Detectable immunological response in Brucella abortus s 19 vaccinated herds of cattle in vilachchiya veterinary range, north central province, Sri Lanka

Abstract

Brucellosis a zoonotic disease caused by Gram-negative, intracellular, coccobacillus. Brucellosis, an economically important disease in livestock with zoonotic implications has been reported worldwide. It is transmitted via contaminated animals and their products. Clinical signs of animal brucellosis are abortions, reduced fertility, retention of fetal membranes, endometritis, and substantial decline in milk production over an animal’s lifespan. Orchitis, epididymitis and chronic hygroma had been reported in bulls. The current study focused on to studying the detectable immunological responses to Brucella S 19 live attenuated vaccine using serological tests in cattle of dry zone farms. A questionnaire-based survey was carried out in selected farms with and without a previous history of abortion respectively. Animals that were in 1st to 5th lactation in the 18 farms were selected for screening by Rose Bengal Plate Test (RBPT) and positives were confirmed by Complement Fixation Test (CFT). Three farms each with and without history of abortion were selected for Brucella S19 vaccination from the RBPT and CFT negative farms. Sixty non pregnant heifers over 6 months were selected, and 1ml each of S19 vaccine was given subcutaneously to 30 animals while 30 animals were kept as controls. The serum samples were collected and screened for Brucellosis by RBPT and CFT at 2, 4, 6, 8 and 10 weeks of post vaccination. The second week after the vaccination, 71.42% of the animals showed over 1:4 CFT levels while 28.57% of them did not show any antibody titres for Brucellosis in the Brucella endemic farms. In Brucella non-endemic farms, 68.75% of animals showed over 1:4 CFT titre at 2 weeks after the vaccination. However, 31.25% of animals did not show any CFT titre. No persistent and detectable antibody responses were found 10 weeks post vaccination in heifers of endemic and non-endemic herds. The titers of CFT indicate IgG or IgM humeral response, cell mediated immune response of live attenuated vaccine has not been monitored in the study. Thus, seropositivity after the 10 weeks post vaccination may indicate an infection of Brucellosis since no antibodies from vaccination were found. Further investigation with highly sensitive tests such as ELISA is recommended to have a better insight into this aspect in the future.