Respiratory

Figure 7.2. Comparison of symptoms in LAA subjects (%). (Aoyama, K., et al., Br. J. Ind. Med., 1992;

49:41-47. Reproduced with permission.)29

Immunological tests are valuable, as they provide additional confirmatory evidence of the diagnosis. The most widely used tests are skin-prick tests and immunoassay tests for specific IgE in the serum. In skin-prick testing, an extract of allergen is placed on the skin and the underlying skin is then punctured. The skin reaction is then compared with a positive (histamine) and negative control. More than 60 percent of cases of LAA (and almost all asthmatic individuals) will be positive by immunoassay. In cases of asthma with no specific IgE to laboratory animals, the symptoms may be due to reactions to other agents that are present in the working environment, e.g., dust, ammonia, formaldehyde, or disinfectants.50

When occupational asthma is suspected, this is usually confirmed with pulmonary function tests. Animal workers with suspected asthma are invited to record their peak expiratory flow rate every two hours throughout the day. They should continue recording this for at least four weeks and include a period away from work. A difference between the mean peak flow while at work and away from work of greater than 15% is indicative of occupational asthma. An alternative technique is cross-shift spirometry, in which pulmonary function is measured before and after work. A deterioration during the working day is suggestive of an occupational cause. However, this technique is often not practicable and the results may be confounded by the normal diurnal increase in pulmonary function from morning to afternoon. The results may also be confounded in asthmatics with a late-phase bronchoconstriction, which may appear several hours after getting off work. Rarely, pulmonary-challenge testing may be necessary to confirm the diagnosis, but this is a risky technique that is only ever done in designated specialist centers.

Prognosis

The symptoms of rhinoconjunctivitis and urticaria are a nuisance. Unless they are effectively managed, they may make it difficult for the affected persons to continue to work with the animals to which they are allergic. If the affected persons cease to be significantly exposed to the allergen, then symptoms will not reappear. However, subjects who have developed sensitivity to one type of fur animal are at increased risk to develop allergies to others. In a study of 100 subjects diagnosed with occupational asthma and followed up after a mean 5.8 years after ceasing exposure, significantly more subjects had developed symptoms against other animals.51

Continued exposure to allergen may lead to the insidious development of asthma, which is of greater concern. The reduction in pulmonary function may be persistent, even after exposure ends,52 with substantial impact on the LAA sufferer's quality of life.53 Continued exposure may lead to permanent loss of function.

Skin

Figure 7.2. Comparison of symptoms in LAA subjects (%). (Aoyama, K., et al., Br. J. Ind. Med., 1992;

49:41-47. Reproduced with permission.)29

Case Management

The workplace management of LAA should be focused on the reduction of exposure to a clinically insignificant level. The medical management of LAA is generally focused on the relief of symptoms, and is not curative. Successful treatment of symptoms should not be allowed to confound efforts to reduce allergen exposure. The exposure can only be regarded as sufficiently low when the LAA sufferer is free of symptoms in the absence of treatment. The degree of exposure precipitating symptoms in allergic workers varies.54,55

Employers and employees should be aware that a risk of anaphylaxis exists and this may be life-threatening. Arrangements for the immediate treatment of anaphylactic reactions should be in place in all animal facilities.

Any person who develops LAA should be counseled by a knowledgeable physician. The worker's job should be analyzed and control measures reviewed and, if necessary, enhanced, so that exposure is reduced (to the benefit of all exposed workers). The capacity of the individual to reduce the risk, through good personal hygiene, careful use of personal protective equipment, and by performing tasks in less exposure-generating ways should be reemphasized. It may be possible to relocate the worker to a lower-risk area, such as work with isolators or in an area with lower aeroallergen levels,56 or to transfer the worker to an area where a different species is present. However, the risk for a rodent-sensitive worker to develop allergies against other rodents is considerable,22 and if symptoms of LAA persist, then the fitness of the worker to continue any animal work should be reviewed carefully. Redeployment into a different role where key skills can be utilized, such as quality assurance or training, may be necessary.

The necessary reduction of exposure to a clinically insignificant level can usually be achieved by changes in working practices or redeployment away from the relevant animal. Only in the most extreme cases will the affected persons have to leave their employment.

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