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1.
Pathogenicity of Mycoplasma synoviae (MS) was examined in specific-pathogen-free (SPF) white leghorn chicken embryos. Six isolates of MS were inoculated into 7-day embryos via the yolk sac. Isolates were evaluated for gross and microscopic lesions through 19 days' incubation and for embryo lethality through 20 days' incubation. Isolates in decreasing order of lethality, from lowest to highest 50% embryo lethal dose, were WVU 1853, K1968, K1858, FMT, 92D8034, and F10-2AS. Embryo lethality was consistent with lesion incidence and severity. Embryo lethality did not correlate with previous results regarding pathogenicity of these same six isolates in SPF broiler chickens. 相似文献
2.
Eleven strains of the avian pathogen Mycoplasma synoviae were evaluated for the presence of sialidase activity with the use of the fluorogenic substrate 2'-(4-methylumbelliferyl)-alpha-D-N-acetylneuraminic acid and the sialidase inhibitor 2-deoxy-2,3- didehydro-N-acetylneuraminic acid. The kinetics of in vitro growth in modified Frey medium were also assessed for each strain. Five strains had been isolated from clinically symptomatic chickens, and strains WVU 1853T and K3344 have been demonstrated to be capable of reproducing disease in specific-pathogen-free chickens. All strains exhibited sialidase activity, although the amount varied 65-fold among strains (P < 0.0001) from 1.3 x 10(-7) to 2.0 x 10(-9) activity units per colony-forming unit. Strains originally isolated from clinically symptomatic birds had more (P < 0.05) sialidase activity than strains from asymptomatic birds. Strain WVU1853T exhibited the most sialidase activity (P < 0.0001) and grew to the highest culture density (P < 0.0001) among strains, but across strains, the rank correlation of growth rate with sialidase activity was not significant. Negligible activity was detected in conditioned culture supernatant fluid. This is the first report of sialidase activity in pathogenic strains of M. synoviae, which suggests a potential enzymatic basis for virulence of the organism. 相似文献
3.
S B Lockaby F J Hoerr L H Lauerman B F Smith A M Samoylov M A Toivio-Kinnucan S H Kleven 《Avian diseases》1999,43(2):251-261
Virulence mechanisms of six isolates of Mycoplasma synoviae (MS), previously classified as pathogenic (K1968), moderately pathogenic (WVU 1853, K1858, 92D8034, and F10-2AS), and mildly pathogenic (FMT) in chickens, were examined. The most virulent isolate, K1968, had been found to invade systematically and produce lesions following eye-drop inoculation. In the present study, all isolates were evaluated for presence of a possible cytadhesin and for functional attachment to host cells as indicated by hemagglutination and hemadsorption. Three representative isolates, K1968, 92D8034, and FMT, were evaluated for attachment and colonization in cultured chick tracheal rings and tendon cell monolayers by direct transmission electron microscopic examination and by quantitative polymerase chain reaction assay. Ciliostasis was compared in tracheal organ culture. Previously found differences in pathogenicity of these isolates for chickens could not be explained as differences in attachment and were only partially explained by differences in colonization. Pathogenicity of the most virulent isolate of MS was suspected to be multifactorial, involving attachment and colonization of the upper respiratory tract plus additional unidentified factors associated with systemic invasion and lesion production. 相似文献
4.
Two experiments were conducted to evaluate the virulence and vaccination efficacy of a Mycoplasma gallisepticum (MG) isolate designated MG Intervet 6/85. Virulence of the strain was determined by evaluation of airsacculitis scores following aerosol exposure to the isolate before and after 10 sequential passes in either commercial broiler chickens or commercial turkeys. Two-week-old specific-pathogen-free chickens were vaccinated by aerosol exposure. The birds were challenged with the R' strain of MG at either 4 or 8 weeks post-vaccination. Efficacy was evaluated by airsacculitis scores determined 21 days after challenge. Ten repetitive back-passes of the isolate in chickens and turkeys did not substantially increase the virulence. Virulence for both chickens and turkeys was minimal, while protection elicited by aerosol vaccination in young chickens against virulent R' strain was significant (P less than or equal to 0.05) compared with unvaccinated controls. 相似文献
5.
A vaccine for necrotic enteritis (NE) of chickens would reduce the current need to prevent or treat the disease in broiler chickens with antimicrobial drugs. The objective of this study was to understand aspects of immunity to the disease. The first experiment examined the virulence of six strains of Clostridium perfringens isolated from cases of NE in broiler chickens. Using a 5-day experimental oral infection of 2-week-old broiler chickens, four of the six strains were found to be virulent. Pulsed-field gel electrophoresis and PCR showed that virulence was not associated with a plasmid encoding the beta2 toxin gene, cpb2, since this was present in virulent and one of the two avirulent strains. In the second experiment, two virulent and one avirulent strains were tested for their ability to immunize ("infection-immunization") chickens through the oral route. The procedure used experimental infection for 5 days followed by bacitracin treatment for 9 days, and then re-challenge 2 days later with a virulent strain, CP4. Infection-immunization with the virulent isolates protected chickens from subsequent virulent challenge, whereas the infection-immunization with the avirulent isolate did not. In a third experiment, two of four alpha-toxin-negative mutants of CP4 protected birds from experimental NE after oral immunization. These two mutants were also attenuated for virulence. We conclude that it is possible to immunize chickens successfully against NE and that immunogen(s) other than alpha-toxin are important in protective immunity against oral infection. 相似文献
6.
A model system was used to study infectious bronchitis virus (IBV) and Mycoplasma synoviae (MS) interaction. The system involved exposure of chickens to IBV, followed by exposure to MS 2-5 days later. The chickens were subjected to a cold environment (10 +/- 2 C) for 3 weeks starting one day before MS exposure. Under these conditions, differences in the capacity of various strains of IBV to exacerbate MS airsacculitis was demonstrated. Exposure to IBV field isolates generally resulted in more air-sac lesions than did higher-egg-passaged laboratory strains and vaccine strains. Use of lower-egg-passaged vaccines resulted in a higher incidence of airsacculitis than did higher-egg-passaged vaccines. When chickens were IBV-vaccinated before being used in the model system, the incidence of airsacculitis was lowered, even though the chickens became infected by the challenge virus. Vaccination of MS-free chickens with IBV had no effect on airsacculitis incidence when MS exposure occurred after the vaccine reaction was past. 相似文献
7.
Recombinant DNA probes for Mycoplasma synoviae 总被引：1，自引：0，他引：1
A genomic library was prepared from Mycoplasma synoviae (MS) strain WVU 1853 cloned in plasmid vector pUC8 and transformed in Escherichia coli host JM83. In dot blot assays, four transformed E. coli clones hybridized with 32P-labeled chromosomal DNA of MS but not with 32P-labeled chromosomal DNA of M. gallisepticum (MG) strain S6. In Southern hybridization, each of the CsCl-purified recombinant plasmid clones was shown to contain two MS DNA fragments between 1.0 to 2.3 kbp in length. 32P-Labeled probes prepared from each of the four recombinant plasmids hybridized in dot blot assays with MS strain WVU 1853 and nine MS field isolates but not with MG strains S6, K810, F2F10, four MG field isolates, and 15 other species of avian mycoplasmas. 相似文献
8.
Systemic Mycoplasma synoviae (MS) infection was induced experimentally in commercial turkeys with recent MS isolates (K4822D and K4774J) from turkey breeder flocks that exhibited no clinical signs typical of MS infection except for a low incidence of swollen footpads. The virulence of each strain was compared by evaluating gross and microscopic lesions, serologic responses, and MS isolation rates at 10 and 21 days postchallenge and by comparing these results with those obtained from a known virulent isolate (K1968), another previously characterized field isolate (K4463B), and unchallenged controls. All strains induced lesions typical of infectious synovitis but showed distinct differences in the extent of the gross and microscopic lesions and in the isolation rates from the tissues in turkeys. K1968 induced the most extensive lesions in hock and stifle joints and footpads, but strains K4822D, K4774J, and K4463B all induced synovitis and were similar in virulence for synovial tissues. Very mild respiratory lesions were induced by all of the strains studied. All strains yielded strong positive serologic responses. We concluded that these recent field isolates, although able to induce synovitis, are less virulent for turkeys than a known virulent strain. Nevertheless, under severe experimental challenge, these strains have the capability of causing lesions that may be incompatible with economical turkey production. 相似文献
9.
The relative virulence for chickens of five strains of Pasteurella multocida was evaluated. Twenty groups, each of ten chickens, were inoculated with a standard dose of 10(5) of each of five strains by the intramuscular (I.m.), intravenous (I.v.), intratracheal (I.tr.) or conjunctival (Co) routes. The highest mortality occurred in the groups dosed I.m. and I.v., followed by I.tr. inoculation. The relative virulence of each strain did not change when inoculated by the different routes. The most virulent strain, VP161, caused 100% mortality by all except the Co route. The least virulent strain, VP17, caused a single mortality by the I.v. route, but gave a high level of protection to birds inoculated by both the I.m. and I.v. routes, when challenged by intramuscular injection with (VP161). There was no protection against I.m. challenge in the birds inoculated by the I.tr. or Co routes. Serum antibody levels measured by ELISA correlated with the level of protection against virulent challenge for groups inoculated I.m. or I.v., but not I.tr. Western blots of pooled sera from each group did not show any specific antigen recognition that might explain the observed differences in protection. Inoculation with strain VP17, (both I.m. and I.tr.) also gave a high level of protection to birds challenged with strain VP161 by intratracheal instillation. 相似文献
10.
Someya A Otsuki K Murase T 《The Journal of veterinary medical science / the Japanese Society of Veterinary Science》2007,69(10):1009-1014
The present study reports colibacillosis of layer chickens in a commercial egg-producing farm in western Japan. Three flocks of chicken at 18-21 weeks of age were affected during the initiation of egg lay. Postmortem examination revealed pericarditis, perihepatitis, airsacculitis, subcutaneous inguinal lesion, and injured cloaca. Escherichia coli was isolated from the lesions of the affected birds. Twenty-two of 26 E. coli isolates (84.6%) obtained from 18 birds in the 3 flocks showed pulsed-field gel electrophoresis (PFGE) patterns that were considered to be closely associated to each other and arbitrarily designated as pattern A. All the 22 isolates with the PFGE pattern A harbored the putative virulence genes, astA, iss, iucD, tsh, and cva/cvi. Additional 2 PFGE patterns (B and C) were also found in E. coli isolates obtained from the affected flocks and had the putative virulence genes in combinations different from those in the pattern A strains. The results suggested that certain E. coli virulence genes and host factors, such as initiation of egg lay may be associated with occurrence of colibacillosis. 相似文献
11.
In this study, we assessed the pathogenic potential of Escherichia coli associated with a commercial competitive exclusion (CE) product by examining the phenotypic characteristics associated with E. coli virulent for humans and domestic animals. Most E. coli isolates were capable of proliferating in iron-deplete chicken sera. Interestingly, none of the E. coli isolates from the commercial CE product contained the bacterial adhesin Tsh characteristic of avian pathogenic E. coli associated with airsacculitis and colisepticemia. In terms of virulence potential for humans, most E. coli isolates (78%) were sensitive to killing by 12.5% human sera. Because of their sensitivity to human sera, the E. coli in the CE product are not likely to cause a serious systemic infection in humans and, therefore, do not present a risk of causing septicemia in humans. Because these isolates also lack the gene tsh, they are also less likely to cause systemic disease or airsacculitis in poultry than pathogenic strains commonly isolated from diseased birds. 相似文献
12.
The live attenuated temperature-sensitive (ts+) Mycoplasma synovia (MS) strain, MS-H, is used as a vaccine in a number of countries to control virulent MS infection in commercial chicken flocks. Nine out of 50 isolates made from flocks vaccinated with MS-H were found to have lost the ts+ phenotype of the original vaccine strain. In order to examine the influence of the ts- phenotype on virulence of the isolates, four of the ts- isolates, the MS-H vaccine, and the vaccine parent strain 86079/7NS were administered by aerosol in conjunction with infectious bronchitis virus to 3-wk-old specific-pathogen-free chickens. The four ts- clones induced only minimal air sac lesions that were not different in severity from those caused by MS-H vaccine; however, the vaccine parent strain 86079/7NS caused air sac lesions that were significantly greater than those of MS-H and all ts- clones. The vaccine parent strain 86079/7NS and two of the ts- clones were recovered from the air sacs of the respectively infected chickens whereas the MS-H vaccine and two other ts- clones were not. Three of the ts- isolates caused increased tracheal mucosal thicknesses that were significantly greater than those from birds inoculated with MS-H, and one caused increased tracheal mucosal thicknesses that were significantly less than those from birds inoculated with 86079/7NS. In conclusion, unlike the MS-H vaccine, the MS-H ts- clones were associated with minor changes in tracheal mucosa; however, unlike the vaccine parent strain, they did not induce lesions in the air sacs. These results suggest that factors other than ts+ phenotype are involved in the attenuation of the MS-H vaccine. 相似文献
13.
Groups of eight chickens were challenged with 10-fold dilutions of one of two strains of Mycoplasma synoviae (MS); each challenge group contained two noninfected sentinels. Both strains were highly efficient in colonizing the respiratory tract with challenge doses as low as 76 and 24 color-changing units/bird. Infection spread rapidly (within 7 days) to sentinels, while uninfected control chickens separated from infected chickens by two empty pens remained uninfected for the 56-day experimental period. Although sentinels and birds challenged with the lowest doses had weaker or slightly slower antibody responses in some cases as measured by serum plate agglutination, enzyme-linked immunosorbent assay (ELISA), and hemagglutination inhibition (HI), they generally exhibited a typical antibody response. Agglutination reactions tended to be weak, but a high percentage of tests (generally >30% from day 14 postchallenge) were positive. ELISA results were variable, and in some cases reactor rates were low (generally <20%), even though the chickens were colonized in the upper respiratory tract. The HI test was reliable in detecting infected groups; usually >50% were positive from 14 days postchallenge. Mean HI titers were higher when using hemagglutination antigens prepared from the homologous MS strain as compared with antigen prepared from the heterologous strain or with standard antigen prepared from WVU 1853. 相似文献
14.
为了解鸡滑液囊支原体(MS)在川西地区的感染情况,本研究采集15个肉鸡场疑似MS感染的病鸡咽拭子、跗关节和胸部滑液囊样本共75份,对经PCR检测为阳性的样本进行MS分离,并对分离株的主要生物学特性进行研究,以及对分离株的VlhA基因进行遗传进化分析。结果显示,75份样本MS PCR阳性检出率为41.33%(31/75),11个鸡场感染该病,场阳性率为73.33%(11/15);但仅从其中3个鸡场分离到9株MS,分离株菌落与菌体形态与已知MS培养特性相符,各分离株培养浓度为10~4CCU/mL^10~6CCU/mL,分离株以5×10~5CCU接种7日龄SPF鸡胚,鸡胚于接种后7 d^9 d死亡,且分离回收到接种菌株;9株MS分离株VlhA基因的同源性为86.1%~99.9%,与参考株同源性为86.2%~95.4%,其中分离自同一鸡场的7株MS VlhA基因同源性为96.4%~99.9%;分离株VlhA基因遗传进化分析显示,其中分离自两个不同鸡场的两株MS与国内流行株的亲缘关系最近,而分离自另一鸡场的7株MS与中东地区分离的3株MS亲缘关系较近,表明MS在川西地区肉鸡场呈高感染率,MS VlhA基因变异较大。本研究为川西地区MS的进一步研究提供了基础材料和科学依据。 相似文献
15.
Mycoplasma synoviae (MS) was isolated from the brains of 22-week-old commercial meat turkeys displaying severe synovitis and infrequent central nervous system signs. Histological examination of the brains revealed mild-to-severe meningeal vasculitis. The vasculitis ranged from fibrinoid necrosis with little inflammation to a marked infiltration of lymphocytes and plasma cells disrupting the architecture of the vessel wall, accumulating as perivascular cuffs, and involving surrounding meninges. Occasional arteries were undergoing thrombosis. Similar lesions were occasionally seen in renal, synovial, and splenic vessels. MS isolates from the brain, trachea, and joint showed similar protein-banding patterns by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. However, the protein profile differed markedly from the standard MS reference strain, WVU 1853. This is the first known field case of MS isolation from the brains of turkeys. 相似文献
16.
A total of 100 poultry farms in northern and middle areas of Jordan were sampled to investigate the bacteria associated with airsacculitis in broiler chickens. Of 170 bacterial isolates, 88.2% were identified as Escherichia coli, 8.8% as Ornithobacterium rhinotracheale, and 3% as Bordetella avium. Fourteen serotypes of E. coli were identified among 66 typeable isolates and the remainder were untypeable. The most prevalent serotypes were O1, O8, and O78. The main serotype of O. rhinotracheale was serotype A. Experimental inoculation of O. rhinotracheale via intravenous, intratracheal, and intra-air sac routes resulted in growth retardation, thickening in the air sacs, arthritis, and liver necrosis. Reisolation of O. rhinotracheale from the air sacs, liver, trachea, heart, and spleen at day 7 postinoculation confirmed its role. In vitro susceptibility testing revealed that E. coli isolates were sensitive to gentamicin and colistin, O. rhinotracheale to tetracyline, and B. avium to most of the nine antibiotics examined. 相似文献
17.
Kidney lesions associated with mortality in chickens inoculated with waterfowl influenza viruses 总被引：7，自引：0，他引：7
R D Slemons L N Locke M G Sheerar R M Duncan V S Hinshaw B C Easterday 《Avian diseases》1990,34(1):120-128
Seventy-six type A influenza viruses recovered from waterfowl in Wisconsin, California, South Dakota, Florida, Texas, Alabama, and Nebraska were tested for virulence in chickens. The challenge to chickens was intravenous inoculation of first-, second-, or third-egg-passage virus. Each of the virus strains was tested separately in three or four chickens. Eighteen of the 76 viruses caused the death of one or more chickens following inoculation. Postmortem lesions were similar in all dead birds. In decreasing order of frequency, gross lesions included: swollen kidneys evident as accentuated lobular patterns, urates in the pericardial sac, and urates on the surface of the liver. Microscopic lesions present in kidneys were consistent with visceral gout. Mortality was associated with inoculations having higher concentrations of infectious virus. These results indicate that the influenza A viruses circulating in duck populations may include strains potentially pathogenic for chickens. 相似文献
18.
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) 相似文献
19.
Serial passage of two infectious bronchitis virus (IBV) vaccine strains in chickens enhanced their capacity to increase the incidence and severity of Mycoplasma synoviae (MS) airsacculitis. Included in this report were the mild Massachusetts-type Connaught strain and the Arkansas 99 vaccine strain of IBV. The Connaught strain and one of two Ark 99 vaccine strains passaged in chickens increased the incidence of airsacculitis markedly compared with nonpassaged virus. The other Ark 99 vaccine virus already exacerbated MS airsacculitis, before passage in chickens, and its influence did not increase on passage. All IBV strains studied to date have either possessed this trait or reacquired it on passage in the natural host. 相似文献
20.
Three fowl adenovirus (FAV) isolates (341, 344, and 215) obtained during 1996-97 from field outbreaks of inclusion body hepatitis/hydropericardium syndrome (IBH/HPS) affecting broilers and broiler breeders in Chile were characterized by virus neutralization tests (VNTs) and restriction enzyme analysis of a DNA fragment. Furthermore, the pathologic characteristics of one of these FAV isolates (FAV 341) was studied in experimentally infected chickens. The VNTs conducted with isolates 341 and 344 against reference strains and antisera belonging to each of 12 FAV serotypes demonstrated a close antigenic relationship with strain KR5 of the FAV serotype 4. Polymerase chain reaction using the primers H3/H4 and subsequent HpaII digestion was used for serotype identification of isolates 341 and 215. The length of the PCR products and the restriction profiles of isolates 341, 215, and the reference strain KR5 (FAV4) were identical. The present results confirmed the classification of all three isolates as FAV4. The pathogenicity test with 1000 mean tissue infectious dose of isolate 341 inoculated intramuscularly in 20-day-old specific-pathogen-free chickens resulted in the death of 9% (two birds) six days postinoculation (PI). Both birds showed characteristic IBH/HPS gross and microscopic lesions; the remaining birds, sacrificed at day 10 PI, showed less severe lesions. On the basis of epidemiologic and experimental data of the virulence of Chilean FAV isolates, and the pathogenicity results with isolate 341, we speculate that Chilean FAV strains may require an association with other agents (immunosuppressive agents) to induce IBH/HPS outbreaks in the field. 相似文献