Herpesviruses of birds--a review

Unraveling the evolutionary origin of the complex Nuclear Receptor Element (cNRE), a cis-regulatory module required for preferential expression in the atrial chamber

Cardiac function requires appropriate proteins in each chamber. Atria requires slow myosin to act as reservoirs, while ventricles demand fast myosin for swift pumping. Myosins are thus under chamber-biased cis-regulation, with myosin gene expression imbalances leading to congenital heart dysfunction. To identify regulatory inputs leading to cardiac chamber-biased expression, we computationally and molecularly dissected the quail Slow Myosin Heavy Chain III (SMyHC III) promoter that drives preferential expression to the atria. We show that SMyHC III gene states are orchestrated by a complex Nuclear Receptor Element (cNRE) of 32 base pairs. Using transgenesis in zebrafish and mice, we demonstrate that preferential atrial expression is achieved by a combinatorial regulatory input composed of atrial activation motifs and ventricular repression motifs. Using comparative genomics, we show that the cNRE might have emerged from an endogenous viral element through infection of an ancestral host germline, revealing an evolutionary pathway to cardiac chamber-specific expression.

DETECTION AND PREVALENCE OF SPHENISCID ALPHA-HERPESVIRUS-1 (SpAHV-1) IN A SAMPLE OF HUMBOLDT PENGUINS (SPHENISCUS HUMBOLDTI) AT PUNTA SAN JUAN, PERU

Infections with herpesvirus have contributed to respiratory, enteric, and neurological disease reports in avian species worldwide. Herpesviruses have been detected in penguin species before but have not been studied extensively. To better understand the impact of these viruses in free-living populations, an initial retrospective survey was performed on a wild population of Humboldt penguins (Spheniscus humboldti) in the Punta San Juan Marine Protected Area, Peru (15°22'S, 75°12'W) using tracheal swabs collected from 28 penguins in 2016 and 34 penguins in 2018. DNA extracted from these swabs was analyzed using a consensus herpesviral PCR assay targeting the DNA polymerase gene, and positive samples were sequenced. A single sample from 2016 was positive for spheniscid alpha-herpesvirus-1 (SpAHV-1), establishing an overall sample prevalence of 1.6% (95% CI: 0-8.6%). The positive animal was an adult male that did not show any clinical signs of herpesviral infection and was otherwise healthy based on physical exam and laboratory findings. This is the first detection of a herpesvirus in penguins at Punta San Juan, Peru, and the first step toward characterizing the implications of SpAHV-1 for Humboldt penguins. This investigation highlights the importance of continual disease surveillance in wild populations over time to monitor for changes that may impact long-term population viability.

Investigation of a herpesvirus outbreak in mixed breeds of adult domestic ducks using next generation sequencing

This report characterizes the first lethal outbreak of Marek's disease on a large farm of mixed-breed adult ducks (>18,000) and identifies the pathogen that resulted in high mortality (35%). Clinical signs included inappetence, respiratory distress, depression, muscle weakness, and ataxia. Post mortem revealed enlarged fragile liver mottled with miliary whitish spots and an enlarged spleen. Histopathology revealed hepatocellular necrosis with eosinophilic intra-nuclear inclusion bodies, necrosis of splenic follicles and degeneration/necrosis of renal tubules. The disease was tentatively diagnosed as a herpesvirus infection, confirmed by virus isolation from the liver. DNA was isolated from 15-year-old archival formalin-fixed tissues from infected ducks and subjected to next generation sequencing (NGS). Despite highly degraded DNA, short stretches of G- and C-rich repeats (TTAGGG and TAACCC) were identified as telomeric repeats frequently found in herpesviruses. Megablast and further investigative bioinformatics identified presence of Marek's disease virus (MDV), a Gallid alphaherpesvirus type 2 (GAHV-2), as the cause of the acute fatal infection. The source of infection may be attributed to a dead migratory flamingo found close to the duck enclosures three days prior to the outbreak; hence, GAHV-2 may also be responsible for the fatal infection of the flamingo accentuated by heat stress. Considering the possible spread of this highly contagious and lethal virus from a flamingo to the ducks, and the increasing zoonosis of animal viruses into humans, such as monkey B alphaherpesvirus transmission from macaques to humans with ~80% fatality, this observation has important ramifications for human health and safety of the poultry industry.

Infection due to Buteo buteo herpesvirus in a common buzzard (Buteo buteo insularum)

This study aimed to document the pathological findings observed in a common buzzard (Buteo buteo insularum) from Gran Canaria (Canary Islands, Atlantic Ocean), naturally infected with Buteo buteo herpesvirus (HV). Local authorities found the common buzzard alive, but it died after 10 days of specialized veterinary care. Postmortem investigation, including complete gross and histologic examination, immunohistochemistry, microbiology, and PCR, was performed. The animal presented necrotizing heterophilic and histiocytic bilateral conjunctivitis, stomatitis, pharyngitis, rhinitis, and sinusitis with secondary bacterial and fungal infections. Frequent eosinophilic intranuclear inclusion bodies were observed in the oral mucosa and esophagus epithelium. HV proteins and DNA were detected in tissues from this animal. The sequences obtained from the PCR product were identical to the reported sequences of Buteo buteo HV.

Genomic characteristics, pathogenicity and viral shedding of a novel DVEV variant derived from goose

Duck virus enteritis (DVE), caused by the DVE virus (DVEV), is an acute, septicemic, and contagious disease affecting ducks of different breeds, ages, and sexes. In late spring and summer 2019, several outbreaks of DVE were reported in areas with large waterfowl industries in central and southern China. A goose farm located in Jining County, Shandong Province, was impacted by an acute DVE outbreak in July 2019. The causative DVEV field strain (Goose/DVEV/SDJN/China/2019) was subsequently isolated from the liver specimens collected from acute cases of dead geese, which showed severe hemorrhagic lesions on the esophageal mucosal membranes of specimens collected from all the postmortem cases. Comparison of the genome sequence of this newly isolated field strain (Goose/DVEV/SDJN/China/2019) with the common DVEV strains revealed insertions or mutations in the gB and gC genes, which possibly caused the observed high morbidity and mortality in this acute outbreak. We conducted a trial among geese to evaluate the pathogenicity of this strain. Healthy experimental goslings aged 15 d old were inoculated with 10^-5.53 ELD₅₀/0.2 mL doses orally or through intramuscular injection. Clinical signs and esophageal erosion appeared in infected geese. Necropsy revealed hemorrhage and necrosis of the cloacal mucosa and liver. Detection of the virus using real-time PCR in the liver, brain, and spleen indicated that they were the hotspots of DVEV infections. One day after the DVEV infection, virus release and seroconvert were observed in infected geese. Thus, our studies demonstrate that DVEV is highly pathogenic and contagious in geese. To the best of our knowledge, this is the first study on the pathogenicity of mutant duck viral enteritis virus in goslings. This study serves as a foundation for further investigations into the pathophysiology of the recently identified variant DVEV strains.

Inclusion Body Disease and Columbid Alphaherpesvirus 1 Infection in a Eurasian Eagle-Owl (Bubo bubo) of Central Italy

Hepatosplenitis or inclusion body disease is a fatal disease in owls caused by Columbid alphaherpesvirus 1 (CoHV-1). A few old case reports describe it worldwide. In Italy, knowledge regarding virus circulation and disease development is lacking. Four Eurasian eagle-owls (Bubo bubo), two adults and two juveniles, were submitted for postmortem examination showing aspecific clinical signs a few hours before death. Grossly disseminated petechial hemorrhages on serosal surfaces (n = 4), hepatic and splenic necrosis (n = 3), bilateral and symmetric necrosis of pharyngeal tonsils (n = 2), and diffuse and bilateral dark-red discoloration and firmness in lungs (n = 2) were seen. Tissues were sampled for histology, bacteriology, molecular testing, and transmission electron microscopy (TEM). On histology, disseminated petechial hemorrhages (n = 4) and necrosis of liver (n = 3) and spleen (n = 3) were seen, as well as lympho-histiocytic interstitial pneumonia and meningoencephalitis (n = 2). Intranuclear inclusion bodies (INIBs) were detected in one case. A panherpesviral PCR led to positive results in one case, identified in sequencing as CoHV-1. On TEM, intranuclear and intracytoplasmic virions with herpesviral morphology were seen in the same case. For the other three birds, the lack of PCR positivity, INIBs, and TEM detection could be linked to a possible reduction of the virus to undetectable levels. Death possibly occurred secondarily to bacterial infections, supposedly established during the acute phase of CoHV-1 infection. This paper reports the presence of CoHV-1in Italy and the development of a fatal form of the disease in a Eurasian eagle-owl.

Effect of ketoprofen on intravenous pharmacokinetics of ganciclovir in chukar partridges (Alectoris chukar)

The aim of the study was to determine the effect of ketoprofen (2 mg/kg) on the intravenous pharmacokinetics of ganciclovir (10 mg/kg) in chukar partridges (Alectoris chukar). Eight clinically healthy partridges were used in the study. The study was performed in two periods using a cross-over design following a 15-day drug washout period. Plasma concentrations of ganciclovir were determined using the high-pressure liquid chromatography-ultraviolet detector and analyzed by non-compartmental analysis. The elimination half-life (t_1/2ʎz ), area under the concentration-time curve (AUC_0-∞ ), total body clearance, and volume of distribution at steady state of ganciclovir were 1.63 h, 33.22 h*μg/ml, 0.30 L/h/kg, and 0.53 L/kg, respectively. Ketoprofen administration increased the t_1/2ʎz and AUC_0-∞ of ganciclovir by 78% and 108%, respectively, and while decreased Cl_T by 53%. The increased plasma concentration and prolonged elimination half-life of ganciclovir caused by ketoprofen may result in the prolonged duration of action and therapeutic effect of ganciclovir. However, the concomitant use requires determination of the pharmacokinetics of ketoprofen and the safety of both drugs.

Resveratrol as an Adjunctive Therapy for Excessive Oxidative Stress in Aging COVID-19 Patients

The coronavirus disease 2019 (COVID-19) pandemic continues to burden healthcare systems worldwide. COVID-19 symptoms are highly heterogeneous, and the patient may be asymptomatic or may present with mild to severe or fatal symptoms. Factors, such as age, sex, and comorbidities, are key determinants of illness severity and progression. Aging is accompanied by multiple deficiencies in interferon production by dendritic cells or macrophages in response to viral infections, resulting in dysregulation of inflammatory immune responses and excess oxidative stress. Age-related dysregulation of immune function may cause a more obvious pathophysiological response to SARS-CoV-2 infection in elderly patients and may accelerate the risk of biological aging, even after recovery. For more favorable treatment outcomes, inhibiting viral replication and dampening inflammatory and oxidative responses before induction of an overt cytokine storm is crucial. Resveratrol is a potent antioxidant with antiviral activity. Herein, we describe the reasons for impaired interferon production, owing to aging, and the impact of aging on innate and adaptive immune responses to infection, which leads to inflammation distress and immunosuppression, thereby causing fulminant disease. Additionally, the molecular mechanism by which resveratrol could reverse a state of excessive basal inflammatory and oxidative stress and low antiviral immunity is discussed.

Herpesvirus Infection in a Breeding Population of Two Coexisting Strix Owls

Simple Summary

Although infection with herpesvirus in owls has commonly been described as a highly lethal disease, there is very little information about the presence of herpesvirus and its potential impact in living owls in wild populations. Our study detected herpesvirus in a breeding population of Ural owls, which showed no clinical signs of illness nor productivity deviances (i.e., in clutch and brood size). Herpesvirus was detected in Ural owl adults and chicks, but not in a young tawny owl (despite the fact that they were in same nest and in persistent contact). Furthermore, herpesviruses were also detected in yellow-necked mice as both owls’ main prey. However, comparison of the herpesviruses detected showed that different herpesviruses are present in the owls and mice. The results of this study show that herpesvirus may be present in a Ural owl breeding population without any consequences on health and breeding performance. However, in the case of tawny owls, it seems that they are not susceptible to infection, which could be related to their polymorphism. It seems that small rodents are not a source of herpesvirus infection in owls and that the probable herpesvirus transmission pathway takes place intraspecifically, mostly from adults to young.

Abstract

Birds are a frequent host of a large variety of herpesviruses, and infections in them may go unnoticed or may result in fatal disease. In wild breeding populations of owls, there is very limited information about the presence, impact, and potential transmission of herpesvirus. The herpesvirus partial DNA polymerase gene was detected using polymerase chain reaction in oropharyngeal swabs of 16 out of 170 owls examined that were captured in or near nest boxes. Herpesvirus was detected in Ural owls (Strix uralensis), in both adults and young, but not in tawny owls (Strix aluco). In yellow-necked mice (Apodemus flavicollis), as the main prey of tawny owls and Ural owls in the area, herpesvirus was detected in the organs of 2 out of 40 mice captured at the same locations as the owls. Phylogenetic analysis showed that the herpesvirus sequences detected in the Ural owls differed from the herpesvirus sequences detected in the yellow-necked mice. The results indicate that herpesvirus infection exists in the breeding wild Ural owl population. However, herpesvirus-infected owls did not show any clinical or productivity deviances and, based on a phylogenetic comparison of detected herpesvirus sequences and sequences obtained from Genbank database, it seems that mice and other rodents are not the source of owl infections. The most probable transmission pathway is intraspecific, especially from adults to their chicks, but the origin of herpesvirus in owls remains to be investigated.

Herpesvirus Encephalitis in a Little Blue Penguin (Eudyptula minor)

An 11-day-old little blue penguin (Eudyptula minor) died unexpectedly. Prior to hatching, the egg experienced trauma and resultant defects were repaired. The chick hatched without complication and was clinically normal prior to death. Necropsy revealed congested lungs. Histologic examination showed moderate nonsuppurative encephalitis with focally extensive neuronal necrosis and intranuclear inclusions in neurons within necrotic foci. Herpesvirus DNA was detected in brain tissue with a generic herpesvirus polymerase chain reaction. Sanger sequencing demonstrated 100% and 98% sequence homology to sphenicid alphaherpesvirus 1 and penguin herpesvirus 2, respectively. In situ hybridization demonstrated large amounts of herpesvirus nucleic acid in intranuclear inclusions and neuronal nuclei. Combined histology, polymerase chain reaction, Sanger sequencing, and in situ hybridization results were most consistent with herpesviral encephalitis, most likely caused by sphenicid alphaherpesvirus 1. To our knowledge, this is the first report of a herpesvirus infection causing encephalitis in a penguin and the first report of herpesvirus in this species.

A novel herpesvirus in a white stork associated with splenic and hepatic necrosis

We identified a novel herpesvirus in a captive juvenile white stork (Ciconia ciconia) that experienced progressive weight loss followed by death. Histologic findings included severe splenic and hepatic necrosis, and intranuclear inclusion bodies in hepatocytes and unidentified splenic cells. The virus was amplified, sequenced, and subsequently accessioned as Ciconiid alphaherpesvirus 1. Phylogenetic analysis was performed and revealed that this virus is more closely related to mammalian herpesviruses than those within the genus Mardivirus. Additional sequence of viruses in this area may elucidate the ancestral virus that jumped from reptilian to mammalian hosts.

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.

Detection and Phylogenetic Analysis of Herpesviruses Detected in Wild Owls in Slovenia

Herpesvirus (HV) was detected using PCR in the organs of eight of 55 wild owls (14.5%) from seven species that were found dead in various locations in Slovenia between 1995 and 2015. HV was detected in three species: the Eurasian eagle owl (Bubo bubo), Ural owl (Strix uralensis), and long-eared owl (Asio otus). Phylogenetic analysis of partial DNA polymerase gene nucleotide sequences showed that the detected HVs are similar to the avian and mammal alphaherpesviruses. Two sequences were very similar to known bird HV sequences. One sequence was identical to the columbid herpesvirus 1 (CoHV1) sequence, and the other was very similar to the gallid herpesvirus 2 (GaHV2) sequence. The phylogenetic tree revealed a lower similarity of the other six analyzed Slovenian sequences with the sequences of alphaherpesviruses of birds and mammals. This is the first study to report the detection of different HVs in owls.

Physiological costs of infection: herpesvirus replication is linked to blood oxidative stress in equids

Viruses may have a dramatic impact on the health of their animal hosts. The patho-physiological mechanisms underlying viral infections in animals are, however, not well understood. It is increasingly recognized that oxidative stress may be a major physiological cost of viral infections. Here we compare three blood-based markers of oxidative status in herpes positive and negative individuals of the domestic horse (Equus ferus caballus) and of both captive and free-ranging Mongolian khulan (Equus hemionus hemionus) and plains zebra (Equus quagga). Herpes positive free-ranging animals had significantly more protein oxidative damage and lower glutathione peroxidase (antioxidant enzyme) than negative ones, providing correlative support for a link between oxidative stress and herpesvirus infection in free-living equids. Conversely, we found weak evidence for oxidative stress in herpes positive captive animals. Hence our work indicates that environment (captive versus free living) might affect the physiological response of equids to herpesvirus infection. The Mongolian khulan and the plains zebra are currently classified as near threatened by the International Union for Conservation of Nature. Thus, understanding health impacts of pathogens on these species is critical to maintaining viable captive and wild populations.

A RETROSPECTIVE SUMMARY OF RAPTOR MORTALITY IN ONTARIO, CANADA (1991-2014), INCLUDING THE EFFECTS OF WEST NILE VIRUS

The causes of mortality of free-ranging raptors range from anthropogenic (e.g., trauma) to dynamic environmental conditions that may affect habitat suitability and prey availability. The province of Ontario, Canada, is vulnerable to anthropogenic and environmental changes because of its northern latitudes and expanding human populations, both of which may impact wildlife. We retrospectively evaluated diagnostic data from raptors submitted to the Ontario/Nunavut node of the Canadian Wildlife Health Cooperative (CWHC) from 1991 to 2014 ( n=1,448). Submissions encompassed 29 species, most commonly the Red-tailed Hawk ( Buteo jamaicensis; n=308) and Great Horned Owl ( Bubo virginianus; n=237). Trauma ( n=716) accounted for the majority of deaths among all species, followed by emaciation ( n=241). Traumatic deaths were most commonly attributed to collisions with stationary objects, and the odds of a diagnosis of trauma were significantly higher in adult versus immature raptors. The odds of being diagnosed with emaciation were significantly higher in males than in females but not in any age class or season. Mortality was less commonly attributed to infectious diseases ( n=214), for which West Nile virus (WNV) was the most common etiology, making up 53.1% of infectious diagnoses after its 2001 arrival in Ontario. The odds of a raptor being diagnosed with an infectious disease were significantly greater in summer and fall versus spring. Immature Red-tailed Hawks had significantly greater odds of being diagnosed with WNV compared to adults. These results reveal that human- and potentially environmentally-associated deaths (e.g., trauma and emaciation, respectively) are commonly diagnosed among Ontario raptors submitted to the CWHC. Infectious diseases are less commonly diagnosed, but WNV may have underlying, ongoing impacts on the health of some raptor species.

Oxidative stress biomarkers are associated with visible clinical signs of a disease in frigatebird nestlings

Infectious diseases are one of the most common threats for both domestic and wild animals, but little is known about the effects on the physiological condition and survival of wild animals. Here, we have tested for the first time in a wild vertebrate facing a viral disease possibly due to herpesvirus (i) whether nestlings with either low levels of oxidative damage or high levels of antioxidant protection are less susceptible to develop visible clinical signs, (ii) whether the disease is associated with the nestlings’ oxidative status, (iii) whether the association between the disease and oxidative status is similar between males and females (iv), and whether cloacal and tracheal swabs might be used to detect herpesvirus. To address our questions, we took advantage of a population of Magnificent frigatebirds (Fregata magnificens) whose nestlings have experienced high mortality rates in recent times. Our work shows that (i) blood lipid oxidative damage is associated with observable clinical signs and survival probabilities of nestling frigatebirds, and (ii) that high glutathione levels in red blood cells are associated with the emergence of visible clinical signs of the disease. Our work provides evidence that differences in the oxidative status of nestlings might underlie individual health and survival.

PREVALENCE OF COLUMBID HERPESVIRUS INFECTION IN FERAL PIGEONS FROM NEW SOUTH WALES AND VICTORIA, AUSTRALIA, WITH SPILLOVER INTO A WILD POWERFUL OWL (NINOX STRUENA)

Columbid herpesvirus-1 (CoHV-1) is widespread in feral pigeons in North America and Europe. We used a PCR assay to detect CoHV-1 DNA in oral and cloacal tissues and oral swabs from naturally infected pigeons. Fifty-three feral pigeons from five flocks in Australia (n=3 from south-central Victoria and n=2 from Sydney) were examined for CoHV-1 DNA. We detected CoHV-1 DNA in oral mucosa and cloacal mucosa, with higher concentrations in the oral mucosa. The sensitivity of testing oral swabs was the same as testing the tissue, indicating that testing of oral swabs from live birds is an effective means of screening flocks for CoHV-1 infection. Infection was found in all five of the flocks examined and the prevalence of infection ranged from 70% to100%. Most positive birds could be detected with a single-amplification PCR, but a nested amplification was required to detect others. Oral swabs from Australian native doves and pigeons (n=18) and the introduced Collared Dove (Streptopelia chinensis; n=2) were also tested by the nested PCR and all were negative for CoHV-1 DNA. We describe a fatal infection of CoHV-1 in a wild Powerful Owl (Ninox strenua) that was observed feeding on feral pigeons. This is the first known case of CoHV-1 causing death in a wild bird of prey in Australia. Our data suggest that CoHV-1 is widespread in feral pigeon flocks in Australia but we did not find it in native doves and pigeons. Spillover into native avian predator species may be occurring.

Identification of the Nuclear Localization Signal Region of Duck Enteritis Virus UL14 and Its Interaction with VP16

OBJECT

Duck enteritis virus (DEV) is a member of the Alphaherpesvirinae viruses. VP16 and pUL14 are both predicted to be tegument proteins of DEV.

METHODS

An indirect immunofluorescence assay (IFA) was performed for preliminary analysis of the colocalization of pUL14 and VP16, which detected their subcellular localization in duck embryo fibroblasts (DEFs) during virus replication. The coexpression of pUL14 and VP16 was detected in transfected DEFs. A bimolecular fluorescence complementation (BiFC) assay was used to confirm a direct interaction between pUL14 and VP16. To better characterize the nuclear localization domain of pUL14, we designed a series of deletion mutants and transfected them with VP16.

RESULTS

Our IFA findings indicated that pUL14 binds to VP16 in the cytoplasm and that pUL14 leads VP16 import into the nucleus during DEV replication. The BiFC assay revealed the presence of pUL14 and VP16 complexes. Furthermore, 1-98 amino acid (aa) at the N-terminus of pUL14 played a role in the nuclear localization signal (NLS) region and promoted translocation of VP16 into the nucleus to complete the virus life cycle.

CONCLUSIONS

Our findings indicated that pUL14 could transport VP16 into the nucleus and that the N-terminal 1-98 aa may contain the NLS domain of pUL14.

Systemic Clinical and Metabolic Diseases

Like other animals pet and companion birds are also prone to systemic illness. This is presented in the form of certain clinical signs and symptoms which is known as “ sick-bird syndrome.”

Outbreak of Herpesviral Conjunctivitis and Respiratory Disease in Gouldian Finches

An outbreak of tracheitis, sinusitis, and conjunctivitis, originating in recently imported birds, caused high morbidity and mortality in a flock of finches in Central Illinois. Although several species were present, Gouldian finches ( Erythrura [Chloebia] gouldiae) were most commonly and severely affected. Birds submitted for necropsy displayed microscopic lesions characteristic of herpesviral infection, including epithelial cytomegaly and karyomegaly with basophilic, intranuclear inclusion bodies in the nasopharynx, sinuses, trachea, parabronchi, conjunctiva, and occasionally the lacrimal gland or proximal proventricular glands. Viral particles consistent with herpesvirus were visualized within affected epithelial cells with electron microscopy. Based on a partial sequence of the viral DNA polymerase gene, this virus was found to be identical to a herpesvirus previously implicated in a similar outbreak in Canada and is most likely an alphaherpesvirus.

Oxidative stress favours herpes virus infection in vertebrates: a meta-analysis

Herpes viruses are responsible for a variety of pathological effects in humans and in both wild and domestic animals. One mechanism that has been proposed to facilitate replication and activity of herpes viruses is oxidative stress (OS). We used meta-analytical techniques to test the hypotheses that (1) herpes virus infection causes OS and (2) supplementation of antioxidants reduces virus load, indicating that replication is favoured by a state of OS. Results based on studies on mammals, including humans, and birds show that (1) OS is indeed increased by herpes virus infection across multiple tissues and species, (2) biomarkers of OS may change differently between tissues, and (3) the effect size does not differ among different virus strains. In addition, the increase of oxidative damage in blood (tissue commonly available in ecological studies) was similar to that in the tissues most sensitive to the herpes virus. Our results also show that administration of antioxidants reduces virus yield, indicating that a condition of OS is favorable for the viral replication. In addition, some antioxidants may be more efficient than others in reducing herpes virus yield. Our results point to a potential mechanism linking herpes virus infection to individual health status.

Antiviral Activity of Resveratrol against Human and Animal Viruses

Resveratrol is a potent polyphenolic compound that is being extensively studied in the amelioration of viral infections both in vitro and in vivo. Its antioxidant effect is mainly elicited through inhibition of important gene pathways like the NF-κβ pathway, while its antiviral effects are associated with inhibitions of viral replication, protein synthesis, gene expression, and nucleic acid synthesis. Although the beneficial roles of resveratrol in several viral diseases have been well documented, a few adverse effects have been reported as well. This review highlights the antiviral mechanisms of resveratrol in human and animal viral infections and how some of these effects are associated with the antioxidant properties of the compound.

Herpesvirus-like respiratory infection in African penguins Spheniscus demersus admitted to a rehabilitation centre

Rehabilitation is an important strategy for the conservation of the Endangered African penguin Spheniscus demersus, and disease has been raised as a concern in the management of the species, both in the wild and in rehabilitation centres. We report 8 cases of herpesvirus-like respiratory infection in African penguin chicks undergoing rehabilitation between 2010 and 2013 at a facility in Cape Town, South Africa. Infection was confirmed through the identification of viral inclusions in the tracheal epithelium and demonstration of particles consistent with herpesvirus by electron microscopy, whereas virus isolation in eggs, serology and PCR testing failed to detect the virus. Only penguin chicks were affected; they were in poor body condition, and in 2 cases infection occurred prior to admission to the rehabilitation centre. The role played by the herpesvirus-like infection in the overall respiratory disease syndrome is uncertain, due to identification of lesions in only a small proportion of the chicks as well as to the occurrence of other concurrent pathological processes. Further studies are advised to characterise the specific virus involved through the development of sensitive diagnostic methods and to clarify the epidemiology and significance of these infections in wild African penguins.

Inhibitory effect of resveratrol against duck enteritis virus in vitro

Duck viral enteritis (DVE) is an acute, contagious herpesvirus infection of ducks, geese, and swans of all ages and species. This disease has been responsible for significant economic losses in domestic and wild waterfowl as a result of mortality, and decreased egg production. Resveratrol is a naturally occurring phytoalexin in specific plants and exhibits inhibitory activity against many kinds of virus. In this paper, resveratrol was found to inhibit duck enteritis virus (DEV) replication in a dose-dependent manner, with a 50% inhibition concentration of 3.85 μg/mL. The inhibition in virus multiplication in the presence of resveratrol was not attributed to direct inactivation or inhibition of virus attachment to the host cells, but to the inhibition of viral multiplication in host cells. The assay of the time of addition limited the drug effect during the first 8 h of infection. This conclusion was supported by the ultrastructure images of the early stage of DEV infection, which showed that the replication of virus nucleic acid and the formation of the capsid in the cell nucleus were suppressed. In the indirect immunofluorescence assay, proteins expression in DEV infected duck embryo fibroblasts (DEFs) within 24 h post-infection (p.i.) was also effectively suppressed by resveratrol. In summary, the resveratrol has a good activity against DEV infection in vitro, which could be attributed to that fact that several essential immediate early viral proteins for virus replication were impacted by resveratrol.

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.

Haemorrhagic enteritis associated with herpesvirus in storks

Herpesvirus infection was diagnosed histologically and electron microscopically in white storks (Ciconia ciconia) and abdim storks (Ciconia abdimi). The consistent lesions of herpesvirus infection were haemorrhagic enteritis, with a slight mononuclear cellular infiltrate, dilatation of the crypts lined by a flat epithelium, necrotic foci in the spleen, and focal or scattered coagulative necrosis in the liver without cellular reaction. Intranuclear inclusion bodies were observed in epithelial cells, endothelial cells, lymphocytes, macrophages/monocytes, fibroblasts and smooth muscle cells in digestive tract, spleen, liver, ovary, oviduct and lung. Ultrastructurally, characteristic herpesvirus replication sites were observed in the nuclei of infected cells, with clusters of intracytoplasmic virions and associated structures, intranuclear tubular structures and filamentous aggregates.

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

Differentiation of herpesvirus isolates has been performed mostly on the basis of biological properties and serology. In this study, 15 herpesvirus isolates from different species of birds were compared by restriction endonuclease analysis of genomic DNA. All herpesviruses were isolated in Europe or are used as vaccine viruses there. The isolates could be differentiated into seven groups based on restriction patterns. The largest group contains isolates from passeriform and psittacine birds and could further be subdivided into four subgroups. Two other groups are represented by herpesvirus isolates of quail and crane, and by isolates of pigeon and owl. Duck plague virus, herpesvirus of turkey, infectious laryngotracheitis virus and a herpesvirus isolate from tragopan all exhibited distinct restriction patterns. In general, our results parallel earlier cross-neutralization studies and yield additional, more detailed information on the relationship between different herpesvirus isolates of birds.

Development and application of an indirect immunohistochemical method for the detection of duck plague virus vaccine antigens in paraffin sections and localization in the vaccinated duckling tissues

The objective of the present study was to develop and apply a streptavidin-alkaline phosphatase labeling system of indirect immunohistochemistry (SP-IHC) to detect antigenic distribution and localization regularity of duck plague virus (DPV) vaccine antigens in paraformaldehyde-fixed paraffin-embedded tissues of experimentally vaccinated ducklings. Male New Zealand rabbits were immunized with purified DPV antigens, which were engaged by a combination of differential centrifugation and sucrose-density gradient ultracentrifugation. The rabbit anti-DPV polyclonal antibodies were purified and used as the primary antibodies. Forty-eight 28-d-old DPV-free Pekin ducklings were subcutaneously inoculated with attenuated DPV vaccine in the immunization group and sterile PBS in the control group. The tissues were collected at sequential time points between 4 h and 18 wk postvaccination (PV) and were prepared for SP-IHC observation. The presence of DPV-specific antigens was first observed in the liver and spleen at 12 h PV; in the bursa of Fabricius, thymus, Harderian gland, esophagus, and intestinal tract at 1 d PV; and in the heart, lung, kidney, pancreas, and brain at 3 d PV. The positive staining reaction could be detected in the vaccinated duckling tissues until 18 wk PV, and no positive staining cells could be observed in the controls. The highest levels of positive staining reaction were found in the liver, spleen, bursa of Fabricius, thymus, and intestinal tract, whereas a few DPV vaccine antigens were distributed in the heart, pancreas, and esophagus. The target cells had a ubiquitous distribution, especially in the mucosal epithelial cells, lamina propria cells, macrophages, hepatocytes, and lymphocytes, which served as the principal sites for antigen localization. These findings demonstrated that SP-IHC was a reliable method for detecting antigenic distribution and localization regularity of DPV vaccine antigens in routine paraffin sections. The present study may be useful for describing proliferation and distribution regularity of DPV vaccine in the vaccinated duckling tissues and enhance further studies and clinical application of attenuated DPV vaccine.

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.

Polyclonal antibody against the DPV UL46M protein can be a diagnostic candidate

Background

The duck plague virus (DPV) UL46 protein (VP11/12) is a 739-amino acid tegument protein encoded by the UL46 gene. We analyzed the amino acid sequence of UL46 using bioinformatics tools and defined the main antigenic domains to be between nucleotides 700-2,220 in the UL46 sequence. This region was designated UL46M. The DPV UL46 and UL46M genes were both expressed in Escherichia coli Rosetta (DE3) induced by isopropy1-β-D-thiogalactopyranoside (IPTG) following polymerase chain reaction (PCR) amplification and subcloning into the prokaryotic expression vector pET32a(+). The recombinant proteins were purified using a Ni-NTA spin column and used to generate the polyclonal antibody against UL46 and UL46M in New Zealand white rabbits. The titer was then tested using enzyme-linked immunosorbent assay (ELISA) and agar diffusion reaction, and the specificity was tested by western blot analysis. Subsequently, we established Dot-ELISA using the polyclonal antibody and applied it to DPV detection.

Results

In our study, the DPV UL46M fusion protein, with a relative molecular mass of 79 kDa, was expressed in E. coli Rosetta (DE3). Expression of the full UL46 gene failed, which was consistent with the results from the bioinformatic analysis. The expressed product was directly purified using Ni-NTA spin column to prepare the polyclonal antibody against UL46M. The titer of the anti-UL46M antisera was over 1:819,200 as determined by ELISA and 1:8 by agar diffusion reaction. Dot-ELISA was used to detect DPV using a 1:60 dilution of anti-UL46M IgG and a 1:5,000 dilution of horseradish peroxidase (HRP)-labeled goat anti-rabbit IgG.

Conclusions

The anti-UL46M polyclonal antibody reported here specifically identifies DPV, and therefore, it is a promising diagnostic tool for DPV detection in animals. UL46M and the anti-UL46M antibody can be used for further clinical examination and research of DPV.

Rapid detection of infectious laryngotracheitis virus isolates by loop-mediated isothermal amplification

The objective of this study was to develop and evaluate a loop-mediated isothermal amplification (LAMP) method to detect infectious laryngotracheitis virus (ILTV) from commercial broiler and layer flocks in southern China. A set of six specific primers was designed to recognize six distinct genomic sequences of thymidine kinase (TK) from ILTV. The entire assay duration was recorded at 40 min under isothermal condition at 63.5 degrees C. The amplified products were analyzed by electrophoresis and visual judgment by the SYBR Green I dyeing. LAMP assay was 10-fold more sensitive than the routine PCR assay, with a detection limit of 46 copies per reaction. In detecting ILTV, the LAMP assay detected all 5 strains previously isolated, did not cross-react with other avian pathogens, and obtained a 100% sensitivity in 43 positive clinical samples with reference to virus isolation. Therefore, the LAMP assay may be a good alternative method for specific diagnosis of ILTV infection in primary care facilities, and in less well-equipped laboratories.

Development of TaqMan MGB fluorescent real-time PCR assay for the detection of anatid herpesvirus 1

Background

Anatid herpesvirus 1 (AHV-1) is an alphaherpesvirus associated with latent infection and mortality in ducks and geese and is currently affecting the world-wide waterfowl production severely. Here we describe a fluorescent quantitative real-time PCR (FQ-PCR) method developed for fast measurement of AHV-1 DNA based on TaqMan MGB technology.

Results

The detection limit of the assay was 1 × 10¹ standard DNA copies, with a sensitivity of 2 logs higher than that of the conventional gel-based PCR assay targeting the same gene. The real-time PCR was reproducible, as shown by satisfactory low intra-assay and inter-assay coefficients of variation.

Conclusion

The high sensitivity, specificity, simplicity and reproducibility of the AHV-1 fluorogenic PCR assay, combined with its wide dynamic range and high throughput, make this method suitable for a broad spectrum of AHV-1 etiologically related application.

Anatid herpesvirus 1 CH virulent strain induces syncytium and apoptosis in duck embryo fibroblast cultures

Anatid herpesvirus 1 (AHV-1) CH virulent strain was first isolated from an infected duck and it was found that this virus strain could induce cytopathic effect (CPE) in duck embryo fibroblast (DEF). Following AHV-1 infection, DEF showed morphological changes such as cell rounding, improved refractivity and detachment from the culture surface. However, its pathological characteristics were not adequately known. Related studies were performed and the results showed that syncytium formation could be observed as the other type of CPE in AHV-1 infection. Hematoxylin-eosin staining and 4', 6-diamidino-2-phenylindole (DAPI) staining of infected DEF were each used to visualize the shape and distribution of chromatin within nuclei and nuclear fragmentation was observed. Chromatin condensation and margination, as well as formation of apoptotic bodies were observed by transmission electron microscopy (TEM). DNA ladder formation was detected in AHV-1 infected cells and apoptosis of the infected DEF was also detected by flow cytometry analysis of Annexin V-FITC/PI staining method. Therefore, it was suggested that AHV-1 virulent strain can induce syncytium and apoptosis in DEF. Syncytium formation and apoptosis observed in this study may contribute to the elucidation of AHV-1 pathogenesis.

An outbreak of Pacheco's parrot disease in a psittacine bird collection and an attempt to control it by vaccination

An outbreak of Pacheco's parrot disease (PPD) is described in a psittacine bird collection of a municipal ornithological garden. A herpes virus was isolated and judged to be the causative agent from the mortality recorded. A formaldehyde/heat-inactivated experimental vaccine was prepared from polyethyleneglycol purified virus. The vaccine was locally and systemically well tolerated by all birds. Seroconversion was demonstrated by neutralization tests in most of the vaccinated birds of the genera Ara, Anodorhynchus and Probosciger.

Molecular analysis of duck enteritis virus US3, US4, and US5 gene

Here, we first present unique short (US)3, US4, and US5 gene sequences, with analysis, of duck enteritis virus (DEV) vaccine strain C-KCE. The assembled sequence comprises 5,742 nucleotides, which are amplified from the DEV genome by single oligonucleotide-nested polymerase chain reaction with primers designed according to our previous acquired sequence deposited in GenBank (accession no. EF619046). The predicted gene arrangement is colinear with the alphaherpesvirus herpes simplex virus within the US region. The N-glycosylated sites, signal peptide, transmembrane helices, RNA polymerase II transcriptional control elements, and polyadenylation signal, were predicted with network prediction programs. Phylogenetic analysis of the three putative proteins revealed that they had a close evolutionary relationship with the subfamily of Alphaherpesvirinae.

Purification of anatid herpesvirus 1 particles by tangential-flow ultrafiltration and sucrose gradient ultracentrifugation

Anatid herpesvirus 1 (AHV-1) infection causes substantial economic losses to the world-wide waterfowl production. However, little is known about the efficient method used to study the purification of AHV-1 and the negative staining morphology of the purified virus particles. This lack of knowledge is one of the important factors that have affected the progress of research studies on AHV-1 molecular virology to such an extent that they are lagging far behind those on other members of the same family Herpesviridae. Therefore, an efficient method for purifying AHV-1 from cell-culture medium has been developed. Abundant AHV-1 particles, whose morphological features match those of herpesvirus, were obtained by using the following procedures: (1) conventional differential centrifugation for removal of debris after cell disruption, (2) tangential-flow ultrafiltration coupled with sucrose density gradient ultracentrifugation for isolation of the virus, and (3) conventional differential ultracentrifugation for virus concentration. The purified AHV-1 particles were subjected to transmission electron microscopy (TEM), infectivity and recovery tests, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), immunoblotting assay, and agar gel diffusion test (AGDT). The results of examinations revealed that purified AHV-1 particles were free of visible contamination or degradation. The purified AHV-1 particles were biologically active and were successful in initiating infection upon inoculation into susceptible duck embryo fibroblast. The procedures are reliable technically and feasible for purification of large volumes of viruses.

Comparative analysis of the genes UL1 through UL7 of the duck enteritis virus and other herpesviruses of the subfamily Alphaherpesvirinae

The nucleotide sequences of eight open reading frames (ORFs) located at the 5' end of the unique long region of the duck enteritis virus (DEV) Clone-03 strain were determined. The genes identified were designated UL1, UL2, UL3, UL4, UL5, UL6 and UL7 homologues of the herpes simplex virus 1 (HSV-1). The DEV UL3.5 located between UL3 and UL4 had no homologue in the HSV-1. The arrangement and transcription orientation of the eight genes were collinear with their homologues in the HSV-1. Phylogenetic trees were constructed based on the alignments of the deduced amino acids of eight proteins with their homologues in 12 alpha-herpesviruses. In the UL1, UL3, UL3.5, UL5 and UL7 proteins trees, the branches were more closely related to the genus Mardivirus. However, the UL2, UL4, and UL6 proteins phylogenetic trees indicated a large distance from Mardivirus, indicating that the DEV evolved differently from other viruses in the subfamily Alphaherpesvirinae and formed a single branch within this subfamily.

Molecular analysis of US10, S3, and US2 in duck enteritis virus

A 4554-bp fragment was amplified from the DEV C-KCE vaccine strain by single oligonucleotide nested polymerase chain reaction with partially known sequences for the DEV US1 and US10 genes. Three open reading frames containing the genes encoding US10, S3, and US2 were predicted using the Editseq program (DNAStar). The S3 and US2 genes have the same transcription orientation but are oriented head-to-head with respect to US10. The promoters and polyadenylation signals were predicted. Two poly A sequences were predicted in S3, but none were predicted in US2. These results provide partial sequence of US region for the physical map of the DEV genome. Phylogenetic analysis suggests that the DEV C-KCE strain is more closely related to Mardivirus in the alphaherpesvirus subfamily of the Herpesviridae.

Rapid diagnosis of duck plagues virus infection by loop-mediated isothermal amplification

Duck virus enteritis is a serious disease among farmed and free-living ducks (Anatidae) and a constant threat to the commercial duck industry in China. In this study, a loop-mediated isothermal amplification (LAMP) assay was developed to rapidly detect and diagnose duck plague virus (DPV) in both farmed and wild waterfowl, and compared with polymerase chain reaction (PCR) method and real-time PCR method in accuracy, sensitivity and specificity. A set of four specific primers was successfully designed to recognize six distinct genomic sequences of UL6 protein from DPV, including one forward inner primer, one back inner primer and two outer primers. The optimum reaction temperature and time were verified to be 61.5 degrees C and 60 min, respectively. Comparative experiments showed that LAMP assay was a simple, rapid, accurate, sensitive and specific method for detecting DPV, and was superior to PCR assay in sensitivity and specificity for DNA amplification. In addition, challenge tests indicated the newly developed LAMP method was more sensitive for the diagnosis of DPV infection than virus isolation and PCR. LAMP assay would be a good alternative method for on-farm disease diagnosis.

Molecular characterization of the herpes simplex virus 1 (HSV-1) homologues, UL25 to UL30, in duck enteritis virus (DEV)

A 16.6-kilo-base pair (kb) sequence was amplified from the duck enteritis virus (DEV) clone-03 strain genome using 'targeted gene walking polymerase chain reaction (PCR)'. Seven complete open reading frames (ORFs) were predicted, and designated herpes simplex virus 1 (HSV-1) homologues, unique long (UL) 25, UL26, UL26.5, UL27, UL28, UL29, and UL30. Sequence analysis revealed that the arrangement of seven genes in DEV clone-03 strain was collinear to that from HSV-1. In addition, mRNA transcription orientation was identical to the HSV-1 genes. While UL25, UL26, and UL26.5 shared the same poly A signal, the UL27 and UL28 genes overlapped by 211bp nucleotides and shared the same 3' transcription terminus. UL26.5, an in-frame ORF of UL26, was co-terminal with UL26 at its 3'-end. We predicted that the gene arrangement in the unique long segment of the DEV clone-03 was identical to that in HSV-1, particularly in the region from UL25 to UL30 gene. Phylogenetic trees of the putative proteins encoded by these seven genes showed that UL27, UL28, and UL30 had a close evolutionary relationship with the Mardivirus, however, the other four proteins exhibited close relationships with the Simplexvirus or Varicellovirus, indicating that the DEV clone-03 should be placed into a single cluster within the subfamily Alphaherpesvirinae.

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.

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.

Inhibition of Anatid Herpes Virus-1 replication by small interfering RNAs in cell culture system

RNA interference (RNAi) mediated by double stranded small interfering RNA (siRNA) is a novel mechanism of post-transcriptional gene silencing. It is projected as a potential tool to inhibit viral replication. In the present paper, we demonstrate the suppression of replication of an avian herpes virus (Anatid Herpes Virus-1, AHV-1) by siRNA mediated gene silencing in avian cells. The UL-6 gene of AHV-1 that codes for a protein involved in viral packaging was targeted. Both cocktail and unique siRNAs were attempted to evaluate the inhibitory potential of AHV-1 replication in duck embryo fibroblast (DEF) cell line. DEF cells were chemically transfected with different siRNAs in separate experiments followed by viral infection. The observed reduction in virus replication was evaluated by cytopathic effect, viral titration and quantitative real time PCR (QRT-PCR). Among the three siRNA targets used the unique siRNA UL-B sequence was found to be more potent in antiviral activity than the cocktail and UL6-A-siRNA sequences.