Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: IMMUNOLOGIC AND PHARMACOLOGICAL INTERVENTIONS OF VECTOR-BORNE BABESIOSIS

Location: Animal Diseases Research

2007 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. BSL-1; 6/30/06. Formerly 5348-32000-020-00D (12/06).


4.Accomplishments
1) Acquired Dermacentor nitens ticks and a D. nitens transmissible strain of B. caballi from Puerto Rico and infected horses for planned treatment trials.

It was important for us to acquire a tick transmissible strain of B. caballi and a colony of a tick species that is known to transmit the strain under natural conditions. Scientist from the Animal Research Unit in Pullman, WA accomplished this by collecting ticks from B. caballi infected ticks in Puerto Rico and the feeding those ticks on a horse in our lab. The horse acquired infection and served as a source of infectious material to infect horses for our planned treatment trial. The ticks have been reared through 3 successive generations on non-susceptible hosts to clear them of infection. This B. caballi isolate and colony of D. nitens ticks which naturally transmit it will be essential for our future work on treatment and control of B. caballi. This accomplishment addresses NP #103, Animal Health, program component #7B, Countermeasure to control and prevent parasitic diseases: Hemoparasitic Diseases.

2) Determination of the Babesia bovis transmission efficiency by a primary vector, Rhipicephalus microplus.

Due to a number of emerging factors including the acaracide resistance of vector ticks such as Rhipicephalus microplus the reemergence of bovine babesiosis is a major concern to U. S. cattle producers. An understanding of the transmission efficiency of this vector for bovine babesiosis is critical for management in the event of additional outbreaks. Scientist from the Animal Research Unit in Pullman, WA discovered that although B. bovis infection of ticks was below PCR detection, the ticks were still able to efficiently transmit infection to naïve cattle. This finding is critical to understanding the role of acute parasitemia in epidemiology of bovine babesiosis and management recommendations. This accomplishment addresses NP #103, Animal Health, program component #7B, Countermeasure to control and prevent parasitic diseases: Hemoparasitic Diseases.

3) Sequencing and Annotation of the Babesia bovis genome

Due to a number of emerging factors including the acaracide resistance of vector ticks such as Rhipicephalus microplus the reemergence of bovine babesiosis is a major concern to U. S. cattle producers. New methods to control vector ticks and/or disease are needed. Scientist from the Animal Research Unit in Pullman, WA in collaboration with The Institute for Genomics Research and WSU, sequenced the B. bovis genome and annotated in order to search for virulence genes, new vaccine candidates and genomic locations for gene replacement studies (transfection based vaccines). These data are paramount in the development of anti-babesial vaccines including those which block transmission. This accomplishment addresses NP #103, Animal Health, program component #7B, Countermeasure to control and prevent parasitic diseases: Hemoparasitic Diseases.

4) Characterization of a key component of bovine innate immunity to Babesia bovis

Due to a number of emerging factors including the acaracide resistance of vector ticks such as Rhipicephalus microplus the reemergence of bovine babesiosis is a major concern to U. S. cattle producers. New methods to control vector ticks and/or disease are needed including vaccines designed based on immunologic data acquired from animals that mount a successful immune response to an initial exposure to a virulent Babesia isolate. In continuing efforts to define the complex spleen-dependent innate immunity of young calves to B. bovis, two previously unknown spleen cell phenotypes involved as key populations in the innate immune response were identified and characterized by the scientists in Pullman, WA and initiated further studies to document their interactions. Research will aid in understanding of certain U.S. ticks for transmission of equine babesiosis and expected to identify measures to control and prevent parasitic diseases. This accomplishment addresses NP #103, Animal Health, program component #7B, Countermeasure to control and prevent parasitic diseases: Hemoparasitic Diseases.


5.Significant Activities that Support Special Target Populations
None


6.Technology Transfer

Number of non-peer reviewed presentations and proceedings5

Review Publications
Howell, J.M., Ueti, M.W., Palmer, G.H., Scoles, G.A., Knowles Jr, D.P. 2007. Transovarial Transmission Efficiency of Babesia bovis Tick Stages Acquired by Rhipicephalus (Boophilus) microplus during Acute Infection. Journal of Clinical Microbiology. 45(2):426-431.

Uilenberg, G., Goff, W.L. 2006. Polyphasic Taxonomy. Annals of the New York Academy of Sciences. 1081:492-497.

Bastos, R.G., Johnson, W.C., Brown, W.L., Goff, W.L. 2007. Differential response of splenic monocytes and DC from cattle to microbial stimulation with Mycobacterium bovis BCG and Babesia bovis merozoites. Veterinary Immunology and Immunopathology. 115(3-4):334-345.

Goff, W.L., Molloy, J.B., Johnson, W.C., Suarez, C.E., Pino, I., Rhalem, A., Sahibi, H., Ceci, L., Carelli, G., Adams, D.S., Mcguire, T.C., Knowles Jr, D.P., Mcelwain, T.F. 2006. Validation of a Competitive Enzyme-Linked Immunosorbent Assay for Detection of Antibodies against Babesia bovis. Clinical and Vaccine Immunology. 13(11):1212-1216.

Murphy, B.G., Hotzel, I., Jasmer, D.P., Davis, W.C., Knowles Jr, D.P. 2006. TNFalpha and GM-CSF-induced activation of the CAEV promoter is independent of AP-1. Virology. 352(1):188-199.

Last Modified: 9/23/2014
Footer Content Back to Top of Page