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ARS Home » Pacific West Area » Pullman, Washington » Animal Disease Research » Research » Research Project #422175

Research Project: Pharmacological and Immunologic Interventions Against Vector-Borne Bovine and Equine Babesiosis

Location: Animal Disease Research

Project Number: 2090-32000-034-00-D
Project Type: In-House Appropriated

Start Date: Oct 6, 2011
End Date: Sep 30, 2016

Objective 1: Improve control of bovine babesiosis and its tick vector through the identification of novel targets and development of new vaccine strategies. Sub-objective 1A: Identify surface exposed antigens expressed by Babesia bovis during its development within the tick. Sub-objective 1B: Test if antibody response in cattle immunized with tick midgut surface antigens enhances access of bovine antibodies to tick hemolymph. Sub-objective 1C: Determine if immunization with Babesia tick stage and midgut antigens blocks B. bovis transmission. Objective 2: Evaluate the risks of B. equi or B. caballi transmission by species of ticks indigenous to the United States. Sub-objective 2A: Identify tick species feeding on horses at the outbreak ranch in Texas that are capable of transmitting B. equi. Sub-objective 2B: Determine the B. equi transmission efficiency of vector-competent tick species from the outbreak ranch in Texas. Objective 3: Determine the impact of both new and current chemotherapeutic agents on the clearance of B. equi or B. caballi from persistently infected horses and on the risks of transmission. Sub-objective 3A: Assess the efficacy of imidocarb dipropionate to eliminate B. equi infection Sub-objective 3B: Develop a serological method that rapidly and accurately predicts elimination of B. equi infection following treatment. Sub-objective 3C: Assess tick-borne transmission risk of imidocarb dipropionate treated horses.

The discovery of chemical (acaricide) resistant ticks capable of transmitting protozoan parasites that cause bovine babesiosis and the reemergence of equine babesiosis within the United States are the catalysts for this research plan. National concerns are eradication of the currently emerging equine babesiosis, the possibility of reemergence of bovine babesiosis and the need for novel methods to control the causal parasites and their tick vectors. The current strategy in the U.S. for bovine babesiosis is control of ticks through acaricides. However, the development of ticks resistant to acaricides is resulting in geographic expansion of these vectors in the U.S. Since cattle entry is not monitored by serology, infected cattle are entering the U.S. The risk of bovine babesiosis is significantly increased by the presence and expanding range of ticks capable of transmission and the lack of serologic monitoring of cattle. To protect the U.S. cattle population from babesiosis, this research plan proposes to develop novel immunological interventions and to use these tools to test the hypothesis that tick transmission of Babesia bovis can be blocked. The primary goal is to disrupt the B. bovis-tick interface at the level of the tick midgut and hemolymph. In contrast to bovine babesiosis, the control strategy for equine babesiosis is based on serological restriction of infected horses from entering the country. Due to previous use of the complement fixation test (CFT), which lacked sensitivity, infected horses have been admitted into the U.S. which likely led, at least in part, to the recent reemergence of this foreign equine disease in the U.S. The goal of this research plan related to equine babesiosis is to assist the Animal Plant Health Inspection Service (APHIS), State Veterinarians and owners in eliminating Babesia infections, transmission risk, and potential endemicity by developing pharmacological interventions.