Standardization of the model of experimental infection in cattle with Anaplasma centrale for the production of immunogens

Abstract

Bovine anaplasmosis is an infectious transmissible disease caused by the rickettsia Anaplasmamarginale. Prophylaxis can be achieved by vaccination with A. centrale-infected erythrocytes (IE) obtained from splenectomized calves. Standardization of conditions for A. centrale infection of bovines can lead to a more efficient production system, which is particularly important when the vaccine is produced as a trivalent formulation that also contains erythrocytes infected with attenuated forms of Babesiabovis and B. bigemina parasites. In this study, bovines (n=26) were inoculated with different doses of A. centrale- infected erythrocytes (2, 3, 4 or 5 x 108 IE per animal). The course of infection was analyzed with regards to pre-patent period, rickettsemia, and maximal hematocrit decrease, and possible correlations between these parameters were evaluated. The lowest inoculum resulted in significantly lengthier pre-patent periods with respect to the other three groups. Also, a moderate negative correlation was observed between the length of the pre-patent period and rickettsemia. Blood from each of these calves was used to produce  commercial vaccines. A humoral response against Anaplasma spat sixty days post vaccination was confirmed by competitive ELISA in a representative group of bovines inoculated with each batch of vaccine produced. Therefore, we conclude that the obtained immunogen maintained itsimmunoprophylactic characteristics in all the series produced. Also, this description of the experimental model could be useful for future investigations.