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United States Department of Agriculture

Agricultural Research Service

2009 Annual Report

1a.Objectives (from AD-416)
The objectives of this research are: (1) the testing of the hypothesis that tick antigens capable of inducing anti-tick immunity can be delivered through a transfected parasite; (2) discovery of new tick antigen vaccine targets; (3) an understanding of the vector competence of certain U. S. ticks for transmission of equine babesiosis, and (4) the determination if certain anti-babesial drugs are capable of clearing horses of persistent babesial infection.

1b.Approach (from AD-416)
The above objectives will be approached through the use of transfection to create replication competent parasites containing tick antigens known to induce anti-tick immunity. In parallel with this approach new tick antigens will be discovered and characterized through genetic approaches including suppressive subtractive hybridization and Serial Analysis of Gene Expression. New antigens will first be tested by subunit immunization for their ability to induce anti-tick immunity. Tick vectors present in the U. S. and known to feed on horses will be tested for their ability to transmit B. equi and/or B. caballi and finally selected chemotherapeutics will be tested for their ability to clear persistent B. equi and/or B. caballi infections. Clearance will be defined as the lack of detectable anti-parasite antibody, the lack of PCR detectable genetic elements of B. equi and/or B. caballi and finally by testing for the ability of know competent ticks to acquire infection from treated horses. Formerly 5348-32000-020-00D (12/06).

3.Progress Report
This project addresses critical gaps in our understanding of the transmission and disease expression of babesial parasites of cattle and horses. A primary current concern is the emergence of treatment resistant exotic ticks in the United States capable of transmitting babesial parasites to cattle and horses. Infection of cattle and horses with these tick-borne parasites cause great economic burdens worldwide. During the past year our laboratory has made significant progress toward the development of a long-term acting anti-babesial and anti-tick vaccine for cattle (accomplishment 01); completed risk assessment of the tick Dermacentor nitens as a reservoir for B. caballi transmission for the Animal Plant Health Inspection Service (accomplishment 02); completed work demonstrating the ability to clear horses of B. caballi infection through chemotherapy (imidocarb); initiated work testing the ability of chemotherapy (ponazuril) to clear horses of B. equi infection; completed experiments testing the ability of certain ticks which are native to the United States for their ability to transmit B. equi (requested by the Animal Plant Health Inspection Service), and initiated work using RNA interference (RNAi) for targeting tick genes that are potential vaccine candidates. RNAi is a molecular biology tool which can directly interfere with the expression of targeted genes in the life tick thereby aiding in the identification of the function of targeted genes. Ongoing collaborations with Washington State University are defining the method to establish long-term anti-babesial and anti-tick immunity through transfection technology; collaborations with the International Livestock Research Institute in Nairobi, Kenya is identifying genes for potential use as anti-tick vaccine targets and the collaboration with The Institute for Genomics Research (TIGR), now the J. Craig Ventor Institute is completed. Our collaborations with TIGR and subsequently JCVI led to sequencing and annotation of the Babesia bovis (a parasite of cattle) genome and Babesia equi (a parasite of horses) genome. Our laboratory collaborated with colleagues at the University of Florida to obtain an isolate of Babesia equi involved in an outbreak of this parasite in Florida and have worked with the Animal Plant Health Inspection Service to develop a final control plan for equine babesiosis during the upcoming World Equestrian Games.

1. Critical progress obtained toward development of a long acting anti-babesial and anti-tick vaccine. Babesiosis is an ecomically devastating disease of cattle. The emergence of resistance to control measures in ticks which transmit babesiosis, requires development of novel control methods. ARS scientists in Pullman, WA developed a procedure for placing new genetic material into babesial parasites for use as a long-term anti-babesial and anti-tick vaccine was developed. Attenuated babesial parasites containing genes important for an anti-tick vaccine have the potential to provide long-term immunity against babesial parasites and the ticks capable of transmission.

2. Transmission of the horse parasite (Babesia caballi) is limited to one tick generation. The infection of horses with B. caballi within the United States is a disease control issue for regulators. Transmission of B. caballi through tick generations of Dermacentor nitens was shown by ARS scientists at Pullman, WA to be limited to one generation. This result limits concerns of this tick being a major reservoir for this parasite. The Animal Plant Health Inspection Service of USDA and other regulators within states hosting equine events utilize these data for risk assessment and management preventing disease transmission at events hosting international gatherings of horses.

6.Technology Transfer

Number of New Commercial Licenses Executed1

Review Publications
Silva, M., Helali, S., Esseghaierb, C., Suarez, C.E., Oliva, A., Abdelghani, A. 2008. An impedance spectroscopy method for the detection and evaluation of Babesia bovis antibodies in cattle. Sensors and Actuators B: Chemical. 135:206-213.

Suarez, C.E., Mcelwain, T. 2009. Stable expression of a GFP-BSD fusion protein in Babesia bovis merozoites. International Journal for Parasitology. 39(3):289-297.

Goff, W.L., Johnson, W.C., Molloy, J.B., Jorgensen, W.K., Waldron, S.J., Figueroa, J.V., Matthee, O., Adams, D.S., Mcguire, T.C., Pino, I., Mosqueda, J., Palmer, G.H., Suarez, C.E., Knowles Jr, D.P., Mcelwain, T.F. 2008. Validation of a Competitive Enzyme-Linked Immunosorbent Assay for Detection of Babesia bigemina Antibodies in Cattle. Clinical and Vaccine Immunology. 15(9):1316-1321.

Odongo, D., Ueti, M.W., Mwaura, S., Knowles Jr, D.P., Bishop, R., Scoles, G.A. 2009. Quantification of Theileria parva in Rhipicephalus appendiculatus (Acari: Ixodidae) Confirms Differences in Infection Between Selected Tick Strains. Journal of Medical Entomology. 46(4):888-894.

Schwint, N.O., Knowles Jr, D.P., Ueti, M.W., Kappmeyer, L.S., Scoles, G.A. 2008. Transmission of Babesia caballi by Dermacentor nitens (Acari: Ixodidae) Is Restricted to One Generation in the Absense of Alimentary Reinfection on a Susceptible Equine Host. Journal of Medical Entomology. 45(6):1152-1155.

Bastos, R.G., Johnson, W.C., Mwangi, W., Brown, W.C., Goff, W.L. 2008. Bovine NK cells acquire cytotoxic activity and produce IFN-gamma after stimulation by Mycobacterium bovis BCG- or Babesia bovis-exposed splenic dendritic cells. Veterinary Immunology and Immunopathology. 124:302-312.

Wilcowsky, S., Farber, M., Gil, G., Echaide, I., Mosqueda, J., Alcaraz, E., Suarez, C.E., Florin-Christensen, M. 2008. Molecular Characterization of Babesia bovis strains using PCR restriction length polymorphism analysis of the msa2s/b genes. Annals of the New York Academy of Sciences. 1149:141-144.

Last Modified: 8/28/2016
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