Isolation and identification of Mycoplasma synoviae in Hebei, China, and evaluation of the immune protection efficacy of inactivated vaccines

Abstract

Mycoplasma synoviae (MS) causes infectious synovitis and eggshell abnormalities in chickens, leading to major economic losses. Vaccination is essential for control, but strain differences often reduce effectiveness. To develop a region-specific inactivated vaccine, MS strains were isolated from poultry farms, and a highly virulent strain (CD-1) was selected using embryo infection assays. A chicken-challenge model identified footpad injection of 0.2 mL at 10⁸ CCU/mL as the optimal infection method. Inactivated vaccines using CD-1 (10¹⁰ CCU/mL) with white oil or propolis adjuvants were tested. The propolis-based vaccine showed the best protection, reaching 80 % efficacy at 0.3 mL/bird, outperforming the white oil and commercial vaccines. This study supports the development of targeted MS vaccines for Hebei.

Keywords: Immune Protection; Inactivated Vaccines; Mycoplasma synoviae; Propolis; White oil.

Fig. 1

A Growth curve of MS CD-1. The growth of the CD-1 strain was monitored by measuring CCU at different time points. All experiments were performed in triplicate. Bars represent mean ± SEM. B. Serum antibody test results of SPF chickens in each group after immunization. Bars represent mean ± SEM. ***P< 0.001. ns means no difference. C-E. Histopathological sections of trachea (C), lungs (D), and footpads (E) collected after vaccination and challenge (magnification, 200 ×). (a) Blank control group 1; (b) Blank control group 2; (c) YBF-MS1 inactivated vaccine group; (d) 0.1 mL propolis-adjuvanted vaccine group; (e) 0.3 mL propolis-adjuvanted vaccine group; (f) 0.5 mL propolis-adjuvanted vaccine group; (g) 0.1 mL white oil-adjuvanted vaccine group; (h) 0.3 mL white oil-adjuvanted vaccine group; (i) 0.5 mL white oil-adjuvanted vaccine group. F. Changes in serum antibody titers in chickens immunized with propolis adjuvant vaccine. Chickens were bled from the ulna vein on 7, 14, 21 days and 1-6 months post-immunization, and serum was separated to determine the antibody titers. The "—" line represents the lowest antibody titers that provides immune protection. Bars represent mean ± SEM.