From surveillance to pathogenesis: characterization of genotype V of chicken infectious anemia virus.

Abstract

INTRODUCTION: Chicken infectious anemia virus (CIAV) is a globally distributed immunosuppressive pathogen that causes substantial economic losses in the poultry industry. METHODS: From 2023 to 2024, 408 clinical samples were collected from diseased chickens to investigate the molecular epidemiology and genetic diversity of CIAV strains circulating in southern China. A representative genotype V strain WSFL24 was further characterized by complete genome sequencing and pathogenicity evaluation using specific-pathogen-free (SPF) chicks. RESULTS: Among the collected samples, 153 (37.5%) tested positive for CIAV. A total of 21 CIAV isolates were isolated and classified the isolates into genotype IIIa (13 isolates) and V (8 isolates). The genotype V strain WSFL24 possessed 31 amino acid substitutions in VP1, including virulence-associated residues (Q139, Q144, and Q394). Moreover, WSFL24 caused 60% mortality, severe anemia (hematocrit <27%), pronounced thymic atrophy, elevated viral loads in lymphoid tissues and cloacal swabs, and distinct histopathological lesions compared with the attenuated reference strain Cux-1 (genotype IIIb). DISCUSSION: These results demonstrate the emergence and enhanced virulence of genotype V CIAV strains in southern China. The findings emphasize the need for continuous molecular surveillance and the development of updated vaccines to control evolving virulent genotypes.