Allergic Alveolitis

By James M. Harris, BS, DVM, FRSH
Mayfair Veterinary Clinic, Hobart

Allergic alveolitis is a respiratory disease of humans. It is the result of a hypersensitivity to avian antigens. This includes serum, feathers, feather dust, and faecal material. The condition is also called hypersensitivity pneumonitis, bronchiolitis, allergic interstitial pneumonitis, parakeet dander pneumoconiasis, acute psittacokeratopneumoconiosis, and pigeon lung disease. There are acute, subacute, and chronic forms of this disease.

The acute form occurs 4 to 8 hours after exposure to a heavy load of avian antigen, such as cleaning out a chook house. Coughing, difficulty breathing, fever, and chills occur. There are rattling sounds when breathing in, and an increase in white blood cells, especially eosinophils. X-rays of the lungs show changes consistent with allergic response. Attacks subside within 24 hours without treatment. The condition is confirmed by the history of exposure and by a skin test.

The subacute form results from long-term exposure to a moderate antigen load. There is a dry cough and progressive difficulty breathing. An obvious "trigger" exposure is absent. A skin test is diagnostic. At this stage, the lung pathology is steroid responsive. It is vital that all further exposure to avian antigens be prevented. As long as this can be accomplished, the prognosis is good.

The chronic form is manifested by progressive difficulty breathing, non-productive cough, weight loss, and increased breathing sounds. The lungs undergo changes to the tissue accompanied by pulmonary fibrosis. At this stage, the condition is irreversible. Only complete protection from exposure to avian antigens prevents further deterioration. This chronic form is produced from low-dose exposure to avian antigen over a long period of time. A careful history and skin test will confirm the diagnosis. The chronic form is the most common in clients caring for birds.

This disease is often unrecognized in subacute stages because it mimics influenza or a variety of mild respiratory infections. It is not the number of birds kept that is the primary factor in this disease's occurrence, but the sensitivity of the person. A typical history has a two or more year exposure to birds. Allergic alveolitis has been identified in all age groups from 3 years and up. Individuals without symptoms may test positive to avian antigens but never develop the disease. In a survey of Budgie owners in Britain, 8 % tested positive for the disease. The pathology in the lungs is the result of the bodies immune system reacting to bird protein. There is cross reaction to multiple species. Therefore replacing Cockatiels and getting finches will not solve the health problem for the bird fancier. Some humans are so very sensitive to bird protein that eating poultry and/or eggs can cause destruction of the lining of the intestines. People with this disease must be counselled on preventing all bird and poultry exposure.

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