title: High herd-level prevalence of Mycobacterium avium subspecies paratuberculosis in Western Canadian dairy farms, based on environmental sampling.
abstract: Mycobacterium avium subspecies paratuberculosis (MAP) causes chronic progressive enteritis in ruminants. The pathogen is present in most countries with modern dairy production, causing substantial economic losses for the industry. The objectives of this study were to estimate dairy herd prevalence of MAP in the Western Canadian provinces of Alberta and Saskatchewan, and to determine whether herd size and housing system (tie-stall versus freestall or loose housing) affected the risk of a herd testing positive for MAP. Six environmental samples were collected on 360 Alberta farms (60% of registered producers) and on 166 Saskatchewan dairy farms (99%). In total, 47% of the sampled farms in Alberta and 53% of the sampled farms in Saskatchewan had at least one environmental sample that was MAP culture positive and were, therefore, defined as infected. Sensitivity of environmental sampling was estimated using 3 subsequent annual tests performed on 82 farms. Because laboratory protocols were continuously improved throughout the project, the sensitivity increased over time. Therefore, a mean of the sensitivity estimates weighted on sampling year was constructed; this resulted in sensitivities of 68 and 69% for Alberta and Saskatchewan, respectively. Implementing those estimates in an approximate Bayesian computation model resulted in a true herd prevalence of 68% (95% probability interval: 60-80%) for Alberta and 76% (95% probability interval: 70-85%) for Saskatchewan. Herds with >200 cows had 3.54 times higher odds of being environmental sample positive and had more positive samples than herds with <50 cows (neither province nor housing system affected those results). In conclusion, the majority of Alberta and Saskatchewan dairy farms were infected with MAP and larger herds were more often MAP positive than smaller herds.
authors.affiliation: Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1. Electronic address: rwolf@ucalgary.ca.
authors.forename: R
authors.initials: R
authors.lastname: Wolf
authors.affiliation: Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: H W
authors.initials: HW
authors.lastname: Barkema
authors.affiliation: Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: J
authors.initials: J
authors.lastname: De Buck
authors.affiliation: Alberta Milk, Edmonton, Alberta, Canada T6X 1H1.
authors.forename: M
authors.initials: M
authors.lastname: Slomp
authors.affiliation: Alberta Milk, Edmonton, Alberta, Canada T6X 1H1.
authors.forename: J
authors.initials: J
authors.lastname: Flaig
authors.affiliation: SaskMilk, Regina, Saskatchewan, Canada S4N 4Y1.
authors.forename: D
authors.initials: D
authors.lastname: Haupstein
authors.affiliation: Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: C
authors.initials: C
authors.lastname: Pickel
authors.affiliation: Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, Alberta, Canada T2N 4N1.
authors.forename: K
authors.initials: K
authors.lastname: Orsel
mesh_terms: D000416:Alberta / Q000453:epidemiology; D000818:Animals; D001499:Bayes Theorem; D002417:Cattle / Q000382:microbiology*; D002418:Cattle Diseases / Q000453:epidemiology* / Q000382:microbiology; D003612:Dairying; D004783:Environmental Microbiology; D005260:Female; D006799:Housing, Animal / Q000592:standards; D016015:Logistic Models; D008372:Manure / Q000382:microbiology; D016927:Mycobacterium avium subsp. paratuberculosis / Q000302:isolation & purification*; D010283:Paratuberculosis / Q000453:epidemiology* / Q000382:microbiology; D015995:Prevalence; D012525:Saskatchewan / Q000453:epidemiology; D012680:Sensitivity and Specificity
chemical_list: D008372:Manure
keywords: Mycobacterium avium ssp. paratuberculosis; environmental sampling; latent class analysis; prevalence