Eviran tutkimuksia - Evira research reports
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(Evira, 2018)Eviran tutkimuksia ; 2/2018Lisäaineet ovat aineita, jotka EU on hyväksynyt käytettäväksi elintarvikkeissa mm. säilyvyyden parantamiseksi tai rakenteen, maun tai värin säätämiseksi. Osa niistä on elintarvikkeissa luonnostaan esiintyviä yhdisteitä, osa keinotekoisia. Kullekin lisäaineelle on käyttöhyväksynnän yhteydessä määritetty puhtausaste, muita laatutekijöitä sekä tehty toksikologisia tutkimuksia, jotka voivat johtaa jopa käytön kieltämiseen. Tämä riskiprofiili pyrkii kartoittamaan kuluttajien lisäainealtistuksen perustasoa kansallisen seurantajärjestelmän pohjaksi. Siinä tutkitaan kaikkia niitä lisäaineita, joille on olemassa EFSA:n määrittämä hyväksyttävän päiväsaannin enimmäismäärä (ADI). Kuluttajien altistumista arvioitiin karkeasti lisäaineasetuksessa sallittujen suurimpien käyttömäärien pohjalta. Populaatiotason arviota tarkennettiin tarvittaessa teollisuuden ilmoittamilla käyttömäärillä. Karkean altistusarvion perusteella lisäaineet jaoteltiin kahteen ryhmään: aineet, joiden saanti Suomessa on varovaisestikin arvioiden turvallisella tasolla; ja aineet joiden saantia on tarpeen tutkia tarkemmin. Jälkimmäiseen ryhmään valikoitui joitakin väri-, säilöntä- ja makeutusaineita, fosfaatteja sekä tiedon puutteiden vuoksi joitakin elintarvikkeen rakennetta muokkaavia aineita.
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(Evira, 2018)Eviran tutkimuksia ; 1/2018Flavourings are products that are not intended to be consumed as such, but which are added to food in order to modify the odour or taste. Presently, about 2,500 chemically defined flavouring substances have been authorised in the EU. In addition to these, the EU regulation on flavourings includes flavouring preparations, thermal process flavourings, smoke flavourings, flavour precursors and other flavourings or mixtures. This report describes the main points on the legislation, evaluation, approval and safety of use of flavourings. The risk posed by flavouring substances is generally considered low because the amounts of flavouring substances used are usually low and many flavouring substances are simple compounds with known metabolites. Many flavouring substances are natural compounds and they are present, for instance, in traditional food. However, some natural flavourings may have adverse effects on human health. The intake of some flavourings may be high among brandloyal consumers or high users. Estimating the intake of flavourings is difficult because the methods used for intake estimates include large uncertainties and because information on the occurrence and concentrations of flavourings in food is scarce.
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(Evira, 2018)Evira Research Reports ; 3/2018Food items of animal origin, such as pork products, have been suggested as the main source of zoonotic salmonella infections in Europe. Contaminated feed can potentially introduce the pathogen into the animal-derived food chains. The prevalence of salmonella in different feeds for Finnish pigs was estimated as below 2% (medians) and on average in pigs 0.25% (mean). Feed was estimated on average as the cause of 35% of salmonella infections in fattening pigs and 55% in sows. Around 5% of the 300–400 domestic human salmonella infections reported per year were estimated as attributable to pig feeds. Year 2013 was employed as a reference. The present costs for the prevention of salmonella contamination in pig feeds were estimated at 1.8–3.0 million euros per year for the year 2013. The costs due to feed contamination, measures due to detected contamination and the resulting salmonella infections in pigs and humans were estimated at €2.4 (0.3–6.1) million annually. According to a scenario, if salmonella prevalence in Finnish pig feed would be similar to that acquired using data from other EU counties, the prevalence in fattening pigs and people could increase by 55-fold on average. If specific measures to eliminate salmonella from feed were not carried out, the costs due to preventive actions against salmonella were at least €1.1–1.8 million per year. Additionally, the costs due to the eradication of feedborne salmonella on pig farms, consequential measures at slaughterhouses, and the health costs to humans could rise to approximately €33 million per year. According to the results, the present feed salmonella control, including the preventive
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(Evira, 2016)Evira Research Reports ; 1/2016Dutch elm disease (DED) is a fungal disease that causes high mortality of elms. DED and its vector beetles are widely present in most of the countries in the Northern Hemisphere, but they are not known to be present in Finland. DED is a major risk to plant health in Finland. DED and its vectors are moderately likely to enter Finland by natural spread aided by hitchhiking, because they are present in areas close to Finland. Entry via other pathways is much less likely, mainly due to the low volume of trade of untreated wood and plants for planting. DED and its vectors could likely establish in the southern parts of the country, since they currently occur in similar climatic conditions in other countries. DED could cause massive environmental damage as natural elm groves are critically endangered habitats in Finland. The economic consequences to the owners of mature elms could also be significant. Eradication or containment of DED could be possible if strict measures were taken as the patchy distribution of elms would limit the spread of the disease. The most important source of uncertainty in this assessment is the lack of information regarding the amount of elm in fuel wood, wood waste and wood chips imported to Finland.
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(Evira, 2016)Evira’s Research Reports ; 2/2016Campylobacter spp. are among the most common causes of gastrointestinal diseases in EU countries. Between four and five thousand human campylobacteriosis cases are registered each year in Finland, of which the majority are most probably acquired from abroad. The prevalence and concentration of campylobacters in foods are influenced by the whole production chain. Based on retail samples, the average annual prevalence of Campylobacter spp. was estimated at 5.5–11.7% (95% CI) in Finnish chicken meat and 1.8–5.9% (95% CI) in turkey meat. No Campylobacter spp. were detected from either domestic beef or pork, and their prevalence was estimated to be 0.0–1.2% (95% CI). The mean concentration of Campylobacter spp. in contaminated poultry meat was estimated to be low, and the probability of illness per one serving was thus also relatively small. Even so, the assessment implies that thousands of human cases can occur due to meat consumption annually in Finland, with the biggest proportion related to chicken meat. However, the predicted number of cases is affected by many factors with uncertainty, such as the level of cross-contamination, size of serving and total consumption. For a general overview, other campylobacters sources should also be identified and their impact on campylobacteriosis quantified.
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(Evira, 2015)Evira Research Reports ; 4/2015Import of animal by-products (ABP) category 2 may cause health risks for cattle, pigs, sheep, goats and fish farms. ABP may, depending on their origin, contain pathogens causing problems for production animals. Therefore ABPs must be treated before use so as not to cause danger. ABPs are imported to Finland mainly for use in feed for fur animals and in fertilisers. In 2013 approximately 4.6 million kg of ABP category 2 were imported to Finland. The risk of pathogen introduction with ABPs is highest during summer and fall when fur animal feed consumption peaks resulting in a peak in ABP imports. The import, treatment and use of ABPs in Finland are investigated in the report. ABPs may contain pathogens if the treatment is inefficient, fails or recontamination occurs after treatment. No untreated ABPs were imported to Finland during the study period. Information about treatment facilities and treatment abroad is unavailable. In treatment plants in Finland some deficiencies have been observed. Direct contact between ABPs and production animals is most likely on farms with both fur and food producing animals. In Finland there are only 30 such farms. However, indirect contact is also possible through vector animals, fomites, water and wind.
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(Evira, 2015)Evira Research Reports ; 3/2015The structure of Finnish agricultural production has changed rapidly resulting in an increase in the average farm size and a reduction in the number of farms. Three animal diseases were used to illustrate the impacts of changing production structures and their consequences on the spread and control of disease: Foot-and-mouth disease (FMD), African Swine Fever (ASF) and Bluetongue (BT). The aim of this study was to assess how changes in the structure of animal production impact on animal disease risks and the economic consequences of diseases. The spread of diseases was simulated according to three predicted future production structure scenarios for 2033 and compared with reference simulations applying the production structure of the year 2009. FMD had the highest spread potential as the probability of spread and magnitude of an epidemic outbreak were the largest. ASF and BT had clearly lower spread potential and also structural change will affect them less. Spread potential is strongly dependent on how logistics will develop in relation with farm size increase. Economic losses due to FMD were similar in 2009 and 2033 simulations. Losses caused by ASF were smaller than those by FMD. In both cases distortions in the food exports were the main source of losses. Losses associated with BT were estimated to be smaller in the future.
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(Evira, 2015)The objective of this study was to determine whether the benefits of eating Baltic Sea herring exceed the risks in Finland, and what the situation is in different age groups. Previous risk-benefit analyses have shown that eating fish is in general healthier than not eating fish. This is particularly due to the healthy omega 3 fatty acids of fish. However, the benefits are largely enjoyed by adults with an elevated risk of heart disease, while children suffer the majority of the risks in the form of dental problems and other developmental disorders. In the riskbenefit analysis carried out to the order of Evira in collaboration with THL during 2014, different age groups were specifically considered separately in the light of current fish consumption. The results are based on the survey of the consumption of Baltic herring conducted by Taloustutkimus in 2013, which was used as the basis for the actual analysis of health effects. The results were expressed as Disability Adjusted Life Years (DALY). Omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) as well as vitamin D were analysed in the report as beneficial nutrients. As far as environmental toxins harmful to health are concerned, Baltic herring were analysed for compounds classified as dioxins, which include polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, as well dioxin-like biphenyls (PCB). According to the results, in Finland eating herring causes ca. 11 (95% confidence interval, CI 0-54) Disability Adjusted Life Years (DALYs) resulting from developmental disorders (dental damage); these affect children via the mother during pregnancy and breastfeeding. In addition, eating herring causes a ca. 12 (95%, CI 1,7-56) DALY cancer risk due to dioxins in the entire population. The health benefits of eating herring clearly exceed risks to health for women and particularly men after the age of 50 years. The greatest health benefits result from the reduction in heart disease and heart-related fatality, ca. –688 (95%, CI -2126 -41) DALY/year. The results show that the consumption of Baltic herring has decreased in Finland to a low level and that the current common dietary advices on fish consumption are adequate to protect the population against the adverse health effects of dioxins and dioxin-like compounds. However, in risk benefit analysis in future it is important to estimate the total health effects of different environmental pollutants and of other fatty fish, and the sufficiency of dietary advices on fish consumption.
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(Evira, 2014)Eviran tutkimuksia ; 1/2014This report compiles basic information needed when assessing the pest risk related to different plant species and sectors of plant production, namely information on a) the volume of pathways of entry and b) the value at risk in the sectors of plant production. The report covers all the products that can act as pathways for pest entry into Finland as comprehensively as possible. Also, the volume of traffic into Finland is reported. The amount of goods traded into Finland was estimated mainly based on official statistics. The value of plant production was assessed based on the volume of production and producer prices. The total amount of the goods traded into Finland was estimated to be about 12 billion kg yearly, of which about 92% were wood and wood products, 7% food and raw materials for the food industry, and about 0.2% propagation material. The total amount of propagation material traded into Finland was about 2 900 billion seeds and/or plants for planting per year. The report covers the trade in about 130 plant species or families. The value of plant production was estimated to be in total about 3.5 billion euros per year. Of this, forestry covers about 54%, field crops about 31% and horticultural production about 11%.
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(Evira, 2014)Eviran tutkimuksia ; 2/2014The main difference between organic and conventional turkey production from an animal disease hazard and biosecurity standpoint, is the outdoor requirement in organic production. Biosecurity barriers between the production facilities and the environment cannot be implemented as strictly as in conventional production facilities. Organic turkeys are therefore more susceptible to disease agents spread by wild birds and rodents as well as soil-borne agents. Infectious agents influence the health of the turkeys and can affect consumers through the consumption of turkey meat. Production of pastured turkeys offers an intermediate form between organic and conventional production. Risk management options such as pest control, pasture rotation and vaccination against erysipelas can limit the animal disease risks associated with pasturing. Risk management naturally involves added costs for the producer. However, its share is small in relation to other variable costs of organic production. Other animal disease risk factors in organic turkey production are associated with housing, feeding and animal stock. Pasturing also involves many positive effects such as increased exercise, lower animal density and better air quality. Disease risks can be decreased with good planning and the use of risk management tools.
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(Evira, 2011)Evira Research Reports ; 1/2011Foot-and-mouth disease (FMD) is a highly contagious viral epizootic disease of cloven-footed animals, which is controlled both by domestic and EU legislation. FMD has not been found in Finland since 1959. The aim of this risk assessment was, by using Monte Carlo simulations, to assess how FMD would spread, the economic consequences of an outbreak and the feasibility of emergency vaccination in case of an outbreak in Finland. The study was based on data from the Finnish cattle and swine production sectors from 2006. If FMD was introduced to a Finnish pig or cattle farm, it would in most cases spread to four other farms and the disease would be brought under control after 5 weeks. In one-third of the cases, the disease would remain a sporadic case and would not spread at all from the first infected farm. Even a larger outbreak would remain relatively small and short. In the worst case scenario, FMD virus would spread to 29 farms before the disease was eradicated. The mean economic consequences of a sporadic outbreak would be €23 million. In the worst case scenario, the economic losses would be more than €38 million. Emergency vaccination is not a feasible option according to this study, because the current EU measures are able to stop the spread of disease and because vaccination can incur considerable extra costs due to prolonged export distortions.
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(Evira, 2011)Eviran tutkimuksia ; 2/2011As an outcome of the EU FISH II project, information was produced about PCDD/F and PCB as well as PBDE levels in Baltic fish, domestic freshwater fish and farmed fish. Variations in the levels were studied by age and size of the fish as well as by species and areas. Analyses of the presence of perfluorinated compounds (PFC) and organotin compounds (OT) in muscles and liver were also carried out within the scope of the project. New data on the content of hazardous substances in fish were obtained for use in risk management. The 2009 results were compared with the results of the previous project conducted in 2002-2003. Analyses of PCDD/F and PCB levels in fish highlight the same species that have also previously been found to be susceptible to accumulation of these environmental toxins. Baltic herring, salmon and sea trout as well as river lamprey and now in this study also European flounder in Kotka area show levels of PCDD/F and PCB compounds exceeding the maximum stipulated limits. In Baltic fish, the median levels of dioxin equivalents in sprat, vendace, perch, pike, pike-perch, burbot and cod are not even half of the permitted maximum level, which is 4 pg/g of fresh weight. The comparison of the levels measured in 2002-2003 with the 2009 levels of PCDD/F and PCB as well as PBDE compounds shows that the mean levels have decreased in salmon and herring. The OT levels measured in the muscles of open sea fish were about one third lower than in the fish samples caught in 2005–2007. Dioxins and dioxin-like PCB compounds are still the worst contaminants in the Baltic Sea. The levels of PBDE, PFOS and OT were low, with a few exceptions. The Bothnian Sea and the fishing areas of Pori, Turku and Kotka took the lead in the contamination ranking, but the worst area was Vanhankaupunginlahti Bay of Helsinki, where both OT and PFOS levels give cause to recommend consumption restrictions, at least as far as large perch are concerned.
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(Evira, 2012)Eviran tutkimuksia ; 4/2012This report identifies and describes possible biological risks posed to consumers by raw cow and goat milk produced in Finland. It also describes methods of reducing such risks. Raw milk consumption has so far been scarce in Finland (about 1% of all milk and dairy product consumption), but some of its consumers belong to risk groups. The risk to consumers is increased by the long storage times and high storage temperatures of raw milk in some home kitchens. According to this investigation, the most important biological factors posing food safety risks in raw milk are EHEC, Listeria monocytogenes, salmonella and campylobacteria. These may cause serious diseases and sequelae. All of them have been found in Finnish production animals, people and barn environments. The Finnish food safety system is not well adapted to providing for the special characteristics of raw milk production and consumption. Instead, risk management is largely based on good hygiene practices and pasteurisation, in order to destroy the microbes in milk. For these reasons, creating a consistent national system would be advisable, proportioned to raw milk sales volumes and activities, in order to prevent possible risks and to distribute information to companies and consumers handling raw milk, on good production practices and safe use.
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(Evira, 2012)Eviran tutkimuksia ; 1/2012In Finland there is statutory surveillance of several swine diseases. We have studied the representativeness of the control programs for AD, TGE and PRRS. These diseases are not at the moment present in Finland and moreover Finland has additional guaranties in the EU for AD and TGE. The control programs are based approximately on 1000 yearly blood samples that are taken from sows in the slaughterhouses. Surveillance of the studied diseases in Finland has been implemented as planned during the studied years 2008-2009. The results reveal that the control programs are most sensitive to detect PRRS and least sensitive to detect TGE. One year of surveillance is enough to demonstrate that the diseases have not been endemic in Finland, but it is not enough to prove freedom from disease. To be able to more effectively prove freedom from disease it is necessary to combine the results from the control program with passive surveillance and take into consideration the risk of entry of the diseases into the country.
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(Evira, 2011)Eviran tutkimuksia ; 4/2011The African swine fever is a viral disease that spreads easily to domestic pigs and wild boar and has considerable socioeconomic consequences as well. Statutory measures are required to combat African swine fever. In the acute phase of the disease pigs can show symptoms including high fever, haemorrhages in the skin, anorexia, blood in stool and possibly diarrhea. Mortality rates can reach almost 100 per cent, and death appears within 7-10 days from infection. The disease is not spread to humans. The disease occurs as well as in domestic pigs as in wild boar in the largest part of sub-Saharan Africa and in Sardinia. Since 2007 the disease has occurred in the Caucasus region and in 2011 near the border of Finland: the Leningrad region and the Kola Peninsula. In the risk profile different routes and chains of events which could lead to the African swine fever entering Finland for the first time are identified and described. The most obvious ones are: people who have travelled in the infected area, infected meat or meat products, with domestic pigs and sperm, contaminated transport vehicles, catering waste from international transport and infected wild boars crossing the border to Finland. The key measures to protect the Finnish swine industry from the African swine fever are high biosecurity of farms and effective and aimed information on the risks of the disease.
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(2011)Eviran tutkimuksia ; 3/2010Plant production products are used to prevent plant diseases, to restrict harmful organisms, and to regulate growth. The consumer risks of active substances are evaluated considering one substance at a time, which gives crucial information, but as such cannot give an overall picture of dietary exposure. The probability of dietary exposure was estimated by cumulative simulation methods. For the first time in Finland exposure estimation in acute setting and also among sensitive groups, such as young children, has been carried out. The cumulative risk assessment presented herein is based on research results gained in control of pesticides residues from a total of 10 565 foodstuff samples. Moreover, risk assessment has utilised data on food consumption of adults and children, produced by the National Institute for Health and Welfare and the DIPP Consortium (the National FINDIET 2007 Survey and DIPP Nutrition Studies). Dietary exposure to residues of plant protection products is characterized by a low chronic exposure level, on which higher acute exposure occasionally takes place. While chronic exposure to pesticide residues did not raise any concerns, the situation in acute exposure setting cannot be considered equally good. Carbamates and organophosphates resulted in aRfD exceedances among children and adults with a probability higher than 0,01%. While the probability of an aRfD exceedance in adult group in the past few years has decreased to acceptable levels, among three-year old children it has not. Although the most important underlying carbamates and organophosphates are not used in Finland any more, current situation does not in all respects fulfil the goals set for the level of protection. Therefore monitoring of sensitive subpopulations should be continued.
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(2011)Evira Research Reports ; 2/2010The reported incidence of human campylobacteriosis in Finland is higher than in most other European countries. A high annual percentage of sporadic infections is of foreign origin, although a notable proportion of summer infections is domestically acquired. While chickens appear to be a major source of campylobacters for humans in most countries, the prevalence of campylobacters is very low in chicken slaughter batches in Finland. Data on other potential animal reservoirs of human pathogenic campylobacters in Finland are scarce. Consequently, this study aimed to investigate the status of Finnish cattle as a potential source of thermophilic Campylobacter spp. and antibiotic-resistant Campylobacter jejuni for human sporadic campylobacter infections of domestic origin. A survey of the prevalence of thermophilic Campylobacter spp. in Finnish cattle studied bovine rectal faecal samples (n=952) and carcass surface samples (n=948) from twelve Finnish slaughterhouses from January to December 2003. The total prevalence of Campylobacter spp. in faecal samples was 31.1%, and in carcass samples 3.5%. Campylobacter jejuni, the most common species, was present in 19.5% of faecal samples and in 3.1% of carcasses. In addition to thermophilic Campylobacter spp., C. hyointestinalis ssp. hyointestinalis was present in bovine samples. The prevalence of campylobacters was higher among beef cattle than among dairy cattle. Using the enrichment method, the number of positive faecal samples was 7.5 times higher than that obtained by direct plating. The predominant serotypes of faecal C. jejuni, determined by serotyping with a set of 25 commercial antisera for heat-stable antigens (Penner), were Pen2 and Pen4-complex, which covered 52% of the samples. Genotyping with pulsed-field gel electrophoresis (PFGE) using SmaI restriction yielded a high diversity of C. jejuni subtypes in cattle. Determining the minimum inhibitory concentrations of ampicillin, enrofloxacin, erythromycin, gentamicin, nalidixic acid, and oxytetracycline among bovine C. jejuni isolates using a commercial broth microdilution method yielded 9% of isolates resistant to at least one of the antimicrobials examined. No multiresistant isolates were found among the bovine C. jejuni strains. The study of the shedding patterns of Campylobacter spp. among three Finnish dairy cattle herds included the examination of fresh faecal samples and tank milk samples taken five times, as well as samples from drinking troughs taken once during the one-year study. The semiquantitative enrichment method detected C. jejuni in 169 of the 340 faecal samples, mostly at low levels. In addition, C. jejuni was present in one drinking trough sample. The prevalence between herds and sampling occasions varied widely. PFGE, using SmaI as restriction enzyme, identified only a few subtypes in each herd. In two of the herds, two subtypes persisted throughout the sampling. Individual animals presented various shedding patterns during the study. Comparison of C. jejuni isolates from humans, chickens and cattle included the design of primers for four new genetic markers selected from completely sequenced C. jejuni genomes 81-176, RM1221 and NCTC 11168, and the PCR examination of domestic human isolates from southern Finland in 1996, 2002 and 2003 (n=309), chicken isolates from 2003, 2006 and 2007 (n=205), and bovine isolates from 2003 (n=131). The results revealed that bovine isolates differed significantly from human and chicken isolates. In particular, the γ-glutamyl transpeptidase gene was uncommon among bovine isolates. The PFGE genotyping of C. jejuni isolates, using SmaI and KpnI restriction enzymes, included a geographically representative collection of isolates from domestic sporadic human infections, chicken slaughter batches, and cattle faeces and carcasses during the seasonal peak of campylobacteriosis in the summer of 2003. The study determined that 55.4% of human isolates were indistinguishable from those of chickens and cattle. Temporal association between isolates from humans and chickens was possible in 31.4% of human infections. Approximately 19% of the human infections may have been associated with cattle. However, isolates from bovine carcasses and human cases represented different PFGE subtypes. In conclusion, this study suggests that Finnish cattle is a notable reservoir of C. jejuni, the most important Campylobacter sp. in human enteric infections. Although the concentration of these organisms in bovine faeces appeared to be low, excretion can be persistent. The genetic diversity and presence or absence of marker genes support previous suggestions of host-adapted C. jejuni strains, and may indicate variations in virulence between strains from different hosts. In addition to chickens, Finnish cattle appeared to be an important reservoir and possible source of C. jejuni in domestic sporadic human infections. However, sources of campylobacters may differ between rural and urban areas in Finland, and in general, the transmission of C. jejuni of bovine origin probably occurs via other routes than food.
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(Evira, 2009)Eviran tutkimuksia ; 3/2009Bluetongue (BT) is a vector-borne viral disease of ruminants, which is classified in Finland as an easily spreading disease which has to be controlled. The symptoms of the disease are non-specific, and are for example fever, erosions on the mucous membrane of the mouth, difficulties in swallowing, swellings in the head and lameness. Bluetongue has never been found in Finland. In the last few years, Bluetongue outbreaks have been detected further north than previously. The outbreaks closest to Finland have been in Sweden and Norway. In this risk profile we study the risk factors related to BT coming to Finland and spreading further and what the consequences would be if the disease should spread. In the study, the Finnish climate and the specific features of the animal population have been taken into account. In addition, the possible consequences of the disease and under what conditions the disease could remain endemic in Finland have been investigated. In Finland there are at least four species of the Culicoides family which have been connected with the BT virus abroad. According to the statistics of the Finnish Meteorological Institute for the last ten years, the temperatures have been high enough for long enough in order to make it possible for the Culicoides biting midges and the BT virus to increase and to spread throughout the whole country. The climatic conditions however, are more favourable to the disease on Åland and in Southern and Western Finland.
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(Evira, 2007)Evira Research Reports ; 3/2007Pigs coexist with diverse and dense commensal microbiota in their gastrointestinal tract (GIT). Lactobacilli, identified as common members of porcine intestinal microbiota, have been considered to be an important group of bacteria in maintaining the stability of GIT, in preventing intestinal infections and generally, in supporting intestinal health. Because several species of lactobacilli have GRAS (generally regarded as safe) status and some of them have an ability to interact with intestinal epithelial cells, thus promoting host-bacterial interactions, their possible applications as mucosal vaccine vector and/or probiotics have aroused interest. Selection criteria for lactobacilli to be used as vaccine vector or probiotic include the abilities to adhere to the intestinal epithelium cells and colonize the lumen of the GI tract. The adherence to host tissues, which enables the organism to overcome local defences such as mucociliary function and peristaltis, is usually mediated by specialized proteins called adhesins. These adhesins are responsible for recognizing and binding to specific receptor structures of the host cells. Bacterial adhesins are often found in hair-like appendages called pili or fimbriae that extend outward from bacterial surface. Alternatively, they can be directly associated with the microbial cell surface. Surface layer proteins (Slps) of lactobacilli have been shown to confer tissue adherence. In this study, S-layer positive lactobacilli from the intestine and faeces of pigs were isolated and their ability to adhere to pig and human intestinal cells as well as to extracellular matrix (ECM) components, collagen, laminin and fibronectin were studied. The adherence of S-layer carrying lactobacilli varied from strong to moderate for human and porcine small intestine enterocytes and for the components of ECM and basal membranes (BM). Removal of the intact Slps reduced the adhesion of some strains to fibronectin and laminin, whereas, the adhesiveness to laminin increased with some strains. Besides the putative binding properties of Slps, a very large number of surface layer protein subunits present in an S-layer make the use of the S-layer structure a very 7 interesting alternative to surface display antigens. Therefore, the aim of this study was to characterize the S-layer proteins. Two new surface layer proteins (SlpB and SlpD), with potential to be tested as antigen carriers, were characterized, and three S-layer protein (slpB, slpC and slpD) genes were isolated, sequenced, and studied for their expression in Lactobacillus brevis neotype strain ATCC 14869. Under different growth conditions, L. brevis strain was found to form two colony types, smooth (S) and rough (R), and to express the S-proteins differently by mechanism not involving DNA rearrangements. The adhesion studies indicate that L. brevis adheres to human and pig intestinal epithelial cells but it is not currently known whether the binding is mediated by the surface proteins in this L. brevis strain of human origin. To identify the S-layer positive lactobacilli strains used in this study, a polyphasic taxonomic approach was applied. The methods used included 16S rRNA gene sequence analysis, numerical analysis of 16 and 23 rRNA gene ribotypes and DNA-DNA reassociation. In addition, all strains were included in a multilocus sequence analysis (MLSA) study for species identification using housekeeping genes encoding the phenylalanyl-tRNA synthase alpha subunit (pheS) and RNA polymerase alpha subunit (rpoA). These results indicated that six out of eight porcine lactobacilli strains from Finland and the related L. sobrius strains, originating from porcine intestine from elsewhere, constitute a single species, L. amylovorus, and that the name L. sobrius should be considered as a later synonym of L. amylovorus. In the final part of this study, the adhesin FedF of Eschrichia coli F18 fimbriae was characterized. The work aims at developing lactobacilli as a live mucosal vaccine vector for pigs against diseases caused by F18+ E. coli. The F18 fimbriae carrying E. coli strains colonize the microvilli of porcine small intestinal epithelial cells and cause post-weaning diarrhoea (PWD) and edema disease (ED) in pigs. It has been shown that oral immunization of weaned piglets with adhesins can induce a protective mucosal immune response. Naked FedF appeared to be very unstable but in our study it could be produced as a fusion protein with maltose binding protein (MBP). Specific adhesion to isolated porcine intestinal epithelial cells was demonstrated with MBP-FedF fusions as well as the ability of anti-MBP-FedF antibodies to prevent binding of E. coli F18 to porcine epithelial cells.
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(Evira, 2008)Evira Research Reports ; 4/2008The drive for risk-based food safety management, systems and control has spread world-wide in recent decades. Since the term is still internationally undefined, its use and implementation vary, producing different realizations. In this Ph.D. thesis, microbiological risk assessment (MRA) was investigated as a basis for risk-based food safety management, which was defined as ‘food safety management based on risk assessment in order to achieve an appropriate level of protection (ALOP)’. Governments are responsible for commissioning MRAs and also for setting food safety targets up to a certain point, but the practical management measures that need to be in place in order to achieve the targets are to be addressed by the operators. On the plant level, food safety is usually managed through regulation, quality assurance systems and a hazard analysis and critical control point (HACCP) programme with its prerequisites. In Finland, food safety management on the food plant level is implemented through an HACCP-like regulated system termed an ownchecking (OC) programme. A quantitative microbiological risk assessment (QMRA) was conducted on salmonella in the beef production chain according to the official standards of the Codex Alimentarius Commission (Codex Alimentarius), and utilized in determining the food safety metrics for beef production. The Finnish Salmonella Control Programme (FSCP) and the main official interventions due to it were examined in the light of risk-based food safety management. The targets set for beef processing plants by the government were converted into quantitative limits, and the results of salmonella monitoring included in the FSCP were examined by the QMRA. The goal of the FSCP was declared in 1994 to ‘maintain the present salmonella situation’, which was considered to refer to the salmonella incidence in humans at that time, and also the de facto ALOP. The requirement for a maximum salmonella prevalence of 1% at defined stages of the beef production chain was embodied in the FSCP. This statement was considered to convey performance objectives (PO) for the aforementioned stages. According to the QMRA, the de facto ALOP was achieved in the referred year 1999, and even the true prevalence levels in the FSCP were estimated to be clearly under the set PO limits with 95% credibility. However, the PO limits were set too high for the de facto ALOP to be maintained in practice. If the salmonella prevalence reached the PO limit of 1% or values near it, the public health risk would increase and overrun the de facto ALOP. The QMRA produced in this work has for the first time provided the possibility to quantitatively asses the relationships between targets set in the FSCP and their impact on public health. At present, imports of beef and beef-derived foods may impose on Finnish consumers a significantly greater exposure than domestic products. If their salmonella prevalence or their share of the foods consumed in Finland increase, the number of human cases could rapidly rise. The models for the QMRA were mainly Bayesian hierarchical models using Markov chain Monte Carlo (MCMC) techniques, which was found to be a flexible and appropriate method for this type of complex modelling. The resulting distributions were also regarded as an advantage compared to the results from models developed with the deterministic approach, because the presentation of results included the extent of the uncertainty, and also in this manner better illustrated the actual operational environment. Based on an inquiry, the personnel in food processing plants had a positive attitude towards food safety management systems, but the knowledge, training and involvement of those employees directly operating on the site with these systems were discovered to be deficient. Therefore, a generic semi-quantitative hygiene risk assessment model, Hygram®, was developed for small and medium-sized food enterprises to offer assistance in understanding, training, and, first of all, detecting the critical steps of the processes, and thereby to contribute to the development of their own-checking systems towards risk-based food safety management. Hygram® was not considered a risk-based tool as such, but whenever the critical limits of the process have been defined as equal to a risk assessment, Hygram® can be used as a risk-based management tool. It can also serve as a tool for systematic hazard analysis and CCP detection when establishing a food safety management system. To conclude, the development of risk-based food safety management is a process in which risk assessment is an essential tool. Scientific, technical, psychological and resource-bound barriers need to be overcome in order to put risk-based management systems into practice. This study showed that QMRA can be valuable in national risk management decision making, although few QMRAs are currently available. Appropriate tools for practical risk management decision making on the industrial level, such as Hygram®, need to be further developed.
