al., 1986). In addition to cattle epithelium, other potential allergens in barns include fungi and mites (Campbell et al., 1989).

From 8 to 19 percent of allergic patients react to horse allergens on intracutaneous testing (Solomon and Matthews, 1988); however, clinical sensitivity is not as frequent. Horse-sensitive patients may react to extracts of mule and donkey allergens as well. Allergy to horses is less common now than it was in the early years of this century, but significant exposure still occurs among agricultural workers, racetrack and stable attendants, and avocational riders. Allergens have been identified in horsehair and horse dandruff (Lowenstein et al., 1976).

Many workers in swine confinement areas experience respiratory symptoms that are not mediated by IgE. It is believed that most of these symptoms are due to the irritant effects of nitrogenous waste products from the animals or to endotoxins from gram-negative organisms in feces. Nevertheless, occupational asthma caused by allergy to pig urine has been reported (Matson et al., 1983).

Wild Animals

Occasionally, veterinarians and zookeepers exposed to wild animals may develop allergies. For example, large cats (lions and tigers) have the Fel d I allergen; in addition, allergy to deer and elk has been reported. Allergenic sources from deer include hair, dander, saliva, serum, and urine (Gillespie et al., 1985). Asthma triggered by exposure to monkeys has been reported in primate centers. The allergenic sources of that condition appear to be hair and dander, and possibly saliva (Petry et al., 1985).

Birds

Positive skin test reactions to feather extracts but not fresh feathers are common, a finding that may be explained by contamination from dust mites. The most common sources of exposure to feathers are pillows, comforters, quilts, down-filled clothing, and feather beds. About 20 percent of budgerigar and canary fanciers with allergic rhinitis and asthma have IgE antibodies to allergens found in extracts of the feathers of these birds (Solomon and Matthews, 1988).

Another avian source of allergens is chickens. About 10 percent of workers in egg-processing plants develop asthma (A. B. Smith et al., 1990). The allergens are aerosolized in liquid form or occasionally as dried airborne egg protein.

Avian proteins may cause hypersensitivity pneumonitis (also called extrinsic allergic alveolitis). Several specific terms are in use, including bird fancier's, breeder's, or handler's lung or pneumonitis. Parakeets, budgerigars,



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