Avian encephalomyelitis in naturally infected pigeons in Turkey

Recombinant Viruses from the Picornaviridae Family Occurring in Racing Pigeons

Viruses from Picornaviridae family are known pathogens of poultry, although the information on their occurrence and pathogenicity in pigeons is scarce. In this research, efforts are made to broaden the knowledge on Megrivirus B and Pigeon picornavirus B prevalence, phylogenetic relationship with other avian picornaviruses and their possible connection with enteric disease in racing pigeons. As a result of Oxford Nanopore Sequencing, five Megrivirus and two pigeon picornavirus B-like genome sequences were recovered, among which three recombinant strains were detected. The recombinant fragments represented an average of 10.9% and 25.5% of the genome length of the Pigeon picornavirus B and Megrivirus B reference strains, respectively. The phylogenetic analysis revealed that pigeons are carriers of species-specific picornaviruses. TaqMan qPCR assays revealed 7.8% and 19.0% prevalence of Megrivirus B and 32.2% and 39.7% prevalence of Pigeon picornavirus B in the group of pigeons exhibiting signs of enteropathy and in the group of asymptomatic pigeons, respectively. In turn, digital droplet PCR showed a considerably higher number of genome copies of both viruses in sick than in asymptomatic pigeons. The results of quantitative analysis leave the role of picornaviruses in enteropathies of pigeons unclear.

Research Note: Pathogenetic characteristics of avian encephalomyelitis virus in Guangdong and Jiangxi Provinces, China

In recent years, the infection rate of avian encephalomyelitis virus (AEV) infection in chickens has risen significantly, seriously endangering the development of the chicken industry. In order to study the current epidemiological status of AEV in China as well as the genetic and evolutionary patterns of the virus, we conducted a survey and genomic analysis of chicken AEV. The results showed that 46.26% (136/294) of the tissue samples tested (n = 294) were positive for AEV, with the highest positivity rate of 62.24% (61/98) among tissue samples from chickens aged 13 to 18 wk. The complete genomes of 2 representative AEV strains were determined, and the VP1 evolutionary tree results revealed that the 2 representative strains belonged to a novel AEV strain. Multiple alignment analysis showed that the ORF1 genes of the 2 representative strains differed by 82.3 to 99.9% at the amino acid level compared with the reference AEV strain, and the mutations at the key amino acid loci of VP2 and VP3 were the same as those in the chick embryo-adapted strain. The analysis makes up for the molecular epidemiological data and genetic variation of the 2 representative strains. The analysis makes up for the molecular epidemiological data and genetic variation of AEV and provides a basis for further understanding the spread of AEV in China.

Occurrence and Role of Selected RNA-Viruses as Potential Causative Agents of Watery Droppings in Pigeons

The diseases with watery droppings (diarrhea and/or polyuria) can be considered some of the most severe health problems in domestic pigeons of various ages. Although they do not always lead to bird death, they can contribute to poor weight gains and hindered development of young pigeons and, potentially, to poor racing results in sports birds. The gastrointestinal tract disorders of pigeons may be of various etiology, but some of the causative agents are viral infections. This review article provides information collected from scientific reports on RNA-viruses belonging to the Astroviridae, Picornaviridae, and Coronaviridae families; the Avulavirinae subfamily; and the Rotavirus genus that might be implicated in such health problems. It presents a brief characterization, and possible interspecies transmission of these viruses. We believe that this review article will help clinical signs of infection, isolation methods, occurrence in pigeons and poultry, systemize and summarize knowledge on pigeon enteropathogenic viruses and raise awareness of the importance of disease control in pigeons.

A Review of Pathogen Transmission at the Backyard Chicken-Wild Bird Interface

Habitat conversion and the expansion of domesticated, invasive species into native habitats are increasingly recognized as drivers of pathogen emergence at the agricultural-wildlife interface. Poultry agriculture is one of the largest subsets of this interface, and pathogen spillover events between backyard chickens and wild birds are becoming more commonly reported. Native wild bird species are under numerous anthropogenic pressures, but the risks of pathogen spillover from domestic chickens have been historically underappreciated as a threat to wild birds. Now that the backyard chicken industry is one of the fastest growing industries in the world, it is imperative that the principles of biosecurity, specifically bioexclusion and biocontainment, are legislated and implemented. We reviewed the literature on spillover events of pathogens historically associated with poultry into wild birds. We also reviewed the reasons for biosecurity failures in backyard flocks that lead to those spillover events and provide recommendations for current and future backyard flock owners.

Assessing the efficacy of a live vaccine against avian encephalomyelitis virus

Avian encephalomyelitis virus (AEV) causes typical neurological symptoms in young chicks and a transient drop in egg production and hatchability in adult laying birds, resulting in huge economic losses in the poultry industry. An effective way to control and prevent this disease is vaccination of the flocks. Here, we assessed the efficacy of the live vaccine candidate strain GDt29 against avian encephalomyelitis virus. The GDt29 strain has low virulence, was confirmed safe, and showed no signs of pathogenicity. High titers of AEV-specific antibodies were detected in GDt29-vaccinated hens (S/P > 3.0) and their progeny (S/P > 2.0). Moreover, the eggs of GDt29-vaccinated hens with high levels of maternal antibodies were hatched successfully regardless of challenge with a heterologous AEV strain, and the GDt29 attenuated vaccine showed higher protective efficacy against AEV than the commercial vaccine. Furthermore, contact-exposed chicks bred with GDt29-vaccinated birds generated high titers against AE virus (S/P > 2.8). Collectively, our studies are proof of the principle that GDt29 might be an ideal vaccine candidate to prevent AEV infection, and they highlight the utility of using a live vaccine against AEV.

Galliformes and Columbiformes

Galliformes and columbifomes are closely associated with humans and some species have been domesticated for well over 5000 years. Both orders remain diverse, ranging from the common domestic poultry species (e.g., chicken, turkey, and squabs) to the more exotic species found in the wild and in zoological collections. While many species have been benefited from human activities and have increased their ranges, others have declined in numbers and some have become threatened (e.g., Trinidad piping-guan and wood quail) or even extinct (e.g., dodo and passenger pigeon). Nondomestic galliformes and columbiformes are susceptible to many of the same diseases that occur in domestic species, yet predisposition may be different. Furthermore, disease prevalence depends on exposure and potential risk factors. Infectious diseases that tend to be more common under intensive commercial production may not pose as great a risk to exotic and free-living species.

Dynamic distribution and tissue tropism of avian encephalomyelitis virus isolate XY/Q-1410 in experimentally infected Korean quail

Avian encephalomyelitis (AE) is an important infectious poultry disease worldwide that is caused by avian encephalomyelitis virus (AEV). However, to date, the dynamic distribution of AEV in quails has not been well described. Quantitative real-time polymerase chain reaction (qPCR) and immunohistochemistry (IHC) assays were used to investigate the dynamic distribution and tissue tropism of AEV in experimentally infected Korean quail. AEV was detected in the cerebrum, cerebellum, proventriculus, intestine, liver, pancreas, spleen, bursa, lung and kidney as early as 3 days post-infection (dpi). The viral loads in the proventriculus, intestine, spleen and bursa were relatively higher than in other tissues. According to the qPCR results, AEV XY/Q-1410 infection lasted for at least 60 days in infected Korean quail. Immunohistochemistry-positive staining signals of AEV antigen were analysed by Image-Pro Plus software. A positive correlation between qPCR and IHC results was identified in most tissues. Our results provide an insight into the dynamic distribution of AEV in various tissues after infection. The distinct dynamic distribution of the viral genome in Korean quail in the early and late stages of infection suggests that AEV replication is affected by antibody levels and the maturity of the immune system of the host.

Serological evidence of avian encephalomyelitis virus and Pasteurella multocida infections in free-range indigenous chickens in Southern Mozambique

A total of 398 serum samples from free-range indigenous chickens originating from four villages in Southern Mozambique were tested for the presence of avian encephalomyelitis virus (AEV) and Pasteurella multocida (PM) antibodies through commercial enzyme-linked immunosorbent assay (ELISA) kits. AEV and PM antibodies were detected in all villages surveyed. The proportion of positive samples was very high: 59.5% (95% confidence interval (CI) 51.7-67.7%) for AEV and 71.5% (95% CI 67.7-77.3%) for PM. Our findings revealed that these pathogens are widespread among free-range indigenous chickens in the studied villages and may represent a threat in the transmission of AEV and PM to wild, broiler or layer chickens in the region. Further research is warranted on epidemiology of circulating strains and impact of infection on the poultry industry.

Analysis of viral protein-2 encoding gene of avian encephalomyelitis virus from field specimens in Central Java region, Indonesia

Aim:

Avian encephalomyelitis (AE) is a viral disease which can infect various types of poultry, especially chicken. In Indonesia, the incidence of AE infection in chicken has been reported since 2009, the AE incidence tends to increase from year to year. The objective of this study was to analyze viral protein 2 (VP-2) encoding gene of AE virus (AEV) from various species of birds in field specimen by reverse transcription polymerase chain reaction (RT-PCR) amplification using specific nucleotides primer for confirmation of AE diagnosis.

Materials and Methods:

A total of 13 AEV samples are isolated from various species of poultry which are serologically diagnosed infected by AEV from some areas in central Java, Indonesia. Research stage consists of virus samples collection from field specimens, extraction of AEV RNA, amplification of VP-2 protein encoding gene by RT-PCR, separation of RT-PCR product by agarose gel electrophoresis, DNA sequencing and data analysis.

Results:

Amplification products of the VP-2 encoding gene of AEV by RT-PCR methods of various types of poultry from field specimens showed a positive results on sample code 499/4/12 which generated DNA fragment in the size of 619 bp. Sensitivity test of RT-PCR amplification showed that the minimum concentration of RNA template is 127.75 ng/µl. The multiple alignments of DNA sequencing product indicated that positive sample with code 499/4/12 has 92% nucleotide homology compared with AEV with accession number AV1775/07 and 85% nucleotide homology with accession number ZCHP2/0912695 from Genbank database. Analysis of VP-2 gene sequence showed that it found 46 nucleotides difference between isolate 499/4/12 compared with accession number AV1775/07 and 93 nucleotides different with accession number ZCHP2/0912695.

Conclusions:

Analyses of the VP-2 encoding gene of AEV with RT-PCR method from 13 samples from field specimen generated the DNA fragment in the size of 619 bp from one sample with sample code 499/4/12. The sensitivity rate of RT-PCR is to amplify the VP-2 gene of AEV until 127.75 ng/µl of RNA template. Compared to Genbank databases, isolate 499/4/12 has 85% and 92% nucleotide homology.

Serological evidence of avian encephalomyelitis virus infection associated with vertical transmission in chicks

Avian encephalomyelitis virus (AEV) can be transmitted both horizontally and vertically. In the present study, we report a typical case of AEV infection in broiler breeder chickens and their progeny identified by clinical survey of the disease, antibody detection, and reverse transcription (RT)-polymerase chain reaction (PCR) assay.

Avian picornaviruses: molecular evolution, genome diversity and unusual genome features of a rapidly expanding group of viruses in birds

Picornaviridae is one of the most diverse families of viruses infecting vertebrate species. In contrast to the relative small number of mammal species compared to other vertebrates, the abundance of mammal-infecting picornaviruses was significantly overrepresented among the presently known picornaviruses. Therefore most of the current knowledge about the genome diversity/organization patterns and common genome features were based on the analysis of mammal-infecting picornaviruses. Beside the well known reservoir role of birds in case of several emerging viral pathogens, little is known about the diversity of picornaviruses circulating among birds, although in the last decade the number of known avian picornavirus species with complete genome was increased from one to at least 15. However, little is known about the geographic distribution, host spectrum or pathogenic potential of the recently described picornaviruses of birds. Despite the low number of known avian picornaviruses, the phylogenetic and genome organization diversity of these viruses were remarkable. Beside the common L-4-3-4 and 4-3-4 genome layouts unusual genome patterns (3-4-4; 3-5-4, 3-6-4; 3-8-4) with variable, multicistronic 2A genome regions were found among avian picornaviruses. The phylogenetic and genomic analysis revealed the presence of several conserved structures at the untranslated regions among phylogenetically distant avian and non-avian picornaviruses as well as at least five different avian picornavirus phylogenetic clusters located in every main picornavirus lineage with characteristic genome layouts which suggests the complex evolution history of these viruses. Based on the remarkable genetic diversity of the few known avian picornaviruses, the emergence of further divergent picornaviruses causing challenges in the current taxonomy and also in the understanding of the evolution and genome organization of picornaviruses will be strongly expected. In this review we would like to summarize the current knowledge about the taxonomy, pathogenic potential, phylogenetic/genomic diversity and evolutional relationship of avian picornaviruses.

Avian encephalomyelitis virus in reared pheasants: a case study

An outbreak of neurological disease occurred in pheasant chicks on a game farm in 2007. The disease was first seen in the 10th hatching of chicks on the farm. Affected chicks showed trembling and incoordination from the time of hatching, and subsequently blindness and cataract formation was seen in some of the affected chicks at 3 weeks of age. The peak mortality and culling figure was 21.0% in the worst affected hatch, compared with a maximum of 11.7% in the first nine hatches. No further cases were evident by 7.5 weeks of age. Histopathological examination showed a moderate acute encephalomyelitis in some, but not all, of the chicks with neurological signs. The clinical presentation and histopathological findings were typical of vertically transmitted avian encephalomyelitis as seen in chickens, although avian encephalomyelitis virus could not be detected in inoculated embryonated chicken eggs. However, serological testing by enzyme-linked immunosorbent assay for antibodies to the virus was positive in four of five affected 3-week-old birds and in 23 out of 29 adult breeding birds, and reverse transcriptase-polymerase chain reaction testing of RNA extracted from brain and pancreas tissue of affected chicks yielded nucleotide sequences aligned 82% and 83% with three avian encephalomyelitis sequences in a sequence database. The evidence suggested that the neurological disease was attributable to infection with a strain of avian encephalomyelitis virus that appeared to have entered the flock at the start of the breeding season, and was possibly introduced by carrier pheasants brought on to the farm early in the season.

Visceral leishmaniosis and parapoxvirus infection in a Mediterranean monk seal (Monachus monachus)

A Mediterranean monk seal was shown by immunohistochemical and polymerase chain reaction techniques to be dually infected with a Leishmania sp. and parapoxvirus. The pathological findings included a deep ulcer on the side of the head, ulcers on the gingival and inner aspect of the lower lip, enlarged lymph nodes and tonsils, and respiratory lesions (pulmonary consolidation, oedema, haemorrhages and emphysema; tracheal and bronchial congestion, exudates and haemorrhage). Amastigotes were demonstrated in macrophages in the lymph nodes and spleen, and intracytoplasmic inclusion bodies were observed in the tracheal and oral mucosa.

Viral infections in pigeons

This review provides a current update on the major viral diseases of the domestic pigeon (Columba livia domestica), based on scientific reports and clinical experience. Paramyxovirus 1, adenovirus, rotavirus, herpesvirus 1, poxvirus and circovirus infections are described according to common clinical signs and target tissues. Since pigeons are sometimes treated as if they were poultry, the review also summarises the common viral infections of poultry for which pigeons are considered resistant. It is hoped that the review will provide a useful reference for veterinarians and others and offer advice on the diagnosis, treatment and prevention of the major infectious diseases of pigeons.