Abstract:
Uptake of Mycobacterium avium subsp. paratuberculosis (MAP) by calves in the first days of life from colostrum, milk
and faeces is regarded an important moment of transmission. The objective of this study was to quantify the
association between the MAP status of dams as determined by the presence of MAP DNA and antibody in colostrum
and that of DNA in faeces and the environment with subsequent MAP shedding of their daughters. A cohort of 117
dam-daughter pairs giving birth/being born on eight commercial dairy farms with endemic paratuberculosis was
followed where colostrum, faecal and environmental samples (dust) were analysed for the presence of MAP using an
IS900 real-time PCR. Antibodies in colostrum were measured by ELISA. Analysis of dust samples showed that on all
farms environmental MAP exposure occurred continuously. In significantly more colostrum samples (48%) MAP DNA
was detected compared to faecal samples (37%). MAP specific antibodies were present in 34% of the colostrum
samples. In total MAP DNA was present in faecal samples of 41% of the daughters at least once during the sampling
period. The association between faecal shedding in the offspring and the dam MAP status defined by MAP PCR on
colostrum, MAP PCR on faeces or ELISA on colostrum was determined by an exact cox regression analysis for discrete
data. The model indicated that the hazard for faecal shedding in daughters born to MAP positive dams was not
significantly different compared to daughters born to MAP negative dams. When born to a dam with DNA positive
faeces the HR was 1.05 (CI 0.6; 1.8) and with DNA positive colostrum the HR was 1.17 (CI 0.6; 2.3). When dam status
was defined by a combination of both PCR outcomes (faeces and colostrum) and the ELISA outcome the HR was
1.26 (CI 0.9; 1.9). Therefore, this study indicates that neither the presence of MAP DNA in colostrum, MAP DNA in
faeces nor the presence of MAP antibodies in colostrum of the dam significantly influences the hazard of MAP
shedding in their subsequent daughters up to the age of two years when raised in a contaminated environment.
