Canary fancier's lung

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis (HP) is a complex syndrome caused by the inhalation of a variety of antigens in susceptible and sensitized individuals. These antigens are found in the environment, mostly derived from bird proteins and fungi. The prevalence and incidence of HP vary widely depending on the intensity of exposure, the geographical area and the local climate. Immunopathologically, HP is characterized by an exaggerated humoral and cellular immune response affecting the small airways and lung parenchyma. A complex interplay of genetic, host and environmental factors underlies the development and progression of HP. HP can be classified into acute, chronic non-fibrotic and chronic fibrotic forms. Acute HP results from intermittent, high-level exposure to the inducing antigen, usually within a few hours of exposure, whereas chronic HP mostly originates from long-term, low-level exposure (usually to birds or moulds in the home), is not easy to define in terms of time, and may occur within weeks, months or even years of exposure. Some patients with fibrotic HP may evolve to a progressive phenotype, even with complete exposure avoidance. Diagnosis is based on an accurate exposure history, clinical presentation, characteristic high-resolution CT findings, specific IgG antibodies to the offending antigen, bronchoalveolar lavage and pathological features. Complete antigen avoidance is the mainstay of treatment. The pharmacotherapy of chronic HP consists of immunosuppressive drugs such as corticosteroids, with antifibrotic therapy being a potential therapy for patients with progressive disease.

Diagnostic accuracy and safety of inhalation challenge tests for bird fancier's lung-Systematic review and meta-analysis

OBJECTIVE

To assess the diagnostic accuracy of inhalation challenge tests for bird fancier's lung and related adverse reactions.

DESIGN

We performed a systematic review and meta-analysis for the diagnostic test accuracy of inhalation challenge tests and a systematic review for adverse events of the tests. We evaluated the risk of bias and applicability of the included articles for diagnostic test accuracy with the modified Quality Assessment of Diagnostic Accuracy Studies-2 tool. We used hierarchical summary receiver operating characteristic (HSROC) curve analysis to evaluate the sensitivity and specificity of challenge tests and assessed subjective adverse reactions and steroid treatment use. Sensitivity was calculated by fixing specificity at 99% from the HSROC curve.

DATA SOURCES

We searched for articles evaluating the diagnostic accuracy of inhalation challenge tests or describing adverse reactions in Medline, Embase, the Cochrane Library, the International Clinical Trials Registry Platform, and Web of Science.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

We included randomized control trials, prospective or retrospective cohort studies, or case-control studies assessing the diagnostic test accuracy of inhalation challenge tests for bird fancier's lung. For adverse effects review, we included the same articles, and case series or case reports reporting adverse reactions of inhalation challenge tests.

RESULTS

In our review of 12 articles, the diagnostic accuracy of inhalation challenge tests was substantially high. Point estimate of sensitivity when calculated with a fixed specificity of 99% was 99%. Among 873 patients, 6 needed steroid treatment for adverse reactions; however, no death occurred due to acute exacerbation following a challenge test.

CONCLUSIONS

Inhalation challenges for bird fancier's lung could be accurate and safe diagnostic procedures and may be considered both as rule-in and rule-out tests in tertiary care centres. However, caution is required regarding overestimation of diagnostic yield due to risk of bias. Systematic review registration: University hospital Medical Information Network Clinical Trials Registry (UMIN000038799).

Allergy to uncommon pets: new allergies but the same allergens

The prevalence of exotic pet allergies has been increasing over the last decade. Years ago, the main allergy-causing domestic animals were dogs and cats, although nowadays there is an increasing number of allergic diseases related to insects, rodents, amphibians, fish, and birds, among others. The current socio-economic situation, in which more and more people have to live in small apartments, might be related to this tendency. The main allergic symptoms related to exotic pets are the same as those described for dog and cat allergy: respiratory symptoms. Animal allergens are therefore, important sensitizing agents and an important risk factor for asthma. There are three main protein families implicated in these allergies, which are the lipocalin superfamily, serum albumin family, and secretoglobin superfamily. Detailed knowledge of the characteristics of allergens is crucial to improvement treatment of uncommon-pet allergies.

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.

Hypersensitivity pneumonitis

Hypersensitivity pneumonitis or extrinsic allergic alveolitis is an immunologically mediated lung disease caused by repeated inhalations of organic antigens. The basic histologic lesion consists of a diffuse mononuclear cell infiltration of alveolar wall, alveoli, terminal bronchioles, and neighboring interstitium. The inflammation is often followed by granulomas, which then may progress to fibrosis. Although there is no single radiologic, physiologic, or immunologic test specific for hypersensitivity pneumonitis, the diagnosis can often be suspected on the basis of a compatible temporal relationship of pulmonary symptoms to the history of environmental or occupational exposure. Once the diagnosis is suspected, the presence of serum precipitating antibodies (IgG), suppressor cytotoxic lymphocytosis in bronchoalveolar lavage fluid, and granulomatous alveolitis in lung biopsy specimens are extremely helpful in confirming the diagnosis. In patients where the diagnosis is confirmed, avoidance of the causative antigen is the best therapy, although corticosteroids are used to suppress inflammation. Once the fibrosis is set in, the patient may gradually slide into respiratory failure, cor pulmonale, and death.