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Background: Information on the prevalence of infectious agents in dairy farms forms the basis for formulating a suitable control strategy; especially in endemic situations. Aims: A cross-sectional study was undertaken to determine the prevalence of six economically important bovine diseases, causing reproductive disorders including bovine abortion in organized dairy herds in India. Methods: A total of 1,075 animals (cattle and buffaloes) from 09 dairy farms were screened by ELISA tests. Results: Bovine viral diarrhoea (BVD) was the most prevalent (56.5%) disease followed by infectious bovine rhinotracheitis (IBR) (45.4%). Prevalence of Q-fever (5.4%) and neosporosis (6.1%) were less on the farms. Although 16.3% of the samples turned positive for brucellosis, the contribution of calf-hood vaccination (B. abortus S19 vaccine) to the prevalence of antibodies cannot be ruled out. The overall prevalence of bovine anaplasmosis, known to cause sporadic abortions in dairy herds, was 34.1% in the 9 farms with a prevalence of less than 20% in 5 farms. Infection of multiple abortifacient (seroprevalence to more than two pathogens) was recorded in 56.8% of animals. A very strong association was observed between BVD and brucellosis (Odds ratio 14.2; P<0.001). Further, a positive association was also seen between seroprevalence of IBR and anaplasmosis, and neosporosis and Q fever (P<0.05). Conclusion: Viral diseases were found to be more common in the dairy herds than bacterial and protozoan diseases. Increased susceptibility of IBR seropositive cows to other bacterial and viral infections was observed. [ABSTRACT FROM AUTHOR]

Bovine brucellosis is a zoonotic disease. It impacts dairy industry since it is a major cause of abortion. The disease is caused by bacteria belonging to the genus Brucella. The pathogen is excreted in milk, semen and aborted materials. Bovine brucellosis is currently controlled by calfhood vaccination of females using live attenuated B. abortus strains (S19/RB51), however it does not provide 100% protection, and its use is restricted by age and gender. The vaccine strains are infectious to humans. Review of literature indicated that use of glyco-conjugate (GC) vaccines could address the above problems. Therefore, the objective of study was to assess the protective efficacy and therapeutic potential of GC vaccine prepared from Brucella abortus S19 (S19GC) in cattle. Immunization of Brucella free animals with two doses of 50μg each at an interval of 90 days by sub-cutaneous route resulted in pronounced Th1 mediated interferon gamma (IFN-γ) response (P=0.0061) as observed in ELISPOT assay compared to unvaccinated controls till 90 days post vaccination (DPV). The ability of S19GC to arrest shedding of Brucella was studied in brucellosis positive animals, vaccination of infected animals each with 50μg of S19GC by subcutaneous route resulted in arresting of shedding as evidenced by negative culture results, reduction (2 log folds) in genome copy number as observed by realtime PCR (qPCR). The prime-boost strategy of immunization (50 μg dose/ cattle) of a group of cattle infected with brucellosis (> 53%) was only able to arrest bacterial shedding transiently (7- 60 DPV) in 66.67% immunized cattle, and after booster bacterial shedding was not recorded by culture in 83.34% of the animal till 250 PI. Also, Brucella genome was not detected transiently (7- 150 DPV) in samples; but was detected thereafter till 250 DPV. The most promising effect of immunization with S19GC was observed in a group of cattle with a mixed population of brucellosis negative and positive animals of the above farm. Immunization of this group of animals with 100 μg of S19GC resulted in complete stoppage of shedding as indicated by culture and qPCR. The post immunization anti- LPS and anti-OMP antibody IgG1 and IgG2 response differed (P<0.01) at 30 DPV compared to pre immunization, suggesting the involvement of both Th2 and Th1 cells in the immunity conferred by S19GC vaccine. [ABSTRACT FROM AUTHOR]