Shedding of Mycobacteriumavium subspecies paratuberculosis bacteria by natural infected dairy calves before first calving

Abstract

Mycobacterium avium subspecies paratuberculosis (MAP) is the causal agent of Johne’s disease. Most on farm control measurements against the spread of MAP aim to reduce the transmission between cow and calf. This research focusses on the spreading of MAP between young stock on infected farms. The aim of the study was to determine the proportion of young stock shedding viable MAP bacteria on infected farms and to determine the agreement between the two PCR methods used. 13 known infected farms were included in the research. Fecal samples were taken from the rectum of all young stock before first calving. Bull calves present on the farm were included. 2122 samples were analyzed by qPCR, using primers targeting the MAP specific IS900 and F57 sequences in two different runs. 147 (6,9%) samples were positive on IS900 PCR and 31 (1,5%) samples were positive on F57 PCR. 11 samples (0,5%) were positive on both target genes. The agreement beyond chance between IS900 and F57 was poor (κ=0.102).