A Novel Psittacine Adenovirus Identified During an Outbreak of Avian Chlamydiosis and Human Psittacosis: Zoonosis Associated with Virus-Bacterium Coinfection in Birds

Abstract

Chlamydophila psittaci is found worldwide, but is particularly common among psittacine birds in tropical and subtropical regions. While investigating a human psittacosis outbreak that was associated with avian chlamydiosis in Hong Kong, we identified a novel adenovirus in epidemiologically linked Mealy Parrots, which was not present in healthy birds unrelated to the outbreak or in other animals. The novel adenovirus (tentatively named Psittacine adenovirus HKU1) was most closely related to Duck adenovirus A in the Atadenovirus genus. Sequencing showed that the Psittacine adenovirus HKU1 genome consists of 31,735 nucleotides. Comparative genome analysis showed that the Psittacine adenovirus HKU1 genome contains 23 open reading frames (ORFs) with sequence similarity to known adenoviral genes, and six additional ORFs at the 3′ end of the genome. Similar to Duck adenovirus A, the novel adenovirus lacks LH1, LH2 and LH3, which distinguishes it from other viruses in the Atadenovirus genus. Notably, fiber-2 protein, which is present in Aviadenovirus but not Atadenovirus, is also present in Psittacine adenovirus HKU1. Psittacine adenovirus HKU1 had pairwise amino acid sequence identities of 50.3–54.0% for the DNA polymerase, 64.6–70.7% for the penton protein, and 66.1–74.0% for the hexon protein with other Atadenovirus. The C. psittaci bacterial load was positively correlated with adenovirus viral load in the lung. Immunostaining for fiber protein expression was positive in lung and liver tissue cells of affected parrots, confirming active viral replication. No other viruses were found. This is the first documentation of an adenovirus-C. psittaci co-infection in an avian species that was associated with a human outbreak of psittacosis. Viral-bacterial co-infection often increases disease severity in both humans and animals. The role of viral-bacterial co-infection in animal-to-human transmission of infectious agents has not received sufficient attention and should be emphasized in the investigation of disease outbreaks in human and animals.

Assessment of Chlamydia psittaci Shedding and Environmental Contamination as Potential Sources of Worker Exposure throughout the Mule Duck Breeding Process

“…It is probable that some interventions may induce more stress for birds and lead to heavier shedding, but this cannot explain all the differences in the prevalence or the excretion level in birds and other factors, such as the "outdoor" factor, that seem to critically impact shedding ( Table 1). As has been previously reported, the presence of coinfections could exacerbate chlamydial shedding (27)(28)(29)(30). Unlike the cases described in these latter studies, it is interesting that the herpesvirus infection that emerged in flock A2 (resulting in premature slaughtering) did not increase the level of C. psittaci shedding from ducks, which therefore had the same shedding pattern as those of flock A1.…”

Genome analysis of four Old World monkey adenoviruses supports the proposed species classification of primate adenoviruses and reveals signs of possible homologous recombination

“…2) (Alonso-Padilla et al, 2016;Pantó et al, 2015). Besides mastadenoviruses, the presence of two fibre genes has also been found in many representatives of different aviadenovirus species (Kaj an et al, 2010(Kaj an et al, , 2012Marek et al, 2014a, b;Zhao et al, 2015), but only in two members of the genus Atadenovirus (P enzes et al, 2014; To et al, 2014). The G+C content, an important AdV species demarcation criterion (Harrach, 2014) among SAdVs, varies between 47.8 (SAdV-20) and 65.7 % (SAdV strain A1139; Roy et al, 2012).…”

Cross-species transmission and emergence of novel viruses from birds

“…Recently, the novel concept of 'pathogen augmentation' was introduced and brought insights into the significance of avian viruses in cross-species transmission of pathogens. A novel adenovirus was detected in Mealy Parrots during an outbreak of avian chlamydiosis and human psittacosis amongst epidemiologically linked workers in an animal detention center in Hong Kong [38 ]. This novel psittacine adenovirus was detected only in the lung, kidney, liver, spleen and cloacal swabs of birds with Chlamydophila psittaci but not in other healthy birds.…”