Infectious Bronchitis Virus Genotypes Research Articles

Clinical, pathological, and genotypic analysis of infectious bronchitis virus in broiler chickens in the Abu Dhabi Emirate, United Arab Emirates

BackgroundInfectious Bronchitis (IB), caused by the infectious bronchitis virus (IBV), is a significant contagious respiratory disease in the poultry industry. The emergence of new variants represents a global challenge for the diagnosis and control of the disease. Despite vaccination efforts in poultry farms in the Abu Dhabi Emirate, United Arab Emirates (UAE), outbreaks continue to occur, raising concerns about the efficacy of vaccination protocols and the potential emergence of new viral strains. This study aims to provide information on clinical, pathological, and genotypes of IBV detected within the Abu Dhabi Emirate, during 2022–2023.MethodsEpidemiological data were collected from twelve suspected IB outbreaks across seven broiler farms located in the Abu Dhabi Emirate. The cases were investigated through clinical and pathological examinations and Forty-six samples, including lung, spleen, kidney tissues, and oro-cloacal swabs, were collected for further analysis. The virus was detected by RT-qPCR assay, genotyping was determined by phylogenetic analysis of the Spike (S)-1 gene, and differentiation between field and vaccine strains was determined by comparing their sequences.ResultsThe age of the affected flocks varies from 2 to 5 weeks. The highest morbidity, mortality and case fatality rates were 36, 33, and 95%, respectively. Necropsy examination revealed characteristic respiratory and renal pathological lesions. Phylogenetic analysis revealed a co-circulation of three lineages of IBV genotype GI-13 or 4/91 serotype (81.8%), GI-1 or Massachusetts serotype (9.1%) and GI-23 or Middle East serotype (9.1%). Approximately 90.9% of the strains classified within GI-1 and G1-13 lineages are 99 to 100% identical to 4/91 and Mass serotypes, respectively, and are considered as vaccine strains. Two strains (9.1%) classified within GI-23 lineage have a < 99% identity to the 4/91 and Mass serotypes vaccine strains and are considered as filed strains.ConclusionCo-circulation of three IBV lineages (GI-13, GI-1, and GI-23) in the Abu Dhabi broiler flocks showing IB symptoms were detected. This complex scenario of different IBV lineages circulation may account for the persistent outbreaks despite vaccination efforts. The results of the study are crucial for optimum IB vaccination and monitoring strategies or designing new vaccines based on local IBV field strains.

First detection of D181 genotype of infectious bronchitis in poultry flocks of Morocco

BackgroundThis paper reports the first pathological and molecular characterization of the novel variant of infectious bronchitis virus (IBV) D181 in poultry flocks in Morocco and Africa.MethodsThe study includes six poultry farms, involving three flocks of layers aged between 28 and 67 weeks and three broiler flocks aged 27, 39 and 42 days from different regions of Morocco. In all affected layer flocks, a severe drop in egg production with poor eggshell quality was reported. Necropsy of dead birds was carried out, and samples of trachea, lungs, oviduct, ovaries, and kidneys were fixed in 10% neutral buffered formalin for histopathologic examinations, while other portions were stored at -20 °C for molecular analysis. Real time RT-qPCR for IBV gene group was performed, and IBV variants were identified. Partial S1 gene sequences were amplified by conventional RT-PCR, sequenced, and aligned for phylogenetic and amino acid similarity analysis.ResultsNecropsy of dead birds revealed misshapen and hemorrhagic ovarian follicles with an edematous oviduct and severe reaction in the cecal tonsils. A caseous material accumulation in the sinus was noted in few birds. In contrast, the broiler flocks exhibited respiratory clinical signs such as difficulty in breathing, sneezing, tracheal rales, watery eyes and lethargy, associated with a decrease in feed consumption. Mortality in broiler ranged from 2 to 15%. Histopathological analysis of samples showed a lympho-plasmocytic inflammation in the oviduct, trachea, and lungs. Individual necrosis of epithelial cells, with sloughing of the bronchial epithelium and accumulation of desquamated cells with mucus in the airways, was observed in some birds. Partial S1 gene sequencing and phylogenetic analyses showed that the Moroccan strains were very closely related to D181 strains isolated in Dutch layers and breeders in 2018. Nucleotide sequence identities reached 90.9–95% with the Dutch isolates (strain CK/NL/D181/2018).ConclusionOur sequencing results demonstrate for the first time that the D181 IBV genotype is circulating in Moroccan poultry. These findings justify permanent monitoring of circulating strains in order to appropriately adjust vaccination strategies to align with the evolving field situation.

Genotyping of infectious bronchitis virus in Canada.

From 2014-2023, infectious bronchitis virus (IBV) was detected in 6,589 samples from Canada, and partial nucleotide (nt) sequences of the IBV spike protein (S) gene were determined for 1,678 samples. Based on their S gene nt sequence identities and origin, Canadian IBVs could be classified into 4 groups: 1) 50.3% were variant viruses related to strains described in the United States; 2) 45.6% were vaccine-like viruses; 3) 2.1% were Eurasian viruses; 4) 2.0% were Canadian variants. Outbreaks with IBVs related to strains CAL1734/04, 4/91, and DMV/1639/11 were often associated with more severe disease in all chicken commodity groups. With the emergence of numerous IBV strains, the severity of infection and number of affected flocks increased. Outbreaks with various IBV strains overlapped in their emergence, peaked, and regressed, but the introduction of DMV/1639/11 has resulted in a continuous field challenge since its first detection in 2015.

Concurrent infection of Infectious Bronchitis Virus and Mycoplasma gallisepticum in a backyard poultry

This study reports the co-existence of two S1 mutants of GI-13 (4/91-like) Infectious Bronchitis Virus (IBV) and Mycoplasma gallisepticum (MG) in a backyard poultry flock that had non-vaccinated 30 broiler chickens and four turkey pullets. Serum samples and tracheal swabs were taken from the chickens and turkey pullets showing respiratory signs. Serum antibody levels were measured using commercial ELISA kits against IBV, Avian Influenza Virus (AIV), Newcastle Disease Virus (NDV), Avian Metapneumovirus (AMPV), MG, Mycoplasma synoviae (MS), and Ornithobacterium rhinotracheale (ORT). Additionally, tracheal swabs were tested for AIV serotypes H5, H7, and H9, NDV, IBV, AMPV, MG, MS, Pasteurella multocida, Avibacterium paragallinarum, and Bordetella avium by circular amplification technology (CAT). Anti-MS, -IBV, -MG, -NDV, -AMPV, and -ORT IgG antibodies were detected in some chicken sera, while anti-NDV, -MG, -MS, and -ORT IgG antibodies were detected in turkey sera. All avian tracheal swabs were positive for MG. However, IBV was only detected in chicken tracheal samples tested by CAT. The IBV strains were genotyped by sequencing a part of the S1 glycoprotein gene. The alignment analyses of two isolates showed 99.35% and 98.69% nucleotide similarities and 99.02% amino acid similarities with the 4/91 IBV vaccine and field strains. Two mutants showed 99.35% nucleotide and 100% amino acid sequence identity to each other. The turkeys and chickens in the flock had MG and MG/IBV co-infections, respectively. Consequently, the presence of mutants of 4/91 (GI-13) IBV genotypes and MG found in backyard poultry could be a potential epidemiological source for commercial flocks in poultry integrations.

Control of Field Infectious Bronchitis Virus Genotype GI-23 (Variant 2) Using Combined Heterologous Vaccine Genotype Strains GI-13 (1/96) and GI-1 (H120)

Infectious bronchitis (IB) is a disease with significant economic impacts both on the costs of control strategies and on productive losses. Various vaccination protocols are applied, depending on homologous or heterologous protection against IB and finding the optimal balance between costs and benefits as a choice by a responsible veterinarian. The current case study aimed to demonstrate the efficacy of a heterologous vaccine combination against field IBV GI-23 (Variant 2) infection when vaccination quality was properly monitored. Two groups, each consisting of six flocks, were examined before and after improving the quality of IB vaccine application in the hatchery. These groups were vaccinated with H-120 and 1/96 vaccine strains for heterologous protection. The study involved field visits, necropsies, serology via ELISA, and oropharyngeal sampling for RT-PCR follow-up activities. Moreover, performance parameters including average body weight, feed conversion ratio, and 7 days plus total mortality were analyzed at the end of the production cycle at 40-45 days of age. Results indicated that the group with enhanced vaccination quality in the hatchery exhibited a significant decrease in IBV titers and an absence of IBV GI-23 field infection. Additionally, there was an improvement in performance data in terms of average body weight, FCR and total mortality. Hatchery vaccination proved to be more controllable and practical compared to traditional on-farm vaccination, ensuring better control of the vaccination process and massive coverage of the farm population. Keywords: Heterologous protection, Infectious bronchitis, Vaccine strain 1/96, Variant 2

The N545S and K717N substitution at the N-glycosylation sites of the S2 subunit of avian infectious bronchitis virus can significantly enhance viral pathogenicity

The S2 subunit of infectious bronchitis virus (IBV) is a heavily glycosylated protein that can impact various characteristics of the virus. It is currently known that N-glycosylation modifications are predominantly located on the S2 subunit. However, the exact role of their N-glycosylation modification remains undisclosed. To elucidate the function of these N-glycosylation sites, we identified 14 common sites distributed on the S2 subunit of the 5 genotypes of IBV in present study. Subsequently, we selected 7 sites to generate mutants and assessed their impact on viral virulence, replication ability, and antigenicity. Our finding revealed that only 2 substitutions, N545S and K717N, increased the viral replication titer and antigenicity, and ultimately the pathogenicity in chicks. To delve into the mechanisms underlying this increased pathogenicity, we discovered that K717N can change the structure of antigenic epitopes. The N545S substitution not only influenced antigenic epitope structure, but also enhanced the ability of the virus to enter CEKs during the early stages of viral replication. These results suggest that the enhanced viral pathogenicity associated with N545S and K717N substitutions is multifaceted, with acceleration of the viral membrane fusion process and alterations in epitope structure representing crucial factors in the capability of N-glycosylation modifications to boost viral virulence. These insights provide valuable guidance for the efficient development of live attenuated vaccines.

Prevalence, Genotype Diversity, and Distinct Pathogenicity of 205 Gammacoronavirus Infectious Bronchitis Virus Isolates in China during 2019-2023.

Gammacoronavirus infectious bronchitis virus (IBV) causes a highly contagious disease in chickens and seriously endangers the poultry industry. The emergence and co-circulation of diverse IBV serotypes and genotypes with distinct pathogenicity worldwide pose a serious challenge to the development of effective intervention measures. In this study, we report the epidemic trends of IBV in China from 2019 to 2023 and a comparative analysis on the antigenic characteristics and pathogenicity of isolates among major prevalent lineages. Phylogenetic and recombination analyses based on the nucleotide sequences of the spike (S) 1 gene clustered a total of 205 isolates into twelve distinct lineages, with GI-19 as a predominant lineage (61.77 ± 4.56%) exhibiting an overall increasing trend over the past five years, and demonstrated that a majority of the variants were derived from gene recombination events. Further characterization of the growth and pathogenic properties of six representative isolates from different lineages classified four out of the six isolates as nephropathogenic types with mortality rates in one-day-old SPF chickens varying from 20-60%, one as a respiratory type with weak virulence, and one as a naturally occurring avirulent strain. Taken together, our findings illuminate the epidemic trends, prevalence, recombination, and pathogenicity of current IBV strains in China, providing key information for further strengthening the surveillance and pathogenicity studies of IBV.

Heterologous maternal antibodies derived from infectious bronchitis vaccines prevent the development of lesions associated with false layer syndrome

Infectious bronchitis virus (IBV) strains of the Delmarva (DMV)/1639 genotype have been causing false layer syndrome (FLS) in the Eastern Canadian layer operations since the end of 2015. FLS is characterized by the development of cystic oviducts in layer pullets infected at an early age. Currently, there are no homologous vaccines for the control of this IBV genotype. Our previous research showed that a heterologous vaccination regimen incorporating Massachusetts (Mass) and Connecticut (Conn) IBV types protects layers against DMV/1639 genotype IBV. The aim of this study was to investigate the role of maternal antibodies conferred by breeders received the same vaccination regimen in the protection against the development of DMV/1639-induced FLS in pullets. Maternal antibody-positive (MA+) and maternal antibody-negative (MA−) female progeny chicks were challenged at 1 day of age and kept under observation for 16 weeks. Oviductal cystic formations were observed in 3 of 14 birds (21.4 %) in the MA− pullets, while the lesions were notably absent in the MA+ pullets. Milder histopathological lesions were observed in the examined tissues of the MA+ pullets. However, the maternal derived immunity failed to demonstrate protection against the damage to the tracheal ciliary activity, viral shedding, and viral tissue distribution. Overall, this study underscores the limitations of maternal derived immunity in preventing certain aspects of viral pathogenesis, emphasizing the need for comprehensive strategies to address different aspects of IBV infection.

Development of a colloidal gold immunochromatographic strip for rapid detection of avian coronavirus infectious bronchitis virus

Avian infectious bronchitis virus (IBV) still causes serious economic losses in the poultry industry. Currently, there are multiple prevalent genotypes and serotypes of IBVs. It is imperative to develop a new diagnosis method that is fast, sensitive, specific, simple, and broad-spectrum. A monoclonal hybridoma cell, N2D5, against the IBV N protein was obtained after fusion of myeloma SP2/0 cells with spleen cells isolated from the immunized Balb/c mice. The N2D5 monoclonal antibody (mAb) and the previously prepared mouse polyclonal antibody against the IBV N protein were used to target IBV as a colloidal gold–mAb conjugate and a captured antibody, respectively, in order to develop an immunochromatographic strip. The optimal pH and minimum antibody concentration in the reaction system for colloidal gold–mAb N2D5 conjugation were pH 6.5 and 30 μg/mL, respectively. Common avian pathogens were tested to evaluate the specificity of the strip and no cross-reaction was observed. The sensitivity of the strip for detecting IBV was 10−1.4522 EID50/mL. The strip showed a broad-spectrum cross-reactive capacity for detecting IBV antigens, including multiple IBV genotypes in China and all of the seven serotypes of IBV that are currently prevalent in southern China. Additionally, the result can be observed within 2 min without any equipment. The throat and cloacal swab samples of chickens that were artificially infected with three IBV strains were tested using the developed strip and the qPCR method; the strip test demonstrated a high consistency in detecting IBV via qPCR gene detection. In conclusion, the immunochromatographic strip that was established is rapid, sensitive, specific, simple, practical, and broad-spectrum; additionally, it has the potential to serve as an on-site rapid detection method of IBV and can facilitate the surveillance and control of the disease, especially in resource-limited areas.

Comparative pathogenicity of CA1737/04 and Mass infectious bronchitis virus genotypes in laying chickens.

Infectious bronchitis virus (IBV) is a respiratory virus causing atropism in multiple body systems of chickens. Recently, the California 1737/04 (CA1737/04) IBV strain was identified as one of the circulating IBV variants among poultry operations in North America. Here, the pathogenicity and tissue tropism of CA1737/04 IBV strain in specific-pathogen-free (SPF) hens were characterized in comparison to Massachusetts (Mass) IBV. In 30 weeks-old SPF hens, Mass or CA1737/04 IBV infections were carried out, while the third group was maintained as a control group. Following infection, we evaluated clinical signs, egg production, viral shedding, serology, necropsy examination, and histopathology during a period of 19 days. Also, certain tissue affinity parameters were investigated, which involved the localization of viral antigens and the detection of viral RNA copies in designated tissues. Our findings indicate that infection with CA1737/04 or Mass IBV strain could induce significant clinical signs, reduced egg production, and anti-IBV antibodies locally in oviduct wash and systemically in serum. Both IBV strains showed detectable levels of viral RNA copies and induced pathology in respiratory, renal, enteric, and reproductive tissues. However, the CA1737/04 IBV strain had higher pathogenicity, higher tissue tropism, and higher replication in the kidney, large intestine, and different segments of the oviduct compared to the Mass IBV strain. Both IBV strains shed viral genome from the cloacal route, however, the Mass IBV infected hens shed higher IBV genome loads via the oropharyngeal route compared to CA1737/04 IBV-infected hens. Overall, the current findings could contribute to a better understanding of CA1737/04 IBV pathogenicity in laying hens.

Differential Impact of Massachusetts, Canadian 4/91, and California (Cal) 1737 Genotypes of Infectious Bronchitis Virus Infection on Lymphoid Organs of Chickens.

Infectious bronchitis virus (IBV) induces severe economic losses in chicken farms due to the emergence of new variants leading to vaccine breaks. The studied IBV strains belong to Massachusetts (Mass), Canadian 4/91, and California (Cal) 1737 genotypes that are prevalent globally. This study was designed to compare the impact of these three IBV genotypes on primary and secondary lymphoid organs. For this purpose, one-week-old specific pathogen-free chickens were inoculated with Mass, Canadian 4/91, or Cal 1737 IBV variants, keeping a mock-infected control. We examined the IBV replication in primary and secondary lymphoid organs. The molecular, histopathological, and immunohistochemical examinations revealed significant differences in lesion scores and viral distribution in these immune organs. In addition, we observed B-cell depletion in the bursa of Fabricius and the spleen with a significant elevation of T cells in these organs. Further studies are required to determine the functional consequences of IBV replication in lymphoid organs.

Avian infectious bronchitis virus (AIBV) review by continent.

Infectious bronchitis virus (IBV) is a positive-sense, single-stranded, enveloped RNA virus responsible for substantial economic losses to the poultry industry worldwide by causing a highly contagious respiratory disease. The virus can spread quickly through contact, contaminated equipment, aerosols, and personal-to-person contact. We highlight the prevalence and geographic distribution of all nine genotypes, as well as the relevant symptoms and economic impact, by extensively analyzing the current literature. Moreover, phylogenetic analysis was performed using Molecular Evolutionary Genetics Analysis (MEGA-6), which provided insights into the global molecular diversity and evolution of IBV strains. This review highlights that IBV genotype I (GI) is prevalent worldwide because sporadic cases have been found on many continents. Conversely, GII was identified as a European strain that subsequently dispersed throughout Europe and South America. GIII and GV are predominant in Australia, with very few reports from Asia. GIV, GVIII, and GIX originate from North America. GIV was found to circulate in Asia, and GVII was identified in Europe and China. Geographically, the GVI-1 lineage is thought to be restricted to Asia. This review highlights that IBV still often arises in commercial chicken flocks despite immunization and biosecurity measures because of the ongoing introduction of novel IBV variants and inadequate cross-protection provided by the presently available vaccines. Consequently, IB consistently jeopardizes the ability of the poultry industry to grow and prosper. Identifying these domains will aid in discerning the pathogenicity and prevalence of IBV genotypes, potentially enhancing disease prevention and management tactics.

Comparative pathogenicity of infectious bronchitis virus Massachusetts and Delmarva (DMV/1639) genotypes in laying hens.

Infectious bronchitis (IB) is a highly contagious and acute viral disease of chicken caused by the infectious bronchitis virus (IBV) of the family Coronaviridae. Even with extensive vaccination against IB by the poultry industry, the occurrence of new IBV genotypes is a continuous challenge encountered by the global poultry industry. This experiment was designed to compare the pathogenicity of two IBV strains belonging to Massachusetts (Mass) and Delmarva DMV/1639 genotypes. Specific pathogen-free laying hens were challenged during the peak of production (30 weeks), keeping a mock-infected control group. During 21 days of observation following infection, a significant drop in egg production with miss-shaped and soft shells was observed in the DMV/1639 IBV-infected hens only. The DMV/1639 IBV infected group showed prolonged and higher cloacal viral shedding compared with the Mass IBV-infected group. At the end of the study (21 days post-infection), the viral genome loads in the respiratory, urogenital, and immune tissues were significantly higher in the DMV/1639 IBV-infected group compared with the Mass IBV-infected group. Macroscopic lesions such as distorted ova leading to egg peritonitis were observed only in the DMV/1639 IBV-infected group. Moreover, microscopic lesion scores were significantly higher in the lung, kidney, cecal tonsils, and oviduct of the DMV/1639 IBV-infected group compared with the Mass IBV-infected group. Finally, the apoptosis index in the kidney, ovary, magnum, isthmus, and shell gland was significantly higher in the DMV/1639 IBV-infected group compared with the control and Mass-infected groups. This study examined the pathogenicity of two IBV genotypes that are impacting the layer industry in North America.

Whole genome sequencing analysis of avian infectious bronchitis virus isolated in Hung Yen province in 2021

Infectious bronchitis is an acute disease in chickens caused by the Infectious Bronchitis Virus (IBV). The disease causes serious economic losses in many countries in the world that have chicken farming industries. Even though vaccines have been used, the disease is still very complicated in many provinces and cities in Vietnam. The reason is that the virus strains causing the disease in the field have many changes compared to the vaccine virus strains. Research showed that there are numerous strains and genotypes of IBV in Vietnam. However, only the S1 gene has been studied, and no research has been done on the full genome. In this study, the IBV strain causing disease in 2021 in Hung Yen Province (North Vietnam) was sequenced and analyzed for molecular characteristics. The analysis results showed that strain IBHYM belongs to genotype QX-like (GI-19) and has a close relationship with Chinese IBV strains. The IBHYM strain has higher nucleotide and amino acid similarities with strains of genotype QX-like (87.5% to 95% for nucleotide and 80.2% to 91.3% for amino acid) and the lowest similarity to strains of genotype TC07-like (70.4% to 70.5% for nucleotide and 53.8% to 56.2% for amino acid). The field pathogenic virus strains also have low nucleotide and amino acid similarity with the Massachusetts vaccine strain currently in use (86% for nucleotide and 77.1% for amino acid). Research results show the importance of molecular epidemiological surveillance and the selection of appropriate vaccine strains in Vietnam. This is the first report of sequencing the whole IBV genome in Vietnam.

Histopathological study and molecular characterization of Infectious Bronchitis virus circulating in broilers in Basrah governorate, Iraq

The poultry industry plays an important role in the food economics and the food industry in both their layer and broiler chicken. Poultry diseases on the other way impact in the poultry industry especially diseases from virus sources since it does not have a specific treatment except for vaccines with routine prevention and control. This study was designed for the assessment of histopathological changes, molecular diagnosis and phylogenetic analyses of the Infectious Bronchitis virus circulating in broilers in Basrah province in the south of Iraq. The tissue samples were (trachea, lung and kidney). One hundred samples were studied with clinical signs and lesions related to IB. The histopathological changes caused by the virus were studied with hematoxylin and eosin stain, and the causative agent Infectious Bronchitis Virus (IBV) was identified using a polymerase chain reaction combined with explaining the phylogenetic analysis. The results of molecular diagnosis and identification showed the twelve Iraqi field strains of IBV were closely related and shared a high identity of 98.44 %- 99.69 % of each other. Variant 2(IS/1494 like) was a predominant genotype of IBV in the present study, and has high similarity with the variant 2(IS/1494) like a strain of IBV circulating in Iran and in the Kurdistan region north of Iraq. The histopathological findings were desquamation of the cilia of the mucosa layer of the trachea, infiltration of inflammatory cells, hyperplasia of goblet cells with thickening of mucosal layer in some areas infiltration of inflammatory exudate within capillaries and Para bronchus, where the microscopic results in kidney were showed interstitial hemorrhage, necrosis of the renal tubular epithelium, infiltration of inflammatory cell. The present results provided useful information on target organs damaged by IBV and the genetic epidemiology of such virus strains circulating in Basrah governorate Iraq during this year that would be helpful to develop a local vaccine.

Infectious Bronchitis Virus (Gammacoronavirus) in Poultry: Genomic Architecture, Post-Translational Modifications, and Structural Motifs

Infectious bronchitis virus (IBV) is an avian coronavirus (CoV) that belongs to the genus Gammacoronavirus and has been listed as an important disease by the World Organization for Animal Health (WOAH). It causes highly contagious respiratory, reproductive, and renal diseases in commercial poultry farms. Multiple IBV serotypes and genotypes have been identified in many countries and many detected variants do not provide cross-protection against infection, resulting in repeated outbreaks and significant economic losses worldwide. In addition, the high genetic mutations and recombination events in the prominent genomic regions of IBV, particularly in the spike glycoprotein (S) and nucleocapsid (N) proteins, are directly involved in the evolutionary processes of IBV and lead to increased pathogenicity and tissue tropism. The characterization of the different genotypes and the relationship between the structure, function, post-translational modifications (PTMs), and structural motifs will elucidate the mechanisms that promote replication and pathogenicity and affect the host’s immune response during infection. In this review, we discuss the molecular features of various IBV genes and proteins that contribute to the infection process. We also highlight the common PTMs and structural motifs that occur during protein synthesis and are essential components of IBV ecology.

Antigenic Characterization of Infectious Bronchitis Virus in the South China during 2021-2022.

Avian infectious bronchitis is a serious and highly contagious disease that is caused by the infectious bronchitis virus (IBV). From January 2021 to June 2022, 1008 chicken tissue samples were collected from various regions of southern China, and 15 strains of the IBV were isolated. Phylogenetic analysis revealed that the strains mainly comprised the QX type, belonging to the same genotype as the currently prevalent LX4 type, and identified four recombination events in the S1 gene, among which lineages GI-13 and GI-19 were most frequently involved in recombination. Further study of seven selected isolates revealed that they caused respiratory symptoms, including coughing, sneezing, nasal discharge, and tracheal sounds, accompanied by depression. Inoculation of chicken embryos with the seven isolates resulted in symptoms such as curling, weakness, and bleeding. Immunization of specific pathogen-free (SPF) chickens with inactivated isolates produced high antibody levels that neutralized the corresponding strains; however, antibodies produced by vaccine strains were not effective in neutralizing the isolates. No unambiguous association was found between IBV genotypes and serotypes. In summary, a new trend in IBV prevalence has emerged in southern China, and currently available vaccines do not provide protection against the prevalent IBV strains in this region, facilitating the continued spread of IBV.

Pathological and molecular findings of visceral gout caused by Israel variant 2 (IS/1494/06) genotype of infectious bronchitis virus in chickens

The aim of this study was to investigate pathological lesions and the presence of of Israel variant 2 (IS /1494/06) genotype of infectious bronchitis virus (IBV) in chickens with visceral gout. Sudden deaths were observed in broiler breeders and layer hens belonging to two different flocks located in eastern Türkiye. Broiler chickens were previously vaccinated with a vaccine containing strains of IBV Massachusetts serotype, but no information was available about the vaccination history of laying hens. At necropsy, there was accumulation of white chalk-like material on the serosal surface of the heart, liver, spleen and air sacs. The kidneys were unilaterally or bilaterally enlarged and pale in color and, ureters were also enlarged. Pooled organ samples from diseased chickens and kidneys alone were examined by virus isolation, real-time reverse transcription polymerase chain reaction (rRT-PCR), nucleotide sequencing analysis and histological methods. Israel variant 2 genotype of IBV was detected in the samples of both flocks as a result of virus isolation, rRT-PCR and DNA sequencing analysis. Histological examination revealed multifocal and randomly distributed crystal deposits in the renal tubulus and adjacent interstitium. Mild to moderate crystalline deposits surrounded by heterophils and macrophages were detected in the serosal layers of the heart, spleen, liver, and air sacs. The findings of this study indicated that IBV should be taken into consideration in visceral gout cases of chickens, and detection of IBV genotypes in the field will enable us to use vaccines compatible with these genotypes in order to control the disease more efficiently.

Efficacy of commercial live vaccines against QX-like infectious bronchitis virus in Japan

Infectious bronchitis, an acute and highly contagious disease that affects chickens, is caused by the infectious bronchitis virus (IBV). The antigenic variant QX-like IBV was first reported in China in 1996 and is now endemic in many countries. Our previous study reported the first detection and isolation of QX-like IBVs in Japan and that they were genetically related to the recently detected strains in China and South Korea. The pathogenicity of 2 Japanese QX-like IBV strains (JP/ZK-B7/2020 and JP/ZK-B22/2020) was evaluated by inoculating specific pathogen-free (SPF) chickens with 102 to 106 median embryo infectious dose. Both strains caused clinical signs of respiratory symptoms, gross tracheal lesions, and moderate-to-severe suppression of tracheal ciliostasis. To evaluate the efficacy of commercial IBV live vaccines against the JP/ZK-B7/2020 strain, vaccinated SPF chickens were challenged with the JP/ZK-B7/2020 strain at 104 EID50 (median embryo infectious dose). Only the JP-Ⅲ vaccine provided high levels of protection (reduced suppression of tracheal ciliostasis and reduced viral loads in organs), whereas the Mass vaccine showed little protective effect. Virus neutralization test results and comparisons between IBV genotypes based on the S1 gene suggested that QX-like and JP-III genotypes were closely related. These results suggest that the JP-III IBV vaccine, which has relatively high S1 gene homology with QX-like IBVs, is effective against Japanese QX-like IBV strain.

Complete Genome Sequences of Infectious Bronchitis Virus Genotype JP-II (GI-7) and JP-III (GI-19) Strains Isolated in Japan.

We report the complete genome sequences of strains JP/Yamanashi/93 and JP/Shimane/98, which are classified in JP-II (GI-7) and JP-III (GI-19), respectively, the major genotypes of infectious bronchitis virus (IBV) in Japan. This information will be useful for the in-depth understanding of the evolution of IBV in Japan.