Location: Animal Disease Research
Project Number: 2090-32000-040-015-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Jul 1, 2020
End Date: Jun 30, 2025
Theileriosis causes significant economic losses to both cattle and horses. Losses are due to morbidity, mortality, and in the case of horses, the loss of the ability to move internationally. Three recent events have led to the need for a collaborative research initiative to protect U.S. livestock from further economic disadvantage. These events are the introduction of Theileria orientalis into the U. S., the discovery of the new species, Theileria haneyi (in horses) and the fact that T. haneyi can't be eliminated from horses by imidocarb diproprionate (ID) as is the case for T. equi. The objective of this collaborative work is to develop informative diagnostic assays and new preventative and treatment strategies for theileriosis in cattle and horses. The objectives for this research are: 1) Develop and technically transfer diagnostic tests that differentiate infections of T. haneyi and T. equi, and use those assays to perform T. haneyi prevalence studies within the U.S.; 2) Test the efficacy of currently approved and experimental drugs against T. haneyi; 3) Identify potential diagnostic and subunit vaccine targets for T. orientalis Ikeda (2016 VA-U.S. isolate); and 4) Provide more complete characterization of the pathogenesis of U.S. Theileria spp within horses and cattle.
1) Develop and technically transfer diagnostic tests that differentiate infections of T. haneyi and T. equi, and use those assays to perform T. haneyi prevalence studies within the U.S.: The cooperator published data demonstrating comparative antibody responses to homologous and heterologous antigens of T. equi and T. haneyi in horses. This information, in combination with the annotated genome of T. haneyi, will be used to identify targets for development of molecular and serologic assays that identify horses infected with T. haneyi. Equine blood and serum banks will be used to validate assays. Blood or sera from horses infected with T. equi (only) or B. caballi (only) will be used to show the specificity of the new tests for T. haneyi. The final format of the assays will depend on the in vitro behavior of the developed reagents (recombinant antigens and monoclonal antibodies). Monoclonal antibodies may be derived in mice against T. haneyi antigen(s) that meet the definition of being specific to T. haneyi infection. One thousand serum and blood samples from horses presented at the southern U. S. border have been provided to the cooperator, and will be used to determine the prevalence of T. haneyi infected horses being presented for entrance into the U.S. 2) Test the efficacy of currently approved and experimental drugs against T. haneyi. The in vitro/in vivo efficacy of pharmaceutical compounds against T. haneyi will be determined in an effort to find a treatment strategy for T. haneyi. The collaborator has assisted with obtaining preliminary data on the efficacy of several compounds against T. haneyi. 3) Identify potential diagnostic and subunit vaccine targets for T. orientalis Ikeda (2016 VA-U.S. isolate). Using the technology and experience developed through collaboration with cooperator, immunodominant antigens will be identified from T. orientalis Ikeda and a serologic diagnostic test developed. Similar to previous collaborative work concerning T. parva and T. equi, appropriate vaccine targets present on the sporozoite, merozoite, and schizont stages of T. orientalis will be identified and tested in vivo. The final objective is 4) Provide more complete characterization of the virulence of Theileria spp within cattle and horses. In horses, this objective will be accomplished by comparing the outcome of infection between T. equi, T. haneyi and novel T. spp in the splenectomized horse. Preliminary data shows splenectomized horses can survive T. haneyi infection. Critically, the use of equine monocyte subset changes during Theileria infection in the horse will be used to inform virluence of these species. This approach has been shown to have utility during lethal T. parva infection in cattle. In cattle, we will follow acute infection with T. orientalis, using different infectious parasite doses and/or tick infection vs. needle challenge (once the tick vector is identified). We will utilize qPCR, blood cell parameter changes, monocyte subset changes, and clinical signs to assess virulence/pathogenesis of U.S. isolates.