The most important route of Mycobacterium avium subsp. paratuberculosis (MAP) transmission in cattle, is fecal-oral and milk is regarded as an important vehicle for MAP transmission to dairy calves. Pamela Steuer and her colleagues at the Universidad Austral de Chile working with Michael T. Collins, University of Wisconsin Madison School of Veterinary Medicine, have studied the efficacy of treatments for milk being fed to calves as a means of preventing MAP infection transmission.
The study was a one-year longitudinal study and was carried out on a Chilean dairy farm. New-born calves were assigned to one of four experimental groups. Five calves received naturally MAP-contaminated milk. For comparison, 5 calves received the same milk after treatment with copper ions, 4 calves were fed commercial calf milk-replacer and 3 were fed UHT treated milk. MAP concentrations were estimated for copper-treated and untreated milk. Infection progression was monitored monthly. After one year, calves were euthanized, and tissue samples were cultured and visually examined.
The authors found that MAP was undetectable in calf milk replacer and UHT milk. Copper ions treatment significantly reduced the number of viable MAP in naturally contaminated milk. Fecal shedding of MAP was observed in all study groups, but the group of calves fed untreated, naturally contaminated milk began to shed MAP earlier than the rest.
Pamela Steuer and her colleagues concluded that strict dependence on a single intervention to block infection transmission, no matter how important, may fail to control this insidious infection on dairy farms. To be successful, paratuberculosis control programs must use multiple methods to interrupt infection transmission between the source, MAP-infected adult cows, and the most susceptible animals on the farm, young calves.
This article can be downloaded as a preprint from https://doi.org/10.21203/rs.3.rs-72767/v1 . This preprint is under consideration at BMC Veterinary Research.