Research note: Prevalence and vlhA gene genotyping analysis of Mycoplasma synoviae in poultry from 2021 to 2023 in central China.

Mycoplasma synoviae (MS) is an important avian pathogen associated with respiratory disease, infectious synovitis, and growth retardation in poultry and causes significant economic losses to the poultry industry in China. Although effective prevention relies on vaccination, the currently licensed live vaccine strain, MS-H, shows limited efficacy. Updated epidemiological data are needed to support vaccine candidate screening. This study was performed to investigate the prevalence and genotype distribution of MS in poultry in central China. A total of 1,534 tracheal, laryngeal, and joint cavity samples were collected from chickens with suspected MS infection between 2021 and 2023. Samples were tested by PCR targeting the variable lipoprotein hemagglutinin adhesin gene (vlhA). The overall MS positivity rate among the collected samples was 55.48 %. Eighty-two positive samples were randomly selected for sequencing, and genotyping was performed based on the proline-rich repeat (PRR) region of the vlhA gene. Three genotypes were identified, with genotype L accounting for 91.46 % of positive samples. Phylogenetic analysis revealed significant genetic divergence between field strains and the vaccine strain MS-H (genotype C). These findings highlight the dominance of genotype L in central China and provide essential molecular epidemiological data for the development of more effective control strategies and regionally adapted vaccines.