Studies on a depressed egg production syndrome in Northern Ireland

The isolation and characterizations of a duck adenovirus 1 causing Egg Drop Syndrome in ducks, China

A fowl adenovirus variant designated as DAdV-JSXZ strain was isolated from the tissue specimen of fallopian tubes of a duck case, which was submitted from a 276-day-old Cherry valley breeding duck flock experienced egg-dropping syndromes in March 2022. Full-genome sequence of the DAdV-I JSXZ strain by next-generation sequencing revealed that the complete genome length of DAdV-JSXZ strain was 33,213 nucleotides and shared a high degree of nucleotide identity (97.0-99.4 %) with other DAdV-I reference strains. In pathogenicity studies, this isolated duck JSXZ strain reproduced similar egg-dropping symptoms in healthy breeding ducks, pathologic lesions of follicular hemorrhage, and the laid eggs in low fertilization and hatchability rates. Our research findings demonstrated that DAdV-I JSXZ strain was one of the causative agents of duck egg dropping syndrome in egg-laying ducks and could cause acute respiratory symptoms in ducklings.

Avian Viruses that Impact Table Egg Production

Eggs are a common source of protein and other nutrient components for people worldwide. Commercial egg-laying birds encounter several challenges during the long production cycle. An efficient egg production process requires a healthy bird with a competent reproductive system. Several viral pathogens that can impact the bird's health or induce reversible or irreversible lesions in the female reproductive organs adversely interfere with the egg industry. The negative effects exerted by viral diseases create a temporary or permanent decrease in egg production, in addition to the production of low-quality eggs. Several factors including, but not limited to, the age of the bird, and the infecting viral strain and part of reproductive system involved contribute to the form of reproductive disease encountered. Advanced methodologies have successfully elucidated some of the virus-host interactions relevant to the hen's reproductive performance, however, this branch needs further research. This review discusses the major avian viral infections that have been reported to adversely affect egg productivity and quality and aims to summarize the current understanding of the mechanisms that underlie the observed negative effects.

Isolation and partial genetic characterization of a new duck adenovirus in China

A novel duck adenovirus, isolated from Jinding Ducks(Anas platyrhynchos domestica), was proposed to be duck adenovirus 4 (DAdV-4), extending the genus Aviadenovirus. In this study, we sequenced the central genome part from Iva2 gene to fiber gene of the DAdV-4 that is conserved in all adenovirus genera. Phylogenetic analysis and protease cleavage site analysis verified the classification of DAdV-4 in the genus Aviadenovirus. Nucleotide identity analysis showed low sequence identity between central genome part genes of DAdV-4 with that of other aviadenoviruses. The phylogenetic tree based on the full amino acid sequence of hexon and DNA polymerase showed that the DAdV-4 appeared on a relatively independent branch. Our analysis suggested that DAdV-4 is a distinct type and represents a novel species. Although DAdV-4 has not caused serious disease outbreaks among ducks yet, the virus should be considered as a potential threat to the poultry industry.

Real-time fluorescence loop-mediated isothermal amplification assay for direct detection of egg drop syndrome virus

Background

Egg drop syndrome (EDS), caused by the adenovirus “egg drop syndrome virus” (EDSV) causes severe economic losses through reduced egg production in breeder and layer flocks. The diagnosis of EDSV has been done by molecular tools since its complete genome sequence was identified. In order to enhance the capabilities of the real-time fluorescence loop-mediated isothermal amplification (RealAmp) assay, we aimed to apply the method for direct detection of the EDSV without viral DNA extraction. In order to detect the presence of the EDSV DNA, three pairs of primers were designed, from the conserved region of fiber gene of the EDSV.

Results

For our assay, test and control samples were directly used in the reaction mixture in 10-fold serial dilution. The target DNA was amplified at 65 °C, which yield positive results in a relatively short period of 40–45 min. The method reported in this study is highly sensitive as compared to polymerase chain reaction (PCR) and showed no sign of cross-reactivity or false positive results. The RealAmp accomplished specific identification of EDSV among a variety of poultry disease viruses.

Conclusions

The direct RealAmp can be used to detect the presence of EDSV. As our result showed, the RealAmp method could be suitable for the direct detection of other DNA viruses.

Tropism and infectivity of duck-derived egg drop syndrome virus in chickens

Egg drop syndrome virus (EDSV) can markedly decrease egg production in laying hens. Duck is the natural host of EDSV. EDSV derived from ducks abrogate egg drop in laying hens. We have previously confirmed that duck-derived EDSVs have a variety of replication activities in chick embryo liver (CEL) cells. However, it is currently unclear whether duck-derived EDSV could display tropism and adaptation in laying hens. This study assessed whether duck-derived EDSV can adapt to laying hens, and estimated the inducing factors. Complete genome sequences of duck-derived EDSVs (D11-JW-012, D11-JW-017, and D11-JW-032 isolates) with various replication efficiency in CEL cells and C10-GY-001 isolate causing disease in laying hens were analyzed to find their differences. Phylogenetic analysis of complete genome sequence revealed that C10-GY-001, D11-JW-032, and strain 127 virus as vaccine were clustered into the same group, with D11-JW-012 and D11-JW-017 clustered in another group. Comparison between D11-JW-012 isolate that poorly replicated and D11-JW-017 isolate that replicated well in CEL cells in same cluster revealed six amino acid differences on IVa2, DNA polymerase, endopeptidase, and DNA-binding protein. These amino acids might be key candidates enhancing cellular tropism in chicken. When the pathogenicities of these isolates in laying hens were compared, D11-JW-032 showed severe signs similar to 127 virus, D11-JW-017 showed intermediate signs, while D11-JW-012 showed almost no sign. Eleven amino acids differed between D11-JW-032 and D11-JW-017, and 17 amino acids were different between D11-JW-032 and D11-JW-012. These results suggest that EDSVs derived from ducks have various pathogenicities in laying hens. Key amino acid candidates might have altered their affinity to tropism of laying hens, causing difference pathogenicities.

Egg Drop Syndrome-76 (EDS-76) in Japanese quails (Coturnix coturnix japonica): an experimental study revealing pathology, effect on egg production/quality and immune responses

Egg Drop Syndrome-76 (EDS-76) is a recognized disease of chickens and Japanese Quails, which is of high economic importance due to its drastic negative effects on egg production in laying birds. The aim of the present study was to better understand the EDS-76 viral disease process in Japanese quails (Coturnix coturnix japonica), since very limited studies have been conducted in this species of birds. For this purpose, an experimental study was conducted with infection of EDS-76 virus in laying Japanese quails to reveal pathology, effect on egg production/quality and immune responses of this virus in these birds. By 7, 9 and 13-15 Days Post Infection (DPI), drop as well as aberrant egg production and lower mean egg quality were observed compared to control birds. Significant histopathological changes were observed in genitalia and spleen. Haemagglutination Inhibition (HI) and Enzyme Linked Immunosorbent Assay (ELISA) titres rose rapidly by 2nd week when it became maximum; thereafter declined and maintained at low levels up to 10 week post infection. The mean total protein values in infected quail gradually increased to 4.10±0.05/100 mL without any change in mean albumen value at 12 DPI. In conclusion, the course of the EDS-76 is significant not only in chickens but also in quails even though it occurs occasionally in quails. Explorative pathological, blood biochemical and immunological studies are suggested during EDS-76 viral disease course in quails. This would aid in formulating effective disease prevention and control measures for this economically important disease of poultry.

Epidemiology of egg drop syndrome virus in ducks from South Korea

Egg drop syndrome virus (EDSV) is an important pathogen of poultry that decreases egg production in chickens and causes respiratory disease in goslings. In 2011, we obtained serum samples from 139 domestic Pekin ducks, 416 one-day-old Pekin ducklings, and 75 wild ducks (67 mallards and 8 pintails) to survey their exposure to EDSV. A total of 123 of 139 sera (88.5%) from Pekin ducks, 396 of the ducklings (95.2%), and 16 of 67 mallards (23.9%) were positive. Field cases of EDSV in wild and domestic ducks were investigated. Six cases from domestic Pekin ducks were identified by PCR detection and were used for virus isolation and molecular analysis. Phylogenetic analyses of the partial hexon and full fiber genes showed that the D11-JW-012 and D11-JW-017 strains among 6 isolates belonged to different clusters compared with other known strains including the 127 strain. We assessed cell growth efficiency by hemagglutination (HA) titers and cytopathic effects in duck embryo liver cells and chicken embryo liver (CEL) cells to investigate host adaptation. The D11-JW-017 strain propagated more in chicken embryo liver than the D11-JW-012 strain and the field isolate from chickens. Our results demonstrate the high prevalence of EDSV in wild and domestic ducks in South Korea and provide information on EDSV from ducks that showed variable adaptability in chickens.

Genomic characterization of Indian isolates of egg drop syndrome 1976 virus

Five Indian isolates of egg drop syndrome (EDS) 1976 virus and the reference strain 127 were compared by restriction enzyme analysis of viral DNA, and the hexon gene amplified by polymerase chain reaction. Using these techniques, no differences were seen among these viruses. However, partial sequencing of the hexon gene revealed major differences (4.6%) in one of the isolates sequenced, EDS Kerala. Phylogenetic analysis also placed this isolate in a different lineage compared with the other isolates. The need for constant monitoring of the genetic nature of the field isolates of EDS viruses is emphasized.

Host range, prevalence, and genetic diversity of adenoviruses in bats

Bats are the second largest group of mammals on earth and act as reservoirs of many emerging viruses. In this study, a novel bat adenovirus (AdV) (BtAdV-TJM) was isolated from bat fecal samples by using a bat primary kidney cell line. Infection studies indicated that most animal and human cell lines are susceptible to BtAdV-TJM, suggesting a possible wide host range. Genome analysis revealed 30 putative genes encoding proteins homologous to their counterparts in most known AdVs. Phylogenetic analysis placed BtAdV-TJM within the genus Mastadenovirus, most closely related to tree shrew and canine AdVs. PCR analysis of 350 bat fecal samples, collected from 19 species in five Chinese provinces during 2007 and 2008, indicated that 28 (or 8%) samples were positive for AdVs. The samples were from five bat species, Hipposideros armiger, Myotis horsfieldii, M. ricketti, Myotis spp., and Scotophilus kuhlii. The prevalence ranged from 6.25% (H. armiger in 2007) to 40% (M. ricketti in 2007). Comparison studies based on available partial sequences of the pol gene demonstrated a great genetic diversity among bat AdVs infecting different bat species as well as those infecting the same bat species. This is the first report of a genetically diverse group of DNA viruses in bats. Our results support the notion, derived from previous studies based on RNA viruses (especially coronaviruses and astroviruses), that bats seem to have the unusual ability to harbor a large number of genetically diverse viruses within a geographic location and/or within a taxonomic group.

Studies on the persistence and excretion of egg drop syndrome 1976 virus in chickens

EDS virus strain 127 did not induce clinical signs or gross lesions in susceptible chicks of various age groups and in adult cocks. Virus persistence in various internal organs and the rate of excretion of virus by experimentally-infected chicken declined rapidly with increasing age. Virus 127 was detectable in organs of young chicks up to 5 weeks post-infection and in their faeces up to 2 weeks post-infection. In adult birds virus 127 persisted in tissues for about 3 weeks and was excreted with faeces for only 1 week post-infection. Vaccination of adult cocks with an inactivated vaccine resulted in intermittent shedding of virus only within the first 4 days post-challenge; thus, in comparison to non-vaccinated chickens, vaccination reduced virus excretion in faeces to a major extent.

Isolation and serological studies with infectious bursal disease viruses from fowl, turkeys and ducks: demonstration of a second serotype

The isolation of a number of strains of infectious bursal disease (IBD) virus from fowl, turkeys and ducks is described. These isolates could be grouped into two serotypes using the neutralisation test. It is proposed that the cell culture adapted vaccine strain from fowl should be the prototype virus for serotype 1 and that the TY89 isolate from a turkey should be the prototype for serotype 2. The isolates in serotype 2 consisted of an antigenically homogeneous group of viruses from turkeys and fowl. However, within serotype 1, which represented isolates from fowl and ducks, some isolates showed only a 30% cross reaction with the vaccine strain. If cross protection mirrors cross neutralisation, then infection with viruses belonging to serotype 2 or with antigenically distant strains from serotype 1 provides one explanation for the apparent failure of the vaccine on certain sites. However, if cross protection does not mirror cross neutralisation, then a virus from serotype 2 could be used as a heterotypic vaccine for young birds with high levels of maternally derived antibody to serotype 1.

Serological survey for the prevalence of antibodies to egg drop syndrome 1976 virus in domesticated and wild birds in Israel

A serological survey of chicken, turkey, goose and duck flocks for the presence of antibodies to egg drop syndrome virus 1976 (EDS 76) has been carried out in Israel. In most of the chicken flocks sampled egg production was not normal, but no antibodies against this virus were detected. Likewise, turkey breeding flocks were similarly negative. All Pekin duck flocks tested showed some serological activity. Muscovy ducks that were reared in direct or indirect contact with Pekin ducks had haemagglutination-inhibition antibodies to EDS 76 virus. Seven cattle egrets trapped on a duck farm were serologically positive. No antibodies were detected in a collection of water fowl raised in a zoological garden.

Phylogenetic analysis of adenovirus sequences

Members of the family Adenoviridae have been isolated from a large variety of hosts, including representatives from every major vertebrate class from fish to mammals. The high prevalence, together with the fairly conserved organization of the central part of their genomes, make the adenoviruses one of (if not the) best models for studying viral evolution on a larger time scale. Phylogenetic calculation can infer the evolutionary distance among adenovirus strains on serotype, species, and genus levels, thus helping the establishment of a correct taxonomy on the one hand, and speeding up the process of typing new isolates on the other. Initially, four major lineages corresponding to four genera were recognized. Later, the demarcation criteria of lower taxon levels, such as species or types, could also be defined with phylogenetic calculations. A limited number of possible host switches have been hypothesized and convincingly supported. Application of the web-based BLAST and MultAlin programs and the freely available PHYLIP package, along with the TreeView program, enables everyone to make correct calculations. In addition to step-by-step instruction on how to perform phylogenetic analysis, critical points where typical mistakes or misinterpretation of the results might occur will be identified and hints for their avoidance will be provided.

Restriction enzyme analysis of Indian isolates of egg drop syndrome 1976 virus recovered from chicken, duck and quail

Egg drop syndrome 1976 (EDS-76) is caused by a haemagglutinating adenovirus belonging to group III of the genus Aviadenovirus in the family Adenoviridae. All isolates are serologically identical, but have been divided into three groups based on restriction endonuclease (RE) analysis. In this study the viral DNA of various Indian EDS-76 viral isolates (CEDS-A, CEDS-B, EDS-M, EDS-ML, EDS-1/AD/86, EDS-KC and QEDS) obtained from different avian species and different geographical regions were digested with restriction endonucleases viz., EcoRI, BamHI, HindIII and PstI. The results showed that one Indian isolate obtained from duck (DEDS-KC) was different from all other chicken and quail counterparts. All other isolates were identical to the reference viral strain BC-14, which belong to group I of EDS-76 viruses. The duck isolate EDS-KC could not be placed in any of the three groups reported earlier.

Characterization of fowl adenovirus serotype-4 associated with hydropericardium syndrome in chicken

The polypeptides of three fowl adenovirus-4 (FAV-4) field isolates of hydropericardium syndrome from various geographical areas of the country and the standard FAV-1 (CELO virus) were subjected to sodium dodecyl sulfate polyacrylamide gel electrophoresis and analysed by protein immunoblotting with polyclonal antibodies to FAV-4 and FAV-1. Protein profile analysis of FAV-4 isolates revealed similarity of all the eight polypeptides with molecular weight ranging from 20 to 107 kDa but differed from CELO, particularly in their 24.2 kDa protein. Subsequent immunoblotting showed relatedness of at least five protein fractions of FAV-4 to CELO virus.

The complete nucleotide sequence of the egg drop syndrome virus: an intermediate between mastadenoviruses and aviadenoviruses

The complete nucleotide sequence of an avian adenovirus, the egg drop syndrome (EDS) virus, was determined. The total genome length is 33,213 nucleotides, resulting in a molecular weight of 21.9 x 10(6). The GC content is only 42.5%. Between map units 3.5 and 76.9, the distribution of open reading frames with homology to known genes is similar to that reported for other mammalian and avian adenoviruses. However, no homologies to adenovirus genes such as E1A, pIX, pV, and E3 could be found. Outside this region, several open reading frames were identified without any obvious homology to known adenovirus proteins. In the region organized similarly as other adenoviral genomes, most homologies were found to an ovine adenovirus (OAV strain 287). The highest level of amino acid identity was found for the hexon proteins of EDS and OAV. The virus-associated RNA (VA RNA) was identified thanks to the homology with the VA RNA of fowl adenovirus serotype 1 (FAV1). Similarities with FAV1 were also found in the fiber protein. Our results demonstrate that the avian EDS virus represents an intermediate between mammalian and avian adenoviruses. The nucleotide sequence and genomic organization of the EDS virus reflect the heterogeneity of the aviadenovirus genus and the Adenoviridae family.

Close phylogenetic relationship between egg drop syndrome virus, bovine adenovirus serotype 7, and ovine adenovirus strain 287

A cloned egg drop syndrome (EDS) virus genomic DNA fragment containing the protease gene has been identified and the complete nucleotide sequence of the protease and partial nucleotide sequence of the hexon genes has been determined. Phylogenetic analysis of the protease gene has revealed EDS virus to be genetically more closely related to bovine adenovirus type 7 (BAV-7) and ovine adenovirus isolate 287 (OAV287) than either of these two viruses are to other members of the genus Mastadenovirus or EDS virus is to an other member of the Aviadenovirus genus. The three viruses share further similarities in that they have a high percentage AT content in their genome and are characterized by having more compact genomes than other adenoviruses. The protease gene from all three viruses contained the active site residues (H55-D72-C122 triad) and C104 (providing a disulfide bond to cofactor pVIc). However, P137, found in all other members of the Mastadenovirus genus, and thought to be involved in trafficking, was missing from the protease of the EDS virus, BAV-7, and OAV287. These results suggest that EDS virus should be classified along with BAV-7 and OAV287 in a separate taxon.

Egg Drop syndrome '76 in Bolivia

Four outbreaks of Egg Drop Syndrome '76 (EDS '76) were diagnosed between April 1993 and July 1993 in the Santa Cruz Department of Bolivia, around the department capital Santa Cruz. Three outbreaks involved commercial laying birds and the fourth a broiler breeder unit. Clinical signs were typical of EDS '76 with decreases in egg production of up to 55% being recorded as well as the production of thin shelled and shell-less eggs. A total of 183 serum samples from the 4 farms were tested for the presence of antibodies to the EDS '76 virus using a haemagglutination inhibition test, with titres of 16 or above being considered as a positive result. Of 63 samples from groups of birds showing signs of EDS '76, 58 (92.1%) had positive titres, and 88 out of 90 samples (97.8%) from unaffected groups of birds had negative titres. Out of 30 samples from birds not yet in lay from the affected farms 28 (93.3%) had tires below 16. EDS '76 had not been reported in Bolivia prior to these outbreaks and vaccination was not practised. The most probable source of virus was from day old chicks imported from South American countries which had recorded outbreaks of EDS '76 before April 1993. The source of the virus, its spread and the control measures implemented in the Santa Cruz area are discussed.

EDS 76 HI antibodies in a flock of free-range layers

An investigation of poor laying performance in a flock of free-range hens revealed high levels of serum antibodies to EDS 76 in the flock initially examined and in another, older flock on the same farm. These flocks had contact with ducks on a farm dam and were supplied with untreated drinking water from the dam. Serological evidence indicated that another flock supplying the same egg packing station had been infected with EDS 76 virus. Little serological evidence of EDS infection was detected from five other flocks supplying the packing station, parent breeders or the ducks resident on the dam. Therefore, the source of the EDS 76 virus remains conjectural.

Biological characterisation of an Indian isolate of egg drop syndrome-76 virus

An isolate of egg drop syndrome-76 virus replicated best in primary chicken embryo liver cells and less well in duck embryo liver cells, duck embryo fibroblast cells and chicken embryo kidney cells. The cytopathic effect in chicken embryo liver cells was marked by the presence of round and refractile cells and detachment of cells from the glass surface. The intranuclear eosinophilic inclusion bodies were observed by 24 to 48 hours after infection. No virus multiplication was observed in primary quail embryo fibroblast cells, chicken embryo fibroblast cells or mammalian cells like Vero, BHK-21 and MDBK. Duck embryos supported the maximum growth of the virus, with allantoic fluid having the highest haemagglutinin titre, followed in order by chorioallantoic membrane, skin and internal organs. Chicken and quail embryos did not support the growth of the virus.

Purification and hemagglutinating properties of egg drop syndrome 1976 virus

We purified three populations of virus particles, F7, F9 and F17, with buoyant densities of 1.34, 1.33 and 1.29 g/ml, respectively, in CsCl equilibrium density gradients from cultures of chick embryo liver cells infected with the H-162 strain of the virus of egg drop syndrome 1976. F9 particles were infectious complete virions and most F17 particles were empty particles. F7 particles were less infectious, and had little capacity of hemagglutination (HA). HA titers were the same at 4 degrees and 37 degrees C and maximal between pH 6.4 and 8.4 and ionic strength from 0.14 to 0.54 M of NaCl. HA titer was inversely proportional to erythrocyte concentration. Potassium periodate destroyed markedly the infectivity of the virus and partially its HA activity at 37 degrees C. HA activity was stable at 56 degrees C or lower temperatures and destroyed at 80 degrees C. Trypsin, alpha-chymotrypsin, papain, ficin and neuraminidase had no effect on HA activity. Alpha-chymotrypsin destroyed the receptor for the virus on chicken erythrocytes, whereas trypsin and neuraminidase did not affect the receptor.

A survey of disease in five commercial flocks of meat breeder chickens

Causes of sickness and death in approximately 30,000 chickens in 5 meat breeder flocks were investigated between May 1979 and April 1980. Approximately 23% of disease was due to neoplasms; 81% of these were Marek's disease despite vaccination against this infection. Other frequent diagnoses included cellulitis (15%), respiratory disease (14%), lesions of the reproductive tract (11%) and tenosynovitis/arthritis (9%). Antibodies to Mycoplasma gallisepticium, avian adenovirus, infectious bursal disease virus and reticuloendotheliosis virus were present in all flocks. Antibody to Newcastle disease virus (NDV) was found in 2 flocks but titres were not considered protective against a virulent NDV challenge. Antibody to egg drop syndrome 1976 virus was found in 2 flocks comprised of the same breed of bird.

Egg drop syndrome 1976 (EDS-76) virus infection in inadequately vaccinated chickens

Experiments were carried out to study the epizootiology of the egg drop syndrome 1976 virus infection in chickens that were not adequately protected by vaccination. Virus excretion was demonstrated when chickens vaccinated at the recommended level were challenged within 10 days of vaccination and when chickens were challenged 6 weeks after administration of low doses of vaccine. In the latter experiment, those chickens which shed virus had all shown a poor haemagglutination inhibition antibody response to vaccination but had high serum neutralisation antibody titres when challenged.

The fibers of fowl adenoviruses

Purified virions from 14 strains of fowl adenoviruses (FAV) representing 11 serotypes were examined by electron microscopy. Pentons of all strains turned out to have two projections at their penton bases. It is shown that the double fibers also protrude from the intact virion. The length of both fibers was measured on free pentons and is given for each serotype. Double fibers seem to be a common feature of FAV. The serologically unrelated Egg Drop Syndrome (EDS) avian adenovirus strain 127 was confirmed to have single fibers only.

Serological examination and egg production of progeny of fowl experimentally infected with egg drop syndrome 1976 virus

Following EDS'76 virus (BC14 virus) infection of breeder chickens by the conjunctival route, vertical transmission occurred in the first week after infection. In the progeny which had been infected with EDS'76 virus by the vertical route, increasing haemagglutination inhibiting (HI) titres to BC14 virus and increasing numbers of birds with HI titres were observed from 3 weeks to 15 weeks of age. Sixty-one per cent of the hens and 77 per cent of the cocks had 2 log HI BC14 virus titres exceeding 4 at an age of 15 weeks. Some birds which han been serologically negative throughout the rearing period, seroconverted between 25 and 28 weeks of age. This phenomenon occurred in hens as well as in cocks. Simulation of stress twice during the laying period by injection of corticosteroid hormone did not increase the number of birds serologically positive to EDS'76 virus. EDS'76 was observed in the group of hens that was vertically infected, since egg production was significantly depressed between 28 and 34 weeks of age. Probably this was mainly the results of a production drop in the hens showing serconversion at 27 or 28 weeks of age. In this group of fowl vertically infected with EDs'76 virus, serologically positive birds appeared to be protected for the greater part to BC14 virus challenge at 50 weeks of age, while negative birds seemed to be fully susceptible. Chicks hatched from eggs collected in the third and fourth week after infection of the dams had maternal antibodies. Fertility and hatchability of apparently normally shelled eggs seemed not to be affected after BC14 virus infection of the dams. Intensive contact with contaminated faeces is probably an indispensable condition for lateral transmission of the virus.

Some biological and physico-chemical properties of egg drop syndrome (EDS) avian adenovirus strain B8/78

The EDS adenovirus produced either in the allantoic cavity of embryonated duck eggs (A0 virus) or in chicken embryo liver cell cultures (TC0 virus) were comparatively studied by gradient ultracentrifugation in CsCl. The A0 viral particles banded at densities of 1.36 and 1.31 g/ml, whereas, the TC0 viral particle were found at densities of 1.33 and 1.31 g/ml, respectively. The heavy populations contained infectious and hemagglutinating particles if they were not pelleted and sonicated before gradient ultracentrifugation. Pelleting or sonicating the viral particles resulted in loss of hemagglutinating activity of the heavy populations. The light particles were hemagglutinating but not infectious regardless of the previous treatment. The pH- and heat-sensitivity of the B8/78 virus strain was similar to those described for CEL0 (FAV-1) adenovirus (5). The B8/78 virus strain replicated well in tissue cultures of chicken and goose origin causing the formation of intranuclear inclusion bodies in the infected cells.

Isolation of haemagglutinating adeno-like virus related to virus 127 from an Australian poultry flock with an egg drop syndrome

An egg drop syndrome within Australian broiler poultry is described. The syndrome was characterised by delayed onset of laying, a lower peak in egg production and a drop in egg production shortly after reaching peak production. Antibody to virus 127 was detected in 102 of 106 fowl serums tested. Two haemagglutinating viruses were isolated from one affected flock and one was subjected to further study. It was adenovirus-like on electron-microscopic examination and haemagglutination was not inhibited by a specific antiserum to Newcastle disease virus. An antiserum was raised in White Leghorn fowl against the isolate and this antiserum was found to cross-react with virus 127, a prototype virus of Egg Drop Syndrome 76.