Molecular characterization of endemic salmonella infections ... - Evira

2.4 Risk assessment and risk management of salmonella infections in cattle
Scientific risk assessments are important tools for estimating the magnitude of different risks and
the effects of different interventions to control these risks (Maijala and Ranta 2003). The nature of
the risk, the possible consequences, and their probability are evaluated in the risk assessment
process (National Veterinary and Food Research Institute 2005). It is based on four stages: hazard
identification, hazard characterization, exposure assessment, and risk characterization (Ranta et al
2004). The risk assessment begins with hazard identification, where the hazard (for example,
salmonella) is identified on a general level. The hazard identification can address questions such
as what kind of disease the Salmonella bacteria might cause, how the disease might spread, and
what is the incidence and prevalence of salmonella. The hazard characterization includes a more
detailed description of the hazard: the microbe itself, the symptoms it may cause, and how it
affects its hosts. Exposure assessment is calculated based on basic information on the exposure
to Salmonella. To be able to assess the risk of exposure, transmission models have to be made
(Maijala and Ranta 2003; Ranta et al 2004). Different exposure models, such as the Bayesian
Hierarchial Modeling (Ranta et al 2005), are used to assess the exposure or estimate the true
salmonella prevalence. A general estimate of the risk of infection is produced by combining
information derived from the exposure assessment with information about the dose-response. Risk
characterization can be done once the risk of infections caused by Salmonella has been quantified
using the exposure models (Maijala and Ranta 2003; Ranta et al 2004).
When risk management actions are evaluated, the true prevalence or incidence should be the
basis for evaluation. The Finnish Salmonella Control Programme (FSCP) was introduced in 1995,
when Finland joined the EU. The aim of the programme was to keep the domestic salmonella
prevalence below 1 per cent along the food chain in broiler, turkey, beef, pork, and egg production.
The FSCP for cattle is more like a monitoring system than a control programme. The regulations
concerning cattle and beef production begin with feed control. All imported, marketed, and
manufactured feed materials and compounded feeds are tested for Salmonella, and no batches
with Salmonella detection are approved. The bulls for artificial insemination and their herds of
origin are required to test negative for Salmonella. Likewise all suspected cattle (with clinical
symptoms or epidemiological evidence) are examined bacteriologically. The intention of this
sampling and testing of cattle is to limit the spread of Salmonella between farms and animals
(Tuominen et al 2007). If Salmonella is detected in cattle, the herd of origin is put under official
restrictions, including isolation of Salmonella-positive animals and the prohibition of animal
movements. Faecal samples from all the animals are examined at one month intervals. The
restrictions are lifted when two successive samplings are negative for Salmonella.
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