Serological survey on the prevalence of chicken infectious anemia virus in broiler breeder and layer farms in some selected areas of Bangladesh

Molecular Detection and Genetic Characterization of Avian Leukosis Virus From Field Outbreaks in Bangladesh

Avian leukosis is a significant viral disease affecting chicken populations globally, including Bangladesh, resulting in high mortality and morbidity rates and causing substantial economic losses in the commercial poultry industry. This study aimed to detect avian leukosis virus (ALV) during recent outbreaks in Bangladesh, utilising a molecular-based approach. A total of 14 liver samples were collected from the suspected layer flocks in Bangladesh. The diagnosis of ALV infection in chickens was confirmed through necropsy, histopathological examinations, reverse transcription-polymerase chain reaction (RT-PCR), and sequence analysis. Gross observations revealed severe liver enlargement with scattered white nodules on the surface in the infected chickens. Histopathological observations showed the infiltration of huge mononuclear inflammatory cells in the periportal area of liver and microvesicular fatty degeneration and necrosis of some hepatocytes. RT-PCR results identified three samples positive for the env gene of ALV. Sequence analysis of the env genes demonstrated high homology among the identified strains (97%-98%) and with reference strains (92%-96%) at the nucleotide level. The phylogenetic tree revealed close relatedness of the three identified strains to reference strains from India, USA, and China. Mutational analysis indicated several mutations throughout the envelope glycoprotein of the identified strains. Protein structure analysis showed minor changes in the hydrophobic region of the envelope protein of the identified strains. In conclusion, this study, the first detailed investigation in Bangladesh, contributes to understanding ALV epidemiology, highlights genetic diversity, and emphasises the necessity for further investigations and the implementation of effective control measures in the affected regions.

Nonstructural protein VP2 of chicken anemia virus triggers IFN-β expression via host cGAS

Chicken anemia virus (CAV) constitutes an important economic threat for the poultry industry. Advancing the understanding of the pathogenic process of CAV infection, we had previously demonstrated that CAV VP1 has the ability to inhibit expression of IFN-β via cGAS-STING signalling pathway. Here to go further to reveal this regulatory role of viral phosphatase VP2, we have performed protein-protein interaction assays with cGAS adaptors, as well as IFN-β induction screenings. Contrary to VP1, VP2 of CAV stimulates the expression of IFN-β, a regulatory effect more closely associated with cGAS (in the context of the cGAS-STING axis) than with STING, TBK1 or IRF7. The results reported here offer new insights about the molecular mechanisms that varied viral proteins act in a timely manner on the host during CAV infection.

Genetic diversity, distribution, and evolution of chicken anemia virus: A comparative genomic and phylogenetic analysis

Chicken infectious anemia (CIA) is an immunosuppressive poultry disease that causes aplastic anemia, immunosuppression, growth retardation and lymphoid tissue atrophy in young chickens and is responsible for huge economic losses to the poultry industry worldwide. The disease is caused by the chicken anemia virus (CAV), which belongs to the genus Gyrovirus, family Anelloviridae. Herein, we analyzed the full-length genomes of 243 available CAV strains isolated during 1991-2020 and classified them into two major clades, GI and GII, divided into three and four sub-clades, GI a-c, and GII a-d, respectively. Moreover, the phylogeographic analysis revealed that the CAVs spread from Japan to China, China to Egypt and subsequently to other countries, following multiple mutational steps. In addition, we identified eleven recombination events within the coding and non-coding regions of CAV genomes, where the strains isolated in China were the most active and involved in ten of these events. Furthermore, the amino acids variability analysis indicated that the variability coefficient exceeded the estimation limit of 1.00 in VP1, VP2, and VP3 proteins coding regions, demonstrating substantial amino acid drift with the rise of new strains. The current study offers robust insights into the phylogenetic, phylogeographic and genetic diversity characteristics of CAV genomes that may provide valuable data to map the evolutionary history and facilitate preventive measures of CAVs.

A new rapid and sensitive method for detecting chicken infectious anemia virus

Since the chicken infectious anemia virus (CIAV) was discovered in 1979, which has been reported as an economically significant and immunosuppressive poultry disease in the world. A novel clinical detection method for the prevention and control of CIAV in the poultry sector is urgently needed. Here, we established a real-time recombinase-aided amplification assay (RAA) for CIAV on-site with a rapid, highly sensitive, strongly specific, low-cost, and simple operational molecular diagnosis detection method. The primers and probe were developed using the CIAV VP2 gene sequence, which has a 117-bp specific band. This assay, which could be carried out at 41°C and completed in 30 min without cross-reactivity with other viruses, had the lowest detection limit of 10 copies of CIAV DNA molecules per reaction. Furthermore, the kappa value of this assay was 0.947, the sensitivity was 93.33%, and the specificity was 100% when compared to the real-time quantitative polymerase chain reaction assay (real-time qPCR). These results indicate that using a real-time RAA assay to detect CIAV on-site could be beneficial. In the future, the real-time RAA test may be a regular assay for the prevention and control of CIAV, as well as help the reduction of economic losses in the poultry business.

Effects of Caulis Spatholobi Polysaccharide on Immunity, Intestinal Mucosal Barrier Function, and Intestinal Microbiota in Cyclophosphamide-Induced Immunosuppressive Chickens

The protective effects of Caulis Spatholobi polysaccharide (CSP) on immune function, intestinal mucosal barrier, and intestinal microflora in cyclophosphamide (CY)-induced immunosuppressed chickens have been rarely reported. This study was designed to investigate the cecal microbiota in chickens and to elucidate the immune mechanism involved in the CSP effect on CY induced-immunosuppressed chickens. A total of 288 cocks were equally divided into six groups and used to evaluate the immune effect of CSP. Results showed that the CSP increased the body weight and immune organ index of immunosuppressed chickens, significantly increased the secretion of cytokines (IL-4, IL-10) and immunoglobulins (IgG, IgM) in sera of chickens, and restored the body immune function. The CSP reduced intestinal injury of the jejunum and ileum, increased the ratio of the intestinal villus height to crypt depth (V/C), improved the expression of tight junction protein, and protected intestinal health. The CSP activated the toll-like receptor (TLR)/MyD88/NF-κB pathway and enhanced the expression of TLR4, MyD88, NF-κB, Claudin1, and Zo-1, protecting the intestinal tract. High-throughput sequencing of the 16S rRNA gene showed that CSP increased species richness, restored CY-induced intestinal microbiome imbalance, and enhanced the abundance of Lactobacillus in the intestinal tract. In conclusion, our study provided a scientific basis for CSP as an immune enhancer to regulate intestinal microflora and protect intestinal mucosal damage in chickens.