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.

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.

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.

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.

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.