Experimental infection of ducks with Mycoplasma gallisepticum

Specific-pathogen-free ducks 24 and 180 days old were inoculated intranasally with the S6 strain of Mycoplasma gallisepticum (MG). No significant gross lesions were found in trachea, lung or air sacs at 7 or 28 days postinfection (PI). MG was recovered from the infraorbital sinus and trachea but not from the air sacs 7 and 28 days PI. A few ducks responded serologically by developing agglutinating antibody. MG multiplied in embryonated duck eggs but to lower titers than in embryonated chicken eggs.     

Response of chickens to inoculation with a temperature-sensitive mutant of Mycoplasma gallisepticum

Newly hatched chickens were inoculated intranasally with either the S6 or TS 100 strain of Mycoplasma gallisepticum (MG) or they were left uninoculated. The three groups of chickens did not differ discernibly in body, spleen, or bursa weight during the 27-day sampling period. However, the S6-inoculated chickens showed a more pronounced cellular response in the nasal passages and had nearly complete lymphoid depletion in the spleens. The TS 100-inoculated birds expressed only a mild cellular reaction, which was localized in the nasal passages. Uninoculated chickens appeared normal histologically. Serologic tests such as rapid serum plate agglutination, hemagglutination-inhibition, and radioimmunoassay were able to detect antibody responses of chickens to MG inoculations yet could not differentiate the response to TS 100 from the response to S6. Tracheal secretions in intact TS 100-inoculated chickens contained antibodies to MG, yet only one-half of the bursectomized inoculated chickens contained detectable antibody, which appeared to be IgG. This led to the conclusion that bursectomy suppresses the appearance of locally synthesized IgG antibodies to MG in tracheal washings. The locally produced antibody was considered important in the development of resistance induced by intranasal inoculation of TS mutants.     

Vaccination of turkeys against air-sac infection with a temperature-sensitive mutant of Mycoplasma gallisepticum

Turkeys were vaccinated with temperature-sensitive (TS) mutants of Mycoplasma gallisepticum (MG) to determine pathogenicity and immunogenicity. TS 37 was apathogenic yet immunogenic to turkeys, TS 100 was highly pathogenic, and TS 102 was slightly pathogenic and nonimmunogenic. Five or 7 weeks after intranasal vaccination of turkeys with the TS 37 mutant, a highly statistically significant resistance against intra-air-sac challenge with the S6 strain of MG was observed.     

An Infection in Chickens with a Strain of Mycoplasma gallisepticum of Low Virulence

A slow-spreading infection due to a strain of Mycoplasma gallisepticum was detected serologically in a flock which remained free of clinical symptoms. The strain was shown to be tylosin resistant. Serological studies indicated that vertical transmission occurred.     

Immunogenicity of Mycoplasma gallisepticum

The serological response and protective immunity elicited in the chicken by the pathogenic Ap3AS strain and the moderately pathogenic 80083 strain of Mycoplasma gallisepticum and variants of strain 80083 attenuated by repeated passage in mycoplasma broth were investigated. Strain 80083 elicited a substantial serum antibody response after administration either in drinking water or by conjunctival sac instillation to 7-week-old SPF chickens. No vaccinated chickens developed air sac lesions when challenged by intra-abdominal (IA) injection with the virulent Ap3AS strain. Chickens vaccinated with strain 80083M (50 broth passages) showed only a weak serological response but were substantially protected when challenged 4 weeks after vaccination. Chickens vaccinated with 80083H (100 broth passages) were serologically negative 4 weeks after vaccination and developed severe air sac lesions after challenge. Thirty-seven-week-old hens vaccinated 6 months previously with strain 80083 had high serum antibody levels and were completely protected against IA challenge with the homologous strain. However, 4/6 showed mild air sac lesions when challenged intra-abdominally with strain Ap3AS. Another group showed high M. gallisepticum serum antibody levels 6 months after vaccination with strain Ap3AS but 4/6 and 2/6 showed mild lesions after IA challenge with strains Ap3AS or 80083, respectively. Strains 80083 or 80083M were administered by conjunctival sac instillation to susceptible 11-week-old commercial pullets at the time of fowl pox vaccination. The concurrent use of both vaccines had no apparent adverse effect on the health of the chickens. Similar protection against IA challenge with strain Ap3AS was produced with the M. gallisepticum vaccines whether used alone or in combination with fowl pox.     

Evaluation of protection against Mycoplasma gallisepticum infection in chickens vaccinated with the F strain of M. gallisepticum

The effect of vaccination with the F strain of Mycoplasma gallisepticum (MG) on protection against challenge with a tylosin-resistant strain of MG was evaluated. White leghorn chickens vaccinated via eyedrop at 6 weeks of age were subsequently challenged with various dilutions of the tylosin-resistant MG strain, as were unvaccinated controls. Three days later, tracheal swabs were collected and cultured in medium with and without tylosin to distinguish between the vaccine and challenge strains. The mean infectious dose of the challenge strains was 3.8 log10 higher in the vaccinated group than in the controls, and the vaccinated group harbored fewer challenge organisms in the trachea. These findings suggest that the F strain of MG induces protection against infection with field strains of MG and that long-term vaccination with the F strain in multiple-age layer farms may result in replacement of field MG strains by the F strain.     

鸡毒支原体研究概况

鸡毒支原体(MG)是对养禽业危害很大的支原体,主要导致禽类慢性呼吸道疾病(CRD),以禽的结膜炎、产蛋率及饲料转换率下降、屠宰率下降等为主要特征。MG可通过垂直和水平传播方式在鸡群中传播,每年给全球家禽产业带来巨大经济损失。随着对MG细胞表面抗原黏附素蛋白(pMGA)和PvpA、GapA的结构与功能研究的深入,K株、TG5株等MG疫苗研究也取得较大进展。由于抗生素的滥用,MG基因中也发生耐药突变,产生了QRDRs等抗药结构,导致MG在耐药性上也出现新的特点。论文主要对国内外MG的疫苗开发、耐药情况和检测技术等进行综述,旨在对家禽MG的综合防控提供借鉴。     

Chemotaxis in Mycoplasma gallisepticum

Boyden-type chemotactic chambers were used to demonstrate that Mycoplasma gallisepticum (MG) was capable of migrating into chemotactic membranes. Scanning electron microscopy was used to confirm that MG could penetrate the membranes. To further demonstrate the invasive ability of MG, MG was deposited on the shell membranes of 9-day-old chicken embryos, and after 6 days of incubation, the presence of MG DNA in the allantoic fluids was detected by polymerase chain reactions. These results indicate that MG can penetrate cellular membrane, possibly by going through the porous cellular surface.     

Immunization of chickens with temperature-sensitive mutants of Mycoplasma gallisepticum

Temperature-sensitive (TS) mutants of the S6 strain of Mycoplasma gallisepticum (MG) were used to immunize newly hatched chickens. Immunized chickens developed antibodies to the wild-type (WT) S6 strain as demonstrated by serologic tests. MG was recovered from nasal cavities but not from the lower respiratory tract of the immunized chicks. Three weeks after intranasal immunization, chickens were challenged via the air sacs with the virulent S6 strain. Immunized chickens were significantly better protected from development of air-sac lesions than were controls.     

鸡败血支原体接种鸡体液免疫的变化规律

SPF鸡接种鸡败血支原体R株、F株和油乳剂苗后，用ELISA检测IgM、IgG和IgA的变化规律，发现特异性IgM出现时间存在差异；强毒株感染后IgM始终存在，因此可作为临诊感染的指证。油乳剂苗能产生IgA，证明油乳剂苗能诱导产生局部免疫。     

Meningoencephalitis in commercial meat turkeys associated with Mycoplasma gallisepticum.

Mycoplasma gallisepticum (MG) infection was diagnosed in three different flocks of 12-to-16-week-old commercial meat turkeys displaying torticollis and/or opisthotonos. MG was isolated from the brain, air sacs, trachea, and sinus of one bird with neurological signs. Histological examination of brains in all three cases revealed moderate-to-severe encephalitis with lymphoplasmacytic cuffing of vessels, fibrinoid vasculitis, focal parenchymal necrosis, and meningitis. Birds with neurological signs were seropositive for MG by the serum-plate agglutination and hemagglutination-inhibition tests. The encephalitic form of MG has been described previously but is rarely mentioned in the current literature.     

Field evaluation of tylosin premix in layers previously vaccinated with a live Mycoplasma gallisepticum vaccine

Mycoplasma gallisepticum infection results in numerous clinical signs including a reduction in egg production in laying chickens. Attempts to prevent mycoplasmosis have included vaccination with both killed and attenuated live M. gallisepticum strains. Live vaccines provide reduction in clinical signs and have been shown to replace indigenous strains when used in a consistent program for several placements. Antibiotic therapy is another option for controlling losses associated with mycoplasmosis. Therapeutic antibiotics with activity against mycoplasma approved for use in poultry include tetracyclines and tylosin. These drugs also are approved for feed efficiency when administered in the feed at levels below the therapeutic index for mycoplasma. The data presented here suggest that birds vaccinated with the live 6/85 strain of M. gallisepticum and then fed tylosin, at the approved level for feed efficiency, exhibit a serologic vaccine response similar to that of unmedicated birds but show improved feed efficiency.     

SPF鸡人工感染鸡败血霉形体后血液生物化学变化

用鸡败血霉形体（ＭＧ）国际标准强毒Ｒ株人工感染１５日龄ＳＰＦ鸡,在感染后１５ｄ采血作血液生物化学检验。结果：ＴＢｉｌ、ＧＯＴ、ＧＰＴ、ＡＬＰ、ＬＤｈ、ＣＯ２－ＣＰ、ＣＲＥ、ＢｕＮ、ＣＲＥ－Ｕ、无机磷、Ｍｇ＾２＋明显升高,而ＴＰ、ＡＬＢ、Ａ／Ｇ、Ｃｈｏ、Ｇｌｕ、Ｃａ＾２＋等明显下降,ＲＢＣ和Ｈｂ下降,ＷＢＣ上升,其中ＬＣ和嗜酸性白细胞明显上升。说明ＭＧ不仅造成呼吸系统障碍,也对肝功能和功能产生较大影