Search

Summary: Foot‐and‐mouth disease (FMD) is an important transboundary disease with substantial economic impacts. Although between‐herd transmission of the disease has been well studied, studies focusing on within‐herd transmission using farm‐level outbreak data are rare. The aim of this study was to estimate parameters associated with within‐herd transmission, host physiological factors and FMD virus (FMDV) persistence using data collected from an outbreak that occurred at a large, organized dairy farm in India. Of 1,836 regularly vaccinated, adult dairy cattle, 222 had clinical signs of FMD over a 39‐day period. Assuming homogenous mixing, a frequency‐dependent compartmental model of disease transmission was built. The transmission coefficient and basic reproductive number were estimated to be between 16.2–18.4 and 67–88, respectively. Non‐pregnant animals were more likely to manifest clinical signs of FMD as compared to pregnant cattle. Based on oropharyngeal fluid (probang) sampling and FMDV‐specific RT‐PCR, four of 36 longitudinally sampled animals (14%) were persistently infected carriers 10.5 months post‐outbreak. There was no statistical difference between subclinical and clinically infected animals in the duration of the carrier state. However, prevalence of NSP‐ELISA antibodies differed significantly between subclinical and clinically infected animals 12 months after the outbreak with 83% seroprevalence amongst clinically infected cattle compared to 69% of subclinical animals. This study further elucidates within‐herd FMD transmission dynamics during the acute‐phase and characterizes duration of FMDV persistence and seroprevalence of FMD under natural conditions in an endemic setting. [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]