Evaluation of two inactivated vaccines against Campylobacter fetus in an experimental bovine model: immunological survey and genital clearance in heifers

Abstract

Bovine Genital Campylobacteriosis is a venereal disease caused by Campylobacter fetus subsp. venerealis (Cfv), responsible for reproductive losses in breeding systems that rely on natural service. Here, we evaluated 2 vaccines against Cfv infection in heifers experimentally challenged by intravaginal route, assessing bacterial persistence and immunological systemic and local response. Forty-four heifers were assigned to 4 groups: G1 (vaccine A), G2 (vaccine B), G3 (infected group with placebo) and G4 (negative control). Experimental intravaginal challenge with Cfv was carried out in G1, G2 and G3, and followed up for 105 days after. A significant difference in positivity through bacteriological culture in vaginal cervical mucus was observed between the vaccinated groups (61,81% in G1 and 45,45% in G2) and the infected group (87,27% in G3) (p < 0.05). Local specific antibodies (IgA) and systemic (IgG) were detected by ELISA in all groups experimentally challenged, though, the vaccinated groups (G1 and G2) showed an earlier increase. Additionally, agglutinating antibodies were observed after vaccination, mainly for group G2 (p = 0.0316). Through qPCR a lower load of bacteria resulted in vaccinated cattle during the sampling period. We conclude that vaccinated heifers showed a significantly earlier clearance of Cfv from the reproductive tract compared to unvaccinated heifers, associated to high-early levels of systemic and local Ig. These vaccines are a potential preventive measure that requires natural field cases to evaluate reproductive performance.