Lessons leaned from the Michigan Johne's Disease Control Demonstration Project (Proceedings)
The Michigan Johne's Disease Control Demonstration Project is a cooperative program between Michigan State University (MSU), Michigan Department of Agriculture (MDA), and the United States Department of Agriculture (USDA). It is part of a larger disease control demonstration project being conducted in 16 other states. The objective is to demonstrate and investigate management factors that are effective in controlling Johne's Disease (JD). Eight dairy farms and one beef farm are enrolled in the project. Herds represent a variety of housing and management systems. A JD control program was developed for each individual herd. The prevalence of JD in the respective herds is tracked annually through repeated testing. Each herd's control program is reviewed annually and updated as necessary. In addition, several field based research projects are being conducted to develop new knowledge on the control of JD. Below is a summary of some of some of the findings from this project.
Isolation of Mycobacterium Avium Subsp. Paratuberculosis From Recycled Sand
Johne's disease (JD), caused by the bacterium Mycobacterium avium subsp. paratuberculosis (MAP), is a chronic untreatable disease of ruminants. It primarily affects the intestinal tract resulting in chronic diarrhea and weight loss. JD is transmitted to young stock through the ingestion of colostrum, milk or feedstuffs contaminated with MAP or through exposure to MAP contaminated environments. Many dairy farms use sand as a bedding material and new technology has been developed to recycle sand and reuse it. In some instances, recycled sand may be used for bedding of replacement heifers that are most susceptible to infection with MAP. This study was conducted to determine if MAP could be found in recycled sand, thus serving as a source of environmental exposure to susceptible animals.Two dairy farms known to be infected with MAP were used in this study. One farm was visited weekly for 4 weeks during the summer and for 3 weeks during the winter of 2006/2007 (n=7 visits). The other farm was visited once every 6 months from 2004-2006 (n=6 visits). On each farm, a 4 oz sample was collected from the pre sand separation holding area, the post separation recycled sand pile and the post separation organic material holding area (lagoon). Samples were submitted to the Michigan State University Diagnostic Center for Population and Animal Health where they were cultured for MAP using a liquid culture system (TREK ESP II, TREK Diagnostic Systems, Cleveland OH). Positive samples, as determined by the TREK liquid culture system were confirmed by both acid-fast staining and IS900 PCR.
MAP was cultured from 12/13 samples collected from the pre separation holding tanks. Post separation, MAP was cultured from 11/13 and 13/13 of the post separation sand pile and post separation organic material respectively. There was no difference in the frequency of MAP recovery based on farm or season of the year.
This study demonstrates that on infected dairy farms, MAP can be found in recycled sand and can potentially serve as a source of disease exposure if used as bedding for susceptible animals. Veterinarians should recognize this risk when conducting Johne's disease risk assessments and advise their clients on how best to manage recycled sand to reduce risk of MAP transmission. Future studies will attempt to determine how long MAP may remain viable in recycled sand and to identify management strategies to reduce survivability.
Environmental Distribution of Mycobacterium avium supsp. Paratuberculosis On Michigan Dairy Farms
Johne's Disease (JD) is an important infectious disease of cattle caused by Mycobacterium avium subspecies paratuberculosis (MAP). It is estimated that over 50% of US dairy herds are infected with MAP. Environmental contamination with MAP is considered the major reservoir of infection for susceptible cattle. While MAP does not multiply in the environment, it can persist for months in manure, lagoons, manure packs—areas that are found in abundance on most dairy farms—even in below-freezing temperatures. Very little information is published of the distribution of MAP on dairy farms. The objectives of this study were to: 1) perform serial environmental culturing on six Michigan dairy herds, enrolled in a JD control program over several years; 2) characterize the distribution of MAP contamination on dairy farms; and 3) determine if and how that distribution changes as herd fecal culture prevalence changes.