초록 ▼

5. 최종 연구결과 요약
◦세부과제명: 모체이행항체별 야외감염 방어효과 분석
- 국내 사육 육용종계(33주령)에서 태어난 후대병아리 22수를 대상으로 모체이행항체 역가소장추이를 경시적으로 조사하였다.
- 육용종계(33주령)에서 태어난 5일령 후대병아리 75수에 IBDV 국내분리 강독주 (Kr/D62/06)를 공격접종하여(105.0ELD50)을 공격접종한 후 모체이행항체를 가진 육계에서의 야외감염방어효과를 분석하였다.
- SPF닭(3~4주령)에 IBDV 중간독형 유사 국내분리주 2주 및 백신주 2주를 접종하여,

5. 최종 연구결과 요약
◦세부과제명: 모체이행항체별 야외감염 방어효과 분석
- 국내 사육 육용종계(33주령)에서 태어난 후대병아리 22수를 대상으로 모체이행항체 역가소장추이를 경시적으로 조사하였다.
- 육용종계(33주령)에서 태어난 5일령 후대병아리 75수에 IBDV 국내분리 강독주 (Kr/D62/06)를 공격접종하여(105.0ELD50)을 공격접종한 후 모체이행항체를 가진 육계에서의 야외감염방어효과를 분석하였다.
- SPF닭(3~4주령)에 IBDV 중간독형 유사 국내분리주 2주 및 백신주 2주를 접종하여, 폐사율, F낭병변 및 증체량 등 닭에 대한 병원성을 조사하였다.
- IBDV 중간독형 플러스 유사 국내분리주 3주 및 5종의 백신주 (중간독형 플러스 3주 및 중간독 2주) 등 총 8주의 IBDV에 대하여 유전학적 특성을 비교․분석하였다.
◦세부과제명: IBD 백신접종 프로그램별 숙주면역반응 분석
- 국내 감보로병 백신접종 프로그램 현황을 조사하고자 5개도 156개 농장을 대상으로 설문조사를 하였다.
- 보편적인 ND 및 IBD 예방백신 접종일령은 14일령이며, 백신접종방법의 선호도는 ND 및 IBD 백신을 동시에 접종하는 방식이었다.
- SPF닭(3-4주령)에서의 백신주 2주 및 백신유사주 2주의 병원성을 측정한 결과Winterfield (I+백신) 및 07Q86(mixed) 분리주는 10%의 폐사율 및 4.3의 높은 BF 병변지수를 보였다.
- SPF닭(3-4주령)에서 백신주 및 백신유사주의 국내강독주 방어효능 비교조사를 실시한 결과 모두 100%의 우수한 방어효과를 보였으나, 4.0의 높은 BF 병변지수를 보였다.
- 국내산란계 병아리 및 육계병아리를 대상으로 일령별 백신을 접종하고, 접종후 혈청학적 반응 및 증체량, 조직병리학적 소견 등을 조사하였다.

Abstract ▼

The protective effect against very virulent infectious bursal disease virus at different levels of maternal antibody in broiler chickens
Infectious bursal disease (IBD) is a highly contagious poultry disease causing severe immune suppression and death in young chickens. Since first report in 1992

The protective effect against very virulent infectious bursal disease virus at different levels of maternal antibody in broiler chickens
Infectious bursal disease (IBD) is a highly contagious poultry disease causing severe immune suppression and death in young chickens. Since first report in 1992 in Korea, chickens are routinely vaccinated with IBDV vaccines. Immunization against the disease is achieved by vaccination within activated oile mulsified vaccine for laying hens and with attenuated live vaccines for young birds. Maternal antibodies transferred from vaccinated dams to offsprings are important for protection of young birds against the disease and antibody’s titers are indicator for determination timing of vaccination with live vaccines in young birds. However, the correlation between antibody titers and disease protection is still not clear. In this study, the protection by mAb against very virulent IBD (vvIBD) was evaluated in commercial broilers from vaccinated dams. All birds with virus neutralizing mAb titers of >32 were grouped on the basis of the level of anti-IBDV mAb prior to challenge with vvIBD virus. All birds survived for 14 days after challenge with vvIBD virus, although some showed mild clinical signs. When examined histopathologically and virologically on 14 dpc, challenged birds exhibited the bursal lesion score inversely proportional to titers of anti-IBD virus neutralizing mAb immediately before vvIBD virus challenge. However, viral load in bursa of Fabricius, as determined by a real time PCR assay, did not show correlation with titers of anti-IBDV neutralizing antibodies and even IBD viral genes was detected in birds having neutralizing titers of 1,024 or greater before challenge. Prolonged virus shedding from cloaca was observed in birds with pre-challenge mAb titers of 128 or greater until 14 dpc, but not in birds with pre-challenge mAb titers of <128. Our results indicate that maternal antibodies transferred from vaccinated hens can provide young chickens with full protection from clinical disease but not from infection.
Characteristics of intermediate plus-like infectious bursal disease virus from a broiler flock in Korea
Infectious bursal disease (IBD) is an acute and contagious disease in young chickens causing primarily lymphoid depletion in the bursa of Fabricius (BF). Very virulent IBD for young chickens (vvIBD) is enzootic among broiler chickens in Korea. Therefore, most of broiler chickens are routinely vaccinated using attenuated live vaccines at 10-14 days old. The majority of IBDV live vaccines are manufactured from IBDV strain with virulence of intermediate plus (intermediate plus type vaccine). In recent, we isolated an IBDV from a broiler flock with IBD vaccination. In this study, we investigated the pathogenicity for SPF chickens of the IBDV isolate.
IBDV (isolate 080502) was isolated from bursal samples from six dead birds (26 days old) of a broiler flock with elevated mortality and poor performance after vaccination with IBDV intermediate plus type vaccine at 14 days old. For genetic characterization, full length genome segments A and B of IBDV were RT-PCR amplified using known PCR primer sets and sequenced. The sequence data were analyzed and compared with genetic information of known IBDV strains winterfield 2512, D78 and S706. The sequences were aligned using the MegAlign program in the Lasergene package(DNASTAR). Phylogenetic relationships were established with the computer program TREEVIEW for Windows. In vivo pathogenicity tests, 3-wk-old SPF chickens (n=10) was inoculated orally with 080502 containing 104.1EID50 per ml and observed for clinical signs for a week. Four SPF chickens were used as control under same condition. All birds were sacrificed on day 7 post-challenge and measured by the bursa/body weight(B:B) ratio and bursal score.
Full length segments A of 3kb long and B of 2.6kb long were successfully amplified by RT-PCR from IBDV isolate 080502. The amplified DNA products were sequenced and compared with other reference strains. Phylogenetic analysis revealed that the 080502 isolate was placed into a cluster consisting of IBDV strains of intermediate plus type based on both segment A and segment B. In sequence comparison at amino acid level, the 080502 isolate was the most closely related with Winterfield 2512 strain, which is used as the intermediated-plus vaccine strain (homology of >99%). When challenged with the 080502 isolate, one of infected chickens died 4 days post challenge and the dead bird showed pathological lesions such as hemorrhages on the thigh muscle, cecal tonsil and junction of proventriculus and gizzard. The remaining birds were alive for a week-period (10% mortality). When sacrified on day 7, the birds (n=9) showed severe atrophy of BF. None of control birds (n=4) showed clinical signs thorough experiment.
Challenge group showed significant reduced weight gain and atrophied BF compared to control group on day 7 post-challenge (P<0.001).
In this study, the 080502 isolates were sequenced and analyzed based on sequence analysis of segments A and B. Our result indicates that the 080502 isolate was almost identical to Winterfield 2512. Considering that the virus was isolated from vaccinated flock, the 080502 isolate might be originated from the intermediated-plus vaccine strain Winterfield 2512. Our pathogenicity test revealed that the isolate 080502 was pathogenic for SPF chicken. Further studies are needed to investigate the immunosuppressive effects of intermediate plus type vaccine as well as the 080502 isolate on commercial broilers under field condition for improved vaccination program.

목차 Contents

• 총괄요약표 ... 1
• 연구과제 최종결과보고서 ... 3
• Ⅰ. 연구배경 및 목표 ... 3
• Ⅱ. 연구방법 및 수행전략 ... 4
• Ⅲ. 연구결과 ... 5
• Ⅳ. 연구결과요약 ... 19
• Ⅴ. 고 찰 ... 20
• Ⅵ. 연구결과 활용실적 및 계획 ... 21
• Ⅶ. 참고문헌 ... 21
• Ⅹ. 영문초록 ... 23
• 끝페이지 ... 25