Infection of laboratory workers with hantavirus acquired from immunocytomas propagated in laboratory rats

Pet Rats as the Likely Reservoir for Human Seoul Orthohantavirus Infection

Seoul orthohantavirus (SEOV) is a rat-associated zoonotic pathogen with an almost worldwide distribution. In 2019, the first autochthonous human case of SEOV-induced hemorrhagic fever with renal syndrome was reported in Germany, and a pet rat was identified as the source of the zoonotic infection. To further investigate the SEOV reservoir, additional rats from the patient and another owner, all of which were purchased from the same vendor, were tested. SEOV RNA and anti-SEOV antibodies were found in both of the patient's rats and in two of the three rats belonging to the other owner. The complete coding sequences of the small (S), medium (M), and large (L) segments obtained from one rat per owner exhibited a high sequence similarity to SEOV strains of breeder rat or human origin from the Netherlands, France, the USA, and Great Britain. Serological screening of 490 rats from breeding facilities and 563 wild rats from Germany (2007-2020) as well as 594 wild rats from the Netherlands (2013-2021) revealed 1 and 6 seropositive individuals, respectively. However, SEOV RNA was not detected in any of these animals. Increased surveillance of pet, breeder, and wild rats is needed to identify the origin of the SEOV strain in Europe and to develop measures to prevent transmission to the human population.

A Portable Diagnostic Assay, Genetic Diversity, and Isolation of Seoul Virus from Rattus norvegicus Collected in Gangwon Province, Republic of Korea

Seoul virus (SEOV), an etiological agent for hemorrhagic fever with renal syndrome, poses a significant public health threat worldwide. This study evaluated the feasibility of a mobile Biomeme platform for facilitating rapid decision making of SEOV infection. A total of 27 Rattus norvegicus were collected from Seoul Metropolitan City and Gangwon Province in Republic of Korea (ROK), during 2016-2020. The serological and molecular prevalence of SEOV was 5/27 (18.5%) and 2/27 (7.4%), respectively. SEOV RNA was detected in multiple tissues of rodents using the Biomeme device, with differences in Ct values ranging from 0.6 to 2.1 cycles compared to a laboratory benchtop system. Using amplicon-based next-generation sequencing, whole-genome sequences of SEOV were acquired from lung tissues of Rn18-1 and Rn19-5 collected in Gangwon Province. Phylogenetic analysis showed a phylogeographical diversity of rat-borne orthohantavirus collected in Gangwon Province. We report a novel isolate of SEOV Rn19-5 from Gangwon Province. Our findings demonstrated that the Biomeme system can be applied for the molecular diagnosis of SEOV comparably to the laboratory-based platform. Whole-genome sequencing of SEOV revealed the phylogeographical diversity of orthohantavirus in the ROK. This study provides important insights into the field-deployable diagnostic assays and genetic diversity of orthohantaviruses for the rapid response to hantaviral outbreaks in the ROK.

Seoul Virus Infection and Spread in United States Home-Based Ratteries: Rat and Human Testing Results From a Multistate Outbreak Investigation

BACKGROUND

During 2017, a multistate outbreak investigation occurred after the confirmation of Seoul virus (SEOV) infections in people and pet rats. A total of 147 humans and 897 rats were tested.

METHODS

In addition to immunoglobulin (Ig)G and IgM serology and traditional reverse-transcription polymerase chain reaction (RT-PCR), novel quantitative RT-PCR primers/probe were developed, and whole genome sequencing was performed.

RESULTS

Seventeen people had SEOV IgM, indicating recent infection; 7 reported symptoms and 3 were hospitalized. All patients recovered. Thirty-one facilities in 11 US states had SEOV infection, and among those with ≥10 rats tested, rat IgG prevalence ranged 2%-70% and SEOV RT-PCR positivity ranged 0%-70%. Human laboratory-confirmed cases were significantly associated with rat IgG positivity and RT-PCR positivity (P = .03 and P = .006, respectively). Genomic sequencing identified >99.5% homology between SEOV sequences in this outbreak, and these were >99% identical to SEOV associated with previous pet rat infections in England, the Netherlands, and France. Frequent trade of rats between home-based ratteries contributed to transmission of SEOV between facilities.

CONCLUSIONS

Pet rat owners, breeders, and the healthcare and public health community should be aware and take steps to prevent SEOV transmission in pet rats and to humans. Biosecurity measures and diagnostic testing can prevent further infections.

Viral Disease

This chapter discusses infections of rats with viruses in the following 14 virus families: Adenoviridae, Arenaviridae, Coronaviridae, Flaviviridae, Hantaviridae, Hepeviridae, Herpesviridae, Paramyxoviridae, Parvoviridae, Picornaviridae, Pneumoviridae, Polyomaviridae, Poxviridae, and Reoviridae . Serological surveys indicate that parvoviruses, coronaviruses, cardioviruses, and pneumoviruses are the most prevalent in laboratory rats. A new polyomavirus and a new cardiovirus that cause disease in laboratory rats are described. Metagenomic analyses of feces or intestinal contents from wild rats have detected viruses from an additional nine virus families that could potentially cause infections in laboratory rats.

Wild Rats, Laboratory Rats, Pet Rats: Global Seoul Hantavirus Disease Revisited

Recent reports from Europe and the USA described Seoul orthohantavirus infection in pet rats and their breeders/owners, suggesting the potential emergence of a “new” public health problem. Wild and laboratory rat-induced Seoul infections have, however, been described since the early eighties, due to the omnipresence of the rodent reservoir, the brown rat Rattus norvegicus. Recent studies showed no fundamental differences between the pathogenicity and phylogeny of pet rat-induced Seoul orthohantaviruses and their formerly described wild or laboratory rat counterparts. The paucity of diagnosed Seoul virus-induced disease in the West is in striking contrast to the thousands of cases recorded since the 1980s in the Far East, particularly in China. This review of four continents (Asia, Europe, America, and Africa) puts this “emerging infection” into a historical perspective, concluding there is an urgent need for greater medical awareness of Seoul virus-induced human pathology in many parts of the world. Given the mostly milder and atypical clinical presentation, sometimes even with preserved normal kidney function, the importance of simple but repeated urine examination is stressed, since initial but transient proteinuria and microhematuria are rarely lacking.

Detection of Seoul virus in wild brown rats (Rattus norvegicus) from pig farms in Northern England

Introduction

Hantaviruses are maintained by mammalian hosts, such as rodents, and are shed in their excretions. Clinical disease can occur in humans from spillover infection. Brown rats (Rattus norvegicus) are the globally distributed reservoir host of Seoul virus (SEOV). Human cases of SEOV-associated haemorrhagic fever with renal syndrome (SEOV-HFRS)have been reported in Great Britain (GB) since 1977.

Methods

Brown rats (n=68) were trapped from a variety of peridomestic locations, with a focus on pig farms. Kidney and lung tissues were tested for viral RNA using a pan-hantavirus RT-PCR assay followed by Sanger sequencing and analysis.

Results

SEOV RNA was detected in 19 per cent (13/68, 95% CI 11 to 30) of rats and all sequences fell within SEOV lineage 9. Twelve sequences were highly similar to each other and to the previously reported GB Humber strain of SEOV (98 per cent). One rat SEOV sequence was more distant. The SEOV prevalence in rats from pig farms was significantly greater (p=0.047) than other sites sampled. No significant sex or age differences were observed among positive and negative rats.

Discussion

The results from this study suggest that SEOV could be widespread in wild rats in GB and therefore pose a potential risk to public health.

Applied Institutional Approaches for the Evaluation and Management of Zoonoses in Contemporary Laboratory Animal Research Facilities

Zoonoses, diseases transmitted between animals and humans, have been a concern in laboratory animal medicine for decades. Exposure to zoonotic organisms not only poses health risks to personnel and research animals but may also affect research integrity. Early laboratory animal programs were ineffective at excluding and preventing transmission of zoonotic diseases: the health status of the animals were often unknown, endemic diseases occurred frequently, housing conditions were less controlled, and veterinary care programs were decentralized. Over time, these conditions improved, but despite this, zoonotic diseases remain a contemporary concern. To reduce the incidence of zoonoses, management should perform an accurate risk assessment that takes into account the type of research performed, animal species used, animal sources, and housing conditions. Specific research practices, such as the use of biological materials, can also affect the risk assessment and should be considered. Once identified, the characteristics of significant zoonotic organisms can be examined. In addition, personnel attitudes and training, facility design and management, equipment availability, personal protective equipment used, standard operating procedures, and the institution’s vermin control program can impact the risk assessment. The effectiveness of the occupational health and safety program at managing risks of zoonoses should also be examined. Risk assessment, in the context of zoonotic disease prevention, is a complex exercise and is most effective when a team approach is used and includes research, husbandry, veterinary, and biosafety personnel.

High prevalence of Seoul hantavirus in a breeding colony of pet rats

As part of further investigations into three linked haemorrhagic fever with renal syndrome (HFRS) cases in Wales and England, 21 rats from a breeding colony in Cherwell, and three rats from a household in Cheltenham were screened for hantavirus. Hantavirus RNA was detected in either the lungs and/or kidney of 17/21 (81%) of the Cherwell rats tested, higher than previously detected by blood testing alone (7/21, 33%), and in the kidneys of all three Cheltenham rats. The partial L gene sequences obtained from 10 of the Cherwell rats and the three Cheltenham rats were identical to each other and the previously reported UK Cherwell strain. Seoul hantavirus (SEOV) RNA was detected in the heart, kidney, lung, salivary gland and spleen (but not in the liver) of an individual rat from the Cherwell colony suspected of being the source of SEOV. Serum from 20/20 of the Cherwell rats and two associated HFRS cases had high levels of SEOV-specific antibodies (by virus neutralisation). The high prevalence of SEOV in both sites and the moderately severe disease in the pet rat owners suggest that SEOV in pet rats poses a greater public health risk than previously considered.

A seroprevalence study to determine the frequency of hantavirus infection in people exposed to wild and pet fancy rats in England

Recent cases of acute kidney injury due to Seoul hantavirus infection from exposure to wild or pet fancy rats suggest this infection is increasing in prevalence in the UK. We conducted a seroprevalence study in England to estimate cumulative exposure in at-risk groups with contact with domesticated and wild rats to assess risk and inform public health advice. From October 2013 to June 2014, 844 individual blood samples were collected. Hantavirus seroprevalence amongst the pet fancy rat owner group was 34.1% (95% CI 23·9–45·7%) compared with 3·3% (95% CI 1·6–6·0) in a baseline control group, 2·4% in those with occupational exposure to pet fancy rats (95% CI 0·6–5·9) and 1·7% with occupational exposure to wild rats (95% CI 0·2–5·9). Variation in seroprevalence across groups with different exposure suggests that occupational exposure to pet and wild rats carries a very low risk, if any. However incidence of hantavirus infection among pet fancy rat owners/breeders, whether asymptomatic, undiagnosed mild viral illness or more severe disease may be very common and public health advice needs to be targeted to this at-risk group.

Microbiological Quality Control for Laboratory Rodents and Lagomorphs

Mice (Mus musculus), rats (Rattus norvegicus), other rodent species, and domestic rabbits (Oryctolagus cuniculus) have been used in research for over 100 years. During the first half of the 20th century, microbiological quality control of lab animals was at best rudimentary as colonies were conventionally housed and little or no diagnostic testing was done. Hence, animal studies were often curtailed and confounded by infectious disease (Mobraaten and Sharp, 1999; Morse, 2007; Weisbroth, 1999). By the 1950s, it became apparent to veterinarians in the nascent field of comparative medicine that disease-free animals suitable for research could not be produced by standard veterinary disease control measures (e.g., improved sanitation and nutrition, antimicrobial treatments) in conventional facilities. Henry Foster, the veterinarian who founded Charles River Breeding Laboratories in 1948 and a pioneer in the large-scale production of laboratory rodents, stated in a seminar presented at the 30th anniversary of AALAS, “After a variety of frustrating health-related problems, it was decided that a major change in the company’s philosophy was required and an entirely different approach was essential”. Consequently, he and others developed innovative biosecurity systems to eliminate and exclude pathogens (Allen, 1999). In 1958, Foster reported on the Cesarean-originated barrier-sustained (COBS) process for the large-scale production of specific pathogen-free (SPF) laboratory rodents (Foster, 1958). To eliminate horizontally transmitted pathogens, a hysterectomy was performed on a near-term dam from a contaminated or conventionally housed colony. The gravid uterus was pulled through a disinfectant solution into a sterile flexible film isolator where the pups were removed from the uterus and suckled on axenic (i.e., germ-free) foster dams. After being mated to expand their number and associated with a cocktail of nonpathogenic bacteria to normalize their physiology and prime their immune system, rederived rodents were transferred to so-called barrier rooms for large-scale production. The room-level barrier to adventitious infection entailed disinfection of the room, equipment, and supplies, limiting access to trained and properly gowned personnel, and the application of new technologies such as high-efficiency particulate air-filtration of incoming air (Dubos and Schaedler, 1960; Foster, 1980; Schaedler and Orcutt, 1983; Trexler and Orcutt, 1999). The axenic and associated rodents mentioned in the COBS process are collectively classified as gnotobiotic to indicate that they have a completely known microflora. By contrast, barrier-reared rodent colonies are not gnotobiotic because they are housed in uncovered cages and thus acquire a complex microflora from the environment, supplies, personnel, and other sources. Instead, they are described as SPF to indicate that according to laboratory testing, they are free from infection with a defined list of infectious agents, commonly known as an ‘exclusion’ list.

Biosafety Recommendations on the Handling of Animal Cell Cultures

The first steps in tissue culture are dating back to the beginning of the nineteenth century when biosafety measures did not yet exist. Later on, animal cell culture became essential for scientific research, diagnosis and biotechnological activities. Along with this development, biosafety concerns have emerged pointing to the risks for human health and in a lesser extent for the environment associated to the handling of animal cell cultures. The management of these risks requires a thorough risk assessment of both the cell cultures and the type of manipulation prior the start of any activity. It involves a case-by-case evaluation of both the intrinsic properties of the cell culture genetically modified or not and the probability that it may inadvertently or intentionally become infected with pathogenic micro-organisms. The latter hazard is predominant when adventitious contaminants are pathogenic or have a better capacity to persist in unfavourable conditions. Consequently, most of the containment measures primarily aim at protecting cells from adventitious contamination. Cell cultures known to harbour an infectious etiologic agent should be manipulated in compliance with containment measures recommended for the etiologic agent itself. The manipulation of cell cultures from human or primate origin necessitates the use of a type II biosafety cabinet. The scope of this chapter is to highlight aspects relevant for the risk assessment and to summarize the main biosafety recommendations and the recent technological advances allowing a mitigation of the risk for the handling of animal cell cultures.

Comment on Jameson et al.: Prevalence of antibodies against hantaviruses in serum and saliva of adults living or working on farms in Yorkshire, United Kingdom

This British hantavirus IgG prevalence study, aimed at 119 asymptomatic farmers in England, and using indirect immunofluorescence assay (IFA) as screening technique, concluded that rat-transmitted Seoul virus (SEOV) might be the main suspect as hantaviral pathogen in the UK. Exactly the same conclusion, using the same IFA screening technique, resulted from a 1994 serosurvey in the same country, and in 627 clinical cases plus 100 healthy controls. SEOV-positive study subjects were also mainly farmers with heavy rat-exposure, but residing in Northern-Ireland, a region where all other known rodent reservoirs for pathogenic hantaviruses are known to be absent, except the wild rat. A rodent capture action in and around the farms of eight seropositives confirmed SEOV seropositivity in 21.6% of 51 rats. All SEOV seropositives were patients, hospitalized with an acute feverish condition, a majority of which having the clinical picture of hantavirus-induced nephropathy, known as hemorrhagic fever with renal syndrome (HFRS). Leptospirosis, often mimicking perfectly HFRS, was serologically excluded. Thus, SEOV was established as a human hantaviral pathogen in the UK and in Europe 20 years ago.

Guidelines for the use of cell lines in biomedical research

Cell-line misidentification and contamination with microorganisms, such as mycoplasma, together with instability, both genetic and phenotypic, are among the problems that continue to affect cell culture. Many of these problems are avoidable with the necessary foresight, and these Guidelines have been prepared to provide those new to the field and others engaged in teaching and instruction with the information necessary to increase their awareness of the problems and to enable them to deal with them effectively. The Guidelines cover areas such as development, acquisition, authentication, cryopreservation, transfer of cell lines between laboratories, microbial contamination, characterisation, instability and misidentification. Advice is also given on complying with current legal and ethical requirements when deriving cell lines from human and animal tissues, the selection and maintenance of equipment and how to deal with problems that may arise.

Guidelines for the use of cell lines in biomedical research

Cell-line misidentification and contamination with microorganisms, such as mycoplasma, together with instability, both genetic and phenotypic, are among the problems that continue to affect cell culture. Many of these problems are avoidable with the necessary foresight, and these Guidelines have been prepared to provide those new to the field and others engaged in teaching and instruction with the information necessary to increase their awareness of the problems and to enable them to deal with them effectively. The Guidelines cover areas such as development, acquisition, authentication, cryopreservation, transfer of cell lines between laboratories, microbial contamination, characterisation, instability and misidentification. Advice is also given on complying with current legal and ethical requirements when deriving cell lines from human and animal tissues, the selection and maintenance of equipment and how to deal with problems that may arise.

Virus contaminations of cell cultures - A biotechnological view

In contrast to contamination by microbes and mycoplasma, which can be relatively easily detected, viral contamination present a serious threat because of the difficulty in detecting some viruses and the lack of effective methods of treating infected cell cultures. While some viruses are capable of causing morphological changes to infected cells (e.g. cytopathic effect) which are detectable by microscopy some viral contaminations result in the integration of the viral genome as provirus, this causes no visual evidence, by means of modification of the cellular morphology. Virus production from such cell lines, are potentially dangerous for other cell cultures (in research labs)by cross contaminations, or for operators and patients (in the case of the production of injectable biologicals) because of potential infection. The only way to keep cell cultures for research, development, and the biotech industry virus-free is the prevention of such contaminations. Cell cultures can become contaminated by the following means: firstly, they may already be contaminated as primary cultures (because the source of the cells was already infected), secondly, they were contaminated due to the use of contaminated raw materials, or thirdly, they were contaminated via an animal passage. This overview describes the problems and risks associated with viral contaminations in animal cell culture, describes the origins of these contaminations as well as the most important virsuses associated with viral contaminations in cell culture. In addition, ways to prevent viral contaminations as well as measures undertaken to avoid and assess risks for viral contaminations as performed in the biotech industry are briefly described.

Cell culture contamination

Microbial contamination is a major issue in cell culture, but there are a range of procedures which can be adopted to prevent or eliminate contamination. Contamination may arise from the operator and the laboratory environment, from other cells used in the laboratory, and from reagents. Some infections may present a risk to laboratory workers: containment and aseptic technique are the key defence against such risks. Remedial management of suspected infection may simply mean discarding a single potentially infected culture. However, if a more widespread problem is identified, then all contaminated cultures and associated unused media that have been opened during this period should be discarded, equipment should be inspected and cleaned, cell culture operations reviewed, and isolation from other laboratories instituted until the problem is solved. Attention to training of staff, laboratory layout, appropriate use of quarantine for new cultures or cell lines, cleaning and maintenance, and quality control are important factors in preventing contamination in cell culture laboratories.

Travellers and viral haemorrhagic fevers: what are the risks?

Viral haemorrhagic fevers (VHF) are caused by zoonotic viral infections transmitted to humans directly or by ticks or mosquitoes. The overall risk to travellers is conservatively estimated at <1 in 1 million travel episodes to African countries where infection is present, and febrile patients returning from these countries are at least 1000 times more likely to have malaria than Lassa fever or another VHF. No cases have been reported in fellow travellers exposed to a travelling case and only one asymptomatic seroconversion (to Lassa) has been reported in over 2000 contacts following care of VHF cases in modern Western hospital settings. However, healthcare-associated transmission of infection has been a major problem in some endemic settings. The potential for healthcare-associated infection and the threats posed by unrecognised or new agents necessitate a high index of suspicion and a standardised risk assessment approach to febrile travellers. Travel-related hantavirus infections are increasingly being reported from Europe and the Americas. This article summarises the epidemiology and reports of travel-related VHF cases in the past 40 years, together with strategies for their recognition, management and prevention.

Role of housing modalities on management and surveillance strategies for adventitious agents of rodents

Specific pathogen-free (SPF) rodents for modern biomedical research need to be free of pathogens and other infectious agents that may not produce disease but nevertheless cause research interference. To meet this need, rodents have been rederived to eliminate adventitious agents and then housed in room- to cage-level barrier systems to exclude microbial contaminants. Because barriers can and do fail, routine health monitoring (HM) is necessary to verify the SPF status of colonies. Testing without strict adherence to biosecurity practices, however, can lead to the inadvertent transfer of unrecognized, inapparent agents among institutions and colonies. Microisolation caging systems have become popular for housing SPF rodents because they are versatile and provide a highly effective cage-level barrier to the entry and spread of adventitious agents. But when a microisolation-caged colony is contaminated, the cage-level barrier impedes the spread of infection and so the prevalence of infection is often low, which increases the chance of missing a contamination and complicates the corroboration of unexpected positive findings. The expanding production of genetically engineered mutant (GEM) rodent strains at research institutions, where biosecurity practices vary and the risk of microbial contamination can be high, underscores the importance of accurate HM results in mitigating the risk of the introduction and spread of microbial contaminants with the exchange of mutant rodent strains among investigators and institutions.

Electron microscopy reveals the presence of viruses in mouse embryonic fibroblasts but neither in human embryonic fibroblasts nor in human mesenchymal cells used for hESC maintenance: toward an implementation of microbiological quality assurance program in stem cell banks

Human embryonic stem cells (hESCs) are expected to open up new avenues in regenerative medicine by allowing the generation of transplantable cells to be used in future cell replacement therapies. Maintenance of hESCs in the presence of xenogenic compounds is likely to prevent their use in future therapeutic applications in humans. Recently, it has been claimed that human foreskin-derived human embryonic fibroblast (HEFs) and human adult marrow cells have the ability to support prolonged expansion of hESCs in culture similar to murine feeders. Here, to minimize the use of xenogenic components for hESC maintenance, we performed transmission electron microscopy-based microbiological studies in an attempt to implement a microbiological Quality Assurance Program in Stem Cell Banks by determining the potential presence of viral particles in MEFs compared with human HEFs and bone marrow-derived mesenchymal cells. We observed in three out of nine MEF samples (33.3%) viruses belonging to the Retroviridae family. Within the Retroviridae family, these viruses have a C morphology, which indicates they belong to the subfamily Orthoretroviridae. In contrast, no viral particles could be observed in either the HEF samples (n = 5) or the human BM-derived mesenchymal cells (n = 9) analyzed. Based on these experimental microbiological data, we recommend the implementation of microbiological Quality Assurance Programs by means of transmission electron microscopy as a routine technique to assess the potential presence of viral particles in any feeder cell used in stem cell banks and support the use of human cells rather than murine cells as feeders to maintain hESC cultures in an undifferentiated state.

Changing medium and passaging cell lines

Cell lines are widely used in biomedical research. This protocol describes the methods used routinely to change the medium and passage the cells. Medium changes keep the cells healthy by providing fresh nutrients, while cell passage or splitting is required to maintain cells in exponential growth. Despite the simplicity of the methods used, each cell line has idiosyncracies. Whether working with one or several cell lines, there is no substitute for knowledge of their needs, including the range of phenotypes and growth patterns under different physical and nutrient conditions. Given the necessary care and attention, most cell lines are easy to maintain and grow.

The development of ‘feeder’ cells for the preparation of clinical grade hES cell lines: Challenges and solutions

The development of human embryonic stem cell (hESC) lines for research and therapy is hampered by the need to improve the basic methodologies for cell culture expansion. In most current methods hESC lines are cultured on a mouse or human feeder cell layer which appears to be the most reliable way to maintain cells stably in the undifferentiated state. However, co-culture introduces complications for studying stem cell biology and the delivery of safe therapies for the future. This article reviews the specific risks associated with any proposed clinical use of feeder cells of mouse origin and compares these with the benefits and risks of using human feeder cells. The further work required to establish clinical grade feeder cell lines for hESC line culture is significant and costly. Much work is being done to find feeder-free culture systems but these are at an early stage of development and there may be consequences that affect the value of the hESCs for research and development. These challenges should be viewed in the context of the huge amount of work that will be required over many years to develop robust differentiation protocols and establish fully defined procedures and adequate safety data for embryonic stem cell products.

Viral Disease

This chapter discusses the infections caused by DNA viruses and also RNA viruses. The chapter focuses on the detection, diagnosis, risk assessment, and decision-making regarding viral infections. Several infections caused by DNA viruses are parvoviruses, rat cytomegalovirus, poxviruses, adenovirus, and papovavirus. Several RNA viruses and infections caused by these viruses are coronaviruses, paramyxoviruses, rotavirus and reovirus, and picornaviruses. Monitoring for viral infections should cover at least three venues: animals in established breeding and experimental colonies, animals held in entry quarantine, and animal tissues and products destined for in vivo use. For established colonies, monitoring should be tailored to local conditions. Effective monitoring should encompass sampling on a pre-arranged schedule, which can be intensified if evidence or suspicion of viral infection emerges. Because viral infections of rats can spread insidiously, early detection and epidemiologic “staging” should employ a detection matrix that includes clinical observation, appropriate sampling, and sensitive and specific diagnostic testing.

Diagnostic approaches for viruses and prions in stem cell banks

Some stem cell lines may contain an endogenous virus or can be contaminated with exogenous viruses (even of animal origin) and may secrete viral particles or express viral antigens on their surface. Moreover, certain biotechnological products (e.g. bovine fetal serum, murine feeder cells) may contain prion particles. Viral and prion contamination of cell cultures and "feeder" cells, which is a common risk in all biotechnological products derived from the cell lines, is the most challenging and potentially serious outcome to address, due to the difficulty involved in virus and prion detection and the potential to cause serious disease in recipients of these cell products. Stem cell banks should introduce adequate quality assurance programs like the microbiological control program and can provide researchers with valuable support in the standardization and safety of procedures and protocols used for the viral and prion testing and in validation programs to assure the quality and safety of the cells.

Emerging viral infections

"Emerging infections" have been defined as infections that have newly appeared, that have appeared previously but are expanding in incidence and geographic range, or that threaten to increase in the near future. This article focuses on nine emerging viral infectious agents. These viruses illustrate how such agents emerge: by encroaching on previously unvisited habitats (eg, hantaviruses), by air travel (eg, SARS), and by accidental importation (eg, monkeypox). Additionally, the example of SARS demonstrates not only how quickly emerging viral infections can spread but also how quickly they can be identified and contained with motivated cooperation.

Virus PCR assay panels: an alternative to the mouse antibody production test

Antibody production tests have traditionally been used to test biological materials for viral contamination. Now molecular biology techniques have emerged as an alternative. The authors compare MAP testing with PCR-based detection methods, focusing on differences in animal use, laboratory requirements, sample size, and limits of detection.

Genetic characterisation of a Hantavirus isolated from a laboratory-acquired infection

Seoul (SEO) viruses belong to the Hantavirus genus (family Bunyaviridae), cause the moderate form of haemorrhagic fever with renal syndrome, and have been associated with laboratory-acquired infections in many countries. To investigate the pedigree of an isolate, designated IR461, which was obtained from a laboratory-acquired infection in a UK research institute, we determined the nucleotide sequences of the small (S) and medium (M) genome segments. In addition, we determined the sequences of the S segments of two Chinese isolates (R22 and L99) and an American isolate (Tchoupitoulas [TCH]). The S segments range within 1769-1785 nucleotides in length and showed identities of >88% in nucleotide sequence and 97% in amino acid sequence to those of published S segment sequences. The M RNA segment of IR461 is 3651 nucleotides long and shows >84% identity at the nucleotide level and >98% at the amino acid level to the M segments of other SEO viruses. These data confirm that SEO viruses show the least diversity within the Hantavirus genus. Phylogenetic analyses of the sequences showed geographic clustering of the Chinese SEO viruses, and that IR461 was more closely related to SEO viruses isolated in the New World than to those from the Far East.

Low pH-induced cytopathic effect--a survey of seven hantavirus strains

Hantaviruses do not produce cytopathic effects (CPE) in cell culture. However, a syncytial CPE can be induced in 7-day cultures of hantavirus growing in Vero E6 cells by reduction of the pH to approximately 6.2 using a HEPES based buffer. The appearance of this acid induced CPE was examined for seven different hantavirus strains. The differences noted were striking and reflected the taxonomic differences between hantaviruses. At 10-100 TCID50% the size of syncytial foci was very large for Seoul type viruses and smallest for Puumala viruses. The size of syncytia for Hantaan (HTN) virus was intermediate between Puumala (PUU) and Seoul (SEO) type viruses.

Laboratory-associated infections and biosafety

An estimated 500,000 laboratory workers in the United States are at risk of exposure to infectious agents that cause disease ranging from inapparent to life-threatening infections, but the precise risk to a given worker unknown. The emergence of human immunodeficiency virus and hantavirus, the continuing problem of hepatitis B virus, and the reemergence of Mycobacterium tuberculosis have renewed interest in biosafety for the employees of laboratories and health care facilities. This review examines the history, the causes, and the methods for prevention of laboratory-associated infections. The initial step in a biosafety program is the assessment of risk to the employee. Risk assessment guidelines include the pathogenicity of the infectious agent, the method of transmission, worker-related risk factors, the source and route of infection, and the design of the laboratory facility. Strategies for the prevention and management of laboratory-associated infections are based on the containment of the infectious agent by physical separation from the laboratory worker and the environment, employee education about the occupational risks, and availability of an employee health program. Adherence to the biosafety guidelines mandated or proposed by various governmental and accrediting agencies reduces the risk of an occupational exposure to infectious agents handled in the workplace.

Characterization of the mode of Hantaan virus infection in adult mice using a nested reverse transcriptase polymerase chain reaction: transient virus replication in adult mice

A polymerase chain reaction (PCR) for the detection of hantavirus genome was established and applied to analyze the mode of infection of Hantaan virus in adult ICR mice. The cDNA for the S genome segment of Hantaan virus was reverse-transcribed from the total RNA of organs of the infected mice. The sequence in the S genome segment of Hantaan virus was successfully amplified by reverse transcriptase (RT)-PCR followed by nested PCR. In 5-week-old ICR mice inoculated intraperitoneally with Hantaan virus, strain 76-118 (1.3 x 10(5) FFU/mouse), the virus was detected in clots and lungs from 3 to 10 days post-inoculation (p.i.) by nested PCR and virus-isolation techniques. No virus was detected in any specimens collected on 1 day and after 28 days p.i., and in spleens and brains through the observation period by both methods. The antibody which was measured by indirect immunofluorescence antibody assay (IFA) appeared at 7 days p.i. and the geometric mean titer was elevated to its maximum level of 1:203 at 10 days p.i., maintaining the same level until 35 days p.i. These results suggest that adult mice are transiently infected with Hantaan virus.

Hantavirus: an increasing problem?

Hantaviruses are enveloped RNA viruses and members of the Bunyaviridae family. They are transmitted from various rodent hosts by inhalation of infected urine, saliva or faeces. Infection in rodent hosts is inapparent but persists for life. Person-to-person spread of hantavirus has not been described. Two main presentations of the disease occur. Haemorrhagic fever with renal syndrome (HFRS) is due to Hantaan, Seoul, Puumala, Porogia and Belgrade viruses. In general HFRS due to Hantaan, Porogia and Belgrade viruses is more severe and has higher mortality than that due to Puumala (nephropathia epidemica) or Seoul viruses. Hantaan is predominant in the Far East (Korea, Japan, China), Porogia and Belgrade in the Balkans, and Puumala in Western Europe; Seoul has a world-wide distribution. Hantavirus pulmonary syndrome (HPS) is a recently described infection with high mortality (60%) due to adult respiratory distress syndrome. The virus (Muerto Canyon Virus) is a hantavirus but different genotypically from previous strains. Management of hantavirus infections may require bed-rest, sedation, circulatory and ventilatory support and renal dialysis. Ribavirin if administered early in the illness may be of benefit.

Comparison of nucleotide sequences of M genome segments among Seoul virus strains isolated from eastern Asia

The nucleotide sequences of the M genome segments of three Seoul virus strains (KI strains) which were isolated from urban rats inhabiting the same enzootic focus between 1983 and 1988 were compared. The viral cDNAs were amplified by PCR and were directly sequenced. The nucleotide sequences of KI strains were extremely homologous regardless of isolation year (less than 10 substitutions in 3651 nucleotides, less than 4 substitutions in 1133 amino acids). In addition, the nucleotide sequence of the KI strain isolated in 1983 (KI-83-262) was also quite similar to that of other Seoul viruses, which were isolated from laboratory rats in Japan (strain SR-11, 98.1% and B-1 strain, 96.5%), from an urban rat in Korea (Seoul 80-39, 96.5%) and from an urban rat in China (R22 strain, 93.4%). All possible N-glycosylation sites in the deduced amino acid sequences were conserved among all Seoul viruses examined. The nucleotide and amino acid sequences of Seoul virus strains were highly conserved although they were isolated from various districts of eastern Asia. These results indicate the genetic stability of Seoul virus strains maintained under a natural environment and the homology of Seoul viruses isolated from various districts of eastern Asia. The relationship among Seoul virus strains isolated from eastern Asia was compared by phylogenetic analysis.

Serological evidence of Hantavirus disease in Northern Ireland

Since, to our knowledge, no clinically documented cases of haemorrhagic fever with renal syndrome (HFRS) have been reported in Northern Ireland, a sero-epidemiological study was carried out to assess the degree of Hantavirus immunity in a group of 627 Northern Irish patients presenting with symptoms suggestive of HFRS and 100 healthy controls. IFA screening for IgG Hantavirus specific antibodies was carried out with a panel of up to 9 different Hantaviral antigens. IgM screening was performed using a commercially available mu-capture ELISA based upon two recombinant Hantaviral nucleocapsid antigens. A seropositivity of 2.1% (15/727) was recorded, with an almost exclusive reaction against a rat-derived R22VP30 strain of the Seoul serotype. Sole reliance upon non-rat-derived classic screening antigens Hantaan (HTN 76-118) and Puumala (CG 18-20) would have resulted in the detection of only 2/15 (13.3%) of cases in IgG IFA, and 8/14 (57.1%) of the cases in IgG ELISA. The findings indicate that for the first time in Europe, and more specifically in N. Ireland, non-laboratory outbreaks of HFRS may be caused by wild rats acting as a reservoir for a Seoul-like Hantavirus. Conventional Hantavirus serology using Hantaan and Puumala as screening antigens does not appear sufficient for the detection of such cases of HFRS. Hence, we propose the addition of a rat derived Hantaviral antigen to the antigen screening panel as a means of improving the specificity of the detection methods.

Eradication of hantavirus infection among laboratory rats by application of caesarian section and a foster mother technique

Hantavirus antibodies were demonstrated by the indirect immunofluorescent antibody assay, in the serum of inbred strains of laboratory rats, during the period 1973-1982, at the Unit of Experimental Immunology in the Catholic University of Louvain, Brussels, Belgium. LOU rats, as well as immunocytomas, which were requested by laboratories in the U.K. and The Netherlands, were supplied at a time when the infection was unknown and unsuspected in Europe. Hantavirus-infected laboratory rats were rendered free of virus through re-derivation by caesarian section and suckling by virus-free foster mothers. Immunocytomas were tested for the presence of hantaviruses by implantation into seronegative laboratory rats. The strain of hantavirus causing the laboratory infection was clearly different from the one circulating in free-living bankvoles in Belgium. The exchange of laboratory rats and rat tumours in relation to the potential risk of laboratory-acquired hantavirus infection, is discussed.

Comparison of immunofluorescence and enzyme-linked immunosorbent assays for the serology of Hantaan virus infections

Three enzyme-linked immunosorbent assay (ELISA) systems based upon different principles were developed for the serology of Hantaan virus infections and compared with an indirect immunofluorescence assay (IFA). The indirect IFA was carried out with gamma-irradiated Hantaan virus-infected and uninfected Vero E6 cells fixed with ethanol (-70 degrees C) or acetone (20 degrees C) on drop slides and a FITC-coupled sheep anti-human Ig preparation. Atypical staining in the IFA was avoided by using ethanol (-70 degrees C) instead of acetone (20 degrees C) fixation. In the first ELISA ('cell-assay'), Hantaan virus-infected or uninfected Vero E6 cells were used as antigens, which after gamma-irradiation were seeded into microtiter ELISA strips. Serial dilutions of human sera were incubated and specific antibodies were demonstrated with a horseradish peroxidase (HRPO)-conjugated sheep anti-human Ig preparation. In the second ELISA ('competition-assay') an affinity-purified human Ig preparation was used as a capture antibody for Hantaan virus antigen. After incubation of serial dilutions of human sera with this coat, the reactivity of the affinity purified anti-Hantaan virus Ig coupled to HRPO was determined. In the third ELISA ('complex trapping blocking [CTB]-assay') the same capture antibody was used to react with a mixture of the antigen and serial dilutions of human sera. The reactivity with the same HRPO conjugate was then determined. The results obtained in the respective assay systems with sera from people at risk or suspected of Hantaan virus infection coincided well. The CTB-ELISA proved to be faster and more sensitive than both the other ELISA systems, without giving more non-specific reactions: it detected almost all the IFA positive samples.(ABSTRACT TRUNCATED AT 250 WORDS)