Genetic characterization and antimicrobial profiling of bacterial isolates collected from Nile tilapia (Oreochromis niloticus) affected by summer mortality syndrome.

In recent years, Egyptian tilapia aquaculture has experienced mortality episodes during the summer months. The causative agents responsible for such mortalities have not been clearly identified. A total of 400 fish specimens were collected from affected tilapia farms within five Egyptian governorates. A total of 344 bacterial isolates were identified from the examined fish specimens. Bacterial isolates were grouped into seven genera based on API 20E results. The most prevalent pathogens were Aeromonas spp. (42%), Vibrio spp. (21%), and Streptococcus agalactiae (14.5%). Other emerging infections like, Plesiomonas shigelloides (10%), Staphyloccocus spp. (8%), Pseudomonas oryzihabitans, and Acinetobacter lwoffii (2.3%) were also detected. Sequence analysis of the 16S ribosomal RNA bacterial gene of some isolates, confirmed the phenotypic identification results. The analysis of antibiotic resistance genes revealed the presence of aac(6')-Ib-cr (35.7%), blaCTX gene (23.8%), qnrS (19%), ampC (16.7%), floR (14.3%), sul1, tetA, and van.C1 (2.4%) genes in some isolates. The antimicrobia resistance gene, qac was reported in 46% of screened isolates. Bacterial strains showed variable virulence genes profiles. Aeromonas spp. harboured (act, gcat, aerA, lip, fla, and ser) genes. All Vibrio spp. possessed the hlyA gene, while cylE, hylB, and lmb genes, were detected in S. agalactiae strains. Our findings point to the possible role of the identified bacterial pathogens in tilapia summer mortality syndrome and highlight the risk of the irresponsible use of antibiotics on antimicrobial resistance in aquaculture.

Genetic heterogeneity of chicken anemia virus isolated in selected Egyptian provinces as a preliminary investigation.

Chicken anemia virus (CAV) is a widespread and economically significant pathogen in the poultry industry. In this study 110 samples were collected from various poultry farms in selected Egyptian provinces during 2021-2022 and were tested against CAV by Polymerase Chain Reaction (PCR), revealing 22 positive samples with 20% incidence rate. Full sequence analysis of five selected CAV strains revealed genetic variations in VP1, VP2, and VP3 genes. Phylogenetic analysis grouped the Egyptian strains with reference viruses, mainly in group II, while vaccines like Del-Rose were categorized in group III. Recombination events were detected between an Egyptian strain (genotype II) and the Del-Rose vaccine strain (genotype III), indicating potential recombination between live vaccine strains and field isolates. To evaluate pathogenicity, one Egyptian isolate (F883-2022 CAV) and Del-Rose vaccine were tested in Specific Pathogen Free (SPF) chicks. Chicks in the positive group displayed clinical symptoms, including weakness and stunted growth, with postmortem findings consistent with CAV infection. The vaccine group showed milder symptoms and less severe postmortem changes. This study provides important insights into the genetic diversity of CAV in selected Egyptian poultry farms showing recombination event between field strain and vaccine strains, highlighting the need for advanced vaccination programs, especially for broilers.

Detection of Novel Goose Parvovirus Disease Associated with Short Beak and Dwarfism Syndrome in Commercial Ducks.

Derzsy's disease causes disastrous losses in domestic waterfowl farms. A genetically variant strain of Muscovy duck parvovirus (MDPV) and goose parvovirus (GPV) was named novel goose parvovirus (NGPV), which causes characteristic syndrome in young ducklings. The syndrome was clinically characterized by deformity in beaks and retarded growth, called short beaks and dwarfism syndrome (SBDS). Ten mule and pekin duck farms were investigated for parvovirus in three Egyptian provinces. Despite low recorded mortality rate (20%), morbidity rate was high (70%), but the economic losses were remarkable as a result of retarded growth and low performance. Isolation of NGPV was successful on primary cell culture of embryonated duck liver cells with a clear cytopathic effect. Partial gene sequence of the VP1 gene showed high amino acids identity among isolated strains and close identity with Chinese strains of NGPV, and low identity with classic GPV and MDPV strains. To the best of our knowledge, this can be considered the first record of NGPV infections in Egypt.

Pathological changes, shedding pattern and cytokines responses in chicks infected with avian influenza-H9N2 and/or infectious bronchitis viruses.

Avian influenza H9N2 (AIV-H9N2) and Infectious bronchitis (IB) viruses are the most commonly isolated viruses from poultry flocks suffering from respiratory signs with mortalities. The outcome of co-infection with both viruses hasn't been yet well understood. In this study, eighty 1-day-old specific pathogen free chicks were divided into four distinct groups. Group 1 remained uninfected as negative control group; groups 2, 3 and 4 were inoculated with either AIV-H9N2 or IBV or co infected with AIV-H9N2 followed by IBV three days post inoculation respectively. Chicks were monitored for clinical and pathological changes, virus shedding and both Interleukin-6 (IL6) and Interferon gamma (IFNγ) cytokines immune responses. Clinical signs varied from mild to moderate respiratory signs in all challenged groups but were more severe in group 4 with mortalities in groups 3 and 4. Tracheal shedding of both viruses washigher in group 4 than group 2 and 3. Mean AIV-H9 virus titer in lung and kidney was higher in group 4 than group 2 in all time points. IFNγ mRNA gene expression in lung was significantly lower in groups3 and 4. In conclusion, this study reports that co-infection of chicks with both viruses enhances the pathogenicity, increases both viruses shedding and extend AIV-H9 replication with impairment of IFNγ stimulation in lung.