Preliminary evaluation of the in vivo antigenic power of a new formulation for the bovine babesiosis immunoprophylaxis

Abstract

Bovine babesiosis is a hemoparasitic disease caused by protozoa of the genus Babesia, the most important are Babesia bovis and B. bigemina, both transmitted by the common bovine tick, Rhipicephalus microplus. In combination with anaplasmosis, they form the Bovine Tristeza Complex, one of the main limiting factors for productive development in tropical and subtropical areas of the world. Currently, for the prophylaxis of bovine babesiosis in Argentina, only live vaccines are available in fresh and deep-frozen presentations. In the present work, we evaluated the immunogenicity of erythrocytes parasitized with Babesia sp, dehydrated and incorporated into a new adjuvant, formulated for use in humans, as a new immuno prophylactic alternative. With this aim, parasitized erythrocytes obtained from in vitro cultures were dehydrated by spray-drying
techniques and assembled with an adjuvant. Twelve calves negative for blood parasites were
used, which were divided into 4 groups of 3 animals each one. Control group: without inoculation;
Treated Group 1: inoculated with adjuvant; Treated Group 2: adjuvant + erythrocytes parasitized with B. bovis and Treated Group 3: adjuvant + erythrocytes parasitized with B. bigemina. Two subcutaneous inoculations were performed, on 0 and 15 days. During 60 days, rectal temperature, hematocrit and parasitaemia control were performed, in turn, samples for serology were taken on 30- and 60-days post inoculation. The animals remained negative throughout the trial, except on day 60, where 33% of Treated Group 3 presented specific antibody titers against the inoculated agent, B. bigemina. Although the response rate is low, the fact that there is no effective killed vaccine for the prophylaxis of this disease encourages us to continue adjusting the inoculant dose.