Theileria orientalis Ikeda infection detected in red deer but not dogs or horses in New Zealand.

AIMS: To determine whether evidence for infection with Theileria orientalis (Ikeda) could be identified in samples of commercial red deer (Cervus elaphus), horses, and working farm dogs in New Zealand. METHODS: Blood samples were collected during October and November 2019 from a convenience sample of red deer (n = 57) at slaughter. Equine blood samples (n = 50) were convenience-sampled from those submitted to a veterinary pathology laboratory for routine testing in January 2020. Blood samples, collected for a previous study from a convenience sample of Huntaway dogs (n = 115) from rural regions throughout the North and South Islands of New Zealand between August 2018 and December 2020, were also tested. DNA was extracted and quantitative PCR was used to detect the T. orientalis Ikeda major piroplasm surface protein (MPSP) gene. A standard curve of five serial 10-fold dilutions of a plasmid carrying a fragment of the T. orientalis MPSP gene was used to quantify the number of T. orientalis organisms in the samples. MPSP amplicons obtained by end-point PCR on positive samples were isolated and subjected to DNA sequencing. The resulting sequences were compared to previously published T. orientalis sequences. RESULTS: There were 6/57 (10%) samples positive for T. orientalis Ikeda from the deer and no samples positive for T. orientalis Ikeda from the working dogs or horses. The mean infection intensity for the six PCR-positive deer was 5.1 (min 2.2, max 12.4) T. orientalis Ikeda organisms/µL. CONCLUSIONS AND CLINICAL RELEVANCE: Red deer can potentially sustain low infection intensities of T. orientalis Ikeda and could act as reservoirs of infected ticks. Further studies are needed to determine whether naïve ticks feeding on infected red deer can themselves become infected. ABBREVIATIONS: Cq: Quantification cycle; LOQ: Limits of quantification; MPSP: Major piroplasm surface protein; qPCR: Quantitative polymerase chain reaction.

Identification and isolation of pathogenic Theileria orientalis Ikeda genotype from confined dairy cattle, in Hebei, China.

Theileria orientalis is known to be a group of benign cattle parasites with a cosmopolitan distribution, and has been classified into 11 genotypes through MPSP gene phylogenetic analysis. In China, T. orientalis is the most prevalent Theileria species, with several genotypes, but few fatal cases have been reported. In June 2020, dairy cattle in Zhangjiakou, Hebei Province, showed clinical symptoms of piroplasmosis, causing many animals to die. Blood smears and PCR detection results confirmed T. orientalis infection with a 66.7% positive rate of collected blood samples. The MPSP sequences analysis revealed parasite genotypes 1 (Chitose) and 2 (Ikeda). Aiming to isolate the pathogens, experimental animal was infected with T. orientalis via inoculation of the positive blood samples. The results has shown that only T. orientalis genotype 2 (Ikeda) was obtained that has confirmed by MPSP and 18S rRNA sequences analysis, indicating that the Ikeda type was predominant and responsible for the disease. Although many T. orientalis genotypes are present in China, the possibility of T. orientalis genotypes 1 and 2 infections in confined dairy cattle should be considered to avoid additional economic losses.

Theileria orientalis Ikeda Genotype in Cattle, Virginia, USA.

Theileria orientalis Ikeda genotype is a parasite that causes a disease in cattle that results in major economic issues in Asia, New Zealand, and Australia. The parasite is transmitted by Haemaphysalis longicornis ticks, which have recently been reported in numerous states throughout the eastern United States. Concurrently, cattle in Virginia showed clinical signs consistent with a hemoprotozoan infection. We used amplicons specific for the major piroplasm surface protein and small subunit rDNA of piroplasms to test blood samples from the cattle by PCR. Bidirectional Sanger sequencing showed sequences with 100% identity with T. orientalis Ikeda genotype 2 sequences. We detected the parasite in 3 unrelated herds and from various animals sampled at 2 time points. Although other benign T. orientalis genotypes are endemic to the United States, detection of T. orientalis Ikeda genotype might represent a risk for the cattle industry in Virginia.

Associations between Theileria orientalis Ikeda type infection and the growth rates and haematocrit of suckled beef calves in the North Island of New Zealand.

AIMS: The principle aim of this study was to examine the association between infection with Theileria orientalis Ikeda type and growth rates of suckled beef calves on four beef farms. In addition, associations between calf sex, sampling time, and individual farm and T. orientalis Ikeda type infection intensity and haematocrit (HCT) were investigated. METHODS: The study was a prospective longitudinal study in which 240 calves from four purposively selected beef farms in the North Island of New Zealand were blood sampled and weighed in late spring, mid-summer and early autumn. Two farms were from high-risk (A and B) and two from low-risk (C and D) tick areas. Blood samples were analysed to determine HCT, and the number of T. orientalis Ikeda type organisms/µL of blood (infection intensity) using a quantitative PCR assay. A calf was defined as infected if >415 organisms/µL were detected in a blood sample. Linear mixed models were used to examine associations between infection intensity, mean daily liveweight gain (MDG), HCT, calf sex and time of sampling on the four farms. RESULTS: On Farms A and B nearly all calves were infected at each sampling time, on Farm C <30% were infected at any sampling and on Farm D infection prevalence increased from 32 to 79% between late spring and early autumn. On Farms C and D, from mid-summer to early autumn, mean MDG was 0.127 (95% CI=0.072-0.183) kg/day less for infected than uninfected calves (p<0.001). On all farms MDG was negatively associated with infection intensity for mid-summer and early autumn sampling times (p=0.037). The relationship between time of sampling and infection intensity varied between farms (p<0.001), and between male and female calves (p=0.018). Females had a higher infection intensity than males at the mid-summer and early autumn samplings. The association between HCT and infection intensity varied with sampling time and farm (p=0.018). There was a strong negative association between infection intensity and HCT at the late spring sampling, but in mid-summer there was no association, and in early autumn only a weak association. CONCLUSIONS AND CLINICAL RELEVANCE: This study has shown that beef farmers in the North Island of New Zealand should be concerned about the welfare effects and economic impacts of T. orientalis Ikeda type infection in suckled beef calves.

Design and Implementation of Autonomous and Non-Autonomous Time-Delay Chaotic System Based on Field Programmable Analog Array.

Time-delay chaotic systems can have hyperchaotic attractors with large numbers of positive Lyapunov exponents, and can generate highly stochastic and unpredictable time series with simple structures, which is very suitable as a secured chaotic source in chaotic secure communications. But time-delay chaotic systems are generally designed and implemented by using analog circuit design techniques. Analog implementations require a variety of electronic components and can be difficult and time consuming. At this stage, we can now solve this question by using FPAA (Field-Programmable Analog Array). FPAA is a programmable device for implementing multiple analog functions via dynamic reconfiguration. In this paper, we will introduce two FPAA-based design examples: An autonomous Ikeda system and a non-autonomous Duffing system, to show how a FPAA device is used to design programmable analog time-delay chaotic systems and analyze Shannon entropy and Lyapunov exponents of time series output by circuit and simulation systems.

Clinical haematology and biochemistry profiles of cattle naturally infected with Theileria orientalis Ikeda type in New Zealand.

AIMS: To present the haematology and biochemistry profiles for cattle in New Zealand naturally infected with Theileria orientalis Ikeda type and investigate if the results differed between adult dairy cattle and calves aged <6 months. METHODS: Haematology and biochemistry results were obtained from blood samples from cattle which tested positive for T. orientalis Ikeda type by PCR, that were submitted to veterinary laboratories in New Zealand between October 2012 and November 2014. Data sets for haematology and biochemistry results were prepared for adult dairy cattle (n=62 and 28, respectively) and calves aged <6 months (n=62 and 28, respectively), which were matched on the basis of individual haematocrit (HCT). Results were compared between age groups when categorised by HCT. Selected variables were plotted against individual HCT, and locally weighted scatterplot smoothing (Loess) curves were fitted to the data for adult dairy cattle and calves <6 months old. RESULTS: When categorised by HCT, the proportion of samples with HCT <0.15 L/L (severe anaemia) was greater for adult dairy cattle than for beef or dairy calves, for both haematology (p<0.002) and biochemistry (p<0.001) submissions. There were differences (p<0.05) between adult dairy cattle and calves aged <6 months in the relationships between HCT and red blood cell counts, mean corpuscular volume, mean corpuscular haemoglobin, mean corpuscular haemoglobin concentrations, lymphocyte and eosinophil counts, and activities of glutamate dehydrogenase and aspartate aminotransferase. In both age groups anisocytosis was frequently recorded. The proportion of blood smears showing mild and moderate macrocytosis was greater in adults than calves (p=0.01), and mild and moderate poikilocytosis was greater in calves than adults (p=0.005). CONCLUSIONS AND CLINICAL RELEVANCE: The haematology and biochemistry changes observed in cattle infected with T. orientalis Ikeda type were consistent with extravascular haemolytic anaemia. Adult dairy cattle were more likely to be severely anaemic than calves. There were differences in haematology and biochemistry profiles between adult dairy cattle and calves, but most of these differences likely had a physiological rather than pathological basis. Overall, the haematological changes in calves aged <6 months appeared less severe than in adult dairy cattle.

Cluster analysis of the clinical histories of cattle affected with bovine anaemia associated with Theileria orientalis Ikeda type infection.

AIM To determine the most commonly used words in the clinical histories of animals naturally infected with Theileria orientalis Ikeda type; whether these words differed between cases categorised by age, farm type or haematocrit (HCT), and if there was any clustering of the common words in relation to these categories. METHODS Clinical histories were transcribed for 605 cases of bovine anaemia associated with T. orientalis (TABA), that were submitted to laboratories with blood samples which tested positive for T. orientalis Ikeda type infection by PCR analysis, between October 2012 and November 2014. χ2 tests were used to determine whether the proportion of submissions for each word was similar across the categories of HCT (normal, moderate anaemia or severe anaemia), farm type (dairy or beef) and age (young or old). Correspondence analysis (CA) was carried out on a contingency table of the frequency of the 28 most commonly used history words, cross-tabulated by age categories (young, old or unknown). Agglomerative hierarchical clustering, using Ward's method, was then performed on the coordinates from the correspondence analysis. RESULTS The six most commonly used history words were jaundice (204/605), lethargic (162/605), pale mucous membranes (161/605), cow (151/605), anaemia (147/605), and off milk (115/605). The proportion of cases with some history words differed between categories of age, farm type and HCT. The cluster analysis indicated that the recorded history words were grouped in two main clusters. The first included the words weight loss, tachycardia, pale mucous membranes, anaemia, lethargic and thin, and was associated with adult (p<0.001), severe anaemia (p<0.001) and dairy (p<0.001). The second cluster included the words deaths, ill-thrift, calves, calf and diarrhoea, and was associated with young (p<0.001), normal HCT (p<0.001), beef (p<0.001) and moderate anaemia (p<0.001). CONCLUSIONS AND CLINICAL RELEVANCE Cluster analysis of words recorded in clinical histories submitted with blood samples from cases of TABA indicates that two potentially different disease syndromes were associated with T. orientalis Ikeda type infection. One was consistent with the affected cattle suffering from a severe regenerative extravascular haemolytic anaemia, the second displaying as ill thrift and diarrhoea, particularly in young beef cattle.

Towards an integrated phylogenetic classification of the Tremellomycetes.

Families and genera assigned to Tremellomycetes have been mainly circumscribed by morphology and for the yeasts also by biochemical and physiological characteristics. This phenotype-based classification is largely in conflict with molecular phylogenetic analyses. Here a phylogenetic classification framework for the Tremellomycetes is proposed based on the results of phylogenetic analyses from a seven-genes dataset covering the majority of tremellomycetous yeasts and closely related filamentous taxa. Circumscriptions of the taxonomic units at the order, family and genus levels recognised were quantitatively assessed using the phylogenetic rank boundary optimisation (PRBO) and modified general mixed Yule coalescent (GMYC) tests. In addition, a comprehensive phylogenetic analysis on an expanded LSU rRNA (D1/D2 domains) gene sequence dataset covering as many as available teleomorphic and filamentous taxa within Tremellomycetes was performed to investigate the relationships between yeasts and filamentous taxa and to examine the stability of undersampled clades. Based on the results inferred from molecular data and morphological and physiochemical features, we propose an updated classification for the Tremellomycetes. We accept five orders, 17 families and 54 genera, including seven new families and 18 new genera. In addition, seven families and 17 genera are emended and one new species name and 185 new combinations are proposed. We propose to use the term pro tempore or pro tem. in abbreviation to indicate the species names that are temporarily maintained.

Epidemiology, Clinical Signs, and Risk Factors Associated with Theileriosis in Australian Cattle (2006-2022).

For over a decade, bovine anaemia caused by Theileria orientalis Ikeda has been a significant disease in the Australian cattle industry. In this study, we conducted a spatial and temporal analysis of theileriosis in Australia using historic data from submissions to the New South Wales Department of Primary Industries (NSW DPI) from 2006 to 2022, where herd history, clinical signs, and PCR results were available. Since the first detections of bovine theileriosis in the Sydney area in 2006, the disease spread north- and southward and is now endemic to the southeast coast of Australia, closely mirroring the distribution of the principal vector Haemaphysalis longicornis. Across all years, the prevalence of the Ikeda genotype was 88%, while the prevalence of the benign Chitose and Buffeli genotypes was 55% and 38%, respectively. The majority of submissions were from beef cattle in coastal NSW, with anaemia, fever, jaundice, abortion, and lethargy the most frequently reported clinical signs. Transportation was identified as the major risk factor for disease. Until 2015, the majority of cases were reported in adult cattle, while in later years, calves made up the majority of cases, most likely due to the widespread acquisition of immunity in adults. Calves were significantly more likely to present with diarrhoea, lethargy, and anaemia, and to suffer mortality, while adults were significantly more likely to present with jaundice. Instances of abortion were observed to be significantly associated with beef cattle. The relationship between the level of parasitaemia and anaemia revealed a strong negative correlation for all animals examined.

Transient efficacy of buparvaquone against the US isolate of Theileria orientalis Ikeda genotype in sub-clinically infected cattle.

Introduction: Theileria orientalis, an economically significant tick-borne hemoparasite, infects cattle globally. The T. orientalis Ikeda genotype, transmitted by Haemaphysalis longicornis ticks, is associated with clinical manifestations characterized by anemia, abortions, and mortality, although subclinical infections prevail. Despite the common occurrence of subclinical infections, therapeutic interventions targeting T. orientalis Ikeda in such cases are currently lacking, impeding effective parasite control measures. To address this critical knowledge gap, we assessed the efficacy of buparvaquone (BPQ) in eliminating the T. orientalis Ikeda, US isolate, in sub-clinically infected cattle. Methods: Twelve sub-clinically infected calves, identified by the presence of T. orientalis in peripheral blood alongside the absence of fever and anemia, were enrolled in the study. Six calves received two treatments of the BPQ label dose (2.5 mg/kg) at a 48-h interval, while additional three calves received the drug at a dosage of 6 mg/kg following the same regimen. Three untreated calves served as controls. Results and discussion: Endpoint and quantitative PCR analyses revealed that BPQ exerted a transient effect on T. orientalis parasitemia. Parasites remained undetectable in peripheral blood until weeks 4 and 11 post-treatment in animals administered 2.5 mg/kg and 6 mg/kg of BPQ, respectively. Intriguingly, following recrudescence, administering 6 mg/kg to animals previously treated with 2.5 mg/kg did not result in a reduction in parasite load. Pharmacokinetic analysis data suggested that escalating the dosage led to a less than proportional increase in serum concentrations of BPQ. Moreover, a significant yet reversible decrease (p < 0.05) in blood urea nitrogen was observed in animals treated with the drug, irrespective of the dosage. Despite parasitemia relapse, animals treated with 6 mg/kg BPQ exhibited a noteworthy decrease (p < 0.05) in IgG levels specific to the T. orientalis major piroplasm surface protein compared to controls and animals treated with 2.5 mg/kg of the drug. Conclusion: BPQ did not demonstrate efficacy in clearing subclinical T. orientalis Ikeda infection. Future investigations are warranted to explore innovative therapeutic modalities that, in synergy with vaccines and diagnostic assays, can facilitate the development of comprehensive programs aimed at controlling and eradicating this parasite.

Theileria orientalis Ikeda infection does not negatively impact growth performance or breeding soundness exam results in young beef bulls at bull test stations.

Introduction: Theileria orientalis Ikeda genotype is an emerging cattle disease in the US. Since 2017, when T. orientalis Ikeda was discovered in beef cattle in two counties in Virginia, cattle infections have risen to include ~67% of Virginia counties and 14 states. Consistent with New Zealand studies, many infected herds in Virginia were >90% positive upon initial testing without overt evidence of infection. Central bull tests present a unique opportunity to study the effects of T. orientalis Ikeda infections, as bulls from multiple source herds are consolidated. The objective of this study was to determine if infection with T. orientalis Ikeda affected the average daily gain (ADG), adjusted yearling weight (AYW) and breeding soundness of bulls at two test stations in Virginia over a period of years. Materials and methods: The bulls were fed and housed similarly to compare their growth performance and breeding soundness. For T. orientalis Ikeda testing, DNA was extracted from whole blood for quantitative polymerase chain reaction. Results: The number of bulls infected with T. orientalis Ikeda at initial delivery to the stations increased significantly over the years studied. Multivariable linear regression models, using Angus bulls from Virginia test stations, indicated no significant effect on ADG or AYW in bulls that became test positive during the test or were positive for the duration, compared to Angus bulls that were negative for the duration. At LOC A, the odds of passing a breeding soundness exam (BSE) were not significantly different for bulls that turned positive during the test or were positive for the duration, compared to bulls that were negative for the duration of the test. At LOC B, bulls that became positive during the test were 2.4 times more likely (95% CI: 1.165-4.995, p = 0.016) to pass their BSE compared to bulls that remained negative throughout the test. Discussion: We do not suppose that an obscured infection of T. orientalis Ikeda is protective for bulls to pass a BSE. However, this study demonstrates an obscured infection of T. orientalis Ikeda does not negatively affect weight gain or achievement of a satisfactory BSE rating at the central bull test stations in Virginia.

Theileria orientalis Ikeda in Cattle, Alabama, USA.

Theileria orientalis Ikeda genotype, a parasite causing a disease in cattle that leads to significant economic challenges in Asia, New Zealand, and Australia, has been identified in seven U.S. States since 2017. Two previously validated PCR tests for Theileria followed by DNA sequencing were performed to test blood samples collected from 219 cattle in Alabama, USA, during the period of 2022-2023. Bidirectional Sanger sequencing revealed that the MPSP gene sequences (639-660 bp) from two cattle in Lee and Mobile Counties of Alabama exhibited a 100% match with those of recognized T. orientalis Ikeda strains, and showed similarities ranging from 76% to 88% with ten other T. orientalis genotypes. A high copy number of T. orientalis Ikeda was detected in the blood of infected cattle (ALP-1: 1.7 × 105 and 1.3 × 106/mL whole blood, six months apart; ALP-2: 7.1 × 106/mL whole blood). Although the confirmed competent vector for T. orientalis Ikeda, Haemaphysalis longicornis tick, has not yet been identified in Alabama, the persistent nature of T. orientalis Ikeda infection and the detection of a high pathogen burden in seemingly healthy cattle in this study suggest that other tick species, as well as shared needles and dehorning procedures, could facilitate pathogen transmission within the herd. Continued investigations are necessary for the surveillance of T. orientalis Ikeda and Haemaphysalis longicornis ticks in Alabama and other U.S. states, along with assessing the pathogenicity of T. orientalis Ikeda infections in cattle.

Distribution of Theileria orientalis in Virginia Market Cattle, 2018-2020.

Theileria orientalis, genotype Ikeda, was recently detected in North America. Determining the emerging distribution of this pathogen is critical for understanding spread and developing management strategies. Whole blood samples were collected from cattle at Virginia livestock markets from September 2018 through December 2020. Animals were tested for T. orientalis using a universal and then genotype specific real-time PCR based on the MPSP gene. Prevalence for each genotype was analyzed for temporal trends and mapped by county. Spatial patterns were compared between genotypes and assessed for associations with habitat features, cattle movements through cattle markets and county proximity. Overall, 212 of 1980 samples tested positive for T. orientalis with an overall prevalence of 8.7% (172/1980) for genotype Ikeda, 1.8% (36/1980) for genotype Chitose, 0.2% (3/1980) for genotype Buffeli. The Ikeda genotype increased over time in northern and southwestern Virginia markets. The Ikeda and Chitose genotypes occurred in different regions, with little overlap, but for each genotype, spatial distribution was associated with a combination of cattle movements and environmental factors. Genotype specific qPCR testing and surveillance of cattle from across a wide area of Virginia are providing information on temporal, spatial, and other patterns for this emerging disease.

Coinfection of cattle in Virginia with Theileria orientalis Ikeda genotype and Anaplasma marginale.

Theileria orientalis Ikeda is a newly identified agent of bovine infectious anemia in the United States. Although T. orientalis Ikeda is transmitted by ticks other than the tick that transmits Anaplasma marginale-a bacterial etiology of bovine infectious anemia-the geographic distributions of these 2 infectious organisms overlap, with coinfection reported in some cattle. Only anaplasmosis has an approved effective treatment in the United States. To provide rapid diagnostic information for producers with anemic animals, we developed a duplex real-time PCR (rtPCR) for A. marginale and T. orientalis. With a cutoff of 38 cycles, the duplex assay has a sensitivity of 97.0% and a specificity of 100% for A. marginale; with a cutoff of 45 cycles, the duplex assay has a sensitivity and a specificity of 100% for T. orientalis, compared to existing tests. In addition to providing a tool for improved clinical decision-making for veterinarians and producers, our rtPCR facilitates the study of coinfection of cattle in Virginia. Of 1,359 blood samples analyzed, 174 were positive for T. orientalis, 125 were positive for A. marginale, and 12 samples were positive for both T. orientalis and A. marginale. Hence, coinfection by these 2 agents of bovine infectious anemia does occur within Virginia. It is likely that this pattern of infection will be seen in other regions where T. orientalis and A. marginale infections are endemic, despite the difference in tick vectors.

A longitudinal study of infection with genotypes of Theileria orientalis in calves and introduced cattle at Dorrigo, New South Wales, and the effect on weight gains.

BACKGROUND: In regions with endemic Theileria orientalis, recovered cattle are carriers, leaving newborn calves and introduced stock as the most susceptible groups to develop clinical disease after tick infestation with parasite transmission. METHODS: To gain information on the kinetics of infection and development and effects of theileriosis caused by virulent ikeda and chitose genotypes and the "benign" buffeli genotype of T.orientalis, this study sampled a total of 134 calves from 3 farms in Dorrigo, Australia, a region with multiple genotypes of the parasite. In addition, 30 introduced beef weaners were bled and weighed for 6 months after arrival. RESULTS: In both cohorts, parasitaemia with the ikeda and chitose (genotypes 1 & 2) of T.orientalis was detectable by PCR within 3-4 weeks in >95 % of the groups, with maximal gene copies generated around 5-7 weeks after birth or introduction, before declining. In contrast, parasitaemias of T.orientalis buffeli (genotype 3), increased slowly, with around 80 % of the population testing positive by PCR after 4 months. The parasitaemias of the buffeli genotype did not exceed 40,000 gene copies /ul and were similar to those exhibited by ikeda and chitose genotypes following the "first wave of parasitaemia" as cattle entered the carrier state. In the 30 introduced weaners, the early infection with T.orientalis ikeda and chitose also caused significant reductions in packed cell volume (PCV) and incurred an estimated 20Kg loss in weight gain; the latter had not been recovered by 6 months after introduction. CONCLUSIONS: The results support previous findings in other endemic regions of theileriosis, and imply that amelioration of the early high levels of parasitosis by the virulent genotypes could reduce the initial impact of theileriosis on production, which appears much less affected once animals enter the carrier state.

The role of sheep (Ovis aries) in maintaining Theileria orientalis Ikeda type infection.

Theileria orientalis is a tick‒borne intracellular parasite of red blood cells that causes severe and mild infections in various ruminants worldwide. To date there have been 11 types identified within this species, of which 4 types are presently found in New Zealand cattle. Since 2012, New Zealand has suffered a substantial epidemic of infectious bovine anaemia in both dairy and beef cattle associated with the Ikeda type. The speed at which the disease spread through the North Island suggested that other species could have been involved in transmission. The aim of a series of related experiments was to test the null hypothesis that sheep cannot maintain T. orientalis Ikeda type infection or infect ticks that feed on them. Several studies were conducted over 2 years to address this hypothesis which together showed that sheep can have detectable levels of T. orientalis Ikeda type infection in both the acute and chronic phase and that Haemaphysalis longicornis larvae can become infected when feeding on sheep. No anaemia, weight loss or clinical disease was recorded in the sheep in the acute phase of infection. The levels of infection recorded in the sheep were much lower than those found in cattle, consistent with the sheep being asymptomatic carriers of T. orientalis Ikeda type infection.

Review of the New Zealand Theileria orientalis Ikeda Type Epidemic and Epidemiological Research since 2012.

This article sets out to document and summarise the New Zealand epidemic and the epidemiological research conducted on the epizootic of bovine anaemia associated with Theileria orientalis Ikeda type infection, which began in New Zealand in August 2012. As New Zealand has no other pathogenic tick-borne cattle haemoparasites, the effects of the T. orientalis Ikeda type infection observed in affected herds and individual animals were not confounded by other concurrent haemoparasite infections, as was possibly the case in other countries. This has resulted in an unbiased perspective of a new disease. In addition, as both New Zealand's beef and dairy cattle systems are seasonally based, this has led to a different epidemiological presentation than that reported by almost all other affected countries. Having verified the establishment of a new disease and identified the associated pathogen, the remaining key requirements of an epidemiological investigation, for a disease affecting production animals, are to describe how the disease spreads, describe the likely impacts of that disease at the individual and herd level and explore methods of disease control or mitigation.

A U.S. isolate of Theileria orientalis, Ikeda genotype, is transmitted to cattle by the invasive Asian longhorned tick, Haemaphysalis longicornis.

BACKGROUND: Theileria orientalis is a tick-borne hemoparasite that causes anemia, ill thrift, and death in cattle globally. The Ikeda strain of T. orientalis is more virulent than other strains, leading to severe clinical signs and death of up to 5% of affected animals. Within the Asia-Pacific region, where it affects 25% of Australian cattle, T. orientalis Ikeda has a significant economic impact on the cattle industry. In 2017, T. orientalis Ikeda was detected in a cattle herd in Albermarle County, Virginia, United States. Months earlier, the U.S. was alerted to the invasion of the Asian longhorned tick, Haemaphysalis longicornis, throughout the eastern U.S. Abundant H. longicornis ticks were identified on cattle in the T. orientalis-affected herd in VA, and a subset of ticks from the environment were PCR-positive for T. orientalis Ikeda. A strain of T. orientalis from a previous U.S. outbreak was not transmissible by H. longicornis; however, H. longicornis is the primary tick vector of T. orientalis Ikeda in other regions of the world. Thus, the objective of this study was to determine whether invasive H. longicornis ticks in the U.S. are competent vectors of T. orientalis Ikeda. METHODS: Nymphal H. longicornis ticks were fed on a splenectomized calf infected with the VA-U.S.-T. orientalis Ikeda strain. After molting, a subset of adult ticks from this cohort were dissected, and salivary glands assayed for T. orientalis Ikeda via qPCR. The remaining adult ticks from the group were allowed to feed on three calves. Calves were subsequently monitored for T. orientalis Ikeda infection via blood smear cytology and PCR. RESULTS: After acquisition feeding on a VA-U.S.-T. orientalis Ikeda-infected calf as nymphs, a subset of molted adult tick salivary glands tested positive by qPCR for T. orientalis Ikeda. Adult ticks from the same cohort successfully transmitted T. orientalis Ikeda to 3/3 naïve calves, each of which developed parasitemia reaching 0.4-0.9%. CONCLUSIONS: Our findings demonstrate that U.S. H. longicornis ticks are competent vectors of the VA-U.S.-T. orientalis Ikeda strain. This data provides important information for the U.S. cattle industry regarding the potential spread of this parasite and the necessity of enhanced surveillance and control measures.

Merozoites of Theileria orientalis buffeli reduce the parasitaemia of T. orientalis ikeda following tick challenge.

Theileria orientalis is a tick-borne protozoal parasite causing anaemia and death in susceptible cattle. This investigation aimed to confirm whether immunisation with the "benign" buffeli genotype of T. orientalis could reduce the parasitaemia of the virulent ikeda genotype. Calves were inoculated intravenously or subcutaneously with bovine blood containing merozoites of T. orientalis buffeli and when recipients became positive by PCR, they and control calves were challenged with unfed nymphs of Haemaphysalis longicornis ticks infected as larvae with T. orientalis ikeda. All calves became positive for the challenge within 12 days after tick application. In the immunised calves, the first wave of parasitaemia with T. orientalis ikeda from 4 to 6 weeks was reduced significantly by >80 % before the parasite burden declined into the carrier state by 9 weeks. The parasitaemias in two calves which exhibited low infections with T. orientalis ikeda shortly after arrival, were also significantly reduced after tick challenge. The results confirm the previous studies on immunity to T. sergenti in Japan, and field experience with theileriosis in endemic zones where the carrier state appears to prevent clinical disease despite repeated, seasonal tick infestations with virulent genotypes of the parasite. This method offers a means to reduce the severity of the first wave of theilerial parasitaemia after tick challenge and possibly recover associated production losses.