Clinical, mycological and pathological findings in turkeys experimentally infected by Aspergillus fumigatus.

Experimental aspergillosis was induced in 1-day-old turkeys by intra-air-sac inoculation of a spore suspension of a 3-day-old Aspergillus fumigatus culture (CBS 144.89) containing 10(7) spores. Ten additional poults were used as controls. Infected and non-infected animals were closely observed at least twice a day for the appearance of clinical signs and were sequentially sacrificed at days 1, 2, 3, 5 and 7 post-inoculation. In the infected group, most lung tissues and air sac swabs were culture positive from day 1 to day 5. At 1 day post-inoculation, air sac membranes were multifocally and moderately to severely thickened by an oedema and covered by an exudate. A small number of germinating conidia were present in the superficial exudate, already giving rise to small radiating hyphae. Lung lesions were mild, dominated by a diffuse congestion and a mild heterophilic infiltration. From 2 to 3 days post-inoculation, air sac membranes were more severely affected and several granulomas were observed. Both granulomas and exudates were rich in germinated conidia and hyphae. Pulmonary lesions consisted in a diffuse pneumonia. Five days post-inoculation, air sac membrane lesions progressed to a severe, multifocal, heterophilic and granulomatous inflammation. Seven days post-inoculation, a reduction of the severity of the diffuse pneumonia was detected. Concomitantly, the fungal elements were mainly observed as fragmented tubules in the cytoplasm of multinucleate giant cells. The present study demonstrated that healthy turkey poults might be able to withstand exposure to 10(7) A. fumigatus spores.