Volume 27 No. 5 2012 basophils. Since mast cells and basophils are his issue of the BRL Bulletin will discuss T abundant in the skin, conjunctiva, respiratory allergies due to exposure to laboratory animals. tract, and gastrointestinal tract, these areas are Laboratory animal allergy (LAA) is the most the sites for allergic reactions. In these areas, it is common medical condition that affects individuals the histamine released by the mast cells and who work with animals in the research basophils that causes the symptoms commonly environment. It has been estimated that 11 to 44% seen in allergic individuals, including constriction of individuals who work with laboratory animals will of airways, tissue edema, increased mucus develop an allergic condition to these animals. Of secretion, itching, and sneezing. Once a person those who develop allergies, four to 22% will is sensitized to an allergen, he/she will develop eventually develop occupation-related asthma, a allergic symptoms within 10-15 minutes of serious, life-long respiratory disease. In other subsequent exposure to that allergen. In addition words, more than one out of ten people who work to this early phase reaction, approximately half of with laboratory animals will develop allergic allergic individuals will also develop a late phase symptoms and of these individuals, at least one reaction three to four hours following exposure to out of twenty will develop asthma. It has been the allergen. This reaction typically reaches its reported that the prevalence of asthma maximum intensity four to eight hours following subsequent to LAA might be decreasing because exposure, and resolves after 12 to 14 hours. of reduced allergen exposure. However, due to the Symptoms experienced during the early and late high prevalence of LAA in the laboratory reactions are similar; however, an individual may environment, this Bulletin will discuss various not realize that the allergic symptoms he/she has aspects of this condition, including how allergies outside the work environment are directly related develop, symptoms, associated risk factors, to exposure to allergens at work. Although the animals involved, and methods to minimize symptoms are similar, the late reaction can lead exposure. to more severe problems due to the entry of inflammatory cells into the tissues. Over time and How Do Allergies Develop? continued exposure to the allergen, a chronic There are two steps involved in the development inflammatory condition such as asthma may of allergies. First, the person must become develop. sensitized to the substance that causes the allergy (allergen). With animals, these substances are Symptoms of LAA often found in the dander, hair, urine, saliva, or As discussed above, histamine and the blood. During the sensitization process, the production of an inflammatory response cause allergen is inhaled into the lungs where it is allergic symptoms in the target areas of the body. presented to T-cells. These activated T-cells The majority of individuals who become stimulate B-cells to produce specific IgE antibodies sensitized develop symptoms of LAA within three against the allergen. The IgE antibodies bind to years of initial exposure to laboratory animals, of mast cells and basophils, which are found in high which one-third develop allergies within the first concentrations in certain areas of the body. Once year. Although most sensitized individuals the IgE antibodies bind to these cells, the person is develop symptoms of LAA within three years, sensitized to the allergen. During the second step, certain individuals may develop allergies several the sensitized individual is exposed to the allergen years after initial exposure. The most common again. The allergen binds to the IgE antibodies sites for an allergic response are the nasal which causes the release of histamine and other passages and the eyes. Common nasal inflammatory mediators from the mast cells and symptoms are congestion, sneezing, nasal Page 2 BRL BULLETIN drainage, and itching, which collectively are increased risk for the development of LAA. Some termed allergic rhinitis. The common ocular people also have atopy, which is a genetic symptom is watery, itchy, red eyes, which is called predisposition to develop IgE antibodies. allergic conjunctivitis. In individuals who have Individuals who have a family history of allergies allergic reactions in the skin, common symptoms are likely to have atopy, which is another risk are redness, itching, rashes, welts, and hives. This factor. Finally, some suggest that smoking is a combination of symptoms is collectively termed risk factor, as the development of allergies and contact urticaria. Skin allergies usually appear asthma is potentially more likely to occur in a after the allergen has come into contact with the respiratory system damaged through the effects exposed skin of the allergic person. Some allergic of smoking. individuals may develop a more serious manifestation of allergies known as asthma. Animals and their Allergens Symptoms of asthma include coughing, wheezing, It is important to remember that any animal can tightness in the chest, and shortness of breath. potentially cause an allergic reaction. Most Due to the chronic changes to the lungs that take people associate LAA with certain animals such place in asthmatic individuals, the symptoms often as mice and rats. Since mice and rats are the persist for several hours after exposure to the most commonly used animals in biomedical allergen. Sometimes, a severe generalized allergic research, they are implicated in most cases of reaction known as anaphylaxis may occur. LAA. However, mice and rats are no more Although extremely rare, an anaphylactic reaction allergenic than any other animal in the laboratory can occur following a bite or puncture wound with environment. In fact, multiple allergens produced a needle or other sharp object contaminated with in multiple tissues have been identified from most allergens. The symptoms can range from of the commonly used animals. Most of the generalized itching and hives to life threatening allergens produced by animals are very small, so swelling of the larynx and airways and shock. they remain suspended in the air for long periods Other symptoms of an anaphylactic reaction of time and can penetrate deep into the airways. include flushing of the skin, swelling of the lips and For this reason, they are easily inhaled into the eyes, difficulty swallowing, dizziness, fainting, respiratory system when a person enters a room nausea, and diarrhea. Rhinoconjunctivitis is the housing animals. In mice, there are three most common expression of LAA (53-100% of allergens that have been identified. The major people with LAA symptoms) with contact urticaria allergen is a protein found in the urine as well as and asthma second (13-70% and 13-71%, in the hair follicles and dander called Mus m 1 or respectively). More than 60% of persons with LAA mouse urinary protein (MUP), which exists in (and almost all asthma cases) have specific IgE multiple isoforms. Male mice produce up to four antibodies to animal allergens. Not all people with times more of this allergen because its LAA symptoms have specific IgE antibodies to expression is dependent on testosterone. The animal allergens, which suggests that LAA-type other two mouse allergens are found in hair and symptoms might also result from reactions to other dander (Mus m 2), and albumin, which is a environmental agents such as dust, disinfectants, protein found in the blood. The three main rat formaldehyde, or ammonia. allergens are found in the urine (Rat n 1.01 and Rat n 1.02, also found in exocrine glands) and Risk Factors serum (rat albumin), with other allergens The most important risk factor for the development occurring in the saliva and fur. Like mice, male of LAA is the level of exposure to animal allergens. rats produce greater amounts of allergens than Certain tasks such as changing cages and females and rat albumin has the ability to cause handling animals cause the individual to be an allergic reaction in some individuals. Three exposed to high levels of allergens, which may allergens have been identified from the urine, hasten the onset of allergic symptoms. Although hair, saliva and dander of guinea pigs (Cav p 1, some controversy exists, most studies indicate that Cav p 2, and Cav p 3). Rabbits have two main individuals with allergies to substances outside the allergens found in their saliva and fur (Ory c 1) workplace (i.e. pollen, ragweed, and pets) have an and saliva, fur and urine (Ory c 2), along with Page 3 BRL BULLETIN others that have not been fully characterized. One ventilated cage. Ventilated hoods, the laminar air of these allergens is found in the saliva, hair, and flow cabin in particular, also greatly reduce the dander, and the other is found in the hair, dander, amount of rodent allergens in the breathing zone and urine. There are 10 cat allergens that have by at least 90-95%. The method used to clean in been identified, although only one allergen (Fel d the animal facility can either increase or decrease 1) has been implicated in most allergic reactions. the amount of allergen suspended in the air. Dry This protein is produced in the sebaceous glands sweeping and vacuuming both re-suspend of the skin and is secreted onto the skin and hair. It allergens that have settled on surfaces. If a is also produced in the salivary glands and is vacuum is used, it should have a HEPA filter that secreted into the saliva. Like male mice and rats, will trap allergens and prevent their escape with male cats produce greater quantities of this the exhaust. Wet mopping is a better method of allergen than female cats. Cat albumin can also cleaning because it reduces the level of allergens elicit an allergic response in some individuals.