Characterization of infectious bursal disease viruses isolated in 2007 from Delmarva commercial broiler chickens

A study was performed in 2007 to isolate and characterize infectious bursal disease viruses (IBDVs) in commercial broilers grown in the Delmarva (DMV) Peninsula region of the United States. Bursae of Fabricius were collected weekly from 1 to 4 wk of age from broilers on 10 farms with a history of poor performance. Microscopic pathology was used to determine the infectious bursal disease (IBD) status of the broilers. Bursae from 1- and 2-wk-old broilers did not show IBD microscopic lesions. Moreover, broilers on 1 of the 10 farms were IBD lesion free at 3 and 4 wk of age. However, 3 of 9 and 9 of 9 farms yielded broilers with IBD-affected bursae from 3- and 4-wk-old commercial broilers, respectively. Ten IBDV isolates were recovered from 3 of 3 lesion-positive bursal pools at 3 wk of age and 7 of 9 lesion-positive bursal pools at 4 wk of age. Analysis of the viral protein (VP) 2 genes identified all isolates as serotype 1 Delaware (Del) variant viruses. Five field isolates, each representing different molecular clades of the Delaware variant viruses, were selected for further study. Experimental infection of specific-pathogen-free white leghorn chickens with isolates DMV/4813/07, DMV/4947/07, DMV/4955/07, DMV/5038/07, and DMV/5041/07 produced gross and microscopic pathology of the bursa consistent with Delaware variant infection. Monoclonal antibody testing showed DMV/4813/07, DMV/4947/07, DMV/ 4955/07, and DMV/5041/07 to be similar to previous recognized variant viruses. However, DMV/5038/07 was found to be unreactive with the monoclonal antibodies that typically recognize reference strains STC, Del E, GLS, RS593, and AL2. In a challenge of immunity study, 10-day-old progeny from breeders immunized with a commercially available inactivated IBDV vaccine containing the Del E and classic strains were protected to a lesser degree against isolate DMV/5038/07 compared to Del E challenge based on microscopic lesion scores (P < 0.01) of the bursa. This result suggests the virus is antigenically different from the Del E strain contained in the vaccine. Collectively, the monoclonal antibody and progeny challenge of immunity findings suggest DMV/5038/07 is antigenically different from the Del E strain contained in the vaccine.     

Efficacy of live vaccines against serologic subtypes of infectious bursal disease virus

Experiments determined the efficacy of live vaccines in specific-pathogen-free broilers against serologic subtypes of infectious bursal disease virus (IBDV). Challenge isolates were the Delmarva variant E, a standard serotype I (APHIS) and a variant isolate from Mississippi. The vaccines were a cloned standard (CS) vaccine (Clone Vac-D78), a cloned variant (CV) vaccine (Bursa Vac IV), and an uncloned standard (UCS) vaccine (Bursine II). The severity of microscopic lesions was correlated with bursal atrophy as measured by bursa-weight-to-body-weight ratios. All vaccines provided adequate protection against the APHIS challenge. The three vaccines averaged 77% protection against APHIS in the first experiment and 78% in the second. Protection against the variant E and Miss isolates was considerably less for all vaccines. The three vaccines produced an average 70% protection against the Miss isolate in the first experiment and 69% in the second experiment. Against the variant E virus, the three vaccines averaged 67% protection in the first experiment and 65% in the second. There were significant differences in protection for each vaccine against individual IBDV subtypes. Results showed that no vaccine provided good protection (at least 80%) against all three subtypes of IBDV.     

四株鸡传染性法氏囊病病毒毒力的研究

对从黑龙江省分离的４株鸡传染性法氏囊病病毒通过易感鸡接种,用病理学技术进行了致病力的研究。结果表明,各毒株毒力有一定差异,其中Ｈ３、Ｈ４株毒力高于Ｈ１、Ｈ２株,且有迅速致法氏囊萎缩的特性;Ｈ３、Ｈ４株引起试验鸡法氏囊指数显著下降（Ｐ＜００５）,脾脏指数明显增加（Ｐ＜００５）。Ｈ３、Ｈ４株接种５０日龄Ｄ７８疫苗免疫鸡,免疫保护指数分别为５０％、６０％,传统疫苗不能提供充分保护。     

A study of the epidemiology of infectious bursal disease in poultry in Queensland, 1976–1979

The epidemiology of infectious bursal disease (IBD) was studied by serology and sometimes by visual examination of the bursa of Fabricius in poultry flocks in Queensland during 1976–1979.
Ten flocks, each of approximately 30,000 meat breeding chickens, were surveyed. All chickens had maternally-derived antibody against IBD virus (IBDV) at hatching and active antibody was not detected while the chickens were brooded on rearing farms. When distributed to breeding farms, 7 of the flocks developed antibody when 11 to 25 weeks of age. The remaining 3 flocks were vaccinated by infection of 10% of the birds and within 4 weeks more than 80% of the chickens had developed precipitating antibody to IBDV.
Blood samples of 20 to 30 broiler chickens were collected at slaughter (7 to 9 weeks of age) from each of 312 broiler flocks raised on 37 contract farms. While the samples from 21 flocks were without detectable antibody to IBDV, all serum samples for 263 flocks contained antibody. The ratio of bursal weight to bodyweight was significantly lower in birds from 144 flocks having antibody to IBDV than in birds from 10 flocks that were without detectable antibody. In sequential studies, IBDV antibody became demonstrable in 27 of 30 flocks when the chickens were one to 6 weeks of age and was accompanied by bursal atrophy.
Serological investigation of 4 flocks of layer breeding chickens on a multi-age farm at approximately monthly intervals resulted in antibody to IBDV being detected at every examination.
Serological tests and bursal examinations were carried out weekly in 2 flocks each of 4000 layer chickens between one and 20 weeks of age. Serum antibody developed in one flock at 4 weeks of age and in the other at 17 weeks of age. In both flocks, bursal atrophy occurred concurrently with the development of antibody.     

传染性法氏囊病病毒株VP2基因在重组腺病毒中的表达

用RT-PCR方法从传染性法氏囊病(IBD)免疫预防失败的病鸡法氏囊组织AH1与AH2中扩增传染性法氏囊病病毒(IBDV)VP2基因。序列分析结果显示,AH1与AH2病毒VP2基因长度均为1350nt,编码450aa,核苷酸和氨基酸序列的同源性分别为98.2%、99.3%,七肽基序均为SWSASGS,在222、253、256、279、284、294和299位上的氨基酸残基分别是A、Q、I、D、A、I和S,具有IBDV强毒的分子特征。进一步将VP2基因克隆入人5型腺病毒穿梭载体(pShuttle-CMV),与腺病毒骨架载体(pAdEasyTM)共转化大肠杆菌BJ5183进行同源重组并转染HEK-293A细胞,经多次亚克隆获得了重组腺病毒rAd-(IBDV)VP2。利用Western-blot、IFA等方法检测IBDVVP2蛋白的体外表达情况,结果证明VP2基因在腺病毒中获得了表达。     

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.     

Infectious bursal disease virus variant from commercial Leghorn pullets

An infectious bursal disease virus (IBDV) was isolated from 39-to-43-day-old commercial leghorn pullets suspected of having infectious bursal disease (IBD). These chickens had been vaccinated with a commercial live IBDV vaccine at 28 and 35 days of age. An isolate designated IN was recovered using specific-pathogen-free (SPF) chickens and the BGM-70 established cell line. Experimental studies using SPF chickens vaccinated with either inactivated vaccines made from the vaccine strain used in the problem flock or a standard-type vaccine indicated no protection against the IN isolate. However, two variants and another standard-type vaccine induced protection against the IN isolate. Cross-neutralization tests indicated that the IN isolate differed antigenically from commercial vaccine strains and was related to the variant IBDV strains recently isolated from broilers. To our knowledge, this is the first report of a variant IBDV recovered from commercial layer chickens in the United States.     

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.     

CpG寡核苷酸对IBDV VP2基因真核表达质粒免疫增效作用

以传染性法氏囊病病毒(IBDV)VP2蛋白基因表达质粒DNA为免疫原，以CpG的寡核苷酸(CpG-0DN)为免疫佐剂，肌肉注射于14日龄SPF鸡，1周后加强免疫1次，2次免疫后15d和21d分别测定血清ELISA抗体效价，并于免疫后21d用IBDV99儿强毒株攻毒和进行病理学观察。结果显示，(1)VP2基因重组质粒DNA与CpG共同免疫组的ELISA抗体水平明显高于VP2重组质粒免疫组；(2)IBD弱毒苗与VP2重组质粒免疫组抗体水平明显高于VP2重组质粒免疫组，且比VP2基因重组质粒DNA与CpG共同免疫组略高；(3)VP2基因重组质粒DNA与CpG共同免疫组及IBD弱毒苗与VP2重组质粒免疫组可明显降低IBDV强毒攻击后引起的急性发病率和死亡率。由此表明，CpG寡核苷酸对IBDV VP2蛋白基因真核表达质粒免疫具有明显增强作用，有很大的应用前景。     

The Characterization of Infectious Bursal Disease Virus Strains/Isolates from Field Outbreaks in India

Pahar, B. and Rai, A., 1997. The characterization of infectious bursal disease virus strains/isolates from field outbreaks in India. Veterinary Research Communications, 21 (4), 289-301Three infectious bursal disease virus (IBDV) isolates were adapted to culture in chick embryo fibroblast cells in which they produced a cytopathic effect. The isolates were identified as IBDV by virus neutralization tests using a standard hyperimmune serum against infectious bursal disease, physicochemical properties and their pathogenicity in chick embryos and chicks. The IBDV S394 strain was antigenically different from IBDV S194/IBDV S494 as well as from the IBDV Intermediate Georgia strain, one of the vaccine strains in use in India.     

Molecular characterization and phylogenetic analysis of infectious bursal disease viruses isolated from chicken in South China in 2011

Infectious bursal disease virus (IBDV) is a double-stranded RNA virus that causes immunosuppressive disease in young chickens. Thousands of cases of IBDV infection are reported each year in South China, and these infections can result in considerable economic losses to the poultry industry. To monitor variations of the virus during the outbreaks, 30 IBDVs were identified from vaccinated chicken flocks from nine provinces in South China in 2011. VP2 fragments from different virus strains were sequenced and analyzed by comparison with the published sequences of IBDV strains from China and around the world. Phylogenetic analysis of hypervariable regions of the VP2 (vVP2) gene showed that 29 of the isolates were very virulent (vv) IBDVs, and were closely related to vvIBDV strains from Europe and Asia. Alignment analysis of the deduced amino acid (aa) sequences of vVP2 showed the 29 vv isolates had high uniformity, indicated low variability and slow evolution of the virus. The non-vvIBDV isolate JX2-11 was associated with higher than expected mortality, and had high deduced aa sequence similarity (99.2 %) with the attenuated vaccine strain B87 (BJ). The present study has demonstrated the continued circulation of IBDV strains in South China, and emphasizes the importance of reinforcing IBDV surveillance.     

Comparison of a putative second serotype of chicken infectious anemia virus with a prototypical isolate I. Pathogenesis

CIAV-7 is a virus with similar pathogenic and physicochemical characteristics to, but antigenically distinct from, chicken infectious anemia virus (CIAV). The pathogenesis of CIAV-7 was evaluated in a comparative study with a representative isolate of CIAV, the Del-Ros strain. The pathogenesis of CIAV-7 was similar to Del-Ros on the basis of the clinical disease induced and gross and microscopic lesions, although CIAV-7 produced fewer and less severe lesions overall. A second comparative pathogenesis study was performed with Del-Ros and CIAV-7, both alone and in combination with infectious bursal disease virus (IBDV). In this study, the pathogenesis of CIAV-7 was similar to Del-Ros in clinical, gross, and microscopic lesions in the bone marrow. However, thymic lesions were less severe in CIAV-7-inoculated birds. The interaction between Del-Ros and IBDV was synergistic, whereas there was no observed potentiation of CIAV-7-induced disease by IBDV. Progeny from breeder flocks from several geographic locations in the eastern United States were challenged with CIAV-7 or Del-Ros to assess protection by maternal antibodies. Some progeny from all flocks had protection against CIAV-7 challenge, providing evidence for the presence of CIAV-7 in the field. Additionally, the number of birds protected against CIAV-7 or Del-Ros challenge varied within flocks, demonstrating that the agents are serologically distinct.     

A study of breeder vaccination programs and problems in the broiler progeny in Saskatchewan utilizing enzyme-linked immunosorbent assay

A survey of antibodies against infectious bursal disease virus (IBDV), infectious bronchitis virus (IBV), Newcastle disease virus (NDV), and reovirus (RV) was conducted in broiler-breeder flocks and selected progeny broiler flocks utilizing the enzyme-linked immunosorbent assay. Marked differences in antibody titers between different breeder flocks were related to differences in vaccination programs. Poor performance in some progeny broiler flocks was related to low antibody titers against IBDV in the source breeder flocks. Progeny broiler flocks in which there was a high incidence of condemnations for airsacculitis had elevated antibody titers against IBV. A few progeny broiler flocks that experienced high mortality due to gangrenous dermatitis had no antibody titers against IBDV at processing. Antibody titers against RV were very variable and could not be related to any production problems.     

Failure of two serotype II infectious bursal disease viruses to affect the humoral immune response of turkeys

The effect of serotype II infectious bursal disease virus (IBDV) isolates from turkeys on the homoral immune response of turkey poults was determined. Following exposure to the OH IBDV isolate, poults in two experiments were inoculated with sheep red blood cells, which is a T-dependent antigen, and poults in two other experiments were inoculated with Salmonella heidelberg O antigen, which is a T-independent antigen. Prior exposure to serotype II IBDV did not affect serum antibody titers to these antigens. IBDV infection also did not affect the concentrations of serum immunoglobulin M (IgM), IgG, or IgA in these poults. Bursa:body weight ratios of OH IBDV-infected poults were not significantly different from those of uninfected controls. In one experiment, the humoral immune response of poults to the LaSota Newcastle disease vaccine was not affected by infection with the MO IBDV isolate. Although no clinical infectious bursal disease was observed in any poult in these experiments, the serotype II IBDV isolates were infectious and transmissible in poults.