Abstract
Longitudinal infection data on Mycobacterium avium subspecies paratuberculosis (MAP) was collected on three dairy farms in Northeastern United States during approximately 10 years. Precise data on animal characteristics and animal location within farm were collected on these farms. Cows were followed over time with regard to MAP status during biannual fecal and serum sampling and quarterly serum sampling. Approximately 13 000 serum samples, 6500 fecal samples and 2000 tissue samples were collected during these years. Prevalence of positive samples was 1.4% for serological samples, 2.2% in fecal samples and 16.7% in tissue samples. Infection dynamics of MAP was studied and resulted in a number of potential changes in our understanding of MAP infection dynamics. First, a high prevalence of MAP infection was observed in these herds due to lifetime follow up of cows, including slaughter. Second, two distinctly different infection patterns were observed, so called non-progressors and progressors. Non-progressors were characterized by intermittent and low shedding of MAP bacteria and a virtual absence of a humoral immune response. Progressors were characterized by continuous and progressive shedding and a clearly detectable and progressive humoral immune response. Strain typing of MAP isolates on the three farms identified on two of three farms a dominant strain type, indicating that some strains are more successful in terms of transmission and infection progression. Continuous high quality longitudinal data collection turned out to be an essential tool in our understanding of pathobiology and epidemiology of MAP infections in dairy herds.
Highlights
Johne’s disease (JD), or paratuberculosis, is a chronic enteric disease of cattle and other ruminants due to an infection with Mycobacterium avium subsp. paratuberculosis (MAP) [1,2]
Herd-level MAP infection prevalence has gradually increased in the past decade; in a recent survey, it was found that 68% of US dairy herds have apparently at least one cow that is infected with MAP [3]
All three farms participated in the Regional Dairy Quality Management Alliance (RDQMA) project, which is a multistate research program conducted under a cooperative research agreement between the USDA Agricultural Research Service (ARS) and four Universities, Cornell University, Pennsylvania State University, University of Pennsylvania, and University of Vermont
Summary
Johne’s disease (JD), or paratuberculosis, is a chronic enteric disease of cattle and other ruminants due to an infection with Mycobacterium avium subsp. paratuberculosis (MAP) [1,2]. Herd-level MAP infection prevalence has gradually increased in the past decade; in a recent survey, it was found that 68% of US dairy herds have apparently at least one cow that is infected with MAP [3]. This estimate was obtained from a survey published by the USDA’s National Animal Health Monitoring System in 2007 [3]. The epidemiology of MAP in dairy herds is difficult to study as the infection shows a very slow progression from initial infection to clinical disease [5]. The best data necessary to understand epidemiology and pathobiology of MAP
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