Isolation and Progeny Transmission of Non-Temperature-Sensitive MS-H Vaccine Strains of Mycoplasma synoviae from Temperature-Sensitive MS-H-Vaccinated Laying Breeder Hens

This pilot study reports the vertical transmission and reverse thermosensitivity of the MS-H vaccine strain of Mycoplasma synoviae (MS) by RAPD in commercial breeders and their progeny. At two weeks of age, breeders were vaccinated with the ts+ MS-H strain. At 9 weeks of age, an outbreak of infectious synovitis (IS) was detected in the progeny. Tracheal swab samples were collected from breeders at 24, 39, 48, and 70 weeks of age. At 9 weeks, pullets swab from the elbow joints were collected. RAPD was performed on the isolates at 39.5°C, and the same ts- MS-H strains were identified in the breeder hens and their progeny. Tracheal swabs from breeder hens were negative to MS isolation at 37°C and 39.5°C at 24- and 39-weeks. MS isolation was recovered from tracheal swabs from 9/10 and 10/10 breeders at 48- and 70- week. At 9 weeks of age in the progeny, MS was isolated from tracheal swabs of 10/10 from non-IS pullets. MS was isolated from 9/10 joints samples. The isolates from breeder hens and their progeny showed non-significant differences in five antimycoplasmic MIC100 values;otherwise, enrofloxacin presented a significant difference in MIC100 value (p < 0.05). This investigation demonstrated the reversal of the thermosensitivity, pathogenicity, and vertical transmission of the MS-H strain. Consequently, it is crucial to contemplate the danger of reversing pathogenicity and transmission to progeny when applying the MS-H vaccine strain.

鸡滑液囊支原体病的诊断及防控技术研究进展

滑液囊支原体病是一种由滑液囊支原体(Mycoplasma synoviae)引起的鸡(Gallus gallus f. domestic)的急性或慢性传染病,可导致雏鸡死亡、呼吸困难、跛行、产蛋下降等,给家禽养殖业造成较大经济损失。概述了滑液囊支原体病主要诊断技术和防控技术的研究进展,并针对其研究进展分析其优缺点,以期为防治滑液囊支原体病提供参考。

Identification and antibiotic susceptibility evaluation of Mycoplasma synoviae isolated from chickens in central China

Mycoplasma synoviae(M.synoviae)infections have become an increasingly serious concern in China because they cause huge economic losses to the poultry industry.Antibiotic treatment is one of control strategies that can be used to contain clinical outbreaks in M.synoviae-free flocks,especially because the bacteria can be transmitted through eggs.To understand M.synoviae infection status in farms of central China and the antibiotic susceptibility of the circulating strains in vivo and in vitro,485 samples were collected from five provinces from 2019 to 2021.Fifty-two strains were isolated and identified.Determination of the minimum inhibitory concentration(MIC)of eight antibiotics(tylvalosin,tiamulin,tilmicosin,lincomycin,enrofloxacin,chlortetracycline,doxycycline and tylosin)for isolates showed that tylvalosin,doxycycline and tiamulin were effective against 52 clinical isolates(MIC values≤0.0625-0.25μg/mL,≤0.0625-1μg/mL,and 0.25-2μg/mL,respectively).Tilmicosin,enrofloxacin and lincomycin had high MICo values(>32μg/mL).An artificial M.synoviae infection model was established in chickens for evaluation of the short-term therapeutic effect of these antibiotics.After 5 days of medication,doxycycline(200 mg/L)showed a superior ability to inhibit M.synoviae compared with other groups,as did tylvalosin(200 mg/L).Furthermore,the therapeutic efficacy of tylvalosin(0.4μg/mL)on intra-embryo-injected M.synoviae was higher than that of tiamulin at the same dose.A combination of MiC values determined in vitro and therapeutic effects observed in vivo revealed that tylvalosin and doxycycline had the best therapeutic effects.Tylvalosin also showed better inhibitory effects on the vertical transmis-sion of M.synoviae than tiamulin.