Public health aspects of microbial contaminants in food

Summary

Food‐borne diseases affect the health and welfare of hundred thousands of people and result in considerable economic loss. Salmonella and Campylobacter are by far the most important causes of food‐borne illness. Raw foods of animal origin are the major sources of these pathogens. Mishandling of foods in kitchens contributes to food‐borne disease outbreaks. More education is necessary. But because of the inevitable risk of recontamination of cooked foods in every kitchen, more emphasis should be placed on pathogen‐free raising of food animals and good manufacturing practices during slaughter. This will minimise contamination of raw foods of animal origin, thus reducing the contamination pressure in the kitchen and more effectively controlling food‐borne diseases.     

Future directions in the European union for veterinary education as related to food-producing animals, with special reference to Greece

During the past 50 years, procedures for raising food-producing animals have changed. Intensification of food production was necessary to keep prices low and to fulfill market demands for the continuously increasing worldwide population. Intensification of farming procedures produced many new problems, some of which had a considerable impact on public opinion about how animals are raised and how food of animal origin is produced and preserved. "Man made diseases" of animals such as bovine spongiform encephalopathy (BSE); contamination of foods with dioxins either through contamination of animal feeds or from the environment; and increased microbial resistance to drugs used for treatment, for prophylaxis of animals from infectious agents, and for growth promotion are some well-known hazards of intensified farming. Veterinarians working on food-producing animals are faced with an increased demand for foods of high quality and safety in developed countries, and higher quantities in the rest of the world. These qualitative and quantitative changes indicate that they must adjust to these new conditions. They will be most successful if their education is adjusted to meet the challenges that the public has created for them through new concepts of the production of food of animal origin. One such concept is the production of foods under fully certified procedures from the farm to the consumer's table. Food safety measures protecting public health will better be achieved if the education of the future veterinarian includes the principles of Hazard Analysis Critical Control Points (HACCP) starting at farm level. This article provides some market-driven ideas in this direction for European Union (EU) countries, including Greece.     

Bioterrorism: the role of veterinarians in detection and prevention

The fear of terrorist attacks has increased since the events of 11 September 2001 in New York. In the weeks following the terrorist attack, letters containing anthrax spores were received at various locations in the USA. This shows that bioterrorism is possible and that is necessary to be prepared for the potential release of biological agents. Such agents can be distributed not only via the air and drinking water but also via household pets. The aim of terrorist attacks, namely, the disruption of society and daily life, can be achieved in three ways, ways which are of importance to practising veterinarians, namely, via pets, via contamination of pet foods of animal origin, and by the spread of infectious animal diseases that have far-reaching economic consequences. These ways are discussed in this article, together with possible ways in which veterinarians can act to diminish the consequences of such an event.     

Emerging food-borne parasites

Parasitic food-borne diseases are generally underrecognised, however they are becoming more common. Globalization of the food supply, increased international travel, increase of the population of highly susceptible persons, change in culinary habits, but also improved diagnostic tools and communication are some factors associated with the increased diagnosis of food-borne parasitic diseases worldwide. This paper reviews the most important emerging food-borne parasites, with emphasis on transmission routes. In a first part, waterborne parasites transmitted by contaminated food such as Cyclospora cayetanensis, Cryptosporidium and Giardia are discussed. Also human fasciolosis, of which the importance has only been recognised in the last decades, with total numbers of reported cases increasing from less than 3000 to 17 million, is looked at. Furthermore, fasciolopsiosis, an intestinal trematode of humans and pigs belongs to the waterborne parasites as well. A few parasites that may be transmitted through faecal contamination of foods and that have received renewed attention, such as Toxoplasma gondii, or that are (re-)emerging, such as Trypanosoma cruzi and Echinococcus spp., are briefly reviewed. In a second part, meat-borne parasite infections are reviewed. Humans get infected by eating raw or undercooked meat infected with cyst stages of these parasites. Meat inspection is the principal method applied in the control of Taenia spp. and Trichinella spp. However, it is often not very sensitive, frequently not practised, and not done for T. gondii and Sarcocystis spp. Meat of reptiles, amphibians and fish can be infected with a variety of parasites, including trematodes (Opisthorchis spp., Clonorchis sinensis, minute intestinal flukes), cestodes (Diphyllobothrium spp., Spirometra), nematodes (Gnathostoma, spp., anisakine parasites), and pentastomids that can cause zoonotic infections in humans when consumed raw or not properly cooked. Another important zoonotic food-borne trematode is the lungfluke (Paragonimus spp.). Traditionally, these parasitic zoonoses are most common in Asia because of the particular food practices and the importance of aquaculture. However, some of these parasites may emerge in other continents through aquaculture and improved transportation and distribution systems. Because of inadequate systems for routine diagnosis and monitoring or reporting for many of the zoonotic parasites, the incidence of human disease and parasite occurrence in food is underestimated. Of particular concern in industrialised countries are the highly resistant waterborne protozoal infections as well as the increased travel and immigration, which increase the exposure to exotic diseases. The increased demand for animal proteins in developing countries will lead to an intensification of the production systems in which the risk of zoonotic infections needs to be assessed. Overall, there is an urgent need for better monitoring and control of food-borne parasites using new technologies.     

Anatomy of a recall

Pet foods on the market that are contaminated or otherwise present a health risk to humans or animals may be subject to a recall under US Food and Drug Administration (FDA) regulations. Legally, all recalls are "voluntary," but there is little incentive for companies to refuse a request by FDA to conduct a recall. While the firm does the bulk of the work, FDA oversees all aspects of a recall to help ensure that violative product is swiftly removed from the market. A recent new federal law will require FDA to improve its abilities to detect outbreaks of pet food-borne illness, respond to a contamination incident, and communicate with industry and the public on the matter of recalls. Veterinarians play a key role in detecting and reporting pet food-borne illness.     

Survey on the Listeria contamination of ready-to-eat food products and household environments in Vienna, Austria

Qualitative and quantitative contamination of ready-to-eat food-stuffs with the pathogen Listeria monocytogenes was studied in 1586 samples collected from 103 supermarkets (n = 946) and 61 households (n = 640) in Vienna, Austria. Seventeen groups of ready-to-eat foods were classified into three risk categories for contamination (CP1-CP3). Three to four samples were randomly collected at the retail level from each CP. Regarding the households, the sampling procedure was started with food items of CP1, and if not available, was continued with sampling of food items of CP2 and finally of CP3. Additionally, 184 environmental samples (swabs from the kitchen area, dust samples from the vacuum cleaner) and faecal samples (household members and pet animals) were included. One-hundred and twenty-four (13.1%) and 45 (4.8%) samples out of 946 food samples collected from food retailers tested positive for Listeria spp. and L. monocytogenes, respectively, with five smoked fish samples exceeding the tolerated limit of 100 CFU/g food. Food-stuffs associated with the highest risk of contamination were twice as frequently contaminated with L. monocytogenes as food-stuffs associated with a medium risk of contamination. Products showing the highest contamination rate were fish and seafood (19.4%), followed by raw meat sausages (6.3%), soft cheese (5.5%) and cooked meat products/patés (4.5%). The overall contamination rate of foods collected at the household level was more than two times lower. Only 5.6% and 1.7% of 640 food-stuffs analysed tested positive for Listeria spp. and L. monocytogenes, respectively. However, CP1 foods were rarely collected. Pulsed-field gel electrophoresis (PFGE) typing of the collected L. monocytogenes isolates revealed a high degree of diversity between the isolates, with some exceptions. PFGE typing of isolates harvested from green-veined cheese revealed a match among strains, although the manufacturer seemed to be distinguishable. Typing of household strains revealed an epidemiological link within one family. In this case, food-stuffs and the kitchen environment were contaminated by an indistinguishable isolate. In addition, the same isolate was collected from a pooled faecal sample of the household members suggesting that consumption of even low contaminated food items (<100 CFU/g) results in Listeria shedding after the passage through the gut.     

Veterinary public health: past success, new opportunities

Animal diseases are known to be the origin of many human diseases, and there are many examples from ancient civilizations of plagues that arose from animals, domesticated and wild. Records of attempts to control zoonoses are almost as old. The early focus on food-borne illness evolved into veterinary medicine's support of public health efforts. Key historical events, disease outbreaks, and individuals responsible for their control are reviewed and serve as a foundation for understanding the current and future efforts in veterinary public health. Animal medicine and veterinary public health have been intertwined since humans first began ministrations to their families and animals. In the United States, the veterinary medical profession has effectively eliminated those major problems of animal health that had serious public health ramifications. These lessons and experiences can serve as a model for other countries. Our past must also be a reminder that the battle for human and animal health is ongoing. New agents emerge to threaten human and animal populations. With knowledge of the past, coupled with new technologies and techniques, we must be vigilant and carry on.     

New food safety initiatives in the Food Safety and Inspection Service, U.S. Department of Agriculture

The production of meat and poultry products has become increasingly complex. Technological growth has contributed to the need for sophistication in determining the origin and risk of food-borne microbial infections as well as environmental contaminants. The increasing use of agricultural chemicals in animal production and to some extent in processed foods has led to the presence of chemical residues in meat and poultry. These changes have caused the Food Safety and Inspection Service (FSIS), a public health agency within the United States Department of Agriculture (USDA), to institute new food safety initiatives and procedures for inspection of meat and poultry products. The goal is to reduce risks to the public health from conditions observed during antemortem and postmortem inspection or detected during processing. FSIS is committed to scientific innovation and has implemented several rapid inplant tests that have given the Agency inexpensive, less disruptive methods to determine product adulteration contamination.     

Recent pre-harvest supplementation strategies to reduce carriage and shedding of zoonotic enteric bacterial pathogens in food animals

Food-borne bacterial illnesses strike more than 76 million North Americans each year. Many of these illnesses are caused by animal-derived foodstuffs. Slaughter and processing plants do an outstanding job in reducing bacterial contamination after slaughter and during further processing, yet food-borne illnesses still occur at an unacceptable frequency. Thus, it is imperative to widen the window of action against pathogenic bacteria. Attacking pathogens on the farm or in the feedlot will improve food safety all the way to the consumer's fork. Because of the potential improvement in overall food safety that pre-harvest intervention strategies can provide, a broad range of preslaughter intervention strategies are currently under investigation. Potential interventions include direct anti-pathogen strategies, competitive enhancement strategies and animal management strategies. Included in these strategies are competitive exclusion, probiotics, prebiotics, antibiotics, antibacterial proteins, vaccination, bacteriophage, diet, and water trough interventions. The parallel and simultaneous application of one or more preslaughter strategies has the potential to synergistically reduce the incidence of human food-borne illnesses by erecting multiple hurdles, thus preventing entry of pathogens into the food chain. This review emphasizes work with Escherichia coli O157:H7 to illustrate the various strategies.     

Emerging zoonoses

The food-borne zoonoses are the most important zoonoses in England and Wales measured in terms of human morbidity and mortality and they include the most important emerging infections. Over the past decade there were over 100,000 laboratory reported cases of salmonellosis, about 1–5 per cent with serious extra-intestinal complications with 427 registered deaths; there were nearly 90,000 Campylobacter infections. In salmonellosis the sources and modes of spread of infection are largely known, but veterinary and human public health measures have so far failed to control the disease. In Campylobacter enteritis however, the source and spread in most of the reported cases are unknown and control is not yet possible. Amongst the remaining less common food-borne zoonoses, listeriosis and yersiniosis are most prominent. Both are increasing with food-borne outbreaks of both infections having been reported, but the origin of infection of most cases recorded in England and Wales is not known. Of the new food-borne or water-borne diseases the most common are giardiasis and cryptosporidiosis but in neither is it clear whether the infections are predominantly of human or animal origin. The place of haemorrhagic colitis and of S. zooepidemicus infection is not yet apparent, both may emerge as important zoonoses. Streptobacillary fever, on the other hand, seems unlikely to recur with normal hygienic standards of water and milk supply. Of the occupational zoonoses Q fever and leptospirosis are the most important. Although only 1,330 cases of Q fever were reported in 10 years, it is a severe disease; 123 of them had endocarditis. Leptospirosis probably increased in incidence and emerged as a new disease of farmers and others working with cattle. S. suis type 2, a ‘new’ disease, remained a rarity. Zoonoses acquired from pets made up only a small proportion of human zoonotic infections and the only apparent change was an increase in psittacosis, the reason for which is unknown. Lastly, among the zoonoses acquired from wild and captive animals the viral haemorrhagic fevers have emerged as an important hazard in hospitals and laboratories.     

The occurrence of cadmium in some types of food]

An examination of 732 samples of foods of animal and vegetable origin revealed that 95% sea fish products, 94% samples of sea and fresh-water fish, 69.9% samples of foods of vegetable origin and 32.9% samples of foods of animal origin -- tinned beefand pork -- patés and spreads -- did not comply with the requirements of the standard on contaminants in foods for cadmium content. Together with the investigation of cadmium content in foods the applied method of atomic absorption spectrophotometry was tested, from the point of interferences during establishing the actual cadmium content; at the same time, this study concerned cadmium losses during the process of mineralization of the biologic material samples. It was concluded that the measured cadmium values were affected by the presence of a higher content of sodium chloride in the samples. The re-gained yield of cadmium by the used method of mineralization is 85%.     

Do we need pathogen-free livestock for food safety?

The reduction of the entry of pathogens in the food chain is an important premise in improving the safety of food of animal origin. Since food animals are the main reservoir for pathogens, the prevalence of pathogens in livestock is of great importance. Unfortunately, classical measures to improve animal health can not exclude the presence of the main food-borne zoonotic agents (Salmonella, Campylobacter, Listeria monocytogenes, verotoxinogene Escherichia coli, Toxoplasma gondii) in "clinically healthy" animals. Absence of pathogens in livestock must be regarded as an unrealistic aim. To achieve an effective improval of product safety through logistical, hygienic or technological measures both farmers and food producers need valid data about the prevalence of pathogens in livestock, in each animal and in raw material of animal origin, respectively. Yet available data are insufficient. New European directives and regulations concerning monitoring and control of zoonosis demand the systematic control of presence of zoonotic agents in livestock and later steps of the food chain.     

Tasks of public veterinary affairs in environmental hygiene]

The involvement of official veterinarians in tasks of environmental hygiene is demonstrated under differentiation of the following working-fields: animal waste-removal, animal health protection, animal welfare, and controlling of foods of animal origin. Thereby it results that nearly all sections of public veterinary affairs are connected with environmental aspects to a high degree.     

Evidence-based identification of the most important livestock related zoonotic diseases in Kampala, Uganda

Urban and peri-urban livestock farming in developing countries plays an important role in food security in cities; however it brings with it zoonotic risks. The present study was conducted to identify the most important livestock farming-related zoonotic diseases among the human population in urban and peri-urban areas of Kampala, Uganda and to assess the risks from such farming. A framework for identifying livestock farming-related significant zoonoses was developed. The process consisted of screening of medical record summaries for zoonotic diagnoses, selection of the zoonoses which are related to livestock farming, case estimation of the identified zoonoses and evidence-based reassurance of the importance of diseases. Medical records in the Mulago National Referral Hospital were used for the analysis. Leaders and residents of 75 Local Councils (LC1s: villages; 48 urban, 11 peri-urban and 16 rural) randomly selected in Kampala were interviewed for information regarding livestock farming systems, value chains and use of medical service units. Twelve zoonoses were identified in the screening and four out of them were related to livestock farming: animal sourced food-borne gastroenteritis, brucellosis, Taenia solium neuro-cysticercosis and Mycobacterium bovis tuberculosis. Livestock farming, value chain and severity of the diseases confirmed that all four diseases were important. Poor geographical correlation between animals in peri-urban and rural areas and patients in urban areas suggested that the majority of these zoonoses were caused by informally-marketed foods.     

Risk factors in causing outbreaks of food-borne illness originating in schoollunch facilities in Japan

We reviewed records of all outbreaks of food-borne illnesses due to schoollunch in Japan from 1987 through 1996 to determine the risk factors causing these outbreaks. Major hazards in 269 outbreaks were Salmonella spp., Campylobacter jejuni, Escherichia coli and Staphylococcus aureus. Foods including uncooked or partially cooked items, salad or egg products presented a high risk in 62 outbreaks with confirmed food sources. Contaminated food items were involved in 29 incidents (46.8%); storage of foods for an extended period before serving in 29 incidents (46.8%), inadequate cooking and cross contamination in 21 incidents (33.9%) each; infected employees in nine incidents (14.5%).     

动物性食品兽药残留的快速筛选方法

在人类消费的可食性动物组织或产品中出现兽药和其代谢物残留可能将对消费者造成不同程度的毒害,这迫切要求开发具有快速、简易、敏感性好等特征的检测方法。本文对动物性食品中兽药和其代谢物残留的微生物学、免疫学、生物感应器、色谱学等快速筛选方法的检测原理、现状及研究进展作一综述。     

Can epidemiology and economics make a meaningful contribution to national animal-disease control?

The general role of veterinary epidemiology and economics to national animal-disease control throughout the world is considered for the four main groupings of animal diseases: zoonotic, food-borne, endemic and epidemic diseases. This is done by considering how veterinary epidemiology and economics has contributed to priority setting (which diseases come first?), decision-making (for a given disease, which strategy is best?), and disease control implementation (how can optimal delivery and adoption of selected interventions best be achieved?). Within each of these categories, progress made and future opportunities are discussed. In addition, a review is made of how veterinary epidemiology and economics has been institutionalised. We conclude that veterinary epidemiology and economics holds a unique role in the development of national policies and strategies for improved animal health world-wide. However, we consider that we must capitalise more on the unique comparative advantage of the partnership between veterinarians and agricultural economists. We believe that much remains to be done to improve the "institutionalisation" of veterinary epidemiology and economics, and the adoption and impact of the products of our unique partnership, particularly in countries of the developing world.     

Diseases transmitted from pets to man: an evolving concern for veterinarians.

Pets are not a major source of human infections but they can transmit certain diseases to man. This transmission usually is complex, requiring close contact with pets or their excretions and frequently involves a breach of sound hygienic practice. In some instances, pathogens of animal origin are acquired inadvertently because infectivity can persist after evidence of gross contamination has gone. Veterinarians participate in controlling zoonotic diseases by encouraging rabies vaccination and hygienic treatment of pet feces and urine, by supporting community efforts toward responsible pet ownership and by advising on precautions for handling sick animals. It is recommended that veterinarians discourage the keeping of wild or exotic animals as pets and excess fondling of pets (particularly by children and pregnant women). Clients and kennel workers should be advised to use caution with animals that have aborted.     

Presence of residues in food of animal origin and related risk

The risk related to the presence of residues in food of animal origin has to be carefully evaluated and it is important to distinguish between the residues of veterinary drugs and environmental contaminants. The first are easily monitored and only difficulty and occasionally exceed MRL concentrations, whereas the second ones can have prolonged and high level exposures. The Safety Margins of environmental contaminants are thus lower, and the risk increases for high level consumers. It is therefore important to ovoid transfer of pollutants to food of animal origin, especially when local contamination occur.     

Presence of Residues in Food of Animal Origin and Related Risk

The risk related to the presence of residues in food of animal origin has to be carefully evaluated and it is important to distinguish between the residues of veterinary drugs and environmental contaminants. The first are easily monitored and only difficultly and occasionally exceed MRL concentrations, whereas the second ones can have prolonged and high level exposures. The Safety Margins of environmental contaminants are thus lower, and the risk increases for high level consumers. It is therefore important to ovoid transfer of pollutants to food of animal origin, especially when local contamination occur.