THE PATHOGENESIS OF INFECTIOUS AVIAN ENCEPHALOMYELITIS

Normal chickens given infectious avian encephalomyelitis virus (IAEV) orally at 1, 7 or 14 days of age developed infectious avian encephalomyelitis (IAE), whereas those dosed with the virus at 21, 28 and 35 days of age did not. Chickens in all of these age groups that had been treated with cyclophosphamide or testosterone developed clinical IAE. Intraperitoneal inoculation of IAEV immunoglobulin at the time of dosing with the virus, or 48 hours later, protected normal and immunosuppressed chickens against the onset of clinical IAE. The titre of IAEV serum neutralising antibody was found to be lower in normal chickens given the virus at 1, 7 and 14 days of age in older chickens. These results suggest a significant role for the humoral immune system in the pathogenesis of IAE and in the development of immunity to the disease.     

THE PATHOGENESIS OF INFECTIOUS AVIAN ENCEPHALOMYELITIS

Infectious avian encephalomyelitis virus (IAEV) maternal antibody was detected in the serum of chickens for up to 21 days following hatching. This antibody protected chickens against clinical IAE after intracerebral inoculation with van Roekel strain or oral administration of the NSW-1 strain of IAEV. Maternal antibody to IAEV also protected testosterone bursectomised chickens against the development of clinical disease. IAEV maternal antibody also influeced the pattern of virus excretion in faeces and serological responsiveness. This influence on antibody responses persisted beyond the time that IAEV maternal antibody could be detected. The importance of IAEV maternal antibody on the strategy of vaccination against IAE is discussed.     

THE PATHOGENESIS OF INFECTIOUS AVIAN ENCEPHALOMYELITIS

The age of the chicken at the time of infection with infectious avian encephalomyelitis virus (IAEV) and the route of the administration of the virus had a marked effect on the development of the clinical disease. Chickens given the virus by intramuscular, intraperitoneal and oral routes exhibited a decreased susceptibility to development of clinical disease with increasing age. Irrespective of age, chickens were consistently susceptible to intracerebral inoculation of IAEV. Chickens infected with the virus at 1-, 7- and 14-days of age developed lower neutralising antibody titres to IAEV than chickens infected at 21 and 28 days. A relationship between the ability to produce specific neutralising antibody to IAEV and susceptibility to the development of clinical disease is discussed.     

A long term observation of antibody status to chicken anaemia virus in individual chickens of breeder flocks

The antibody status to chicken anaemia virus (CAV) in four layer breeder flocks was evaluated. Sera were periodically collected from the same 17 to 20 individual chickens of each flock ranging in age from 10 to 63 weeks old. The neutralising and fluorescence antibody were detectable in individual chickens during the observation periods ranging from 13 to 44 weeks. A high prevalence of both neutralising and fluorescence antibodies was observed; however, the prevalence of fluorescence antibody in older chickens was lower than that of neutralising antibody. The geometric mean (GM) of neutralising antibody titres, after all the chickens examined had seroconverted in flocks 1, 2 and 4, ranged from 373·2 to 2940·6. In flock 1, the GM titre at 63 weeks old was significantly lower than that at 37 and 52 weeks old. In flock 4, the GM titre at 48 weeks old was significantly lower than that at 24 and 35 weeks old. In flock 2, the GM titre at more than 31 weeks old significantly increased compared with that at 25 weeks old; this tendency was not seen in the GM of the fluorescence antibody titres. The results indicate that immunity to CAV can last a long time in naturally infected individual chickens.     

鸡腺胃病变型传染性支气管炎病毒感染试验

本文采用腺胃病变型传染性支气管炎患病鸡的腺胃病料和H95株分离株尿囊液毒,对不同品种、不同日龄的易感鸡,采用不同的感染途径进行感染,对其增重、死亡等数据进行统计分析,结果表明:供试不同品种的鸡在不同的感染途径下,采用腺胃病料和鸡胚尿囊液毒分别感染,均可引起不同程度的感染发病,并出现和自然病例相同的症状和典型的病理变化。随日龄的增长,其易感率和死亡率呈下降趋势。从感染死亡鸡中可重新回收到相应的病毒,发病耐过的鸡可产生特异性抗体。     

云南省地方品种鸡群4种垂直传播病毒血清流行病学调查

为了解云南省地方品种鸡群中禽白血病病毒(ALV)、禽网状内皮组织增生症病毒(REV)、鸡传染性贫血病毒(CAV)和禽脑脊髓炎病毒(AEV)的感染情况,采用ELISA方法对云南省滇东、滇西、滇中、滇南和滇北5个区域8个地方品种鸡群的2295份血清样品进行了上述4种垂直传播病毒的抗体检测。结果显示:云南省8个地方品种鸡群中,ALV、REV、CAV和AEV平均抗体阳性率分别为27.02%、72.77%、98.47%和76.25%,二重、三重、四重感染率分别为32.90%、36.38%、15.90%;不同区域、不同品种鸡群中均存在上述4种病原的感染,抗体阳性率有一定差异,但无规律性。结果表明,云南省地方品种鸡群中4种垂直传播病毒感染率较高,流行面较广,且呈现严重的混合感染状态。结果提示:应重视这4种可垂直传播病原的流行控制,谨防因病毒混合感染导致重大疫病免疫失败;继续加强抗体检测,及时淘汰阳性鸡群,净化种群,同时定期进行疫苗污染监测,提升饲养管理水平,保障云南省地方鸡种质资源的安全健康发展。     

THE SUSCEPTIBILITY OF YOUNG AND NEWBORN CALVES TO BOVINE EPHEMERAL FEVER VIRUS

The pathogenicity of a field strain, 417, of bovine ephemeral fever (BEF) virus for newborn and young calves was investigated. Three colostrum-deprived newborn calves inoculated intravenously developed severe clinical disease and viraemia, and produced long-lasting neutralising antibody. The incubation period in these animals was 10 and 11 days, compared with 5 to 7 days for older calves. Two newborn calves which received colostrum from immune dams and 2 which received colostrum from non-immune dams failed to respond clinically to intravenous inoculation with strain 417. The neutralising antibody response of these calves was of short duration. Four calves, 7 to 8 weeks old and lacking detectable neutralising antibody to BEF virus, or having low levels of antibody, did not develop clinical disease when inoculated intravenously. Four calves 12 to 14 weeks of age and free of detectable neutralising antibody to BEF virus developed clinical disease when inoculated with strain 417.     

鸡传染性贫血病毒与马立克氏病病毒共感染SPF鸡群免疫抑制协同作用的研究

将鸡传染性贫血病毒（Chicken infectious anemia virus,CIAV or CAV）和马立克氏病病毒（Marek s dis-ease virus,MDV）人工单一和共同感染1日龄的SPF鸡,感染后分别于14、21、28、35日龄检测鸡体红细胞压积的变化,并检测鸡群疫苗免疫3周后的抗体反应,以探讨CAV与MDV共感染对鸡体的免疫抑制是否有协同作用。结果表明,在血液分析方面,CAV与MDV共感染组较病毒单一感染组与对照组差异极显著,共感染不仅加重了鸡群贫血现象,而且延长了贫血的病理症状;而在禽流感病毒（Avian influenza virus,AIV）H5/H9疫苗、新城疫病毒（Newcastle disease virus,NDV）疫苗和传染性法氏囊病毒（Infectious bursal disease virus,IBDV）疫苗免疫后3周的抗体检测中,CAV与MDV共感染组较其它各实验组差异极显著,抗体滴度大大低于其它实验组;此外,CAV与MDV共感染组,鸡体生长状况明显差于实验各组,有6只鸡只死亡（6/25）,比病毒单一感染时的死亡率大大增加。综上研究证明,CAV与MDV共感染在免疫抑制作用上有协同作用。     

A CELL CULTURE VACCINE AGAINST BOVINE EPHEMERAL FEVER

SUMMARY A vaccine was prepared from cell culture fluids harvested from the twelfth passage of the 919 strain of bovine ephemeral fever (BEF) virus in Vero cell cultures. Cattle were vaccinated subcutaneously with various combinations of strain 919 virus and adjuvants. Neutralising antibodies were assayed at various times after vaccination and some cattle were challenged by intravenous inoculation with the virulent 417WBC strain of BEF virus. Strain 919 virus of the third and twelfth passage levels in Vero cells produced neither fever, clinical illness nor detectable viraemia in 5 calves inoculated intravenously. Nor could viraemia be detected in 5 heifers receiving vaccine subcutaneously. When the vaccine was administered mixed with aluminium hydroxide adjuvant, the production of neutralising antibodies increased with an increase in the volume of vaccine from 2.5 ml to 10 ml and the response to 2 injections was significantly better than the response to a single injection. The neutralising antibody response was decreased when vaccine was diluted in phosphate buffered saline. The neutralising antibody response following 2 subcutaneous vaccinations with strain 919 virus mixed with aluminium hydroxide adjuvant was higher than that following intravenous inoculation with virulent virus. The vaccine-induced antibodies persisted for at least 12 months, and revaccination at this time led to an increase in the titre of neutralising antibody. Antibodies induced by a single subcutaneous administration of strain 919 virus mixed with Freund's complete adjuvant persisted for at least 40 weeks; those induced by vaccine containing Freund's incomplete adjuvant had virtually disappeared within 16 weeks. All these calves responded to vaccination with aluminium hydroxide-containing vaccine with increases in levels of neutralising antibodies. Of 26 vaccinated calves challenged with virulent BEF virus, 24 remained clinically normal. Two developed brief periods of pyrexia on the seventh day after challenge, but no other clinical signs. One of these calves had a viraemia that was demonstrated only by intravenous inoculation of a susceptible calf. The remaining calf had no detectable viraemia. All of 7 unvaccinated calves developed severe clinical BEF within 5 days of challenge. No disease attributable to the 919 virus occurred in 24 vaccinated pregnant heifers or their newborn calves.     

Clinical effects, virological and serological responses in chickens following in-ovo inoculation of reticuloendotheliosis virus

Six-day-old embryonated specific pathogen free chicken eggs were inoculated with reticuloendotheliosis virus (REV) into the yolk sac and were incubated until they hatched. The hatchability of eggs inoculated with REV was significantly less (P less than 0.025) than that of media-inoculated controls. Although there were no significant differences in the body weights of these chickens at hatching, there were differences (P less than 0.001) at 6, 25 and 51 days of age between the infected and control chickens. Six of 10 chickens hatched from eggs inoculated with REV had feathering defects at 6 days of age. All chickens hatched from infected eggs had cell-free viraemia and antigenaemia, but not precipitating antibodies. Some of these chickens had very low neutralising antibody titres (less than 45) when examined at 25 and 37 days of age, as did all 10 chickens at 51 days of age. A low rate of horizontal transmission was indicated by the detection of antibodies at 37 and 51 days of age in chickens running in contact with the chickens hatched from eggs inoculated with REV.     

1株肾型鸡传染性支气管炎病毒的鉴定

鸡传染性支气管炎病毒(IBV)具有不同致病特性,将IBV XDC-2株接种9日龄SPF鸡胚培养,可引起鸡胚死亡和出现侏儒胚,病毒EID50达5×10-5.33/mL。将IBV XDC-2株接种18日龄SPF鸡,饲养观察14 d,病鸡临床症状表现为:精神沉郁,羽毛凌乱,双翅下垂,轻微腹泻,多数拉白色水样稀粪。病死鸡出现肾肿大、呈花斑状、大量尿酸盐沉积。鸡发病率为100%,死亡率为25%。死亡鸡肺脏、肾组织制作组织切片,发现病理变化明显,主要为:肾小管扩张,上皮细胞呈玻璃样变性,部分管腔内可见坏死脱落之上皮细胞,于肾间质可见大量单核细胞浸润,肾间质有充血、出血现象;肺内动脉、毛细血管充血,淋巴细胞浸润。死亡鸡肺脏、肾组织接种鸡胚分离病毒,RT-PCR检测结果为阳性,表明该分离株为鸡传染性支气管炎病毒,具有很强的嗜肾性。     

Viral tissue tropisms and interferon production in white leghorn chickens infected with two avian reovirus strains

Inoculation of 6-day-old and 4-week-old chickens with pathogenic or attenuated avian reovirus resulted in an inapparent infection. The virus had a greater tissue distribution and persisted longer in tissues of 6-day-old chickens. Interferon was detected in only the serum and lung of infected chickens and appeared to be related to route of inoculation. Titers of interferon were greater and appeared sooner in the tissues of older chickens. Reovirus-neutralizing antibody was not detected in the serum of chickens of either age 120 days postinfection.     

Susceptibility of laboratory animals to experimental infection with Ife virus

The susceptibility of rabbits, domestic chickens and albino rats to experimental infection with Ife virus was investigated. Neither pyrexia nor clinical signs of disease were observed in infected rabbits or chickens. Low-grade viraemia (10(1.0) mouse lethal doses per 0.02 ml) occurred in intracerebrally (i.c.) inoculated chicks on the second day post-infection. Complement-fixing antibody was detected on the 14th day post-inoculation in rabbits and on the 7th day in chickens. Infant rats less than 3 and 5 days of age died after subcutaneous (s.c.) and i.c. inoculation, respectively; older rats survived infection. Ife virus titres were highest in the brain following both i.c. and s.c. inoculation.     

Immune response to avian reovirus in chickens and protection against experimental infection

Objectives To assess the efficacy of the vaccination procedure and the effect of the transfer of maternal antibodies to progeny chickens on reovirus pathogenicity.
Design To vaccinate chickens and challenge progeny chickens with high doses of homologous and heterologous viruses.
Procedure High doses of reovirus strains RAM-1, 1091 and 724 were used to induce tenosynovitis lesions. High doses were produced by concentration of viruses grown in cell culture. Then similar doses of viruses were used to challenge immunised chickens progeny.
Result Vaccination of breeding hens with the RAM-1 strain of avian reovirus, which resulted in the passive transfer of neutralising antibody to progeny chickens, completely prevented the development of tenosynovitis in 80% of progeny chickens infected with the homologous virus. Even though multiple injection of hens resulted in broadening of the normal type-specificity of the neutralising antibody response against heterologous serotypes of avian reovirus, only marginal protection against strains of two heterologous serotypes of avian reovirus was obtained.
Conclusions A model for assessing the efficacy of vaccination against avian reovirus strains on clinical signs such as tenosynovitis was developed that overcome the normal low virulence of Australian strains of avian reovirus. Breeding hens can be immunised with Australian strain of avian reovirus with passive transfer of antibody via the yolk to the progeny chickens. Although the neutralising antibody response to three injections of inactivated virus decreased the specificity of the neutralising antibody response against antigenically heterologous strains of avian reovirus, the protective immunity appeared to retain type-specificity.     

一例肾型鸡传染性支气管炎的诊断

2007年9月,郑州某鸡场发生一起疑似肾型鸡传染性支气管炎。将分离毒株接种20日龄肉鸡,于接种后第4 d出现精神不振、拉稀,第6 d出现死亡。分离病毒可致死部分鸡胚及产生卷曲胚,但不能凝集鸡红细胞,经1 %胰酶处理后能凝集鸡红细胞。经过实验室检查结果结合流行病学调查、临床症状和剖检变化,初步诊断为肾型鸡传染性支气管炎。     

Testing and management of a specific pathogen free chicken flock with special reference to avian leukosis virus infections.

A specific pathogen free (SPF) chicken flock was reared in isolation under laboratory conditions during five years and continuously tested for presence of specified avian pathogens. The potential occurrence of avian leukosis virus (ALV) was most thoroughly examined. The RIF and neutralization tests were unequivocally negative. Radioimmunoassay was used for detecting the presence of the major protein (gs-a) of the group-specific antigen of avian onoorna viruses. This test seemed to he well suited for checking ALV infections in chicken flocks whereas the COFAL (complement fixation avian leukosis) test was considered unreliable for this purpose. Yolk and serum from SPF chickens were negative for anti-gs-a antibodies measured by the radioimmunoassay; immunized or naturally infected birds showed anti-gs-a amounts correlating with the neutralizing titre. Besides, the flock was regularly tested for presence of seven other contagious avian pathogens. There was no evidence of infection.SPF chicken flock; avian leukosis; laboratory diagnosis of avian leukosis virus infections.     

J亚群禽白血病病毒(ALV-J)ELISA检测方法的建立

利用抗J亚群禽白血病病毒（ALV—J）囊膜蛋白特异性单克隆抗体JE9，建立了检测ALV—J env抗原抗体免疫复合物的ELISA方法。应用该方法检测SPF鸡血清、鸡抗禽流感H9亚型阳性血清、鸡沙门氏菌阳性血清、鸡腺病毒阳性血清、鸡新城疫阳性血清．结果均为阴性，无交叉反应；抗ALV—J阳性血清与ALV—J特异性单克隆抗体JE9能相互阻断；ALV—J阳性血清经酸处理后，ELISA检测的D490差值明显下降。对部分攻毒鸡血清样本及田间ALV—J阳性血清样本进行电镜观察，可见ALV—J样病毒粒子及ALV—J样免疫复合物。经与间接免疫荧光（IFA）检测ALV—J env抗体结果比较表明，建立的ELISA方法与IFA方法两者具有较好的群体符合率，群体符合率为8／9。这些结果表明，本研究建立的ELISA方法在ALV—J的诊断中具有很好的应用前景。     

Immunofluorescent study on egg-adapted avian encephalomyelitis virus infection in chickens.

Fluorescent antibody study showed persistent infection of egg-adapted avian encephalomyelitis virus in the central nervous system and pancreatic tissues of infected embryos and chickens hatched from them. The limited organ tropism of the egg-adapted virus in hatched chickens was in striking contrast to the systemic infection that occurs with a field strain. In chidkens orally infected with egg-adapted virus strains, transient infection of a few organs was found despite occurrence of viremia.     

Pancreas-passaged avian encephalomyelitis virus and its immunogenicity.

A serial 34-chicken pancreas passage of avian encephalomyelitis virus by oral administration was successful. Oral inoculation test with 4 passaged viruses showed rapid infection of the duodenal wall and unchangeable infection of pancreas diminishing the viral invasiveness to other organs. The passaged virus caused neither detectable viremia nor clinical avian encephalomyelitis signs and produced neutralizing antibody of high titers.     

Comparative pathogenesis in specific-pathogen-free chickens of two strains of avian hepatitis E virus recovered from a chicken with Hepatitis–Splenomegaly syndrome and from a clinically healthy chicken

Avian hepatitis E virus (avian HEV) is the primary causative agent of Hepatitis–Splenomegaly (HS) syndrome in chickens. Recently, a genetically unique strain of avian HEV, designated avian HEV-VA, was recovered from healthy chickens in Virginia. The objective of this study was to experimentally compare the pathogenicity of the prototype strain recovered from a chicken with HS syndrome and the avian HEV-VA strain in specific-pathogen-free chickens. An infectious stock of the avian HEV-VA strain was first generated and its infectivity titer determined in chickens. For the comparative pathogenesis study, 54 chickens of 6-week-old were assigned to 3 groups of 18 chickens each. The group 1 chickens were each intravenously inoculated with 5 × 10^2.5 50% chicken infectious dose of the prototype strain. The group 2 received the same dose of the avian HEV-VA strain, and the group 3 served as negative controls. Six chickens from each group were necropsied at 2, 3 and 4 weeks post-inoculation (wpi). Most chickens in both inoculated groups seroconverted by 3 wpi, and the mean anti-avian HEV antibody titers were higher for the prototype strain group than the avian HEV-VA strain group. There was no significant difference in the patterns of viremia and fecal virus shedding. Blood analyte profiles did not differ between treatment groups except for serum creatine phosphokinase levels which were higher for prototype avian HEV group than avian HEV-VA group. The hepatic lesion score was higher for the prototype strain group than the other two groups. The results indicateded that the avian HEV-VA strain is only slightly attenuated compared to the prototype strain, suggesting that the full spectrum of HS syndrome is likely associated with other co-factors.