Veterinary Science - Theses

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    Investigations into pathogens of potential public health and biosecurity significance in Australian native birds
    Amery-Gale, Jemima ( 2016)
    Pathogens of potential public health and/or biosecurity significance in Australian birds were investigated by screening samples collected from 409 birds presented to the Australian Wildlife Health Centre (AWHC) at Zoos Victoria’s Healesville Sanctuary for veterinary care between December 2014 and December 2015. Samples were tested for the presence of Salmonella, Campylobacter, Yersinia, Chlamydia psittaci, avian influenza viruses (AIVs), avian herpesviruses, Beak and feather disease virus (BFDV), avian paramyxoviruses and avian coronaviruses, using a combination of bacterial culture and genus- or family-wide PCR methods coupled with sequencing and phylogenetic analyses for detection and identification of both known and novel microorganisms. A low prevalence of pathogens was detected, with the exception of BFDV, which was detected from 43.8% of 210 birds sampled at post-mortem. BFDV was considered the greatest biosecurity threat to other birds at Healesville Sanctuary, particularly to threatened psittacine species for which the Sanctuary has captive breeding programs, namely the Orange-bellied parrot (Neophema chrysogaster). The findings suggest that BFDV is more common in non-psittacine species than previously recognised, with BFDV DNA being detected from 27.6% of non-psittacine birds tested, even from species with no clear ecological association with psittacines, and without showing any characteristic clinical signs of BFDV infection. BFDV DNA was also detected at 60% prevalence from psittacine birds sampled at post-mortem, in the majority of cases without exhibiting any clinical signs of BFDV infection. These findings suggest that every bird should be considered a potential carrier of BFDV, regardless of species and clinical presentation. Campylobacter spp. were detected at a prevalence of 21.5%, but it was determined that these bacteria exhibit a pattern of avian host-specificity, are part of the normal commensal intestinal flora and are unlikely to pose a significant zoonotic risk. Although Chlamydia psittaci was only detected from 0.67% of the wild birds and 3.64% of the captive birds sampled, its potential to cause outbreaks as well as severe or even fatal psittacosis in humans after zoonotic transmission means C. psittaci presents the most significant public health risk within the AWHC. Yersinia, AIVs and avian coronaviruses were not detected at all amongst Victorian birds. Salmonella was detected at extremely low prevalence, and a single case of Columbid herpesvirus 1 infection was detected from a Powerful owl (Ninox strenua). Three novel viruses were detected: an avian paramyxovirus from a Musk lorikeet (Glossopsitta concinna), and two avian herpesviruses from a Sulphur-crested cockatoo (Cacatua galerita) and a Tawny frogmouth (Podargus strigoides), which have been named Cacatuid herpesvirus 1 and Podargid herpesvirus 1 respectively. The clinical significance of these novel viruses remains undetermined. It is recommended that the AWHC consider the use of a disinfectant that is effective in inactivating the non-enveloped and extremely resistant circoviruses (e.g. Virkon®S, with main ingredient the oxidising agent peroxymonosulphate), to disinfect all exposed surfaces between examinations of all birds. This should also provide sufficient disinfection for control of C. psittaci and other zoonotic pathogens. These recommendations extend to all veterinary clinics and wildlife rehabilitation facilities that care for birds that are susceptible to PBFD.