Isolation and identification of Aspergillus spp. from brown kiwi (Apteryx mantelli) nocturnal houses in New Zealand

Abstract

Aspergillosis, a disease caused by infection with Aspergillus spp., is a common cause of death in birds globally and is an irregular cause of mortality of captive kiwi (Apteryx spp.). Aspergillus spp. are often present in rotting plant material, including the litter and nesting material used for kiwi in captivity. The aim of this study was to survey nocturnal kiwi houses in New Zealand to assess the levels of Aspergillus currently present in leaf litter. Samples were received from 11 nocturnal kiwi houses from throughout New Zealand, with one site supplying multiple samples over time. Aspergillus was isolated and quantified by colony counts from litter samples using selective media and incubation temperatures. Isolates were identified to the species level by amplification and sequencing of ITS regions of the ribosomal. Aspergillus spp. were recovered from almost every sample; however, the levels in most kiwi houses were below 1000 colony-forming units (CFU)/g of wet material. The predominant species was Aspergillus fumigatus, with rare occurrences of Aspergillus niger, Aspergillus nidulans, and Aspergillus parasiticus. Only one site had no detectable Aspergillus. The limit of detection was around 50 CFU/g wet material. One site was repeatedly sampled as it had a high loading of A. fumigatus at the start of the survey and had two recent clinical cases of aspergillosis diagnosed in resident kiwi. Environmental loading at this site with Aspergillus spp. reduced but was not eliminated despite changes of the litter. The key finding of our study is that the background levels of Aspergillus spores in kiwi nocturnal houses in New Zealand are low, but occasional exceptions occur and are associated with the onset of aspergillosis in otherwise healthy birds. The predominant Aspergillus species present in the leaf litter was A. fumigatus, but other species were also present. Further research is needed to confirm the optimal management of leaf litter to minimize Aspergillus spore counts. However, in the interim, our recommendations are that leaf litter should be freshly collected from areas of undisturbed forest areas and spread immediately after collection, without interim storage.