A preliminary study investigating effects of oral monensin sodium in an enteric Mycobacterium avium ssp. Paratuberculosis infection model of calves

摘要

Mycobacterium avium ssp. paratuberculosis (MAP)is the causative agent of Johne’s disease, an entericinfection of ruminants that causes significant economicburden for dairy and beef producers. Efforts to controlMAP in endemic herds typically focus on herd managementpractices such as limiting exposure or early cullingof infected animals and, occasionally, vaccination.The ionophore monensin sodium may have protectiveeffects against MAP both in vivo and in vitro; however,this has not been thoroughly evaluated experimentally.Using a direct intestinal MAP challenge model, we haveobserved similarities regarding persistence of MAP intissues and apparent resilience to infection comparedwith experimental oral infection or natural disease.Here we sought to investigate the effects of oral monensinsupplementation in experimentally MAP-infectedcalves. We examined the persistence of MAP in theintestinal tissues, MAP-induced intestinal inflammation,fecal MAP shedding, and seroconversion usinga commercial serologic assay. Monensin-supplementedMAP-infected calves demonstrated evidence for resilienceto MAP infection earlier in this study comparedwith monensin-free MAP-infected calves. However,statistical modeling did not identify a significant effectof monensin on outcomes of infection, and more workis required to understand how monensin affects earlytissue colonization of MAP in calves.