Control of infectious bursal disease in broiler chickens

传染性法氏囊病（Infectious bursal disease，IBD）是由双RNA病毒科病毒引起的鸡的一种急性高度接触性传染病。 其特征在于破坏法氏囊（BF）中的淋巴细胞，从而损害免疫系统并引起免疫抑制。该病是全世界家禽生产区的一个主要问题。由于IBD病毒对许多消毒剂和环境因素具有耐药性，一旦禽舍被污染，疾病往往会在随后的鸡群中复发。有效的IBD预防和控制计划通常涉及肉鸡育种者父母接种计划，有效的畜舍清洁和消毒计划，以及在许多地区，肉鸡接种计划。种禽免疫是IBD控制计划的重要组成部分。母鸡产生的抗体通过鸡蛋传给肉鸡。这些母体抗体，如果存在足够的水平，可以保护小鸡免受许多野外IBDV的感染。在萨斯喀彻温省的大量肉鸡舍中，IBD病毒的“变异”株的识别使IBD的控制变得复杂。“变异”病毒损害BF，即使在来自接种良好的母鸡的雏鸡中也是如此。“变异”菌株不会引起明显的临床疾病，但可诱导严重的免疫抑制。变异的IBD病毒不是IBD的不同血清型，但它们的抗原性不同，即使在来自接种良好的种鸡的肉鸡中也会引起免疫抑制。加拿大使用的IBDV疫苗是基于美国IBDV毒株，其对加拿大IBDV田间毒株的有效性尚未研究。因此，拟定的研究旨在确定肉鸡及其亲本鸡群的适当疫苗接种程序，以控制IBD并减少免疫抑制和相关的继发性疾病。预防与免疫抑制相关的继发性细菌性疾病将导致最大限度地减少抗生素的使用和抗生素耐药菌的出现。

Infectious bursal disease (IBD) is an acute and highly contagious infectious disease of immature chickens caused by a virus that belongs to the family Birnaviridae. It is characterized by destruction of lymphocytes in the bursa of Fabricius (BF) which damages the immune system and cause immunosuppression. The disease is a major problem in poultry production areas throughout the world. Because the IBD virus is resistant to many disinfectants and environmental factors, once a poultry house becomes contaminated, the disease tends to recur in subsequent flocks. An effective IBD prevention and control program typically involves a broiler breeder parent vaccination program, an effective barn cleaning and disinfection program, and in many areas, a broiler vaccination program. Immunization of breeders is an important part of the IBD control program. Antibodies produced by the hen are passed through the egg to the broiler chick. These maternal antibodies, if present in adequate levels, can protect young chicks against infection with many field IBDVs. Control of IBD has been complicated by the recognition of "variant" strains of the IBD virus in significant number of broiler barns in Saskatchewan. "Variant" viruses damage BF, even in chicks from well vaccinated hens. "Variant" strains do not cause obvious clinical disease, but can induce severe immunosuppression. Variant IBDVs are not a different serotype of IBD, but they are antigenically different to cause immunosuppresion even in broilers from well vaccinated breeders. IBDV vaccines used in Canada are based on the USA IBDV strains and their effectiveness against Canadian IBDV field strains has not been investigated. Thus, the proposed studies are aimed at to identify proper vaccination programs in broilers and their parent flocks to control IBD and to reduce immunosuppresion and associated secondary diseases. Preventing secondary bacterial diseases associated with immunosuppression will lead to minimize antibiotic use and emergence of antibiotic resistant bacteria.