Genome sequencing of a novel variant of fowl adenovirus B reveals mosaicism in the pattern of homologous recombination events.

We determined the genomic sequence of a Ukrainian strain of fowl adenovirus B (FAdV-B). The isolate (D2453/1) shared 97.2% to 98.4% nucleotide sequence identity with other viruses belonging to the species Fowl aviadenovirus B. Marked genetic divergence was seen in the hexon, fiber, and ORF19 genes, and phylogenetic analysis suggested that recombination events had occurred in these regions. Our analysis revealed mosaicism in the recombination patterns, a finding that has also been described in the genomes of strains of FAdV-D and FAdV-E. The shared recombination breakpoints, affecting the same genomic regions in viruses belonging to different species, suggest that similar selection mechanisms are acting on the key neutralization antigens and epitopes in viruses of different FAdV species.

Herpesvirus of turkey-vectored avian influenza vaccine offers cross-protection against antigenically drifted H5Nx highly pathogenic avian influenza virus strains.

Among the different vaccines used to control highly pathogenic avian influenza, an HVT vector-based live recombinant avian influenza vaccine, expressing the haemagglutinin gene of an H5N1 HPAI virus, has been used by the poultry industry since 2012. The objective of the study presented in this paper was to test the efficacy of the commercially available HVT-based recombinant H5 vaccine against antigenically drifted H5N1, H5N8 and H5N2 HPAI virus circulating in Egypt recently. Groups of SPF chicks vaccinated at day-old with the HVT-based recombinant H5 vaccine were challenged, along with non-vaccinated controls, with 106 EID50 each of H5N1, H5N2 or H5N8 HPAI virus at 28 days of age. The birds were monitored for clinical protection and virus shedding during a 10-day postchallenge period. Clinical protection levels were 90%, 90% and 80% following challenge with the H5N1, H5N2 and H5N8 field isolates, respectively. Challenge virus shedding was significantly reduced in vaccinated groups, with up to 40%, 30% and 20% of non-shedders, and 3.8, 3.3 and 2.8 log10 reduction in the amount of excreted virus following challenge with H5N1, H5N2 and H5N8 viruses, respectively. Analyses of the amino acid sequences of the HA proteins of challenge viruses and serological relatedness with the vaccine insert revealed significant antigenic divergences between the vaccine and the challenge viruses. These results provide further evidence of the potential of HVT-based recombinant H5 vaccine to provide cross-protection against antigenically drifted HPAI H5Nx viruses with strong control on virus shedding.

Characterization of a PCV2d-2 isolate by experimental infection of pigs.

Porcine circovirus type 2 (PCV2), a highly prevalent, economically important swine pathogen is classified into different genotypes (PCV2a-f) based on phylogenetic analysis. Since the introduction of extensive vaccination programs, at least two major shifts have been observed in the prevalence of PCV2 genotypes. The first genotype shift from 2a towards 2b occurred around 2003, while in recent years, we are witnessing the second change in genotype prevalence from the predominant 2b towards 2d.In this study, a PCV2d-2 isolate was characterized as a potential challenge virus for the evaluation of PCV2 vaccine efficacy. Ten-week-old pigs carrying low to moderate levels of maternally derived antibodies to PCV2 were infected with the isolate by the nasal route. Over the next 4 weeks post-infection, the pigs were monitored for the presence of viremia, fecal virus excretion, and humoral immune responses. At the end of the post-infection observation period, samples were taken from the mediastinal and mesenteric lymph nodes of the animals and tested for viral load. The gradual depletion of maternally derived antibodies in the sera of piglets was demonstrated by ELISA and virus neutralization tests. Following experimental infection by PCV2d-2, specific IgM antibodies were first detected at 14 days post challenge (dpch), while IgG class antibodies were first detected at 21 dpch. Both viremia and virus shedding could be detected at 7 dpch, in 36 and 50% of the pigs, respectively. The proportion of shedders reached 100% by 14 dpch and remained at this level, while viremia was demonstrated in 86, 100, and 100% of the pigs at 14, 21, and 28 dpch, respectively. Both the mediastinal and mesenteric lymph nodes contained high levels of virus (7.6 and 8.5 log10 copies/mg tissue, respectively).

Survey indicates circulation of 4/91 and QX-type infectious bronchitis viruses in Hungary in 2014 - Short communication.

Understanding the epidemiology and improving vaccinal protection against the highly variable chicken infectious bronchitis virus (IBV) requires the knowledge of circulating IBV serotypes/genotypes in defined geographic areas. Accordingly, the authors initiated a survey among the major poultry producers in Hungary in order to reveal the prevailing IBV serotypes in the country. Tracheal swabs and organ samples (caecal tonsils, kidneys, and trachea) were collected from broiler, layer, and meat-type breeder flocks, and were subjected to IBV detection by virus isolation and polymerase chain reaction (PCR). The IBV-positive samples were further characterised by nucleotide sequencing and phylogenetic analysis of a portion of the S1 IBV gene. Seventeen out of the 26 submitted samples proved to be positive for IBV. Sequence analyses revealed ten 4/91 and six QX serotypes, and a single D274 type IB virus. One sample contained a mixture of QX and Massachusetts serotype viruses. Presumably most of the 4/91 and D274 type viruses were vaccine strains. The proportion of QX type viruses and their observed variation are in good agreement with the situation in a few other European countries. The detected viruses clustered largely according to their geographic origin, with a few exceptions. If updated regularly, the preliminary 'virus map' will be useful for the adjustment of vaccination protocols.

The complete genome sequence of a European goose reovirus strain.

The complete genomic sequence of a Hungarian goose orthoreovirus strain (D20/99) is reported in this study. The genome of D20/99 is 22,969 bp in length (range, 3958 bp for L1 to 1124 bp for S4) and encodes 11 putative proteins. Pairwise sequence comparisons and phylogenetic analyses indicated that D20/99 shares genetic signatures with some contemporary Chinese duck and goose reovirus strains, except for the µA, µNS and σA protein coding genes, which represented independent genetic lineages. This study implies a greater genetic diversity among waterfowl-origin orthoreoviruses than hitherto recognized.

Tembusu-like flavivirus (Perak virus) as the cause of neurological disease outbreaks in young Pekin ducks.

A neurological disease of young Pekin ducks characterized by ataxia, lameness, and paralysis was observed at several duck farms in Malaysia in 2012. Gross pathological lesions were absent or inconsistent in most of the cases, but severe and consistent microscopic lesions were found in the brain and spinal cord, characterized by non-purulent panencephalomyelitis. Several virus isolates were obtained in embryonated duck eggs and in cell cultures (Vero and DF-1) inoculated with the brain homogenates of affected ducks. After exclusion of other viruses, the isolates were identified as a flavivirus by flavivirus-specific reverse transcription-polymerase chain reaction (RT-PCR) assays. Inoculation of 2-week-old Pekin ducks with a flavivirus isolate by the subcutaneous or intramuscular route resulted in typical clinical signs and histological lesions in the brain and spinal cord. The inoculated virus was detected by RT-PCR from organ samples of ducks with clinical signs and histological lesions. With a few days delay, the disease was also observed among co-mingled contact control birds. Phylogenetic analysis of NS5 and E gene sequences proved that the isolates were representatives of a novel phylogenetic group within clade XI (Ntaya virus group) of the Flavivirus genus. This Malaysian Duck Tembusu Virus (DTMUV), named Perak virus, has moderate genomic RNA sequence similarity to a related DTMUV identified in China. In our experiment the Malaysian strain of DTMUV could be transmitted in the absence of mosquito vectors. These findings may have implications for the control and prevention of this emerging group of flaviviruses.

Clinicopathological and Molecular Investigation of Newcastle Disease Outbreaks in Vaccinated and Non-Vaccinated Broiler Chicken Flocks in Nepal.

Newcastle disease (ND) is a highly contagious viral disease caused by the paramyxovirus, which is a single-stranded ribonucleic acid (RNA) virus. This study was conducted to investigate ND outbreaks in 10 vaccinated or non-vaccinated broiler farms, collectively housing 9840 birds of various ages in the Chitwan and Nawalpur districts of Nepal from July to December 2021. Clinically, the affected birds exhibited symptoms such as limb paralysis, greenish diarrhea (seven out of ten flocks), torticollis (two out of ten flocks), inappetence, and drowsiness (ten out of ten flocks). Birds that succumbed during the clinical course underwent a necropsy for gross pathology and samples were collected for the histopathology and molecular diagnosis. The gross and microscopic examination revealed hemorrhages in the proventriculus, erosions and ulcers in the small intestine, congestion, as well as sero-mucosal hemorrhages in the trachea of affected birds, which are typical of ND. Rapid test kits further confirmed the presence of the ND virus antigen while excluding the avian influenza virus. Furthermore, M gene-based real time polymerase chain reaction (RT-PCR) was performed in the pooled samples from the affected birds and the presence of a velogenic strain of the ND virus was identified. The phylogenetic analysis of the RT-PCR positive strain based on the partial F gene nucleotide sequence revealed these strains as genotype VII.2 (formerly VIIi). The findings highlight the occurrence of clinical ND outbreaks in farms despite adherence to recommended vaccination protocols in broiler flocks, underscoring the need for a regular comprehensive investigation involving in-depth examinations of available vaccines and genetic analyses.

Genomic Epidemiology and Evolution of Fowl Adenovirus 1.

Fowl adenovirus 1 (FAdV-1) is the main cause of gizzard erosion in chickens. Whole genome sequencing and sequence analyses of 32 FAdV-1 strains from a global collection provided evidence that multiple recombination events have occurred along the entire genome. In gene-wise phylogenies, only the adenoviral pol gene formed a tree topology that corresponded to whole genome-based phylogeny. Virus genetic features that were clearly connected to gizzard erosion were not identified in our analyses. However, some genome variants tended to be more frequently identified from birds with gizzard erosion and strains isolated from healthy birds or birds with non-specific pathologies tended to form common clusters in multiple gene phylogenies. Our data show that the genetic diversity is greater, and the evolutionary mechanisms are more complex within FAdV-1 than previously thought. The implications of these findings for viral pathogenesis and epidemiology await further investigation.

Efficacy of a recombinant HVT-H5 vaccine against challenge with two genetically divergent Indonesian HPAI H5N1 strains.

The swift evolution rate of avian influenza (AI) H5N1 virus demands constant efforts to update inactivated vaccines to match antigenically with the emerging new field virus strains. Recently, a recombinant turkey herpesvirus (rHVT)-AI vaccine, rHVT-H5, expressing the HA gene of a highly pathogenic avian influenza (HPAI) H5N1 clade 2.2 A/Swan/Hungary/499/ 2006 strain inserted into FC-126 strain of HVT vector, has been developed to combat current threats in poultry industry. Here, we present the results of two trials where rHVT-H5 was tested alone or in combination with inactivated H5N1 vaccines (the latter vaccines contained antigens produced by using a clade 2.1.3 HPAI H5N1 virus [A/Ck/WestJava-Nagrak/2007] in the first trial or mixture of antigen produced by strain A/Ck/WestJava-Nagrak/2007 and A/Ck/Banten-Tangerang/2010 [bivalent vaccine] for second trial) in broiler chickens (Gallus gallus domesticus) carrying maternally derived antibodies to H5N1 and then challenged with Indonesian HPAI H5N1 field isolates. The effectiveness of vaccination was evaluated on the basis of clinical protection (morbidity and mortality) and measurement of virus shedding after challenge. Immune response to vaccination was followed by serology. In the first experiment, chickens were vaccinated at the day of hatch with rHVT-H5 alone (Group 1) or combined with inactivated vaccine at day old (Group 2) or at 10 days of age (Group 3). The chickens along with nonvaccinated hatch-mates were challenged at 28 days of age with the HPAI H5N1 field isolate dade 2.1.3 A/Chicken/WestJava-Subang/29/2007. Eighty, 100%, and 80% clinical protection was recorded in Group 1, 2, and 3, respectively. A similar experiment was performed a second time, but the chicks in Group 3 received the inactivated vaccine earlier, at 7 days of age. Challenge was performed at 28 days of age using a different H5N1 isolate, clade 2.1.3 A/Ck/Purwakarta-Cilingga/142/10. Clinical protection achieved in the second trial was 95%, 75%, and 90% in Group 1, 2, and 3, respectively. Shedding of challenge virus was significantly lower in the vaccinated groups compared with controls in both experiments. Vaccinated birds developed hemagglutination inhibition antibody response to H5N1 by the time of challenge. These experiments confirmed that the rHVT-H5 vaccine applied alone or in combination with inactivated H5N1 vaccines could provide high level (> 80%) clinical protection against divergent HPAI H5N1 field isolates after single immunization by 4 wk of age and a significant reduction in the excretion of challenge virus.

Research Note: "Hidden" infectious bursal disease virus infections in Central Europe.

Infectious bursal disease virus (IBDV) is a major threat to the poultry industry globally, represented by a variety of genetic, pathogenic, and antigenic variants. The recognition of the infection may be challenging due to several factors, as the virulence of the strain, age, and immune status of the birds at infection, to name the most important ones. Here we report about the molecular typing of IBDVs detected over the recent years in Central Europe. The results revealed the diversity of IBDV in the region, that is, very virulent strains being present in all four involved countries, the successive detection of a recently described reassortant variant in the Czech Republic, and the "rediscovery" of a subclinical pathotype virus in Hungary. These findings highlight the need for monitoring the flocks regularly not only by evaluating the production parameters but to look specifically for the occurrence of IBDV and adjust the control measures according to the results.

Identification of the main genetic clusters of avian reoviruses from a global strain collection.

Introduction: Avian reoviruses (ARV), an important pathogen of poultry, have received increasing interest lately due to their widespread occurrence, recognized genetic diversity, and association to defined disease conditions or being present as co-infecting agents. The efficient control measures require the characterization of the available virus strains. Methods: The present study describes an ARV collection comprising over 200 isolates from diagnostic samples collected over a decade from 34 countries worldwide. One hundred and thirty-six ARV isolates were characterized based on σC sequences. Results and discussion: The samples represented not only arthritis/tenosynovitis and runting-stunting syndrome, but also respiratory symptoms, egg production problems, and undefined disease conditions accompanied with increased mortality, and were obtained from broiler, layer or breeder flocks. In 31 percent of the cases other viral or bacterial agents were demonstrated besides ARV. The most frequent co-infectious agent was infectious bronchitis virus followed by infectious bursal disease virus and adenoviruses. All isolates could be classified in one of the major genetic clusters, although we observed marked discrepancies in the genotyping systems currently in use, a finding that made genotype assignment challenging. Reovirus related clinical symptoms could not be unequivocally connected to any particular virus strains belonging to a specific genetic group, suggesting the lack of strict association between disease forms of ARV infection and the investigated genetic features of ARV strains. Also, large genetic differences were seen between field and vaccine strains. The presented findings reinforce the need to establish a uniform, widely accepted molecular classification scheme for ARV and further, highlight the need for ARV strain identification to support more efficient control measures.

Efficacy of live attenuated, vector and immune complex infectious bursal disease virus (IBDV) vaccines in preventing field strain bursa colonization: A European multicentric study.

Infectious bursal disease virus (IBDV) is among the most relevant and widespread immunosuppressive agents, which can severely damage poultry farming by causing direct losses, predisposing the host to secondary diseases and reducing the efficacy of vaccination protocols against other infections. IBDV has thus been the object of intense control activities, largely based on routine vaccination. However, the need for protecting animals from the infection in the first period of the production cycle, when the bursa susceptibility is higher, clashes with the blanketing effect of maternally derived antibodies. To overcome this issue, other strategies have been developed besides live attenuated vaccines, including vector vaccines and immune complex (icx) ones. The present study aims to investigate, in field conditions, the efficacy of these approaches in preventing IBDV infection in laying chickens vaccinated with either live attenuated, vector or immune complex (icx) vaccines. For this purpose, a multicentric study involving 481 farms located in 11 European countries was organized and IBDV infection diagnosis and strain characterization was performed at 6 weeks of age using a molecular approach. Vaccine strains were commonly detected in flocks vaccinated with live or icx vaccines. However, a significantly higher number of field strains (characterized as very virulent IBDVs) was detected in flocks vaccinated with vector vaccines, suggesting their lower capability of preventing bursal colonization. Different from vector vaccines, live and icx ones have a marked bursal tropism. It can thus be speculated that vaccine virus replication in these sites could limit vvIBDV replication by direct competition or because of a more effective activation of innate immunity. Although such different behavior doesn't necessarily affect clinical protection, further studies should be performed to evaluate if vvIBDV replication could still be associated with subclinical losses and/or for viral circulation in a "vaccinated environment" could drive viral evolution and favor the emergence of vaccine-escape variants.

The genomic constellation of a novel avian orthoreovirus strain associated with runting-stunting syndrome in broilers.

Avian orthoreoviruses (ARVs) are responsible for considerable economic losses in broiler chickens; yet, the genetic characterization of most ARV strains is limited to a few genes, and the full coding region has been determined for only S1133 and 138, two ARV strains associated with tenosynovitis. Recently, in parts of the United States, ARVs with novel neutralization antigen type were isolated from chickens afflicted with runting-stunting syndrome. One such strain, AVS-B, was selected for full genome sequencing and phylogenetic analysis. The complete genome was 23,494 bp in size and included 12 open reading frames. The lengths of the coding regions, as well as those of the 5' and 3' ends, were fairly well conserved between AVS-B and other reference strains. In pairwise comparisons to the S1133 and 138 strains, the AVS-B strain shared a wide range of sequence identities along each genome segment, i.e., a range of 54-55% for the σC coding region of S1 genome segment and 91-93% for the S2 genome segment. Phylogenetic analyses of individual genes of AVS-B did not identify any single common ancestor among more completely characterized ARV strains for which sequence data are available. One exception to this lack of identity was strain 138, which shared 90-93% nt identity with AVS-B along seven of ten genome segments; only M2, M3, and S1 segments of these strains shared lower sequence identities. Collectively, our analyses indicated that multiple reassortment events and strong divergence caused by the accumulation of point mutations could have led to the observed assortment and genetic heterogeneity of the AVS-B genome.

Efficacy of a Turkey Herpesvirus Vectored Newcastle Disease Vaccine against Genotype VII.1.1 Virus: Challenge Route Affects Shedding Pattern.

The control of Newcastle disease (ND) highly relies on vaccination. Immunity provided by a ND vaccine can be characterized by measuring the level of clinical protection and reduction in challenge virus shedding. The extent of shedding depends a lot on the characteristics of vaccine used and the quality of vaccination, but influenced also by the genotype of the challenge virus. We demonstrated that vaccination of SPF chicks with recombinant herpesvirus of turkey expressing the F-gene of genotype I ND virus (rHVT-ND) provided complete clinical protection against heterologous genotype VII.1.1 ND virus strain and reduced challenge virus shedding significantly. 100% of clinical protection was achieved already by 3 weeks of age, irrespective of the challenge route (intra-muscular or intra-nasal) and vaccination blocked cloacal shedding almost completely. Interestingly, oro-nasal shedding was different in the two challenge routes: less efficiently controlled following intra-nasal than intra-muscular challenge. Differences in the shedding pattern between the two challenge routes indicate that rHVT-ND vaccine induces strong systemic immunity, that is capable to control challenge virus dissemination in the body (no cloacal shedding), even when it is a heterologous strain, but less efficiently, although highly significantly (p < 0.001) suppresses the local replication of the challenge virus in the upper respiratory mucosa and consequent oro-nasal shedding.

A Case of Infectious Laryngotracheitis in an Organic Broiler Chicken Farm in Greece.

Infectious laryngotracheitis is an economically significant viral disease of chickens, that mainly affects the upper respiratory tract, and is present worldwide. This case reports the first outbreak of infectious laryngotracheitis in a four-week-old organic broiler farm and surrounding flocks in Greece, with typical clinical symptoms and lesions, allegedly provoked by a wild strain of infectious laryngotracheitis virus. Our findings contradict the general perception indicating that the disease appears mainly in older birds and that vaccine strains are the primary cause of infectious laryngotracheitis outbreaks in most continents. A recombinant vectored vaccine was administered, supplementary to biosecurity measures, containing the viral spread. The responsible strain was potentially circulating in the area; therefore, an industry-wide holistic approach was applied, including the vaccination of neighboring broilers and breeders with the same vaccine, the rapid molecular diagnosis of the disease, and strict biosecurity protocols. The results of this holistic effort were effective because, following the application of vaccine and management protocols, manifestations of the disease in regional flocks dropped significantly, and there was no recurrence to date. These findings suggest that vaccination protocols should be modified, especially for organic broilers, to include vaccination against infectious laryngotracheitis.

Occurrence and spread of a reassortant very virulent genotype of infectious bursal disease virus with altered VP2 amino acid profile and pathogenicity in some European countries.

Reassortant strains of Infectious Bursal Disease Virus (IBDV) were detected in commercial broiler flocks in the Netherlands, Belgium, Denmark, Czech Republic and Germany and in layers and organic broilers in Sweden in the period of 2017-19. Genetic analysis, based on hypervariable region of VP2 gene showed grouping together with very virulent IBDV strains (vvIBDV, Genogroup 3), but these recent viruses formed a separate cluster, which was most closely related to Latvian IBDV strains from 2010-13. VP1 gene of these isolates was most closely related to D78 attenuated IBDV strain. The recently described reassortant IBDV strain (Bpop/03/PL) from Poland with similar genomic constellation (segment A from vvIBDV, segment B from attenuated strain) retained its pathogenicity (80 % mortality in SPF chickens). Infection with the North-West European reassortant IBDVs described in this study showed subclinical feature in the field (without complicating agents) and when tested under standardized pathogenicity test in SPF layer chickens (no mortality or clinical signs, but marked bursa atrophy was observed). Although these recent North-West European reassortant strains had all amino acid residues in their VP2 gene which are considered as markers of vvIBDV strains, they exhibited typical amino acid changes compared to vvIBDV reference strains that should contribute to the determination of pathogenicity. Diagnostic investigations indicated that co-infection with fowl adenovirus or chicken infectious anaemia virus exaggerated the outcome of the IBDV infection (10-20 % mortality). Widespread presence of this reassortant IBDV group in clinically healthy flocks draws attention to the importance of active surveillance.

Short beak and dwarfism syndrome of mule duck is caused by a distinct lineage of goose parvovirus.

From the early 1970s to the present, numerous cases of short beak and dwarfism syndrome (SBDS) have been reported in mule ducks from France. The animals showed strong growth retardation with smaller beak and tarsus. It was suggested that the syndrome was caused by goose parvovirus on the basis of serological investigation, but the causative agent has not been isolated and the disease has not so far been reproduced by experimental infection. The aim of the present study was to characterize the virus strains isolated from field cases of SBDS, and to reproduce the disease experimentally. Phylogenetic analysis proved that the parvovirus isolates obtained from SBDS of mule duck belonged to a distinct lineage of goose parvovirus-related group of waterfowl parvoviruses. The authors carried out experimental infections of 1-day-old, 2-week-old and 3-week-old mule ducks by the oral route with three different parvovirus strains: strain D17/99 of goose parvovirus from Derzsy's disease, strain FM of Muscovy duck parvovirus from the parvovirus disease of Muscovy ducks, and strain D176/02 isolated from SBDS of mule duck. The symptoms of SBDS of the mule duck could only be reproduced with the mule duck isolate (strain D176/02) following 1-day-old inoculation. Infection with a genetically different strain of goose parvovirus isolated from classical Derzsy's disease (D17/99) or with the Muscovy duck parvovirus strain (FM) did not cause any clinical symptoms or pathological lesions in mule ducks.

Comparison of the pathogenicity of QX-like, M41 and 793/B infectious bronchitis strains from different pathological conditions.

Five QX-like infectious bronchitis virus (IBV) strains, isolated from different field outbreaks and two reference IBV strains of known serotypes (M41 and 793/B), were used in the present study to investigate and compare their pathogenicity for 1-day-old specific pathogen free chickens. The ability of the strains to inhibit trachea epithelium ciliary activity, to induce immune response, to replicate and to cause histopathological lesions in designated organs was followed by repeated samplings during a period of 42 days post infection. Clear differences in pathogenicity and in organ distribution of the three serotypes were found. Strain 793/B had the least capacity to invade the investigated organs, while it produced a good humoral response as measured by enzyme-linked immunosorbent assay. The QX-like strains generally replicated to higher titres, although differences were found among the five strains in their pathogenicity and affinity for different organs. The Chinese isolate of QX-like virus caused the most severe lesions and induced the highest antibody titres. Severe kidney damage and dilatation of the oviduct were the prominent lesions that could be related to the QX-like IBV strains, although neither marked virus replication nor histopathological lesions were detected in the oviduct.

Recombinant subunit vaccine elicits protection against goose haemorrhagic nephritis and enteritis.

Outbreaks of haemorrhagic nephritis and enteritis of geese (HNEG) have been reported in goose flocks in Hungary, Germany and France since 1969. HNEG is characterized by high morbidity and mortality rates in geese 3 to 10 weeks of age. The causative agent of HNEG is the goose haemorrhagic polyomavirus (GHPV), which has a circular double-stranded DNA genome encoding the structural proteins VP1, VP2 and VP3. In vitro culture of GHPV has been problematic, so the baculovirus system was used to construct a recombinant virus expressing the VP1 gene of GHPV under control of the polyhedrin promoter in Sf9 insect cells. The expression and the identity of recombinant goose polyomavirus VP1 in the crude Sf9 cell extracts were confirmed by mass spectrometry. Experimental oil-emulsion vaccines containing two different doses of antigen were prepared using this crude extract. Goslings were vaccinated either once at 1 day old or twice by boosting 18 days after the primary vaccination, and were challenged with a virulent polyomavirus isolate at 5 weeks of age. A single injection of either vaccine dose induced 95% protection against challenge. Using the booster vaccination regimen, 100% protection was achieved with either vaccine dose.

Epidemiologic investigation of an outbreak of goose parvovirus infection in Sweden.

An outbreak of goose parvovirus (GPV) infection on a Swedish goose farm in the spring of 2004 increased the mortality rates from 2% in the early unaffected hatches to 90% and 99% respectively in the two hatches following virus introduction and 40% in goslings hatched later in the same breeding season. In this paper we describe the clinical observations, diagnostic procedures, and epidemiologic investigation carried out to elucidate the source of the infection. The diagnosis was confirmed by serology, virus isolation, and sequence analysis of a 493-bp-long fragment of the VP1 gene. Phylogenetically the causative virus was closely related to pathogenic GPV strains isolated in 2003 and 2004 from Poland and the United Kingdom, respectively. The Swedish isolate exhibited less homology with pathogenic strains from Hungary and Asia and with attenuated vaccine strains. The epidemiologic investigation showed that the virus was first introduced to a contract farm (farm A) and then was transferred with newly hatched goslings to the farm that had submitted the birds for necropsy (index farm). The exact time and source of the virus introduction to farm A could not be determined with absolute certainty. Possible sources of the infection included backyard goose eggs that had been delivered to farm A for subcontract incubation and hatching, wild geese that frequented the flock of breeding geese on pasture on farm A, and a clutch of Canada goose eggs (Branta canadensis) that had been produced by wild geese and was hatched in the same machine as the eggs produced by farm A.