title: Development and validation of a quantitative PCR assay using multiplexed hydrolysis probes for detection and quantification of Theileria orientalis isolates and differentiation of clinically relevant subtypes.
abstract: Theileria orientalis is an emerging pathogen of cattle in Asia, Australia, and New Zealand. This organism is a vector-borne hemoprotozoan that causes clinical disease characterized by anemia, abortion, and death, as well as persistent subclinical infections. Molecular methods of diagnosis are preferred due to their sensitivity and utility in differentiating between pathogenic and apathogenic genotypes. Conventional PCR (cPCR) assays for T. orientalis detection and typing are laborious and do not provide an estimate of parasite load. Current real-time PCR assays cannot differentiate between clinically relevant and benign genotypes or are only semiquantitative without a defined clinical threshold. Here, we developed and validated a hydrolysis probe quantitative PCR (qPCR) assay which universally detects and quantifies T. orientalis and identifies the clinically associated Ikeda and Chitose genotypes (UIC assay). Comparison of the UIC assay results with previously validated universal and genotype-specific cPCR results demonstrated that qPCR detects and differentiates T. orientalis with high sensitivity and specificiy. Comparison of quantitative results based on percent parasitemia, determined via blood film analysis and packed cell volume (PCV) revealed significant positive and negative correlations, respectively. One-way analysis of variance (ANOVA) indicated that blood samples from animals with clinical signs of disease contained statistically higher concentrations of T. orientalis DNA than animals with subclinical infections. We propose clinical thresholds to assist in classifying high-, moderate-, and low-level infections and describe how parasite load and the presence of the Ikeda and Chitose genotypes relate to disease.
authors.affiliation: ithree institute, University of Technology, Sydney, Ultimo, NSW, Australia Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, NSW, Australia.
authors.forename: D R
authors.initials: DR
authors.lastname: Bogema
authors.affiliation: Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, NSW, Australia.
authors.forename: A T
authors.initials: AT
authors.lastname: Deutscher
authors.affiliation: Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, NSW, Australia.
authors.forename: S
authors.initials: S
authors.lastname: Fell
authors.affiliation: Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, NSW, Australia.
authors.forename: D
authors.initials: D
authors.lastname: Collins
authors.affiliation: Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, NSW, Australia.
authors.forename: G J
authors.initials: GJ
authors.lastname: Eamens
authors.affiliation: ithree institute, University of Technology, Sydney, Ultimo, NSW, Australia Elizabeth Macarthur Agricultural Institute, NSW Department of Primary Industries, Menangle, NSW, Australia cheryl.jenkins@dpi.nsw.gov.au.
authors.forename: C
authors.initials: C
authors.lastname: Jenkins
mesh_terms: D000818:Animals; D001208:Asia; D001315:Australia; D001769:Blood / Q000469:parasitology; D002417:Cattle; D002418:Cattle Diseases / Q000175:diagnosis* / Q000469:parasitology; D008969:Molecular Sequence Data; D009520:New Zealand; D015345:Oligonucleotide Probes / Q000235:genetics; D059208:Parasite Load / Q000379:methods*; D060888:Real-Time Polymerase Chain Reaction / Q000379:methods*; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D016794:Theileria / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D013801:Theileriasis / Q000175:diagnosis* / Q000469:parasitology
chemical_list: D015345:Oligonucleotide Probes