Spleno‐enteritis caused by adenovirus in psittacine birds: A pathological study

Captive Psittacine Birds in Ontario, Canada: a 19-Year Retrospective Study of the Causes of Morbidity and Mortality

Psittacines (e.g. parrots, macaws and cockatoos) are common companion animals that are also kept in zoos and private breeding collections. Despite this popularity, long-term, comprehensive studies of diagnostic data from captive psittacines are rare. This study was conducted to assess trends in disease prevalence and to describe causes of morbidity and mortality in psittacines submitted for post-mortem examination to the veterinary hospital and diagnostic laboratory at the University of Guelph, Ontario, Canada. Post-mortem reports of 1,850 psittacines from 1998 to 2017 were assessed and included 110 species from 45 genera. Birds were often diagnosed with infectious disease processes (n = 823; 44.5%), including viral (n = 428; 23.1%), bacterial (n = 284; 15.4%) and fungal (n = 161; 8.7%). Non-infectious disease processes (n = 1,076; 58.2%) were most commonly degenerative (n = 465; 25.1%), metabolic (n = 392; 21.2%) or haemodynamic (n = 270; 14.6%). Exploratory statistical analyses, used to guide further research, revealed significant correlations and associations among disease processes and genera, age categories and sex. This 19-year retrospective study is the first to be conducted in Canada for psittacine birds and provides a broad overview of disease prevalence that can be used as a baseline to inform other studies addressing common and uncommon diseases affecting these birds in the future.

Disease surveillance in wild Victorian cacatuids reveals co-infection with multiple agents and detection of novel avian viruses

Wild birds are known reservoirs of bacterial and viral pathogens, some of which have zoonotic potential. This poses a risk to both avian and human health, since spillover into domestic bird populations may occur. In Victoria, wild-caught cockatoos trapped under licence routinely enter commercial trade. The circovirus Beak and Feather Disease Virus (BFDV), herpesviruses, adenoviruses and Chlamydia psittaci have been identified as significant pathogens of parrots globally, with impacts on both aviculture and the conservation efforts of endangered species. In this study, we describe the results of surveillance for psittacid herpesviruses (PsHVs), psittacine adenovirus (PsAdV), BFDV and C. psittaci in wild cacatuids in Victoria, Australia. Samples were collected from 55 birds of four species, and tested using genus or family-wide polymerase chain reaction methods coupled with sequencing and phylogenetic analyses for detection and identification of known and novel pathogens. There were no clinically observed signs of illness in most of the live birds in this study (96.3%; n = 53). Beak and Feather Disease Virus was detected with a prevalence of 69.6% (95% CI 55.2-80.9). Low prevalences of PsHV (1.81%; 95% CI 0.3-9.6), PsAdV (1.81%; 95% CI 0.3-9.6), and C. psittaci (1.81%; 95% CI 0.3-9.6) was detected. Importantly, a novel avian alphaherpesvirus and a novel avian adenovirus were detected in a little corella (Cacatua sanguinea) co-infected with BFDV and C. psittaci. The presence of multiple potential pathogens detected in a single bird presents an example of the ease with which such infectious agents may enter the pet trade and how novel viruses circulating in wild populations have the potential for transmission into captive birds. Genomic identification of previously undescribed avian viruses is important to further our understanding of their epidemiology, facilitating management of biosecurity aspects of the domestic and international bird trade, and conservation efforts of vulnerable species.

Recognition and partial genome characterization by non-specific DNA amplification and PCR of a new siadenovirus species in a sample originating from Parus major, a great tit

A seemingly novel siadenovirus species was detected by PCR and sequencing in the sample of a great tit (Parus major) found dead in Hungary. Since the genus Siadenovirus has very few known members so far, further study of the virus was intriguing not only from epizootiological but also from taxonomical aspects. The sample, which had been tested in another PCR survey previously, consisted of less than 50 microl of extracted nucleic acid. To ensure sufficient target DNA for an extended study, the viral genome had to be preserved. To this end, the sample was subjected to a novel method of non-specific DNA amplification. Using the amplified DNA as target, different PCR and sequencing strategies were applied with consensus or specific primers for the study of the central genome part of the putative tit adenovirus. The sequence of supposedly one half (13,628 bp) of the genome was determined including eight full genes between the genes of the IVa2 and hexon proteins. The gene content of the viral genome fragment as well as the results of the phylogenetic analyses with different proteins confirmed the discovery of a new species in the genus Siadenovirus. This is the first report on the detection of an adenovirus in great tits. The methods, described in this work, proved suitable for the recovery of nucleic acid samples that contain irreplaceable microbial genomic DNA but are only available in limited quantities.

A novel budgerigar-adenovirus belonging to group II avian adenovirus of Siadenovirus

Five budgerigars in the same breeding facility died or showed ruffled feathers. To determine the cause, five dead or euthanized budgerigars were examined. Splenomegaly was observed at necropsy in all birds examined. Histopathology of the spleen revealed a slight-to-moderate deletion of lymphocytes and increase of macrophages. Concurrent congestions in several tissues such as liver, lung, kidney, and/or brain and basophilic intranuclear inclusion bodies in the epithelial cells of renal tubules were found in all the birds examined. Psittacine adenoviral DNA was detected in the kidney of one of the five budgerigars by PCR. Sequencing and phylogenetic analysis of the hexon gene revealed that the adenovirus gene detected in the budgerigar was derived from an unknown adenovirus belonging to the genus Siadenovirus. Using a new pair of primers based on the obtained sequence, we confirmed the presence of the newly found adenovirus in all five birds. The newly found unknown adenovirus is designated as Budgerigar Adenovirus 1.

Adenovirus of psittacine birds: investigations on isolation and development of a real-time polymerase chain reaction for specific detection

Liver samples of psittacine birds with a histological suspicion of an adenovirus infection, confirmed by electron microscopy examination, were subjected to virus isolation attempts using a heterologous cell culture system and a homologous cell culture system in the form of chicken embryo liver cells and psittacine embryo fibroblasts, respectively. Whereas isolation in chicken embryo liver cells failed, virus was isolated successfully in the psittacine embryo fibroblasts cell culture system. Molecular investigations identified the virus as a specific psittacine adenovirus (PsAdV). Additionally, on the basis of the hexon gene sequence data obtained, a real-time polymerase chain reaction (PCR) for specific detection of PsAdV was developed. To ensure an exclusive hybridization with PsAdV, selected primers were located within the variable L1 region of the hexon gene. Furthermore, the specificity of the real-time PCR was confirmed by investigation of a panel of different avian adenoviruses and unrelated DNA viruses. Using this PCR, the threshold cycle values obtained support the propagation of PsAdV in the homologous cell culture system in comparison with the chicken cell culture system. Moreover, the developed PCR represents a reliable method for specific and sensitive detection of PsAdV in clinical samples.