Cost-effectiveness analysis of using probiotics, prebiotics, or synbiotics to control Campylobacter in broilers.

Campylobacter is a food safety hazard, which causes a substantial human disease burden. Infected broiler meat is a common source of campylobacteriosis. The use of probiotics, prebiotics, or synbiotics has been associated with controlling Campylobacter infections in broilers, although efficacy remains a contentiously debated issue. On-farm use of probiotics, prebiotics, or synbiotics is gaining momentum. Therefore, it is interesting to analyze the economic viability of this potential intervention to reduce Campylobacter prevalence in broilers. A normative cost-effectiveness analysis was conducted to estimate the cost-effectiveness ratio of using probiotics, prebiotics, or synbiotics in broiler production in Denmark, the Netherlands, Poland, and Spain. The cost-effectiveness ratio was defined as the estimated costs of probiotics, prebiotics, or synbiotics use divided by the estimated public health benefits expressed in euro (€) per avoided disability-adjusted life year (DALY). The model considered differences between the countries in zootechnical and economic farm performance, in import, export, and transit of live broilers, broiler meat and meat products, and in disease burden of Campylobacter-related human illness. Simulation results revealed that the costs per avoided DALY were lowest in Poland and Spain (€4,000-€30,000 per avoided DALY) and highest in the Netherlands and Denmark (€70,000-€340,000 per avoided DALY) at an efficacy ranging from 10 to 20%. In Poland and Spain, using probiotics can be classified as a moderately expensive intervention if efficacy is more than 10%, otherwise it is relatively expensive. In the Netherlands and Denmark, using probiotics is a relatively expensive intervention irrespective of efficacy. However, if probiotics, prebiotics, or synbiotics were assumed to enhance broiler performance, it would become a relatively cost-effective intervention for Campylobacter even at low efficacy levels of 1 to 10%.

Economic aspects of Q fever control in dairy goats.

This paper presents an economic analysis of Q fever control strategies in dairy goat herds in The Netherlands. Evaluated control strategies involved vaccination strategies (being either preventive or reactive) and reactive non-vaccination strategies (i.e., culling or breeding prohibition). Reactive strategies were initiated after PCR positive bulk tank milk or after an abortion storm (abortion percentage in the herd of 5% or more). Preventive vaccination eradicates Q fever in a herd on average within 2 and 7 years (depending on breeding style and vaccination strategy). Economic outcomes reveal that preventive vaccination is always the preferred Q fever control strategy on infected farms and this even holds for a partial analysis if only on-farm costs and benefits are accounted for and human health costs are ignored. Averted human health costs depend to a large extend on the number of infected human cases per infected farm or animal. Much is yet unknown with respect to goat-human transmission rates. When the pathogen is absent in both livestock and farm environment then the "freedom of Q fever disease" is achieved. This would enable a return to non-vaccinated herds but more insight is required with respect to the mechanisms and probability of re-infection.

Controlling highly pathogenic avian influenza outbreaks: An epidemiological and economic model analysis.

Outbreaks of highly pathogenic avian influenza (HPAI) can cause large losses for the poultry sector and for animal disease controlling authorities, as well as risks for animal and human welfare. In the current simulation approach epidemiological and economic models are combined to compare different strategies to control highly pathogenic avian influenza in Dutch poultry flocks. Evaluated control strategies are the minimum EU strategy (i.e., culling of infected flocks, transport regulations, tracing and screening of contact flocks, establishment of protection and surveillance zones), and additional control strategies comprising pre-emptive culling of all susceptible poultry flocks in an area around infected flocks (1 km, 3 km and 10 km) and emergency vaccination of all flocks except broilers around infected flocks (3 km). Simulation results indicate that the EU strategy is not sufficient to eradicate an epidemic in high density poultry areas. From an epidemiological point of view, this strategy is the least effective, while pre-emptive culling in 10 km radius is the most effective of the studied strategies. But these two strategies incur the highest costs due to long duration (EU strategy) and large-scale culling (pre-emptive culling in 10 km radius). Other analysed pre-emptive culling strategies (i.e., in 1 km and 3 km radius) are more effective than the analysed emergency vaccination strategy (in 3 km radius) in terms of duration and size of the epidemics, despite the assumed optimistic vaccination capacity of 20 farms per day. However, the total costs of these strategies differ only marginally. Extending the capacity for culling substantially reduces the duration, size and costs of the epidemic. This study demonstrates the strength of combining epidemiological and economic model analysis to gain insight in a range of consequences and thus to serve as a decision support tool in the control of HPAI epidemics.

Risk-based audit selection of dairy farms.

Dairy farms are audited in the Netherlands on numerous process standards. Each farm is audited once every 2 years. Increasing demands for cost-effectiveness in farm audits can be met by introducing risk-based principles. This implies targeting subpopulations with a higher risk of poor process standards. To select farms for an audit that present higher risks, a statistical analysis was conducted to test the relationship between the outcome of farm audits and bulk milk laboratory results before the audit. The analysis comprised 28,358 farm audits and all conducted laboratory tests of bulk milk samples 12 mo before the audit. The overall outcome of each farm audit was classified as approved or rejected. Laboratory results included somatic cell count (SCC), total bacterial count (TBC), antimicrobial drug residues (ADR), level of butyric acid spores (BAB), freezing point depression (FPD), level of free fatty acids (FFA), and cleanliness of the milk (CLN). The bulk milk laboratory results were significantly related to audit outcomes. Rejected audits are likely to occur on dairy farms with higher mean levels of SCC, TBC, ADR, and BAB. Moreover, in a multivariable model, maxima for TBC, SCC, and FPD as well as standard deviations for TBC and FPD are risk factors for negative audit outcomes. The efficiency curve of a risk-based selection approach, on the basis of the derived regression results, dominated the current random selection approach. To capture 25, 50, or 75% of the population with poor process standards (i.e., audit outcome of rejected), respectively, only 8, 20, or 47% of the population had to be sampled based on a risk-based selection approach. Milk quality information can thus be used to preselect high-risk farms to be audited more frequently.

Economic assessment of Q fever in the Netherlands.

In this paper the economic impact of controlling the Q fever epidemic in 2007-2011 in the Netherlands is assessed. Whereas most of the long-term benefits of the implemented control programme stem from reduced disease burden and human health costs, the majority of short-term intervention costs were incurred in the dairy goat sector. The total intervention cost in agriculture amounted approximately 35,000 Euro per DALY occurred. By culling of infected animals, breeding prohibition and vaccination, the epidemic seems to be under control. As the dairy goat vaccination programme continues, future expenses in maintaining the current protected status are relatively low.

Modelling risk aversion to support decision-making for controlling zoonotic livestock diseases.

Zoonotic infectious livestock diseases are becoming a significant burden for both animal and human health and are rapidly gaining the attention of decision-makers who manage public health programmes. If control decisions have only monetary components, governments are generally regarded as being risk-neutral and the intervention strategy with the highest expected benefit (lowest expected net costs) should be preferred. However, preferences will differ and alternative intervention plans will prevail if (human) life and death outcomes are involved. A rational decision framework must therefore consider risk aversion in the decision-maker and controversial values related to public health. In the present study, risk aversion and its impact on both the utility for the monetary component and the utility for the non-monetary component is shown to be an important element when dealing with emerging zoonotic infectious livestock diseases and should not be ignored in the understanding and support of decision-making. The decision framework was applied to several control strategies for the reduction of human cases of brucellosis (Brucella melitensis) originating from sheep in Turkey.

Comparing risk in conventional and organic dairy farming in the Netherlands: an empirical analysis.

This study was undertaken to contribute to the understanding of why most dairy farmers do not convert to organic farming. Therefore, the objective of this research was to assess and compare risks for conventional and organic farming in the Netherlands with respect to gross margin and the underlying price and production variables. To investigate the risk factors a farm accountancy database was used containing panel data from both conventional and organic representative Dutch dairy farms (2001-2007). Variables with regard to price and production risk were identified using a gross margin analysis scheme. Price risk variables were milk price and concentrate price. The main production risk variables were milk yield per cow, roughage yield per hectare, and veterinary costs per cow. To assess risk, an error component implicit detrending method was applied and the resulting detrended standard deviations were compared between conventional and organic farms. Results indicate that the risk included in the gross margin per cow is significantly higher in organic farming. This is caused by both higher price and production risks. Price risks are significantly higher in organic farming for both milk price and concentrate price. With regard to production risk, only milk yield per cow poses a significantly higher risk in organic farming.

Perceived risk and strategy efficacy as motivators of risk management strategy adoption to prevent animal diseases in pig farming.

For Dutch fattening pig farms, this study explored (1) farmers' perceptions towards animal disease risks and animal health risk management; (2) factors underlying farmers' adoption of the two risk management strategies, namely, biosecurity measures and animal health programs. The risks included endemic and epidemic diseases. Data were obtained through a questionnaire (n=164). A behavioral model was developed using the Health Belief Model and tested using structural equation modeling. Endemic and epidemic diseases were regarded as an operational and catastrophic risk, respectively. Farmers considered severity of epidemics as slightly more important, compared to endemics. For both disease categories, farmers valued biosecurity measures as a more effective strategy than animal health programs. In the behavioral model, perceived benefits in terms of strategy efficacy was the strongest direct predictor of strategy adoption. Other behavioral components had a minor indirect effect, namely, via perceived benefits, and only in case of biosecurity measures. The indirect effect path did, however, vary per disease category. For endemics, such a path captured the effect of perceived susceptibility on perceived benefits mediated by perceived severity. For epidemics, it only captured the effect of perceived severity on perceived benefits. The results also revealed the importance of innate risk characteristics of farmers in their adoption decisions. In particular, general self-protection behavior directly contributed to decisions to adopt a certain strategy. The obtained knowledge highlights possible ways of improvement of programs aimed at promoting effective risk management strategies.

Process audits versus product quality monitoring of bulk milk.

Assessment of milk quality is based on bulk milk testing and farm certification on process quality audits. It is unknown to what extent dairy farm audits improve milk quality. A statistical analysis was conducted to quantify possible associations between bulk milk testing and dairy farm audits. The analysis comprised 64.373 audit outcomes on 26,953 dairy farms, which were merged with all conducted laboratory tests of bulk milk samples 12 mo before the audit. Each farm audit record included 271 binary checklist items and 52 attention point variables (given to farmers if serious deviations were observed), both indicating possible deviations from the desired farm situation. Test results included somatic cell count (SCC), total bacterial count (TBC), antimicrobial drug residues (ADR), level of butyric acid spores (BAB), freezing point depression (FPD), level of free fatty acid (FFA), and milk sediment (SED). Results show that numerous audit variables were related to bulk milk test results, although the goodness of fit of the models was generally low. Cow hygiene, clean cubicles, hygiene of milking parlor, and utility room were positively correlated with superior product quality, mainly with respect to SCC, TBC, BAB, FPD, FFA, and SED. Animal health or veterinary drugs management (i.e., drug treatment recording, marking of treated animals, and storage of veterinary drugs) related to SCC, FPD, FFA, and SED. The availability of drinking water was related to TBC, BAB, FFA, and SED, whereas maintenance of the milking equipment was related mainly to SCC, FPD, and FFA. In summary, bulk milk quality and farm audit outcomes are, to some degree, associated: if dairy farms are assessed negatively on specific audit aspects, the bulk milk quality is more likely to be inferior. However, the proportion of the total variance in milk test results explained by audits ranged between 4 and 13% (depending on the specific bulk milk test), showing that auditing dairy farms provides additional information but has a limited association with the outcome of a product quality control program. This study suggests that farm audits could be streamlined to include only relevant checklist items and that bulk milk quality monitoring could be used as a basis of selecting farms for more or less frequent audits.

Multi Criteria Decision Making to evaluate control strategies of contagious animal diseases.

The decision on which strategy to use in the control of contagious animal diseases involves complex trade-offs between multiple objectives. This paper describes a Multi Criteria Decision Making (MCDM) application to illustrate its potential support to policy makers in choosing the control strategy that best meets all of the conflicting interests. The presented application focused on the evaluation of alternative strategies to control Classical Swine Fever (CSF) epidemics within the European Union (EU) according to the preferences of the European Chief Veterinary Officers (CVO). The performed analysis was centred on the three high-level objectives of epidemiology, economics and social ethics. The appraised control alternatives consisted of the EU compulsory control strategy, a pre-emptive slaughter strategy, a protective vaccination strategy and a suppressive vaccination strategy. Using averaged preference weights of the elicited CVOs, the preference ranking of the control alternatives was determined for six EU regions. The obtained results emphasized the need for EU region-specific control. Individual CVOs differed in their views on the relative importance of the various (sub)criteria by which the performance of the alternatives were judged. Nevertheless, the individual rankings of the control alternatives within a region appeared surprisingly similar. Based on the results of the described application it was concluded that the structuring feature of the MCDM technique provides a suitable tool in assisting the complex decision making process of controlling contagious animal diseases.

Awareness and perceived value of economic information in controlling somatic cell count.

A survey of dairy farmers assessed whether they were aware of the potential production and economic benefits of adopting and implementing efficient practices to control somatic cell count (SCC), and whether providing them with additional information on projected economic losses on a regular basis might motivate them to implement enhanced control programmes. In-depth interviews revealed that the majority of the dairy farmers perceived cow-specific and herd-specific projected losses due to elevated SCCs, as not very relevant to them. Farmers considered that SCC was already monitored regularly at individual cow level, which provided them with adequate information to support decision-making. The farmers justified their actions with regard to SCC control in terms of their intention to manage the problem, and their belief in whether their efforts would be successful. Actions were rationalised in a specific context comprising the intertwined notions of intentions and efficacy beliefs.

Selection of critical factors for identifying emerging food safety risks in dynamic food production chains.

A pro-active emerging risk identification system starts with the selection of critical factors related to the occurrence of emerging hazards. This paper describes a method to derive the most important factors in dynamic production chains starting from a gross list of critical factors. The method comprised the semi-quantitative evaluation of the critical factors for a relatively novel product on the Dutch market and a related traditional product. This method was tested in an expert study with three case studies. The use of group discussion followed by individual ranking in an expert study proved to be a powerful tool in identifying the most important factors for each case. Human behaviour (either producers' behaviour or human knowledge) was the most important factor for all three cases. The expert study showed that further generalization of critical factors based on product characteristics may be possible.

Stochastic efficiency analysis of bovine tuberculosis-surveillance programs in the Netherlands.

We constructed a stochastic bio-economic model to determine the optimal cost-efficient surveillance program for bovine tuberculosis. The surveillance programs differed in combinations of one or more detection methods and/or sampling frequency. Stochastic input variables in the epidemiological module described the dynamics of infection and the probability of detection. By means of an efficiency frontier, the trade-off between the expected cost and the epidemiological risk parameter relating to the outbreak size was evaluated. The surveillance scheme based on visual inspection of lesions on carcasses at slaughter was optimal given the current prevalence of the disease in the Netherlands if the objective was to minimise the expected costs. However, the efficient set also included two other schemes: slaughterhouse inspection in combination with GAMMA-interferon testing of blood samples and slaughterhouse inspection in combination with two-stage tuberculin testing. The choice ultimately will depend on the risk attitude of the decision-maker; a more-stringent surveillance scheme will be enforced if the expected outbreak size is to be constrained. In future scenarios, ELISA testing of bulk-tank milk in combination with the current slaughterhouse inspection procedure would outperform the surveillance scheme of solely slaughterhouse inspection if ELISA testing of bulk-tank milk becomes feasible.

Evaluation of surveillance strategies for bovine tuberculosis (Mycobacterium bovis) using an individual based epidemiological model.

The Netherlands holds the bovine tuberculosis-free (BTB-free) status according to European Union standards, but in recent years small outbreaks of the infection have occurred. After the last outbreak in 1999 with 10 infected herds the question raised if the current surveillance system, visual inspection of carcasses at the slaughterhouse, is efficient enough to detect infected cattle in time and to maintain the official BTB-free status. Through epidemiological modelling, the risk of a major outbreak is quantified, using one of six surveillance strategies. These are the currently used visual inspection of carcasses at the slaughterhouse (SL), the ELISA test on blood samples of carcasses at the slaughterhouse (ELISA-B), the gamma-interferon test on blood samples of carcasses at the slaughterhouse (GAMMA-B), comparative tuberculination of the herd (CT), the combined method of single and comparative tuberculination of the herd (ST+CT) and the ELISA test on samples of bulk milk (ELISA-M). Test frequency of the last three methods was varied as well. A stochastic individual based model (IBM) was developed to simulate a chain of infected herds, where each individual animal is followed in time. The model mimics the nation-wide situation after the introduction of one infected animal into one herd. BTB-transmission is simulated with an S-E(1)-E(2)-I state transition model. Output is time until detection of the infection, prevalence in the detected herd and the number of infected herds at the time of detection. For the assessment 500 simulations were used, representing 500 BTB-introductions. Model robustness to parameter values was analysed with Monte Carlo elasticity analysis, for which 1000 simulations were used. Results of median time until detection and median number of infected farms at detection for SL (302 weeks and seven farms) were in agreement with estimates from an outbreak in the Netherlands in 1999. ELISA-B and GAMMA-B performed better than SL with a much lower median time until detection (189 and 97 weeks, respectively). The results for the tuberculination methods (ST+CT and CT) and ELISA-M depended heavily on the frequency in which the tests were performed. The tuberculination methods ST+CT and CT yield comparable results and detect the infection sooner than SL, also at the lowest tested frequency of once in 5 years. ELISA-M is comparable with SL at frequencies of once in 4 or 5 years, and this test works well at frequencies of once a year or higher. Our study results are used for an economical optimisation analysis of the six surveillance strategies.