Avian-associated Aspergillus fumigatus displays broad phylogenetic distribution, no evidence for host specificity, and multiple genotypes within epizootic events

Abstract

Birds are highly susceptible to aspergillosis, which can manifest as a primary infection in both domestic and wild birds. Aspergillosis in wild birds causes mortalities ranging in scale from single animals to large-scale epizootic events. However, pathogenicity factors associated with aspergillosis in wild birds have not been examined. Specifically, it is unknown whether wild bird-infecting strains are host-adapted (i.e. phylogenetically related). Similarly, it is unknown whether epizootics are driven by contact with clonal strains that possess unique pathogenic or virulence properties, or by distinct and equally pathogenic strains. Here, we use a diverse collection of Aspergillus fumigatus isolates taken from aspergillosis-associated avian carcasses, representing 24 bird species from a wide geographic range, and representing individual bird mortalities as well as epizootic events. These isolates were sequenced and analyzed along with 130 phylogenetically diverse human clinical isolates to investigate the genetic diversity and phylogenetic placement of avian associated A. fumigatus, the geographic and host distribution of avian isolates, evidence for clonal outbreaks among wild birds, and the frequency of azole resistance in avian isolates. We found that avian isolates were phylogenetically diverse, with no clear distinction from human clinical isolates, and no sign of host or geographic specificity. Avian isolates from the same epizootic events were diverse and phylogenetically distant, suggesting that avian aspergillosis is not contagious among wild birds and that outbreaks are likely driven by environmental spore loads or host co-morbidities. Finally, all avian isolates were susceptible to Voriconazole and none contained the canonical azole resistance gene variants.

The pan-genome of Aspergillus fumigatus provides a high-resolution view of its population structure revealing high levels of lineage-specific diversity driven by recombination

“…In addition to its importance as a pathogen of humans and other animals [22][23][24], A. fumigatus is an ubiquitous plant litter saprophyte and plays a substantial ecological role in carbon and nutrient cycling, enabled by the wide range of carbohydrate-active enzymes encoded in the genome and involved in the decay of organic matter [2,25]. The fungus primarily reproduces asexually, via the production of prolific, stress-resistant, hydrophobic conidia [26].…”

A single fungal strain was the unexpected cause of a mass aspergillosis outbreak in the world’s largest and only flightless parrot

“…This is counter to findings that avian epizootic events are typically driven by diverse strains. 28 Importantly, the only historical isolate from Whenua Hou (collected from a kakapo in 2012) is more closely related to mainland New Zealand isolates than the outbreak strain. This result suggests the outbreak strain is not simply the only A. fumigatus lineage historically present on Whenua Hou.…”

Important Mycoses of Wildlife: Emphasis on Etiology, Epidemiology, Diagnosis, and Pathology—A Review: PART 1

“…The predisposing factors to aspergillosis include a high concentration of Aspergillus spores in the environment, humidity, poor ventilation [ 21 , 22 ], poor sanitation [ 23 ], and the prolonged storage of feed [ 17 , 24 ], which may increase the number of spores in the air. Factors including impaired immunity, an inadequate diet, metabolic bone diseases, toxicosis, shipping, quarantine or captivity, overcrowding, starvation, thermal discomfort, and animal migration can also result in a predisposition to mycosis [ 17 , 25 , 26 , 27 , 28 , 29 , 30 ]. Aspergillus fumigatus has been identified in wild boars in Bulgaria [ 31 ] and other Aspergillus species have also been reported in female killer whales ( Orcinus orca ) [ 32 ].…”