Protective Efficacy of BCG Vaccination in Calves Vaccinated at Different Ages

Abstract

Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB), is a globally prevalent pathogen with significant animal welfare, economic and public health impacts. In the UK, the control of bTB relies on detection via tuberculin skin tests with ancillary interferon gamma (IFN-γ) release assays, followed by culling infected animals. Vaccination with Bacille Calmette–Guérin (BCG) could be an important element of bTB control, and a number of studies have demonstrated its protective efficacy, particularly when young calves are vaccinated. Here, we compared immune responses and the protective efficacy of BCG in calves vaccinated within the first day of life and at three weeks of age. Significant protection from M. bovis infection was observed in BCG-vaccinated calves compared to non-vaccinated, age-matched controls. No significant differences were shown between calves vaccinated at one day and at three weeks of age when assessing the protective efficacy of BCG (measured as a reduction in lesions and bacterial burden). Antigen-specific IFN-γ levels were similar between the BCG-vaccinated groups, but significantly different from the non-vaccinated control animals. Antigen-specific IFN-γ expression post-BCG vaccination was correlated significantly with protection from M. bovis infection, whereas IFN-γ levels post-challenge correlated with pathology and bacterial burden. These results indicate that early-life vaccination with BCG could have a significant impact on M. bovis infection and, therefore, bTB incidence, and they demonstrate that age, at least within the first month of life, does not significantly impact the protective effect of vaccination.

Development of lateral flow assays to detect host proteins in cattle for improved diagnosis of bovine tuberculosis

“…Despite this, when a NUM score cutoff of 3 is considered the cutoff for M. bovis infection, all M. bovis challenged and naïve animals (except for the one with high ratios for medium stimulation) from this cohort were correctly classified while showing a range of positive and negative results among the vaccinated and challenged cohort NUM scores (1–5). The latter is expected and indicates the amply described partial protection conferred by BCG after a virulent challenge ( 31 , 33 , 47 ).…”

“…The animal cohorts and their respective samples used in this study were described previously ( 30 , 31 ). Briefly, animals were either bTB naïve ( n = 16); M. bovis experimentally challenged with strain AF 2122/97 ( 32 ) ( n = 9); BCG vaccinated (with BCG Pasteur ~1 × 10 6 CFU/calf; n = 10); or BCG vaccinated and subsequently M. bovis challenged ( n = 12) ( 30 ).…”

“…We acknowledge H. Martin Vordermeier and Chris J. Howard for their input into the original studies, from which the samples were derived. These studies were performed at the Institute for Animal Health, Compton, to compare the efficacy of two BCG strains ( 33 ) and the age of BCG administration in calves ( 31 ).…”

Zoonotic Diseases Caused by Mastitic Milk

“…Respiratory tract is infected in both direct and indirect contact. A very small dose can cause the infection through respiration that can be 1000 times less than the intestinal route (Hope et al 2023).…”