Molecular Characterization and Phylogenetic Analysis of Fowl Adenoviruses Isolated from Broiler Chicken Flocks

Abstract

FADV has caused high economic losses in poultry industry in Egypt in the last few years. The study aimed to detect and genetically characterize the fowl adenovirus (FAdV) species prevalent in Egyptian commercial broiler chicken flocks during 2023. The 63 suspected samples were collected from Egyptian broiler chickens from 5 governorates during 2023. The molecular characterization was performed by using polymerase chain reaction (PCR) and the positive samples was isolated in primary chicken embryo liver (CEL) cells. The genetic characterization of 8 selected samples represented different governorates by sequencing of loop 1 (L1) of the hexon gene. Clinically, the poultry suffered from depression, watery diarrhea, and ascites and decreased body weight with a mortality rate of 10–30%. The post-mortem inspection showed liver was pale, enlarged with petechial haemorrhage. 27 out of 63 samples (42.8%) were positive by PCR. The molecular charctersation of the L1 hexon gene’s revealed that the FADV (from Eg-ANY1-2023 to EG-ANY4-2023) genetically charcterized as FADV-D 2/11 strains, the FADV-EG-ANY5-2023 to FADV-EG-ANY8-2023 genetically characterized as FADV E/8a and FADV E/8b. By mutation analysis, the strains in our study related to FADV-E/8a (FADV-EG-ANY5, ANY6) had R171K in the HVR4 and strain related to 8b (FADV-EG-ANY7, ANY8) had S95N in the HVR2 and A91T between HVR1 and HVR2 compared to other reference strains. Thus, these findings demonstrate that many mutated virus genotypes are circulating in commercial chicken flocks. Further research is needed to study the pathogencity of these strains and implement control measures and vaccine production to prevent economic loss in the poultry industry.