Milk quality assurance for paratuberculosis: simulation of within-herd infection dynamics and economics

Abstract

-A bulk milk quality assurance programme for Mycobacterium avium subsp. paratuberculosis (Map) in dairy herds was simulated with a stochastic simulation model (JohneSSim). The aim of this study was to evaluate the epidemiological and economic effects of preventive management measures and various test schemes in a simulated population of closed Dutch dairy herds over a 20-year period. Herds were certified as 'low-Map bulk milk' if, with a certain probability, the concentration of Map in bulk milk did not exceed a maximum acceptable concentration of 10 3 Map organisms per litre (based on pasteurisation studies). The programme started with an initial assessment; test-negative herds entered a surveillance procedure and test-positive herds a control procedure. The simulations showed that herd examinations by ELISA for the initial assessment, surveillance and control procedures effectively ensure the quality of 'lowMap bulk milk': > 75% of simulated herds were certified and > 96% of certified herds produced bulk milk with < 10 3 Map/L if the initial herd-level prevalence was 30%. Preventive management measures only had a minor effect on bulk milk quality of certified herds. Culling based on biennial faecal culture was more effective than culling based on annual ELISA. Average total discounted costs for 20-year participation in a programme consisting of initial assessment by ELISA, surveillance by biennial ELISA and control by biennial faecal culture were e16 × 10 3 per herd.In conclusion, this study shows that a bulk milk quality assurance programme for closed Dutch dairy herds is feasible and provides information on the cost-effectiveness of different programmes. The concepts of this study equally apply to other countries because mechanisms of paratuberculosis infection, disease, and testing are comparable in other dairy cattle populations. dairy cattle / milk / paratuberculosis / stochastic simulation model / quality assurance programme

Modeling the Effect of Direct and Indirect Contamination of On-Farm Bulk Tank Milk with Mycobacterium avium subsp. paratuberculosis

“…The low median concentration of MAP in bulk tank milk was similar to other models (Weber et al, 2008;Boulais et al, 2011). However, the stochastic model enabled infrequent but plausible case scenarios, such as a herd containing a few cows shedding extreme amounts of MAP in feces.…”

“…Previous models for MAP in bulk tank milk have mainly focused on clinically affected animals with obvious high concentrations of MAP in feces and rarely discuss the role of cows in earlier stages of infection (Nauta and van der Giessen, 1998;Weber et al, 2008;Boulais et al, 2011). Taking one step further, a model should also be able to assess the effect of differences in infection prevalence and herd sizes on the level of contamination.…”

Relationship between Presence of Cows with Milk Positive for Mycobacterium avium subsp. paratuberculosis-Specific Antibody by Enzyme-Linked Immunosorbent Assay and Viable M. avium subsp. paratuberculosis in Dust in Cattle Barns

“…paratuberculosis, which disperses inside the barn, as shown previously, and transmission might occur even though animals are not in close contact (10,11,29). The number of ELISA-positive cows detected in farms throughout varied the study (2a to h), because the Dutch Milk Quality Assurance Program started during the sampling period (24). Removal of ELISA-positive animals from a herd is thought to result in a decrease in M. avium subsp.…”

“…All the farms were situated in the northern part of The Netherlands. Paratuberculosis status was identified by using the data from the Intensive Paratuberculosis Program (n ϭ 3) or the Bulk Milk Quality Assurance Program (BMQAP) (n ϭ 5) (23,24). All farms were categorized as high M. avium subsp.…”

Bovine paratuberculosis: recent advances in vaccine development

“…There are concerns that the causative agent is involved in the pathogenesis of human Crohn's disease, a debilitating inflammatory bowel disease (Behr and Kapur 2008). Therefore, dairy industries have installed national programmes to limit human exposure via consumer products, like milk and cheese (Weber et al 2008). Control programmes for paratuberculosis are in need of an effective vaccine (van Schaik et al 1996;Lu et al 2010), but at the moment there is no vaccine registered for use in cattle in the EU.…”