Control of infectious bursal disease in broiler chickens

传染性法氏囊病（IBD）是一种由伯纳病毒科病毒引起的未成熟鸡的急性高度传染性传染病。它的特点是破坏法氏囊（BF）的淋巴细胞，损害免疫系统并引起免疫抑制。该病是世界各地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，因此一旦鸡舍受到污染，这种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包括肉鸡种鸡亲本疫苗接种计划，有效的鸡舍清洁和消毒计划，以及在许多地区，肉鸡疫苗接种计划。育种者的免疫接种是IBD控制计划的重要组成部分。母鸡产生的抗体通过鸡蛋传递给肉鸡。这些母源抗体，如果存在足够的水平，可以保护雏鸡免受许多田间ibdv的感染。由于在萨斯喀彻温省大量肉鸡舍中发现了IBD病毒的“变异”株，IBD的控制变得更加复杂。“变异”病毒破坏BF，即使是接种了疫苗的母鸡产下的小鸡。“变异”菌株不会引起明显的临床疾病，但可引起严重的免疫抑制。变体ibdv不是IBD的不同血清型，但它们在抗原性上不同，即使在接种良好的育种者的肉鸡中也会引起免疫抑制。加拿大使用的IBDV疫苗是以美国IBDV毒株为基础的，其对加拿大IBDV野毒株的有效性尚未进行调查。因此，本研究旨在为肉鸡及其亲本鸡群确定适当的疫苗接种方案，以控制IBD，减少免疫抑制和相关的继发疾病。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细菌的出现。

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.