Faecal shedding of Mycobacterium avium subspecies paratuberculosis reduces before parturition in sheep?

Abstract

Paratuberculosis is a disease affecting mainly ruminants, and it is caused by Mycobacterium avium subspecies paratuberculosis (MAP). Control of the disease relies primarily on test-and-removal that is not easy to apply effectively for reasons associated with its pathogenesis. Therefore the aim of this preliminary study was to investigate whether positivity of sheep to MAP-specific antibody and DNA, detected by ELISA and faecal real time polymerase chain reaction (PCR) respectively, varies between specific stages of breeding i.e. before and after parturition, and before the mating season.Rectal faeces (n=120) and whole blood (n=120) samples were collected from a flock of sheep with no record of clinical paratuberculosis. The sheep under study are maintained throughout the year, in isolated confinement with no access to pasture or other animals, and a continuously monitored diet.The proportion of positive animals to real time PCR before parturition (13.9%) was found to be significantly lower (χ2=10.67, P=0.0015) than the proportion of positive animals after parturition (59.5%), and before the mating season (47.6%). The proportion of positive animals after parturition and before the mating season did not differ significantly. PCR analysis of one sample collected from each animal after parturition, allowed detection of more than 71% of the reactors.In conclusion, faecal shedding of MAP detected by real time PCR seems to be decreased before parturition, which probably makes the specific period less suitable for detection of shedders in sheep with no clinical signs of paratuberculosis.