Identification and genetic characterization of polyomaviruses in estrildid and fringillid finches

Canary Bornavirus (Orthobornavirus serini) Infections Are Associated with Clinical Symptoms in Common Canaries (Serinus canaria dom.)

While parrot bornaviruses are accepted as the cause of proventricular dilatation disease (PDD) in psittacine birds, the pathogenic role of bornaviruses in common canaries is still unclear. To answer the question of whether canary bornaviruses (species Orthobornavirus serini) are associated with a PDD-like disease in common canaries (Serinus canaria f. dom.), the clinical data of 201 canary bird patients tested for bornaviruses using RT-PCR assays, were analyzed for the presence of PDD-like gastrointestinal or central nervous system signs and for other viruses (mainly circovirus and polyomavirus), yeasts and trichomonads. Canary bornavirus RNA was detected in the clinical samples of 40 out of 201 canaries (19.9%) coming from 28 of 140 flocks (20%). All nucleotide sequences obtained could unequivocally be determined as canary bornavirus 1, 2, or 3 supporting the current taxonomy of the species Orthobornavirus serini. PDD-like signs were found associated with canary bornavirus detection, and to a lesser extent, with circoviruses detection, but not with the detection of polyomaviruses, yeasts or trichomonads. The data indicate that canary bornaviruses contribute to a PDD-like disease in naturally infected canaries, and suggest a promoting effect of circoviruses for the development of PDD-like signs.

Pathogenicity of Avian Polyomaviruses and Prospect of Vaccine Development

Polyomaviruses are nonenveloped icosahedral viruses with a double-stranded circular DNA containing approximately 5000 bp and 5–6 open reading frames. In contrast to mammalian polyomaviruses (MPVs), avian polyomaviruses (APVs) exhibit high lethality and multipathogenicity, causing severe infections in birds without oncogenicity. APVs are classified into 10 major species: Adélie penguin polyomavirus, budgerigar fledgling disease virus, butcherbird polyomavirus, canary polyomavirus, cormorant polyomavirus, crow polyomavirus, Erythrura gouldiae polyomavirus, finch polyomavirus, goose hemorrhagic polyomavirus, and Hungarian finch polyomavirus under the genus Gammapolyomavirus. This paper briefly reviews the genomic structure and pathogenicity of the 10 species of APV and some of their differences in terms of virulence from MPVs. Each gene’s genomic size, number of amino acid residues encoding each gene, and key biologic functions are discussed. The rationale for APV classification from the Polyomavirdae family and phylogenetic analyses among the 10 APVs are also discussed. The clinical symptoms in birds caused by APV infection are summarized. Finally, the strategies for developing an effective vaccine containing essential epitopes for preventing virus infection in birds are discussed. We hope that more effective and safe vaccines with diverse protection will be developed in the future to solve or alleviate the problems of viral infection.

Mycobacteriosis in Various Pet and Wild Birds from Germany: Pathological Findings, Coinfections, and Characterization of Causative Mycobacteria

A total of 50 birds diagnosed with mycobacteriosis were examined for pathomorphological lesions, coinfections, and causative agents. Mycobacterial species were identified and isolates differentiated using multilocus sequence typing (MLST) and mycobacterial interspersed repetitive-unit variable-number of tandem-repeat (MIRU-VNTR) analysis. Possible associations between mycobacterial species, pathomorphological findings, coinfections, bird orders, and husbandry conditions were evaluated statistically. Mycobacteria were isolated from 34 birds (13 of 22 Psittaciformes, 12 of 18 Passeriformes, five of six Columbiformes, and four other orders) belonging to 26 species in total. Mycobacterium genavense (Mg) was cultured from 15 birds, Mycobacterium avium subsp. avium (Maa) from 20 birds, and Mycobacterium avium subsp. hominissuis (Mah) from three birds; hence, four birds had mixed infections. About equal numbers of psittacines and passerines were infected with Ma and Mg. The genetic diversity differed; Mg isolates belonged to one MLST type, Maa to six, and Mah to three combined genotypes. Several coinfections were detected; viruses and/or endoparasites affected 44%, fungi 38%, and bacteria 29% of the birds. Pathological findings and mycobacteriosis-affected organs were independent of coinfections. Overall, gross pathological findings were more often seen in mycobacteriosis caused by Ma (95%) compared with Mg (66%). Organ distribution of mycobacteriosis was independent of the mycobacterial species. Pathomorphological changes were seen in the small intestine of 71% and the lung of 65% of the birds, suggesting oral or pulmonal ingestion of mycobacteria. There were no associations between mycobacterial species and bird orders or bird husbandry conditions. Not only Mg, but also Maa and Mah, were clearly identified as primary cause of mycobacteriosis in pet birds. IMPORTANCE In this study, the causative agents and confounding factors of mycobacteriosis in a set of pet and some wild birds from Germany were examined. Not only Mycobacterium genavense, but also M. avium subsp. avium and M. avium subsp. hominissuis, contributed to mycobacteriosis in these birds. Various coinfections did not affect the manifestation of mycobacteriosis. Due to different gross necropsy findings, however, a different pathogenicity of the two species was assumed. New strains of M. avium subsp. hominissuis originating from birds were identified and characterized, which is important for epidemiological studies and for understanding the zoonotic role of this pathogen, as the subsp. hominissuis represents an increasing public health concern. The study provides some evidence of correlation between M. avium subsp. avium genotypes and virulence which will have to be confirmed by broader studies.

Molecular identification of novel and genetically diverse adenoviruses in Passeriform birds

Knowledge about adenoviruses in birds of the order Passeriformes is very scarce. Based on molecular characterizations, only two siadenoviruses, great tit adenovirus 1 and Gouldian finch adenovirus, have been described so far occurring in great tits and Gouldian finches, respectively. Assuming a broader occurrence of adenoviruses, various passeriform birds including pet, zoo, and wild birds were examined using a broad-range PCR targeting a fragment of the adenovirus DNA polymerase gene. Adenoviruses were detected in 25 individual birds belonging to 13 species and seven zoological families (Ploceidae, Fringillidae, Estrildidae, Paridae, Sylviidae, Turdidae, Muscicapidae). The putative viruses were further characterized by sequencing the PCR products and phylogenetic analyses. DNA of adenoviruses affiliating to 3 genera including aviadenovirus, siadenovirus, and atadenovirus was found. Viruses with sequences identical or closely related to great tit adenovirus 1 and Gouldian finch adenovirus 1 were detected in a great tit and in two zebra finches, respectively. Based on polymerase amino acid sequence comparisons, the viruses found in the remaining 22 birds revealed phylogenetic distances larger than 15% to adenoviruses known so far suggesting that they may belong to at least 14 different virus species. In some bird species (great tit, zebra finch, vitelline masked weaver) varying adenovirus genera were detected. These results suggest a broad variety of adenoviruses circulating in passeriform birds.

Isolation and characterization of an Aves polyomavirus 1 from diseased budgerigars in China

Aves polyomavirus 1 (APV) causes inflammatory disease in psittacine birds, especially in young budgerigar. In this study, an APV virus (SD18 strain) was isolated from a diseased psittacine birds breeding facility. The full genome (4981 bp) of SD18 was determined and analyzed. Phylogenetic analysis of full genome sequences indicated all the APV strains form two groups. The SD18 strain showed close relationship with APV isolated from Poland, however, the other Chinese strains are located in group II, which suggested different genotypes APVs are co-circulating in China. Compared with the consensus sequence of APV full genome, the SD18 strain contains 13 nucleotide mutations, and 2 unique amino acid substitutions (R179M and Q382K) located in VP2/3 and Large T proteins. To explore the pathogenicity of the virus, the SD18 strain was used to challenge 2-week-old budgerigars. All infected birds died no later than 5 days post infection, and virus was detected in multiple organs including brain, heart, ingluvies, liver, and intestine, which indicated that SD18 is fatal and causes systemic infection in young budgerigar. In vitro studies showed that SD18 replicated efficiently in CEF cells and reached the highest viral titers at 9 days post infection. Notably, replication of SD18 stimulated IFN-β response in CEF cells and overexpression of the VP4 or VP4Delta proteins significantly inhibited IFN-β promoter activation, which could be the strategy of APV to escape from the host innate immunity.

Complete Genome Sequence of an Avian Polyomavirus Strain First Isolated from a Pigeon in China

Avian polyomavirus can infect multiple bird species and cause inflammatory disease with high mortality in young psittacine birds. In this study, we sequenced and analyzed an avian polyomavirus isolated from a pigeon in China, strain APV-P, which is closely related to a polyomavirus in psittacine birds.

Avian polyomavirus can infect multiple bird species and cause inflammatory disease with high mortality in young psittacine birds. In this study, we sequenced and analyzed an avian polyomavirus isolated from a pigeon in China, strain APV-P, which is closely related to a polyomavirus in psittacine birds.

High prevalence of Mycobacterium genavense within flocks of pet birds

Mycobacterium genavense is regarded as the primary cause of mycobacteriosis in psittaciform and passeriform birds, which are commonly kept as pets. In humans, Mycobacterium genavense is especially pathogenic for young, old, pregnant and immunocompromised people (YOPIs). In birds, only few studies, mainly case reports, exist and there is still little e information about occurrence and relevance of this zoonotic pathogen. In this first pilot study concerning the prevalence of Mycobacterium genavense within flocks of naturally infected pet birds, real-time PCR examinations of 170 individual passeriform and psittaciform birds, including commonly kept budgerigars, lovebirds and zebra finches as well as gold finches and weaver finches, were conducted to determine the infection rate in six different aviaries. Antemortem examinations of faeces and cloacal swabs were compared with postmortem examinations of tissue samples to evaluate the reliability of antemortem diagnostics. Additional ophthalmologic examinations were performed to evaluate their diagnostic potential. Molecular examinations for viral co-infections, including circovirus, polyomavirus and adenovirus, were conducted to identify potential risk factors. PCR results revealed a detection prevalence of Mycobacterium genavense in the flocks varying from 3% to 91% based on postmortem testing, while antemortem diagnostics of faecal samples and swabs showed 64% discrepant (false negative) results. Ophthalmologic examinations were not useful in identifying infected birds within the flocks. Viral co-infections, especially with polyomavirus, were common. It has to be assumed that Mycobacterium genavense infections are widespread and underdiagnosed in companion birds. Viral infections might be an important risk factor. There is urgent need to improve antemortem diagnostics.