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Location: Infectious Bacterial Diseases Research

Title: Differences in intermittent and continuous fecal shedding patterns between natural and experimental Mycobacterium avium subspecies paratuberculosis infections in cattle

item Mitchell, Rebecca - Centers For Disease Control And Prevention (CDCP) - United States
item Schukken, Ynte - Cornell University - New York
item Koets, Ad - Institute For Animal Health - Netherlands
item Weber, Maarten - Gd Animal Health Service
item Bakker, Douwe - Institute For Animal Health - Netherlands
item Stabel, Judith
item Louzouon, Yoram - Bar-Ilan University

Submitted to: Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2015
Publication Date: 6/19/2015
Citation: Mitchell, R.M., Schukken, Y., Koets, A., Weber, M., Bakker, D., Stabel, J.R., Louzouon, Y. 2015. Differences in intermittent and continuous fecal shedding patterns between natural and experimental Mycobacterium avium subspecies paratuberculosis infections in cattle. Veterinary Research. 46:66. doi: 10.1186/s13567-015-0188-x.

Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle characterized by diarrhea, reduced feed intake, weight loss and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced milk production by these animals, they also present a potential infective threat to the rest of the herd. As the disease progresses from a latent, asymptomatic stage to a more advanced stage shedding of the bacteria into the feces increases dramatically. Understanding the shedding patterns of infected animals will help us understand how the disease progresses. This paper develops a model to explain the dynamics of fecal shedding of the and how this relates to the occurrence of clinical disease. More fully understanding this disease will allow us develop control measures to prevent the spread of infection.

Technical Abstract: The objective of this paper is to study shedding patterns of cows infected with Mycobacterium avium subsp. paratuberculosis (MAP). While multiple single farm studies of MAP dynamics were reported, there is not large-scale meta-analysis of both natural and experimental infections. Large differences in shedding patterns between experimentally and naturally infected cows were observed. Experimental infections are thus probably driven by different pathological mechanisms. For further evaluations of shedding patterns only natural infections were used. Within such infections, the transition to high shedding was studied as a proxy to the development of a clinical disease. The majority of studied cows never developed high shedding levels. Those that do, typically never reduced their shedding level to low or no shedding. Cows that eventually became high shedders showed a pattern of continuous shedding. In contrast, cows with an intermittent shedding pattern had a low probability to ever become high shedders. In addition, cows that start shedding at a younger age (less than three years of age) have a lower hazard of becoming high shedders compared to cows starting to shed at an older age. These data suggest the presence of three categories of immune control. Cows that are intermittent shedders have the infection process under control (no progressive infection). Cows that start shedding persistently at a young age partially control the infection, but eventually will be high shedders (slow progressive infection), while cows that start shedding persistently at an older age cannot effectively control the infection and become high shedders rapidly.