Johne's Disease

Direct Fecal PCR for Mycobacterium avium subsp. paratuberculosis

The Iowa State University Veterinary Diagnostic Laboratory offers direct fecal PCR testing for the detection of Mycobacterium avium subsp. paratuberculosis (MAP) DNA in ruminant feces. Results are available same day/next day, compared with the eight weeks required for liquid fecal culture testing. Sensitivity for the direct PCR is comparable to the culture system for high- and moderate-shedding animals. The test is highly specific for detecting MAP DNA and is able to discriminate between MAP and other fecal Mycobacterium spp. 

Pooled Fecal PCR for Mycobacterium avium subsp. paratuberculosis

ISU VDL commonly performs pooled fecal PCR tests for surveillance of Johne’s disease in cattle herds, to reduce testing costs in low prevalence herds. The test is run similarly to the direct fecal PCR, but allows pooling of up to 5 fecal samples with results available same day/next day. If a pool is positive or suspect, individual testing of samples in that pool can be performed by request to identify positive or suspect individuals.

  1. Guidelines for sample collection from individual animals are outlined below.
  2. Pooling procedures will be completed at the VDL prior to testing.
  3. If individual testing of positive/suspect pools is desired following pooled testing, please indicate this on the submission form or contact the laboratory.

IMPORTANT: When collecting/submitting fecal samples from multiple animals for PCR testing, it is imperative to be as clean as possible to avoid contamination of subsequent samples. PCR tests are remarkably sensitive and cattle with Johne’s disease can shed incredibly high amounts of bacteria in feces; cross-contamination of samples can result in inaccurate testing results and increased testing costs.

Guidelines for Fecal Collection and Submission

All submissions of fecal samples or serum should use the ISU VDL ruminant submission form. Please include unique animal identification, age, breed, and other pertinent information (i.e. stage of lactation, gender) for each sample. PCR testing is performed every business day; most samples are processed on the day of submission with results available that evening. For large herd surveillance cases or those requiring extra organization/biosecurity measures, samples may be processed in the afternoon on the day of submission with results available the next day.

  1. Collect fecal samples directly from the rectum; do not collect ground or floor samples.  
  2. Use a separate clean sleeve/glove to collect each individual sample (moisture/lubricant may adversely affect the quality of the sample).
  3. Place a minimum of 10 grams (1/2 ounce or 1 tablespoon) into a clean, plastic container; we recommend cups or 50ml conical tubes (with screw top lids), Fisher brand Polystyrene Sample Vials (catalog # 03-341-13), or similar containers. Submission of feces in rectal sleeves/gloves is discouraged and may delay testing results.
  4. Use permanent ink to label container with animal ID and premise ID if available.
  5. Place sample containers in a cooler with cold packs and transfer samples to refrigerator or submit samples to the laboratory ASAP. DO NOT FREEZE. Include ice packs to keep samples cool during shipping. Samples should arrive at the lab within 96 hours of collection.
  6. For pooled testing, up to five individual samples from animals of similar ages/lactation/groups can be pooled. POOLING PROCEDURES WILL BE COMPLETED AT THE VDL PRIOR TO TESTING. 

Other testing options for Johne’s disease at ISU VDL

Antibody testing is available on serum, plasma, or milk samples; tests are performed twice weekly. The inclusion of antibody testing in a herd surveillance or clean-up program may help identify positive cattle, particularly those that are not currently shedding or that may be shedding MAP intermittently in feces.

More Information

Powerpoint presentations available for download

Johne’s Disease Control Program

The Iowa Department of Agriculture and Land Stewardship (IDALS) is participating in the National Johne's Disease Control Program, which provides guidelines for detecting infected animals and minimizing risks to herd mates through management practices. The goal of the Johne's Disease Program is to certify Johne's negative herds according to the USDA definitions. Participation in the program is completely voluntary and the confidentiality of test results will be maintained within the limits of Iowa law. For more information, please contact Dr. Gary Eiben (Iowa Johne’s Disease Coordinator) at IDALS (515-669-6095) or your state district veterinarian.

Contact Information

Please feel free to contact Dr. Drew Magstadt (, 515-294-1950) at the ISU VDL with questions/concerns regarding sampling, diagnostic testing, and results or to discuss strategies for herd evaluation.