AVIAN/FUR/EXOTIC SPECIES

Atypical mycotic infection in poultry: Aspergillus oryzae   

Emily Martin, Alex Weisz, Lloyd Weber, Rachel Ouckama

Since November 2015, there have been multiple cases of atypical mycotic infection submitted to the AHL involving

layer and broiler breeder flocks. The flocks had clinical signs of increased mortality and severe runting/stunting.

On gross postmortem examination, there were multifocal to coalescing firm cream nodules throughout the lungs, air sacs, and multiple other organs (Figs.1, 2). These nodules were firm and homogeneous throughout on cut section. On histopathology, these nodules were composed of numerous clusters of multinucleated giant cells surrounding fungal organisms (Fig.3) and occasionally coalesced into larger granulomas (Fig.4). This appearance was quite different from the more common mycotic infections caused by Aspergillus fumigatus that occur as large well developed multifocal to coalescing granulomas. The fungal organisms in these cases affected multiple organs including the lungs, liver, kidney, and brain.

These nodules were forwarded to the AHL Bacteriology Laboratory for mycology, and on wet mounts Aspergillus sp. was identified. These cultures were directed to the AHL Molecular Biology lab section for 18SrRNA sequence analysis. This initial analysis revealed a 99.0% sequence similarity (474/479 bp) to multiple members of family Trichocomaceae (Aspergillus, Penicillium, Eurotium, Neosartorya, Edyuillia spp., etc.) as well as uncultured clones (i.e., Aspergillus flavus, A. fumigatus, A. tamarii, Penicillium javanicum, etc.). For further characterization, the nuclear ribosomal internal transcribed spacer (ITS) region was sequenced and found to have 100% similarity to both A. flavus and A. oryzae. Then the cytochrome c oxidase subunit I (COI) gene was analyzed to attempt to make a final identification of this fungus. The COI partial gene (640 bp) sequence revealed that this fungus had 100% similarity to Aspergillus oryzae (and 90% sequence similarity to Aspergillus flavus).

Aspergillus oryzae, also known as kōji (Japanese), is a filamentous fungus used in Chinese and East Asian cuisines. It is used to ferment soybeans, to make soy sauce, and make fermented bean paste. It is also used to saccharify rice, grains, and potatoes to make alcoholic beverages.

Overall, these were cases of increased mortality and atypical mycotic lesions. The origin of the fungus is not known.