The Science and Pervasiveness of Laboratory Animal Allergy

A llergic reactions to animals are among the most common conditions that adversely affect the health of workers involved in the care and use of animals in research (NRC 1997). Of the 90,000 laboratory animal workers in the United States (Bland et al. 1987), up to 46% develop allergy to laboratory animals. Of those who develop symptoms, more than 10% eventually develop occupationrelated asthma with symptoms that persist even after exposure ceases. A rare but life-threatening consequence of laboratory animal allergy (LAA1) is an anaphylactic reaction to animal bites, scratches, and needle sticks carrying the animal proteins. The manifestations of animal allergy, which range from rhinitis and itchy eyes to respiratory distress, have caused more than one third of laboratory animal workers at the National Institutes of Health to lose time from work (Bland et al. 1986). Occupational allergy to animals is clearly an important and pervasive condition that affects workers in many countries of the world. Although first reported many years ago, LAA continues to be an important health problem for animal workers and an administrative and financial burden on research institutions due to lost productivity and health care costs. Although much is known about the etiology and prevention of LAA, there is much that is yet to be learned. Contributors to this ILAR Journal issue discuss many of the key issues of LAA and review what is known from the literature and what is yet to be determined. The development of LAA commonly begins with the inhalation of allergens, such as animal dander and urinary proteins, into the lungs. If these allergens stimulate the development of immunoglobulin E (IgE1) antibodies, a cascade of events may follow. Antigen-presenting cells capture the antigen and stimulate complex T-cell replication and the production of cytokines leading to the well-known histamine response of allergy. An important variable in this equation is atopy, which is a genetic predisposition for production of IgE antibodies and the cascading events that lead to allergy. Once allergen-specific IgE antibodies are present, subsequent exposure to the allergen leads to an immediate response. It is thought that the intensity of the allergic reaction depends on the duration and intensity of exposure. Other risk factors for development of LAA are less certain. In the article titled Mechanism and Epidemiology of Laboratory Animal Allergy, Bush (2001b) discusses the role of coexisting allergies and tobacco smoking and provides a clear account of the mechanisms and epidemiology of LAA. One might be able to initiate a good and effective LAA program while knowing little about the nature of the allergens involved. However, an understanding of the lipocalin group of small extracellular proteins that constitute animal allergens is revealing and provides important insights into their control. Wood’s article, Laboratory Animal Allergens, provides a succinct and interesting review of this speciesspecific microcosm (Wood 2001). We generally think of rats and mice only in regard to allergen control; however, we make that association only because they are the most common laboratory animals and not necessarily because other species are less allergenic. All species, and employees who work with them, should be included in the allergy control program. We learn a great deal from this chapter about the science of allergy. For example, cats have 12 allergenic proteins and the most common one, Fel d 1, has been cloned and its amino acid sequence identified. Unfortunately, little is known about its biological function. Clearly, administrators, supervisors, and employees alike will benefit from an understanding of the nature and distribution of animal allergens. The objective of responsible LAA programs is to control exposure to animal antigens in an effort to reduce the incidence of LAA and relieve the symptoms of sensitive employees. Exposure control begins with recognition of the sources of causative antigens and the species most apt to shed them. Most animals shed allergens through urine, dander, hair, serum, and saliva, but not all species or strains do so equally, and, in general, females shed fewer allergens. Allergen exposure is also related to the size of the allergen particle and environmental conditions in the cage as well as the type of bedding, job responsibility, and duration and magnitude of exposure. To address each of these issues in a Thomas K. Wolfle, D.V.M., Ph.D., is a former Director of ILAR. Robert K. Bush, M.D., is Chief of the Allergy Section of the William S. Middle Veterans Affairs Hospital in Madison, Wisconsin, and Professor of Medicine, University of Wisconsin, Madison.