Avian Pathology最新文献

The avian influenza virus is an infectious agent that may cause global health problems in poultry and is potentially zoonotic. In the recent decades, bacterial-derived sialidases have been extensively studied for their ability to inhibit avian influenza virus infections. In this study, the antiviral activity of NanB sialidase from Pasteurella multocida was investigated through in vitro analysis using Madin-Darby canine kidney (MDCK) cells. NanB sialidase was purified from P. multocida to test its toxicity and its ability to hydrolyse its sialic acid receptors on MDCK cells. The H9N2 challenge virus was propagated in MDCK cells until cytopathic effects appeared. Antiviral activity of NanB sialidase was tested using MDCK cells, and then observed based on cell morphology, viral copy number, and expression of apoptosis-mediating genes. NanB sialidase effectively hydrolysed Neu5Acα(2,6)-Gal sialic acid at a dose of 129 mU/ml, while at 258 mU/ml, it caused toxicity to MDCK cells. Antiviral activity of sialidase was evident based on the significant decrease in viral copy number at all doses administered. The increase of p53 and caspase-3 expression was observed in infected cells without sialidase. Our study demonstrates the ability of NanB sialidase to inhibit H9N2 virus replication based on observations of sialic acid hydrolysis, reduction in viral copy number, and expression of apoptosis-related genes. The future application of sialidase may be considered as an antiviral strategy against avian influenza H9N2 virus infections. RESEARCH HIGHLIGHTSNanB sialidase effectively hydrolyses Neu5Acα(2,6)-Gal at a dose of 129 mU/ml.NanB sialidase from Pasteurella multocida can inhibit the entry of H9N2 virus into cells.NanB sialidase of Pasteurella multocida prevents infection-induced cell apoptosis.NanB sialidase reduces the H9N2 viral copy number in MDCK cells.

Infectious bursal disease virus (IBDV) can cause a highly contagious disease, resulting in severe damage to the immune system that causes immunosuppression in young chickens. Both spleen and thymus are important immune organs, which play a key role in eliciting protective immune responses. However, the effects of very virulent IBDV (vvIBDV) strain LJ-5 infection on chicken spleen and thymus are still unknown. In the present study, 3-week-old specific pathogen-free chickens were infected with vvIBDV for 1-5 days. The vvIBDV infection significantly increased the spleen index and decreased the thymus index. Microscopic analysis indicated necrosis, depletion of the lymphoid cells, and complete loss of structural integrity in spleen and thymus. Ultrastructural analysis displayed mitochondrial and nuclear damage, including mitochondrial cristae breaks, and deformation of nuclear membrane in vvIBDV-infected spleen and thymus tissues. Cytokine levels increased in the spleen and thymus after IBDV infection, promoting inflammation and causing an inflammatory imbalance. Moreover, the mRNA expression of apoptosis-related genes was significantly upregulated in the vvIBDV-infected group compared to the control group. Meanwhile, the mRNA expression of mitochondrial dynamics was altered in the spleen and thymus of vvIBDV-infected chickens. These results suggested that vvIBDV infection triggers an imbalance of inflammatory cytokines, and apoptosis in the spleen and thymus, resulting in immune injury in chickens. This study provides basic data for the further study of vvIBDV pathogenesis.

Effective control of infectious bronchitis is a challenge in commercial poultry operations due to the high transmissibility of the virus. Although multiple IBV lineages are circulating in the United States, the DMV1639-type IBV strain (GI-17) is currently the major circulating variant, creating production losses in the poultry industry. This study aimed to test whether the combination of a GA08 (GI-27) and a Mass-type (GI-1) IB vaccines could significantly reduce the transmission of a DMV1639-type (GI-17) field IBV strain in 4-week-old commercial broilers. Half of the birds were directly challenged, whereas the other half of the groupmates were put in contact 24 hours later. Two replicates of the same study setup, including 10 directly challenged and 10 contact birds per group, were run. Transmission of the challenge virus was significantly reduced in vaccinates (R = 0.0), whereas all unvaccinated birds became infected (R = 9.6). Reduced transmission of the DMV1639 IB challenge virus by the combined vaccination programme in broiler chickens was also accompanied by clinical protection. These data are important because prevention of IBV transmission by vaccination will result in overall reduced viral replication and consequently in reduced likelihood of genetic changes that can lead to new variants. This is the first published evidence of the successful transmission control of a DMV1639 IBV strain in chickens.

ABSTRACTNecrotic enteritis (NE) is a severe gastrointestinal disease that poses a significant threat to poultry, leading to progressive deterioration of the small intestine, reduced performance, and increased mortality rates, causing economic losses in the poultry industry. The elimination of antimicrobial agents from chicken feed has imposed a need to explore alternative approaches for NE control, with vaccination emerging as a promising strategy to counteract the detrimental consequences associated with NE. This comprehensive review presents an overview of the extensive efforts made in NE vaccination from 2004 to 2023. The review focuses on the development and evaluation of vaccine candidates designed to combat NE. Rigorous evaluations were conducted in both experimental chickens and broiler chickens, the target population, to assess the vaccines' capacity to elicit an immune response and provide substantial protection against toxin challenges and experimental NE infections. The review encompasses the design of vaccine candidates, the antigens employed, in vivo immune responses, and the efficacy of these vaccines in protecting birds from experimental NE infection. This review contributes to the existing knowledge of NE vaccination strategies, offering valuable insights for future research and development in this field.

The poultry population is an integral part of Ethiopia's Gross Domestic Product (GDP) but, due to various infectious diseases such as infectious bursal disease (IBD), the expected economic impact in the country remains limited. The status of the disease in Ethiopia is obscured; thus, a systematic review and meta-analysis were employed to estimate the overall pooled prevalence of IBD in Ethiopia. Meta-analysis was conducted to determine the effects of each identified risk factor, while meta-regression and sub-group analysis were employed to assess the relationship between study-level covariates and effect size. The pooled prevalence of IBD in Ethiopia was 69.4% (95% CI 30.7-96.2), while the pooled logit prevalence was 0.94 (95% CI: 0.68-1.20) with significant inter-study variance (Q test = 948.28, df = 43, P < 0.001; τ² = 0.71, I²= 95.47%). A small-study effect was detected in the regression-based Egger test (Prob > |z| < 0.0001). Significant variation was observed among different groups such as sex, age, breed, and type of farm of the chickens. The effect size for the study period from 2018 to 2021 was significantly lower by -0.204 compared to the study period from 2009 to 2015 (P < 0.0001. In conclusion, the IBD pooled prevalence estimate is high, even though the number of studies in the country is insufficient. The high prevalence of the disease requires prompt attention from all stakeholders in the sector to bring it under control through comprehensive disease prevention and control intervention strategies.

Research highlights: Typical E. cecorum lesions can be reproduced in SPF broilers after intravenous, aerosol and oral inoculations.The respiratory route is potentially an infection route for pathogenic E. cecorum bacteria.Co-infections tested in this study or dexamethasone do not exacerbate the proportion of E. cecorum lesions.M.s. in combination with IBV or NDV vaccines exacerbates the proportion of positive reisolations.Immunosuppression induced by early CAV infection increases the proportion of positive reisolations.

AbstractSalmonella enterica serovar Gallinarum biovar Gallinarum is a pathogenic bacterium that causes fowl typhoid (FT), affecting chicken flocks worldwide. This study aimed to evaluate the emergence, dissemination and genomic profile of S. Gallinarum lineages from Brazil. Twelve whole-genomes sequences (WGS) of different S. Gallinarum strains isolated from Brazilian poultry farms (2014 to 2018) were obtained and used to construct a dataset with other 31 previously published data (five more from Brazil). Brazilian strains phylogenetic diversity, temporal evolution and antimicrobial resistance/virulence genomic profile were evaluated. Sixteen (94.1%) Brazilian strains were from sequence type ST78 and one (5.9%) was from ST331. All S. Gallinarum strains clustered into five different clades/lineages (I to V), all circulating in South America and four (I, II, III, IV) in Brazil. The time of most recent common ancestor (tMRCA) of all strains was many centuries ago, but the lineages detected in South America (II and V) had tMRCA in recent decades. IncFIC(FII), IncFII(S) and ColRNAI were plasmid replicons frequently found in the lineages from Brazil, but antimicrobial resistance genes were scarce. Only two resistance genes (aac(6')-Iaa and mdf(A)) were detected in most strains, while other two (blaTEM-106 and fosA3) were present in some isolates. It was also observed important differences in the virulence genomic profile of the different lineages, highlighting lineage IV, which does not carry the very important Salmonella pathogenicity island 1 (SPI1) genes cluster. In summary, this study reveals the emergence and dissemination of four different lineages of S. Gallinarum in Brazil.

Salmonella Pullorum (S. Pullorum) and Salmonella Gallinarum (S. Gallinarum) are the biovars of Salmonella enterica serovar Gallinarum that are responsible for pullorum disease and fowl typhoid, respectively, in poultry. Traditional serological methods fail to quickly differentiate between these biovars due to their identical O antigenic factors (O9 and O12). Although single nucleotide polymorphism (SNP)-based methods have been used to distinguish between the biovars, they often lack the required accuracy and effectiveness. In this study, we developed a PCR high resolution melt (PCR-HRM) assay, which targeted a SNP at position 665 of the fimH gene, for rapid differentiation between S. Pullorum and S. Gallinarum. Our method showed 100% specificity and was able to detect as little as 0.033 pg of S. Pullorum DNA and 0.027 pg of S. Gallinarum DNA. The PCR-HRM results for 547 clinical isolates were in complete agreement with traditional serological methods. This PCR-HRM assay significantly reduced identification time and provided high throughput, efficient testing. This makes it a practical and reliable tool for accurate differentiation between S. Pullorum and S. Gallinarum in clinical settings.

Ascites syndrome (AS) is a deadly condition in fast-growing chickens, preceded by pulmonary arterial hypertension (PAH), where the angiotensin II type 1 receptor (ATR1) plays a role. We investigated whether allicin (ALLI), a garlic derivative, could (a) interact with broiler ATR1, (b) affect ascites-related traits [haematocrit content (Hct%), blood oxygen saturation (SaO₂), and the right-to-total ventricular weight ratio (RV:TV)], (c) modify ATR1 expression in the lung, heart, and liver, alongside ascites mortality and growth performance in Ross 308 broilers raised at high altitude and under cold temperatures promoting PAH/AS. Three groups (n = 70 each) were studied: 0-ALLI (untreated), 1-ALLI (allicin 1 mg/kg bodyweight/daily at 14-27 days of age by oral-oesophageal route), and 2.5-ALLI. After 3-6 weeks, Hct%, SaO₂, RV:TV ratios, and ATR1 expression in the lung, heart, and liver, were evaluated. Weekly productive performance and AS mortality were recorded. Molecular dockings and dynamic simulations predicted that ALLI might inhibit broiler ATR1 in a transitory manner. At 42 days of age, birds in the 2.5-ALLI group exhibited lower Hct% and lower RV:TV values, while ALLI marginally enhanced SaO₂. ATR1 expression in the 1-ALLI and 2.5-ALLI groups was higher (i.e. restored) in the lungs and heart, respectively, but not in the liver compared with the untreated group. Productive performance remained unaffected by ALLI, and 2.5-ALLI provided a protection of 4.3% against ascites mortality. In conclusion, 2.5-ALLI mitigated PAH/AS traits in the lungs and heart without compromising broiler productive performance. Further studies adjusting ALLI doses and combinations are warranted. RESEARCH HIGHLIGHTSBroilers bred at >2000 m OSL and <20°C were treated with 1 or 2.5 mg allicin per os.Allicin at 2.5 mg per os decreased haematocrit and right ventricular hypertrophy.Allicin treatments restored ATR1 expression in the heart and lungs.Productive performance of broilers was not affected by allicin treatments.Allicin is a promising candidate to enhance the quality of poultry production.