Necrotic, haemorrhagic, hepatomegalic hepatitis associated with vasculitis and amyloidosis in commercial laying hens

FAdV-4 Promotes Expression of Multiple Cytokines and Inhibits the Proliferation of aHEV in LMH Cells

Single or mixed infections of multiple pathogens such as avian hepatitis E virus (aHEV) and avian leukosis virus subgroup J (ALV-J) have been detected in numerous laying hens with severe liver injury in China. Thus, aHEV and immunosuppressive viruses are speculated to cause co-infections. In this study, co-infection with aHEV and fowl adenovirus (FAdV) was confirmed by nested RT-PCR and recombinase-aided amplification combined with gene sequencing in two flocks with severe liver injury. Subsequently, the two reference strains, aHEV and FAdV-4, were inoculated into LMH cells to identify their co-infection potential. Confocal microscopy revealed aHEV and FAdV-4 co-infected LMH cells. In addition, the replication dynamics of aHEV and FAdV-4 along with the expression levels of immuno-cytokines were measured. The results indicated colocalization of aHEV and FAdV-4 and inhibition of viral replication in LMH cells. The transcription levels of MDA5, Mx, OASL, and IFN-α were significantly upregulated in LMH cells, whereas those of immune-related factors induced by FAdV-4 were downregulated upon FAdV-4 and aHEV co-infection. These results confirmed the co-infection of aHEV and FAdV-4 in vitro and prompted the antagonistic pathogenic effects of FAdV-4 and aHEV, thereby providing novel insights into the counterbalancing effects of these viruses.

Virome Profiling of Chickens with Hepatomegaly Rupture Syndrome Reveals Coinfection of Multiple Viruses

Liver diseases seriously challenge the health of chickens raised on scaled farms and cause tremendous economic losses to farm owners. The causative agents for liver diseases are still elusive, even though various pathogens, such as the hepatitis E virus, have been reported. In the winter of 2021, a liver disease was observed on a chicken farm in Dalian, China, which increased chicken mortality by up to 18%. We conducted panvirome profiling of the livers, spleens, kidneys, and recta of 20 diseased chickens. The viromic results revealed coinfection of multiple viruses, including pathogenic ones, in these organs. The viruses were highly identical to those detected in other provinces, and the vaccine and field strains of avian encephalomyelitis virus (AEV) and chicken infectious anemia virus (CIAV) cocirculated on the farm. In particular, the liver showed higher abundance of AEV and multiple fowl adenoviruses than other organs. Furthermore, the liver also contracted avian leukemia virus and CIAV. Experimental animals with infected liver samples developed minor to medium lesions of the liver and showed a virus abundance profile for AEV across internal organs similar to that in the original samples. These results suggest that coinfection with multiple pathogenic viruses influences the occurrence and development of infectious liver disease. The results also highlight that strong farm management standards with strict biosafety measures are needed to minimize the risk of pathogenic virus introduction to the farm.

Hemorrhagic Hepatopathy in Broiler Breeder Pullets: Gross and Microscopic Pathology and Factors Associated with Incidence

Hemorrhagic hepatopathy is a syndrome reported in layer pullets resulting in mortality and lesions including hepatic, splenic, and intestinal necrosis; hepatic and splenic enlargement; hemorrhages; amyloidosis of the muscle, spleen, and liver; accumulation of noncoagulated hemorrhagic fluid in the coelom; and frequently, granulomatous myositis at bacterin injection sites. The syndrome is characterized in the literature in table egg layer pullets and is thought to be associated with the administration of bacterin vaccines, namely, frequently Salmonella enterica subsp. enterica bacterins. Hemorrhagic hepatopathy is recognized by industry veterinarians as also occurring infrequently in broiler breeder pullets in the United States. As the condition is likely due to an inflammatory process in response to bacterial lipopolysaccharide inoculation, it is important to characterize both the pathologic changes and predisposing factors for the condition in broiler breeds, which are immunologically different from table egg layer breeds. In this study, we characterize the gross and microscopic lesions observed in a series of diagnostic laboratory cases of hemorrhagic hepatopathy in broiler breeder pullets and suggest a possible pathophysiology for the condition. Additionally, we report results from a case survey of the United States broiler industry that suggest that the condition is due to a reaction to bacterin vaccination and that certain bacterin products may predispose pullet flocks to develop the condition. Although further research is indicated, these findings establish hemorrhagic hepatopathy as a pathologic condition of broiler breeder pullets and may aid in the diagnosis and prevention of the syndrome.

Research Note: A putative novel subtype of the avian hepatitis E virus of genotype 3, Jiangxi province, China

In recent years, the avian hepatitis E virus (HEV) has been widely spread in China, causing huge economic losses. Several studies have carried out detailed epidemiologic investigations of the avian HEV, but no data were from Jiangxi province. Since early April 2020, diseases similar to hepatic rupture hemorrhage syndrome caused by the avian HEV occurred in a Roman Brown layer farm in Jiangxi province, indicating this virus may also be epidemic there. To make this assumption clear, 20 liver samples were collected from the sick flock and then analyzed by detailed viral detection, which confirmed that the avian HEV should be responsible for the aforementioned disease (6 of 20). Then, the capsid gene of the virus was sequenced to show the molecular characteristics of the strain circulating in the aforementioned flock. Sequence comparison showed that it shared 80.7 to 94.7% identities with 12 published strains, while phylogenetic analysis confirmed that it belongs to a new subtype of genotype 3. Moreover, basing on a 242 bp fragment, the novel also shared high similarities to reference strains identified as genotypes before, revealing the genotype 3 maybe very popular in China and even can be divided into several subgroups. In conclusion, a novel avian HEV strain was identified in this study, which belongs to a new subtype of genotype 3. The analysis makes up for the molecular epidemiologic data of avian HEV and provides a basis for further understanding the spread of avian HEV in China.

Avian Hepatitis E Virus: With the Trend of Genotypes and Host Expansion

Avian hepatitis E virus (HEV) is a single-stranded, positive-sense RNA virus with a complete genome of approximately 6.6 kb in size. To date, four major genotypes of avian HEV have been identified and classified into the Orthohepevirus B genus of the family Hepeviridae. The avian HEV associated with hepatitis-splenomegaly syndrome, big liver and spleen disease or hepatic rupture hemorrhage syndrome in chickens is genetically and antigenically related to mammalian HEV. With the increased genotypes of avian HEV identified, a broader host tropism is also notable in the epidemiological studies. Due to the lack of an efficient cell culture system, the mechanisms of avian HEV replication and pathogenesis are still poorly understood. The recent identification and characterization of animal strains of avian HEV has demonstrated the virus' ability of cross-species infection. Although it has not yet been detected in humans, the potential threat of a zoonotic HEV capable of transmission to humans needs to be taken into consideration. This review article focuses on the current knowledge regarding avian HEV in virology, epidemiology, pathogenesis, clinical presentation, transmission, diagnosis and prevention.

HIGHLIGHTS

- The mechanisms of avian HEV replication and pathogenesis are still poorly understood due to the lack of an efficient cell culture system.- A broader host tropism is also notable in the epidemiological studies with the increased genotypes of avian HEV identified.- The recent identification and characterization of animal strains of avian HEV has demonstrated the virus' ability of cross-species infection.- The potential threat of a zoonotic HEV capable of transmission to humans needs to be taken into consideration.

Hepatic rupture hemorrhage syndrome in chickens caused by a novel genotype avian hepatitis E virus

Since 2016, severe outbreaks of hepatic rupture hemorrhage syndrome (HRHS) have emerged in chickens in several Chinese provinces and caused huge economic losses to the poultry industry, but the etiological characteristics and pathogenic potential of it has remained unclear. This study sequenced the partial helicase and capsid gene of the potentially novel avian hepatitis E virus (HEV) isolated from chickens with HRHS and tested the pathogenicity of it on SPF chicks, while the appearance of clinical signs, histopathological changes, viral distribution, viremia and viral shedding were monitored for 14 days post-infection (dpi). Analysis revealed that the HRHS related avian HEV belongs to a novel genotype, and infected chicks developed the typical symptoms of HRHS. Thus, this study successfully developed an experimental infection model for studying the pathogenicity and role of the novel avian HEV in HRHS. Meanwhile, the novel avian HEV mainly existed in the liver and spleen, inducing a rapid viremia and chronic viral shedding in infected chicks, and could cause 40% mortality before 14 dpi. In conclusion, this study found the novel genotype avian HEV and confirmed its role in HRHS.

Hepatitis Virus Infections in Poultry

Viral hepatitis in poultry is a complex disease syndrome caused by several viruses belonging to different families including avian hepatitis E virus (HEV), duck hepatitis B virus (DHBV), duck hepatitis A virus (DHAV-1, -2, -3), duck hepatitis virus Types 2 and 3, fowl adenoviruses (FAdV), and turkey hepatitis virus (THV). While these hepatitis viruses share the same target organ, the liver, they each possess unique clinical and biological features. In this article, we aim to review the common and unique features of major poultry hepatitis viruses in an effort to identify the knowledge gaps and aid the prevention and control of poultry viral hepatitis. Avian HEV is an Orthohepevirus B in the family Hepeviridae that naturally infects chickens and consists of three distinct genotypes worldwide. Avian HEV is associated with hepatitis-splenomegaly syndrome or big liver and spleen disease in chickens, although the majority of the infected birds are subclinical. Avihepadnaviruses in the family of Hepadnaviridae have been isolated from ducks, snow geese, white storks, grey herons, cranes, and parrots. DHBV evolved with the host as a noncytopathic form without clinical signs and rarely progressed to chronicity. The outcome for DHBV infection varies by the host's ability to elicit an immune response and is dose and age dependent in ducks, thus mimicking the pathogenesis of human hepatitis B virus (HBV) infections and providing an excellent animal model for human HBV. DHAV is a picornavirus that causes a highly contagious virus infection in ducks with up to 100% flock mortality in ducklings under 6 wk of age, while older birds remain unaffected. The high morbidity and mortality has an economic impact on intensive duck production farming. Duck hepatitis virus Types 2 and 3 are astroviruses in the family of Astroviridae with similarity phylogenetically to turkey astroviruses, implicating the potential for cross-species infections between strains. Duck astrovirus (DAstV) causes acute, fatal infections in ducklings with a rapid decline within 1-2 hr and clinical and pathologic signs virtually indistinguishable from DHAV. DAstV-1 has only been recognized in the United Kingdom and recently in China, while DAstV-2 has been reported in ducks in the United States. FAdV, the causative agent of inclusion body hepatitis, is a Group I avian adenovirus in the genus Aviadenovirus. The affected birds have a swollen, friable, and discolored liver, sometimes with necrotic or hemorrhagic foci. Histologic lesions include multifocal necrosis of hepatocytes and acute hepatitis with intranuclear inclusion bodies in the nuclei of the hepatocytes. THV is a picornavirus that is likely the causative agent of turkey viral hepatitis. Currently there are more questions than answers about THV, and the pathogenesis and clinical impacts remain largely unknown. Future research in viral hepatic diseases of poultry is warranted to develop specific diagnostic assays, identify suitable cell culture systems for virus propagation, and develop effective vaccines.

Characterization of Seven Outbreaks of Hemorrhagic Hepatopathy Syndrome in Commercial Pullets Following the Administration of a Salmonella Enteritidis Bacterin in California

Between April 2013 and April 2015, seven flocks belonging to three different major commercial egg producers inCalifornia experienced a mild increase in mortality 2 to 3 wk after administration of Salmonella Enteritidis bacterins. Strains of chickens involved were H&N (flock A1, A2, B2, C1, C2, and C3) and Lohmann white (flock B1). Vaccination was administered individually through injection either in the breast muscles or subcutis in the legs between 11 and 18 wk of age in all flocks. Clinical signs ranged from inapparent to lameness, reluctance to walk, greenish diarrhea, and retching-like symptoms. The mortality ranged from 0.16% to 1.38% per week, with the highest peaks occurring usually 2 to 3 wk postvaccination, and then declined rapidly. Postmortem examinations revealed enlarged livers with disseminated hemorrhages and pale foci of necrosis. Also, severe extensive hemorrhages in the intestine, heart, and proventriculus were observed in a few birds. Various degrees of productive, exudative giant cell granulomatous myositis were observed invading deeply the muscles and subcutis at the site of vaccination. The myositis was always associated with optically empty vacuoles positive for neutral lipids by Oil Red O stain. Droplets of Oil Red O material were also noticed in the affected livers and intestines. Congo red stain highlighted the presence of amyloid in moderate to severe amounts in the breast muscles and moderate amounts in livers, spleens, and intestines. Salmonella antigens were detected in the injection sites and livers by immunohistochemical staining. No viruses or toxic substances were recovered from the liver, spleen, intestine, and pectoral muscles, and the few bacteria isolated were interpreted as secondary postmortem invaders. In addition, livers and bile tested for hepatitis E virus were negative by reverse-transcriptase polymerase chain reaction.

Necrotizing and haemorrhagic hepatitis and enteritis in commercial layer pullets

This case report describes an episode of recurring severe necrotizing and haemorrhagic hepatitis and enteritis experienced in a flock of commercial layer pullets at 12 weeks of age and again at 18 weeks of age in Indiana. Pullets had been vaccinated at 10 weeks old using a trivalent Salmonella Enteritidis (SE)/Newcastle disease/infectious bronchitis oil-emulsion-inactivated vaccine. The pullets were found dead at 12 weeks with firm but friable, enlarged, haemorrhagic livers, enlarged spleens, and necrohaemorrhagic intestines. Histopathologic findings were consistent with a necrotizing and haemorrhagic enteritis and hepatitis. Livers had multiple intra-sinusoidal thrombi, intestines contained Gram-positive bacterial colonies, and spleens had marked lymphoid depletion. The pullets seemed to improve after antibiotic treatment. Pullets were vaccinated with an inactivated SE vaccine at 14 weeks of age. A second spike of mortality occurred at 18 weeks of age. Although clostridial enteritis and hepatitis were highly suspected in the two cases based on macroscopic and microscopic findings, no significant bacterial or viral agents were isolated from the livers and intestines. In summary, lesions in the liver and intestines are speculated to be due to repetitive vaccination, leading to an anamnestic response by the immune system, and resulting in an immune-mediated response. However, much of the pathogenesis is still unclear, and other causes such as unidentified infectious aetiology, transmissible amyloidosis, and hypersensitivity may need further investigation.

Hepeviridae: an expanding family of vertebrate viruses

The hepatitis E virus (HEV) was first identified in 1990, although hepatitis E-like diseases in humans have been recorded for a long time dating back to the 18th century. The HEV genotypes 1-4 have been subsequently detected in human hepatitis E cases with different geographical distribution and different modes of transmission. Genotypes 3 and 4 have been identified in parallel in pigs, wild boars and other animal species and their zoonotic potential has been confirmed. Until 2010, these genotypes along with avian HEV strains infecting chicken were the only known representatives of the family Hepeviridae. Thereafter, additional HEV-related viruses have been detected in wild boars, distinct HEV-like viruses were identified in rats, rabbit, ferret, mink, fox, bats and moose, and a distantly related agent was described from closely related salmonid fish. This review summarizes the characteristics of the so far known HEV-like viruses, their phylogenetic relationship, host association and proposed involvement in diseases. Based on the reviewed knowledge, a suggestion for a new taxonomic grouping scheme of the viruses within the family Hepeviridae is presented.

Impact of Escherichia coli vaccine on parent stock mortality, first week mortality of broilers and population diversity of E. coli in vaccinated flocks

In the present investigation 20,000 broiler parents were vaccinated during rearing with Nobilis Escherichia coli vaccine and were placed in two out of four identical houses, with the remaining two houses on the same farm accommodating 20,000 unvaccinated control birds. During the production period a total of 335 dead birds (including 171 vaccinated and 164 control birds) randomly selected from the four houses were subjected to post-mortem examination. Although the overall mortality between the vaccinated and control flocks did not differ, mortality due to E. coli infections made up only 8.2% in vaccinated birds compared with 24.6% in unvaccinated birds. All E. coli isolates recovered from internal organs were assigned to the same phylogenetic group (B2), but a major genetic diversity was outlined by multilocus sequence typing. Only a single isolate was demonstrated to harbour a gene encoding the P-fimbriae variant F11, a key component of the Nobilis vaccine. Significant differences in average first week mortality, calculated average weight at 38 days and food conversion rate among broiler flocks originating from vaccinated and control birds, respectively, were not found. Further investigations are needed to explain the protection observed and the impact on the genetic diversity of E. coli.

Avian hepatitis E virus in an outbreak of hepatitis–splenomegaly syndrome and fatty liver haemorrhage syndrome in two flaxseed-fed layer flocks in Ontario

Two commercial layer chicken flocks that were fed a flax-based diet beginning at 28 weeks of age for the production of omega-3 fatty-acid-enriched eggs experienced increased mortality when the birds reached 37 weeks. The average weekly mortality was 0.34% over a 20-week period, with peak mortality of 0.9% for 1 week. Reduced feed consumption, reduced body weight gain and poor peak production were noticed prior to the onset of increased mortality. A total of 245 birds were necropsied and 78% of these had lesions in the liver and spleen, with 44% of those necropsied having changes consistent with hepatitis-splenomegaly syndrome, with lesions ranging from acute periportal lymphoplasmacytic hepatitis to chronic severe cholangiohepatitis with haemorrhage, vasculitis and amyloidosis. A total of 11% of the birds had lesions typical of fatty liver haemorrhagic syndrome, and 22% had lesions found in both hepatitis-splenomegaly syndrome and fatty liver haemorrhagic syndrome. No significant bacteria or viruses were recovered from samples of the liver/bile or spleen but 11 of 21 bile samples contained avian hepatitis E virus RNA detectable with a reverse transcriptase-polymerase chain reaction assay. Comparative sequence analysis found identities of 82 to 92% and 78 to 80% between the helicase and capsid protein genes, respectively, of the virus detected in this outbreak and those of other avian hepatitis E virus isolates, suggesting extensive genetic heterogeneity in avian hepatitis E viruses in Ontario flocks.

Production and growth related disorders and other metabolic diseases of poultry – A review

In humans, metabolic complaints may be associated with a failure in one of the body hormone or enzyme systems, a storage disease related to lack of metabolism of secretory products because of the lack of production of a specific enzyme, or the breakdown or reduced activity of some metabolic function. Some of these disorders also occur in poultry, as do other important conditions such as those associated with increased metabolism, rapid growth or high egg production that result in the failure of a body system because of the increased work-load on an organ or system. These make up the largest group of poultry diseases classified as metabolic disorders and cause more economic loss than infectious agents. Poultry metabolic diseases occur primarily in two body systems: (1) cardiovascular ailments, which in broiler chickens and turkeys are responsible for a major portion of the flock mortality; (2) musculoskeletal disorders, which account for less mortality, but in broilers and turkeys slow down growth (thereby reducing profit), and cause lameness, which remains a major welfare concern. In addition, conditions such as osteoporosis and hypocalcaemia in table-egg chickens reduce egg production and can kill.

Systematic pathogenesis and replication of avian hepatitis E virus in specific-pathogen-free adult chickens

Hepatitis E virus (HEV) is an important human pathogen. Due to the lack of a cell culture system and a practical animal model for HEV, little is known about its pathogenesis and replication. The discovery of a strain of HEV in chickens, designated avian HEV, prompted us to evaluate chickens as a model for the study of HEV. Eighty-five 60-week-old specific-pathogen-free chickens were randomly divided into three groups. Group 1 chickens (n=28) were each inoculated with 5 x 10(4.5) 50% chicken infectious doses of avian HEV by the oronasal route, group 2 chickens (n=29) were each inoculated with the same dose by the intravenous (i.v.) route, and group 3 chickens (n=28) were not inoculated and were used as controls. Two chickens from each group were necropsied at 1, 3, 5, 7, 10, 13, 16, 20, 24, 28, 35, and 42 days postinoculation (dpi), and the remaining chickens were necropsied at 56 dpi. Serum, fecal, and various tissue samples, including liver and spleen samples, were collected at each necropsy for pathological and virological testing. By 21 dpi, all oronasally and i.v. inoculated chickens had seroconverted. Fecal virus shedding was detected variably from 1 to 20 dpi for the i.v. group and from 10 to 56 dpi for the oronasal group. Avian HEV RNA was detected in serum, bile, and liver samples from both i.v. and oronasally inoculated chickens. Gross liver lesions, characterized by subcapsular hemorrhages or enlargement of the right intermediate lobe, were observed in 7 of 28 oronasally and 7 of 29 i.v. inoculated chickens. Microscopic liver lesions were mainly lymphocytic periphlebitis and phlebitis. The lesion scores were higher for oronasal (P=0.0008) and i.v. (P=0.0029) group birds than for control birds. Slight elevations of the plasma liver enzyme lactate dehydrogenase were observed in infected chickens. The results indicated that chickens are a useful model for studying HEV replication and pathogenesis. This is the first report of HEV transmission via its natural route in a homologous animal model.

The putative capsid protein of the newly identified avian hepatitis E virus shares antigenic epitopes with that of swine and human hepatitis E viruses and chicken big liver and spleen disease virus

We recently identified a novel virus, designated avian hepatitis E virus (avian HEV), from chickens with hepatitis-splenomegaly (HS) syndrome in the USA. We showed that avian HEV is genetically related to swine and human HEVs. Here we report the antigenic cross-reactivity of the putative open reading frame 2 (ORF2) capsid protein of avian HEV with those of swine and human HEVs and the Australian chicken big liver and spleen disease virus (BLSV). The region encoding the C-terminal 268 amino acid residues of avian HEV ORF2 was cloned into expression vector pRSET-C. The truncated ORF2 protein was expressed in E. coli as a fusion protein and purified by affinity chromatography. Western blot analysis revealed that the avian HEV ORF2 protein reacted with antisera against the Sar-55 strain of human HEV and with convalescent antisera against swine HEV and the US2 strain of human HEV, as well as with antiserum against BLSV. Convalescent sera from specific-pathogen-free chickens experimentally infected with avian HEV also reacted with the recombinant capsid proteins of swine HEV and Sar-55 human HEV. Antisera against the US2 human HEV also reacted with recombinant ORF2 proteins of both swine HEV and Sar-55 human HEV. The antigenic cross-reactivity of the avian HEV putative capsid protein with those of swine and human HEVs was further confirmed, for the most part, by ELISA assays. The data indicate that avian HEV shares certain antigenic epitopes in its putative capsid protein with swine and human HEVs, as well as with BLSV. The results have implications for HEV diagnosis and taxonomy.

Classification of grossly detectable abnormalities and conditions seen at postmortem in Canadian poultry abattoirs according to a hazard identification decision tree

This study was designed to review all grossly detectable abnormalities and conditions (GDACs) encountered in poultry in Canadian abattoirs to determine which have potential to cause adverse health effects for the consumer. Review of the literature and consultation with scientists in the field of microbiology, epidemiology, poultry pathology, chemistry, and meat inspection served to generate an inventory of GDACs, and a decision tree containing algorithms was developed to identify GDACs potentially representing a health hazard to consumers. Through the use of the decision tree, GDACs were classified into different categories with regard to the risk they represent to humans. A number of GDACs were identified as being of potential concern from a food safety perspective, namely Erysipelas, fowl cholera, Campylobacteriosis, clostridial diseases, hepatitis/enteritis associated with Helicobacter, Listeriosis, Salmonella infections (nontyphoid infections, Salmonella arizonae, pullorum disease, and fowl typhoid), Staphylococcosis, and Toxoplasmosis. Further characterization--i.e., hazard characterization, exposure assessment, and risk characterization--is required to quantify or better characterize the probability that products derived from affected carcasses may affect the consumer as well as the resulting consequences. Risk assessment is a dynamic process. Results presented in this paper are based on available information and expert opinion. As new information is obtained, the inventory of GDACs and their classification may be modified.

Genetic identification and characterization of a novel virus related to human hepatitis E virus from chickens with hepatitis-splenomegaly syndrome in the United States

Hepatitis-splenomegaly (HS) syndrome is an emerging disease in chickens in North America; the cause of this disease is unknown. In this study, the genetic identification and characterization of a novel virus related to human hepatitis E virus (HEV) isolated from bile samples of chickens with HS syndrome is reported. Based upon the similar genomic organization and significant sequence identity of this virus with HEV, the virus has been tentatively named avian HEV in order to distinguish it from human and swine HEV. Electron microscopy revealed that avian HEV is a non-enveloped virus particle of 30-35 nm in diameter. The sequence of the 3' half of the viral genome ( approximately 4 kb) was determined. Sequence analyses revealed that this genomic region contains the complete 3' non-coding region, the complete genes from open reading frames (ORFs) 2 and 3, the complete RNA-dependent RNA polymerase (RdRp) gene and a partial helicase gene from ORF 1. The helicase gene is the most conserved gene between avian HEV and other HEV strains, displaying 58-61% aa and 57-60% nt sequence identities. The RdRp gene of avian HEV shares 47-50% aa and 52-53% nt sequence identities and the putative capsid gene (ORF 2) of avian HEV shares 48-49% aa and 48-51% nt sequence identities with the corresponding regions of other known HEV strains. Phylogenetic analysis indicates that avian HEV is genetically related to, but distinct from, other known HEV strains. This discovery has important implications for HEV animal models, nomenclature and natural history.

Amyloid arthropathy in chickens

The present paper presents an overview of current knowledge of amyloid arthropathy in chickens, and covers the pathogenesis of amyloidosis in general and in birds, field cases reported, and the studies performed to assess the amyloidogenicity of various agents compared to that of Enterococcus faecalis. An animal model of amyloid arthropathy is presented, as are studies on the pathogenesis of arthropathic and amyloidogenic E. faecalis infections in brown layers. The review concludes with a description of the pathology of amyloid arthropathy, the biochemical characterization of the chicken joint amyloid protein as being of the AA type, investigation of the serum amyloid A (SAA) gene involved, and local SAA mRNA expression in joint and liver.

The role of various agents in chicken amyloid arthropathy

The results of an inventory of field cases of amyloid arthropathy in chickens and of routine post-mortem recordings over a two years period are described. Studies were also performed to evaluate the amyloidogenic potential of arthrotropic bacterial species (Staphylococcus aureus, Escherichia coli and Salmonella enteritidis) isolated from chickens as well as several Enterococcus faecalis isolates compared to the amyloidogenic E. faecalis isolate (previously isolated from amyloidotic joints). As chicken anemia virus was also isolated from amyloidotic joints of field cases, it was also screened for its amyloidogenic potential. In another experiment, Mycoplasma synoviae, inactivated E. faecalis isolate 6085.94, Freund's adjuvant and an arthrotropic reovirus field isolate were also screened for amyloidogenicity by intra-articular injection. These studies showed that the ability to elicit extensive amyloid arthropathy is reserved primarily to E. faecalis, but that this property is not common to every E. faecalis isolate. Intra-articular application of complete Freund's adjuvant led to the formation of extensive joint amyloid deposits. Of the other micro-organisms studied, S. aureus, S. enteritidis and E. coli were also able to cause joint amyloidosis, but in very small amounts. Inactivated E. faecalis, chicken anemia virus and reovirus did not cause amyloid arthropathy after intra-articular inoculation. This study is consistent with results of the analyses of previous field cases and of the induction of amyloid arthropathy in chickens, suggesting a considerable role for E. faecalis in this clinical-pathological entity. Finally, strain typing by analysis of chromosomal DNA restriction endonuclease digests by pulsed-field gel electrophoresis (PFGE) of amyloidogenic, non-amyloidogenic, amyloid-associated and other E. faecalis isolates from various origins showed that all amyloidogenic and amyloid-associated E. faecalis isolates had similar restriction digests, suggesting clonal spread.