Search Results (94)

Over the past decade, diseases associated with fowl adenoviruses (FAdVs) have exhibited a new epidemic trend worldwide. The presence of numerous FAdVs serotypes, combined with the virus’s broad host range, positions it as a significant pathogen in the poultry industry. In the current context of intensive poultry production and global trade, co-infections involving multiple FAdVs serotypes, as well as co-infections with FAdVs alongside infectious bursal disease or infectious anemia virus, may occur within the same region or even on the same farm. The frequency of these outbreaks complicates the prevention and control of FAdVs. Therefore, the development of effective, targeted vaccines is essential for providing technical support in the management of FAdVs epidemics. Ongoing vaccine research aims to improve vaccine efficacy and address the challenges posed by emerging FAdVs outbreaks. This review focuses on vaccines developed and studied worldwide for various serotypes of FAdVs in the past decade. It encompasses inactivated vaccines, live attenuated vaccines, e.g., host-adapted attenuated vaccines and gene deletion vaccines, viral vector vaccines, and subunit vaccines (including VLP proteins and chimeric proteins). The current limitations and future development directions of FAdVs vaccine development are also proposed to provide a reference for new-generation vaccines and innovative vaccination strategies against FAdVs, as well as for the rapid development of highly effective vaccines. Full article

Infectious bursal disease virus (IBDV) is one of the most important immunosuppressive viruses in poultry, causing the global spread of infectious bursal disease (IBD). It poses a significant threat to the healthy development of the poultry industry. Vaccination is an effective approach for controlling IBDV infection. Therefore, reliable immune monitoring for IBDV is critical for maintaining poultry health. The enzyme-linked immunosorbent assay (ELISA) is a common technique used to detect specific antibodies in clinical serum testing and for the serological evaluation of IBDV vaccines. Among the currently available and under development IBDV vaccines, IBD VP2 subunit-based vaccines account for a considerable proportion. These vaccines stimulate the production of antibodies that are specific only to VP2. However, most IBDV antibody ELISA kits approved for use have applied the whole virus as the coating antigen, which does not adequately meet the diverse requirements for IBDV detection across different conditions. This study utilized a prokaryotic expression system to express the VP2 protein of the IBDV epidemic strain, assembling it into virus-like particles to be used as coating antigens. This approach enabled the establishment of an indirect ELISA method for detecting IBDV VP2 antibody (VP2-ELISA). The optimal coated antigen concentration was determined to be 2.5 μg/mL, with overnight coating at 4 °C; sealing with 5% skim milk at 37 °C for 4 h; serum dilution at 1:500 with incubation at 37 °C for 30 min; secondary antibody dilution at 1:4000 with incubation at 37 °C for 40 min; and then incubation with the substrate solution 3,3′,5,5′-tetramethylbenzidine at room temperature for 20 min. The criterion for interpreting the detection results was OD_450nm ≥ 0.111 indicates IBDV antibody positivity, while OD_450nm < 0.111 indicates negativity. The established VP2-ELISA can specifically detect IBDV-positive sera at the lowest serum dilution of 1:6400, with intra- and inter-batch coefficients of variation of <2%. This indicates that the VP2-ELISA exhibits good specificity, sensitivity, and stability. Detection experiments using 20 laboratory-immunized chicken serum samples and 273 clinical serum samples demonstrated that the results of VP2-ELISA were consistent with those of commercial ELISA kits coated with whole virus. In summary, the VP2-ELISA developed in this study offers advantages in immune response detection for IBD VP2 subunit-based vaccines and is appropriate for evaluating the efficacy of IBD vaccines and detecting clinical serum samples. Full article

Infectious bursal disease (IBD) is a viral disease that most commonly affects young chickens and destroys lymphocytes, leading to immunosuppression. The field study aimed to investigate the effect of three different vaccines administered in ovo against IBD and spray against Newcastle disease (ND) on serological response tested for IBD and ND and histopathological analysis of the bursa of Fabricius (BF) and quantitative B lymphocytes in BF in broiler chickens. The study was conducted on a farm of four hen houses with 30,000 chicks in each building. Three different vaccination programs were used in the poultry hatchery, and one hen house IV was not vaccinated. All three groups were vaccinated at 18 days and 9 h in ovo during egg transfer against IBD at a dose of 0.05 mL/embryo, group I vector vaccine (strain vHVT013-69), group II immunocomplex vaccine (strain Winterfield 2512), group III immunocomplex vaccine (strain M.B, 0.05). Then, after hatching, the chicks were vaccinated in a spray (groups I, II, and III) against NDV (strain VG/GA, 20 mL/100 birds) and infectious bronchitis (IBV) in a spray (strain H-120, serotype Mass, and strain CR88121, serotype 793B) at a dose of 20 mL/100 chicks. On days 1, 21, 31, and 41, blood was collected for serological tests to determine the antibody titer against IBD, which was performed using two tests (IDEXX and ID-Vet) and against ND. During the necropsy of birds on days 21 and 31, the bursae of Fabricius were collected from five chickens for histopathological evaluation of BF and quantitative B lymphocyte counts; a total of 40 bursae were analyzed (10 per group). The vaccination program applied significantly (p < 0.05) affected the immune response expressed as a geometric mean titer (GMT) in the serum of the examined chickens against IBDV on days 21, 31, and 41. Differences were also demonstrated in the mass and level of BF damage and the number of B lymphocytes. No significant differences were demonstrated in the GMT in the serum of the examined chickens against NDV depending on the vaccination program applied. Full article

The poultry farming industry encounters considerable obstacles stemming from viral diseases, resulting in elevated mortality rates and substantial economic losses. Current research highlights the significant involvement of long non-coding RNAs (lncRNAs) in the interactions between hosts and pathogens by enhancing antiviral responses at different levels, such as the activation of pathogen recognition receptors, as well as through epigenetic, transcriptional, and post-transcriptional modifications. Specific long non-coding RNAs (lncRNAs), including ERL lncRNA, linc-GALMD3, and loc107051710, have been recognized as significant contributors to the antiviral immune response to multiple avian viral pathogens. Understanding the mechanisms by which long non-coding RNAs (lncRNAs) act offers valuable insights into prospective diagnostic and therapeutic approaches aimed at improving disease resistance in poultry. Differentially expressed lncRNAs may also be utilized as biomarkers for both prognosis and diagnosis of avian viral diseases. This review delves into the various roles of long non-coding RNAs (lncRNAs) in the context of viral diseases in chickens, such as avian leukosis, Marek’s disease, infectious bursal disease, avian influenza, infectious bronchitis, and Newcastle disease. It highlights the pivotal role of lncRNAs in the complex dynamics between the host and viral pathogens, particularly their interactions with specific viral proteins. Understanding these interactions may provide valuable insights into the spatial and temporal regulation of lncRNAs, aid in the identification of potential drug targets, and reveal the expression patterns of lncRNA and coding gene transcripts in response to different viral infections in avian species. Full article

Mycotoxins are secondary fungal metabolites that frequently contaminate poultry feed, posing significant risks to animal health, productivity, and food safety. In broiler production, mycotoxins such as aflatoxins, trichothecenes, fumonisins, ochratoxin A, deoxynivalenol, and zearalenone have been shown to impair growth performance, damage key organs, and disrupt immune function. This review explores the multifaceted impact of mycotoxin exposure in broilers, with particular emphasis on immunosuppression, decreased vaccine efficacy, and increased vulnerability to infectious diseases, including coccidiosis, salmonellosis, E. coli, and viral infections like infectious bursal disease and infectious laryngotracheitis. Mycotoxin contamination in poultry feed can lead to direct economic losses through reduced feed conversion efficiency, increased mortality, and reproductive disorders, while also resulting in the transfer of toxic residues into meat and eggs, thereby threatening consumer health. The review further examines the synergistic interactions between mycotoxins and pathogens, the physiological and histopathological changes in exposed birds, and the implications for public health. Finally, it discusses current mitigation strategies, including mycotoxin binders, probiotics, and regulatory approaches to reduce exposure. An integrated management strategy combining feed hygiene, monitoring, and targeted nutritional interventions is essential to safeguard poultry health, enhance vaccine responses, and ensure the safety of poultry-derived food products. This review offers actionable insights for veterinarians, nutritionists, and policymakers, reinforcing the importance of mycotoxin mitigation strategies within a One Health framework. Full article

The etiology of transmissible viral proventriculitis (TVP) of broiler chickens has been discussed since its initial recognition 40 years ago. Regardless of its low direct impact on mortality rate, it leads to high economic losses in the broiler industry through reduction of food conversion, weakening of birds, and their increased susceptibility to pathogens. The aim of the present study was to examine the potential presence of TVP on the broiler chicken farms in Bosnia and Herzegovina, to characterize microscopic lesions, and to investigate the viruses implicated in etiology of TVP by PCR-based methods. In total, 143 diseased broiler chickens from 16 farms in Bosnia and Herzegovina were euthanized and subjected to necropsy and subsequent histopathology of proventriculi. A representative number of proventriculi samples (n = 50) that exhibited histopathologic changes were processed for molecular detection of chicken proventricular necrosis virus (CPNV), girovirus (GyV3), chicken anemia virus (CAV), and infectious bursal disease virus (IBDV) by PCR-based methods. In addition, samples of bursa of Fabricius (n = 39) and spleen (n = 50) were tested for IBDV. Histopathology revealed changes consistent with TVP in 39.8% (57/143) and LP (lymphocytic proventriculitis) in 2.1% (3/143) of samples. All 50 proventricular samples showed positivity to CPNV with Ct values ranging between 18 and 26. GyV3 was detected in eight samples (16%), with Ct values ranging from 11.1 to 27.5. The presence of CAV was more prominent (38%), with 19 positive broiler chickens (Ct ranging from 9.6 to 35.6). Pooled samples of spleen, bursa, and proventriculi from three farms were positive for IBDV. The obtained results represent the first documented data on TVP and the first record of CPNV and GyV3 presence in broiler farms from Bosnia and Herzegovina. Full article

The poultry industry is a critical source of affordable protein worldwide; however, it faces continuous threats from various poultry diseases that significantly impact public health, economic stability, and food security. Knowledge of and examination of the transmission routes, risk factors, and environmental survival characteristics of the most important pathogens affecting poultry populations, as well as the importance of strict biosecurity, are pivotal. Transmission routes are split into direct and vector-borne pathways, and indirect ways, which include infections via contaminated surfaces and vector-borne pathways, including insects and rodents. Avian influenza virus and Newcastle disease virus spread through respiratory droplets, and their transmission risk increases with increasing stocking density. While other pathogens (e.g., infectious bursal disease virus and Salmonella spp.), to persist long-term in the environments, for example, feed and litter, increasing the probability to persist long-term in the environments, for example, feed and litter, increasing the probability of infection. The long-term resilience of pathogens in multiple pathogens in various environmental conditions highlights the role of biosecurity, sanitation, and hygiene controls in preventing disease outbreaks. High stocking density in production systems, suboptimal ventilation, and inadequate biosecurity controls further increase transmission risks. This paper summarizes important disease transmissions and reinforces the need for strict biosecurity protocols and routine health monitoring to prevent the spread of pathogens within and beyond poultry facilities. These strategies can support safe poultry production, address growing global demand, and ensure food safety and public health. Full article

Infectious bursal disease (IBD) is a major immunosuppressive disease affecting young chickens, and causes significant economic losses to the poultry industry. This work represents the first pathogenicity assessment of Moroccan very virulent IBD virus. Molecular characterization and sequence analysis of this isolate previously identified specific substitutions, including seven amino acid substitutions in segment A, and I472L and E688D in segment B, specific and unique to Moroccan vvIBDV strains. Two chicken lines, broiler and specific-pathogen-free (SPF) chickens, were inoculated via the occulonasal route with 0.2 mL of the 10⁵EID₅₀ /mL viral solution of the IB19 vvIBDV strain at 29 days of age. Experimental monitoring was carried out for 10 days post-challenge (dpc). Clinical signs started on the second dpc, with peak severity observed between 3 and 6 dpc. The total mortality rate reached 10% in broilers (group G1) and 93% in SPF chickens (G3). Macroscopic lesions in G1 broilers included marked hypertrophy of the bursa of Fabricius (BF), followed by very pronounced atrophy, while macroscopic examinations of deceased SPF birds (G3) revealed very hemorrhagic BF with a black cherry appearance in 80% of dead birds. The mean Bursa/Body Index (BBI) of challenged broilers (G1) showed a decrease of 46% compared to the control group (G2), indicating bursal atrophy. Microscopic lesions in the BF consisted mainly of inflammation, with severe lymphoid depletion of the follicles in challenged G3 SPF birds. This in vivo study of Moroccan vvIBDV demonstrated a distinctive virulence profile, and confirmed its classification as a very virulent strain with substantial disease-causing potential. It is crucial to obtain comprehensive knowledge of the prevalence, emergence, pathogenicity, and control of Moroccan IBDV strains. Full article

Infectious bursal disease virus (IBDV) is an important pathogen affecting the poultry industry worldwide. IBDV serotype 1, including classical virulent strains (cvIBDV), variant strains (varIBDV), and very virulent strains (vvIBDV), is pathogenic for chickens. IBDV mainly infects immature B-lymphocytes in the bursa of Fabricius, weakening the humoral immune response and leading to secondary infections and increased morbidity and mortality. The Laboratory of Avian Pathology received ten live 8-week-old pullets from a laying hen operation experiencing increased mortality, prostration, diarrhea, and sudden death. Upon necropsy, the affected birds presented swollen, hemorrhagic, and edematous bursa of Fabricius, as well as hemorrhage in the breast and thigh muscles. RT-PCR confirmed that the samples from the bursa of Fabricius were positive for IBDV. Phylogenetic analysis of the VP1 and VP2 gene nucleotide sequences classified the strain, isolated in embryonated chicken eggs, as the A3B5 genotype. Amino acid sequence analysis of the VP2 hypervariable region revealed the presence of amino acid residues commonly found in vvIBDV. Additional studies are required to investigate the epidemiological situation of this genotype in Chile and to evaluate current vaccination plans and their effectiveness against new variants. Full article

Mycoplasma, reticuloendotheliosis virus (REV), avian leukosis virus (ALV), chicken infectious anemia virus (CIAV), bovine polyomavirus (BPV), bovine viral diarrhea virus (BVDV), and porcine circovirus (PCV) are considered common contaminants in live veterinary vaccines against Newcastle disease virus (NDV), fowlpox virus (FPV), infectious bursal disease virus (IBDV), classical swine fever virus (CSFV), pseudorabies virus (PRV), and porcine reproductive and respiratory syndrome virus (PRRSV). In the past five years, Getah virus (GETV), an arbovirus affecting many farming mammals, was reported as a new contaminant in live PRRSV vaccines in two previous studies, which arouses our considerable interest. Therefore, in this paper, we aim to analyze and discuss the source, biological hazard, and genomic characteristics of these contaminating GETV strains further. Full article

Poultry production systems are usually exposed to important infections that could be prevented by vaccination programs. Conventional methods of vaccination such as drinking water; spray, eye, or nose inoculation; and injection are usually given after hatching and have many disadvantages. Therefore, there is a great need for searching of alternative ways for vaccination process. In ovo vaccination technology is now regarded as an alternative approach to post-hatch vaccination in modern poultry operations. This technique is effective, fast, provides uniform vaccine dosing and delivery, is suitable for massive production, and reduces labor costs. Routine in ovo vaccination is applied during the late stage of embryonic development between days 17.5 and 19.25 of egg incubation. The best route of inoculation of the vaccine is in the amniotic fluid or in the embryo’s muscles, without causing any hatchability or chick quality losses. Accordingly, the inoculation site, the age of the embryos and breeders, presence of maternal antibodies, and the sanitation of equipment’s and the environment during the vaccination process affect the efficiency of the in ovo vaccination technique. In ovo vaccination technology is currently applied for vaccination against several economically important viral diseases such as Newcastle, infectious bursal disease, Marek’s disease, infectious laryngotracheitis, infectious bronchitis, avian influenza, and avian metapneumovirus. Moreover, vaccines used for prevention of mycoplasmosis and coccidiosis could be applied in ovo instead of in post-hatching application. It can be concluded that in ovo vaccination is a rapidly growing trend of vaccine technology, and it can replace post-hatching vaccination conventional methods. Full article

Novel antigenic variant strains of the infectious bursal disease virus (IBDV) classified into genogroup A2d have been found in the western part of Japan since 2017. Novel antigenic variant IBDVs now occur in higher frequencies in poultry houses and have been detected in the eastern part of Japan, indicating the spread of IBDVs despite the usual IBDV vaccination. We isolated a novel antigenic variant IBDV, designated as the B2977CE2C3 strain. The B2977CE2C3 strain had two genogroup A2d specific amino acids—lysine and isoleucine, at 221 and 252 aa—along with the other genogroup A2 common amino acids in the projection domains of the VP2 protein corresponding to the virus-neutralizing epitopes and viral pathogenicity. Experimental infection of the B2977CE2C3 strain did not produce any apparent clinical signs in the specific-pathogen-free chickens during the observation period (21 days), but atrophy of the bursa of Fabricius (BF) was apparent. The mean BF to the body weight ratio was 0.35 in negative control chickens at 21 days post-infection (pi) but 0.06 in the B2977CE2C3 infected group. An extremely high copy number of the IBDV genome (>10⁸ copies/µL) was observed in the BF at 3 days pi, while a high copy number of the IBDV genome (>10⁶ copies/µL) was observed in the thymus, spleen cecal tonsil, and bone marrow even though macroscopic lesions were not apparent in these organs. Full article

Despite the significant growth in Sonali chicken production across Bangladesh, inadequate disease surveillance and control measures along with indiscriminate antimicrobial use remain major challenges to the sector. In this study, we evaluated the disease burden and antimicrobial prescription patterns of Sonali chickens in Bangladesh using a web-based data recording system from 2020 to 2021 and analyzed 1690 cases. The diagnoses recorded in the system were presumptive, as they were based on clinico-epidemiological history, clinical signs, and gross necropsy findings noted by registered veterinarians. We conducted this study in Bogura, a district renowned for its high concentration of Sonali chicken farms. We estimated a higher prevalence of infection among grower chickens (69.0%) compared to starter chickens (31.0%). Small- to medium-sized flocks (63%) were more frequently infected than larger flocks (37.0%). Most disease cases occurred during the summer season (43.0%), followed by winter (27%), the rainy season (15%), and autumn (14%). Overall, climatic factors contributed to 51% of disease occurrence at temperatures below 25°C, 55% at high humidity (≥75%), and 57% during heavy rainfall (≥29 mm). The most prevalent disease was Newcastle disease (ND) (19.5%), followed by Marek’s disease (9.8%), coccidiosis (7.4%), necrotic enteritis (4.7%), infectious bursal disease (3.2%), and infectious laryngotracheitis (3.2%). The odds of ND were 1.4 (grower chickens vs. starter chickens), 11.4 (summer vs. winter), 4.1 (autumn vs. winter), 3.9 (rainy vs. winter), 3.5 (≥25 °C vs. <25 °C), and 2.6 (≥75% vs. <75%). Tylvalosin (38.0%) was the most frequently prescribed antibiotic, followed by fluoroquinolones (9.0%), aminoglycosides (8.0%), and colistin sulphate (4.0%). These findings suggest that a web-based disease record could be an important tool for a centralized poultry disease surveillance system in low- and middle-income countries like Bangladesh. Full article

Infectious bursal disease (IBD) continues to threaten poultry production globally, with highly virulent strains circulating in many parts of Africa. In this study, molecular characterization was performed on a circulating infectious bursal disease virus (IBDV) strain from an outbreak in a layer flock in Ghana. Layer chicks presented for necropsy had markedly enlarged and hemorrhagic bursae of Fabricius, with necrotic foci and catarrhal exudate on the serosal surface. Histopathology of the bursa of Fabricius revealed scattered to effacing hemorrhages on the plicae, extensive necrosis with expansion of the stroma between the follicles, and depletion of lymphocytes within the interfollicular epithelium. Reverse transcription polymerase chain reaction (RT-PCR) and subsequent sequencing of the VP2 gene showed the presence of IBDV in formalin-fixed paraffin-embedded tissues. A phylogenetic analysis compared 62 other IBDV sequences from different parts of the world and placed the Ghanaian IBDV in genogroup 3 (vvIBDV), closely related to IBDV from Nigeria. In comparison to reference vvIBDV, there were amino acid substitutions at positions 252, 254, and 300. To the best of our knowledge, this is the first report in which an IBDV from a disease outbreak in Ghana has been sequenced and compared with other IBDVs in a phylogenetic analysis. Full article

Infectious bursal disease (IBD) is among the most impactful immunosuppressive diseases of poultry. Its agent, infectious bursal disease virus (IBDV), is prone to both mutation and reassortment, resulting in a remarkable variability. Traditionally, IBDV characterization relies on antigenicity and pathogenicity assessment, but multiple phylogenetic classifications have been recently proposed, whose implementation in molecular surveys helps generating informative and standardized epidemiological data. In the present study, the Algerian IBDV scenario was assessed based on the novel classification guidelines by sequencing portions of both genome segments. Seventy pools of bursal samples were collected in 2022–2023 in 11 districts of Northern Algeria, mostly from broiler flocks. Out of 55 (78.6%) positive flocks, 40 (57.1%) were infected by field strains, which were characterized as very virulent strains (genotype A3B2) and phylogenetically related to previously reported Algerian strains. Significant differences in the percentage of field infections were observed between vaccinated (25/52, 46.2%) and unvaccinated (14/17, 82.3%) groups, and also between birds immunized with live intermediate (13/20, 65.0%) and intermediate plus (10/28, 35.7%) vaccines. Nonetheless, the number of field strain detections suggests a high infectious pressure and the inadequacy of current vaccination efforts, demanding a reevaluation of control measures coupled with attentive monitoring activities. Full article