Mycoplasma gallisepticum vaccination: effects on egg transmission and egg production

The effects of Mycoplasma gallisepticum (MG) vaccination on egg transmission of MG and egg production were evaluated. Leghorn hens vaccinated with live MG (strain F), with strain F plus MG bacterin, with one dose of MG bacterin, or with two doses of MG bacterin all transmitted MG through the egg at a significantly lower level than unvaccinated controls. Hens vaccinated with two doses of MG bacterin had the longest lag before detectable transmission of MG through the egg. All vaccinated groups were protected against the egg-production drop seen in unvaccinated hens challenged with virulent MG.     

Effect of Mycoplasma gallisepticum bacterin on egg-transmission and egg production

Groups of white leghorn hens were vaccinated twice with a Mycoplasma gallisepticum (MG) bacterin, once with bacterin, or left unvaccinated. Four weeks after vaccination, they were challenged with virulent R strain MG. Egg production was significantly higher in challenged vaccinated groups than in the challenged control group. Four challenged control hens went out of production, whereas only one twice-vaccinated hen did. MG was first isolated directly from eggs 5 days postchallenge (PC) in twice-vaccinated hens, 4 days PC in once-vaccinated hens, and 2 days PC in controls, and the hens continued to lay positive eggs till the end of the experiment 7 weeks PC. MG was found in 17.65%, 38.55%, and 45.90% of eggs cultured in twice-vaccinated, once-vaccinated, and control groups, respectively. Nine of 16 twice-vaccinated hens were found to be shedding MG through their eggs, whereas 15 of 17 once-vaccinated hens and 14 of 16 controls were shedding MG through their eggs.     

The effects of ts-11 strain Mycoplasma gallisepticum vaccination in commercial layers on egg production and selected egg quality parameters

Live Mycoplasma gallisepticum (MG) vaccines have been USDA approved and licensed for use in commercial layer chickens since 1988; however, egg production and egg quality data exist only for the F strain of MG. Information pertinent to the effects of ts-11 MG on egg and eggshell quality parameters, as well as egg size distribution, is lacking. In this study, pullets were inoculated at 10 wk of age with ts-11 strain MG and placed in biological isolation units at 10 birds/unit. Hen-day egg production, eggshell strength, Haugh unit score, pimpling incidence, and blood/meat spot incidence were monitored and recorded in each trial through a 45-wk production cycle. Further, eggs from all treatments were collected daily, Monday-Thursday, and individually weighed. Results of this study indicate that no significant difference was observed between the treatments for the parameters measured or for egg size distribution. Therefore, these data should lessen producers' concerns pertaining to the impact of ts-11 strain MG on egg production, egg and eggshell quality parameters, and egg size distribution.     

F strain Mycoplasma gallisepticum vaccination of post-production-peak commercial Leghorns and its effect on egg and eggshell quality

Forty-five-week-old commercial leghorns negative for antibodies to Mycoplasma gallisepticum (MG) and M. synoviae were vaccinated with high-passage F strain MG (FMG). Hens were confined in modified Horsfall-Bauer isolation units through 60 weeks of age. Egg production (% hen day) and parameters of egg and eggshell quality were monitored, including egg weight, eggshell strength, Haugh unit score, pimpling, and blood/meat spot incidence. Egg production was significantly lower (P less than 0.05) for FMG vaccinates than controls (down 5.76% and 5.80% in Trials 1 and 2, respectively). However, vaccinates and controls did not differ significantly in eggshell strength, shell thickness, pimpling, or blood/meat spot incidence. Haugh unit scores were significantly (P less than 0.05) greater for FMG vaccinates. At necropsy, all reproductive tracts appeared grossly normal. These studies suggest that high-passage FMG vaccination of post-production-peak hens does not adversely affect oviduct function.     

Temperature sensitivity studies on selected strains on Mycoplasma gallisepticum.

Mycoplasma gallisepticum (MG324), a tylosin resistant strain of low virulence, was compared with four other strains with respect to their survival at temperatures from 46.1 to 48.9 degrees C. MG324 was found to be more resistant than the other strains tested.     

Effects of increased dosages of the Mycoplasma gallisepticum vaccine MYCOVAC-L in layer chickens subsequently challenged with virulent M. gallisepticum: egg production and serologic response

Ten-week-old Hy-Line Commercial W-36 pullets were spray-vaccinated with MYCOVAC-L at the manufacturer's recommended dosage (1x) or at 15 times that rate (15x). At 22 or 45 wk of age, subsets of 1x- and 15x-vaccinated pullets were challenged with the virulent Mycoplasma gallisepticum (MG) strain Rlow. Percent hen-day egg production was determined through week 55. Analyses for treatment effects on overall (22-56 wk) percent hen-day egg production revealed no significant differences between nonchallenged 1x and nonchallenged 15x MYCOVAC-L treatments. Among 1x MYCOVAC-L-vaccinated groups, Rlow challenge at 45 wk corresponded to significantly (P < or = 0.01) lower overall egg production compared with the unchallenged 1x-vaccinated control (70.88% vs. 79.15%, respectively). Conversely, at the 15x MYCOVAC-L dosage level, overall egg production was not significantly affected by virulent MG challenge at 45 wk compared with its unchallenged counterpart (84.09% vs. 81.03%, respectively) and could indicate increased protection from virulent MG challenge. Serologic monitoring indicated the virulent MG challenge was consistently (100%) associated with seroconversion. Comparisons among the nonchallenged experimental treatments indicated that vaccinations at the 15x MYCOVAC-L dosage rate were associated with a greater seroconversion rate at weeks 21, 27, and 44, but not at week 50.     

罗红霉素对鸡霉形体病的药效观察

罗红霉素 (Roxithromycin)为十四元环的半合成新大环内酯类抗生素 ,抗菌谱较广 ,对多数革兰氏阳性菌 (如金葡菌、链球菌等 )、部分革兰氏阴性菌敏感 ,对某些厌氧菌及支原体、衣原体亦有较强的抗微生物作用[1] 。罗红霉素与红霉素有相似的抗菌谱和不完全的交叉耐药性 ,其优点是提高了对酸的稳定性 ,同时显著改善了药动学性质 ,如半衰期延长 ,能迅速经胃肠道吸收 ,具有较高的血药浓度 ,能广泛分布于全身各组织及体液中 ,其血药峰浓度及生物利用度是大环内酯类中相对最高者 [2～ 4 ] 。医学上主要用于呼吸道、泌尿道及皮肤软组织感染 [2 ]。国…     

Bacterin to control the vertical transmission of Mycoplasma gallisepticum in chickens

A Mycoplasma gallisepticum bacterin was prepared and used in Mycoplasma gallisepticum (MG)-positive primary breeders to control vertical transmission of MG. Two generations were vaccinated, but the third generation was not vaccinated and was monitored serologically. Results showed no evidence of MG at 1 day, 6 weeks, 11 weeks, 16 weeks, or 31 weeks of age. This procedure may offer small breeder organizations and showbird fanciers a way to eliminate MG.     

Further studies on the immunization of chickens with temperature-sensitive Mycoplasma gallisepticum mutant

Newly hatched chickens were immunized with a temperature-sensitive (TS) Mycoplasma gallisepticum (MG) mutant (TS 100). Immunized chickens resisted challenge with the virulent S6 strain. The dose of TS MG needed for protection was less than 3.3 X 10(4) colony-forming units. After immunization with TS 100, chickens were subjected to a variety of virus infection and immunosuppressive treatments. Neonatal bursectomy or thymectomy, infectious bursal disease virus infection, and infectious bronchitis virus vaccination or a combination of infectious bronchitis virus and Newcastle disease virus vaccination did not contribute to the development of air-sac lesions in TS MG-immunized chickens. Infectious bronchitis virus vaccination enabled MG to migrate from the nasal cavity to the trachea but not to the air sacs. The TS MG vaccine appears to be a safe immunogen.     

北京市鸡毒支原体和滑液囊支原体血清学调查

为了解北京市鸡毒支原体(Mycoplasma galliscepticum,MG)和滑液囊支原体(Mycoplasma synoviae,MS)感染情况,2019年从北京市10个区127个养鸡场(户),采集3 910份鸡血清样品,采用酶联免疫吸附试验(ELISA)进行MG和MS感染抗体检测。结果显示:北京市10个区均有不同程度的MG和MS感染,场群阳性率分别介于78.95%～100%、68.42%～100%,样品阳性率分别介于59.35%～93.13%、50.0%～94.53%,平均场群阳性率分别为89.0%和86.6%,平均样品阳性率分别为79.0%和75.6%;第三季度的场群阳性率和第二季度的样品阳性率最高,第四季度场群阳性率和样品阳性率最低(P0.01);110～180日龄的MG样品阳性率、251～320日龄的MS样品阳性率最高,462日龄以上均最低(P0.01);规模化商品鸡场的MG和MS场群阳性率和样品阳性率均最高(P0.01);蛋鸡的MG和MS样品阳性率均高于肉鸡(P0.01)。结果表明,北京市MG和MS感染较为严重,第二、三季度高发,110～320日龄鸡群、规模化商品鸡场和蛋鸡群感染尤其严重。结果提示,应采取包括加强生物安全管理、种鸡净化、疫苗预防和药物治疗在内的综合管理措施,有效控制该地区MG、MS的流行。     

Strain differentiating real-time PCR for Mycoplasma gallisepticum live vaccine evaluation studies

Mycoplasma gallisepticum causes respiratory disease and production losses in poultry. Vaccination of poultry with M. gallisepticum live vaccines is an approach to reduce susceptibility to infection and to prevent the economic losses. The development and evaluation of live vaccines usually requires the involvement of several vaccine and challenge strains in the same experimental setup. Our goal was to develop a tool to allow the differentiation between a set of known M. gallisepticum strains in a quantitative manner. We developed 5 real-time PCR assays that absolutely differentiated between one of the five commercial and laboratory vaccine strains: F, ts-11, 6/85, K5831, K5054, and the challenge strain R low when tested on in vitro cultures. The assay K5831 vs. R low was also tested on specimens from live birds that were vaccinated with K5831 and challenged with R low, and successfully differentiated between the vaccine and the challenge strains in a quantitative manner. This preliminary in vivo application of the method also shed light on possible protection mechanisms for the M. gallisepticum K5831 vaccine strain.     

Scanning electron microscopic studies of Mycoplasma gallisepticum infection in embryonic tracheae

Mycoplasma gallisepticum (MG) was used to infect chicken embryos, and scanning electron microscopy was used to examine the morphologic changes in the tracheae. Tracheae harvested from embryos infected with MG for 5 days showed extensive deciliation, surface erosion, and inflammatory cell infiltration. Embryonic tracheal explants infected with MG for 6 hr showed the same deciliation and surface erosion. The damage to the tracheal surface caused by MG at the embryonic stage might play a role in the pathogenesis of MG infection.     

Virulence and transmissibility of Mycoplasma gallisepticum

The virulence of 4 low passage strains of Mycoplasma gallisepticum obtained from different sources within Australia was studied by experimental infection of chickens. Strain Ap3AS, originally isolated from the air sac of a broiler chicken, produced severe air sac lesions following injection into the abdominal air sacs of 2-week or 3-week-old chickens, and adult hens. Strain 80083 which was isolated from a clinically normal broiler breeder hen was also capable of producing gross air sac lesions following intra-abdominal (IA) injection, although it did so less consistently than strain Ap3AS. Strain 82078 isolated from a layer hen and strain QXO which was isolated from a turkey were also moderately pathogenic in terms of the incidence and severity of lesions elicited following IA injection. Strains Ap3AS and 80083 both caused a substantial loss of egg production over a 5 week period after IA infection of 27-week-old hens. Neither strain Ap3AS nor 80083 caused gross lesions or loss of egg production when administered alone into the upper respiratory tract. However, when inoculated into the conjunctival sac in combination with the Vic S strain of infectious bronchitis virus (IBV) strains Ap3AS and 80083 produced identical clinical signs of conjunctivitis. The mean numbers of M. gallisepticum in tracheal washings were significantly higher 2 weeks after infection in the group receiving strain 80083 in combination with IBV than in the group infected with strain Ap3AS and IBV (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ultrastructural features of Mycoplasma gallisepticum in tracheal explants under transmission and stereoscan electron microscopy

Ultrastructural features of Mycoplasma gallisepticum in tracheal explants were examined using the transmission and stereoscan electron microscope. The organisms were characteristically cocco-bacilliform except when in close contact with the host cells when they assumed an elongated and irregular form characteristically terminating in a bleb which was often embedded in the cell surface. In such organisms there were peripherally aligned fibrillar structures oriented towards the bleb which may have a functional relationship with a probing or moving habit of the mycoplasma.     

Genetic and antigenic relatedness between Mycoplasma gallisepticum and Mycoplasma synoviae

The two avian pathogens Mycoplasma gallisepticum and Mycoplasma synoviae were found, by Southern blot hybridization of their digested DNAs, to share genomic nucleotide sequences additional to those of the highly conserved ribosomal RNA genes. The assumption that some of the shared sequences encode for antigens or epitopes common to both mycoplasmas was supported by Western immunoblot analysis of cell proteins of one mycoplasma with specific antiserum to the other mycoplasma. Interestingly, the band patterns of reactive antigens were different for some of the M. gallisepticum strains, supporting the concept that the species is genotypically variable. The results of the present study may explain the cross-reactivity of the two mycoplasmas noted previously in a variety of routine serological tests.     

Mycoplasma gallisepticum vaccination-challenge: an egg-production model.

Specific-pathogen-free layer hens in maximum lay were exposed by aerosol to a broth culture of Mycoplasma gallisepticum R' strain. Egg-production loss of greater than 50% was evident 7-14 days following challenge of unvaccinated chickens, with a gradual recovery during the next several days. Various vaccine preparations were tested to determine the effect in the model. All vaccinated chickens exhibited significantly (P < or = 0.05) lower egg-production loss than the unvaccinated controls. The model provides a method for testing treatment effects on egg-production losses resulting from controlled exposure to M. gallisepticum and may be useful in simulating field exposure.     

Egg production, egg weight, eggshell strength, and mortality in three strains of commercial layers vaccinated with F strain Mycoplasma gallisepticum

Three strains of commercial leghorns vaccinated at 17 to 22 weeks of age with F strain Mycoplasma gallisepticum (MG) were maintained through 117 weeks of age. The three strains differed in both mortality and percent egg production per hen housed; however, the strains did not differ in egg weight (EW), eggshell strength (ESS), or percent daily egg production. Results of this study indicate EW and ESS for F strain MG-vaccinated hens follow patterns previously reported for uninfected layers. Further, mortality may account, in part, for differences in percent egg production per hen housed between strains of F strain MG-vaccinated hens.