|Cook, Kimberly - Kim|
Submitted to: American Association of Bovine Practitioners Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2006
Publication Date: 9/23/2006
Citation: Cook, K.L., Britt, J., Berk, S. 2006. Detection of bovine mycobacterium avium subsp. paratuberculosis in clinical and environmental samples from an infected animal. American Association of Bovine Practitioners Proceedings.
Technical Abstract: Introduction: Mycobacterium avium subsp. paratuberculosis (M. paratuberculosis) causes Johne’s disease, a chronic, enteric infection that is passed from adults to calves via the fecal-oral route. Eradication of M. paratuberculosis from infected farms has been difficult and is likely due to long-term survival of the organism in the environment. However, information is needed to better understand the persistence of the organism in environmental sources (water, soil, protozoa) and the duration of its survival following removal of infected animals. The purpose of this study was to evaluate the occurrence and survival of the organism in clinical and environmental samples obtained from a M. paratuberculosis infected cow and its surroundings. Methods: Quantitative, real-time PCR (QRT-PCR) was used to target the IS900 sequence of M. paratuberculosis in rectal samples taken from the infected animal over a period of 3 months and in tissue samples taken when the animal was posted. Environmental samples were taken from the pen for 3 months while the animal was in the pen and on a weekly basis after its removal. Water and biofilm samples from the animals watering trough were taken for QRT-PCR and for isolation of protozoa. Results: The M. paratuberculosis IS900 sequence was detected in fecal samples taken from the infected animal over a 3 month period (1.0 x 107 to 3.8 X 107 cells gram-1), however, the concentration increased an order of magnitude (1.8 X 108 cells gram-1) the month the animal went clinical with the disease. The concentration of M. paratuberculosis in tissue samples from the animal was highest in the small intestine (5.5 X 107 and 5.7 X 107 cells gram-1 in the ileum and jejunum, respectively). However, M. paratuberculosis could not be detected in the rumen. M. paratuberculosis was detected in soil, fecal, biofilm and water samples taken from the pen. Protozoa (an Acanthamoeba strain) isolated from the watering trough were shown by confocal microscopy to take up and retain large numbers of M. paratuberculosis, and QRT-PCR revealed that the cell concentration increased 3-fold upon incubation with the protozoa. Environmental samples taken weekly since removal of the animal from the pen have retained high concentrations of M. paratuberculosis (1.2 X 108 cells gram-1 to 4.0 X 108 cells gram-1). Significance: These results suggest the M. paratuberculosis survives in high concentrations in diverse sources within the environment occupied by the infected animal. M. paratuberculosis does not appear to survive in the rumen, but is present in high concentrations in both the small intestine and rectal colon of infected animals. Survival of the organism in protozoa isolated from the farm suggests that watering troughs (and associated protozoa) may serve as a hidden reservoir and source of infection.