Theileria sergenti and T. buffeli: polymerase chain reaction-based marker system for differentiating the parasite species from infected cattle blood and infected tick salivary gland

Identification, molecular characterization and risk factors of Theileria infection among sheep: a first comprehensive report from North India

The present study was aimed at the identification, molecular characterization, and risk factor assessment of Theileria infection among sheep of Haryana province, north India. A total of 402 blood samples were collected from three different climatic zones of Haryana from March 2020 to September 2021. Light microscopy of blood smears revealed Theileria spp. infection in 47.26% (n = 190), while 60.94% (n = 245) of blood samples were positive using nested PCR. Extensive molecular characterization of Theileria infection using four pairs of species-specific primers indicated the dominance of T. ovis (29.1%) followed by T. lestoquardi (12.69%), T. luwenshuni (5.97%) and T. annulata (1.49%). Mixed infection was detected in 11.69% of cases. Bidirectional sequencing and phylogeny further confirmed the presence of these four Theileria spp. in the investigated area under study. Hematology indicated a significant (p < 0.01) reduction in various haematological indices of animals infected with T. luwenshuni and T. lestoquardi compared to the healthy control group. Risk factors like age, sex, and zone were significantly associated with Theileria infection in sheep. The present investigation depicts the first comprehensive molecular report of ovine Theileria spp., which warrants further study to develop suitable control strategies against these haemoparasitic infections.

Molecular Detection and Differentiation of Different Theileria Species in Naturally Infected Goats Using Nested PCR-RFLP: A First Report from Northern India

PURPOSE

Theileriosis is an economically important tick-borne pathogen with a serious impact on livestock health and productivity. Despite the fact that bovine theileriosis has been widely investigated, there exists a paucity of information on these infections in small ruminants, especially in India. The present study was carried out to detect and differentiate different Theileria spp. in goats using nested PCR RFLP.

METHODS

Blood samples and ticks were collected from 405 goats in various agro-climatic zones of Haryana state, India. The blood samples were screened by microscopy, nested PCR-RFLP, and sequence analysis. The nested PCR-RFLP was performed with four restriction enzymes viz., Hpa II, Bsh 1285I, Hae II and Rsa I. Six nested PCR amplicons with different RFLP patterns were sequenced and submitted to NCBI (OM666861, MZ220430, OM666628, MZ220437, OM666637, OM721806).

RESULTS

Microscopy revealed 18.27% (n = 74) infection with Theileria spp., while 33.58% (n = 136) of blood samples were confirmed positive by nested PCR. Out of 136 positive samples, 43.38% (n = 59), 11.02% (n = 15) and 20.58% (n = 28), were positive for T. ovis, T. lestoquardi and T. luwenshuni (Theileria sp. China 1), respectively. Mixed infection was detected in 25% (n = 34) cases. Based upon Hpa II digestion pattern, 13 samples with T. lestoquardi and T. ovis, and 21 samples with T. ovis and T. luwenshuni were detected. Sequence study further confirmed their identity. The majority of ticks collected from goats were identified as Rhipicephalus spp., Hyalomma anatolicum and Hemaphysalis spp.

CONCLUSION

This study represents the first confirmed molecular report of goats infected with T. ovis, T. lestoquardi, and T. luwenshuni from northern India.

Approaches to Integrated Parasite Management (IPM) for Theileria orientalis with an Emphasis on Immunity

Integrated parasite management (IPM) for pests, pathogens and parasites involves reducing or breaking transmission to reduce the impact of infection or infestation. For Theileria orientalis, the critical impact of infection is the first wave of parasitaemia from the virulent genotypes, Ikeda and Chitose, associated with the sequelae from the development of anaemia. Therefore, current control measures for T. orientalis advocate excluding the movement of naïve stock from non-endemic regions into infected areas and controlling the tick Haemaphysalislongicornis, the final host. In Australia, treatment of established infection is limited to supportive therapy. To update and expand these options, this review examines progress towards prevention and therapy for T. orientalis, which are key elements for inclusion in IPM measures to control this parasite.

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.

Analysis of Theileria orientalis draft genome sequences reveals potential species-level divergence of the Ikeda, Chitose and Buffeli genotypes

BACKGROUND

Theileria orientalis (Apicomplexa: Piroplasmida) has caused clinical disease in cattle of Eastern Asia for many years and its recent rapid spread throughout Australian and New Zealand herds has caused substantial economic losses to production through cattle deaths, late term abortion and morbidity. Disease outbreaks have been linked to the detection of a pathogenic genotype of T. orientalis, genotype Ikeda, which is also responsible for disease outbreaks in Asia. Here, we sequenced and compared the draft genomes of one pathogenic (Ikeda) and two apathogenic (Chitose, Buffeli) isolates of T. orientalis sourced from Australian herds.

RESULTS

Using de novo assembled sequences and a single nucleotide variant (SNV) analysis pipeline, we found extensive genetic divergence between the T. orientalis genotypes. A genome-wide phylogeny reconstructed to address continued confusion over nomenclature of this species displayed concordance with prior phylogenetic studies based on the major piroplasm surface protein (MPSP) gene. However, average nucleotide identity (ANI) values revealed that the divergence between isolates is comparable to that observed between other theilerias which represent distinct species. Analysis of SNVs revealed putative recombination between the Chitose and Buffeli genotypes and also between Australian and Japanese Ikeda isolates. Finally, to inform future vaccine studies, dN/dS ratios and surface location predictions were analysed. Six predicted surface protein targets were confirmed to be expressed during the piroplasm phase of the parasite by mass spectrometry.

CONCLUSIONS

We used whole genome sequencing to demonstrate that the T. orientalis Ikeda, Chitose and Buffeli variants show substantial genetic divergence. Our data indicates that future researchers could potentially consider disease-associated Ikeda and closely related genotypes as a separate species from non-pathogenic Chitose and Buffeli.

Theileria orientalis: a review

Theileria orientalis (also known historically as T. sergenti and T. buffeli) is responsible for benign or non-transforming theileriosis, and exerts its major effect through erythrocyte destruction. The life cycle of T. orientalis is essentially similar to that of other Theileria species, except that the schizonts do not induce transformation and fatal lymphoproliferation. The pathogenesis of anaemia as a result of infection is not clearly established and may be multifaceted. Clinical signs of weakness, reluctance to walk and abortion are early but non-specific indications of disease, particularly if accompanied by a history of cattle being moved. Physical examination may reveal pallor (pale eyes, vaginal mucosa), pyrexia, and elevated heart and respiratory rates. T. orientalis is an economically important parasite of cattle in New Zealand, Australia and Japan, especially where naïve animals are introduced into an endemic area or in animals under stress. Increased awareness of the risks posed by the parasite is required to enable management practices to be implemented to minimise its impact.

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.

An outbreak of haemolytic anaemia associated with infection of Theileria orientalis in naive cattle

CASE HISTORY

An outbreak of haemolytic anaemia occurred when 87 cattle were introduced from a presumed non-infected herd from south Otago to a herd in Northland (n=580 cows), New Zealand, where theileriosis is endemic.

CLINICAL FINDINGS

Clinical signs associated with Theileria spp. infection included lethargy, anorexia, inappetance, pale mucous membranes, and varying severity of anaemia. In the naive imported cattle, 11/29 (38%) of those tested showed haematological signs of anaemia (haematocrit (HCT) <0.25 L/L). A negative association was present between the HCT and the number of Theileria spp. organisms counted using light microscopy (correlation coefficient=-0.4; p<0.05). Haemoparasites consistent with Theileria spp. were observed on examination of a blood smear. Theileria orientalis group (Theileria buffeli/orientalis) species was confirmed using PCR and DNA sequencing, and other causes for anaemia were excluded in the most clinically severely affected cow. The 18S sequence data and phylogenetic analysis of the CoxIII sequences showed samples had the greatest similarity to T. orientalis Chitose from Japan.

DIAGNOSIS

Haemolytic anaemia associated with infection of T. orientalis.

CLINICAL RELEVANCE

Previous reports have suggested that T. orientalis group species may be non-pathogenic in healthy cattle, and an incidental finding in blood samples. However, this investigation provided evidence that in New Zealand, this pathogen is capable of causing clinical disease in cattle not necessarily debilitated by another disease. The potential for disease should be considered when naive cattle are brought in from non-endemic to endemic regions, for instance cattle from the South Island moved to regions where the vector for T. orientalis group species, Haemaphysalis longicornis, is active, and T. orientalis is present.

Detection and differentiation of Theileria luwenshuni and T. uilenbergi infection in small ruminants by PCR

Theileria luwenshuni and T. uilenbergi are newly identified Theileria species highly pathogenic for sheep and goats in China. As they are morphologically indistinguishable and poorly characterized, there is no easily applicable method available to differentiate between these species. In the present study, PCR assays are described for the differentiation and detection of T. luwenshuni and T. uilenbergi using species-specific primers, which were designed based on the hypervariable region of the small subunit ribosomal RNA gene sequences. By testing 100 field blood samples of sheep collected from five geographically different regions where the Theileria species were described to be prevalent, the PCR assays not only detected infected samples but also identified mixed infection. This suggests that these PCR assays are useful tools for the detection of and differentiation between T. luwenshuni and T. uilenbergi.

Characterisation of the 33kDa piroplasm surface antigen of Theileria orientalis/sergenti/buffeli isolates from West Java, Indonesia

The immunodominant 33/35kDa antigen of a Theileria isolate from West Java, Indonesia, was characterised and immuno-affinity purified by use of a monoclonal antibody, KUL-a4, and was shown to be representative of the T. orientalis/sergenti/buffeli group. The aminoterminal sequence of the purified 35kDa peptide (20 residues) was determined by automated Edman degradation and found to correspond to the predicted amino acid sequence of a prospective p33 gene previously sequenced from the same isolate. The cleavage site of a putative signal peptide was identified and conforms the (-3, -1) rule for signal peptidases. The existence of dimeric and trimeric forms of the p33/35 antigen is hypothesised from Western blot profiles. KUL-a4 appeared specific for the T. orientalis/sergenti/buffeli group. It did not recognise in indirect fluorescence antibody test (IFAT), intraerythrocytic bodies of Anaplasma marginale or piroplasms and schizonts of T. mutans, T. parva and T. annulata, whereas cattle antisera raised to these species showed cross-reactivity in IFAT. It however, appeared weakly cross-reactive in Western blot and ELISA, with the 34kDa piroplasm antigen of one T. annulata (Gharb) isolate. The present study indicates that the isolated antigen belongs to the p33/34 antigen family described within the T. sergenti/orientalis/buffeli group, and documents the group-specificity of one of its epitopes.

Molecular evidence of Babesia caballi (Nuttall and Strickland, 1910) parasite transmission from experimentally-infected SCID mice to the ixodid tick, Haemaphysalis longicornis (Neuman, 1901)

Molecular evidence that suggests the possible role of the ixodid tick, Haemaphysalis longicornis and its eggs in the transmission of equine Babesia caballi parasites is presented herein. Using polymerase chain reaction (PCR) to assay for DNA in parasites, presumably acquired by ticks that were allowed to feed on splenectomized-SCID mice, experimentally exposed to in vitro-cultivated B. caballi, we have obtained positive bands that corresponded to the expected B. caballi-specific 430bp gene fragment in 50% of female ticks used, and in 75 and 25% of eggs and larval progeny, respectively. Also, parasite DNA was detected in ticks, eggs and larvae as late as the 16th to the 20th day post-host infestation. Present findings support to the potential role of H. longicornis in the transmission of B. caballi parasites. Its capability, however, to successfully transmit the infection to horses under natural conditions in the field needs to be further ascertained. To our knowledge, this is the first documented study incriminating H. longicornis as a most and likely biological vector of equine babesias.

Expression of major piroplasm protein (p33) of Theileria sergenti (Korean isolate) and its immunogenicity in guinea pigs

To investigate the development of a subunit vaccine against theileriosis in cattle, the DNA fragments encoding piroplasm surface protein (p33) of Theileria sergenti of a Korean isolate were expressed in baculoviruses. The expressed p33 was characterized by indirect fluorescent antibody (IFA) and western blotting analysis. The expression of p33 was mainly detected on the surface of infected Sf21 cells by IFA. The immunoblotting analysis revealed the presence of a same molecular weight protein band of p33. The antigenicity of expressed polypeptide was further examined through the inoculation of a guinea pig. The sera of guinea pigs immunized with p33 expressed cell lysate showed similar fluorescent antibody patterns and reacted with the same molecular weight protein of T. sergenti in immunoblotting analysis, thus indicating that this protein can be a promising candidate for a subunit vaccine in the future.

PCR amplification and sequence of the p33 piroplasm surface antigen gene of a Theileria species isolated from cattle in west Java, Indonesia

Oriental theileriosis, a parasitic disease of cattle caused by protozoa of the Theileria orientalis/sergenti/buffeli group, has been reported in Indonesia but its causal agent had not yet been characterized. This study was carried out to isolate and characterize the parasite through comparison of its p33 piroplasm surface antigen gene sequence, with known p32 sequences of T. sergenti and T. buffeli isolates. A Theileria spp. isolate was collected from an Ongole cow in Jonggol, West-Java, and transferred into a splenectomized calf for antigen production. Piroplasms were extracted from erythrocytes by ammonium chloride-lysis, separated from unlysed leukocytes and parasitic DNA was phenol-extracted. Polymerase chain reaction (PCR) was carried out on genomic DNA with a pair of 20 bp primers showing consensus for the p32-35 nucleotide sequence of 7 known T. orientalis/sergenti/buffeli isolates. An 875 bp fragment was amplified, and further sequenced on both strands by the dye-labeled terminators method. It showed an 88% homology with the p33 nucleotide sequence of the Japanese T. sergenti Ikeda stock and a lesser homology with 6 other sequences of Australian T. buffeli or Japanese T. sergenti stocks. It was shown to share the presence of the Pst 1 and the absence of the HindIII restriction sites of the T. sergenti Ikeda stock and of one Australian T. buffeli stock, respectively. In conclusion, the affiliation to and the relative position of this Indonesian isolate within the T. orientalis/sergenti/buffeli group has been elucidated.

Identical small subunit ribosomal RNA gene nucleotide sequence of bovine Theileria isolates (Korea and Japan) and Theileria buffeli (Marula, Kenya)

Small subunit ribosomal RNA (SSU rRNA) gene nucleotide sequences of bovine Theileria isolates from Korea (KLS and KCB) and Japan (JHS) were determined. The genes from each isolate were amplified by the polymerase chain reaction and the approximately 1.8 kb product cloned and sequenced by a modified dideoxynucleotide method. Overlapping gene segments produced with a series of primers were sequenced, resulting in a complete DNA sequence for both forward and reverse strands of the SSU rRNA genes of each isolate. SSU rRNA gene sequences (termed Type A) were identical among the bovine Theileria isolates from Korea and the isolate from Japan. A GenBank data library homology search showed the sequence to be the same as that listed as Theileria buffeli isolated from cattle in Marula, Kenya.

A polymorphism observed in the experimentally successful peptide vaccine sequence derived from Theileria sergenti piroplasm major surface antigen (p33)

A polymorphism in the experimentally successful peptide vaccine sequence (EVVWKEKKEVKDLDA, amino acids 134-148) derived from the 33 kDa piroplasm major surface antigen (p33) of Theileria sergenti was examined. The vaccine sequences obtained by PCR amplification and sequencing of the p33 gene from a total of 15 parasite-infected cattle blood samples collected from 4 prefectures through Hokkaido to Kumamoto revealed the two major sequences (Ikeda and Chitose stock types) either of which was identified in all samples. Since the peptide vaccine develops the parasite species- or stock-specific immunity in the animals, an application of the two major peptide sequences as cocktailed vaccine should be evaluated for a practical use of this strategy to controlling T. sergenti infection in Japan.

[Rapid detection of Theileria sergenti by polymerase chain reaction]

Four separate pairs of oligonucleotide primers within the coding region in a T. sergenti 33-kDa surface protein gene were selected to detect T. sergenti by PCR. The specificity of PCR-amplified DNA was examined by digestion with restriction enzyme and Southern blot hybridization using T. sergenti p33 DNA probe. PCR appears to be specific for T. sergenti, without detectable signals from uninfected erythrocytes, uninfected bovine leukocytes and other hemoparasites, including A. marginale and B. ovata. Although 46 of 71 specimens (64.8%) from grazing cattle were microscopically positive, PCR in this study showed that 64 specimens (88.7%) were positive. Therefore, PCR proves a useful diagnostic tool for detecting T. sergenti-infected cattle. In addition, it is also revealed that PCR was significantly more sensitive than traditional microscopic examination using Giemsa's stain.