ModellingAspergillus fumigatusinfections in racing pigeons (Columba livia domestica)

Abstract

In vivo modelling of aspergillosis in birds allows the evaluation of control measures and the study of hostÁ pathogen interactions. In this study the impact of the use of different inoculation routes and immunosuppression on the course of an infection with Aspergillus fumigatus in racing pigeons (Columba livia domestica) was examined. A. fumigatus conidia were inoculated in the thoracic air sac, lung or trachea in immunocompetent or immunosuppressed pigeon squabs. Immunosuppression was induced by three dexamethasone injections before inoculation. Mortality in the A. fumigatus-inoculated groups varied between 1/4 and 4/4. The highest and more acute mortality was seen in immunocompetent pigeons inoculated in the thoracic air sac and in pigeons inoculated in the thoracic air sac or lung after immunosuppression. Pigeons inoculated in the lung or inoculated intratracheally after immunosuppression developed an aspergillosis infection with a slower course of disease and more prominent clinical symptoms. Using microsatellite length polymorphism, it was confirmed that all mycoses were caused by the inoculated strain except for one isolate in a dexamethasone-treated pigeon. In conclusion, inoculation in the lung is selected as the preferred model for chronic aspergillosis in pigeons, and inoculation in the thoracic air sac as the preferred model for acute aspergillosis. The use of immunosuppressed birds seems to be contra-indicated due to the risk of opportunistic infections.

Anatomopathological aspects of avian aspergillosis

“…In determining such widely different forms of the pathology, a key role is played by the typical resistance of the species, since immunodepression is one of the most important infection-inducing factors in all animal species (Singh et al 1991;Deem 2003;Beernaert et al 2008). The ability of a species to respond to the fungal antigens by organising a good and lasting cell-mediated response explains why, even with the same histological kind of lesion, some species respond by increasing the ridge and thickness of the granuloma's capsule, while others produce poorly defined lesions with a very small connective vallum and diffuse forms of cellular exudates.…”

Germination of Aspergillus fumigatus inside avian respiratory macrophages is associated with cytotoxicity

“…The A. fumigatus isolate, K24, used in the in vitro studies, was obtained from a racing pigeon, which died from pulmonary aspergillosis [20]. Five-day-old cultures of this isolate on Sabouraud dextrose agar (CM0041, Oxoid Ltd., Basingstoke, England) were washed with 5 mL of 0.01% Tween 20 in RPMI 1640 to harvest A. fumigatus conidia.…”

Aspergillus fumigatusin Poultry

“…In some surveys, birds were concurrently challenged with A. flavus conidia [80, 101]. The purpose of intratracheal, intrapulmonary, or intra-air sac injections [109] was to induce a primary respiratory disease. These inoculation routes allowed the delivery of consistent numbers of conidia between individual birds [105].…”

“…The protocols consisted of repeated dexamethasone injections (2 to 5 mg/kg) in pigeons [109], chickens (see [113]; data not shown), and turkeys [106]. Genotyping of isolates recovered from internal organs allowed to verify that experimental infection resulted from the inoculated A. fumigatus strain [109]. …”