Comparison of the dot blot hybridization assay with antigen detection assays for the diagnosis of infectious bursal disease virus infections

The use of cDNA probes as diagnostic tools for detecting infectious bursal disease virus (IBDV) antigens was compared with the agar-gel precipitin (AGP) and immunofluorescence (IF) assays. Specific-pathogen-free chickens were inoculated with the STC or IN strains of IBDV in three separate experiments. Tissue samples were collected at various intervals postinoculation (PI) and examined for viral antigens using the IF assay, the AGP assay, and the hybridization assay. Viral antigen was detected by the AGP assay for a period of approximately 3 days beginning 2 days PI and by the IF assay for approximately 4 days beginning 2 days PI. Virus was detected by the hybridization assay through the length of all the experiments (longest experiment was 24 days) beginning 1 day PI. These results suggested that the hybridization assay is more sensitive than the IF assay and the AGP assay.     

Susceptibility of Local Nigerian and Exotic Chickens to Infectious Bursal Disease by Contact Exposure

One hundred 6-week-old susceptible cockerels were inoculated with a pathogenic strain of infectious bursal disease virus (IBDV) and kept in the same pen as 100 each of 6-week-old pullets, local chickens and broilers. The cockerels developed depression and diarrhoea on day 3 post inoculation (PI) and most of the pullets and some of the local chickens and broilers showed similar signs on day 4 PI. Loss in weight was severe and similar in the pullets and local chickens, being significantly greater than that in the broilers from days 3–11 PI. The total mortality was 85%, 66.7%, 30% and 20% for the pullets, cockerels, local chickens and broilers, respectively. The lesions were more severe in the pullets and local chickens than in the broilers. IBDV antigen and antibody were detected, respectively, in all the bursal and serum samples from the infected chickens tested. The contact exposure method used in this study simulates better what happens in nature than inoculation with IBDV. The reduced mortality observed among the local chickens, compared with that (61.5%) seen in earlier studies using intraocular inoculation of IBDV, may have been due to behavioural differences that tend to result in their ingesting a relatively low dose of the virus.     

Detection of vaccine-like infectious bursal disease (IBD) virus in IBD vaccine-free chickens in Japan

The prevalence of infectious bursal disease virus (IBDV) was studied in chickens, which had not been vaccinated against IBD. Fifty sera and forty-six bursae of Fabricius from chickens showing impaired growth, collected from 7 IBD vaccination-free farms in Japan were used for virus neutralization (VN) tests and RT-PCR for detection of IBDV genome corresponding to the VP2 hypervariable region. Of the fifty sera, 39 sera (78%) from 6 farms were VN antibodies positive. Of the forty-six bursae, 37 bursae (80.4%) from 6 farms were positive in the RT-PCR assay. The sequences of all the RT-PCR products detected in this study were closely related or identical to those of the vaccine strains. These results show that vaccine-like IBDV is prevalent even in IBD vaccine-free chicken farms in Japan.     

Protective immunity against infectious bursal disease virus in chickens in the absence of virus-specific antibodies

The role of cell-mediated immunity (CMI) in pathogenesis of infectious bursal disease virus (IBDV) was investigated. One-day-old specific pathogen-free chickens were treated with 3mg of cyclophosphamide (Cy) per chicken for 4 consecutive days and, 3 weeks later, infected with the IBDV-IM strain. Chickens were examined for: (a) mitogenic response of splenocytes to ConA, as an indicator of T-cell functions in vitro, (b) antibody against IBDV by ELISA, (c) IBDV genome in various tissues by RT-PCR and (d) immunological memory. At the time of IBDV infection, Cy-treated chickens had depleted bursal tissue (an avian primary B-cell lymphoid organ), severely compromised antibody-producing ability, but normal T-cell response to ConA. In primary infection, no detectable antibody against IBDV antigen in Cy-treated, IBDV-infected chickens was observed up to 28 days post-infection (PI), while IBDV genome was detected by RT-PCR in spleen, thymus, liver and blood until 10 days PI. Like intact control chickens infected with IBDV, Cy-treated, IBDV-infected chickens suppressed splenocytes responses to ConA from 5 to 10 days PI, suggesting that intact control as well as Cy-treated chickens responded similarly to IBDV infection in the early phase. Following re-infection with IBDV, no detectable secondary antibody response to IBDV as well as IBDV genome in tissues were observed in Cy-treated chickens, while intact control chickens developed vigorous secondary antibody response. Similar to intact control chickens infected with IBDV, Cy-treated chickens after second infection with IBDV did not suppress splenocyte response to ConA. These results suggested that in the absence of detectable anti-IBDV antibodies, protection of Cy-treated chickens from IBDV infection may occur via immunological memory mediated by CMI. We concluded that under normal conditions, IBDV induces a protective antibody response, however, in the absence of antibody, CMI alone is adequate in protecting birds against virulent IBDV.     

Experimental cryptosporidiosis and infectious bursal disease virus infection of specific-pathogen-free chickens

Specific-pathogen-free chickens orally inoculated at 4 days of age with a moderately pathogenic vaccine strain of infectious bursal disease virus (IBDV) and/or at 5 days of age with Cryptosporidium baileyi oocysts remained free of overt clinical signs throughout a 16-day period postinoculation (PI). The prepatency period for C. baileyi oocyst shedding was shorter in chickens receiving higher numbers of oocysts, but once shedding was detected, there were no obvious differences in shedding patterns among groups receiving 10(3) through 10(6) oocysts. On days 8 and 16 PI, cryptosporidia were located primarily in the bursae of Fabricius. IBDV exposure was associated with bursal follicle atrophy, whereas C. baileyi infection resulted in bursal epithelial hypertrophy and hyperplasia, mild follicle atrophy, and heterophil infiltration of the bursal mucosa. Examination of experimental groups of 30 birds each indicated that concurrent infection with both agents resulted in more severe bursal lesions, more infected birds, and greater numbers of cryptosporidia in infected tissues. At the termination of the trial, 16 days PI, Cryptosporidium infection was associated with a 6% decrease in mean body weight compared with controls.     

Preparation of an agar-gel-precipitating antigen for avian encephalomyelitis and its use in evaluating the antibody status of poultry

An agar-gel-precipitin (AGP) antigen for avian encephalomyelitis virus (AEV) was prepared from infected chicken embryo brains. The antigen could precipitate specific antibodies to AEV. No nonspecific reactions were observed. Results of AGP tests were compared with those of virus-neutralization (VN) tests on both unvaccinated and AEV-vaccinated chickens. The AGP test reliably detected antibodies to AEV as early as four days postinoculation. Antibodies persisted in most vaccinated birds for over one year.     

Detection of infectious laryngotracheitis virus in trigeminal ganglia by avidin-biotin complex method in chickens: short communication

Detection of infectious laryngotracheitis virus (ILTV) by avidin-biotin complex (ABC) method was studied in trigeminal ganglia (TRG) during the acute and post-acute or latent period in chickens inoculated with an A96 strain of the antigen. TRG tissue samples were collected from uninoculated (10 chickens) and inoculated (30 chickens) animals at various intervals post inoculation (PI), and stained by the ABC method. The results indicated that no ILTV antigen was detected in the TRG between PI days 3 and 11. However, the antigen was detected in most of the chickens between PI days 13 and 41. It is concluded that the ABC method can be used successfully for the detection of ILTV antigens in TRG during post-acute or latent period.     

不同方法对鸡胚和法氏囊中囊病病毒抗原含量的检测比较

用单抗介导的抗原捕获－酶联免疫吸附试验（AC－ELISA），琼脂扩散试验（ACP）快速诊断试纸条（ISK）对感染同株强毒或弱毒囊病病毒（IBDV）的鸡胚和鸡法氏囊中的病毒抗原效价进行了检测比较，结果表明，上述3种方法测得法氏囊中温毒IBDV抗原效价分别为10^6.0(AC-ELISA),2^-3.0(AGP)t 10^-3.0，测得鸡胚中强毒IBDV抗原效价依次为10^-1.0,0和0。强毒株接种鸡胚后，只有第1代鸡胚组织可被AC－ELISA测到低效价的IBDV抗原，而第2代以后则未能测到病毒抗原，弱毒疫苗株IBDV感染鸡后，法氏囊中可测到低效价抗原，但感染鸡胚后则无可测性病毒抗原。     

应用双抗体夹心法ELISA检测IBDV的研究

从抗ＩＢＤＶ高免蛋黄液中提取ＩｇＧ，用作包被抗体和酶标记，建立了检测ＩＢＤＶ的双抗体夹心法ＥＬＩＳＡ。经抗原阻断，无关病毒对照、取代、验证等项试验，并与常规ＡＧＰ法比较，对来源不同的１００多个样品进行检测，结果表明：该法对患鸡腔上囊、脾脏的检出率均为１００％，比ＡＧＰ法敏感１００倍以上，用肉眼观察阳性与阴性之间颜色差异显著，不存在非特异性反应。试验证明该法具有满意的待异性、敏感性、快速性和稳定性，是ＩＢＤ早期病原学诊断和流行病学调查的有效手段。     

法氏囊疫苗免疫效果三种不同评价方法的比较

为了选出法氏囊疫苗免疫效果评估的合适方法,本研究使用酶联免疫吸附试验(ELISA)、琼脂糖扩散试验(AGP)和中和抗体检测3种方法对6种法氏囊灭活疫苗免疫后28 d的抗体水平进行评估,同时,对采血鸡进行攻毒,攻毒后4 d剖检所有鸡,观察法氏囊病变,评估3种抗体水平与攻毒保护之间的相关性;结果显示,ELISA和AGP方法检测免后血清结果相对较高,中和试验方法检测免后抗体值较低;ELISA和AGP方法检测疫苗免后抗体水平与攻毒保护结果基本一致,使用中和试验方法检测免后抗体与攻毒保护相关性较差;建议在实际生产中使用ELISA和AGP方法进行法氏囊疫苗免疫效果的评估。     

传染性法氏囊病免疫保护试验中3种评定指标的比较

100只SPF鸡均分为5组，A、B、c3组免疫后攻毒，接种3批次自制的IBD基因工程重组亚单位油乳剂疫苗；D组不免疫不攻毒，E组不免疫而攻毒。免疫后第22天，感染IBDV强毒株BC-6／85。攻毒后第4天，将所有存活的鸡只以颈脱臼致死，收集法氏囊，以3种方法和指标（法氏囊眼观病变；法氏囊显微病变；法氏囊中IBDV抗原检测）进行分析，以评定免疫保护率。结果显示，以这3种方法和指标评定，A组免疫保护率为90％，B、C组免疫保护率均为95％；试验鸡A3、A14、B7、C16、E1～E20，法氏囊眼观病变明显，法氏囊显微病理损伤评分为3～5分，琼脂免疫扩散试验检测法氏囊中IBDV抗原均为阳性；其他试验鸡，法氏囊眼观无明显异常，法氏囊显微病理损伤评分在3分以下，琼脂免疫扩散试验检测法氏囊中IBDV抗原均为阴性。结果表明，这3种方法和指标在IBD疫苗免疫保护试验评定中具有很好的一致性。     

An enzyme-linked immunosorbent assay for the detection of antibody against avian influenza virus

An enzyme-linked immunosorbent assay (ELISA) was developed for detecting antibody to type A avian influenza (AI) virus. The sensitivity and group specificity of the AI-ELISA were compared with those of the agar-gel-precipitin test (AGPT) and the hemagglutination-inhibition (HI) test under conditions of both controlled and field exposure. During the course of temporal experimental infection (0-76 days) of specific-pathogen-free (SPF) chickens with AI subtype Hav9N2, the AI-ELISA was able to detect specific AI antibody as early as 8 days postinoculation (PI), and it measured rising levels of antibody through 35 days PI, at which time the chickens were re-exposed to AI virus. Conversely, AGP tests were negative through 35 days PI, and HI tests began to detect low levels of AI antibody only at 21 days PI. Following a secondary infection at 35 days PI with the same AI subtype, all tests measured rising levels of AI-specific antibody (35-76 days PI). However, the AGP test was positive at only the 7- and 14-day samplings postsecondary immunization. Under field conditions, the AI-ELISA was able to detect serum AI antibody in flocks from which highly pathogenic AI was isolated, but the AGP tests of these sera were negative.     

免疫胶体金试纸膜和AGP检测vvIBDV GX株在SPF鸡体内的侵染性变化规律

对28日龄无特定病原(SPF)鸡通过点眼、滴鼻方式人工感染了传染性法氏囊病病毒(IBDV)超强毒株GX;自感染第2天至第9天,每天用免疫胶体金试纸膜和琼脂扩散试验(AGP)两种方法检测九种组织(法氏囊、脾脏、胸腺、肾脏、肝脏、盲肠、扁桃体、肺脏、心脏、直肠内容物)的病毒含量变化,初步探索出传染性法氏囊病病毒在鸡体内各组织的侵染性变化规律。     

检测禽流感病毒抗体的重组核蛋白间接ELISA方法的建立

以大肠杆菌系统表达的H9N2亚型禽流感病毒（AIV）核蛋白（NP）为抗原，建立了禽流感间接酶联免疫吸附试验抗体检测技术（NP—ELISA）。对263份待检血清（包括临床收集的243份血清和20份H9N2亚型AIV免疫鸡阳性血清）进行检测，NP—ELISA与琼脂免疫扩散试验（AGP）的总符合率为83．3％，与血凝抑制试验（HI）的总符合率为92％。特异性试验表明，NP—ELISA方法可以检测H5、H7和H9亚型AIV特异性抗体，检测为阳性的血清样品能够被阳性鸡胚尿囊液阻断。敏感性试验证实，NP—ELISA最早可以检测鸡感染后7d的血清样品，并于感染后10d确定100％血清阳性，而AGP检测直到首免后21～28d才出现部分血清阳性，HI检测直到10～14d才出现部分血清阳性，并且NP-ELISA要比HI敏感4～40倍。试验证明，NP—ELISA是检测AIV血清型特异性抗体的一种特异、敏感、快速、经济的血清学检测技术。     

Development of a one-step strip test for the diagnosis of chicken infectious bursal disease

A rapid diagnostic strip for chicken infectious bursal disease (IBD) was developed based on membrane chromatography using high-affinity monoclonal antibodies directed to chicken infectious bursal disease virus (IBDV). The diagnostic strip has high specificity for detection of chicken IBDV antigen and recognizes a variety of the virus isolates, including virulent and attenuated strains, with no cross-reactivity to other viruses, such as Newcastle disease virus, Marek's disease virus, infectious bronchitis virus, infectious laryngotracheitis virus, and egg-drop-syndrome virus. The results showed that its specificity was highly consistent with the agar-gel precipitation test (AGP). The diagnostic strip detected as low as 800 median egg lethal dose (ELD50) viruses in the IBDV BC6/85-infected sample, which was comparable with AC-ELISA (400 ELD50) and 32 times more sensitive than the AGP test (2.56 x 10(4) ELD50). In experimental infection, IBDV was detected in the bursa as early as 36 hr postinfection with the diagnostic strip before the clinical signs and gross lesions appeared. It takes only 1-2 min to do a strip test to detect chicken IBDV antigen after the specimen is grounded in a whirl pack with finger massage.     

原位PCR检测鸡传染性法氏囊病病毒

采取临床病例鸡的法氏囊制成石蜡切片,经蛋白酶K处理、原位RT-PCR后,用地高辛精标记探针进行原位杂交检测传染性氏囊病病毒（IBDV）。结果10个病例有8个呈阳性,2个阴性。本试验尝试利用具有极高灵敏度的原位PCR方法,从组织中检测低拷贝甚至单拷贝的目标序列,以鉴别隐性感染或混合感染,为IBDV的诊断和分子流行病学的分析提供了一种新的手段。     

Persistent infection with chicken anaemia virus and some effects of highly virulent infectious bursal disease virus infection on its persistency

Chicken anaemia virus (CAV) infectivity and the effect of highly virulent infectious bursal disease virus (hv IBDV) infection on CAV's infectivity were examined in chickens inoculated with CAV or inoculated dually with CAV and hv IBDV. Five chickens inoculated dually with hv IBDV at 35 days old and then with CAV at 40 days old exhibited no clinical signs of disease, but showed atrophic bursae of Fabricius when necropsied 4 weeks later. Upon examining the chickens at 7 days postinoculation (dpi) with CAV, it was found that hv IBDV infection had inhibited production of virus neutralising (VN) antibody to CAV, and that it was possible to recover CAV from plasma of these chickens. Although VN antibody to CAV appeared after 14 dpi, CAV was recovered from blood cells (BC s) at high titres ranging from 10(2.5)to 10(5.5)TCID(50)/0.1 ml, 7 to 28 dpi in IBDV -induced immunosuppressed chickens. In addition, CAV was sporadically recovered, using rectal swabs, from the dually inoculated chickens at low titers, ranging from 10(1.0)to 10(2. 0)TCID(50)/0.1 ml). In contrast, although CAV was recovered from BC s in most of the chickens inoculated with CAV alone, the titers were lower (10(1.0)to 10(2.5)TCID(50)/0.1 ml). No CAV was detected from the rectal swabs of these chickens. The results of virus recovery were confirmed by polymerase chain reaction. This study first examined the persistency of CAV in BC s and the effective enhancement of primary CAV infection as a result of immunosuppression caused by hv IBDV infection.     

鸡IBD蜂胶囊毒灭活苗的制备及其最佳用量的筛选

以典型发病鸡群的法氏囊为组织源，以蜂胶为佐剂，按病毒性动物组织灭活疫苗制造基本程序制备灭活苗；以不同的剂量皮下接种．GIBD母源抗体的10日龄AA肉鸡，按常规方法检测其不同免疫期的AGP抗体阳性率、AGP效价和对强毒攻击的保护率。结果显示：0．5mL／只剂量组的受试鸡AGP抗体的阳性率在免疫后10d达到60％，20d上升到100％，90d仍有80％的阳性率。在免疫后第20、50d的攻毒试验中，保护率均为100％。