{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,3]],"date-time":"2026-08-03T16:21:10Z","timestamp":1785774070851,"version":"3.56.0"},"reference-count":54,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T00:00:00Z","timestamp":1775779200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["frontiersin.org"],"crossmark-restriction":true},"short-container-title":["Front. Vet. Sci."],"abstract":"<jats:sec>\n                    <jats:title>Introduction<\/jats:title>\n                    <jats:p>\n                      The emergence of the tick-borne Ikeda genotype of\n                      <jats:italic>Theileria orientalis<\/jats:italic>\n                      poses a significant threat to the U.S. cattle industry. Although information has been gathered on parasite distribution, data regarding the pathogenicity of the U.S. isolate of Ikeda remain to be elucidated. In this study, we evaluated the effect of the U.S. Ikeda isolate on cattle experimentally infected with sporozoites, the parasite stage naturally transmitted by ticks.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Methods<\/jats:title>\n                    <jats:p>\n                      Six spleen-intact Holstein calves, aged 6\u201312\u202fmonths, were subcutaneously inoculated with 1-mL stabilate containing 3.8\u202f\u00d7\u202f10\u2075 of\n                      <jats:italic>T. orientalis<\/jats:italic>\n                      Ikeda sporozoites. Parasite load, temperature, hematocrit, blood cell counts, and serology were monitored. For this study, we defined acute infection as occurring up to 8\u202fweeks post-inoculation (WPI) and chronic infection as occurring from weeks 10\u201320. Parasite load was quantified by qPCR targeting the major piroplasm surface protein (MPSP) gene. Hematological parameters were evaluated using a veterinary hematology analyzer. IgM, total IgG, IgG1, and IgG2 profiles were determined by an MPSP-based indirect ELISA.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Results<\/jats:title>\n                    <jats:p>\n                      Parasite load in peripheral blood varied markedly among animals and peaked at 8 WPI (average of 27,078 parasites\/\u03bcl). A substantial number of parasites were also detected in peripheral blood during the chronic phase (average of 931 parasites\/\u03bcl). The results demonstrated a significant inverse correlation during the acute phase between parasite load and both hematocrit (\n                      <jats:italic>p<\/jats:italic>\n                      \u202f=\u202f0.004;\n                      <jats:italic>r<\/jats:italic>\n                      \u202f=\u202f\u22120.8703) and total erythrocyte count (\n                      <jats:italic>p<\/jats:italic>\n                      \u202f=\u202f0.001;\n                      <jats:italic>r<\/jats:italic>\n                      \u202f=\u202f\u22120.9205). However, no significant correlation was found between parasite load and changes in hematocrit or erythrocyte count during the chronic phase. Lymphocyte, neutrophil, and monocyte counts remained within physiological ranges throughout infection. Anti-MPSP IgM was detected at 2 WPI and peaked at 4 WPI, while total IgG appeared at 2 WPI, peaked at 6 WPI, and persisted during the chronic phase. Anti-MPSP IgG1 and IgG2 were detectable from 4 WPI onward, with no significant differences between subclasses.\n                    <\/jats:p>\n                  <\/jats:sec>\n                  <jats:sec>\n                    <jats:title>Conclusion<\/jats:title>\n                    <jats:p>\n                      Acute infection with the U.S. isolate of\n                      <jats:italic>T. orientalis<\/jats:italic>\n                      Ikeda was correlated with reduced hematocrit and erythrocyte count in peripheral blood. Infected cattle exhibited robust anti-MPSP antibody responses during the acute phase, which maintained throughout chronic infection.\n                    <\/jats:p>\n                  <\/jats:sec>","DOI":"10.3389\/fvets.2026.1768408","type":"journal-article","created":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T04:26:26Z","timestamp":1775795186000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":1,"title":["Acute infection with the U.S. isolate of Theileria orientalis genotype Ikeda is associated with decreased hematocrit and erythrocyte counts in experimentally infected cattle"],"prefix":"10.3389","volume":"13","author":[{"given":"Cynthia K.","family":"Onzere","sequence":"first","affiliation":[{"name":"Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University","place":["Pullman, WA, United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Eun-Jee","family":"Na","sequence":"additional","affiliation":[{"name":"Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University","place":["Pullman, WA, United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"David R.","family":"Herndon","sequence":"additional","affiliation":[{"name":"Animal Disease Research Unit, USDA-ARS","place":["Pullman, WA, United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Lowell S.","family":"Kappmeyer","sequence":"additional","affiliation":[{"name":"Animal Disease Research Unit, USDA-ARS","place":["Pullman, WA, United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Chungwon J.","family":"Chung","sequence":"additional","affiliation":[{"name":"Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University","place":["Pullman, WA, United States"]},{"name":"Animal Disease Research Unit, USDA-ARS","place":["Pullman, WA, United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Reginaldo G.","family":"Bastos","sequence":"additional","affiliation":[{"name":"Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University","place":["Pullman, WA, United States"]},{"name":"Animal Disease Research Unit, USDA-ARS","place":["Pullman, WA, United States"]}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1965","published-online":{"date-parts":[[2026,4,10]]},"reference":[{"key":"ref1","doi-asserted-by":"publisher","first-page":"3","DOI":"10.1080\/00480169.2015.1064792","article-title":"Theileria orientalis: a review","volume":"64","author":"Watts","year":"2016","journal-title":"N Z Vet J"},{"key":"ref2","doi-asserted-by":"publisher","DOI":"10.3390\/pathogens10091153","article-title":"Approaches to integrated parasite management (IPM) for Theileria orientalis with an emphasis on immunity","volume":"10","author":"Emery","year":"2021","journal-title":"Pathogens (Basel, Switzerland)"},{"key":"ref3","doi-asserted-by":"publisher","DOI":"10.3390\/pathogens10101346","article-title":"Review of the New Zealand Theileria orientalis Ikeda type epidemic and epidemiological research since 2012","volume":"10","author":"Lawrence","year":"2021","journal-title":"Pathogens (Basel, Switzerland)"},{"key":"ref4","doi-asserted-by":"publisher","first-page":"250","DOI":"10.1016\/j.meegid.2014.07.013","article-title":"Evolution and genetic diversity of Theileria","volume":"27","author":"Sivakumar","year":"2014","journal-title":"Infect Genet Evol"},{"key":"ref5","doi-asserted-by":"publisher","first-page":"51","DOI":"10.1186\/s13028-017-0318-8","article-title":"Pathogenic genotype of major piroplasm surface protein associated with anemia in Theileria orientalis infection in cattle","volume":"59","author":"Kim","year":"2017","journal-title":"Acta Vet Scand"},{"key":"ref6","doi-asserted-by":"publisher","first-page":"103038","DOI":"10.1016\/j.parint.2025.103038","article-title":"Genetic diversity and phylogeography of the global Theileria orientalis isolates inferred from MPSP gene sequences","volume":"106","author":"El-Alfy","year":"2025","journal-title":"Parasitol Int"},{"key":"ref7","doi-asserted-by":"publisher","first-page":"937","DOI":"10.1292\/jvms.71.937","article-title":"Epidemiological survey of Theileria orientalis infection in grazing cattle in the eastern part of Hokkaido, Japan","volume":"71","author":"Ota","year":"2009","journal-title":"J Vet Med Sci"},{"key":"ref8","doi-asserted-by":"publisher","DOI":"10.3390\/pathogens12101187","article-title":"Epidemiology and transmission of Theileria orientalis in Australasia","volume":"12","author":"Lakew","year":"2023","journal-title":"Pathogens (Basel, Switzerland)"},{"key":"ref9","doi-asserted-by":"publisher","first-page":"1653","DOI":"10.3201\/eid2509.190088","article-title":"Theileria orientalis Ikeda genotype in cattle, Virginia, USA","volume":"25","author":"Oakes","year":"2019","journal-title":"Emerg Infect Dis"},{"key":"ref10","doi-asserted-by":"publisher","first-page":"1310","DOI":"10.15585\/mmwr.mm6747a3","article-title":"Multistate infestation with the exotic disease-vector tick Haemaphysalis longicornis - United States, august 2017-September 2018","volume":"67","author":"Beard","year":"2018","journal-title":"MMWR Morb Mortal Wkly Rep"},{"key":"ref11","doi-asserted-by":"publisher","first-page":"757","DOI":"10.1093\/jme\/tjy006","article-title":"Discovery of Haemaphysalis longicornis (Ixodida: Ixodidae) parasitizing a sheep in New Jersey, United States","volume":"55","author":"Rainey","year":"2018","journal-title":"J Med Entomol"},{"key":"ref12","doi-asserted-by":"publisher","first-page":"157","DOI":"10.1186\/s13071-021-04659-9","article-title":"A U.S. isolate of Theileria orientalis, Ikeda genotype, is transmitted to cattle by the invasive Asian longhorned tick, Haemaphysalis longicornis","volume":"14","author":"Dinkel","year":"2021","journal-title":"Parasit Vectors"},{"key":"ref13","year":"2025"},{"key":"ref14","year":""},{"key":"ref15","doi-asserted-by":"publisher","first-page":"101279","DOI":"10.1016\/j.vprsr.2025.101279","article-title":"First report of Theileria orientalis Ikeda genotype associated with disease in cattle, Georgia, USA","volume":"62","author":"Maboni","year":"2025","journal-title":"Vet Parasitol Reg Stud Rep"},{"key":"ref16","doi-asserted-by":"publisher","first-page":"e0319327","DOI":"10.1371\/journal.pone.0319327","article-title":"Active surveillance for Theileria orientalis and the invasive Asian longhorned tick (Haemaphysalis longicornis) in three Missouri beef herds","volume":"20","author":"Ierardi","year":"2025","journal-title":"PLoS One"},{"key":"ref17","doi-asserted-by":"publisher","DOI":"10.3390\/pathogens13100861","article-title":"First report of Haemaphysalis longicornis (Neumann) in Oklahoma, USA","volume":"13","author":"Myers","year":"2024","journal-title":"Pathogens"},{"key":"ref18","doi-asserted-by":"publisher","first-page":"217","DOI":"10.1080\/00034983.1993.11812757","article-title":"Theileria sergenti: experimental transmission by the long-nosed cattle louse, Linognathus vituli","volume":"87","author":"Fujisaki","year":"1993","journal-title":"Ann Trop Med Parasitol"},{"key":"ref19","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1016\/j.vetpar.2018.09.017","article-title":"Evaluation of the natural vertical transmission of Theileria orientalis","volume":"263","author":"Mekata","year":"2018","journal-title":"Vet Parasitol"},{"key":"ref20","doi-asserted-by":"publisher","first-page":"34","DOI":"10.1186\/s13071-016-1323-x","article-title":"Mechanical transfer of Theileria orientalis: possible roles of biting arthropods, colostrum and husbandry practices in disease transmission","volume":"9","author":"Hammer","year":"2016","journal-title":"Parasit Vectors"},{"key":"ref21","doi-asserted-by":"publisher","first-page":"109516","DOI":"10.1080\/00480169.2015.1064792","article-title":"Detection and distribution of haematophagous flies and lice on cattle farms and potential role in the transmission of Theileria orientalis","volume":"298","author":"Lakew","year":"2021","journal-title":"Vet Parasitol"},{"key":"ref22","doi-asserted-by":"publisher","first-page":"1","DOI":"10.1146\/annurev.micro.53.1.1","article-title":"Transformation of leukocytes by Theileria parva and T. annulata","volume":"53","author":"Dobbelaere","year":"1999","journal-title":"Ann Rev Microbiol"},{"key":"ref23","doi-asserted-by":"publisher","first-page":"7312","DOI":"10.1073\/pnas.96.13.7312","article-title":"The intracellular parasite Theileria parva protects infected T cells from apoptosis","volume":"96","author":"Heussler","year":"1999","journal-title":"Proc Natl Acad Sci USA"},{"key":"ref24","doi-asserted-by":"publisher","first-page":"549","DOI":"10.1016\/j.ttbdis.2016.02.001","article-title":"The biology of Theileria parva and control of East Coast fever - current status and future trends","volume":"7","author":"Nene","year":"2016","journal-title":"Ticks Tick Borne Dis"},{"key":"ref25","doi-asserted-by":"publisher","first-page":"378","DOI":"10.1038\/nature14044","article-title":"Theileria parasites secrete a prolyl isomerase to maintain host leukocyte transformation","volume":"520","author":"Marsolier","year":"2015","journal-title":"Nature"},{"key":"ref26","doi-asserted-by":"publisher","first-page":"679","DOI":"10.1016\/j.ijpara.2018.03.010","article-title":"Discovery of a novel species, Theileria haneyi n. sp., infective to equids, highlights exceptional genomic diversity within the genus Theileria: implications for apicomplexan parasite surveillance","volume":"48","author":"Knowles","year":"2018","journal-title":"Int J Parasitol"},{"key":"ref27","doi-asserted-by":"publisher","first-page":"68","DOI":"10.1016\/j.vetpar.2019.06.009","article-title":"Infection dynamics of Theileria equi and Theileria haneyi, a newly discovered apicomplexan of the horse","volume":"271","author":"Sears","year":"2019","journal-title":"Vet Parasitol"},{"key":"ref28","doi-asserted-by":"publisher","DOI":"10.3390\/pathogens11020254","article-title":"Clinical progression of Theileria haneyi in splenectomized horses reveals decreased virulence compared to Theileria equi","volume":"11","author":"Sears","year":"2022","journal-title":"Pathogens"},{"key":"ref29","doi-asserted-by":"publisher","first-page":"1370255","DOI":"10.3389\/fimmu.2024.1370255","article-title":"Expression of IL-10 and TGF-\u03b21 in horses experimentally infected with Theileria equi merozoites is associated with antibody production but not modulation of pro-inflammatory responses","volume":"15","author":"Onzere","year":"2024","journal-title":"Front Immunol"},{"key":"ref30","doi-asserted-by":"publisher","first-page":"332","DOI":"10.1111\/avj.12078","article-title":"Distribution and temporal prevalence of Theileria orientalis major piroplasm surface protein types in eastern Australian cattle herds","volume":"91","author":"Eamens","year":"2013","journal-title":"Aust Vet J"},{"key":"ref31","doi-asserted-by":"publisher","first-page":"96","DOI":"10.1016\/j.vetpar.2012.12.059","article-title":"Significance of Theileria orientalis types in individual affected beef herds in New South Wales based on clinical, smear and PCR findings","volume":"196","author":"Eamens","year":"2013","journal-title":"Vet Parasitol"},{"key":"ref32","doi-asserted-by":"publisher","first-page":"306","DOI":"10.1016\/j.ttbdis.2015.11.006","article-title":"Production and dose determination of the infection and treatment method (ITM) Muguga cocktail vaccine used to control East Coast fever in cattle","volume":"7","author":"Patel","year":"2016","journal-title":"Ticks Tick Borne Dis"},{"key":"ref33","doi-asserted-by":"publisher","first-page":"1421710","DOI":"10.3389\/fvets.2024.1421710","article-title":"Transient efficacy of buparvaquone against the US isolate of Theileria orientalis Ikeda genotype in sub-clinically infected cattle","volume":"11","author":"Bastos","year":"2024","journal-title":"Front Vet Sci."},{"key":"ref34","doi-asserted-by":"publisher","DOI":"10.3390\/pathogens12040559","article-title":"A U.S. isolate of Theileria orientalis Ikeda is not transstadially transmitted to cattle by Rhipicephalus microplus","volume":"12","author":"Onzere","year":"2023","journal-title":"Pathogens (Basel, Switzerland)"},{"key":"ref35","doi-asserted-by":"publisher","DOI":"10.3390\/vetsci10110638","article-title":"Theileria orientalis Ikeda in cattle, Alabama, USA","volume":"10","author":"Iduu","year":"2023","journal-title":"Vet Sci"},{"key":"ref36","doi-asserted-by":"publisher","first-page":"101508","DOI":"10.1016\/j.ttbdis.2020.101508","article-title":"Infection dynamics of Theileria equi in carrier horses is associated with management and tick exposure","volume":"11","author":"Tirosh-Levy","year":"2020","journal-title":"Ticks Tick Borne Dis"},{"key":"ref37","doi-asserted-by":"publisher","first-page":"277","DOI":"10.1007\/s11250-024-04138-0","article-title":"Identification of novel bovine leukocyte antigen alleles and association of BoLA-DRB3.2*020:02:01 with resistance to Theileria orientalis infection in crossbred Kedah-Kelantan cattle: a pilot study","volume":"56","author":"Agina","year":"2024","journal-title":"Trop Anim Health Prod"},{"key":"ref38","doi-asserted-by":"publisher","first-page":"298","DOI":"10.1186\/s12864-018-4701-2","article-title":"Analysis of Theileria orientalis draft genome sequences reveals potential species-level divergence of the Ikeda, Chitose and Buffeli genotypes","volume":"19","author":"Bogema","year":"2018","journal-title":"BMC Genomics"},{"key":"ref39","doi-asserted-by":"publisher","first-page":"1261","DOI":"10.1093\/jme\/tjae090","article-title":"New report of Haemaphysalis longicornis (Ixodida: Ixodidae) in Mecklenburg County, Virginia from field collections","volume":"61","author":"Adams","year":"2024","journal-title":"J Med Entomol"},{"key":"ref40","doi-asserted-by":"publisher","first-page":"1071","DOI":"10.1093\/jme\/tjae051","article-title":"Surveillance and detection of Haemaphysalis longicornis (Acari: Ixodidae) in protected areas from Georgia, USA","volume":"61","author":"Fausett","year":"2024","journal-title":"J Med Entomol"},{"key":"ref41","doi-asserted-by":"publisher","first-page":"e0292595","DOI":"10.1371\/journal.pone.0292595","article-title":"Environmental variables serve as predictors of the invasive Asian longhorned tick (Haemaphysalis longicornis Neumann): an approach for targeted tick surveillance","volume":"18","author":"Trout Fryxell","year":"2023","journal-title":"PLoS One"},{"key":"ref42","doi-asserted-by":"publisher","first-page":"1374","DOI":"10.1093\/jme\/tjad121","article-title":"Management of Haemaphysalis longicornis (Acari: Ixodidae) on a cow-calf farm in East Tennessee, USA","volume":"60","author":"Butler","year":"2023","journal-title":"J Med Entomol"},{"key":"ref43","doi-asserted-by":"publisher","first-page":"1398","DOI":"10.1093\/jme\/tjad119","article-title":"Invasive Haemaphysalis longicornis (Acari: Ixodidae) investigation in South Carolina: new records of establishment, pathogen prevalence, and blood meal analyses","volume":"60","author":"Dye-Braumuller","year":"2023","journal-title":"J Med Entomol"},{"key":"ref44","doi-asserted-by":"publisher","DOI":"10.3390\/pathogens10060650","article-title":"Effects of Theileria orientalis infection on health status and productivity of dairy cows reared inside barns","volume":"10","author":"Fukushima","year":"2021","journal-title":"Pathogens"},{"key":"ref45","doi-asserted-by":"publisher","first-page":"1045608","DOI":"10.3389\/fimmu.2022.1045608","article-title":"Identification of novel immune correlates of protection against acute bovine babesiosis by superinfecting cattle with in vitro culture attenuated and virulent Babesia bovis strains","volume":"13","author":"Bastos","year":"2022","journal-title":"Front Immunol"},{"key":"ref46","doi-asserted-by":"publisher","first-page":"1219913","DOI":"10.3389\/fimmu.2023.1219913","article-title":"Vaccination with an in vitro culture attenuated Babesia bovis strain safely protects highly susceptible adult cattle against acute bovine babesiosis","volume":"14","author":"Bastos","year":"2023","journal-title":"Front Immunol"},{"key":"ref47","doi-asserted-by":"publisher","first-page":"e00703-19","DOI":"10.1128\/IAI.00703-19","article-title":"Changes in the molecular and functional phenotype of bovine monocytes during Theileria parva infection","volume":"87","author":"Bastos","year":"2019","journal-title":"Infect Immun"},{"key":"ref48","doi-asserted-by":"publisher","first-page":"73","DOI":"10.1186\/1756-3305-7-73","article-title":"Oriental theileriosis in dairy cows causes a significant milk production loss","volume":"7","author":"Perera","year":"2014","journal-title":"Parasit Vectors"},{"key":"ref49","doi-asserted-by":"publisher","first-page":"1432228","DOI":"10.3389\/fvets.2024.1432228","article-title":"Theileria orientalis Ikeda infection does not negatively impact growth performance or breeding soundness exam results in young beef bulls at bull test stations","volume":"11","author":"Guynn","year":"2024","journal-title":"Front Vet Sci"},{"key":"ref50","doi-asserted-by":"publisher","first-page":"275","DOI":"10.1292\/jvms.61.275","article-title":"Expression of a major piroplasm surface protein of Theileria sergenti in sporozoite stage","volume":"61","author":"Sako","year":"1999","journal-title":"J Vet Med Sci"},{"key":"ref51","doi-asserted-by":"publisher","first-page":"106","DOI":"10.1186\/s13071-016-1395-7","article-title":"Factors associated with seroconversion to the major piroplasm surface protein of the bovine haemoparasite Theileria orientalis","volume":"9","author":"Jenkins","year":"2016","journal-title":"Parasit Vectors"},{"key":"ref52","first-page":"249","article-title":"Functional properties of bovine IgG1 and IgG2: interaction with complement, macrophages, neutrophils and skin","volume":"38","author":"McGuire","year":"1979","journal-title":"Immunology"},{"key":"ref53","doi-asserted-by":"publisher","first-page":"32","DOI":"10.1111\/j.1365-3083.2006.01865.x","article-title":"Structural evidence for a new IgG1 antibody sequence allele of cattle","volume":"65","author":"Saini","year":"2007","journal-title":"Scand J Immunol"},{"key":"ref54","doi-asserted-by":"publisher","first-page":"241","DOI":"10.1016\/j.cimid.2011.12.002","article-title":"Adaptive immunity to Anaplasma pathogens and immune dysregulation: implications for bacterial persistence","volume":"35","author":"Brown","year":"2012","journal-title":"Comp Immunol Microbiol Infect Dis"}],"container-title":["Frontiers in Veterinary Science"],"original-title":[],"link":[{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fvets.2026.1768408\/full","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,4,10]],"date-time":"2026-04-10T04:26:27Z","timestamp":1775795187000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.frontiersin.org\/articles\/10.3389\/fvets.2026.1768408\/full"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,4,10]]},"references-count":54,"alternative-id":["10.3389\/fvets.2026.1768408"],"URL":"https:\/\/doi.org\/10.3389\/fvets.2026.1768408","relation":{},"ISSN":["2297-1769"],"issn-type":[{"value":"2297-1769","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,4,10]]},"article-number":"1768408"}}