Comparison of the genomes of 15 avian herpes-virus isolates by restriction endonuclease analysis

Inclusion Body Herpesvirus Hepatitis in Captive Falcons in the Middle East: A Review of Clinical and Pathologic Findings

Inclusion body hepatitis in falcons is caused by a herpesvirus designated Falconid HV-1. This herpesvirus and other herpesviruses affecting birds of prey have not been assigned to a genus and include inclusion body herpesvirus hepatitis in eagles (Accipitrid HV-1) and inclusion body herpesvirus hepatitis in owls (Strigid HV-1). Herpesvirus infections have been diagnosed in both captive and free-living raptors across Europe, North America, and Asia in different species of the family Falconidae. Herpesviruses affecting owls and falcons have been found to be antigenically similar to pigeon herpesvirus (Columbid HV-1) and distinct from other avian herpesviruses. When the herpesvirus isolates from owls, falcons, and pigeons were compared by sequencing a fragment of the herpes viral DNA polymerase gene from those birds naturally infected with the virus, the sequences from these 3 sources were found to be nearly identical. The authors of this study concluded that the Falconid HV-1, Strigid HV-1, and Columbid HV-1 were the same virus. Furthermore, the authors also proposed that the virus therefore be referred to as Columbid HV-1 (CoHV-1), because pigeons may be responsible for the transmission of the virus to birds of prey. Pigeons are often carriers of the virus without showing any clinical signs. It has long been suspected that raptors may contract the infection by the ingestion of infected pigeons. Some studies have suggested that falcons may not contract the infection through the oral route by ingesting carrier pigeons, but through the ocular or nasal route. Inclusion body herpesvirus hepatitis is a frequently diagnosed disease in the captive falcon population used for falconry, racing, and breeding in the Middle East, and it seems to be associated with the extensive use of pigeons for training and as a food item. This paper reviews the clinical and pathological findings in falcons affected by inclusion body herpesvirus hepatitis in the Middle East.

Molecular characterization of the complete genome of falconid herpesvirus strain S-18

Falconid herpesvirus type 1 (FaHV-1) is the causative agent of falcon inclusion body disease, an acute, highly contagious disease of raptors. The complete nucleotide sequence of the genome of FaHV-1 has been determined using Illumina MiSeq sequencing. The genome is 204,054 nucleotides in length and has a class E organization. The genome encodes approximately 130 putative protein-coding genes, of which 70 are orthologs of conserved alphaherpesvirus and Mardivirus proteins. Three FaHV-1 genes (UL3.5, UL44.5 and CIRC) were identified that encode protein homologues unique to Mardivirus and Varicellovirus. The genome also encodes homologues to the Mardivirus genes LORF2, LORF3, LORF4, LORF5, SORF3 and SORF4. An opal mutation resulting in premature termination was identified in the FaHV-1 UL43 gene. Phylogenetically, FaHV-1 resides in a monophyletic group with the other Mardiviruses but, along with anatid herpesvirus 1, represents a more distant divergence from the rest of the Mardivirus genus.

Phylogenetic analysis of Columbid herpesvirus-1 in rock pigeons, birds of prey and non-raptorial birds in Poland

Background

The identity of herpesviruses isolated in Europe from domestic pigeons (Columbid herpesvirus-1 - CoHV-1) as well as falcons and owls remains unknown. All these herpesviruses are antigenically and genetically related. The falcons and owls are thought to have become infected during the ingestion of pigeon meat thus suggesting the virus’s capacity to infect a wide range of hosts. The aim of the conducted study was to detect the occurrence of CoHV-1 and estimating the similarities and differences in the DNA-dependent DNA polymerase gene of herpesviruses isolated from domestic pigeons, birds of prey and non-raptorial free-ranging birds in Poland.

Results

The study has shown the presence of CoHV-1 in 20.4% (18/88) in the examined birds. In case of one CoHV-1, infected Peregrine Falcon (Falco peregrinus), neurological signs were observed. Nucleotide sequencing of the DNA-dependent DNA polymerase gene, showed a high similarity among Polish strains (100%), independently from the species of the affected birds. Only one compared CoHV-1 strain - KP 21/23 originating from Germany showed a slightly lower similarity at a level of 99.1%. Further analysis has shown the identity of DNA-dependent DNA polymerase of CoHV-1 strains and other herpesviruses present in poultry as well as other birds ranged from 35.4 to 44.9%. Interestingly CoHV-1 infection was also confirmed for the first time in four non-raptorial birds.

Conclusions

The current study has shown a high similarity of CoHV-1 strains and the possible transmission of herpesviruses between domestic rock pigeons and free-ranging birds including raptors and non-raptorial birds. Further studies focused on cloning and the analysis of the whole CoHV-1 genome which is needed to explain the role of the observed similarities and differences between field strains of columbid herpesviruses.

A novel herpesvirus in 3 species of pheasants: mountain peacock pheasant (Polyplectron inopinatum), Malayan peacock pheasant (Polyplectron malacense), and Congo peafowl (Afropavo congensis)

The mountain peacock pheasant (Polyplectron inopinatum), the Malayan peacock pheasant (Polyplectron malacense), and the Congo peafowl (Afropavo congensis) are all listed as vulnerable to extinction under the International Union for Conservation of Nature Red List of Threatened Species. Here the authors report fatal infection with a novel herpesvirus in all 3 species of birds. DNA was extracted from the livers of birds with hepatocellular necrosis and intranuclear eosinophilic inclusions consistent with herpesvirus infection. Based on degenerate herpesvirus primers and polymerase chain reaction, 220- and 519-base pair products of the herpes DNA polymerase and DNA terminase genes, respectively, were amplified. Sequence analysis revealed that all birds were likely infected with the same virus. At the nucleotide level, the pheasant herpesvirus had 92% identity with gallid herpesvirus 3 and 77.7% identity with gallid herpesvirus 2. At the amino acid level, the herpes virus had 93.8% identity with gallid herpesvirus 3 and 89.4% identity with gallid herpesvirus 2. These findings indicate that the closest relative to this novel herpesvirus is gallid herpesvirus 3, a nonpathogenic virus used widely in a vaccine against Marek's disease. In situ hybridization using probes specific to the peacock pheasant herpesvirus DNA polymerase revealed strong intranuclear staining in the necrotic liver lesions of an infected Malayan peacock pheasant but no staining in normal liver from an uninfected bird. The phasianid herpesvirus reported here is a novel member of the genus Mardivirus of the subfamily Alphaherpesvirinae and is distinct from other galliform herpesviruses.

Comparison of commercial ELISA test kits from Australia and the USA with the serum neutralization test in cell cultures for the detection of antibodies to the infectious laryngotracheitis virus of chickens

The objective of this work was the evaluation under our conditions of two commercial ELISA kits for the detection of antibodies to avian infectious laryngotracheitis (ILT) virus, one from Australia (Trop-ELISA, TropBio) and one from the USA (ProFLOK-ELISA, KPL), and to compare their performance with the conventional serum neutralization test (SNT) in chick embryo liver cells. Repeatability varied considerably, particularly when using the Trop-ELISA. Therefore, if individual results are important, at least two parallel measurements per serum sample are recommended. In 89.3% of the sera tested by SNT, results of two parallel measurements did not vary by more than one 2-fold dilution step. There was good linear correlation between both ELISAs and the SNT, the correlation coefficient for the Trop-ELISA being r = 0.758 and for the ProFLOK-ELISA r = 0.867. The negative/positive cut-off was redefined to suit our conditions. Sera with a SN titre of > or = 1:4 were considered positive. Sera with < or = 15% absorption in the ProFLOK-ELISA were considered clearly negative. For the Trop-ELISA, extinctions of > or = 0.477 were considered positive, < or = 0.168 clearly negative. Values in between were regarded as doubtful for young chickens and as possibly due to non-specific reactions in older chickens. The sensitivity and specificity of the ELISAs relative to the SNT were 87 and 77% for the Trop-ELISA, and 95 and 60%, respectively, for the ProFLOK-ELISA. However, the results indicate that the sensitivity of the ELISA is higher than that of the SNT, because most sera showed similar deviations from SNT results with both ELISAs. Generally, both ELISAs were a suitable alternative to the SNT under our conditions, as long as only negative/positive results are required.

Pacheco's disease in a Hungarian zoo bird population: a case report

An epizootic of Pacheco's disease is reported from a zoo bird population. The infection was introduced by wild-captured Patagonian conures (Cyanoliseus patagonus) despite 61 days of quarantine. The disease affected several parrot species and, interestingly, three out of seven bearded barbets (Lybius dubius). The mortality rate was 30.93%. Autopsy revealed abdominal hyperaemia with liver haemorrhages and, in less rapid cases, yellowish discoloration and fragility of the liver. Death was caused by the collapse of circulation. Histopathology demonstrated liver cell necrosis, disintegration of the lobular structure, and a few intranuclear inclusion bodies. Icosahedral virions were detected by electron microscopy. The virus was isolated in the allantoic cavity of embryonated chicken eggs as well as in chicken embryo fibroblast cell culture. A 281-bp-long fragment of psittacid herpesvirus DNA was detected by PCR in cell culture material and liver samples of the affected birds. To our knowledge this is the first report of Pacheco's disease in bearded barbets as well as the first occurrence of Pacheco's disease in Hungary.

Characterization of the genes encoding UL24, TK and gH proteins from duck enteritis virus (DEV): a proof for the classification of DEV

Duck enteritis virus (DEV) is classified to the family Herpesviridae, but has not been grouped into any genus so far. Four overlapped fragments were amplified from the DEV genome with polymerase chain reaction (PCR). The assembled length of the four fragments was 6,202 bp, which contained the genes encoding unique long (UL) 24, thymidine kinase (TK) and glycoprotein H (gH) proteins. The UL24 overlapped with TK by 64 nucleotides (nt), in a head-to-head transcription orientation, and the TK and gH had the same transcription orientation. The comparison of amino acid sequences of these 3 deduced DEV proteins with other 12 alphaherpesviruses displayed 5 highly conserved sites in the UL24, as well as another 5 consensus regions in the TK and 4 consensus regions in the gH. The RNA polymerase II transcriptional control elements were identified in all the UL24, TK and gH of DEV. These elements included core promoters, TATA motifs and polyadenylation sites. Phylogenetic analysis for the genetic classification of DEV in the Alphaherpesvirinae subfamily with other 12 alphaherpesviruses was computed. The result showed that DEV was more closely related to avian herpesviruses, except infectious laryngotracheitis virus (ILTV), than to other alphaherpesviruses. Conclusively, according to the phylogenesis-based analysis and the homology comparison of functional domains of UL24, TK and gH, DEV should be classified to a separate genus of the Alphaherpesvirinae subfamily in the family Herpesviridae.

Psittacid herpesvirus 1 and infectious laryngotracheitis virus: Comparative genome sequence analysis of two avian alphaherpesviruses

Psittacid herpesvirus 1 (PsHV-1) is the causative agent of Pacheco's disease, an acute, highly contagious, and potentially lethal respiratory herpesvirus infection in psittacine birds, while infectious laryngotracheitis virus (ILTV) is a highly contagious and economically significant avian herpesvirus which is responsible for an acute respiratory disease limited to galliform birds. The complete genome sequence of PsHV-1 has been determined and compared to the ILTV sequence, assembled from published data. The PsHV-1 and ILTV genomes exhibit similar structural characteristics and are 163,025 bp and 148,665 bp in length, respectively. The PsHV-1 genome contains 73 predicted open reading frames (ORFs), while the ILTV genome contains 77 predicted ORFs. Both genomes contain an inversion in the unique long region similar to that observed in pseudorabies virus. PsHV-1 is closely related to ILTV, and it is proposed that it be assigned to the Iltovirus genus. These two avian herpesviruses represent a phylogenetically unique clade of alphaherpesviruses that are distinct from the Marek's disease-like viruses (Mardivirus). The determination of the complete genomic nucleotide sequences of PsHV-1 and ILTV provides a tool for further comparative and functional analysis of this unique class of avian alphaherpesviruses.

Genetic Characterization of a Herpesvirus Isolate from a Superb Starling (Lamprotornis superbus) as a Psittacid Herpesvirus Genotype 1

Four genotypes of the psittacid herpesvirus (PsHV) cause Pacheco disease in parrots. Viruses that are serologically cross-reactive to the PsHVs have also been isolated from passerine species. DNA was amplified from a herpesvirus isolated from a superb starling (Lamprotornis superbus) with PsHV-specific primers and polymerase chain reaction. A comparison of the partial sequence of the UL 16 gene from this herpesvirus with sequences from viruses of known PsHV genotypes showed that the herpesvirus from the superb starling was a PsHV genotype 1 virus. This finding expands the range of birds that are known to be susceptible to PsHV genotype 1 infections and suggests that PsHVs should be considered as a differential in passerines with herpesvirus infections.

Molecular phylogeny of the psittacid herpesviruses causing Pacheco's disease: correlation of genotype with phenotypic expression

Fragments of 419 bp of the UL16 open reading frame from 73 psittacid herpesviruses (PsHVs) from the United States and Europe were sequenced. All viruses caused Pacheco's disease, and serotypes of the European isolates were known. A phylogenetic tree derived from these sequences demonstrated that the PsHVs that cause Pacheco's disease comprised four major genotypes, with each genotype including between two and four variants. With the exception of two viruses, the serotypes of the virus isolates could be predicted by the genotypes. Genotypes 1 and 4 corresponded to serotype 1 isolates, genotype 2 corresponded to serotype 2 isolates, and genotype 3 corresponded to serotype 3 isolates. The single serotype 4 virus mapped to genotype 4. DNA from a virus with a unique serotype could not be amplified with primers that amplified DNA from all other PsHVs, and its classification remains unknown. Viruses representing all four genotypes were found in both the United States and Europe, and it was therefore predicted that serotypes 1, 2, and 3 were present in the United States. Serotype 4 was represented by a single European isolate that could not be genetically distinguished from serotype 1 viruses; therefore, the presence of serotype 4 in the United States could not be predicted. Viruses of genotype 4 were found to be the most commonly associated with Pacheco's disease in macaws and conures and were least likely to be isolated in chicken embryo fibroblasts in the United States. All four genotypes caused deaths in Amazon parrots, but genotype 4 was associated with Pacheco's disease only in Amazons in Europe. Genotypes 2, 3, and 4, but not 1, were found in African grey parrots. Although parrots from the Pacific distribution represent a relatively small percentage of the total number of birds with Pacheco's disease, all four genotypes were found to cause disease in these species.

Characterization of a herpesvirus associated with tracheitis in Gouldian finches (Erythrura [Chloebia] gouldiae)

Severe tracheitis and bronchitis were identified in two fatal cases of respiratory disease affecting a flock of Gouldian finches (Erythrura [Chloebia] gouldiae). Intranuclear inclusion bodies in epithelial cells of the upper respiratory tract were identified in samples from two birds. Electron microscopic examination showed that the inclusions consisted of viral particles consistent in appearance with Herpesviridae. Degenerate PCR primers targeting a conserved region of the herpesviral-DNA-dependent DNA polymerase were used to amplify a region of DNA isolated from tissues with lesions from each animal. Nucleotide sequencing of the PCR products yielded identical viral sequences that were distinct from known herpesviruses. An analysis of sequence homology indicated that these gene segments appear to belong to a member of the subfamily Alphaherpesvirinae.

Detection and heterogeneity of herpesviruses causing Pacheco's disease in parrots

Pacheco's disease (PD) is a common, often fatal, disease of parrots. We cloned a virus isolate from a parrot that had characteristic lesions of PD. Three viral clones were partially sequenced, demonstrating that this virus was an alphaherpesvirus most closely related to the gallid herpesvirus 1. Five primer sets were developed from these sequences. The primer sets were used with PCR to screen tissues or tissue culture media suspected to contain viruses from 54 outbreaks of PD. The primer sets amplified DNA from all but one sample. Ten amplification patterns were detected, indicating that PD is caused by a genetically heterogeneous population of viruses. A single genetic variant (psittacid herpesvirus variant 1) amplified with all primer sets and was the most common virus variant (62.7%). A single primer set (23F) amplified DNA from all of the positive samples, suggesting that PCR could be used as a rapid postmortem assay for these viruses. PCR was found to be significantly more sensitive than tissue culture for the detection of psittacid herpesviruses.

Detection of new DNA polymerase genes of known and potentially novel herpesviruses by PCR with degenerate and deoxyinosine-substituted primers

A consensus primer PCR approach was used to (i) investigate the presence of herpesviruses in wild and zoo equids (zebra, wild ass, tapir) and to (ii) study the genetic relationship of the herpesvirus of pigeons (columbid herpesvirus 1) to other herpesvirus species. The PCR assay, based on degenerate primers targeting highly conserved regions of the DNA polymerase gene of herpesviruses, was modified by using a mixture of degenerate and deoxyinosine-substituted primers. The applicability of the modification was validated by amplification of published DNA polymerase genes of 16 herpesvirus species and of the previously uncharacterized DNA polymerase genes of equine herpesvirus 3 (EHV-3) and equine herpesvirus 5 (EHV-5). The modified assay was then used for partial amplification of the polymerase of columbid herpesvirus 1 which is presently classified as a beta-herpesvirus based on biological criteria. Sequence analysis of amplicons obtained from four different viral strains revealed a close relationship of columbid herpesvirus 1 to members of the subfamily Alphaherpesvirinae, especially to Marek's disease herpesvirus. This was confirmed by characterization of additional 1.6kb of the columbid herpesvirus 1 polymerase. Consensus PCR analysis of blood samples from zebras, a wild ass and a tapir revealed amplicons showing high percentages ( > 50%) of sequence identity to DNA polymerases of gamma-herpesviruses. In particular, the zebra and the wild ass sequence were closely related to each other and to the polymerases of the equine gamma-herpesviruses EHV-2 and EHV-5 with sequence identities of > 80%. This is a first indication that novel gamma-herpesviruses are present in wild and zoo equids.

Development of a polymerase chain reaction to detect Vietnamese isolates of duck virus enteritis

A polymerase chain reaction (PCR) method for the detection of duck virus enteritis (DVE) virus in tissues of infected and affected ducks, and in cell culture was developed. This required us to obtain specific nucleotide sequence information as we could not find any specific data about the genome of the virus. We found the assay to be highly effective in detecting the virus under experimental conditions and to be easily transferred to laboratories in Vietnam where it is being used in studies on the epidemiology of the disease. We have applied this simple and rapid diagnostic method to the detection of DVE isolates grown in cell culture and tissues from infected birds. The assay was also able to differentiate DVE from other avian herpesviruses, such as Marek's disease, infectious laryngotracheitis virus and goose herpesvirus.