University of Wisconsin–Madison

Copper vs MAP

Pamela Steuer, working on the laboratory of Miguel Salgado at the Universidad Austral de Chile, published a series of three articles on the effects of copper ions on Mycobacterium avium subsp. paratuberculosis (MAP). This news story summarizes those three articles.


The first study, published in2018 in BMC Microbiology, showed that copper ions resulted in a significant reduction of MAP in suspended in saline (PBS), although some MAP survival on some occasions was observed.

The second study, published in 2020 in the Journal of Applied Microbiology, showed that copper ions have a significant inactivating effect on MAP as well as certain other bacterial communities found in naturally contaminated cow’s milk. However, there were some copper-tolerant MAP strains.

The third study, published in the July 2021 issue of Animals (Open Access), attempted to use copper treatment of milk to prevent infection of calves on farm. Below is the full abstract of that publication.


One of the important routes of Mycobacterium avium subsp. paratuberculosis (MAP) transmission in dairy calves is milk. The aim of the present study was to assess the efficacy of milk treatments to prevent MAP infection transmission to calves. A one-year longitudinal study was carried out. Newborn calves were assigned to one of four experimental groups: 5 calves received naturally MAP-contaminated milk, 5 calves received copper treated milk, 4 calves were fed calf milk replacer, and 3 were fed UHT pasteurized milk. MAP load in milk was estimated. Infection progression was monitored monthly. After one year, calves were euthanized, and tissue samples were cultured and visually examined. MAP was undetectable in milk replacer and UHT milk. Copper ion treatment significantly reduced the number of viable MAP in naturally contaminated milk. Fecal shedding of MAP was observed in all study groups but began earlier in calves fed naturally contaminated milk. Paratuberculosis control programs must place multiple hurdles between the infection source, MAP-infected adult cows, and the most susceptible animals on the farm, young calves. As our study shows, strict dependence on a single intervention to block infection transmission, no matter how important, fails to control this insidious infection on dairy farms.


This series of studies opens new avenues of investigation on use of copper to control of MAP. There are many applications of copper to kill MAP in settings other than the farm that can be explored. However, as the on-farm study showed, controlling MAP in dairy cattle requires multiple complimentary strategies to be effective.

The fact that a Chilean institution studied the effect of copper on MAP is no surprise. Chile produces more than one quarter of the world’s copper and is also by far the country with the largest copper reserves.