Psittacid Adenovirus-2 infection in the critically endangered orange-bellied parrot (Neophema chrysogastor): A key threatening process or an example of a host-adapted virus?

Abstract

Psittacid Adenovirus-2 (PsAdv-2) was identified in captive orange-bellied parrots (Neophema chrysogastor) during a multifactorial cluster of mortalities at the Adelaide Zoo, South Australia, and an outbreak of Pseudomonas aeruginosa septicaemia at the Tasmanian Department of Primary Industries, Parks, Water and Environment captive breeding facility, Taroona, Tasmania. This was the first time that an adenovirus had been identified in orange-bellied parrots and is the first report of PsAdv-2 in Australia. To investigate the status of PsAdv-2 in the captive population of orange-bellied parrots, 102 healthy birds from five breeding facilities were examined for the presence of PsAdv-2 DNA in droppings and/or cloacal swabs using a nested polymerase chain reaction assay. Additionally, eight birds released to the wild for the 2016 breeding season were similarly tested when they were recaptured prior to migration to be held in captivity for the winter. PsAdv-2 was identified in all breeding facilities as well as the birds recaptured from the wild. Prevalence of shedding ranged from 29.7 to 76.5%, demonstrating that PsAdv-2 is endemic in the captive population of orange-bellied parrots and that wild parrots may have been exposed to the virus. PsAdv-2 DNA was detected in both cloacal swabs and faeces of the orange-bellied parrots, but testing both samples from the same birds suggested that testing faeces would be more sensitive than cloacal swabs. PsAdv-2 was not found in other psittacine species housed in nearby aviaries at the Adelaide Zoo. The source of the infection in the orange-bellied parrots remains undetermined. In this study, PsAdv-2 prevalence of shedding was higher in adult birds as compared to birds less than one year old. Preliminary data also suggested a correlation between adenovirus shedding prevalence within the breeding collection and chick survival.

Fig 1. Map demonstrating the locations of the captive breeding sites (Adelaide Zoo, Healesville Sanctuary, Moonlit Sanctuary, Werribee Open Range Zoo, Priam Parrot Breeding Centre, and Taroona breeding facility) and the remaining breeding location (Melaleuca, Tasmania) of the wild orange-bellied parrots.

Fig 2. Light microscopic image of haematoxylin and eosin stained kidney tissue from an orange-bellied parrot that died at the Adelaide Zoo with aspergillosis and a Psittacid Adeonvirus-2 infection.

Characteristic adenovirus associated intra-nuclear inclusion bodies (Arrows) are shown in renal collecting duct epithelial cells.

Fig 3. Linear regression model of the correlations between adenovirus prevalence and reproductive success of the orange-bellied parrots (Neophema chrysogaster) during the 2016–17 breeding season.

(H: Healesville Sanctuary, A: Adelaide Zoo, M: Moonlit Sanctuary, P: Priam Parrot Breeding Centre).