Food-borne human pathogenic viruses and their molecular detection with special consideration of noroviruses and hepatitis A virus in mussels

Viruses are increasingly important as etiological agents of gastrointestinal infections. Because of improved diagnostic methods, in particular, because of molecular biological techniques, viruses can be detected much more frequently as pathogens of foodborne diseases. Apart from the hepatitis A virus (HAV) the Norovirus (NLV) is becoming more significant. On an international level methods are developed to detect the amount of viruses which minimise PCR inhibitors and which are applicable in routine diagnostic. There are numerous routines available in the field of virus diagnostic in shellfish and oysters which are, however, not yet standardised and applicable in the whole of Europe. This review highlights viral agents their characteristics as well as food contaminated with viruses. While most of the detection methods are cited from the literature, own preliminary results of virus detection in mussels are discussed in addition.     

Animal health and foodborne pathogens: enterohaemorrhagic O157:H7 strains and other pathogenic Escherichia coli virotypes (EPEC,ETEC, EIEC,EHEC)

The majority of interactions between microorganisms and animals are based on convenient relations for both of them. Symbiotic microorganisms, like intestinal microbiota, produce important vitamins for animals and protects them from putative pathogens. In general, for monogastric animals, the main contribution of intestinal microorganisms is to supply with growth factors the animal diet, and in some cases they are responsible for providing essential vitamins (e.g. vitamin K). Some particular and relatively few microbes like viruses, bacteria, fungi, protozoa and algae are responsible for animal illness. Because microorganisms are easily dispersed, display physiological diversity, and tolerate extreme conditions, they are ubiquitous and may contaminate and grow in many products, including food and raw materials. Foodborne diseases are caused by consumption of contaminated food or beverages. Many different disease-causing pathogens can contaminate food, so there are many different foodborne infections. In addition, poisonous chemicals and biological toxins can cause disease if they are present in food. To know how a particular disease is spreading is an important matter to take appropriate steps to stop it. For example Escherichia coli O157:H7 infections can spread through contaminated food (meat, vegetables, cheese, etc.), contaminated drinking water or juices, contaminated swimming water and from person to person. Among foodborne pathogens, the most frequently detected are bacteria, but also parasitic protozoa and worms, viruses, natural toxins and other pathogenic agents like prions are important agents for foodborne diseases. Particular pathogenic types of E. coli, classified by their specific pathogenic mechanisms (toxins, adhesins, invasiveness, etc.) are actually known as E. coli virotypes. Enterohaemorrhagic E. coli (EHEC), which constitute the main part of this review, were also named verotoxigenic E. coli (VTEC) or Shiga toxigenic E. coli (STEC). EHEC strains cause haemorrhagic colitis (HC), haemolytic uremic syndrome (HUS) and thrombotic thrombocytopaenic purpura (TP) in humans. They synthetize shigatoxins (verotoxins) which are potent cytotoxic substances, adherence factors and enterohaemolysin. EHEC are responsible for many outbreaks of bloody diarrhoea caused by contaminated foods: beef, milk, fruits, juice, water, etc. The most important serogroups among EHEC are O26, O111 and O157, being O157:H7 the most relevant serotype in foodborne outbreaks. The normal intestinal microflora of cattle was found to be the most relevant reservoir of EHEC strains.     

Food as a potential vector for antibiotic resistance. 1. Relevance of residues and selected foodborne infections and intoxicants

Food of animal origin has been considered as an important vector for the transfer of antibiotic resistances from animal to man. Such a transfer is possible by three ways: through antibiotic residues in food, through the transfer of resistant foodborne pathogens or through the ingestion of resistant parts of the original food microflora and resistance transfer to pathogenic microorganisms. A literature review and own investigations were performed in order to asses the potential impact of antibiotic resistance in food on the consumer health. In the first report Salmonella and Staph, aureus isolates were screened for their antibiotic resistance profiles. As a result it could be shown that residues in fresh meat or milk are quantitatively of minor interest. The resistance profile of Salmonella depended on the origin (pig or poultry), but only serovars could be identified which are generally not responsible for systemic infections. Staph. aureus isolates did not show any resistances relevant for human medicine. In these cases food can be considered as safe concerning its role as a vector for antibiotic resistances. However, a resistance monitoring seems to be necessary.     

2008-2018年我国猪流行性腹泻病毒混合感染分析

为了解我国猪流行性腹泻病毒混合感染的地区分布情况、季节性特征和混合感染病原类型,基于中国知网、NCBI等数据库,对2008-2018年间我国猪流行性腹泻病毒混合感染病例进行统计.结果显示,全国18个省市地区统计样本数量共计6951份,其中猪流行性腹泻病毒阳性样本数3345(48.12%)份,混合感染阳性样本数1325(19.06%)份;我国中部地区猪流行性腹泻病毒混合感染率高于其他省市;冬季(12~2月)为猪流行性腹泻病毒混合感染多发季节;细菌和病毒是猪流行性腹泻病毒混合感染的主要病原,在与细菌的混合感染中,主要混合感染病原类型为大肠杆菌,在与病毒的混合感染中,可以与猪圆环病毒2型、猪轮状病毒、猪瘟病毒、猪传染性胃肠炎病毒、猪伪狂犬病毒、猪嵴病毒、猪Delta冠状病毒和猪繁殖与呼吸综合征病毒进行混合感染,混合感染主要以二重混合感染(15.41%)为主,三重混合感染和四重混合感染分别占总样本数的3.25%和0.40%.本文归纳了近10年我国猪流行性腹泻病毒混合感染的基本特征,为了解猪流行性腹泻病毒混合感染及提高疫病综合防控水平提供了一定的参考.     

Noroviruses and sapoviruses in man and farm animals

Noro- and Sapoviruses belong to the virus family Caliciviridae and are important causative agents of acute epidemic gastroenteritis in man. In many cases transmission of Noro- and Sapoviruses occurs via contaminated food or water and the respective diseases are therefore designated as food borne. Recently, the presence of Noro- and Sapoviruses in farm animals has attracted increasing attention. Clinical symptoms were observed after experimental infection of cattle and swine with members of the two virus groups. Thus far it is not known, whether virus transmission from animals to man does occur.     

Virological and serological studies on the role of PI-3 virus, BRSV, BVDV and BHV-1 on respiratory infections of cattle. I. The detection of etiological agents by direct immunofluorescence technique

Nasal cells extracted from nasal swabs obtained from 95 cattle with signs of respiratory disease, out of eleven different herds, were tested for BHV-1, PI-3 virus, BRSV and BVDV using direct immunofluorescence technique. Viral antigen positive samples were detected in seven out of eleven herds examined. Of the 95 individual diseased cattle, 19 were found positive for at least one viral antigen. It was found that especially BHV-1 and PI-3 virus are important causative agents in cattle respiratory disease, both or in combination with other pathogenic agents. Multiple infection in virologically positive herds were observed in six (9.8%) of 61 animals tested. The findings reveal that single or multiple infections of selected viruses may be present in an important range in cattle and that direct immunofluorescence technique as a rapid method, based on the detection of viral antigen in nasal swab samples, is useful to establish the viral aetiology of acute bovine respiratory disease caused by these viruses, particularly in the diagnosis of mixed viral infections.     

New emerging viral zoonoses

New developments in the field of viral transmission from animal to man can be divided into four areas of study. First are the new viral zoonoses such as diseases caused by rotaviruses, Lassa virus and the animal orthopox viruses which will be more prevalent after the cessation of mandatory vaccination against smallpox. Secondly are the numerous ubiquitous viruses, such as adeno and herpesviruses, which in healthy animals lead only to clinically inapparent infections. A typical example of the third area is the recombination and hybridisation between animal and human influenza type A viruses. The final area is concerned with the transmission of viral zoonoses to man through food of animal origin.     

Simultaneous isolation of verotoxin-producing strains of Escherichia coli O128:H2 and viruses in gastroenteritis outbreaks

Three outbreaks of gastroenteritis from which the Verotoxin producing Escherichia coli serotype O128:H2 was isolated are reported. In addition Norwalk-like viruses were detected in patients from two of the outbreaks and astrovirus in the third outbreak. While it cannot be specifically determined which of these agents played the major role in these outbreaks, the findings suggest that the viral agents need to be considered in investigations of gastroenteritis outbreaks, regardless of whether bacterial enteropathogens have also been isolated. This study points to a strong need to investigate gastroenteritis outbreaks for both bacterial and viral agents and to review in detail the asymptomatic carriage rate of Verotoxin-producing bacteria and gastroenteritis-associated viral agents; these areas of public health significance have been largely neglected.     

Public health and research perspectives on the microbial contamination of foods

Scientific advances in methodology and epidemiology have resulted in a renewed awareness of foodborne disease, and increased contact among nations of the world has stimulated rapid global distribution of foods as well as foodborne pathogens. New food vehicles are being identified for old, familiar pathogens, and new pathogens are being discovered. Current research in food microbiology has spurred development of rapid and specific methods to identify these pathogens and to assess their virulence. Organisms of recent interest, such as Bacillus, Yersinia, Campylobacter, Listeria, Sporothrix, Giardia, Cryptosporidium, and Anisakis, are the foci of new investigations, as are the more familiar foodborne pathogens, Salmonella, Shigella, Clostridium, Staphylococcus, Entamoeba and Ascaris. Some foodborne organisms, such as parasitic protozoa, serve as hosts for unique bacterial and viral symbionts but also might become infected with mammalian viruses. The remote possibility of the transmission of human immunodeficiency viruses in foodborne protozoa is discussed.     

A microbiologic study of the urban gray squirrel.

Bacteriologic, virologic, and serologic examinations were conducted on 180 urban gray squirrels (Sciurus carolinensis) during a 1-year period in a metropolitan area. Evidence was not found of infections with leptospires, enteric or other bacteria, rickettsial agents, Francisella tularensis, or arthropod-borne viruses. The squirrels were remarkably free of evidence of bacterial or viral infections of importance to man and lower animals.     

猪腹泻相关肠道病毒分离研究进展

猪腹泻是全球养猪生产中最常见的疾病之一,病毒性腹泻具有传播快、致死率高和防控难的特点。常见的引起仔猪腹泻的病毒包括猪流行性腹泻病毒(PEDV)、猪传染性胃肠炎病毒(TGEV)和猪轮状病毒(PoRV),近几年新发现的猪δ冠状病毒(PDCoV)、猪嵴病毒(PKV)和猪急性腹泻综合征冠状病毒(SADS-CoV)也与仔猪腹泻相关。病毒分离是病毒感染诊断的金标准,也是进行病毒研究的前提。对上述6种常见猪肠道病毒的分离进展进行综述,可为掌握这些病毒的分离情况、疾病发展动向监测、疫苗研发以及猪腹泻病的防控提供参考。     

轮状病毒感染肠上皮细胞激活宿主先天免疫研究进展

轮状病毒(RV)是引起婴幼儿、幼畜禽急性肠胃炎的人畜共患病原,常与其他病原体混合感染,多以呕吐,严重水样腹泻,脱水为临床症状,感染后具有较高病死率,对人类公共卫生以及养殖业造成极大危害.RV病原相关分子模式(PAMP)可被肠上皮细胞(IECs)中一组可遗传的模式识别受体(PRR)识别,通过IECs、先天免疫细胞与RV互...     

Seafood transmitted diseases]

This paper reviews seafood related bacterial, viral and parasitological hazards for consumers worldwide. Seafood from Europe is generally regarded as safe. Food safety risks associated with aquaculture products results from contamination with biological agents, which are greater in freshwater and coastal ecosystems than in open seas. Due to the consumption conditions and the intensive investigations of imported products with contamination of pathogenic bacteria there are little seafood risks in Europe. Viral infections are associated with consumption of raw or recontaminated shellfish. There has been speculation that more than 50% of the outbreaks of unknown aethiology are due to viruses. Foodborne parasitic hazards are associated with the consumption of raw (sushi) or insufficiently heated, marinated and salted seafood.     

Recent developments in avian influenza research: epidemiology and immunoprophylaxis

Influenza A viruses have been isolated from humans, from several other mammalian species and a wide variety of avian species, among which, wild aquatic birds represent the natural hosts of influenza viruses. The majority of the possible combinations of the 15 haemagglutinin (HA) and nine neuraminidase (NA) subtypes recognized have been identified in isolates from domestic and wild birds. Infection of birds can cause a wide range of clinical signs, which may vary according to the host, the virus strain, the host's immune status, the presence of any secondary exacerbating microorganisms and environmental factors. Most infections are inapparent, especially in waterfowl and other wild birds. In contrast, infections caused by viruses of H5 and H7 subtypes can be responsible for devastating epidemics in poultry. Despite the warnings to the poultry industry about these viruses, in 1997 an avian H5N1 influenza virus was directly transmitted from birds to humans in Hong Kong and resulted in 18 confirmed infections, thus strengthening the pandemic threat posed by avian influenza (AI). Indeed, reassortant viruses, harbouring a combination of avian and human viral genomes, have been responsible for major pandemics of human influenza. These considerations warrant the need to continue and broaden efforts in the surveillance of AI. Control programmes have varied from no intervention, as in the case of the occurrence of low pathogenic (LP) AI (LPAI) viruses, to extreme, expensive total quarantine-slaughter programmes carried out to eradicate highly pathogenic (HP) AI (HPAI) viruses. The adoption of a vaccination policy, targeted either to control or to prevent infection in poultry, is generally banned or discouraged. Nevertheless, the need to boost eradication efforts in order to limit further spread of infection and avoid heavy economic losses, and advances in modern vaccine technologies, have prompted a re-evaluation of the potential use of vaccination in poultry as an additional tool in comprehensive disease control strategies. This review presents a synthesis of the most recent research on AI that has contributed to a better understanding of the ecology of the virus and to the development of safe and efficacious vaccines for poultry.     

Public health and policy

Antimicrobial agent usage data are essential for focusing efforts to reduce misuse and overuse of antimicrobial agents in food producing animals because these practices may select for resistance in bacteria of animals. Transfer of resistant bacteria from animals to humans can lead to human infection caused by resistant pathogens. Resistant infections can lead to treatment failures, resulting in prolonged or more severe illness. Multiple World Health Organization (WHO) reports have concluded that both antimicrobial resistance and antimicrobial usage should be monitored on the national level. The system for collecting antimicrobial usage data should be clear and transparent to facilitate trend analysis and comparison within and among countries. Therapeutic, prophylactic and growth promotion use should be recorded, along with route of administration and animal species and/or production class treated. The usage data should be compared to resistance data, and the comparison should be made available in a timely manner. In the United States, surveillance of antimicrobial resistance in foodborne bacteria is performed by the National Antimicrobial Resistance Monitoring System (NARMS) for enteric bacteria, however, the United States still lacks a mechanism for collecting antimicrobial usage data. Combined with antimicrobial resistance information from NARMS, antimicrobial usage data will help to direct education efforts and policy decisions, minimizing the risk that people will develop antimicrobial resistant infections as a result of eating food of animal origin. Ultimately mitigation strategies guided by usage data will be more effective in maintaining antimicrobial drugs for appropriate veterinary use and in protecting human health.     

Important virus infections of the respiratory tract in cattle from the clinical point of view

The etiological participation of different viruses in the pneumonia complex of cattle is undisputed. The significance of the individual viruses in the genesis of disease symptoms is still mostly unclear. Since the pneumonia complex of cattle is a multifactorial syndrome, vaccination programs as the only measure of prophylaxis in most cases do not show the desired effect. Against those viral agents causing self-standing diseases of the respiratory tract, specific vaccinations are applicable with success. Prerequisite for their effectiveness, however, is the exact etiological clarification of the cause of disease or of the existing infections respectively in the herd. The frequency of possible viral agents in infections of the respiratory tract in cattle from herds of the province of Schleswig-Holstein found in routine diagnostic work during the last four years is presented in addition.     

国内外食品源及动物源弯曲菌流行性及耐药性调查研究进展

弯曲菌是重要的食品源性致病微生物,在很多动物中属于正常携带细菌,能通过食物链传递给人类,可引起人类肠炎的暴发流行和食物中毒。在畜牧养殖业大量抗菌药物的使用,造成动物源弯曲菌耐药性日益增加,给人类带来健康风险。发达国家很早就开展了动物源性弯曲菌流行性和耐药性监测工作,很多发展中国家也对弯曲菌流行性和耐药性监测越来越重视,文章将就近年来国内外动物源性弯曲菌的流行及耐药情况调查工作做简单的总结,为中国动物源性弯曲菌流行性和耐药性工作的开展提供比较及理论分析数据。     

Studies on pathogenesis following single and double infection with viral hemorrhagic septicemia virus and infectious hematopoietic necrosis virus in rainbow trout (Oncorhynchus mykiss)

Rainbow trout (Oncorhynchus mykiss) were bath challenged with viral hemorrhagic septicemia (VHS) virus or infectious hematopoietic necrosis (IHN) virus or with both viruses simultaneously. The viral distribution and development of histologic lesions were examined using immunohistochemistry, while virus titer in kidney was determined by viral titration in cell culture. Single infections with VHS virus and IHN virus showed similar distributions of virus in internal organs. The early identification of virus in gill epithelium, 1 and 2 days postinfection (PI) for VHS virus and IHN virus, respectively, indicates that this organ is the point of entry for both viruses. The detection of VHS virus at 1 day PI and 3 days PI for IHN virus is indicative of kidney and spleen being the target organs for these viruses. A simultaneous infection of VHS virus and IHN virus resulted in both viruses establishing an infection. Further double infection did not result in a statistically significant lower titer of both viruses in kidney but a more restricted distribution of IHN virus in internal organs compared with the single infected group. The most striking finding is that, for IHN virus, virus was not detected in the brain in situ in the double-infected group. This study provides support for the conclusion that simultaneous infection with two piscine rhabdoviruses in a susceptible host results in some degree of interaction at the cell level, leading to a reduced systemic distribution of IHN virus.