Research Project: Development of Detection and Control Strategies for Bovine Babesiosis and Equine Piroplasmosis

Location: Animal Disease Research

2019 Annual Report

Objectives
The goals of this project are to develop multivalent bovine babesiosis subunit vaccines targeting antigens expressed in different Babesia bovis life cycle stages, to develop serological diagnostic assays to aid in bovine babesiosis and equine piroplasmosis diagnosis and surveillance, and to characterize vector competence and drug susceptibility for a new protozoan parasite of horses. These goals will be addressed in the following objectives: Objective 1: Develop diagnostic assays and vaccines for bovine babesiosis by targeting antigens from multiple parasite stages. Subobjective 1A: Determine if immunization with B. bovis blood stage subdominant antigens reduces disease severity and impacts tick infection. Subobjective 1B: Identify B. bovis tick stage specific targets for development of a vaccine to reduce or block tick infection. Subobjective 1C: Develop a multivalent vaccine targeting tick and B. bovis parasite proteins to decrease clinical disease and B. bovis transmission. Subobjective 1D: Develop a B. bovis serological assay to determine infection prevalence. Objective 2: Develop improved diagnostic assays and control strategies for emerging equine piroplasmosis organisms. Subobjective 2A: Identify diagnostic targets for detection of horses infected with Theileria-like parasite. Subobjective 2B: Determine competent tick vectors of the new Theileria-like parasite. Subobjective 2C: Determine Theileria-like parasite drug susceptibility.

Approach
Objective 1: Develop diagnostic assays and vaccines for bovine babesiosis by targeting antigens from multiple parasite stages. Goals: The goal of this objective is to develop preventive measures and diagnostic assays for bovine babesiosis in an effort to stop pathogen spread via tick vectors and to understand pathogen prevalence and distribution. Approach: Target B. bovis proteins expressed in vertebrate or invertebrate hosts which may provide control strategies to reduce disease severity in the mammalian host and block transmission of parasites via tick vectors. In addition, this project will provide diagnostic tools to determine vaccine efficacy and to assess pathogen prevalence and distribution in the U.S. Objective 2: Develop improved diagnostic assays and control strategies for emerging equine piroplasmosis organisms. Goals: Develop diagnostic assays for the newly discovered Theileria-like parasite (TLP) to discriminate between horses infected with this new parasite and those infected with T. equi, elucidate vector competency and determine the efficacy of drug therapy to prevent TLP spread in the U.S. horse population.

Progress Report
Significant progress continued under Objective 1, which involved expressing recombinant parasite proteins and developing a diagnostic test to detect infected cattle. In support of Sub-objectives 1A and 1B, progress was made towards the expression and purification of proteins to develop vaccines to control cattle infection and the tick vector which will prevent the spread of parasites. In support of Sub-objective 1A, significant progress was made towards developing a more accurate test at targeting a conserved gene in the new horse parasite. Progress was made in generating and purification of proteins for the development of a serological test. For Sub-objective 1D, progress was made towards validating a new diagnostic test to detect bovines infected with the parasite. This technology will allow infected animals to be monitored which will prevent the spread of pathogens in the U.S. Under Objective 2, significant progress was made in the development of diagnostic tests, determining vector competence and determining treatment efficacy for the new parasite that infects horses. In support of Sub-objective 2B, significant progress was achieved in assessing several tick species capable of transmitting the new horse parasite. Several tick species were fed onto infected horses and this demonstrated the capability of some tick species to acquire the new parasite from infected horses. In support of Sub-objective 2C, significant progress was made in assessing the efficacy of drug therapy to clear the new parasite from infected horses. Progress was made towards treating horses infected with the new parasite and demonstrating the low clearance efficacy of the new parasite from infected horses.

Accomplishments
1. Proteins to control parasite transmission and tick infestation identified. Babesia bovis transmitted by ticks causes severe disease in cattle and more than 90 percent of infected adult animals die as a consequence of red blood cell damage. This parasite is spread in tropical and subtropical regions including Mexico. There is no vaccine available in the U.S. Should an outbreak occur, the U.S. cattle industry's ability to produce food and fiber would be significantly reduced. ARS scientists at Pullman, Washington, identified new parasite and tick proteins as antigen candidates to develop vaccines for preventing disease and tick infestation. These vaccines will mitigate economic losses for the U.S. cattle industry if bovine babesiosis outbreaks occur.

2. New diagnostic test to detect cattle infected with parasite. Babesia bovis causes a devastating disease in cattle and is responsible for significant losses for the livestock industry. The discovery of acaricide-resistant tick populations that transmit protozoan parasites on the U.S.-Mexico border increases the risk for outbreaks in the U.S. ARS scientists at Pullman, Washington, developed and validated a new serological diagnostic test. The new serological test will increase the ability to prevent and control B. bovis spreading to the U.S. cattle population.

3. Tick capable of transmitting a new parasite between horses. The discovery of a new Theileria-like parasite of horses on the U.S.-Mexico border causes a tremendous concern for the horse industry. It was unknown if ticks could spread this parasite to naïve horses in the U.S. ARS scientists at Pullman, Washington, assessed several tick species including Rhipicephalus, Dermacentor and Amblyomma ticks, to determine vector competence. The results demonstrated that ticks present in Mexico, but foreign to the U.S. can acquire the new horse parasite. Controlling tick feeding on horses is critical to control the spread of the new horse parasite.

Review Publications
Alzan, H.F., Cooke, B.M., Suarez, C.E. 2019. Transgenic babesia bovis lacking 6-Cys sexual-stage genes as the foundation for non-transmissible live vaccines against bovine babesiosis. Ticks and Tick Borne Diseases. 10(3):722-728. https://doi.org/10.1016/j.ttbdis.2019.01.006.
Elnaggar, M.M., Abdellrazeq, G.S., Venn-Watson, S.K., Jensen, E.D., Mack, V., Fry, L.M., Sacco, R.E., Davis, W.C. 2017. Identification of monoclonal antibodies cross-reactive with bottlenose dolphin orthologues of the major histocompatibility complex and leukocyte differentiation molecules. Developmental and Comparative Immunology. 192:54-59. https://doi.org/10.1016/j.vetimm.2017.09.007.
Fry, L.M., Bastos, R.G., Stone, B.C., Williams, L.B., Knowles, D.P., Murphy, S.C. 2019. Gene gun DNA immunization of cattle induces humoral and CD4 T-cell-mediated immune responses against the Theileria parva polymorphic immunodominant molecule. Vaccine. 37(12):1546-1553. https://doi.org/10.1016/j.vaccine.2019.02.009.
Abdellrazeq, G.S., Elnaggar, M.M., Bannantine, J.P., Schneider, D.A., Souza, C.D., Hwang, J., Mahmoud, A.H., Hulubei, V., Fry, L.M., Park, K., Davis, W.C. 2019. A peptide-based vaccine for Mycobacterium avium subspecies paratuberculosis. Vaccine. 37(21):2783-2790. https://doi.org/10.1016/j.vaccine.2019.04.040.
Williams, L.B., Fry, L.M., Herndon, D.R., Franceschi, V., Schneider, D.A., Donofrio, G., Knowles, D.P. 2019. A recombinant bovine herpesvirus-4 vectored vaccine delivered via intranasal nebulization elicits viral neutralizing antibody titers in cattle. PLoS One. 14(4):e0215605. https://doi.org/10.1371/journal.pone.0215605.
Knowles, D.P., Kappmeyer, L.S., Haney, D., Herndon, D.R., Fry, L.M., Munro, J.B., Sears, K., Ueti, M.W., Wise, L.N., Silva, M., Schneider, D.A., Grause, J., White, S.N., Trentina, K., Bishop, R., Odongo, D.O., Pelzel-McCluske, A.M., Scoles, G.A., Mealey, R.H., Silva, J.C. 2018. 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. International Journal for Parasitology. 48(9-10):127-137. https://doi.org/10.1016/j.ijpara.2018.03.010.
Abdellrazeq, G.S., Elnaggar, M.M., Bannantine, J.P., Park, K.T., Souza, C.D., Backer, B., Hulubei, V., Fry, L.M., Khaliel, S.A., Torky, H.A., Schneider, D.A., Davis, W.C. 2018. A Mycobacterium avium subsp. paratuberculosis relA deletion mutant and a 35 kDa major membrane protein elicit development of cytotoxic T lymphocytes with ability to kill intracellular bacteria. Veterinary Research. 49:53. https://doi.org/10.1186/s13567-018-0549-3.
Gallego-Lopez, G., Lau, A., O'Connor, R., Ueti, M.W., Cooke, B., Laughery, J., Graca, T., Madsen-Bouterse, S., Oldiges, D., Suarez, C.E. 2018. Up-regulated expression of spherical body protein 2 truncated copy 11 is associated with reduced in vitro endothelial cell cytoadhesion by babesia bovis. International Journal for Parasitology. 49(2):127-137. https://doi.org/10.1016/j.ijpara.2018.05.015.
Suarez, C.E., Alzan, A., Silva, M., Rathinasamy, V., Poole, W., Cooke, B. 2019. Unraveling the cellular and molecular pathogenesis of bovine babesiosis: is the sky the limit? International Journal for Parasitology. 49(2):183-197. https://doi.org/10.1016/j.ijpara.2018.11.002.
Bohaliga, G.A., Johnson, W.C., Taus, N.S., Hussein, H.E., Ueti, M.W. 2018. Identification of a putative methyltransferase gene of Babesia bigemina as a novel molecular biomarker uniquely expressed in parasite tick stages. Parasites & Vectors. 11(1):480. https://doi.org/10.1186/s13071-018-3052-9.
Hala, H.E., Johnson, W.C., Taus, N.S., Suarez, C.E., Scoles, G.A., Ueti, M.W. 2019. Silencing expression of the Rhipicephalus microplus vitellogenin receptor gene blocks Babesia bovis transmission and interferes with oocyte maturation. Parasites & Vectors. 12(1):7. https://doi.org/10.1186/s13071-018-3270-1.
Iacobucci, E., Fritz, H., Papageorgiou, S., O'Conner, R., Taus, N.S., Ueti, M.W. 2019. Detection and genotypic characterization of toxoplasma gondii DNA within the milk of Mongolian livestock. Parasitology Research. 118(6):2005-2008. https://doi.org/10.1007/s00436-019-06306-w.
Ruiz, M.H., Suarez, C.E., Mercado-Uriostequi, M.A., Hernandez-Ortiz, R., Ramos, J.A., Galindo-Velazco, E., Mosqueda, J. 2018. Babesia bovis RON2 contains conserved B-cell epitopes that induce an invasion-blocking humoral immune response in immunized cattle. Parasites & Vectors. 11:575. https://doi.org/10.1186/s13071-018-3164-2.