Investigating the first outbreak of oriental theileriosis in cattle in South Australia using multiplexed tandem PCR (MT-PCR)

Epidemiology and Transmission of Theileria orientalis in Australasia

Oriental theileriosis, a disease primarily impacting cattle is caused by an apicomplexan hemoprotozoan parasite, Theileria orientalis. It has now become established in the Australasia region. The organism was long considered a benign cause of persistent infections; however, an increase in clinical outbreaks since 2006 in the eastern Australian states and New Zealand was associated with the identification of the pathogenic Ikeda (Type 2) and Chitose (Type 1) genotypes. Unlike the pathogenic T. parva and T. annulate, which target leucocytes, clinical manifestation with T. orientalis is due to its effects on erythrocytes, with the infection sometimes designated as Theileria associated bovine anemia (TABA). In Australia and New Zealand, the tick Haemaphysalis longicornis is the principal vector, though other Haemaphysalis species are also likely vectors. The endemic status of infection with pathogenic genotypes in areas with low or absent tick populations is an apparent paradox that may be attributable to alternative modes of transmission, such as mechanical transmission by hematophagous insects (lice, mosquitoes, and biting flies), vertical transmission, and transmission via iatrogenic means. This review addresses the evidence for the different modes of transmission of T. orientalis with particular focus on the reported and potential vectors in Australasia.

Distribution and Prevalence of Theileria orientalis Genotypes in Adult Lactating Dairy Cows in South West Region of Western Australia

Bovine anaemia caused by Theileria orientalis group (BATOG) causes significant production and economic losses in Australia's cattle industry. The pathogenic T. orientalis genotypes reported in Australian cattle are type 1 (Chitose) and type 2 (Ikeda). The present study aimed to determine the prevalence and distribution of T. orientalis genotypes in adult lactating cows in Western Australia (WA) dairy herds. A total of 100 whole blood samples from lactating cows from 10 farms were obtained and screened for T. orientalis using polymerase chain reaction (PCR). Sanger sequencing was subsequently used to characterise T. orientalis genotypes isolated from positive samples. A total of thirteen cows (13%; 95% CI: 7.1-21.2%) were positive for T. orientalis, and six out of ten farms (60%; 95% CI: 26.2-87.8%) housed at least one T. orientalis-positive cow. The distribution of T. orientalis was found to be wide and dense in the South west region of WA and the southern coast of WA. The predominant T. orientalis genotype identified was Ikeda (n = 11, 11%; 95% CI: 5.6-18.8%), while the Buffeli genotype was identified in WA for the first time, albeit at a low prevalence (n = 1, 1%; 95% CI: 0.0-5.4%). This study has provided useful epidemiological evidence on the prevalence and distribution of T. orientalis in adult lactating dairy cows in WA dairy farms, and on the importance of conducting widespread surveillance programs for the understanding of BATOG in WA.

Oriental theileriosis associated with a new genotype of Theileria orientalis in buffalo (Bubalus bubalis) calves in Uttar Pradesh, India

Theileria orientalis is known to cause a benign infection in cattle and buffalo (Bubalus bubalis). However, the Ikeda and Chitose genotypes of the parasite cause lethal disease in beef and dairy cattle. Recently an outbreak of clinical oriental theileriosis occurred in buffalo calves in a Government Animal Husbandry and Agricultural Farm located in Uttar Pradesh, India. Examination of Giemsa stained thin blood smears revealed typical rod-shaped T. orientalis piroplasms in the erythrocytes. The clinical signs included pyrexia, nasal discharge, lacrimation, lethargy, inappetence and anaemia with varying degrees of paleness of the visible mucous membranes. Vascular congestion in internal organs, pulmonary emphysema and consolidation of lungs, focal areas of necrosis in the heart with mononuclear cell infiltration, focal mononuclear cell aggregation in the cortex and tubular degeneration of the kidney were significant necropsy findings. The T. orientalis major piroplasm surface protein (MPSP) gene was amplified by polymerase chain reaction (PCR) using specific primers. The nucleotide sequence analysis of the PCR product revealed 84.8% identity between the T. orientalis Uttar Pradesh isolate and other reference genotypes available in the public domain. Furthermore, the phylogenetic analysis of the MPSP gene sequence ratified that this is a new genotype of T. orientalis. This is the first report of a clinical outbreak of oriental theileriosis in Indian buffalo calves caused by a novel genotype of T. orientalis.

Endemic infection of cattle with multiple genotypes of Theileria orientalis on the Northern Tablelands of New South Wales despite limited presence of ticks

Bovine theileriosis, caused by the Theileria orientalis complex, causes a mild persistent infection with the severity dependent on the infecting genotype and host exposure status. Clinical theileriosis was first detected on the Northern Tablelands of NSW in 2009 and a high prevalence of infection in cattle reported in 2013. However, the parasite was not genotyped and likely vectors not investigated. In response to ongoing clinical cases, here we identify the Theileria genotypes present in the region and potential vectors. Genotype-specific multiplex qPCR of 90 blood samples from eight farms revealed a 100 % prevalence of T. orientalis in individual cattle with concurrent infection with all three genotypes present in 73 % of cases. The prevalence of the pathogenic genotype (Ikeda) differed significantly between farms; however, the level of parasitemia was not affected by genotype or associated with clinical disease. Parasitaemia levels were higher in heifers than cows. Questing tick collection on six of the farms between November 2017 and May 2019 yielded 358 questing ticks from one farm, all of which were morphologically identified as Haemaphysalis bancrofti. Larvae accounted for 59 % of the ticks followed by nymphs (34 %) and adults (7%). Theileria was detected only in nymphs with Ikeda and Buffeli genotypes each being detected in one of four pools of ticks. The high prevalence of co-infection with three genotypes of T. orientalis indicates that they are now endemic in the region and confirms the lack of cross-protection between genotypes. This is the first detection of T. orientalis in questing H. bancrofti ticks: indicating that it may be a vector for T. orientalis in this region. However, the high prevalence of bovine infection is at odds with the absence of captured ticks or history of tick infestation on five of the six farms raising the possibility that other vectors or transmission pathways play key roles.

Targeted Next-Generation Sequencing and Informatics as an Effective Tool to Establish the Composition of Bovine Piroplasm Populations in Endemic Regions

Protists of the genera Babesia and Theileria (piroplasms) cause some of the most prevalent and debilitating diseases for bovines worldwide. In this study, we established and used a next-generation sequencing-informatic approach to explore the composition of Babesia and Theileria populations in cattle and water buffalo in a country (Pakistan) endemic for these pathogens. We collected individual blood samples from cattle (n = 212) and water buffalo (n = 154), extracted genomic DNAs, PCR-amplified the V4 hypervariable region of 18S small subunit rRNA gene from piroplasms, sequenced amplicons using Illumina technology, and then analysed data using bioinformatic platforms. The results revealed piroplasms in 68.9% (252/366) samples, with overall occurrence being markedly higher in cattle (85.8%) than in water buffaloes (45.5%). Babesia (B.) occultans and Theileria (T.) lestoquardi-like species were recorded for the first time in Pakistan, and, overall, T. annulata was most commonly detected (65.8%) followed by B. bovis (7.1%), B. bigemina (4.4%), and T. orientalis (0.5%), with the genetic variability within B. bovis being pronounced. The occurrence and composition of piroplasm species varied markedly across different agro-ecological zones. The high detection of T. annulata in asymptomatic animals suggested a relatively high level of endemic stability of tropical theileriosis in the bovine population.

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.

Hematological Changes Associated with Theileria orientalis Infection in Korean Indigenous Cattle

Tick-borne pathogens can cause serious problems in grazing cattle. However, little information is available on tick-mediated diseases in cattle grazing on mountains. Thus, this study aimed to understand the potential problems related to tick-borne diseases in grazing cattle through the investigation of prevalent tick-transmitted infections, and their associated hematological changes, in terms of season and grazing type in Korean indigenous cattle (=Hanwoo). Hanwoo cattle from 3 regions of the Republic of Korea (=Korea) were either maintained indoors or placed on grassy mountains from spring to fall of 2014 and 2015. Cattle that grazed in mountainous areas showed a greater prevalence of tick-borne infections with an increased Theileria orientalis infection rate (54.7%) compared to that in non-grazing cattle (16.3%) (P<0.001). Accordingly, the red blood cell (RBC) count and hematocrit (HCT) values of grazing cattle were significantly lower than those of non-grazing cattle throughout the season (P<0.05). Moreover, RBC, hemoglobin (Hb), and HCT of T. orientalis-positive group were significantly lower than those of T. orientalis-negative group (P<0.05). T. orientalis is a widespread tick-borne pathogen in Korea. Grazing of cattle in mountainous areas is closely associated with an increase in T. orientalis infection (RR=3.4, P<0.001), and with consequent decreases in RBC count and HCT. Thus, these findings suggest that the Hanwoo cattle in mountainous areas of Korea are at a high risk of infection by T. orientalis, which can lead to hematological alterations. This study highlights the necessity of preventive strategies that target T. orientalis infection.

An outbreak of oriental theileriosis in dairy cattle imported to Vietnam from Australia

This study reports an outbreak of oriental theileriosis in dairy cattle imported to Vietnam from Australia. Following clinical and pathological diagnoses, a total of 112 cattle blood samples were divided into three groups and tested using multiplexed tandem PCR. Group 1 were from aborted heifers in Vietnam; group 2 were from cattle before shipment from group 1 cattle and group 3 were from the same batch of cattle but transported to Taiwan. Theileria orientalis DNA was detected in 72·3% cattle. The prevalences of T. orientalis in groups 1, 2 and 3 were 77·6, 86·9 and 57·5%, respectively, and the difference in prevalence was significant between groups 1 and 3 (P < 0·0001). The infection intensities of genotypes chitose and ikeda of T. orientalis were higher in groups 1 (57 721 and 33 709, respectively) and 3 (5897 and 61 766, respectively) than those in group 2 (2071 and 6331, respectively). Phylogenetic analyses of the major piroplasm surface protein sequences revealed that genotypes chitose and ikeda determined herein were closely related to those previously reported from Australia. This first report of an outbreak of oriental theileriosis in imported cattle emphasizes improved measures for the export and import of cattle infected with T. orientalis.

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.