Prospective epidemiologic evaluation of laboratory animal allergy among university employees

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.

Occupational asthma: etiologies and risk factors

The purpose of this article is to critically review the available evidence pertaining to occupational, environmental, and individual factors that can affect the development of occupational asthma (OA). Increasing evidence suggests that exploration of the intrinsic characteristics of OA-causing agents and associated structure-activity relationships offers promising avenues for quantifying the sensitizing potential of agents that are introduced in the workplace. The intensity of exposure to sensitizing agents has been identified as the most important environmental risk factor for OA and should remain the cornerstone for primary prevention strategies. The role of other environmental co-factors (e.g., non-respiratory routes of exposure and concomitant exposure to cigarette smoke and other pollutants) remains to be further delineated. There is convincing evidence that atopy is an important individual risk factor for OA induced by high-molecular-weight agents. There is some evidence that genetic factors, such as leukocyte antigen class II alleles, are associated with an increased risk of OA; however, the role of genetic susceptibility factors is likely to be obscured by complex gene-environment interactions. OA, as well as asthma in general, is a complex disease that results from multiple interactions between environmental factors and host susceptibilities. Determining these interactions is a crucial step towards implementing optimal prevention policies.

Work-related sensitization and respiratory symptoms in carpentry apprentices exposed to wood dust and diisocyanates

BACKGROUND

Exposure to certain substances in the workplace may lead to sensitization and increased respiratory symptoms.

OBJECTIVE

To evaluate the frequency of work-related specific sensitization and respiratory symptoms in carpentry apprentices with occupational exposure to wood dust and diisocyanates.

METHODS

Apprentices (n=101) completed an occupational and symptoms questionnaire. Spirometry and skin prick tests to aeroallergens and to a battery of 14 different woods were performed in all the participants. Blood samples were collected for total IgE measurement and detection of specific IgE to diisocyanates.

RESULTS

Half the participants (56%) had work-related respiratory symptoms: 54% due to wood dust, 15% due diisocyanates, and 9% to both. Participants with respiratory symptoms related to wood dust exposure had a significantly lower forced expiratory volume in 1 second compared with symptomatic individuals due to diisocyanates and asymptomatic individuals (P < .05). A history of rhinitis or asthma was associated with a 2.1- or 2.8-fold increase, respectively, in the likelihood of having respiratory symptoms due to wood dust exposure. Sensitization to wood was detected in 9% of participants, all of whom were atopic with a history of rhinitis and a high total IgE level (P < .05). Sensitization to diisocyanates was detected in 2% of exposed participants.

CONCLUSIONS

Work-related respiratory symptoms are common in carpentry apprentices and are more frequently related to exposure to wood dust than to diisocyanates. Symptomatic participants due to wood dust exposure had a lower forced expiratory volume in 1 second. Individuals with a history of rhinitis or asthma had an increased risk of respiratory symptoms. Sensitization to wood was more common in atopic apprentices with a history of rhinitis and a high total IgE level.

Inverse association between rural environment in infancy and sensitization to rodents in adulthood

BACKGROUND

It is not known whether early childhood exposure to hygiene hypothesis factors modifies the risk of sensitization to aeroallergens among adults. Studying adults exposed to allergens in the workplace may help determine whether childhood exposures confer lasting protection against sensitization.

OBJECTIVE

To determine whether early life exposures influence the prevalence of sensitization to allergens in adulthood.

METHODS

Sensitization to rodents was determined by skin testing in a cross-sectional study among university employees with and without occupational exposure to laboratory animals. Demographic information was obtained by questionnaire.

RESULTS

Of 137 employees, 8% of workers without occupational exposure to laboratory animals and 24% of those with such exposure were sensitized to rodents (P = .007). None of 32 study participants who lived in a rural environment during their first year of life were rodent sensitized vs 18% of those who lived in other settings (P < .01). Rural setting in infancy was also associated with a decreased prevalence of sensitization to outdoor allergens (odds ratio [OR], 0.36; 95% confidence interval [CI], 0.14-0.95). After adjusting for multiple confounders, sensitization to rodents remained rare among individuals who lived in a rural setting during infancy (OR, <0.15). Rodent sensitization was more prevalent among those with higher educational attainment (OR, 9.50; 95% CI, 1.10-82.02) and those sensitized to indoor allergens (OR, 6.22; 95% CI, 1.42-27.24). Sensitization to rodents was not significantly associated with having older siblings or sensitization to outdoor allergens.

CONCLUSIONS

Living in a rural setting during the first year of life is associated with protection from sensitization to rodent allergens in the workplace decades later.

Lung function decline in laboratory animal workers: the role of sensitisation and exposure

BACKGROUND

Little is known about the relation between allergic sensitisation and subsequent long term lung function changes in working populations exposed to sensitising agents.

AIMS

To investigate whether exposure and work related sensitisation to laboratory animals are associated with lung function decline.

METHODS

The relation between exposure and sensitisation to laboratory animal allergens and changes in lung function was investigated in a longitudinal study (median follow up 2.0 years) among 319 laboratory animal workers. Subjects who had been working with laboratory animals for less than 4 years (n = 102) were analysed separately, since an earlier cross sectional analysis had suggested a strong healthy worker effect in more experienced workers.

RESULTS

In multiple regression analyses both sensitisation and exposure appeared to contribute independently to lung function decline in subjects who had been working with laboratory animals for less than 4 years, adjusting for gender, age, smoking, and atopy. Lung function decline was most pronounced in sensitised subjects who continued to be in contact with the animals to which they were sensitised, with estimated average excess declines in FEV1, FVC, and MMEF of 83 ml/y (p < 0.05), 148 ml/y (p < 0.01), and 7 ml/s/y (p = 0.9).

CONCLUSIONS

We conclude that exposure to laboratory animals is a significant risk factor for accelerated lung function decline, and that sensitised workers are especially at risk.

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.

Primary and secondary allergies to laboratory animals

Although laboratory animal allergy (LAA) is a significant occupational hazard among workers exposed to laboratory animals, few studies have evaluated long-term risks to workers who remain in the workplace. This short-term focus has obscured the evaluation of subsequent animal allergies (secondary LAA). We analyzed surveillance data from a 10-year LAA prevention program to estimate incidence rates of primary and secondary LAA and to evaluate the effectiveness of the prevention program in reducing the development of primary LAA. The 10-year incidence rates of primary and secondary LAA were 1.34 (95% CI, 0.78-1.90) and 11 (95% CI, 7.4-14.6) cases per 100 person-years, respectively. The annual incidence of primary LAA was reduced from 3.6% to 0 in the first 5 years and did not rise above 1.2% over the remaining years, whereas the incidence of secondary LAA was greater than 8% in most years. These findings suggest that programs effective at preventing primary LAA may need to be evaluated for their effectiveness at protecting against further risk.

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

BACKGROUND

Laboratory animal allergy is an important occupational disease that is preventable by reduction of exposure to mammalian allergens.

OBJECTIVE

The purpose of this investigation was to assess the efficacy of safety equipment in containing mouse urinary protein (MUP)--specifically, individually ventilated cage (IVC) systems and class I--type and class II ventilated cabinets.

METHODS

Six IVC systems (which are used to house rodents) were operated at positive and negative pressure. Air samples (2 L/min) were collected at the cage front, cage back, air inlet, and air outlet, and the MUP was quantified by immunoassay. The background MUP of the IVC study room was compared with that of rooms where mice were housed conventionally or in isolators. Class I--type cabinets (n = 2) were tested during the disposal of soiled litter. Air samples were positioned on and behind the operator and inside the cabinet (n = 2). Personal samples were collected while scientific procedures were performed in a class II cabinet and in the open.

RESULTS

All of the IVC systems contained MUP effectively (>250-fold) when operated at negative pressure. At positive pressure, the "unsealed" IVC racks leaked MUP (1- to 25-fold reduction) but the "sealed" IVC system did not. Class I--type cabinets reduced (10-fold) but did not eliminate exposure during "cleaning out." No MUP was detected when procedures were performed in class II cabinets (protection factor, >10-fold).

CONCLUSION

Safety equipment can substantially reduce exposure to mouse allergen. Allergen exposure in holding rooms will be minimized if mice are housed in IVC systems operated at negative pressure or in "sealed" IVC systems at positive pressure. Respiratory protection should be used whenever "unsealed" IVC systems are operated at positive pressure or during "cleaning out" in class I--type cabinets.

Mechanism and epidemiology of laboratory animal allergy

Laboratory animal allergy (LAA) is a form of occupational allergic disease. The development of laboratory animal allergy is due to the presence of IgE antibodies directed against animal proteins. The process of sensitization (development of IgE antibodies) is a complex process which involves interaction of antigen presenting cells and lymphocytes of the Th-2 cell type. These cells generate a host of cytokines and other factors which lead to immediate hypersensitivity reactions and other factors which lead to immediate hypersensitivity reactions and the generation of allergic inflammation. Typical symptoms of laboratory animal allergy include nasal symptoms, such as sneezing, watery discharge, and congestion. Skin rashes are also common. Asthma, which produces symptoms of cough, wheezing, and shortness of breath, may affect 20-38% of workers who are sensitized to laboratory animal allergens. Rarely a generalized, life-threatening allergic reaction (anaphylaxis) may occur. The estimated prevalence of laboratory animal allergy is variable depending on the method used for diagnosis, but nonetheless may affect up to 46% of exposed workers. The presence of pre-existing allergies to non-work place allergens (e.g., dust mite, pollens, molds), exposure to laboratory animal allergens, and possibly tobacco smoking are risk factors for the development of laboratory animal allergy. Progress in the understanding of the mechanism and epidemiology of laboratory animal allergy will lead to improved methods for its prevention.

Laboratory animal allergy: a British perspective on a global problem

In the United Kingdom, laboratory animal allergy (LAA) has been recognized as an important occupational disease for nearly 25 years. However, introduction of health and safety legislation (e.g., the Control of Substances Hazardous to Health Regulations of 1988) and an increasing knowledge of the factors that contribute to the etiology of this disease have had surprisingly little impact on the prevalence and incidence of LAA over the last 10 to 20 yr. Studies of the relation between exposure to animal allergens and the development of LAA reveal that the risk of disease increases with increasing intensity of exposure. Current evidence suggests that animal allergens are very potent, and substantial decreases in allergen exposure are therefore necessary before a reduction in symptoms will be observed. In the United Kingdom, it is unlikely that an Occupational Exposure Limit will be set for animal allergens in the near future, partly because an adequately standardized assay for quantifying exposure is not yet available. Prevention of LAA in the future will probably be driven by the needs of the industry and will most likely rely on the adoption of guidelines describing " best practise" which incorporate sophisticated engineering methods of controlling exposure to animal allergens.

Incidence and host determinants of probable occupational asthma in apprentices exposed to laboratory animals

Laboratory animal (LA) workers are frequently affected with allergic sensitization and occupational asthma (OA). The role of preexposure host factors, in particular airway responsiveness, on the incidence of OA has not been satisfactorily studied. A prospective cohort study of 417 apprentices in animal-health technology was conducted to investigate the incidence and determinants of probable OA. Questionnaire and skin-prick tests with common and work-specific allergens were administered on entry and at follow-up visits (up to three) from 8 to 44 mo after starting apprenticeship. Responsiveness to inhaled methacholine was assessed at baseline and at follow-up in apprentices who developed a new specific skin sensitization and in control subjects. Preexposure host characteristics and the school attended were compared between cases and all cohort subjects not meeting the criteria for probable OA. Twenty-eight apprentices satisfied the definition for probable OA, i.e., onset of immediate skin reactivity to > 1 occupational inhalant and > 3.2-fold decrease in the provocative concentration causing a 20% reduction in FEV(1) (PC(20)). The incidence of probable OA was 2.7% (28/1,043 person-years). Baseline immediate skin reactivity to pets (rate ratio [RR] 4.1, 95% confidence interval [CI] = 1.6 to 10.8), and bronchial responsiveness (PC(20) < or = 32 versus PC(20) > 32 mg/ ml) (RR = 2.5, 95% CI = 1.0 to 5.8) were associated with an increased risk of probable OA; a lower FEV(1) had an apparent, protective effect (RR = 0.58, 95% CI = 0.43 to 0.78). It is concluded that apprentices in animal health show a high incidence of probable OA, and that preexposure airway caliber and responsiveness as well as sensitization to pets are associated with an increased risk.