Clinical Manifestations

Symptoms

Symptoms during work with laboratory animals are mainly, but not exclusively, mediated by mechanisms initiated by the interaction of allergen with specific IgE. Symptoms of LAA arise from the release of biochemical mediators that lead to an inflammatory response. The nature of the symptoms vary from person to person, but form three principal patterns that affect the nose and eyes, chest, and skin.

The most commonly reported symptoms affect the nose and eyes (rhinitis and conjunctivitis). The symptoms include sneezing, nasal congestion and discharge, redness of the conjunctiva, and itching, watery eyes. If the lower airways are affected, then the presenting symptoms are those of asthma, with cough, wheezing, production of sputum, and shortness of breath.

Skin reactions include urticaria, with itching and circumscribed red lesions, and contact dermatitis.33 Typically localized lesions appear quickly on the skin exposed to allergen, such as the face, neck, and arms, but skin reactions can be more generalized.48

Anaphylactic reactions are a rare manifestation of LAA that have been reported in association with both rat and mouse bites2,35 and a puncture wound from a needle used on a rabbit.36 These reactions can lead to generalized itching and urticaria, swelling of the face, lips, and tongue (angioedema), obstruction of the airways, and shock (low blood pressure). The symptoms may vary from mild skin rashes to life-threatening cardiorespiratory reactions.

Pooled data from 13 studies revealed a consistent picture of symptom distribution.3 Of 10 persons with symptoms of LAA, about eight will have rhinoconjunctivitis (range 53 to 100%), about four will have skin reactions (13 to 70%), and about three to four will have asthma (13 to 71%). Subsequent studies of symptom incidence suggests this 2:1:1 ratio of symptoms remains typical.25 29 There is inevitably overlap between symptoms; most subjects have more than one affected target organ, and asthma rarely occurs in the absence of the prior development of rhinoconjunctivitis (see Figure 7.2).29,49

Diagnosis

Strong evidence for LAA is provided by a clear history of symptoms that are associated with work. Where there are immediate symptoms on contact with the relevant animal, then the diagnosis is usually self-evident. However, care must be taken to make sure that it is LAA and not symptoms arising from contact with another allergen found in the animal facility, such as latex from gloves or wood dust from bedding materials.

Workers who have delayed reactions to allergen may only experience symptoms after leaving the animal facility. They may not attribute these symptoms to allergen exposure. When symptoms are those of LAA, a careful history will normally reveal a temporal association with workplace exposure. Symptoms are typically worse at the end of the working week and after periods of intense animal handling, and usually improve during periods away from work, such as weekends and vacations. It is common for persons who care for animals at work to keep pets at home; this should be taken into account when considering the pattern of symptoms during "exposure-free" periods. Health workers will easily recognize the symptoms of allergy, such as the typical rashes, although there may be few findings of allergy on examination in the absence of obvious symptoms.

Coping with Asthma

Coping with Asthma

If you suffer with asthma, you will no doubt be familiar with the uncomfortable sensations as your bronchial tubes begin to narrow and your muscles around them start to tighten. A sticky mucus known as phlegm begins to produce and increase within your bronchial tubes and you begin to wheeze, cough and struggle to breathe.

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