University of Wisconsin–Madison

MAP in Many Humans

Dr. J. Todd Kuenstner, Pathology and Laboratory Medicine, Lewis Katz School of Medicine, Philadelphia, PA, and colleagues from seven other institutions have reported on the detection of MAP in the blood of people with and without Crohn’s Disease by multiple laboratory assays. Their article appears in the most recent issue of Microorganisms [Open Access, 14 pages with 51 references].


Mycobacterium avium subspecies paratuberculosis (MAP) has long been suspected to be involved in the etiology of Crohn’s disease (CD). An obligate intracellular pathogen, MAP persists and influences host macrophages. The primary goals of this study were to test new rapid culture methods for MAP in human subjects and to assess the degree of viable culturable MAP bacteremia in CD patients compared to controls. A secondary goal was to compare the efficacy of three culture methods plus a phage assay and four antibody assays performed in separate laboratories, to detect MAP from the parallel samples. Culture and serological MAP testing was performed blind on whole blood samples obtained from 201 subjects including 61 CD patients (two of the patients with CD had concurrent ulcerative colitis (UC)) and 140 non-CD controls (14 patients in this group had UC only).

Viable MAP bacteremia was detected in a significant number of study subjects across all groups. This included Pozzato culture (124/201 or 62% of all subjects, 35/61 or 57% of CD patients), Phage assay (113/201 or 56% of all subjects, 28/61 or 46% of CD patients), TiKa culture (64/201 or 32% of all subjects, 22/61 or 36% of CD patients) and MGIT culture (36/201 or 18% of all subjects, 15/61 or 25% of CD patients). A link between MAP detection and CD was observed with MGIT culture and one of the antibody methods (Hsp65) confirming previous studies. Other detection methods showed
no association between any of the groups tested. Nine subjects with a positive Phage assay (4/9) or MAP culture (5/9) were again positive with the Phage assay one year later. This study highlights viable MAP bacteremia is widespread in the study population including CD patients, those with other autoimmune conditions and asymptomatic healthy subjects.


While the high rate of MAP detection in human blood samples is shocking, it is not surprising. MAP has been proven capable of infecting a wide array of animal species, including nonhuman primates. The majority of MAP-infected animals, e.g., cattle, goats and sheep, are used for food. Since food safety regulatory agencies have not declared MAP to be a zoonotic pathogen, those MAP-infected animals, and their products such as milk, legally enter the food supply daily. Multiple studies have detected live MAP in retail pasteurized milk, cheese, and meat. Thus, humans are being exposed every day.

As the concluding sentence of this Dr. Kuenstner’s publication states: “as a minimum measure of best practice, the possibility that MAP is a zoonotic pathogen should prompt public health measures to better control JD and MAP spread into food and the environment by governments worldwide.”

For more on MAP as a human pathogen visit the website of the Human Para Foundation, the organization who funded this study.

Read this for more evidence that MAP is a zoonotic pathogen.

Read this for more on MAP in food and water.