Abstract
Epizootic bovine abortion (EBA) is an arthropod-borne bacterial disease that causes significant economic loss for cattle producers in the western United States. The etiologic agent, Pajaroellobacter abortibovis, is an intracellular pathogen that has yet to be cultivated in vitro, thereby requiring novel methodologies for vaccine development. A vaccine candidate, using live P. abortibovis-infected cells (P.a-LIC) harvested from mouse spleens, was tested in beef cattle. Over the course of two safety studies and four efficacy trials, safety risks were evaluated, and dosage and potencies refined. No incidence of anaphylaxis, recognized health issues or significant impact upon conception rates were noted. Vaccination did result in subclinical skin reactions. Early fetal losses were noted in two trials and were significant when the vaccine was administered within 21 days prior to conception. Administration of the EBA agent (EBAA) vaccine as a single dose, at a potency of 500 P.a–LIC, 56 days prior to breeding, provided 100% protection with no early fetal losses. Seroconversion occurred in all animals following EBAA vaccination and corresponded well with protection of the fetus from epizootic bovine abortion.
Highlights
Epizootic bovine abortion (EBA; foothill abortion) is a vector-borne disease and is geographically limited by the distribution of the Argasid tick, Ornithodoros coriaceus Koch [1,2,3,4]; there are no other recognized methods of transmission
Devastating reproductive losses associated with the disease are primarily reported within the beef cattle industry as these animals are most often pastured in habitat that supports the tick vector, but losses can occur in dairy cattle breeds [10,11]
At the time of the study, the tick vector had not been found on these premises despite several trapping attempts, nor had EBA been diagnosed in animals within the herd
Summary
Epizootic bovine abortion (EBA; foothill abortion) is a vector-borne disease and is geographically limited by the distribution of the Argasid tick, Ornithodoros coriaceus Koch [1,2,3,4]; there are no other recognized methods of transmission. The full range of the vector, and thereby the disease, is not completely defined but epizootic bovine abortion is recognized in the dry foothill, mountainous and high desert regions of California, Oregon and Nevada [7,8], and while not reported in the literature, cattle in Mexico likely suffer EBA losses. Preventive measures have been limited to the management of vector exposure, either by pasturing cattle in known O. coriaceus habitat prior to breeding or by avoidance of tick infested habitats during pregnancy; neither are always efficacious or practical. Populations of naïve pregnant cattle, introduced into areas with O. coriaceus populations, can experience devastating fetal losses [15]
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