Elimination of mouse allergens in the working environment: assessment of individually ventilated cage systems and ventilated cabinets in the containment of mouse allergens

Evaluation of Various IVC Systems According to Mouse Reproductive Performance and Husbandry and Environmental Parameters

IVC systems are marketed for improving the health and management of mouse colonies. The current study compared mouse reproductive performance and husbandry and environmental parameters among 3 high-density (HD) IVC rack systems (RS1, RS2, and RS3), which were present in separate but comparable rooms. Three breeding trios each of Swiss Webster (CFW) and BALB/c mice were placed in each rack (n = 36 female, n = 18 male). Reproductive indices were measured for 3 breeding cycles over 2 generations; indices included time to parturition, litter size and pup weight, survivability, and interbirth interval. Over 18 wk, personnel used scoring systems to evaluate each RS daily to every other week according to cage dirtiness, need for spot changing, ease of cage changing, daily health checks, and cage wash processing. Macroenvironmental parameters (temperature, relative humidity, noise, total particulate matter) were measured weekly over 14 wks. Microenvironmental parameters (temperature, relative humidity, NH₃, CO₂, O₂) of 2 cages each of male and female CFW mice (4 mice/cage) on each RS were measured at 6 time points over 2 wks. RS1 had significantly smaller mean litter sizes of CFW mice (mean ± 1 SD, 6.5 ± 2.9 pups) as compared with both RS2 (9.5 ± 1.7 pups) and RS3 (9.3 ± 3.8 pups). RS1 scored as being significantly easier to process through the cage wash. RS2 had significantly lower room noise levels (46.0 ± 5.0 dBA) but higher humidity (58.6% ± 8.9%) as compared with both RS1 (43.7% ± 9.9%) and RS3 (46.0% ± 12.0%) over the 2-wk cycle, particularly at 8 and 12 d after cage change. In conclusion, in terms of mouse reproductive performance and husbandry and environmental parameters, each system had at least 1 advantage over the other 2. Therefore, various factors should be considered when choosing an IVC system for mice.

Behavioural effects of cage systems on the G93A Superoxide Dismutase 1 transgenic mouse model for amyotrophic lateral sclerosis

Environmental factors inherent to animal facilities can impact on the neuro-behavioural phenotype of laboratory mice and genetic mouse models for human diseases. Many facilities have upgraded from traditional 'open filter top' cages (FT) to individually ventilated cage (IVC) systems, which have been shown to modify various behavioural responses of laboratory mice. Importantly, the impact of IVC housing on the G93A superoxide dismutase 1 mouse model of amyotrophic lateral sclerosis (ALS) is currently unknown. Male and female wild type-like (WT) and heterozygous SOD1^G93A mice were group-housed in FT or IVC systems from PND 30 ± 5 onwards. Body weight and motor function were assessed weekly from 15 weeks onward. Mice were also tested for cognitive abilities (i.e., fear conditioning and social recognition memory) and sensorimotor gating (i.e., prepulse inhibition: PPI). SOD1^G93A mice lost body weight, and their motor function degenerated over time compared with control littermates. Motor impairments developed faster when SOD1^G93A females were housed in IVCs. Context and cue freezing were increased in SOD1^G93A females compared with controls, whereas all SOD1^G93A mice exhibited lower acoustic startle and PPI than WT mice. IVC housing led to an increase in cue freezing in males and reduced the severity of PPI deficits in SOD1^G93A females. Overall, IVC housing impacted moderately on the SOD1^G93A phenotype but central behavioural deficits were still evident across housing conditions. Nonetheless, our findings indicate the importance of assessing the effect of cage system in genetic mouse models as these systems can modulate the magnitude and onset of genotypic differences.

Laboratory animal allergy is preventable in modern research facilities

BACKGROUND

Historical data suggest 15% of laboratory animal workers develop IgE sensitisation and 10% symptoms of laboratory animal allergy (LAA), including occupational asthma. Individually ventilated cages (IVCs) are replacing conventional open cages; we sought to evaluate their impact on the development of LAA.

METHODS

We surveyed 750 laboratory animal workers and measured airborne Mus m 1 (mouse allergen) levels in seven UK institutions. We compared the prevalence of sensitisation to mouse proteins (by specific IgE assay or skin prick test) and of work-related allergic symptoms in IVC-only and open cage units.

RESULTS

Full-shift Mus m 1 levels were lower in IVC than open cage units (geometric mean 1.00 (95% CI 0.73-1.36) versus 8.35 (95% CI 6.97-9.95) ng·m^-3; p<0.001), but varied eight-fold across the IVC units (geometric mean range 0.33-4.12 ng·m^-3). Primary analyses on data from 216 participants with ≤3 years exposure to mice revealed a lower prevalence of sensitisation in those working in IVC units compared with conventional cage units (2.4% (n=2) versus 9.8% (n=13); p=0.052). Sensitisation in IVC units varied from 0% to 12.5%; the use of fitted respiratory protection was less common in IVC units where prevalence of sensitisation was higher. Work-related allergy symptoms were more frequently reported by mouse-sensitised individuals (46.7% versus 10.9%; p<0.001) and only by those working in open cage units.

CONCLUSION

In contemporary practice, LAA is now largely preventable with the use of IVC systems and the judicious use of appropriate respiratory protection.

Predictors for Increased and Reduced Rat and Mouse Allergen Exposure in Laboratory Animal Facilities

Introduction

Exposure to rat and mouse allergens during work in laboratory animal facilities represents a risk for being sensitized and developing allergic diseases, and it is important to keep the exposure level as low as possible. The objective of this study was to characterize the personal Mus m 1 and Rat n 1 exposure during work in laboratory animal facilities, and to investigate the effect of identified predictors of increased and reduced exposure.

Methods

Mus m 1 and Rat n 1 were analysed in whole day or task-based personal air samples by enhanced sensitivity sandwich enzyme-linked immunosorbent assay. Information about cage-and-rack systems, tasks, and other conditions known to influence the allergen exposure was registered. Predictors for allergen exposure were identified by multiple linear regression analyses.

Results

The median allergen exposure was 3.0 ng m-3 Mus m 1 and 0.5 ng m-3 Rat n 1, with large task-dependent variations among the samples. The highest exposed job group were animal technicians. Cage emptying and cage washing in the cage washroom represented the highest exposure, whereas animal experiments in the lab/operation room represented the lowest exposure, with laminar airflow bench being an exposure-reducing determinant. Cage changing was the highest exposed task in the animal room, where individually ventilated cages (IVCs) were predictors of reduced exposure for both Mus m 1 and Rat n 1, whereas cage-rack systems with open shelves and sliding doors were predictors of increased Rat n 1 exposure. Cages of IVC type with positive air pressure (IVC+) as well as open shelves and sliding doors were strong predictors of increased exposure during cage emptying and cage washing.

Conclusions

Significant different exposure levels depending on type of work and task imply different risks of sensitization and allergy development. The fact that IVC+ cages have opposite impact on Mus m 1 and Rat n 1 exposure during different tasks may have positive clinical implications when taken into account.

Occupational Animal Allergy

PURPOSE OF REVIEW

This review explores animal allergen exposure in research laboratories and other work settings, focusing on causes and prevention.

RECENT FINDINGS

(1) Consistent with the hygiene hypothesis, there is new evidence that early childhood exposure to pets produces changes in the gut microbiome that likely lead to a lower risk of allergy. (2) Anaphylaxis from laboratory animal bites occurs more frequently than suggested by prior literature. (3) Animal allergens represent an occupational hazard in a wide variety of work settings ranging from fields that work with animals to public settings like schools and public transportation where allergens are brought into or are present in the workplace. Exposure to animal allergens can result in allergy, asthma, and anaphylaxis. Animal allergy has been most studied in the research laboratory setting, where exposure reduction can prevent the development of allergy. Similar prevention approaches need to be considered for other animal work environments and in all settings where animal allergens are present.

Laboratory animal allergy: a new world

PURPOSE OF REVIEW

In recent years there has been a dramatic shift in the world of animal research whereby genetically modified mice have largely supplanted rats, and individually ventilated cages have been introduced to house delicate experimental animals in place of traditional open cages. Although laboratory animal allergy remains an important cause of occupational asthma, the risks associated with contemporary practice and consequently the opportunities for primary and secondary prevention are largely unknown.

RECENT FINDINGS

Although there is clear confirmation of a widespread increase in animal experiments using mice, the evidence-base on the associated risks has lagged. Individually ventilated cages reduce ambient levels of mouse urinary protein in air but task-based exposures are unquantified. Immunological techniques to identify sensitization to mouse proteins are poorly standardized. The available evidence suggests that modern practices are, in most cases, associated with a reduced incidence of animal sensitization.

SUMMARY

There is a paucity of data to inform evidence-based practice in methods to control the incidence of laboratory animal allergy under the prevailing research environment; a better understanding of the relationship between exposures and outcome is urgently needed. As exposures decline, the relative importance of individual susceptibility will become prominent.

Laboratory Animal Allergy in the Modern Era

Laboratory animal workers face a high risk of developing laboratory animal allergy as a consequence of inhaling animal proteins at work; this has serious consequences for their health and future employment. Exposure to animal allergen remains to be the greatest risk factor although the relationship is complex, with attenuation at high allergen exposure. Recent evidence suggests that this may be due to a form of natural immunotolerance. Furthermore, the pattern of exposure to allergen may also be important in determining whether an allergic or a tolerant immune response is initiated. Risk associated with specific tasks in the laboratory need to be determined to provide evidence to devise a code of best practice for working within modern laboratory animal facilities. Recent evidence suggests that members of lipocalin allergens, such as Mus m 1, may act as immunomodulatory proteins, triggering innate immune receptors through toll-like receptors and promoting airway laboratory animal allergy. This highlights the need to understand the relationship between endotoxin, animal allergen and development of laboratory animal allergy to provide a safe working environment for all laboratory animal workers.

The characteristics, treatment and prevention of laboratory animal allergy

Laboratory animal allergy (LAA) is a pervasive problem that affects up to one-third of laboratory animal personnel. An immediate hypersensitivity reaction can be triggered by contact with antigens present in urine, hair, dander and saliva of laboratory animals. The authors provide an overview of the epidemiology, triggering mechanisms, diagnosis, treatment and risk factors of LAA. They also discuss primary and secondary prevention measures that can be taken to reduce LAA morbidity and to allow personnel suffering from LAA to safely continue to do their jobs.

Laboratory animals and respiratory allergies: the prevalence of allergies among laboratory animal workers and the need for prophylaxis

OBJECTIVE

Subjects exposed to laboratory animals are at a heightened risk of developing respiratory and allergic diseases. These diseases can be prevented by simple measures such as the use of personal protective equipment. We report here the primary findings of the Laboratory Animals and Respiratory Allergies Study regarding the prevalence of allergic diseases among laboratory animal workers, the routine use of preventive measures in laboratories and animal facilities, and the need for prevention programs.

METHODS

Animal handlers and non-animal handlers from 2 Brazilian universities (University of São Paulo and State University of Campinas) answered specific questionnaires to assess work conditions and symptoms. These subjects also underwent spirometry, a bronchial challenge test with mannitol, and skin prick tests for 11 common allergens and 5 occupational allergens (rat, mouse, guinea pig, hamster, and rabbit).

RESULTS

Four hundred fifty-five animal handlers (32±10 years old [mean±SD], 209 men) and 387 non-animal handlers (33±11 years old, 121 men) were evaluated. Sensitization to occupational allergens was higher among animal handlers (16%) than non-animal handlers (3%, p<0.01). Accessibility to personal protective equipment was measured at 85% (median, considering 73 workplaces of the animal handler group). Nineteen percent of the animal handlers indicated that they wear a respirator at all times while handling animals or working in the animal room, and only 25% of the animal handlers had received an orientation about animal-induced allergies, asthma, or rhinitis.

CONCLUSION

In conclusion, our data indicate that preventive programs are necessary. We suggest providing individual advice to workers associated with institutional programs to promote a safer work environment.

Mice prefer draught-free housing

An increasing number of rodents are housed in individually ventilated cage (IVC) systems, as these seem to be very effective for the protection of animals against infections, as well as protecting the staff against allergens. For the IVC systems to be properly ventilated, a huge amount of air has to be blown into the cage, which may cause a draught at animal level inside the cage. The aim of the present study was to evaluate the preferences of mice for differing levels of air speeds and air changes inside the cage. It has been concluded that mice do react to draughts, whereas they do not seem to be affected by a high number of air changes delivered without draught, which underlines the importance of applying draught-free IVC systems for mice.

Rodent and germplasm trafficking: risks of microbial contamination in a high-tech biomedical world

High-tech biomedical advances have led to increases both in the number of mice used for research and in exchanges of mice and/or their tissues between institutions. The latter are associated with the risk of dissemination of infectious agents. Because of the lack of international standardization of health surveillance programs, health certificates for imported rodents may be informative but may not address the needs of the importing facility. Preservation of mouse germplasm is achieved by cryopreservation of spermatozoa, embryos, or ovaries, and embryonic stem cells are used for the production of genetically engineered mice. After embryo transfer, recipients and rederived pups that test negative in microbiological screening for relevant microorganisms are released into full barrier holding areas. However, current research shows that embryos may also transmit microorganisms, especially viruses, to the recipient mice. In this article, we discuss regulations and practical issues in the shipping of live mice and mouse tissues, including spermatozoa, embryos, ovaries, and embryonic stem cells, and review work on microbial contamination of these biological materials. In addition, we present ways to reduce the risk of transmission of pathogens to mice under routine conditions.

Is there a need for special preventive medical check-ups in employees exposed to experimental animal dust?

OBJECTIVE

Due to new legal requirements in Germany, the employer must request preventive medical check-ups for activities involving exposure to dust from experimental animals in the rooms in which the animals are kept. The objective is to report our first experiences with these medical check-ups in the context of academic research.

METHODS

The check-ups were carried out since November 2005 and comprised a questionnaire and a medical examination, including a pulmonary function test with whole-body plethysmography. Respiratory, nasal and ocular symptoms related to occupational exposure to animals were documented. Participation in skin prick tests (ubiquitous inhalation allergens and laboratory animal allergens), a bronchial provocation test with methacholine, and serological examinations for total IgE and specific IgE antibodies was voluntary.

RESULTS

Data on 132 persons are presented. One hundred and six of these had already been exposed for at least 1 year. Main complaints at the workplace were sneezing and runny nose. Ocular symptoms and bronchial asthma were reported infrequently. The development of at least one of these symptoms occurred in 34% of employees with an exposure of at least 1 year. If the weekly exposure duration was at least 5 h, the proportion of employees with complaints rose to 44.9%. In employees occupationally exposed to mice and rats, work-related complaints occurred in 33.7 and 37.8%, respectively, and sensitisation rates were 12.7 and 16.3%, respectively. Employees with and without complaints differed in history of allergic symptoms, and workplace safety measures.

CONCLUSIONS

In employees with occupational contact with laboratory animal dust, the frequency of complaints was high. The results confirm the necessity of regular medical check-ups for employees with contact with laboratory animal dust. Nevertheless, the medical check-ups must be part of a prevention strategy including education, engineering controls, administrative controls, use of personal protective equipment and vocational integration.

Environmental detection of mouse allergen by means of immunoassay for recombinant Mus m 1

BACKGROUND

Mouse urinary allergens are an important cause of occupational asthma in animal facilities. Domestic exposure to mouse allergens is a risk factor for asthma among inner-city residents.

OBJECTIVE

We sought to develop a sensitive and specific assay for assessing environmental mouse allergen exposure.

METHODS

An ELISA for recombinant (r)Mus m 1 was developed by using rabbit polyclonal antibodies to rMus m 1 that were affinity purified against the natural allergen. Assay specificity was established by means of immunoblotting and ELISA. Mus m 1 levels in mouse, other mammalian allergenic products, and house dust samples from inner-city homes were compared.

RESULTS

Polyclonal antibodies to Mus m 1 showed a single 20-kd band on immunoblots against rMus m 1 and male mouse urine. Parallel dose-response curves were obtained by using mouse urine extract and natural Mus m 1 or rMus m 1. Mus m 1 was detected in mouse allergenic products (0.10-10.0 microg/mL) and in gerbil allergenic products (0.1 microg/mL) but was less than the limit of detection in epithelial extracts from 10 other animal species. Environmental measurements showed an excellent correlation between Mus m 1 levels in house dust extracts from inner-city asthma studies by using 2 different Mus m 1 standards (n=22; r=0.99; P <.001).

CONCLUSIONS

A highly sensitive ELISA has been developed with rMus m 1. This assay is suitable for monitoring domestic and environmental exposure to mouse urinary allergens.

Management of immunocompromised and infected animals

This chapter discusses the management of immunocompromised and infected animals. The microbiological quality of laboratory animals is a direct result of colony management practices and monitoring provides an after-the-fact assessment of the adequacy of those practices. Monitoring is, therefore, of greatest value in connection with the maintenance of animals in isolation systems where vigorous microbiological control is applied. In addition to constructive measures, an appropriate management system is necessary for the prevention of infections, as well as for their detection and control. It is a major task for the management of an animal facility to understand the way micro-organisms might be introduced or spread under the specific conditions given. The management of all animal facilities in an institution is best centralized. This warrants that all information dealing with the purchase of animals, the use of experimental materials and equipment and the performance of animal experiments flows through one office. This reduces the opportunity for the failures of communication. Centralized management can best establish comprehensive monitoring programs to evaluate important risk factors, such as animals and biological materials, before they are introduced into a facility.

Laboratory animal allergy: an update

Allergic reactions are among the most common conditions affecting the health of workers involved in the care and use of research animals. Between 11 and 44% of the individuals working with laboratory animals report work-related allergic symptoms. Of those who become symptomatic, 4 to 22% may eventually develop occupational asthma that can persist even after exposure ceases. Allergic symptoms consist of rashes where animals are in contact with the skin, nasal congestion and sneezing, itchy eyes, and asthma (cough, wheezing, and chest tightness). The generation of immunoglobulin E (IgE) antibodies is a prerequisite for the production of allergic symptoms. The mechanism by which IgE antibodies develop is becoming clearer. The propensity to produce IgE is genetically determined, and pre-existing allergy may be a risk factor for the development of laboratory animal allergy (LAA). However, exposure to animal allergens is the major risk factor for the development of LAA. Techniques to measure the airborne concentration of laboratory animal allergens have been developed. Research on animal allergens themselves indicates that many of the mouse and rat urinary proteins belong to a family of proteins called lipocalins, which share sequence homology with antigens of the parasitic agent that causes schistosomiasis. The fact that parasite infections also trigger IgE antibody responses may account for the development of LAA in persons who have never had any previous allergy. The prevention of LAA should be a major goal of an effective health and safety program in the animal research facility, and it can be accomplished by education and training of employees, reduction of exposure (including the use of personal protective gear), and changes in facility design. Medical surveillance programs can also play a role in improving health of individuals working with laboratory research animals. Early recognition of symptoms and evidence of sensitization can lead to interventions to reduce exposure and thereby avoid the long-term health consequences of LAA.

Occupational asthma

Occupational asthma is a common yet all too frequently unnoticed form of adult asthma. Many agents can trigger disease by a variety of mechanisms, some of which are unknown. Awareness of high-risk occupations and knowledge that adults with persistent asthma may have an occupational trigger are vital in early identification and treatment of this population of patients where the stakes are high. Although the sensitivity and specificity of various tests are low, a multidimensional approach, which includes the cooperation of primary care physician, allergist-immunologist, pulmonologist, industrial hygienist, occupational medicine specialist, and industry (union and management), can lead to a successful outcome in a timely manner.

Rodent allergens

Rodent allergens play a significant role in the pathogenesis of asthma and allergic rhinitis, and are potent causes of acute and chronic symptoms. This has long been apparent in occupational settings, particularly in the laboratory, but has been most recently studied and found to be important in home environments. These allergens have been suggested as uniquely important among inner-city children with asthma. Furthermore, rodents have become increasingly popular as pets. With recent awareness of significant exposure in a variety of settings, hypersensitivity to rodents has become increasingly important. This review focuses on the importance of rodent allergens, concentrating on mouse and rat, but including other potentially important rodents such as gerbil, hamster, and rabbit. It also discusses the pathogenesis, diagnosis, prevention, and management of rodent allergy.