title: Economic aspects of disease monitoring with special reference to bovine paratuberculosis.
abstract: Monte Carlo simulation models were used to evaluate the feasibility and potential results of a proposed national survey of the prevalence of bovine paratuberculosis (PTB) in dairy herds in Norway. The expected herd prevalence was assumed to be 0.2% in the simulations. Infected herds were classified as detected if 1 animal was sero-positive. With a sample size of 6000 herds at least 1 truly infected herd was detected in 99% of the iterations. The low sensitivity of the ELISA test, the assumed low herd prevalence, the typical low within-herd prevalence of PTB and the small herd sizes in Norway all present problems in detection of the disease. The results showed that the ratio between false-positive herds and true positive herds detected had a median of 70:1. At the assumed herd prevalence of 0.2% and a cost/test of 70 NOK the median cost of detecting 1 infected herd was approximately 900,000 NOK. If 2 positive reactors were needed to classify a herd "infected" the median cost of detecting 1 infected herd was 5,055,000 NOK. Our results suggest that a randomized national prevalence survey would not be feasible, due to the low probability of detecting infected herds and because of the high number of false-positive reactions that would be expected.
authors.affiliation: Danish Veterinary Laboratory, Bülowsvej 27, DK-1790 Copenhagen V, Denmark. lpa@svs.dk
authors.forename: L G
authors.initials: LG
authors.lastname: Paisley
mesh_terms: D000818:Animals; D002417:Cattle; D003612:Dairying; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D005240:Feasibility Studies; D008403:Mass Screening / Q000191:economics*; D009010:Monte Carlo Method; D016927:Mycobacterium avium subsp. paratuberculosis / Q000276:immunology / Q000302:isolation & purification; D009664:Norway / Q000453:epidemiology; D010283:Paratuberculosis / Q000453:epidemiology* / Q000517:prevention & control*; D015995:Prevalence