Molecular evidence for piroplasms in wild Reeves' muntjac (Muntiacus reevesi) in China

Molecular Characterization of Tick-borne Pathogens in Bactrian Camels and Ticks from Gansu Province, China

PURPOSE

Ticks are dangerous ectoparasites for humans and other animals, and tick-borne pathogens of Bactrian camels have been epidemiologically surveyed in Gansu Province, China. We aimed to determine the current distribution of tick-borne pathogens among Bactrian camels in Gansu during August 2013 using molecular tools.

METHODS

All ticks underwent morphological identification. We extracted DNA from the blood samples and ticks, screened them for Theileria, Babesia, Anaplasma, and Ehrlichia using standard or nested PCR with specific primers.

RESULTS

All ticks collected from the skin were identified as Hyalomma asiaticum. The blood and tick samples harbored similar pathogens, including the Theileria species, T. annulata, T. luwenshuni, T. uilenbergi, and T. capreoli, the Anaplasma species A. bovis and uncultured Anaplasma, the Ehrlichia species E. canis and uncultured Ehrlichia, and a new haplotype of Babesia species.

CONCLUSION

Our findings of anaplasmataceae and piroplasmida in Bactrian camels in Gansu provide a theoretical basis for deeper investigation into the epidemiology of tick-borne pathogens in these camels.

Analysis of genetic diversity and population structure of Babesia gibsoni

Babesia gibsoni is a tick-borne apicomplexan protozoan causing canine babesiosis. This parasite has diploid sexual reproduction in ticks, during which genetic exchanges can occur leading to increased genetic diversity, which is an important factor in adapting to environmental changes. Exploring the genetic variation of B. gibsoni population can provide a foundation for understanding the patterns of disease transmission and developing babesiosis control strategies. Partial 18S rRNA fragment sequences were obtained from 11 B. gibsoni isolates collected from different regions in China and 117 publicly available sequences were from 12 geographical areas including China. The genetic variation, demographic expansion and population structure were examined. A total of 34 haplotypes were identified among B. gibsoni populations. Analysis of molecular variance, pairwise Fst and structure analysis showed that high genetic variation within populations, low genetic differentiation and obvious mixture haplotype were apparent in a single continent, but higher genetic differentiation was detected across different continents. Neutrality tests implied that B. gibsoni populations had experienced population extension. These findings will contribute to understand the genetics and evolution of B. gibsoni and will be useful for formulating effective management strategies to prevent and control this parasite.

First Report of Babesia gibsoni in Cats in China

As there are few studies of Babesia spp. infection in cats in China, or anywhere in the world, the aim of this study was to explore the epidemic features of babesiosis in pet cats in China. In total, 429 blood samples were randomly collected in four different geographical regions. The 18S rRNA gene fragment of Babesia spp. was amplified by nest polymerase chain reaction (PCR), and haplotype and phylogenetic analysis of Babesia were performed to analyze the relationship of this protozoa. The total positive rate of infection was 2.8%. BLAST analysis indicated that Babesia gibsoni was detected in 12 cats. Among these, 4.3%, 3.1%, 0.8% and 2.0% were from Chongqing, Fujian, Hubei and Shandong, respectively. Haplotype and phylogenetic analysis showed that there were nine haplotypes and no obvious genetic variation among B. gibsoni populations. This is the first report of B. gibsoni in cats in China. These findings will be helpful for understanding the epidemiology of Babesia spp. in China, and provide a foundation for developing effective preventative strategies.

Systematic Comparison of the Performances of De Novo Genome Assemblers for Oxford Nanopore Technology Reads From Piroplasm

Background

Emerging long reads sequencing technology has greatly changed the landscape of whole-genome sequencing, enabling scientists to contribute to decoding the genetic information of non-model species. The sequences generated by PacBio or Oxford Nanopore Technology (ONT) be assembled de novo before further analyses. Some genome de novo assemblers have been developed to assemble long reads generated by ONT. The performance of these assemblers has not been completely investigated. However, genome assembly is still a challenging task.

Methods and Results

We systematically evaluated the performance of nine de novo assemblers for ONT on different coverage depth datasets. Several metrics were measured to determine the performance of these tools, including N50 length, sequence coverage, runtime, easy operation, accuracy of genome and genomic completeness in varying depths of coverage. Based on the results of our assessments, the performances of these tools are summarized as follows: 1) Coverage depth has a significant effect on genome quality; 2) The level of contiguity of the assembled genome varies dramatically among different de novo tools; 3) The correctness of an assembled genome is closely related to the completeness of the genome. More than 30× nanopore data can be assembled into a relatively complete genome, the quality of which is highly dependent on the polishing using next generation sequencing data.

Conclusion

Considering the results of our investigation, the advantage and disadvantage of each tool are summarized and guidelines of selecting assembly tools are provided under specific conditions.

Evaluation of haemoparasite and Sarcocystis infections in Australian wild deer

Wild animals are natural reservoir hosts for a variety of pathogens that can be transmitted to other wildlife, livestock, other domestic animals, and humans. Wild deer (family Cervidae) in Europe, Asia, and North and South America have been reported to be infected with gastrointestinal and vector-borne parasites. In Australia, wild deer populations have expanded considerably in recent years, yet there is little information regarding which pathogens are present and whether these pathogens pose biosecurity threats to humans, wildlife, livestock, or other domestic animals. To address this knowledge gap, PCR-based screening for five parasitic genera was conducted in blood samples (n = 243) sourced from chital deer (Axis axis), fallow deer (Dama dama), rusa deer (Rusa timorensis) and sambar deer (Rusa unicolor) sampled in eastern Australia. These blood samples were tested for the presence of DNA from Plasmodium spp., Trypanosoma spp., Babesia spp., Theileria spp. and Sarcocystis spp. Further, the presence of antibodies against Babesia bovis was investigated in serum samples (n = 105) by immunofluorescence. In this study, neither parasite DNA nor antibodies were detected for any of the five genera investigated. These results indicate that wild deer are not currently host reservoirs for Plasmodium, Trypanosoma, Babesia, Theileria or Sarcocystis parasites in eastern Australia. We conclude that in eastern Australia, wild deer do not currently play a significant role in the transmission of these parasites. This survey represents the first large-scale molecular study of its type in Australian wild deer and provides important baseline information about the parasitic infection status of these animals. The expanding populations of wild deer throughout Australia warrant similar surveys in other parts of the country and surveillance efforts to continually assess the level of threat wild deer could pose to humans, wildlife, livestock and other domestic animals.

Molecular Survey of Tick-Borne Pathogens Reveals Diversity and Novel Organisms With Veterinary and Public Health Significance in Wildlife From a National Nature Reserve of China

Wildlife is involved in the maintenance and transmission of various tick-borne pathogens. The objective of the present study was to determine the occurrence and diversity of tick-borne pathogens in free-ranging wild animals collected from Tangjiahe National Nature Reserve of China. Blood or liver samples from 13 wild animals (5 takin, 3 Himalayan goral, 3 Reeves' muntjac, 1 forest musk deer, and 1 wild boar) were collected and screened for piroplasm, Anaplasma spp., Ehrlichia spp., and spotted fever group (SFG) rickettsiae by PCR-based on different gene loci. Three Theileria species, a potential novel Theileria parasite (Theileria sp. T4) and two Anaplasma species were identified in those wildlife. Theileria capreoli was found in Himalayan goral, Reeves' muntjac, and forest musk deer; Theileria luwenshuni, Theileria uilenbergi, and a potential novel, Theileria parasite (Theileria sp. T4), were identified in takin. Meanwhile, Anaplasma bovis was identified in Himalayan goral, takin, Reeves' muntjac, forest musk deer, and wild boar; Anaplasma phagocytophilum and related strains was found in takin, Reeves' muntjac, and forest musk deer. All wildlife included in this study was negative for Babesia, Anaplasma ovis, Anaplasma marginale, Ehrlichia, and SFG rickettsiae. Moreover, coinfection involving Theileria spp. and Anaplasma spp. was observed in eight wild animals. This study provided the first evidence of tick-borne pathogens in free-ranging wild animals from the nature reserve, where contact between domestic and wild animals rarely occurs.

Cross-priming amplification targeting the 18S rRNA gene for the rapid diagnosis of Babesia bovis infection

Babesia bovis is a known causative agent of bovine babesiosis and is widely distributed across China. Rapid detection and accurate identification of B. bovis is essential for follow-up management and epidemiological investigations. In this study, a cross-priming amplification combined with vertical flow (CPA-VF) assay was developed. The detection limit of the CPA-VF assay targeting the 18S rRNA gene was 320 fg per reaction at 61 °C for 60 min. No cross-reactions were observed with other piroplasms infective to cattle. Furthermore, 36 blood samples from experimentally-infected animals were accurately assessed using the CPA-VF assay. The performance of the CPA-VF assay was compared with the results of conventional PCR for 219 blood samples from the field. Our results demonstrate that the CPA-VF assay is a practical and effective diagnostic tool for bovine babesiosis caused by B. bovis infection.

Molecular evidence of piroplasm infection in companion animals in Hunan Province, China

BACKGROUND

Feline and canine babesiosis is an important tick-borne disease caused by parasites of the genus Babesia. The disease has a worldwide distribution and causes serious health problems in domestic and wild canidae and felidae.

RESULTS

Genomic DNA was isolated from blood samples, which were randomly collected from pet dogs (n = 115) and cats (n = 25) in Changsha city of Hunan Province, China. Results of nested PCR assay targeting 18S rRNA gene and partial gene sequencing revealed that seven animals were infected with Babesia species, five dogs (5/115, 4.3%) and two cats (2/25, 8.0%). Sequence analysis showed that four dogs (3.5%) were positive for Babesia canis, and the other one for Babesia vogeli (0.87%). The two cats were infected by Babesia hongkongensis.

CONCLUSIONS

The findings of this study will expand knowledge of the distribution of Babesia species and provide important epidemiological information for the control of animal babesiosis in China.

Rapid detection of Babesia motasi responsible for human babesiosis by cross-priming amplification combined with a vertical flow

Background

Babesia motasi is known as an etiological agent of human and ovine babesiosis. Diagnosis of babesiosis is traditionally performed by microscopy, examining Giemsa-stained thin peripheral blood smears. Rapid detection and accurate identification of species are desirable for clinical care and epidemiological studies.

Methods

An easy to operate molecular method, which requires less capital equipment and incorporates cross-priming amplification combined with a vertical flow (CPA-VF) visualization strip for rapid detection and identification of B. motasi.

Results

The CPA-VF targets the 18S rRNA gene and has a detection limit of 50 fg per reaction; no cross reaction was observed with other piroplasms infective to sheep or Babesia infective to humans. CPA-VF and real-time (RT)-PCR had sensitivities of 95.2% (95% confidence interval, CI 78.1–99.4%) and 90.5% (95% CI 72–97.6%) and specificities of 95.8 (95% CI 80.5–99.5%) and 97.9 (95% CI 83.5–99.9%), respectively, versus microscopy and nested (n) PCR combined with gene sequencing. The clinical performance of the CPA-VF assay was evaluated with field blood samples from sheep (n = 340) in Jintai county, Gansu Province, and clinical specimens (n = 492) obtained from patients bitten by ticks.

Conclusions

Our results indicate that the CPA-VF is a rapid, accurate, nearly instrument-free molecular diagnostic approach for identification of B. motasi. Therefore, it could be an alternative technique for epidemiological investigations and diagnoses of ovine and/or human babesiosis caused by B. motasi, especially in resource-limited regions.

Molecular Survey and Genetic Diversity of Babesia spp. and Theileria spp. in Cattle in Gansu Province, China

PURPOSE

Babesia spp. and Theileria spp. are tick-borne pathogens of livestock globally. In this study, we investigated the presence and distribution of these pathogens in cattle from 20 locations in 4 Counties of Wuwei City. The aim of the present research was to evaluate the spread of piroplasms, so as to provide the epidemiological information for control piroplasmosis in the region.

METHODS

The authors provided the molecular data for Babesia spp. and Theileria spp. and analyzed the obtained sequences of the 18S rRNA gene, Tams1 gene and MPSP gene by using the ClustalW program in MEGA version 6.06 software and BLASTn tool of NCBI GenBank database.

RESULTS

The total infection rates were detected by nPCR with 1.8% for T. orientalis, 3% for T. sinensis, 0.6% for T. annulata, 1.8% for B. motasi and 0.6% for B. bigemina.

CONCLUSIONS

To the best of our knowledge, this is the first report investigating T. sinensis from cattle by PCR in Wuwei City. In particular, ovine B. motasi has been for the first time detected in cattle in our study and its impact is worth discussing to figure out the potential reasons.

First detection and molecular identification of Anaplasma phagocytophilum in an introduced population of Reeve's muntjac (Muntiacus reevesi) in United Kingdom

In the present study, we investigated blood samples of 196 invasive Reeve's muntjac (Muntiacus reevesi) and 91 native roe deer (Capreolus capreolus) originating from the same area in Thetford Forest in Eastern England for the occurrence of blood pathogens such as Anaplasmatacae, Rickettsiales and Piroplasmida (Babesia spp., Theileria spp.) by using PCR. Babesia spp., Rickettsia spp. and Theileria spp. were not detected. Only two male (1%) Reeve's muntjacs and six (6.6%) roe deer were positive for Anaplasma phagocytophilum with 100% identity among their sequences. However, it is not clear whether Reeve's muntjac is less susceptible to infection, less susceptible to infestation by I. ricinus, or an infection in Reeve's muntjac is more lethal and therefore less positive animals are taken during hunting events.

Babesia divergens in human in Gansu province, China

Human babesiosis is an important tick-borne infectious disease. We investigated human babesiosis in the Gansu province and found that it is prevalent in this area with a prevalence of 1.3%. Results of gene sequencings indicate that 1.3% of patients were positive for Babesia divergens. This initial report of human B. divergens infections in Gansu Province should raise awareness of human babesiosis.

High resolution melting analysis of the 18S rRNA gene for the rapid diagnosis of bovine babesiosis

Background

Bovine babesiosis is caused by protozoan parasites of the genus Babesia and presents a wide spectrum of clinical manifestations. Disease severity depends on the type of Babesia species infection. Generally, B. bovis and B. bigemina are considered as the causative agents of bovine babesiosis; in addition, Babesia ovata and B. major are a group of benign bovine piroplasms. Therefore, species identification is important for diagnosis, epidemiological investigations and follow-up management.

Methods

Real-time PCR combined with high resolution melting (RT-PCR-HRM) analysis was used to detect and discriminate four Babesia species infective to cattle, including Babesia bovis, B. bigemina, B. major and B. ovata. The melting profiles and melting temperatures (Tm) of the amplicon targeting 18S rRNA revealed differences that can discriminate the four Babesia spp. Sensitivity and specificity of the analytical method were evaluated using 50 blood samples collected from experimentally infected cattle and 240 blood samples from areas where bovine babesiosis is an issue.

Results

RT-PCR-HRM analysis allowed to detect and discriminate four Babesia spp. (B. bovis, B. bigemina, B. major and B. ovata), which were responsible for bovine babesiosis in China. The protocol was validated with DNA samples from experimentally infected cattle and field infection in cattle.

Conclusions

Our results indicate that RT-PCR-HRM is a fast and robust tool for the simultaneous detection and discrimination of four Babesia species that are responsible for bovine babesiosis in China. This approach is applicable for both field and experimental samples, thus it could be useful in epidemiological investigations and diagnoses of bovine babesiosis.

Rapid detection and differentiation of Theileria annulata, T. orientalis and T. sinensis using high-resolution melting analysis

Bovine theileriosis, caused by protozoan parasites of the genus Theileria, presents with various clinical symptoms. In cattle, clinical presentations and outcomes of bovine theileriosis are closely correlated with the causative Theileria spp. Thus, accurate detection and discrimination of Theileria spp. are essential for epidemiological studies and for provision of clinical management strategies. High-resolution melting (HRM) analyses of two amplicons targeting the 18S rRNA indicated that T. annulata, T. orientalis, and T. sinensis isolated from China can be accurately detected and discriminated with the lowest detection limit of 1-10 copy numbers of plasmid bearing the 18S rRNA sequence. The approach was verified with DNA samples from experimentally infected cattle and field samples. Thus, this assay is useful for diagnosis of bovine theileriosis in field samples and experimentally infected animals, and could also be applicable for the survey of parasite dynamics, epidemiological studies.

Molecular detection and identification of tick-borne bacteria and protozoans in goats and wild Siberian roe deer (Capreolus pygargus) from Heilongjiang Province, northeastern China

BACKGROUND

Small ruminants are important hosts for various tick species and tick-associated organisms, many of which are zoonotic. The aim of the present study was to determine the presence of tick-borne protozoans and bacteria of public health and veterinary significance in goats and wild Siberian roe deer (Capreolus pygargus) from Heilongjiang Province, northeastern China.

METHODS

The occurrence of piroplasms, Anaplasma phagocytophilum, A. bovis, A. marginale, A. capra, A. ovis, Ehrlichia spp. and spotted fever group rickettsiae was molecularly investigated and analyzed in 134 goats and 9 free ranging C. pygargus living in close proximity.

RESULTS

Piroplasm DNA was detected in 16 (11.9%) goats and 5 C. pygargus. Sequence analysis of 18S rRNA sequences identified 3 Theileria species (T. luwenshuni, T. capreoli and T. cervi). Four Anaplasma species (A. ovis, A. phagocytophilum, A. bovis and A. capra) were identified in goats and C. pygargus. Anaplasma ovis and A. bovis were detected in 11 (8.2%) and 6 (4.5%) goats, respectively; A. phagocytophilum, A. bovis and A. capra were found in 3, 7 and 3 C. pygargus, respectively. Sequence analysis of 16S rRNA sequences revealed the presence of 5 different genetic variants of A. bovis in goats and C. pygargus, while the analysis of 16S rRNA and gltA sequence data showed that A. capra isolates identified from C. pygargus were closely related to the genotype identified from sheep and Haemaphysalis qinghaiensis, but differed with the genotype from humans. Anaplasma/Theileria mixed infection was observed in 2 (1.5%) goats and 5 C. pygargus, and co-existence involving potential zoonotic organisms (A. phagocytophilum and A. capra) was found in 2 C. pygargus. All samples were negative for A. marginale, Ehrlichia spp. and SFG rickettsiae.

CONCLUSIONS

These findings report the tick-borne pathogens in goats and C. pygargus, and a greater diversity of these pathogens were observed in wild animals. Three Theileria (T. luwenshuni, T. capreoli and T. cervi) and four Anaplasma species (A. ovis, A. phagocytophilum, A. bovis and A. capra) with veterinary and medical significance were identified in small domestic and wild ruminants. The contact between wild and domestic animals may increase the potential risk of spread and transmission of tick-borne diseases.

First molecular evidence of Babesia occultans and Theileria separata infection in ticks and sheep in China

Protozoan parasites of the genus Babesia and Theileria are significant tick-borne pathogens of domestic animals and cause economic losses to the livestock industry in tropical and subtropical regions worldwide. In this study, 274 blood samples and 32 tick samples were collected from four counties of Wuwei City in northwestern China in June and July in 2018. The DNA from the field samples was analyzed for Babesia or Theileria infection using specific PCR and sequencing based on 18S rRNA gene fragments. The total infection rates were 0.4% for B. motasi and T. separata (both 1/274) in sheep, 3.1% for T. annulata (1/32), 6.2% for B. occultans (2/32) and 9.4% for B. bigemina (3/32) in ticks, respectively. In particular, T. separata has been for the first time detected in sheep in China and B. occultans in Hyalomma asiaticum from Gansu Province of China.

Molecular detection and genetic diversity of Babesia canis canis in pet dogs in Henan Province, China

Canine babesiosis is an important tick-borne disease caused by Babesia spp. A total of 130 blood samples were randomly collected from pet dogs in Zhengzhou city, Henan Province, China, and screened for the presence of piroplasms with nested PCR and gene sequencing targeting the 18S rRNA gene. On the basis of blast analysis of the 18S rRNA gene sequences, our results revealed that seven dogs (5.4%) were infected with Babesia canis canis. The sequences were compared with those in GenBank, and alignments showed that all B. canis canis isolates belonged to genotype B. This is the first report of B. canis canis infection in dogs in China.

The first molecular detection and genetic diversity of Babesia caballi and Theileria equi in horses of Gansu province, China

Equine piroplasmosis, caused by Theileria equi and Babesia caballi, is an economically important tick-borne disease worldwide. In the current study, 242 blood samples were randomly collected from horses in Zhangye city of Gansu province, China. The presence and genetic diversity of piroplasms were evaluated with a nested PCR assay, gene sequencing and phylogenetic analysis. The results showed that seventy-five (31.0%) samples were positive for piroplasms. Sequences analysis showed that seventy-three (30.2%) were positive for T. equi, and seven (2.9%) for B. caballi, five of which (2.1%) were infected with T. equi and B. caballi. Phylogenetic analysis revealed two T. equi genotypes (C and E) and one B. caballi genotype (A). The molecular epidemiological and genetic diversity results provide important epidemiological data for control of equine piroplasmosis caused by T. equi and B. caballi in China.

First Molecular Detection of Piroplasm Infection in Pet Dogs from Gansu, China

Babesiosis, the hemolytic disease caused by Babesia, which is a tick-transmitted obligate intraerythrocytic protozoan parasite. This disease is responsible for significant mortality and morbidity rates and enormous economic losses to the livestock industry in tropical and subtropical regions worldwide. In this study, blood samples were collected from 141 pet dogs from Gansu, China, and analyzed for Babesia or Theileria spp. infection using specific PCR and sequencing based on 18S rRNA gene fragments. The results indicated that 18S rRNA gene sequences from 11 samples were similar to the 18S rRNA gene sequences in Babesia canis vogeli (2) and Theileria sinensis (9). The total infected rates of B. canis vogeli and T. sinensis were 1.4% (2/141) and 6.4% (9/141), respectively. This represents the first molecular report of T. sinensis in dogs worldwide and of B. canis vogeli in dogs from Gansu province of China. Furthermore, the finding of T. sinensis in dogs may represent the common infection of this parasite occurring in Gansu.

Molecular detection and characterization of Theileria infection in cattle and yaks from Tibet Plateau Region, China

Theileriosis continues to threaten the livestock industry worldwide, but comprehensive epidemiological surveys for this disease have not been conducted in the Tibet Plateau Region, China. In this study, we screened 154 cattle blood samples from the Tibet Plateau Region (Lhasa, Lhoka, and Tianzhu), China, for detection of Theileria pathogens by polymerase chain reaction (PCR) with species-specific primers. The results revealed that the prevalence was 6.9 % (2/29) for Theileria orientalis and 27.6 % (8/29) for Theileria sinensis in Lhasa, 0 % (0/30) for T. orientalis and 26.7 % (8/30) for T. sinensis in Lhoka, and 0 % (0/95) for T. orientalis and 30.5 % (29/95) for T. sinensis in Tianzhu. Interestingly, Theileria luwenshuni, which was a previously reported pathogenic Theileria sp. in sheep and goats, was detected in blood samples from cattle and yaks for the first time, with a prevalence of 10 % (3/30) in Lhoka and 1.1 % (1/95) in Tianzhu. No other Theileria sp. was detected in these samples. T. sinensis and T. orientalis infections were detected in cattle and yaks, and T. luwenshuni was discovered for the first time in cattle and yaks in the Tibet Plateau Region, China.

Report of Theileria luwenshuni and Theileria sp. RSR from cervids in Gansu, China

Theileria parasites are important tick-borne pathogens of animals and cause huge economic losses worldwide. Here, we undertook to assess the prevalence of Theileria spp. in cervids in Gansu, China, based on PCR analysis and sequencing of the 18S rRNA genes. Molecular survey showed that Theileria luwenshuni and Theileria sp. RSR were frequently found in Gansu cervids, and the prevalence of T. luwenshuni was 66.7% (n = 9, 6/9) in roe deer in Zhengning County, 58.3% (n = 12, 7/12) in sika deer in Ningxian County, 50% (n = 10, 5/10) in sika deer and 42.9% (n = 14, 6/14) in red deer in Weiyuan County. The prevalence of Theileria sp. RSR was 77.8% (n = 9, 7/9) in roe deer in Zhengning County, 75% (n = 12, 9/12) in sika deer in Ningxian County, 60.0% (n = 10, 6/10) in sika deer, and 50.0% (n = 14, 7/14) in red deer in Weiyuan County. The co-prevalence of the two T. luwenshuni and Theileria sp. RSR was 55.6% (n = 5, 5/9) in roe deer in Zhengning County, 50% (n = 12, 6/12) in sika deer in Ningxian county, 50% (n = 10, 5/10) in sika deer and 35.7% (n = 14, 5/14) in red deer in Weiyuan County, respectively. No other Theileria species was found in these samples. T. luwenshuni and Theileria sp. RSR were detected for the first time in cervids in Gansu, China. Animal experiments showed that four sheep were inoculated with roe deer blood from Zhengning, sika deer blood from Ningxian, sika deer blood, and red deer blood from Weiyuan, respectively, and the Theileria isolated from these inoculated sheep was identified as T. luwenshuni, but Theileria sp. RSR was not detected in these sheep. Our results extend our understanding of the epidemiology of cervine theileriosis in Gansu, China, and will facilitate the implementation of measures to control theileriosis in cervids and small ruminants. This was the first report to demonstrate the occurrence of T. luwenshuni from roe deer, sika deer, and red deer worldwide.

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.