Economic and epidemiological evaluation of Salmonella control in Dutch dairy herds

Wageningen UR, Agricultural Economics Research Institute, P.O. Box 35, 6700 AA Wageningen, The Netherlands.
Preventive Veterinary Medicine (Impact Factor: 2.17). 03/2009; 89(1-2):1-7. DOI: 10.1016/j.prevetmed.2008.12.007
Source: PubMed


This paper presents an analysis of a Salmonella control program for Dutch dairy herds. Salmonella control strategies were evaluated using a computer-based model consisting of an epidemiological module and an economics module. The epidemiological module is a state transition model of the infectivity of a herd, with the unit of analysis being the individual farm. The probability of a herd going from one state in the model to another state was derived from biological characteristics of Salmonella infections in dairy herds, and the presence or absence of risk factors. The economics module was based on partial budgeting. Control measures were modeled as influencing the risk factors. Amongst the measures considered were the prohibition of transporting potentially infectious animals and manure to farms, the culling of chronically infected animals, and herd management measures such as separate housing of groups of animal that differ in age. Alternative strategies, both compulsory and obligatory, were defined and evaluated concerning the reduction of prevalence of infected herds, the cost of a strategy, and cost-effectiveness. Results of the model suggested that a compulsory control strategy which included culling chronically infected animals and prohibiting the transport of potentially infected animals reduces the prevalence of Salmonella positive herds considerably, and was most cost-effective. Adding hygienic measures and a ban on the transport of animal manure further reduces prevalence, but only slightly, and with substantially more costs.

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    • "However, during the last decade, some countries have also started control programs for Salmonella Dublin (S. Dublin) in cattle herds (Bergevoet et al., 2009;Nielsen, 2013). In Sweden, legislated Salmonella control was initiated already in the 1960ies and the program includes all serotypes and all species along the entire chain from feed to food. "
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    ABSTRACT: Legislated Salmonella control in Sweden has been in place since the 1960s. The purpose of this study was to investigate presence of Salmonella antibodies in dairy cattle herds and to provide a basis for decisions on how surveillance and control can be improved. Bulk milk samples from all Swedish dairy herds (n = 4 683) were analysed with two different ELISAs; one detecting antibodies against Salmonella Dublin (Dublin ELISA), and one detecting antibodies against several of the serotypes causing bovine salmonellosis including S. Dublin (Bovine ELISA). Information about herds, i.e. geographical location, local animal density, number of test positive herds within 5 km, animal trade and herd size, was based on register data.
    No preview · Article · Jan 2016 · Preventive Veterinary Medicine
    • "This was not possible with the earlier described methods that focused exclusively on transmission and did not include economic consequences of BVDV infections. Bergevoet et al. (2009) modeled between herd transmission and the subsequent economic consequences of Salmonella for all dairy herds in the Netherlands, and it was decided to use the same modeling approach for BVDV. The aim of this study was to compare the epidemiological and economic consequences of several control scenarios for Dutch dairy herds using a stochastic simulation model. "
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    ABSTRACT: Bovine viral diarrhea virus (BVDV) is an important endemic infection. However, no information was available on whether it would be economically beneficial to implement a national control program in the Netherlands. Therefore, a stochastic simulation model was developed in which control scenarios were added to compare the epidemiological and economic consequences of BVDV control in Dutch dairy herds in the next 10 yr. In the epidemiological part of the model, herds could be classified as susceptible, infectious, recovered, or vaccinated. The outputs of the epidemiological module served as input for the economic module. Net costs that could be attributed to bovine viral diarrhea consisted of production losses, costs for testing, and culling persistently infected cattle in the present voluntary Dutch BVDV control program and costs for vaccination. Four different control scenarios were simulated, involving testing and culling of persistently infected (based on serum or ear-notch testing), and monitoring BVDV statuses and vaccination and were derived from BVDV control programs that are currently executed in Europe. The costs and benefits of BVDV control in the current situation and in each of the simulated control scenarios were evaluated assuming an annual discount rate of 2%. The model estimated a mean BVDV herd prevalence of 18.0% in 2014 and showed a slightly decreasing prevalence over time. The outputs seemed realistic for the present situation in the Netherlands when compared with actual survey data. The average annual net costs associated with bovine viral diarrhea were estimated at €27.8 million for the dairy industry. Two control scenarios were beneficial in controlling BVDV during the study period (between 2015 and 2025). In the scenario where tracing and removing of PI animals and monitoring of the subsequent status was obligatory, the benefit to cost (B/C) ratio was 1.5 (€1.5 benefit for each invested euro). In the scenario in which the BVDV status of all herds was determined, followed by voluntary measures before control measures became obligatory, the B/C ratio was 1.1. The B/C ratio of the scenarios included could be even higher when it was assumed that nondairy herds participated in the control program as well. The model provided the opportunity to compare the effect of voluntary and mandatory control scenarios on the BVDV prevalence and costs and benefits relative to the current situation in the Netherlands. The model was used to support policy makers in their decisions about a BVDV control program.
    No preview · Article · Sep 2015 · Journal of Dairy Science
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    • "enterica serovar Dublin (Salmonella Dublin) is a bacterium that leads to compromised animal health and production losses in cattle herds worldwide (McDonough et al., 1999; Carrique- Mas et al., 2010). Therefore, several countries have initiated research and extended programs for screening and control of this infection in their cattle populations (Veling et al., 2002; Bergevoet et al., 2009; Lewerin et al., 2011). "
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    ABSTRACT: Salmonella Dublin is a bacterium that causes disease and production losses in cattle herds. In Denmark, a surveillance and control program was initiated in 2002 to monitor and reduce the prevalence of Salmonella Dublin. In dairy herds, the surveillance includes herd classification based on bulk tank milk measurements of antibodies directed against Salmonella Dublin at 3-mo intervals. In this study, an "alarm herd" concept, based on the dynamic progression of these repeated measurements, was formulated such that it contains predictive power for Salmonella Dublin herd classification change from "likely free of infection" to "likely infected" in the following quarter of the year, thus warning the farmer 3 mo earlier than the present system. The alarm herd concept was defined through aberrations from a stable development over time of antibody levels. For suitable parameter choices, alarm herd status was a positive predictor for Salmonella Dublin status change in dairy herds, in that alarm herds had a higher risk of changing status in the following quarter compared with nonalarm herds. This was despite the fact that both alarm and nonalarm herds had antibody levels that did not indicate the herds being "likely infected" according to the existing classification system in the present quarter. The alarm herd concept can be used as a new early warning element in the existing surveillance program. Additionally, to improve accuracy of herd classification, the alarm herd concept could be incorporated into a model including other known risk factors for change in herd classification. Furthermore, the model could be extended to other diseases monitored in similar ways.
    Full-text · Article · Oct 2013 · Journal of Dairy Science
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