Direct or indirect contact with bird allergens frequently causes sensitization. Bird allergens may be major components in house dust.

Allergen Exposure

Geographical distribution

Budgerigar and Parakeet are the common names for a widespread group of small Parrots, native to the Indo-Malayan-Australian region and now the most popular cage birds in the world. Parakeets have long, pointed tails, unlike the chunky Lovebirds with which they are sometimes confused. The wild Budgerigar of Australia is usually green or blue with black and yellow markings; as a cage bird, however, it has been bred in many color varieties.

Environment

Large flocks, sometimes in the tens of thousands, inhabit the open grasslands in central Australia, nesting in the spring and summer in the southern areas of the continent. In most of the world, however, Budgerigars are familiar only as pets.

No allergens from this bird have yet been fully characterised.

Canary and Budgerigar feathers contain IgE-binding antigens that are not present in the corresponding bird sera and droppings (1).

Cross-reactivity between Chicken and other phylogenetically related bird species may be expected, and in Chicken-allergic patients significant IgE titers to Parrot, Budgerigar, Chicken, Pigeon, Goose and Duck have been reported (2-3), even in patients without known exposure (6).

IgE-mediated reactions

Asthma, allergic rhinitis and allergic conjunctivitis may result on exposure to Budgerigars (1, 4).

In a prospective study, 258 adults were investigated for sensitisation against bird antigens (Budgerigar, Canary, Pigeon) using an intracutaneous test. Eighteen of 78 Budgerigar keepers reacted against Budgerigar feathers. Thirty (38%) showed a positive skin reaction with at least 1 of the 3 extracts tested. In non-bird-exposed persons a reaction was found in 18/96 (19%) against Budgerigar and in 24/96 (25%) against at least 1 of the 3 allergen extracts. Late reactions occurred in 5/70 (7%) Budgerigar keepers. The frequency of sensitisation against Budgerigar antigens increased to 48% of bird keepers (24/50) if the birds could fly around in their homes instead of being always caged (4/22, 18%). Three of the 78 Budgerigar keepers (4%) had a positive nasal provocation with feather extract, and they were skin-positive against all 3 bird antigens tested (6).

Extrinsic allergic alveolitis, also known as hypersensitivity pneumonitis, Bird Fancier's Lung and Farmer's Lung, is a disease of inflammation of the lung parenchyma in the terminal bronchioles and alveoli. Symptoms may start soon after exposure to bird allergens or after many years, and may include breathlessness, cough, occasional chills, and fever. Death may also result.

The disease occurs after exposure to organic dust, especially after close contact with Pigeons or other birds such as Budgerigars, Parrots, Canaries, Parakeets, Cockatiels, Doves or Finches. Exposure results in the development of immunoglobulin antibodies including IgE (6),  IgM (7),  IgA and various IgG subclasses (8-10. The antibodies may be found in the sera and saliva of patients (11) as well as in the sera of asymptomatic but exposed subjects (12). 

The allergenic proteins may be found in bird serum, droppings, skin scales, feathers and, in the case of Pigeons, Pigeon bloom (a waxy fine dust which coats the feathers of Pigeons). Contact may result from handling birds, cleaning their lofts, or exposure to the organic dust drifting down from a ceiling or roof where birds nest.

Diagnosis is based on a characteristic clinical picture and a typical x-ray pattern, accompanied by the presence of specific IgG antibodies (13).

The measurement of specific IgG using IgG tracer technology has been shown to be a sensitive and specific assay for the routine diagnostic testing of extrinsic allergic alveolitis (14).

A woman with alveolitis due to her Budgerigar developed recurrent symptoms when exposed to dropping allergens left on her artificial Christmas tree (15).