Avian circoviruses of the genus Circovirus: A potential trigger in Pigeon breeder's lung (PBL)/Bird fancier's lung (BFL).

Pigeon breeder's lung (PBL) or Bird fancier's lung (BFL) is one of the most common extrinsic allergic alveolitis or hypersensitivity pneumonitis. It is caused after prolonged inhalation of avian antigens and provokes a hypersensitivity reaction in the lungs of sensitised people. Although the pathogenic mechanism is unclear, the epidemiology of BFL shows that it occurs worldwide, and has been described in adults keeping birds and also in their children. Laboratory findings associated with the disease classified as a type III immunologic reaction that produces blood precipitin antibodies against birds' serum, feathers, intestinal mucin and/or faeces. In particular, the fine dust from pigeon feathers has strong antigenic properties. There is an interaction between host and antigen that seems to be influenced by both genetic and environmental factors. Avian circoviruses (ACV) of the genus Circovirus, has been detected in free-ranging and captive birds worldwide, such as pigeons, canaries, psittacines, Senegal doves, finches, gulls, Australian ravens and geese. T lymphocytes are the main target cells of the ACV and in the above avian species circovirus-like particles were detected in blood, macrophages, feathers, crop secretions, intestinal contents and/or faeces. Most of the ACV was demonstrated that are pantropic and viral antigen in pigeon tissues was most commonly detected in respiratory organs, including the trachea, pharynx and lung. The transmission of the circovirus between the birds usually occurs through inhalation of feathers dust. There is evidence that animal circoviruses may originate when vertebrates become "infected" with DNA from a plant nanovirus. So, it seems that further investigation for the avian circoviruses is needed to determine if they are host specific or not. This study attempts to demonstrate ACV or ACV-like particles as potential triggers in the BFL aetiology, and the possible involvement in BFL's pathogenic mechanism.