Infectious Bursal Disease Research Articles

Evaluation Of Infectious Bursal Disease Virus Maternally Derived Antibody Decay Rate In Day Old Broilers From Different Hatcheries In Nigeria

Infectious Bursal disease (IBD) is an immunosuppressive disease of young chicks, which is responsible for major economic losses in the poultry industry worldwide, particularly for the last decades. This study utilized a cross-sectional approach to evaluate Infectious bursal disease virus (IBDV) maternally derived antibody decay rate in day old chicks (D.O.C) obtained from different hatcheries in Nigeria. Of the 450 serum samples collected through random selection with replacement method, (i.e 90 samples from the 5 hatcheries designated as farms A – E), it was observed that farm A at day 1 had mean Elisa titre of (4213 ± 366.66), farm B (2178.225 ± 292.477), farm C (1629.699 ± 229.2197), farm D (3452.609 ± 403.64.6469) and farm E (1651.789 ± 201.6811), these values were far above the protective (positive) level of 875, recommended by IDvet manual with (S/P ratios of 0.350). This level was maintained, although, with minimal decays, up to day 7 for farms A, D and E but farm B and C did not exceed day 6 and day 5 respectively. Only farm D presented protective (positive) value that lasted to day 13. The best fit for this decay rate was calculated to be Y = -2263In(x) + 3714 (week) with R2 = (0.903). From these studies we could deduce that these farms were truly vaccinated or immunized as expected and they presented different antibody titres with variable decay rates. It would have been a good idea to recommend that same vaccination schedule should not be applied indiscriminately to broilers from these farms like other researchers have, but this would rather be to the detriment of many farmers who may not be privileged to access the detailed information on which schedule is meant for which farm .We therefor recommend that broilers from these hatcheries be vaccinated between day 7 to day 10 post hatch and a booster dose (if necessary) should be administered a week after, with an intermediate plus strain vaccine type that has the capacity to penetrate through the MDA and induce humoral-immunity-in- thechicks.

Loop PDE of viral capsid protein is involved in immune escape of the emerging novel variant infectious bursal disease virus

Infectious bursa disease (IBD) is an acute, highly contactable, lethal, immunosuppressive infectious disease caused by the Infectious bursa disease virus (IBDV). Currently, the emerged novel variant IBDV (nVarIBDV) and the sustainedly prevalent very virulent IBDV (vvIBDV) are the two most prevalent strains of IBDV in China. The antigenic properties of the two prevalent strains differed significantly, which led to the escape of nVarIBDV from the immune protection provided by the existing vvIBDV vaccine. However, the molecular basis of the nVarIBDV immune escape remains unclear. In this study, we demonstrated, for the first time, that residues 252, 254, and 256 in the PDE of VP2 are involved in the immune escape of the emerging nVarIBDV. Firstly, the IFA-mediated antigen-antibody affinity assay showed that PBC and PDE of VP2 could affect the affinity of vvIBDV antiserum to VP2, of which PDE was more significant. The key amino acids of PDE influencing the antigen-antibody affinity were also identified, with G254N being the most significant, followed by V252I and I256V. Then the mutated virus with point or combined mutations was rescued by reverse genetics. it was further demonstrated that mutations of V252I, G254N, and I256V in PDE could individually or collaboratively reduce antigen–antibody affinity and interfere with antiserum neutralization, with G254N being the most significant. This study revealed the reasons for the widespread prevalence of nVarIBDV in immunized chicken flocks and provided innovative ideas for designing novel vaccines that match the antigen of the epidemic strain.

Genetic Sequence and Pathogenicity of Infectious Bursal Disease Virus in Chickens in Egypt During 2017-2021.

The continued circulation of infectious bursal disease virus (IBDV) in Egypt, despite the use of various vaccines, is a serious problem that requires continuous detection of IBDV. In the current study, real-time reverse transcriptase polymerase chain reaction testing of 100 diseased chicken flocks during 2017-2021 revealed the presence of very virulent IBDV (vvIBDV) in 67% of the flocks, non-vvIBDV in 11%, and a mixture of both vvIBDV and non-vvIBDV in 4%. Twenty-nine IBDV isolates were submitted for partial sequencing of the viral protein 2 hypervariable region (VP2-HVR), and 27 isolates were confirmed to be genogroup A3 (vvIBDV) with 96.3%-98.5% similarity to the global A3 (vvIBDV) and 88.9%-97% similarity to genogroup A1 vaccine strains. The remaining two isolates were non-vvIBDV and showed 91.1% and 100% identity with classical genogroup A1 strains, respectively. Furthermore, the sequence and phylogenetic analysis of VP1 (amino acids 33-254) of two selected isolates of A3, 5/2017 and 98/2021, clustered them as B2, vvIBDV-like, strains with high similarity (99.5%) to four Egyptian, 99% to Chinese and European, and 97.7% to Chinese and Polish vvIBDV isolates. Experimental infection of commercial broiler chickens with two vvIBDV-A3B2 isolates (5/2017 and 98/2021) showed no mortality despite typical tissue lesions, clear histopathological changes, and strong ELISA antibody response. Isolate 98/2021 was more pathogenic, as confirmed by histopathology, whereas isolate 5/2017 induced a stronger serological response. In conclusion, vvIBDV (A3B2) strains with two amino acid (aa) substitutions in VP1 as V141I and V234I as well as VP2 as Y220F and G254S are still circulating in Egypt.

Oral delivery of Eimeria acervulina transfected sequentially with two copies of the VP2 gene induces immunity against infectious bursal disease virus in chickens.

Chicken coccidiosis caused by Eimeria spp. can occur on almost all poultry farms, causing huge economic losses to the industry. Genetically manipulated Eimeria parasites as a vaccine vector to deliver viral antigens have been reported. In our preliminary study, transgenic E. acervulina expressing a VP2 gene (Ea-VP2) of the infectious bursal disease virus (IBDV) demonstrated partial protection against IBDV infection. To enhance immune responses, we aimed to increase the VP2 gene copy number in transgenic E. acervulina. In this study, we used a novel plasmid vector carrying a VP2 gene fused with three flag tags and a red fluorescent reporter gene (mCherry). The vector was introduced into Ea-VP2 sporozoites through nucleofection, leading to the generation of Ea-2VP2. Subsequent analysis revealed a notable escalation in the fluorescent rate, increasing from 0.11 to 95.1% following four consecutive passages facilitated by fluorescent-activated cell sorting. Verification via PCR, Western blot, and immunofluorescence confirmed the successful construction of the Ea-2VP2 population. Despite lower fecundity compared to wild-type E. acervulina, Ea-2VP2 maintained immunogenicity. Our research effectively created a transgenic E. acervulina strain transfected sequentially with two copies of the VP2 gene from IBDV. This modification resulted in an increased humoral immune response after primary immunization in chickens. Additionally, it demonstrated a degree of protection within the bursa against IBDV infection. Future studies will focus on further enhancing immune response levels.

Development of an improved reverse genetics system for avian metapneumovirus (aMPV): A novel vaccine vector protects against aMPV and infectious bursal disease virus

Avian metapneumovirus (aMPV), a paramyxovirus, causes acute respiratory diseases in turkeys and swollen head syndrome in chickens. This study established a reverse genetics system for aMPV subtype B LN16-A strain based on T7 RNA polymerase. Full-length cDNA of the LN16-A strain was constructed by assembling five cDNA fragments between the T7 promoter and hepatitis delta virus ribozyme. Transfection of this plasmid, along with the supporting plasmids encoding the N, P, M2-1, and L proteins of LN16-A into BSR-T7/5 cells, resulted in the recovery of aMPV subtype B. To identify an effective insertion site, the enhanced green fluorescent protein (EGFP) gene was inserted into different sites of the LN16-A genome to generate recombinant LN16-As. The results showed that the expression levels of EGFP at the site between the G and L genes of LN16-A were significantly higher than those at the other two sites (between the leader and N genes or replacing the SH gene). To verify the availability of the site between G and L for foreign gene expression, the VP2 gene of very virulent infectious bursal disease virus (vvIBDV) was inserted into this site, and recombinant LN16-A (rLN16A-vvVP2) was successfully rescued. Single immunization of specific-pathogen-free chickens with rLN16A-vvVP2 induced high levels of neutralizing antibodies and provided 100% protection against the virulent aMPV subtype B and vvIBDV. Establishing a reverse genetics system here provides an important foundation for understanding aMPV pathogenesis and developing novel vector vaccines.

Impact of early feed restriction and continued supplementation with coated organic acid and essential oils on sustainability of laying performance, egg quality, fertility, hatchability, immunity status, and gut microbiota of Japanese quail hens

Abstract Three hundred and sixty, 42-day-old Japanese quail (JQ) hens were randomly divided into six experimental groups with 5 replicates/group. Each replicate consisted of 12 birds (8 females and 4 males). During the growing period, chickens were fed restricted (FR) during only the second week of age at days 7, 9, 11, and 13. Three levels of FR were applied: 0.0 (control), 12.5 (12.5FR), and 25.0% (25FR) of the ad libitum intake of chickens measured on the previous day (groups 1, 2 and 3). In the other three groups (4, 5 and 6) the control, 12.5FR and 25.0FR diets were supplemented with coated organic acid + essential oils (COAWEO ) at 100 g/ton feed. The trial lasted from 6 to 18 weeks of age. Feed intake was significantly reduced by 12.5% FR compared with the control group. FR improved all external and internal egg quality of JQ hens except for egg weight, while albumen % decreased in the group fed 12.5FR diet. Coated organic acid with essential oils did not affect all JQ hens’ external and internal egg quality. Feed restriction did not affect fertility, pipped and dead chicks, and hatchability, as total and fertile egg percentage. COAWEO increased fertility and hatchability percentage. FR did not affect blood serum biochemistry and immunity characteristics except for high density lipoprotein (HDL) and hemagglutination inhibition test for infectious bursal disease virus (HI IBDV). Coated organic acid with essential oils did not affect quail blood characteristics but significantly decreased total lipids and increased IL6 at 18 weeks of age. Dietary COAWEO decreased E. coli, Clostridia, and Salmonella while increasing Lactobacillus counts. It can be concluded that 25.0% FR supplemented with COAWEO considerably improved the sustainability of productive performance of JQ hens without adverse effects on egg production, quality, fertility and hatchability traits, serum biochemistry and immune markers, and gut microbiota.

Effect of adding natural and synthetic antioxidants to broiler drinking water as antistressor on productivity, antioxidant statues and hematological traits under heat stress

This study was conducted to explore the benefit of adding synthetic and natural antioxidants nutritional additives in drinking water to increase broiler resistance to heat stress in the hot summer climate on productive performance, and physiological status. A total of 600 chicks of broiler (Ross-308) were distributed into ten treatments, each treatment with three replicates of 20 chicks. The treatments of study are: T0: (Positive control: drinking water without adding-DW)- without heat stress, treatments exposed to heat stress: [T1: (Negative control: drinking water without adding-DW, but exposed to heat stress), T2: (100 mg BHT/1 L DW) (BHT – butylhydroxytoluene: synthetic antioxidant), T3: (100 mg vit E/1 L DW) (synthetic antioxidant), T4: (200 mg saffron/1 L DW) (natural antioxidant, T5: (200 mg curcumin/1 L DW), T6: (100 mg saffron+ 50 mg BHT/1 L DW), T7: (100 mg saffron+50 mg vit E/1 L DW), T8: (100 mg curcumin+ 50 mg BHT/1 L DW), T9: (100 mg curcumin+ 50 mg vit E/1 L DW)]. Data of the study analyses and display that the synthetic and natural antioxidants nutritional additives had significantly decreases in the temperature of body parts surface (head, back, under wings, cloaca), general body temperature, mortality%, Malondialdehyde (MDA), heat shock proteins (HSP-40 and HSP -70), Corticosterone hormone concentration in the blood serum and heterophiles: lymphocytes (H/L) ratio. However, body weight, body weight gain, Production index (PI), feasibility (economic profit), water intake (WI), Glutathione Peroxidase (GSH-Px), super oxide dismutase (SOD), total antioxidant capacity (TAC), Newcastle (ND), Infectious bursal (IBD) diseases and Infection bronchitis virus (IB), so feed conversion ratio (FCR) had significantly improved in the all treatments of water additive in the treatments of positive control T0 compared with the negative control T1. Whereas, feed intake had non-significant differences among all treatments of the study. In all traits of the study natural antioxidant additives: saffron and curcumin additives seen superiorly

The long noncoding RNA loc107053557 acts as a gga-miR-3530-5p sponge to suppress the replication of vvIBDV through regulating STAT1 expression

ABSTRACT Infectious bursal disease virus (IBDV) causes immunosuppression and high mortality in young chickens. Long non-coding RNAs (lncRNAs) and microRNAs (miRNAs) are important regulators during viral infection. However, detailed the regulatory mechanisms of lncRNA-miRNA-mRNA have not yet been described in IBDV infection. Here, we analysed the role of lncRNA53557/gga-miR-3530-5p/STAT1 axis in very virulent IBDV (vvIBDV) infection. Evidently upregulated expression of lncRNA53557 was observed in bursa of Fabricius and DT40 cells. Meanwhile, overexpression of lncRNA53557 promoted STAT1 expression and inhibited vvIBDV replication and vice versa, indicating that the upregulation of lncRNA53557 was part of the host antiviral defence. The subcellular fractionation assay confirmed that lncRNA53557 can be localized in the cytoplasm. Further, dual-luciferase reporter, RNA pulldown, FISH and RT-qPCR assays revealed that lncRNA53557 were directly bound to gga-miR-3530-5p and had a negative regulatory relationship between them. Subsequent mechanistic analysis showed that lncRNA53557 acted as a competing endogenous RNA (ceRNA) of gga-miR-3530-5p to relieve the repressive effect of gga-miR-3530-5p on its target STAT1, as well as Mx1, OASL, and ISG15, thereby suppressing vvIBDV replication. The study reveals that a network of enriched lncRNAs and lncRNA-associated ceRNA is involved in the regulation of IBDV infection, offering new insight into the mechanisms underlying IBDV-host interaction.

Identification of Extremely Virulent Infectious Bursal Disease Virus Via Molecular and Histological Methods in Broiler Chickens

Infectious bursal disease (IBD) is caused by an RNA virus belonging to the Avibirnavirus genus within the Birnaviridae family. The global prevalence of infectious bursal disease virus (IBDV) is a significant concern, affecting birds of all ages. Birds infected with IBDV exhibit symptoms, such as depression, bleeding in the thighs and pectoral muscles, and enlargement of the bursa. This study aimed to identify predominant IBDV serotypes using molecular methods and to gain insights into the resulting pathological conditions in infected chickens. Additionally, the study investigated the viral sequence and the relationship between a local Diyala isolate and reference strains from the Genebank. In the current study, the IBDV was isolated from broiler chickens aged 2-3 weeks from 15 farms in the Diyala Governorate of Iraq. A total of 15 samples, each from a different farm, were collected. Necropsy samples were obtained from various organs of broiler chickens, including the bursa of Fabricius, lungs, liver, and kidneys. Specific primers targeting the VP2 gene were used for reverse transcription-polymerase chain reaction (RT-PCR) analysis. The RT-PCR analysis yielded a 727 bp fragment, confirming the presence of IBDV in 10 out of the 15 samples. One strain was assigned the accession number LC498531 in the NCBI database. Phylogenetic analysis using the neighbor-joining tree program revealed three distinct groups. All examined regional samples (S1) were situated within the constructed tree. Five samples formed a specific group, indicating a close relationship. Histological examination of the tissues showed visible alterations such as degeneration, necrosis, and infiltration of inflammatory cells, particularly heterophils, providing clear evidence of the disease. In conclusion, this study confirmed the presence of IBDV in broiler chickens from multiple farms in Iraq’s Diyala Governorate, highlighting distinct clustering patterns in viral sequences. Moreover, the study confirmed the virus's presence using conventional RT-PCR, with histological examination supporting the findings. Keywords: Broiler chicken, Bursal enlargement, Infectious bursal disease, RT-PCR

Efficacy and Safety of an Inactivated Novel Variant Infectious Bursal Disease Virus in Broiler Chickens

The infectious bursal disease virus (IBDV) is severe and highly contagious, causing high mortality and immunosuppression in chickens worldwide. A new novel variant, IBDV (nVarIBDV), has recently emerged in Asian countries, including Malaysia, highlighting the need to develop a new vaccine against this strain due to the inadequacy of existing commercial vaccines in protecting chickens from nVarIBDV infection. Therefore, the current study aimed to evaluate the efficacy and safety of inactivated nVarIBDV as a potential vaccine candidate in broiler chickens. A total of 65 one-day-old Arbo Acres broiler chickens were randomly divided into three groups (five animals in each group with four replications) before the challenge, namely A, B, and C. Groups A and B were immunized subcutaneously at day old with inactivated nVarIBDV (107 EID50/0.2 ml), and Group B was boosted at day 14. Group C was an unimmunized control. The experimental animals were divided into three subgroups and were challenged with pathogenic nVarIBDV (105 EID50/1.0ml) on day 28 post-inoculation through ocular and oral routes. The challenge sub-groups were named ACH, BCH, and CCH, respectively. The live body weight, bursa weight, and blood samples of the chickens were recorded. Gross lesions were examined, and samples of the bursa of Fabricius were collected from all the groups for histological evaluation. All the chickens appeared healthy and normal throughout the trial. Body weight increased in all groups without significant differences. The bursa weight and the bursa-to-body weight ratio of the booster group (Group B) were significantly higher than the non-booster and control groups. Gross lesions were not observed in the investigated groups. The challenged control group had higher bursa lesion scoring than the vaccinated groups. The IBDV antibody titer of challenged chickens in ACH, BCH, and CCH groups was higher than those of unchallenged groups A, B, and C at 35 days post-inoculation. The IBDV antibody titer of challenged chickens in group B was higher than challenged chickens in groups A and C (ACH and CCH). In conclusion, the inactivated nVarIBDV demonstrated safety and efficacy, with the booster Group (B) showing elevated humoral immune responses compared to the non-booster group. Keywords: Antibody, Chicken, Efficacy, Inactivated vaccine, Novel variant infectious bursal disease virus

Evaluation of bird-adapted self-amplifying mRNA vaccine formulations in chickens

Each year, millions of poultry succumb to highly pathogenic avian influenza A virus (AIV) and infectious bursal disease virus (IBDV) infections. Conventional vaccines based on inactivated or live-attenuated viruses are useful tools for disease prevention and control, yet, they often fall short in terms of safety, efficacy, and development times. Therefore, versatile vaccine platforms are crucial to protect poultry from emerging viral pathogens. Self-amplifying (replicon) RNA vaccines offer a well-defined and scalable option for the protection of both animals and humans. The best-studied replicon platform, based on the Venezuelan equine encephalitis virus (VEEV; family Togaviridae) TC-83 vaccine strain, however, displays limited efficacy in poultry, warranting the exploration of alternative, avian-adapted, replicon platforms. In this study, we engineered two Tembusu virus (TMUV; family Flaviviridae) replicons encoding varying capsid gene lengths and compared these to the benchmark VEEV replicon in vitro. The TMUV replicon system exhibited a robust and prolonged transgene expression compared to the VEEV replicon system in both avian and mammalian cells. Moreover, the TMUV replicon induced a lesser cytopathic effect compared to the VEEV replicon RNA in vitro. DNA-launched versions of the TMUV and VEEV replicons (DREP) were also developed. The replicons successfully expressed the AIV haemagglutinin (HA) glycoproteins and the IBDV capsid protein (pVP2). To assess the immune responses elicited by the TMUV replicon system in chickens, a prime-boost vaccination trial was conducted using lipid nanoparticle (LNP)-formulated replicon RNA and DREP encoding the viral (glyco)proteins of AIV or IBDV. Both TMUV and VEEV replicon RNAs were unable to induce a humoral response against AIV. However, TMUV replicon RNA induced IBDV-specific seroconversion in vaccinated chickens, in contrast to VEEV replicon RNA, which showed no significant humoral response. In both AIV and IBDV immunization studies, VEEV DREP generated the highest (neutralizing) antibody responses, which underscores the potential for self-amplifying mRNA vaccine technology to combat emerging poultry diseases.

Efficacy of Saccharomyces cerevisiae Fermentation Product and Probiotic Supplementation on Growth Performance, Gut Microflora and Immunity of Broiler Chickens.

Concern for global health security and the environment due to the emergence of antibiotic-resistant bacteria and antibiotic residues in meat and other livestock products has led many countries to restrict the use of antibiotics in animal feed. This experiment was performed to assess the impact of dietary supplementation of a probiotic (Bacillus subtilis) and a postbiotic (Saccharomyces cerevisiae fermentation product) on growth performance, carcass traits, blood haemato-biochemical profile, gut microflora, gut morphology, and immune response in broilers as an alternative to antimicrobials in poultry production system to minimize the effect on global health security. A total of 324 one-day-old Ven Cobb 400 broiler chicks were randomly divided into three dietary groups, each containing 12 replicated pens, and each replicate contained nine chickens. The dietary groups consisted of (1) a basal diet without any growth promoters (T1), (2) the basal diet augmented with Bacillus subtilis at 200 g/MT feed (T2), and (3) the basal diet supplemented with Saccharomyces cerevisiae fermentation product at 1.25 kg/MT feed (T3). To calculate body weight gain, all birds and residual feed were weighed on a replicated basis on days 0, 7, 14, 21, 28, 35, and 42; mortality was recorded daily. At the end of the trial (42 d), two chickens from each replicate were slaughtered for carcass traits, gut microflora, and morphology measurements. Blood samples were collected for the haemato-biochemical profile on 35 d and antibody titer on 28 d and 35 d. Feeding with SCFP (T3 group) significantly improved average daily feed intake (ADFI) and average daily gain (ADG) of chickens compared to the T1 (control) and T2 (probiotic) groups from 1 to 14 days of age. Feed conversion ratio (FCR) was significantly improved in SCFP-fed birds (T3) relative to the control (T1) over the entire experimental period. Carcass traits and blood haemato-biochemical parameters remained unaffected by any diets. However, cholesterol levels and concentrations of corticosterone were significantly lower in T3 compared to T2 and T1 groups. Total E. coli, Enterohaemorrhagic E. coli, ESBL-producing Enterobacteriaceae, and Salmonella counts were significantly lower in T2 and T3 groups compared to T1 group and Salmonella counts were lower in T3 when compared to T2. However, there was no significant difference in Lactobacillus count among treatment groups. A significant increase in villi height and villi-height-to-crypt-depth ratio (VH: CD) was observed in both T3 and T2 groups. On day 28, the T3 and T2 groups exhibited a significant increase in antibody titers against Newcastle disease virus and infectious bursal disease virus. It can be concluded that Saccharomyces cerevisiae fermentation product and Bacillus subtilis probiotic could be viable alternatives to antimicrobials in poultry production considering beneficial impacts in broilers fed an antibiotic-free diet.

Feeding strategy and prebiotic supplementation: Effects on immune responses and gut health in the early life stage of broiler chickens

This study aimed to investigate the effects of early or late feeding strategies and prebiotic, on immune responses and gut health during the early life stage of broiler chickens. A total of 240 day-old male broiler chicks were used in a 2 × 3 factorial arrangement of treatments that comprised 2 feeding strategies (early or late) and 3 levels of prebiotic (0, recommended dosage or three times the recommended dosage) in a completely randomized design with 4 pen replicates and 10 broilers per each. Compared to broiler chickens that had early access to feed, delayed access to feed resulted in an increased population of Escherichia coli and a decreased population of Lactobacillus spp. and Bifidobacterium spp. in the ileum (P < 0.05). Additionally, delayed access to feed led to a decrease in villus height, crypt depth, villus height: villus width ratio, goblet cell density, and mucin 2 gene expression in the ileum (P < 0.05). The supplementation of prebiotics in both the late and early feeding strategy groups resulted in increased villus height, crypt depth, goblet cell density, mucin 2 gene expression, and antibodies against Infectious Bursal Disease (IBD). Additionally, it led to an improvement in the foot web thickness index (P < 0.05). Furthermore, it resulted in a significant decrease in the population of Escherichia coli, while the populations of Lactobacillus spp. and Bifidobacterium spp. in the ileum were significantly increased (P < 0.05). Therefore, this study suggests that incorporating prebiotics in the starter diet can effectively enhance immune responses and promote gut health, regardless of the feeding strategy (early or late). In conclusion, this study demonstrates the potential benefits of incorporating prebiotics into poultry diets to alleviate the detrimental effects of delayed access to feed and improve gut health during the early life stage of broiler chickens.

Novel variant infectious bursal disease virus diminishes FAdV-4 vaccination and enhances pathogenicity of FAdV-4

Infectious bursal disease virus (IBDV) caused an acute and highly contagious infectious disease characterized by severe immunosuppression, causing considerable economic losses to the poultry industry globally. Although this disease was well-controlled under the widely use of commercial vaccines in the past decades, the novel variant IBDV strains emerged recently because of the highly immunized-selection pressure in the field, posting new threats to poultry industry. Here, we reported novel variant IBDV is responsible for a disease outbreak, and assessed the epidemic and pathogenicity of IBDV in this study. Moreover, we constructed a challenge model using Fowl adenovirus serotype 4 (FAdV-4) to study on the immunosuppressive effect. Our findings underscore the importance of IBDV surveillance, and provide evidence for understanding the pathogenicity of IBDV.

Research Note: Characterization and phylodynamic analysis of new infectious bursal disease virus variants circulating in Argentina

Infectious Bursal Disease is a highly contagious disease that affects young chickens and leads to significant economic losses. Its causal agent is a double-stranded RNA virus that, due to its high error rate during the replication process, gives rise to a constant generation of new virus variants. Until 2014, strains of Infectious Bursal Diseases Virus (IBDV) belonging to genogroup 4 predominated in Argentina, but there have been no reports since then regarding the circulating genogroups in poultry. In this study, 11 recent sequences of Argentine from the hypervariable region of VP2 protein (hvVP2) were analyzed to determine their genogroup, origin, evolution, and amino acid sequence. Samples from chickens showing signs of IBDV infection were collected, and the hvVP2 region was amplified using RT-PCR, followed by sequencing. The results indicated that the analyzed strains belong to genogroup 2, with an estimated evolutionary rate of 1.74 × 10-3 substitutions/site/year. It is speculated that the predominant group of sequences began to spread in Argentina around 2014 and had its origins in China. Another sample is related to strains from South Korea and is not closely linked to the main group. Furthermore, the predicted amino acid sequences show similarity to strains that can evade vaccine-induced immunity. These findings underscore the importance of active surveillance in poultry to mitigate losses caused by IBDV.

A Quick Review of the Prevalence of Important Infectious Poultry Diseases all Around the World.

The poultry industry is one of the fastest growing industries in the world. Poultry breeding has developed significantly to meet the food needs of the increasing population and it is expected that this growth will continue in the coming years. Prevalent poultry diseases are of great importance as they are responsible for vast economic losses and public health concerns. They also affect the national and international trade of the poultry products. This review will provide a quick and general view of different important poultry diseases for poultry breeders, scientists and decision makers. Based on this review, Campylobacteriosis and infectious bursal disease [IBD] in the Asian continent, and Campylobacteriosis, Newcastle disease [ND] and coccidiosis in the African continent were the most prevalent diseases. In Europe, Campylobacter species and in America, Escherichia coli species are widespread in poultry meat. Infectious Bronchitis [IB] in Europe and Coccidiosis in America were high-incident.

Development of a Highly Efficient CRISPR/Cas9-Mediated Herpesvirus of Turkey-Based Vaccine against Novel Variant Infectious Bursal Disease Virus.

Infectious bursal disease (IBD), caused by IBD virus (IBDV), is an extremely contagious immunosuppressive disease that causes major losses for the poultry industry worldwide. Recently, the novel variant IBDV (G2d) has been highly prevalent in Korea, but the current vaccines against this very virulent IBDV have limited efficacy against this novel variant. To develop a vaccine against this variant IBDV, a recombinant virus designated rHVT-VP2 was constructed by inserting the IBDV (G2d) VP2 gene into herpesvirus of turkeys (HVT) using CRISPR/Cas9 gene-editing technology. The PCR and sequencing results obtained showed that the recombinant virus rHVT-VP2 was successfully constructed. Vaccination with rHVT-VP2 generated IBDV-specific antibodies in specific pathogen-free chickens starting from 2 weeks post-immunization. Seven days after the challenge, the autopsy results showed that the bursa atrophy rates of the rHVT-VP2, HVT, vaccine A, and positive control groups were 0%, 100%, 60%, and 100%, respectively, and the BBIX values were 1.07 ± 0.22, 0.27 ± 0.05, 0.64 ± 0.33, and 0.32 ± 0.06, respectively. These results indicate that rHVT-VP2 can provide 100% protection against a challenge with the IBDV (G2d), whereas vaccine A only provides partial protection. In conclusion, vaccination with the recombinant virus rHVT-VP2 can provide chickens with effective protection against variant IBDV (G2d).

The effect of ghrelin on bursa and cecal tonsils of chickens infected with an attenuated virus strain of infectious bursal disease virus

Infectious bursal disease (IBD) significantly affects the poultry industry, causing substantial economic losses. This study aimed to investigate the effects of ghrelin on chicks infected with an attenuated virus strain of IBDV (aIBDV). Chicks were divided into 3 groups: a control group (group I), an aIBDV infection group (group II), and a ghrelin + aIBDV infection group (group III). Mice in groups II and III were fed until they reached 19 d of age and then inoculated with aIBDV to establish a subclinical infection model. Group III received an intraperitoneal injection of 0.5 nmol/100 g ghrelin from d 17 to 23. The present study utilized paraffin sectioning, H&E staining, and immunohistochemical staining to examine the effects of ghrelin on the bursa of fabricius and cecum tonsils in aIBDV-infected chicks. The results indicated that at 3 d postinfection (dpi), the average body weight of group III was significantly greater than that of group II (P < 0.05). At 3 and 7 dpi, the proportion of large lymphoid follicles in the bursa of fabricius in group III was notably greater than that in group II (P < 0.05). aIBDV infection resulted in bleeding, edema, and fibrosis in the cecal mucosal layer of chicks, but ghrelin administration mitigated these pathological changes. At 3 and 7 dpi, the thickness of the lamina propria in the cecal tonsils of group III was significantly lower than that in the cecal tonsils of group II (P < 0.05). Additionally, the percentage of large lymphoid follicles in the cecal tonsils of group III was significantly greater than that in group II at 3 and 5 dpi (P < 0.05). There were significantly fewer macrophages in the cecal tonsils of group III than in those of group II at 1, 3, and 5 dpi (P < 0.05). In conclusion, ghrelin supplementation improved performance and mitigated bursal atrophy in aIBDV-infected chicks. It also reduced histological lesions and immune responses in the cecum tonsil. Notably, the reduction in macrophages in the cecum tonsil following ghrelin administration may decrease the risk of aIBDV spread.

The booster immunization using commercial vaccines effectively protect chickens against novel variants of infectious bursal disease virus (genotype A2dB1)

The novel variant IBDV (nVarIBDV, genotype A2dB1), characterized by bursal atrophy of fabricius and decreased lymphocytes, has been emerging on a large scale in Asia (including China) since late 2018. nVarIBDV is a new threat to the poultry industry, yet the currently licensed commercial vaccines, including the live viral vector vaccine, IBDV immune complex vaccine or VP2 subunit vaccine, are ineffective against nVarIBDV infection. In this study, specific-pathogen-free (SPF) chickens and broilers divided into three groups were vaccinated with the live viral vector vaccine, the VP2 subunit vaccine or the IBDV immune complex vaccine at 1 day old, respectively. The SPF chickens received a secondary vaccination with the live B87 strain vaccine at 11 days-old. The bursa/body weight ratio, histopathology lesion of the bursa, and the differentiation between infected and vaccinated animals (DIVA) by qRT-PCR confirmed that the live viral vector vaccine or immune complex vaccine plus live B87 strain booster could provide at least 80% protection against the FJ2019-01 strain of nVarIBDV in SPF chickens. The broilers also received a secondary vaccination using a live W2512 G-61 strain vaccine at 14 days-old, and analyses showed that the VP2 subunit vaccine or immune complex vaccine plus the live W2512 G-61 strain booster also provided more than 80% protection against the FJ2019-01 strain of nVarIBDV. Unfortunately, the live viral vector vaccine plus live W2512 G-61 strain booster provided poor to moderate protection against FJ2019-01 in broilers. These findings suggest that combining commercial vaccines with rational booster immunization can effectively protect chickens against an nVarIBDV challenge.

Isolation, Molecular, and Histopathological Patterns of a Novel Variant of Infectious Bursal Disease Virus in Chicken Flocks in Egypt.

After an extended period of detecting classical virulent, attenuated, and very virulent IBDV, a novel variant (nVarIBDV) was confirmed in Egypt in this study in 18, IBD vaccinated, chicken flocks aged 19-49 days. Partial sequence of viral protein 2 (VP2) [219 aa, 147-366, resembling 657 bp] of two obtained isolates (nos. 3 and 4) revealed nVarIBDV (genotype A2d) and OR682618 and OR682619 GenBank accession numbers were obtained. Phylogenetic analysis revealed that both nVarIBDV isolates were closely related to nVarIBDV strains (A2d) circulating in China, exhibiting 100% identity to SD-2020 and 99.5-98.1% similarity to ZD-2018-1, QZ, GX and SG19 strains, respectively. Similarity to USA variant strains, belonging to genotypes A2b (9109), A2c (GLS) and A2a (variant E), respectively, was 95.5-92.6%. Also, the VP2 hypervariable region in those two, A2d, isolates revealed greater similarities to Faragher 52/70 (Vaxxitek®) at 90.4% and to an Indian strain (Ventri-Plus®) and V217 (Xtreme®) at 89.7% and 86-88.9% in other vaccines. Histopathological examination of both the bursa of Fabricius and spleen collected from diseased chickens in flock no. 18 revealed severe atrophy. In conclusion, further studies are required to investigate the epidemiological situation of this novel genotype across the country, and to assess various vaccine protections against nVarIBDV. Additionally, vaccination of breeders with inactivated IBD vaccines including this nVarIBDV is essential to obtain specific maternal antibodies in their broilers.