Abstract
Mycobacterial diseases are persistent and characterized by lengthy latent periods. Thus, epidemiological models require careful delineation of transmission routes. Understanding transmission routes will improve the quality and success of control programs. We aimed to study the infection dynamics of Mycobacterium avium subsp. paratuberculosis (MAP), the causal agent of ruminant Johne’s disease, and to distinguish within-host mutation from individual transmission events in a longitudinally MAP-defined dairy herd in upstate New York. To this end, semi-annual fecal samples were obtained from a single dairy herd over the course of seven years, in addition to tissue samples from a selection of culled animals. All samples were cultured for MAP, and multi-locus short-sequence repeat (MLSSR) typing was used to determine MAP SSR types. We concluded from these precise MAP infection data that, when the tissue burden remains low, the majority of MAP infections are not detectable by routine fecal culture but will be identified when tissue culture is performed after slaughter. Additionally, we determined that in this herd vertical infection played only a minor role in MAP transmission. By means of extensive and precise longitudinal data from a single dairy herd, we have come to new insights regarding MAP co-infections and within-host evolution.
Highlights
Mycobacterium avium subsp. paratuberculosis (MAP) is the etiologic agent of Johne’s disease, a chronic granulomatous enteritis causing diarrhea and progressive weight loss in ruminant species.Johne’s disease results in an estimated 250-million-dollar loss annually for the U.S dairy industry, Vet
The dairy herd in this study consisted of approximately 330 milking and dry cows and remained stable in terms of herd size during the years of the study
4004 fecal samples were obtained from 1058 cows in this single dairy herd
Summary
Paratuberculosis (MAP) is the etiologic agent of Johne’s disease, a chronic granulomatous enteritis causing diarrhea and progressive weight loss in ruminant species. Johne’s disease results in an estimated 250-million-dollar loss annually for the U.S dairy industry, Vet. Sci. In addition to adverse impacts on animal welfare and agro-economics, MAP may be of public health significance since it has been implicated as a potential cause of human Crohn’s Disease [2]. MAP is of further relevance from a public health standpoint due to notable parallels between the mechanisms of MAP and M. tuberculosis infections. Both types of infection are characterized by lengthy incubation periods resulting in a large proportion of subclinical cases. The presence of co-infections and their potential clinical importance in both MAP and M. tuberculosis suggests that within-host infection dynamics of MAP could have broad application in understanding the pathobiology of multiple mycobacterial infections [4]
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