Historical Investigation of Fowl Adenovirus Outbreaks in South Korea from 2007 to 2021: A Comprehensive Review

A sandwich amperometric immunosensor for the detection of fowl adenovirus group I based on bimetallic Pt/Ag nanoparticle-functionalized multiwalled carbon nanotubes

An enzyme-free sandwich amperometric immunosensor based on bimetallic Pt/Ag nanoparticle (Pt/AgNPs)-functionalized chitosan (Chi)-modified multiwalled carbon nanotubes (MWCNTs) as dual signal amplifiers and Chi-modified MWCNTs (MWCNTs-Chi) as substrate materials was developed for ultrasensitive detection of fowl adenovirus group I (FAdV-I). MWCNTs have a large specific surface area, and many accessible active sites were formed after modification with Chi. Hence, MWCNTs-Chi, as a substrate material for modifying glassy carbon electrodes (GCEs), could immobilize more antibodies (fowl adenovirus group I-monoclonal antibody, FAdV-I/MAb). Multiple Pt/AgNPs were attached to the surface of MWCNTs-Chi to generate MWCNTs-Chi-Pt/AgNPs with high catalytic ability for the reaction of H2O2 and modified active sites for fowl adenovirus group I-polyclonal antibody (FAdV-I/PAb) binding. Amperometric i-t measurements were employed to characterize the recognizability of FAdV-I. Under optimal conditions, and the developed immunosensor exhibited a wide linear range (100.93 EID50 mL-1 to 103.43 EID50 mL-1), a low detection limit (100.67 EID50 mL-1) and good selectivity, reproducibility and stability. This immunosensor can be used in clinical sample detection.

Conflicting Evidence between Clinical Perception and Molecular Epidemiology: The Case of Fowl Adenovirus D

Fowl adenoviruses (FAdVs, species FAdV-A/-E) are responsible for several clinical syndromes reported with increasing frequency in poultry farms in the last decades. In the present study, a phylodynamic analysis was performed on a group of FAdV-D Hexon sequences with adequate available metadata. The obtained results demonstrated the long-term circulation of this species, at least several decades before the first identification of the disease. After a period of progressive increase, the viral population showed a high-level circulation from approximately the 1960s to the beginning of the new millennium, mirroring the expansion of intensive poultry production and animal trade. At the same time, strain migration occurred mainly from Europe to other continents, although other among-continent connections were estimated. Thereafter, the viral population declined progressively, likely due to the improved control measures, potentially including the development and application of FAdV vaccines. An increase in the viral evolutionary rate featured this phase. A role of vaccine-induced immunity in shaping viral evolution could thus be hypothesized. Accordingly, several sites of the Hexon, especially those targeted by the host response were proven under a significant pervasive or episodic diversifying selection. The present study results demonstrate the role of intensive poultry production and market globalization in the rise of FAdV. The applied control strategies, on the other hand, were effective in limiting viral circulation and shaping its evolution.

Genomic and Pathologic Characterization of the First FAdV-C Serotype 4 Isolate from Black-Necked Crane

Fowl adenoviruses (FAdVs) are distributed worldwide in poultry and incriminated as the etiological agents for several health problems in fowls, and are capable of crossing species barriers between domestic and wild fowls. An FAdV strain was, for the first time, isolated from black-necked crane in this study, and was designated as serotype 4 Fowl aviadenovirus C (abbreviated as BNC2021) according to the phylogenetic analysis of its DNA polymerase and hexon gene. The viral genomic sequence analysis demonstrated that the isolate possessed the ORF deletions that are present in FAdV4 strains circulating in poultry fowls in China and the amino acid mutations associated with viral pathogenicity in the hexon and fiber 2 proteins. A viral challenge experiment with mallard ducks demonstrated systemic viral infection and horizontal transmission. BNC2021 induced the typical clinical signs of hepatitis-hydropericardium syndrome (HHS) with swelling and inflammation in multiple organs and showed significant viral replication in all eight organs tested in the virus-inoculated ducks and their contactees at 6 dpi. The findings highlight the importance of surveillance of FAdVs in wild birds.

Complete genome sequence and pathogenicity analysis of a highly pathogenic FAdV-4 strain

Fowl adenovirus serotype 4 (FAdV-4) is a double-stranded DNA virus that mainly infects broiler chickens and has caused huge economic losses to the poultry industry. Recently, an FAdV-4 strain, SDLC202009, the causative pathogen of hydropericardium-hepatitis syndrome (HHS) in Liaocheng, Shandong, was isolated from commercial laying hens and propagated in specific pathogen free SPF chicken embryos. Pathogenicity studies showed that SDLC202009 could infect SPF chicken embryos and chickens, with a mortality rate of 100%. The complete genome was sequenced, and phylogenetic analysis showed that SDLC202009 belonged to the FAdV-4 cluster, with a genome length of 43, 077 bp. The SDLC202009 had 99.9% identity with the JSJ13 and SD1601, which were recently isolated in China. Compared to the recently isolated strain in China, SDLC202009 had deleted open reading frame 19 (ORF19), ORF27, ORF48, and ORF0. SDLC202009 harbored amino acid site mutations in the main structural proteins hexon, fiber1, and fiber2 similar with those in highly pathogenic strains. Furthermore, SDLC202009 showed unique mutations in hexon A571P, fiber1 E216K, and fiber2 N98K. In summary, our findings provide theoretical support for prevention and control of the HHS.

Epidemiological Survey and Risk Factor Analysis of 14 Potential Pathogens in Golden Snub-Nosed Monkeys at Shennongjia National Nature Reserve, China

Golden snub-nosed monkeys (Rhinopithecus roxellanae) belong to Class A, the highest level of endangered primate species. Exploring the infection status of potential pathogens in golden snub-nosed monkeys is important for controlling associated diseases and protecting this species. The objective of this study was to investigate the seroprevalence for a number of potential pathogens and the prevalence of fecal adenovirus and rotavirus. A total of 283 fecal samples were collected from 100 golden snub-nosed monkeys in December 2014, June 2015, and January 2016; 26 blood samples were collected from 26 monkeys in June 2014, June 2015, January 2016 and November 2016 at Shennongjia National Reserve in Hubei, China. The infection of 11 potential viral diseases was examined serologically using an Indirect Enzyme-linked Immunosorbent Assay (iELISA) and Dot Immunobinding Assays (DIA), while the whole blood IFN-γ in vitro release assay was used to test tuberculosis (TB). In addition, fecal Adenovirus and Rotavirus were detected using Polymerase Chain Reaction (PCR). As a result, the Macacine herpesvirus-1 (MaHV-1), Golden snub-nosed monkey cytomegalovirus (GsmCMV), Simian foamy virus (SFV) and Hepatitis A virus (HAV) were detected with the seroprevalence of 57.7% (95% CI: 36.9, 76.6), 38.5% (95% CI: 20.2, 59.4), 26.9% (95% CI: 11.6, 47.8), and 7.7% (95% CI: 0.0, 84.2), respectively. Two fecal samples tested positive for Adenovirus (ADV) by PCR, with a prevalence of 0.7% (95% CI: 0.2, 2.5), and further, the amplification products were sequenced. Phylogenetic analysis revealed that they belonged to the HADV-G group. However, other pathogens, such as Coxsackievirus (CV), Measles virus (MeV), Rotavirus (RV), Simian immunodeficiency virus (SIV), Simian type D retroviruses (SRV), Simian-T-cell lymphotropic virus type 1 (STLV-1), Simian varicella virus (SVV), Simian virus 40 (SV40) and Mycobacterium tuberculosis complex (TB) were negative in all samples. In addition, a risk factor analysis indicated that the seroprevalence of MaHV-1 infection was significantly associated with old age (≥4 years). These results have important implications for understanding the health status and conservation of the endangered golden snub-nosed monkey population at Shennongjia Nature Reserve.

An Inactivated Novel Trivalent Vaccine Provides Complete Protection against FAdV-4 Causing Hepatitis-Hydropericardium Syndrome and FAdV-8b/-11 Causing Inclusion Body Hepatitis

Outbreaks of hepatitis-hydropericardium syndrome (HHS) caused by fowl adenovirus serotype 4 (FAdV-4) and inclusion body hepatitis (IBH) related to FAdV-8b and FAdV-11 have been increased in chickens in China since 2015. Clinical concurrent infections of FAdV-4, FAdV-8b, and FAdV-11 are quite common, yet there are no commercially available trivalent vaccines against infection by these three serotypes. In our previous study, a bivalent vaccine based on a recombinant FAdV-4, of which fiber-1 was replaced with the fiber of FAdV-8b, has been developed. In this study, a novel recombinant rFAdV-4-fiber/8b + 11 was constructed by inserting FAdV-11 fiber gene into the 1966-bp deletion region of rFAdV-4-fiber/8b genome. The in vitro replication ability of the rFAdV-4-fiber/8b + 11 was similar to the parental FAdV-4. One dose immunization with the inactivated rFAdV-4-fiber/8b + 11 vaccine generated robust immune responses against FAdV-4, FAdV-8b, and FAdV-11, and provided efficient clinical protection against FAdV-4, FAdV-8b, and FAdV-11 challenge. This study provides a novel strategy for developing potential trivalent vaccines for the prevention and control of HHS and IBH.

Detection, Quantification and Molecular Characterization of Fowl Adenoviruses Circulating in Ecuadorian Chicken Flocks during 2019-2021

Fowl adenoviruses are a group of pathogens that cause large economic losses worldwide in the poultry industry, in addition to producing a wide range of diseases, such as IBH, HHS, and enteric and respiratory diseases. The objective of this study was to quantify, identify, and molecularly characterize the types of FAdV circulating in commercial poultry farms (broilers, breeders, and layers) in Ecuador from 2019 to 2021. Molecular characterization was performed by PCR, quantification by qPCR, and subsequent sequencing for each positive sample. The results indicated that the FAdV genotypes circulating in our country are FAdV-2/D2, FAdV-6/E1, FAdV-8a/E2, and FAdV-11/D3; the samples were grouped into different groups that contain sequences that were obtained from countries in Africa, Asia, and America, and that are found in birds at different ages, since early age where can cause different clinical signs, such as diarrhea, ruffled feathers and dwarfism. Therefore, these results indicate that several genotypes of the virus are circulating in commercial poultry flocks, suggesting that biosecurity measures on farms should be improved, in addition to carrying out new or improved vaccination plans.

Epidemiology, pathology, prevention, and control strategies of inclusion body hepatitis and hepatitis-hydropericardium syndrome in poultry: A comprehensive review

Infection with fowl adenoviruses (FAdVs) can result in a number of syndromes in the production of chicken, including inclusion body hepatitis (IBH), hepatitis-hydropericardium syndrome (HHS), and others, causing enormous economic losses around the globe. FAdVs are divided into 12 serotypes and five species (A-E; 1-8a and 8b-11). Most avian species are prone to infection due to the widespread distribution of FAdV strains. The genus aviadenovirus, which is a member of the adenoviridae family, is responsible for both IBH and HHS. The most popular types of transmission are mechanical, vertical, and horizontal. Hepatitis with basophilic intranuclear inclusion bodies distinguishes IBH, but the buildup of translucent or straw-colored fluid in the pericardial sac distinguishes HHS. IBH and HHS require a confirmatory diagnosis because their clinical symptoms and postmortem abnormalities are not unique to those conditions. Under a microscope, the presence of particular lesions and inclusion bodies may provide clues. Traditional virus isolation in avian tissue culture is more delicate than in avian embryonated eggs. Additionally, aviadenovirus may now be quickly and precisely detected using molecular diagnostic tools. Preventive techniques should rely on efficient biosecurity controls and immunize breeders prior to production in order to protect progeny. This current review gives a general overview of the current local and global scenario of IBH, and HHS brought on by FAdVs and covers both their issues and preventative vaccination methods.

An inactivated novel chimeric FAdV-4 containing fiber of FAdV-8b provides full protection against hepatitis-hydropericardium syndrome and inclusion body hepatitis

Fowl adenovirus serotype 4 (FAdV-4) and FAdV-8b are causative agents of hepatitis-hydropericardium syndrome (HHS) and inclusion body hepatitis (IBH), respectively. HHS and IBH co-infections were often reported in clinical, yet there are no commercially available bivalent vaccines for prevention and control of both FAdV-4 and -8b. In the present study, a chimeric FAdV-4 was firstly generated by substituting fiber-1 of FAdV-4 with fiber of FAdV-8b. The chimeric virus, rFAdV-4-fiber/8b, exhibited similar replication ability in vitro and pathogenicity in vivo to the parental wild type FAdV-4. A single dosage of vaccination with the inactivated rFAdV-4-fiber/8b induced high antibody titers against fiber-2 of FAdV-4 and fiber of FAdV-8b and provided full protection against FAdV-4 and -8b challenge. These results demonstrated that fiber of FAdV-8b could replace the role of fiber-1 of FAdV-4 in the process of viral infection, and rFAdV-4-fiber/8b could be used to make a potential bivalent vaccine for the control and prevention of HHS and IBH.

Epidemiological survey of avian adenovirus in China from 2015 to 2021 and the genetic variability of highly pathogenic Fadv-4 isolates

The prevalence of poultry adenovirus in China is determined using clinical diagnosis, molecular biological testing, serological testing, and LMH cell virus isolation. These methods can track and test key poultry and waterfowl breeding areas across the country. From 2015 to 2021, 9613 suspected adenovirus samples were collected from 28 provinces. After the first generation of gene sequencing, a total of 2210 hexo gene fragments were obtained. Among them, FAdV-1 type accounted for 7.65%, FAdV-2 type accounted for 5.34%, FAdV-3 type accounted for 2.04%, FAdV-4 type accounted for 38.24%, FAdV-5 type accounted for 2.17%, FAdV-6 type accounted for 0.32%, FAdV-7 type accounted for 0.77%, FAdV-8a type accounted for 10.63%, FAdV-8b type accounted for 11.58%, FAdV-9 type accounted for 0.50%, FAdV-10 type accounted for 8.10%, and FAdV-11 type accounted for 12.67%. A total of 877 FAdV strains were isolated from FAdV suspected samples by seeding LMH cells, and there were 475 FAdV-4 strains among them. A total of 473 isolates were highly pathogenic FAdV-4, and the percentage of amino acid homology with the highly pathogenic FAdV-4 reference strains was >99.1%. Two isolates were non-pathogenic, and the amino acid homology with the ON1 reference strain was >99.6%. Part of the amino acid positions of the hexon gene have mutations, including positions 188, 193, 195, 238, and 240.

Current epidemiological situation in the context of inclusion body hepatitis in poultry flocks in Poland

The research has been undertaken to understand the spreading of adenovirus strains in Poland's poultry flocks in the last six years. One hundred and forty-nine herds suspected of infection with adenoviruses were tested and the presence of poultry adenoviruses was found in 86 studied herds which were about 57,71% of examined flocks. Thirty-eight (44.18%) strains were connected with the infection of inclusion body hepatitis, 11 (12.79%) strains were isolated from digestive system dysfunction, 33 (38.37%) strains had been obtained from the flocks with no symptomatic changes/behaviour, and four (4.65%) strains were obtained from flocks with the manifestation of depression. Sequencing analysis was based on Loop L1 region of the HVR1-4 fragment of the hexon gene. The adenovirus strains were classified into five species FAdV-A-E, belonging to the following eight serotypes: FAdV-1/A, FAdV-5/B, FAdV-3/10/C, FAdV-9/11/D, and FAdV-7/8a/E. The most common serotype in poultry turned out to be type/species FAdV-11/D, FAdV-5/B, and FAdV-7/8b/E while the least frequent was type/species FAdV-3/10/C (only four and two strains respectively of this types were isolated with the following range: FAdV-1/A 6 (6.97%), FAdV-5/B 24 (27,90%), FAdV-3/C 4 (4,65%), FAdV-10/C 2 (2,32%), FAdV-11/D 36 (41,86%), and FAdV-E 14 (16.27%). The understanding of genetic diversity, geographic distribution, and antigenic properties of fowl adenovirus strains (FAdVs) isolated in Poland have been evaluated.

The Role of Hexon Amino Acid 188 Varies in Fowl Adenovirus Serotype 4 Strains with Different Virulence

Hepatitis-hydropericardium syndrome (HHS) induced by fowl adenovirus serotype 4 (FAdV-4) has caused huge economic losses to poultry industries. The key genes responsible for different virulence of FAdV-4 strains are not fully elucidated. Previous studies indicated that hexon of pathogenic FAdV-4 has a conserved arginine (R) at position 188, and a conserved isoleucine (I) is present at this position in reported nonpathogenic FAdV-4. Recently, it was reported that R188 of hexon is the determinant site for pathogenicity of the emerging Chinese FAdV-4 strain. However, the role of hexon amino acid 188 (aa188) has not been examined in the nonpathogenic FAdV-4 strain. In this study, three recombinant FAdV-4 viruses, H/H/R188I, O/O/I188R, and H/O/I188R, were constructed by mutating hexon aa188 of FAdV-4 pathogenic strain CH/HNJZ/2015 (H) and nonpathogenic strain ON1 (O), and pathogenicity was assessed in specific-pathogen-free (SPF) chickens. Consistent with previous findings, H/O/I188R exhibited pathogenicity similar to that of CH/HNJZ/2015, yet H/H/R188I induced no mortality. Unexpectedly, all chickens infected with O/O/I188R survived. Postmortem examination of O/O/I188R-infected chickens showed typical lesions of inclusion body hepatitis rather than HHS. Expression of proinflammatory cytokines in CH/HNJZ/2015- and H/O/I188R-infected chickens was significantly higher than that in H/H/R188I-, ON1-, and O/O/I188R-infected chickens. Analysis of predicted hexon protein structures indicated that aa188 mutation leads to conformational changes in the L1 loop of HNJZ-hexon but not in ON1-hexon. In summary, the present study demonstrated that the role of hexon aa188 in the virulence of FAdV-4 varies between different strains. Induction of HHS requires factors aside from hexon aa188 in the emerging Chinese FAdV-4 strain.

IMPORTANCE HHS induced by FAdV-4 has caused huge economic losses to the poultry industry. The key determinants for the different virulence of FAdV-4 have not been fully elucidated. Here, we investigated the role of hexon aa188 in FAdV-4 strains with different virulence and showed that the role of hexon aa188 varies in FAdV-4 strains with different genetic contents. The hexon R188 may be the key amino acid for causing inclusion body hepatitis by the pathogenic FAdV-4 strain, and induction of HHS by FAdV-4 may need other viral cofactors. Moreover, the hexon R188I mutation greatly affected the expression of proinflammatory cytokines induced by the pathogenic strain CH/HNJZ/2015, but no significant difference was observed between the nonpathogenic strain ON1 and ON1 with hexon I188R mutation. We found that hexon aa188 mutation induced conformational changes to hexon protein in CH/HNJZ/2015 but not in ON1, which might be the underlying reason for the changing virulence.