies; however, there is evidence for the genetic relatedness between populations from neighbouring countries.

CONCLUSION

The high genetic polymorphism and different associated pathogenicity in T. orientalis-MPSP genotypes highlight the need for further investigations employing whole genome sequencing technology to provide accurate comparative gene-level analyses and help further understand their pathogenicity.

Molecular Detection of Hemoparasites in Hematophagous Insects Collected from Livestock Farms in Northeastern Thailand

Vector-borne parasitic diseases (VBPDs) are diseases that have a major impact on the health and productivity of livestock. VBPDs, including trypanosomosis, theileriosis, and anaplasmosis, are caused by blood parasites and Rickettsiales infections that can be transmitted by biting insects. The control and elimination of VBPDs is difficult and challenging. This study contributed to better understanding the impact of hematophagous insects on carrying pathogens to livestock by investigating the detection of Trypanosoma evansi, Theileria spp. and Anaplasma spp. in hematophagous insects collected from five livestock farms in Northeastern Thailand using polymerase chain reaction (PCR). The Stomoxys and Tabanus samples were collected using Nzi and Vavoua traps. Morphological and molecular identifications of hematophagous insects were performed. The Stomoxys samples were dissected into head and abdomen parts, while the Tabanus samples were dissected into head, salivary glands, and abdomen parts before DNA extraction individually. The host blood meal in the DNA of each part of the hematophagous insects was identified using PCR targeting the prepronociceptin (PNOC) gene. PCR detection of T. evansi, Theileria spp., and Anaplasma spp. were performed by targeting the ITS2, 18s rRNA, and msp4 genes, respectively. In total, 131 insect samples were collected, with Stomoxys calcitrans being the most common species at 40 (30.53%), followed by Tabanus spp. at 14 (10.69%) and the other Stomoxys spp. at 7 (5.34%), respectively. The hemoparasite detection results identified Theileria spp. in the abdomen (21.43%; 3/14) of three Tabanus samples. Neither Anaplasma spp. nor T. evansi were detected in this study. Additionally, host blood meal DNA was found in the abdomen of Stomoxys calcitrans (4.17%; 1/24) and Stomoxys spp. (20%; 1/5). For the Tabanus spp., host blood meal DNA was detected in the head (7.14%; 1/14), salivary glands (7.14%; 1/14), and abdomen (14.29%; 2/14). These results highlighted that Tabanus spp. might play an important role in Theileria transmission.

Detection of Theileria in cattle ticks (Rhipicephalus microplus) (Canestrini, 1888) in upper-northeastern Thailand

Theileria parasites were investigated from cattle ticks (Rhipicephalus microplus (Canestrini, 1888)) collected in 12 provinces in upper-northeastern Thailand based on the sequences of 18S rRNA and MPSP gene. Polymerase chain reactions (PCRs) and sequencing specific regions for the 18S rRNA gene revealed two species of Theileria pathogens; T. orientalis (n = 42) and T. sinensis (n = 31) with 94.50-100 % identity. In the provinces of upper-northeastern Thailand, the nucleotide diversity of Theileria's 18S rRNA for T. sinensis and T. orientalis were 0 % and 1.3 %. respectively. The MPSP gene was used to categorize the T. orientalis genotypes. The sequences were compared with those available in the public database (GenBank) for species identification. Phylogenetic trees of Theileria were constructed from the MPSP gene sequences of our amplicons and those available in GenBank using maximum-likelihood and neighbor-joining analyses. The results revealed three identified genotypes: type 3, 5, and 7. Although the main carriers of T. orientalis are ticks in the genus Haemaphysalis, T. orientalis was the most frequently found in R. microplus in upper-northeastern Thailand. Theileria was frequent in Nong Khai, Mukdahan, and Loei, three Thai provinces that bordered the Lao PDR close to the Mekong River. Epidemiological surveys and control strategies in this region should be considered.

First report of oriental theileriosis in the Intermediate Zone, Sri Lanka: Is Theileria orientalis type 7 always apathogenic?

PURPOSE

Theileriosis in cattle has a significant economic implication for dairy production globally. Thus, it is crucial to investigate the prevalence of bovine theileriosis, the causative agent and genotypes of Theileria species in dairy cattle in the Kurunegala District in the Intermediate zone, where the third largest population of dairy cattle in Sri Lanka is present and experienced a substantial reduction in the cattle population recently.

METHODS

Sixty blood samples and background data were collected from three dairy farms in Galpokuna (n = 20), Koulwewa (n = 20), and Andigama (n = 20) areas. Haematocrit was used to identify anaemia while Giemsa-stained blood smears demonstrated the presence of piroplasms. A Fisher's Exact Test (p < 0.05) compared the prevalence of infection among age groups and farms. PCRs using species-specific primers designed to amplify regions of MPSP and 18 s rRNA genes followed by sequencing of selected amplicons allowed phylogeny of the species detected.

RESULTS

All three farms had semi-intensive farming practices keeping animals in a 'closed' setup with limited movement. Theileriosis prevalence in dairy cattle was 55.0 % with no difference among the farms (Koulwewa: 65.0 %, Galpokuna: 50.0 %, Andigama: 50.0 %). One-third of the cattle (33.3 %) were anaemic based on haematocrit results but most showed mild anaemia. Anaemia was significantly higher in calves (45.0 %) than in adults (25.0 %; χ2 = 5.743; p = 0.03) tested positive for theileriosis. None of the animals showed any other signs of theileriosis. PCR revealed the presence of both T. orientalis (pathogenic or benign) and T. annulata (pathogenic). The sequencing data revealed that the T. orientalis genotype present in Kurunegala District is type 7.

CONCLUSION

This is the first report on T. orientalis and T. annulata in dairy cattle in the Intermediate zone of Sri Lanka. The type 7 of T. orientalis was more common showing severe anaemia in calves while mild anaemia or no anaemia in adults and sub-adults. In immunologically intact animals, the reported genotype of the parasite can persist asymptomatically for life, occasionally causing a relapse, particularly under stressful conditions like pregnancy, lactation, and rapid changes in environmental conditions. However, the susceptibility of calves for pathogenic and apathogenic genotypes of T. orientalis and the carrier status of asymptomatic animals needs further investigation.

Molecular epidemiology and genetic characterization of Theileria orientalis in cattle

Theileria orientalis (T. orientalis) is a benign species of Theileria that is found all throughout the world, including Egypt. The purpose of this work was to determine the current status of T. orientalis infection in cattle, as well as to define T. orientalis genetic diversity using the major piroplasm surface protein (MPSP) genes. In 2020, blood samples from 500 asymptomatic cattle were collected, which live in four different governorates at northern Egypt and examined using PCR assay based on MPSP gene. Overall, 44 blood samples (8.8%, 44/500) were positive for T. orientalis, and the highest prevalence rate was observed in Kafer ElSheikh while it was relatively low in Gharbia governorate. Moreover, based on multivariable analysis, the risk of infection with T. orientalis infection was higher in mixed breed cattle and in animals of age group more than 3 years compared to other. Additionally, absence of acaricide application, infestation with ticks, and communal grazing system were identified as potential risk factors for T. orientalis infection. Phylogenetic analysis revealed that the isolates studied belonged to two MPSP genotypes, types 1 and 2. These findings reveal that the MPSP genotypes discovered in the present work displayed genetic variation that was linked to geographic area. Therefore, further research should be focused on developing an effective T. orientalis monitoring and preventive program.

Epidemiological survey of Anaplasma marginale in cattle and buffalo in Sri Lanka

Bovine anaplasmosis caused by Anaplasma marginale represents a serious threat to cattle farming worldwide, especially in the tropics and subtropics. In the present study, archived DNA samples from the blood of cattle (n=437) in the Nuwara Eliya, Galle, Ampara, Polonnaruwa, and Jaffna districts and buffalo (n=327) in the Galle, Polonnaruwa, Mannar, and Mullaitivu districts in Sri Lanka, were screened for A. marginale using a major surface protein 5 (msp5) gene-based PCR assay. The findings showed that 32.7 and 57.5% of cattle and buffalo, respectively, were A. marginale-positive. The rate of positivity differed significantly among geographical regions. In conclusion, the high rates of A. marginale infection in cattle and buffalo highlight the importance of effective control measures in Sri Lanka.

First molecular survey of piroplasm species in cattle from Kyrgyzstan

Bovine piroplasmosis is a tick-borne disease caused by apicomplexan hemoparasites of the genera Theileria and Babesia. This study was carried out to assess the presence and frequency of piroplasm parasites in apparently healthy cattle in Kyrgyzstan. A total of 454 blood samples were collected from animals of various ages in eight villages located in the Chu valley and around the Lake Issyk Kul. The hypervariable V4 region of the 18S ribosomal RNA (rRNA) gene was amplified with a set of primers specific targeting members of the genera Theileria and Babesia. Amplified PCR products were hybridized onto a membrane to which generic and species-specific oligonucleotide probes were covalently linked. The results revealed the presence of three piroplasm species (Theileria orientalis, Babesia major, Theileria annulata). Theileria orientalis was the most prevalent species (32.8%; CI 28.5-37.3). Babesia major was the only species of Babesia found in any of the samples (1.3%; CI 0.5-2.8). The co-existence of Theileria annulata and T. orientalis was detected in nine animals (1.9%; CI 0.9-3.7). BLAST search revealed that the Theileria sequences shared 100% identity with the recently reported sequences for T. buffeli and T. annulata. The sequence of B. major was also 100% identical to an existing B. major sequence. This molecular survey provides important epidemiological data for control of bovine piroplasmosis caused by T. orientalis, B. major, and T. annulata in Kyrgyzstan.

Epidemiological survey of hemoprotozoan parasites in cattle from low-country wet zone in Sri Lanka

The diseases caused by hemoprotozoan parasites in cattle often result in economic losses. In Sri Lanka, previous studies found that the up-country wet zone, which is located in central Sri Lanka, was characterized by a high rate of Theileria orientalis and a low rate of Theileria annulata compared with the dry zone. In this study, DNA samples were prepared from the blood of 121 cattle in Galle, a coastal district located in low-country wet zone in Sri Lanka, and were PCR-screened for Babesia bovis, Babesia bigemina, T. annulata, T. orientalis, and Trypanosoma theileri. All the parasite species, except B. bovis, were detected among the surveyed cattle. The animals had a high rate of T. orientalis (100%) and a low rate of T. annulata (1.6%), as in the up-country wet zone. Babesia bigemina and Tr. theileri were detected in 19.0% and 20.6% of the animals, respectively, and their infection rates were higher in the animals reared in extensive management systems (32.8% and 27.9%, respectively) than in those managed in intensive/semi-intensive systems (5.0% and 13.3%, respectively). Genotypic analyses found that the T. orientalis mpsp type 5 was predominant similar to up-country wet zone, and that Tr. theileri consisted of seven catl genotypes, including two new genotypes (IL and IM) and four previously detected genotypes (IA, IB, II, and IK). These findings suggest that the hemoprotozoan infection profiles are largely conserved within the wet zone, despite differences in the geography, cattle breeds, and management practices between the up-country and low-country wet zones.

Genetic Analysis of Babesia Isolates from Cattle with Clinical Babesiosis in Sri Lanka

Bovine babesiosis is a serious threat to the cattle industry. We prepared blood DNA samples from 13 cattle with clinical babesiosis from the Badulla (n = 8), Jaffna (n = 3), and Kilinochchi (n = 2) districts in Sri Lanka. These DNA samples tested positive in PCR assays specific for Babesiabovis (n = 9), Babesia bigemina (n = 9), and Babesiaovata (n = 1). Twelve cattle were positive for B. bovis and/or B. bigemina One cow was negative for the tested Babesia species but was positive for Babesia on microscopic examination; the phylogenetic positions of 18S rRNA and cytochrome oxidase subunit III gene sequences suggested that the cow was infected with Babesia sp. Mymensingh, which was recently reported from a healthy cow in Bangladesh. We then developed a novel Babesia sp. Mymensingh-specific PCR assay and obtained positive results for one other sample. Analysis of gene sequences from the cow with positive B. ovata-specific PCR results demonstrated that the animal was infected not with B. ovata but with Babesia sp. Hue-1, which was recently reported from asymptomatic cattle in Vietnam. The virulence of Babesia sp. Hue-1 is unclear, as the cow was coinfected with B. bovis and B. bigemina However, Babesia sp. Mymensingh probably causes severe clinical babesiosis, as it was the sole Babesia species detected in a clinical case. The present study revealed the presence of two bovine Babesia species not previously reported in Sri Lanka, plus the first case of severe bovine babesiosis caused by a Babesia species other than B. bovis, B. bigemina, and Babesiadivergens.

Molecular characterisation of Theileria orientalis in imported and native bovines from Pakistan

The epidemiological aspects of Theileria orientalis in Pakistan are unknown; therefore, investigations using sensitive and precise molecular techniques are required. This study reports the first molecular characterisation of T. orientalis detected from imported (Bos taurus) and native cattle (Bos indicus×Bos taurus) and buffaloes (Bubalus bubalis) selected from four districts of Punjab, Pakistan. DNA samples from blood (n=246) were extracted and tested using conventional PCR utilising the major piroplasm surface protein (MPSP) gene and multiplexed tandem PCR (MT-PCR). Theileria orientalis DNA was detected (15%; 22/147) only in imported cattle by conventional PCR, whereas 24.5% (36/147), 6% (3/50) and 6.1% (3/49) of the imported cattle and native Pakistani cattle and buffaloes, respectively were test-positive for T. orientalis using MT-PCR. Using MT-PCR, the prevalence of T. orientalis was significantly higher (P<0.0001) in imported cattle compared to that of detected in native Pakistani bovines. The prevalence of T. orientalis and DNA copies of chitose and ikeda were significantly higher (P<0.05) in imported cattle than those detected in native Pakistani bovines. DNA sequencing of amplicons of the conventional PCR revealed the presence of buffeli, chitose and ikeda genotypes of T. orientalis. Phylogenetic analysis revealed that the MPSP sequences of buffeli, chitose and ikeda from imported cattle were closely related to those sequences reported previously from Australia and other regions. This study provides the first survey of T. orientalis infection in imported and native bovines in Pakistan, and highlights the need for future studies to understand the spread of transboundary animal diseases.

Molecular characterization of Theileria orientalis from cattle in Ethiopia

This study reports the first molecular characterization of Theileria orientalis in local breeds of cattle in Ethiopia. A conventional PCR utilizing major piroplasm surface protein (MPSP) gene and an established multiplexed tandem PCR (MT-PCR) were used to characterize T. orientalis and to assess the infection intensity, respectively. Of 232 blood samples tested, T. orientalis DNA was detected in only 2.2% of samples using conventional PCR; two genotypes buffeli (1.3%; 3/232) and type 5 (0.9%; 2/232) of T. orientalis were detected. Phylogenetic analysis revealed that the buffeli MPSP sequences from Ethiopia were closely related to those reported from Kenya, Sri Lanka and Myanmar, and type 5 sequences from Ethiopia grouped with those from Korea, Japan, Vietnam and Thailand. A higher number of samples (3.9%; 9/232) were test-positive by MT-PCR and four genotypes (buffeli, chitose, ikeda and type 5) of T. orientalis were detected. The average intensity of infections with genotypes buffeli (DNA copy numbers 11,056) and type 5 (7508) were significantly higher (P<0.0001) than the pathogenic genotype ikeda (61 DNA copies). This first insight into T. orientalis from cattle in Ethiopia using MPSP gene provides a basis for future studies of T. orientalis in various agroclimatic zones and of the impact of oriental theilerosis on cattle in this and other countries of Africa.

Investigation of the index case herd and identification of the genotypes of Theileria orientalis associated with outbreaks of bovine anaemia in New Zealand in 2012

CASE HISTORY AND CLINICAL FINDINGS

On 7 September 2012 the Ministry for Primary Industries was notified of a dairy cow with regenerative anaemia (haematocrit (HCT) 0.08 L/L) in a herd of 465 Jersey-Friesian cross cows (index case herd) in the Northland region of New Zealand. Organisms consistent with Theileria spp. were present in red blood cells on a blood smear. No other causes of anaemia were detected following examination of affected cows. Blood samples collected from 29 randomly selected cows on 26 September 2012 showed that 24 (83%) were anaemic (HCT≤0.24 L/L) and therefore fitted the case definition for bovine anaemia associated with Theileria orientalis infection.

LABORATORY FINDINGS

Using a T. orientalis type-specific PCR assay that targeted the single subunit rRNA gene, all of six animals tested were positive for T. orientalis type Ikeda. Blood samples collected from clinically affected cattle in 11 subsequent outbreaks from throughout the North Island showed that T. orientalis Ikeda type was a common finding, but mixed infections with Chitose type were also identified. In addition, using a PCR assay that targeted the major piroplasm surface gene, T. orientalis type 5 was detected in one cow from the Waikato region.

DIAGNOSIS

The presence of T. orientalis type Ikeda, as well as type 5, was confirmed in cattle from outbreaks of bovine anaemia in herds throughout the North Island of New Zealand.

CLINICAL RELEVANCE

Two new types of T. orientalis were identified in this investigation, that were associated with a sudden rise in cases of bovine anaemia. The body of evidence showed that the Ikeda type was implicated as the cause of disease observed in this epidemic.

Type-specific PCR assays for Babesia bovis msa-1 genotypes in Asia: Revisiting the genetic diversity in Sri Lanka, Mongolia, and Vietnam

Babesia bovis is the most virulent Babesia organism, resulting in a high mortality rate in cattle. The genetic diversity of B. bovis merozoite surface antigens (MSAs), such as MSA-1, MSA-2b, and MSA-2c, might be linked to altered immune profiles in the host animals. The present study aimed to develop type-specific PCR assays for Asian msa-1 genotypes, thereby re-analyzing the genetic diversity of msa-1 in Sri Lanka, Mongolia, and Vietnam. Specific primers were designed for nine Asian msa-1 genotypes, which had been detected based on the phylogeny constructed using msa-1 gene sequences retrieved from the GenBank database. Specificity of the type-specific PCR assays was confirmed using plasmids containing the inserts of msa-1 gene fragments that represent Asian genotypes. Furthermore, no amplicons were observed by these PCR assays when DNA samples of Babesia bigemina, Babesia ovata, Theileria annulata, Theileria orientalis, Trypanosoma evansi, Trypanosoma theileri, Anaplasma marginale, and Anaplasma bovis, and non-infected bovine blood were analyzed. In total, 109 B. bovis-positive blood DNA samples sourced from Sri Lanka (44 cattle), Mongolia (26 cattle), and Vietnam (23 cattle and 16 water buffaloes) were then screened by the type-specific PCR assays. The sequences derived from all of the PCR amplicons were phylogenetically analyzed. Out of 109 DNA samples, 23 (20 from cattle and 3 from water buffaloes) were positive for at least one genotype. In agreement with previous studies, five and four different genotypes were detected among the DNA samples from Sri Lanka and Vietnam, respectively. In contrast, four genotypes, including three novel genotypes, were detected from Mongolia. Five DNA samples were found to be co-infected with multiple genotypes. The sequences of the PCR amplicons clustered phylogenetically within the corresponding clades. These findings indicated that the type-specific PCR assays described herein are useful for the determination of genotypic diversity of the B. bovis msa-1 gene in Asia.

Molecular epidemiology of bovine Babesia spp. and Theileria orientalis parasites in beef cattle from northern and northeastern Thailand

Beef cattle production represents the largest cattle population in Thailand. Their productivity is constrained by tick-borne diseases such as babesiosis and theileriosis. In this study, we determined the prevalence of Babesia bigemina, Babesia bovis and Theileria orientalis using polymerase chain reaction (PCR). The genetic markers that were used for detection of the above parasites were sequenced to determine identities and similarity for Babesia spp. and genetic diversity of T. orientalis. Furthermore the risk factors for the occurrence of the above protozoan parasites in beef cattle from northern and northeastern parts of Thailand were assessed. A total of 329 blood samples were collected from beef cattle in 6 provinces. The study revealed that T. orientalis was the most prevalent (30.1%) parasite in beef cattle followed by B. bigemina (13.1%) and B. bovis (5.5%). Overall, 78.7% of the cattle screened were infected with at least one of the above parasites. Co-infection with Babesia spp. and T. orientalis was 30.1%. B. bigemina and T. orientalis were the most prevalent (15.1%) co-infection although triple infection with the three parasites was observed in 3.0% of the samples. Sequencing analysis revealed that B. bigemina RAP1 gene and B. bovis SBP2 gene were conserved among the parasites from different cattle samples. Phylogenetic analysis showed that the T. orientalis MPSP gene from parasites isolated from cattle in north and northeast Thailand was classified into types 5 and 7 as reported previously. Lack of tick control program was the universal risk factor of the occurrence of Babesia spp. and T. orientalis infection in beef cattle in northern and northeastern Thailand. We therefore recommend training of farmers on appropriate tick control strategies and further research on potential vectors for T. orientalis and elucidate the effect of co-infection with Babesia spp. on the pathogenicity of T. orientalis infection on beef in northern and northeastern Thailand.

Emergence of new genotype and diversity of Theileria orientalis parasites from bovines in India

Bovine theileriosis is a serious threat to livestock worldwide. Uncertainty around species prevalence, antigenic diversity and genotypes of strains make it difficult to assess the impact of this parasite and to provide necessary treatment. We aimed to characterize genotypic diversity, phylogeny and prevalence of Theileria orientalis parasites from the states of Telangana and Andhra Pradesh, India by collecting bovine blood samples from the major districts of the two states. Bioinformatic analysis identified antigenic diversity among the prevalent parasite strains using major piroplasm surface protein (MPSP) gene. Our study revealed a prevalence rate of 4.8% (n=41/862) of T. orientalis parasites in bovine animals and a new genotype of T. orientalis parasite which was not previously reported in India. The emergence of these new genotypes could be an explanation for the frequent outbreaks of bovine theileriosis. Further, whole genome sequencing of T. orientalis strains will help to elucidate the genetic factors relevant for transmissibility and virulence as well as vaccine and new drug development.

Development and validation of a quantitative PCR assay using multiplexed hydrolysis probes for detection and quantification of Theileria orientalis isolates and differentiation of clinically relevant subtypes

Theileria orientalis is an emerging pathogen of cattle in Asia, Australia, and New Zealand. This organism is a vector-borne hemoprotozoan that causes clinical disease characterized by anemia, abortion, and death, as well as persistent subclinical infections. Molecular methods of diagnosis are preferred due to their sensitivity and utility in differentiating between pathogenic and apathogenic genotypes. Conventional PCR (cPCR) assays for T. orientalis detection and typing are laborious and do not provide an estimate of parasite load. Current real-time PCR assays cannot differentiate between clinically relevant and benign genotypes or are only semiquantitative without a defined clinical threshold. Here, we developed and validated a hydrolysis probe quantitative PCR (qPCR) assay which universally detects and quantifies T. orientalis and identifies the clinically associated Ikeda and Chitose genotypes (UIC assay). Comparison of the UIC assay results with previously validated universal and genotype-specific cPCR results demonstrated that qPCR detects and differentiates T. orientalis with high sensitivity and specificiy. Comparison of quantitative results based on percent parasitemia, determined via blood film analysis and packed cell volume (PCV) revealed significant positive and negative correlations, respectively. One-way analysis of variance (ANOVA) indicated that blood samples from animals with clinical signs of disease contained statistically higher concentrations of T. orientalis DNA than animals with subclinical infections. We propose clinical thresholds to assist in classifying high-, moderate-, and low-level infections and describe how parasite load and the presence of the Ikeda and Chitose genotypes relate to disease.

Assessment of sequence variability in a p23 gene region within and among three genotypes of the Theileria orientalis complex from south-eastern Australia

Oriental theileriosis is a tick-borne, protozoan disease of cattle caused by one or more genotypes of Theileria orientalis complex. In this study, we assessed sequence variability in a region of the 23kDa piroplasm membrane protein (p23) gene within and among three T. orientalis genotypes (designated buffeli, chitose and ikeda) in south-eastern Australia. Genomic DNA (n=100) was extracted from blood of infected cattle from various locations endemic for oriental theileriosis and tested by polymerase chain reaction (PCR)-coupled mutation scanning (single-strand conformation polymorphism (SSCP)) and targeted sequencing analysis. Eight distinct sequences represented all DNA samples, and three genotypes were found: buffeli (n=3), chitose (3) and ikeda (2). Nucleotide pairwise comparisons among these eight sequences revealed considerably higher variability among the genotypes (6.6-11.7%) than within them (0-1.9%), indicating that the p23 gene region allows the accurate identification of T. orientalis genotypes. In the future, we will combine this gene with other molecular markers to study the genetic structure of T. orientalis populations in Australasia, which will pave the way to establish a highly sensitive and specific PCR-based assay for genotypic diagnosis of infection and for assessing levels of parasitaemia in cattle.

An epidemiological survey of bovine Babesia and Theileria parasites in cattle, buffaloes, and sheep in Egypt

Cattle, buffaloes, and sheep are the main sources of meat and milk in Egypt, but their productivity is thought to be greatly reduced by hemoprotozoan parasitic diseases. In this study, we analyzed the infection rates of Babesia bovis, Babesia bigemina, Theileria annulata, and Theileria orientalis, using parasite-specific PCR assays in blood-DNA samples sourced from cattle (n=439), buffaloes (n=50), and sheep (n=105) reared in Menoufia, Behera, Giza, and Sohag provinces of Egypt. In cattle, the positive rates of B. bovis, B. bigemina, T. annulata, and T. orientalis were 3.18%, 7.97%, 9.56%, and 0.68%, respectively. On the other hand, B. bovis and T. orientalis were the only parasites detected in buffaloes and each of these parasites was only found in two individual DNA samples (both 2%), while one (0.95%) and two (1.90%) of the sheep samples were positive for B. bovis and B. bigemina, respectively. Sequence analysis showed that the B. bovis Rhoptry Associated Protein-1 and the B. bigemina Apical Membrane Antigen-1 genes were highly conserved among the samples, with 99.3-100% and 95.3-100% sequence identity values, respectively. In contrast, the Egyptian T. annulata merozoite surface antigen-1 gene sequences were relatively diverse (87.8-100% identity values), dispersing themselves across several clades in the phylogenetic tree containing sequences from other countries. Additionally, the T. orientalis Major Piroplasm Surface Protein (MPSP) gene sequences were classified as types 1 and 2. This is the first report of T. orientalis in Egypt, and of type 2 MPSP in buffaloes. Detection of MPSP type 2, which is considered a relatively virulent genotype, suggests that T. orientalis infection may have veterinary and economic significance in Egypt. In conclusion, the present study, which analyzed multiple species of Babesia and Theileria parasites in different livestock animals, may shed an additional light on the epidemiology of hemoprotozoan parasites in Egypt.

Evolution and genetic diversity of Theileria

Theileria parasites infect a wide range of domestic and wild ruminants worldwide, causing diseases with varying degrees of severity. A broad classification, based on the parasite's ability to transform the leukocytes of host animals, divides Theileria into two groups, consisting of transforming and non-transforming species. The evolution of transforming Theileria has been accompanied by drastic changes in its genetic makeup, such as acquisition or expansion of gene families, which are thought to play critical roles in the transformation of host cells. Genetic variation among Theileria parasites is sometimes linked with host specificity and virulence in the parasites. Immunity against Theileria parasites primarily involves cell-mediated immune responses in the host. Immunodominance and major histocompatibility complex class I phenotype-specificity result in a host immunity that is tightly focused and strain-specific. Immune escape in Theileria is facilitated by genetic diversity in its antigenic determinants, which potentially results in a loss of T cell receptor recognition in its host. In the recent past, several reviews have focused on genetic diversity in the transforming species, Theileriaparva and Theileriaannulata. In contrast, genetic diversity in Theileriaorientalis, a benign non-transforming parasite, which occasionally causes disease outbreaks in cattle, has not been extensively examined. In this review, therefore, we provide an outline of the evolution of Theileria, which includes T. orientalis, and discuss the possible mechanisms generating genetic diversity among parasite populations. Additionally, we discuss the potential implications of a genetically diverse parasite population in the context of Theileria vaccine development.

Molecular prevalence and genetic diversity of bovine Theileria orientalis in Myanmar

Theileria orientalis is a causative agent of benign theileriosis in cattle and distributed in mainly Asian countries. In the present study, we examined the prevalence of T. orientalis infection by PCR based on the major piroplasm surface protein gene (MPSP) sequences in cattle in Myanmar, followed by phylogenetic analysis of the MPSP genes. The MPSP gene was amplified in 258 of 713 (36.2%) cattle blood DNA samples collected from five cities in different geographical regions of Myanmar. Phylogenetic analysis of MPSP sequences from 54 T. orientalis-positive DNA samples revealed the presence of six allelic genotypes, including Types 1, 3, 4, 5, 7, and N-3. Types 5 and 7 were the predominant types detected. Sequences of the MPSP genes detected in Myanmar were closely related to those from Thailand, Vietnam or Mongolia. These findings suggest that movement of animals carrying T. orientalis parasites between Southeast Asian countries could be a reason for the similar genotype distribution of the parasites in Myanmar.

Theileria infection in domestic ruminants in northern Ethiopia

Piroplasmosis caused by different tick-borne hemoprotozoan parasites of the genera Theileria and Babesia is among the most economically important infections of domestic ruminants in sub-Saharan Africa. A survey for piroplasm infection was conducted in three locations in Northern Ethiopia. Of 525 domestic ruminants surveyed, 80% of the cattle, 94% of the sheep and 2% of the goats were positive for different Theileria spp. based on PCR of blood followed by DNA sequencing. Sheep had a significantly higher rate of infection compared with cattle (P<0.0003) and both sheep and cattle had higher rates of infection compared to goats (P<0.0001). Four species of Theileria were detected in cattle: T. velifera, T. mutans, T. orientalis complex and T. annulata with infection rates of 66, 8, 4, and 2%, respectively. This is the first report of T. annulata, the cause of Tropical Theileriosis in Ethiopia. Of the two Theileria spp. detected in small ruminants, T. ovis was highly prevalent (92%) in sheep and rare in goats (1.5%) whereas T. seperata was infrequent in sheep (2%) and rare in goats (0.4%). None of the animals were positive for Babesia spp.; however, Sarcocystis capracanis and S. tenella were detected in one goat and a sheep, respectively. The widespread distribution of Theileria spp. among cattle in northern Ethiopia including the virulent T. annulata and more mildly pathogenic T. mutans and T. orientalis, and the high infection rate in sheep with the usually sub-clinical T. ovis indicate extensive exposure to ticks and transmission of piroplasms with an important economic impact.