Newcastle disease in a vaccinated flock which had experienced subclinical infectious bursal disease

A flock of 4,500 Cobb broilers inoculated with Newcastle disease vaccine intra-ocular strain B1 type at 10 days of age developed clinical signs of the disease 19 days later; the mortality rate was 71%. Necropsy examinations showed characteristic lesions. Newcastle disease virus was isolated and identified in the allantoic fluid of embryonating chicken eggs by haemagglutination and haemagglutination-inhibition tests. Histopathological examination showed that follicles of the bursa were depleted of lymphocytes, had many large cavities and were being repopulated by newly formed healthy lymphocytes. Both the acute and convalescent serum samples were positive for infectious bursal disease antibodies in agar gel precipitation tests. Haemagglutination inhibition titres of the acute and convalescent sera were 20 to 80 and 80 to 640 respectively. The vaccine failure may be due to either the subclinical bursal disease or the highly pathogenic nature of the wild Newcastle disease virus.     

Biological properties of a naturally attenuated infectious bursal disease virus isolated from a backyard chicken flock

The biological properties of an infectious bursal disease (IBD) virus isolated from bursas collected during an outbreak in a village chicken flock in Macedonia are described. The mortality rate was 50%. Two viruses coexisted in the bursas of infected chickens (IBDVwt and IBDVtc). The virus termed IBDVtc grows on chicken embryo fibroblast (CEF) cells from the first passage. Specific pathogen free chickens inoculated with IBDVtc at passage level 4 did not develop any clinical signs of disease. Some discrete bleeding on the leg muscles was seen and the bursa of Fabricius revealed pathological lesions similar to those caused by classical strains. However, the bursa recovered quickly (bursa lesion score 2) by 14 days post infection (PI). We also found evidence of bursal repopulation by means of perinuclear antigen staining. Strong CD3 influx was evident at 4 days PI, and at 33 days PI the CD3+ cell finding was comparable to the control. The mean antibody titre was 9.2 log 2 at 14 days PI. The amino acid composition of VP2 in IBDVwt (222 Ala, 242 Ile, 253 Gln, 256 Ile, 279 Asp, 284 Ala, 294 Ile and 299 Ser) is described. The same sequence was found in IBDVtc, except for two point mutations, at Gln253→His and Ala284→Thr. Such amino acid substitution is responsible for partial attenuation and the ability of the strain to replicate in cell culture. None of the commercial vaccine viruses has a similar arrangement of amino acids in the variable domain of IBDV. This strongly suggests that IBDVtc originates from a very virulent strain. To the best of our knowledge, this is the first report of a concomitant infection of chickens with highly pathogenic IBDV and its mutant counterpart.     

Effect of thymus extract on immunologic reactivity of chicken vaccinated with infectious bursal disease virus.

The effects of crude thymus extract on the immune response and protection against challenge with virulent infectious bursal disease virus (IBDV) were studied in one-day-old chick. Oral administration of thymus extract (1 ml/kg) markedly and significantly increased the total protein, albumin, globulin, Tri-iodothyronine (T3), Thyroxine (T4) and the body weight gain in one-day-old chick. In addition, it increased the total lymphocytic count over four weeks after administration. Although vaccination also increased total protein, globulin, T4 and the total lymphocytic count but it significantly decreased the body weight gain of the chick and administration of thymus extract, before, during or after vaccination markedly improved the vaccination effectiveness with significant elevation of the globulin level and body weight gain of the chick. It also prevented the decrease in the relative weights of bursa, spleen and thyroid gland which commonly prevailed during vaccination. Chicken administered thymus extract and vaccinated with infectious bursal disease (IBD) vaccine showed 100% protection against challenge with IBDV. Meanwhile the vaccinated non-thymus treated group exhibited 80% protection against IBDV challenge. These results indicate a potentiating effect of thymus extract on the immune system in baby chick. These findings are supported by ELISA results that showed a marked increase in antibody titers in thymus treated groups. Additionally, microscopical examination of the bursa and the existent lymphoid hyperplasia in thymus treated groups but not vaccinated group support our findings.     

鸡传染性法氏囊病的诊治报告

自2005年春季以来,法库县频繁发生鸡传染性法氏囊病,其发病日龄逐渐拓宽,最早7日龄,最迟120日龄。临床表现及病理变化逐渐趋向非典型性,尖峰式零星死亡,现将诊治情况报告如下。     

鸡传染性法氏囊病的诊断

鸡传染性法氏囊炎病是一种主要危害鸡的体液免疫中枢器官——法氏囊的病毒性传染病。牡丹江市某大型养鸡场2006年10月,购自某种鸡场海     

夏季谨防鸡法氏囊炎

近年来,每当进入5月份以后,随着北方温度的升高,养户们开始大量饲养和进购鸡雏.鸡法氏囊炎的发病率开始逐渐增多,在7～8月份达到发病高峰,10月份以后随着温度、湿度的降低,发病率又呈逐渐下降的趋势.     

鸡传染性法氏囊病的综合防治

鸡传染性法氏囊病(IBD)是由双RNA病毒科的传染性法氏囊病毒(IBDV)引起幼鸡的一种急性、高度接触性传染病.病鸡表现为精神萎顿、食欲不振、下痢、震颤和衰竭.剖检以脱水、骨骼肌出血、肾小管尿酸盐沉积、法氏囊肿大出血和浆膜面覆盖有淡黄色干酪样或奶油样渗出物为特征.该病主要侵害法氏囊,法氏囊是禽类特有的淋巴器官,孵化出壳的雏鸡法氏囊已存在,性成熟前发育最大,此后逐渐萎缩,直至完全消失.本病具有发病骤然、病程短、高发病率、低死亡率的特点,是养鸡场鸡群发病最频繁并造成养鸡业重大经济损失的主要疾病之一.笔者根据多年来的临床实践、学习与研究,现将IBD的流行特点、临床症状、剖检变化、临床诊治以及在预防上应该采取的措施等方面作一总结,为兽医临床上防治IBD提供具体方法,仅供参考.     

Lysis of chicken lymphocytes by infectious bursal disease viruses

Infectious bursal disease virus types 1 and 2 were able to induce direct lysis of chicken bursal cells, thymus cells, and peripheral blood lymphocytes in chromium-release assays. These two viruses were unable to lyse two established lymphoblastoid cell lines, although IBDV-1 was capable of multiplying in MSB-1 cells.     

鸡传染性法氏囊病防制研究进展

传染性法氏囊病毒穴IBDV雪可引起鸡急性、高度接触传染性的免疫抑制性疾病,即传染性法氏囊病(IBD)。该病是由Gosgrove穴1957年雪在美国首次发现的,现已遍及全世界主要养禽地区,给世界养禽业造成了巨大的损失,被国际公认为鸡的三大疫病之一。1962年Cosgrove正式报道了该病在美国特拉华州甘布罗镇的肉鸡群中发生,因此又称“甘布罗病”。本病先后流行于美国、英国、日本、中国、印度等30个国家和地区,呈世界性流行。IBD疫苗的使用,曾使本病一度得到控制,但进入80年代中期后,IBD的流行出现了许多新特点:一是IBD呈暴发性流行,区域广;二是…     

种公鸡管理技术要点

在种鸡场的生产管理中,一些管理者往往只是片面地追求高产蛋率,而忽视了另外一项重要的生产指标——孵化率,而孵化率的高低在很大程度上取决于种公鸡授精能力的好坏(母鸡繁殖器官病变或异常等情况也会影响受精率),所以种公鸡饲养管理的好坏是决定母鸡饲养效益回报高低的主要因素之一,同时种公鸡饲养管理的好坏对其后代生产性能的影响也是极其重要的。要培育生长发育良好、体格健壮、体重适宜、性成熟适时、精液品质良好、交配能力强的种公鸡,必须根据公鸡的生理及行为特点,有针对性地做好有关的饲养管理和选种工作。1公鸡断喙、断趾和剪冠公…     

鸡传染性法氏囊病诊断与防制的研究

鸡传染性法氏囊病(Infectious bursal disease,IBD)是由双RNA病毒科、禽双RNA病毒属传染性法氏囊病毒引起幼鸡的一种急性、高度接触性、     

安徽省鸡传染性法氏囊病流行病学初步调查

应用RT-PCR诊断方法,对2003年9月~2005年3月间来自安徽省不同地方的52个鸡群,共154羽病/死鸡的法氏囊样品进行了检测。结果表明,传染性法氏囊病(IBD)在安徽各地普遍流行,所有检测病例的平均阳性率为40.91%。不同的日龄段平均阳性率差异极显著(P<0.01),其中30日龄以下阳性率最高(35/75),60日龄以上阳性率最低(0/16)。不同品种的鸡均可检测出IBDV,品种间阳性率差异显著(P<0.05),其中江淮麻鸡阳性率最高(25/45),土鸡阳性率最低(3/15)。不同地区的病例均检测出IBDV,但阳性率差异不显著(P>0.05),其中合肥地区阳性率最高(23/47),宣城地区阳性率最低(5/18)。     

Challenge study on infectious bursal disease in chicks derived from vaccinated hens

Presence and levels of maternal antibody (MA) in broiler chicks derived from hens vaccinated with a live infectious bursal disease (IBD) vaccine were investigated by a quantitative agar-gel precipitin test. At day old 100% of the chicks tested had MA; by 17 days of age it was present in only 10%. The mean MA level at day old was 337.5 UK units/ml but decreased to 6.3 UK units/ml at 17 days of age. Randomly selected chicks from the pool studied were challenged at weekly intervals from day old for 29 days with an IBD virus obtained from a natural outbreak. Subclinical and clinical disease were observed in chicks challenged at eight and 29 days of age respectively.     

Exotic Newcastle disease in a game chicken flock.

A sudden increase in mortality, preceded by a short history of respiratory signs and diarrhea, occurred in a backyard flock of 48 game chickens in the Central Valley of California. Necropsy findings included severe generalized linear hemorrhages and/or ulcers in the digestive tract, larynx, and trachea. Histology revealed severe multifocal hemorrhages and necrosis in the mucosa of the respiratory and digestive tracts, vasculitis, and necrosis of lymphoid tissue. The birds were serologically negative to Newcastle disease virus; this was consistent with an acute infection. The avian paramyxovirus type 1 isolated was characterized as velogenic viscerotropic Newcastle disease virus. A thorough epidemiologic investigation was carried out, and no other premises were found to have birds with clinical signs or evidence of exposure. The entire outbreak was limited to the original backyard flock and resolved within 14 days of the onset of clinical signs.     

鸡传染性法氏囊病与球虫病混合感染的诊疗报告

广东省汕头市潮南区两英镇一养鸡户饲养的麻鸡在33日龄时,发生了以精神沉郁、闭目呆立、羽毛松乱、行动迟钝、怕冷打堆、排带有白色红色相间的水样稀便为主要症状,以法氏囊肿大,囊腔内有奶油状物、干酪状物或覆盖着果酱样粘液,两条盲肠高度肿大,肠腔内充满凝固的或新鲜的血液为主要病变的传染病。根据流行病学调查、综合临床症状、病理变化,初步诊断为鸡传染性法氏囊病与球虫病混合感染,后经实验室检查,确诊。经采取综合性治疗措施,取得良好的效果,现将诊疗情况报告如下:1发病情况广东省汕头市潮南区两英镇一黄姓养鸡户,于2004年5月14日购进…