Different ways to examine the economic effects of diseases exist. In this report, the focus is on two types of costs: 1) the costs of preventing a salmonella outbreak and 2) the costs caused by salmonella outbreaks and contaminations due to the salmonella contamination of pig feed. The feed and pork production chain from feed import
to consumers is included. The costs of preventing salmonella include the cost of feed treatment measures, cleaning measures, pest control, measures by authorities (statutory salmonella sampling and official control checks), and self-monitoring measures related to the salmonella control of different operators. Precise cost factors are defined more specifically when reviewing the different operators in the feed and pig sectors. The benefits of the salmonella control program are due to avoided costs caused by salmonella contaminations. When a more efficient control program is implemented, fewer human infections and contamination events occur along the supply chain, thus reducing the cost of illness in humans and contamination in the food chain. In an efficient program, more costs of contamination are saved than the preventive and monitoring costs of the program when compared to a situation with a less efficient or no program (Figure 6).
Figure 6. An illustration of the principle of how a more efficient salmonella control program increases monitoring and prevention costs and decreases costs caused by salmonella contaminations in different phases of the supply chain.
We first calculate the total annual costs (L) incurred by control and preventive measures plus costs caused by salmonella contaminations and human infections in Finland in each scenario:
where h is an index representing one of H cost items or measures associated with preventive or monitoring costs; Ch refers to the total costs of measure or item h which is implemented fully or partly because of the goal of reducing salmonella 𝐿𝐿 = � 𝑃𝑃ℎ𝐶𝐶ℎ+
𝐻𝐻 ℎ=1
� 𝑝𝑝𝑝𝑝′𝑖𝑖𝑤𝑤𝑖𝑖
24 𝑖𝑖=1
𝑄𝑄𝑖𝑖+ � 𝑝𝑝𝑝𝑝′′𝑗𝑗𝑤𝑤𝑗𝑗𝑄𝑄𝑗𝑗
9 𝑗𝑗 =1
+ � 𝑃𝑃ft𝑘𝑘𝑤𝑤𝑘𝑘𝑄𝑄𝑘𝑘𝑑𝑑𝑘𝑘
14 𝑘𝑘=1
+� 𝑃𝑃app𝑟𝑟𝑤𝑤𝑟𝑟𝑄𝑄𝑟𝑟
2 𝑟𝑟=1
𝜃𝜃1,𝑟𝑟 1
+ � 𝑃𝑃𝑚𝑚𝑤𝑤𝑚𝑚𝑄𝑄𝑚𝑚
4 𝑚𝑚=1
𝜃𝜃𝑚𝑚𝑓𝑓𝑑𝑑𝑚𝑚 2
contamination; Ph is the proportion of preventive or monitoring costs Ch that are associated with item h (i.e. if a measure is adopted for multiple reasons, what is the contribution of the salmonella control program to the decision to adopt the measure and thus to the costs); i, j, k and r are indices representing feed material, feed (j, k) or animal types, respectively, where measures associated with the treatment of salmonella-contaminated materials, animals, or humans; pt’’I, pt’’j, Pftk, Pappr and Pm represent is the probability of salmonella contamination or prevalence of salmonella contamination occurring in i, j, k, r or m; w‘s are the cost caused by salmonella contamination, or eradication of the pathogen, in i, j, r, k or m; dk is the proportion of true infections that will be detected; dmis the proportion of each type of human infection; θ is the proportion of infections related to contamination in feed; and Q’s represent the quantity of pig feed materials, pig feed, pigs or humans in the study population. The costs taken into account in each of the six elements in the sum is explained in sections below. (7.4.5, 7.5.1, 7.5.2, 7.5.3, 7.5.4, 7.6).
For feed materials at import and storage prior to feed manufacturing, pa’i is the apparent prevalence of salmonella in feed material batches of 25 tons (see appendix 3). For costs incurred at industrial feed manufacturing stage, the apparent prevalence of salmonella in manufactured compound or complete feed (pa’’j) was used. Salmonella contamination in pigs at the farm was obtained as the probability for infection due to feed, using feeding type specific infection probabilities (Pftk).
As this was true prevalence, only proportion dk was considered to result in costly eradication measures. The incidence of salmonella at slaughter pigs was assigned with the observed prevalence of infections (Papp) represented by the prevalence in the lymph node samples (see appendix 3) and the costs for infection (wr) were relative to the number of pigs that were assumed to be influenced in the batch when a salmonella positive pig was detected. Finally, the annual prevalence of salmonella infections in humans Pm was determined as a proportion of observed infections that could be, according to the source attribution model, be linked to pig feeds. PmwmQmθ fdm therefore represents the product of the prevalence in humans, size of the population in Finland, reporting factor f = 11.5, proportion of infections associated with contamination in feed, and the proportion of infections associated with each type of human infection and cost wm per infected person (see section 7.6)
Parameters in the loss equation above are important in the cost-benefit analysis.
This is because feed is manufactured and handled for different types of animals by using partially the same facilities and resources. Therefore, it is essential to allocate the costs of monitoring and preventive measures to pig feed and other feeds.
Furthermore, it is essential to allocate the costs associated with pig feed to those caused by salmonella control (i.e. parameter Pi) and to those caused by other reasons than salmonella control. In addition, in the pig sector, it is essential to identify the number of salmonella infections that need to be resolved.
Preventive and monitoring costs Ci are independent of how much salmonella occurs in the food chain. These costs include the statutory measures and additional voluntary measures taken by the stakeholders, who include feed importers, feed processors, and manufacturers (small and large scale), mobile feed mixers, or pigs farms. These costs are explained in more detail in section 7.4 and include:
■ Costs of additional cleaning carried out at the harbor warehouse, at the feed factory or warehouse, for equipment and machinery, or at the pig farms
■ Sampling and analysis of salmonella samples taken from feed, feed ingredients, or from the environment where feed has been
■ Additional storage costs caused by waiting for the analysis results
■ Heat or acid treatments carried out to reduce the concentration of salmonella in feeds
■ Control of pests and vermin
■ Costs due to public monitoring and inspections
■ Other costs, if any
This approach was used because commercial feed production operators, in particular, purchase feed materials and produce feed for many types of animals. Monitoring costs related to the production of feed are accounted whereas monitoring costs related to production of feed materials without producing feed are accounted only to the extent that these activities are conducted by feed production operators. Hence, measures that prevent salmonella contamination are also often taken so that they cover feed for different animals. As information on the measures was obtained from a survey that covered multiple species, the cost share attributed to pig feed had to be divided among all produced feed.
By contrast, treatment and eradication costs (w’s) depend on the number and severity of salmonella contaminations and human infections observed. These costs include the statutory measures and additional voluntary measures taken by feed importers, feed processors, and manufacturers (small and large scale), mobile feed mixers, pigs farms, slaughterhouses, or measures taken to treat infected humans:
■ Additional samples taken to verify salmonella contamination and thereafter freedom from salmonella
■ Washing, cleaning, and disinfecting of facilities contaminated with salmonella
■ Treatment of salmonella-contaminated feed
■ Treatment or culling and rendering of salmonella-contaminated animals
■ Business interruptions caused by restrictive measures
■ Loss of efficiency on an infected farm
■ Labor effort by authorities and stakeholders in handling salmonella contamination
■ Costs caused by salmonella infections in humans (lost working time, visits to the doctor, hospitalization, mortality, sequelae of infection)
More details regarding the parameter values are provided in the sections 7.5 and 7.6.
The cost parameters (w’s) for feed and feed materials are normalized so that they represent the cost of measures related to 25 tons batch of feed or feed material that is positive with salmonella. For animals they are normalized per infected pig held on a salmonella-contaminated farm and for human infections they represent costs per infected human. Furthermore, w’s are multiplied by the amount of animals that can be considered to be influenced by 25 tons of salmonella positive feed, representative number of pig farms in Finland, and the population of Finland.
Because the net treatment and eradication costs can vary substantially from year to year due to changes in prevalence, they are simulated by using the Monte Carlo method. Prevalence parameters are based on the simulation results explained in the previous sections of this report. For the current monitoring programme, the parameters are obtained from the results of simulations reported in Table 12 and in appendix.