A52-75-2007E.pdf - AgroMedia International Inc

Health61Johne’s disease in Canada Part I: Clinical symptoms,pathophysiology, diagnosis, and prevalence in dairy herdsCorresponding AuthorTiwari, A.Atlantic Veterinary CollegeCollaboratorsVanLeeuwen, J.A.Atlantic Veterinary CollegeMcKenna, S.L.B.Atlantic Veterinary CollegeKeefe, G.P.Atlantic Veterinary CollegeBarkema, H.W.University of CalgaryCanadian Veterinary Journal (2006) Vol. 47 p. 874-882.Johne’s Disease (JD) is an infectious disease caused by Mycobacteriumavium subspecies paratuberculosis (MAP). Although the natural hosts forMAP are wild and domestic ruminants, other wildlife including fox, weasel,crow, rat, mouse, rabbit, hare and badger can also harbour the bacteriaand may contribute to its spread. In cattle, the primary route of infectionis ingestion by calves of MAP from teats, milk, feed and water contaminatedwith faeces. This paper reviews current knowledge about the clinicalstages, pathology and diagnosis of JD as well as its prevalence in Canadiancattle populations. MAP infects the gastrointestinal tract and associatedlymph nodes, limiting nutrient absorption, ultimately resulting in chronicdiarrhea, emaciation, debilitation and death. Subclinical infections causeweight loss and reduced milk production leading to premature culling anddecreased slaughter value. Fertility and udder health may also be negativelyaffected. Currently available diagnostic tests yield many false-negativeand false-positive results, particularly in blood, milk and fecal samplesfrom animals with subclinical infections. Studies of JD prevalence amongdairy herds in 7 Canadian provinces estimated that 37-74% of herds had atleast one animal that tested MAP-positive; 9.8-43.1% had at least 2 MAPpositiveanimals.96 Highlights in Canadian Dairy Cattle Research - 2007