The remit of this review is to provide the non-specialist reader of Avian Pathology with an overview of research carried out on infectious bronchitis over the 40 years since the journal was first ...published. In order to do this, we felt it necessary to summarize the knowledge acquired previously, since the since the disease was first identified in the 1930s. Infectious bronchitis virus is a significant pathogen in the domestic chicken, affecting the respiratory and renal systems as well as the female reproductive tract. The virus exists in the form of many, ever changing, serotypic or genotypic variants, some of which have global distribution whilst others are found only in more local areas. This review mentions the major discoveries concerning both the virus itself and the types of disease it causes and considers recent changes in its pathogenesis. It also discusses the impact of developments in the field of molecular biology and highlights possible areas for future work.
The history, current situation and control measures for infectious bronchitis virus (IBV) variants are reviewed. A large number of IBV variants exist worldwide; some being unique to a particular ...area, others having a more general distribution. The possible reasons why some strains spread readily over major parts of the world, whereas other strains stay more localized are discussed. The advantages and disadvantages of strain classification by protectotyping, serotyping and genotyping are discussed in relation to in vivo protection. The different vaccination strategies are also considered.
The factors influencing the outcome of infectious bronchitis vaccination and challenge experiments regarding the respiratory and renal systems are reviewed. Advantages and disadvantages of the ...available techniques for measuring protection against an infectious bronchitis virus challenge are discussed, including the definition of protection itself. Suggestions are made regarding some ways in which progress towards standardization of a recognized protocol for performing experimental challenge studies can be made and areas where more work is needed are indicated.
Spotlight on avian coronaviruses de Wit, J. J. (Sjaak); Cook, Jane K. A.
Avian pathology,
07/2020, Letnik:
49, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Coronaviruses (CoVs) mainly cause enteric and/or respiratory signs. Mammalian CoVs including COVID-19 (now officially named SARS-CoV-2) belong to either the Alphacoronavirus or Betacoronavirus ...genera. In birds, the majority of the known CoVs belong to the Gammacoronavirus genus, whilst a small number are classified as Deltacoronaviruses. Gammacoronaviruses continue to be reported in an increasing number of avian species, generally by detection of viral RNA. Apart from infectious bronchitis virus in chickens, the only avian species in which CoV has been definitively associated with disease are the turkey, pheasant and guinea fowl. Whilst there is strong evidence for recombination between gammacoronaviruses of different avian species, and between betacoronaviruses in different mammals, evidence of recombination between coronaviruses of different genera is lacking. Furthermore, the recombination of an alpha or betacoronavirus with a gammacoronavirus is extremely unlikely. For recombination to happen, the two viruses would need to be present in the same cell of the same animal at the same time, a highly unlikely scenario as they cannot replicate in the same host!
Infectious bronchitis is a highly infectious disease of the domestic chicken of all ages and type, affecting the respiratory, renal and reproductive systems. Secondary bacterial infections are common ...and have a serious economic and welfare impact. Many genotypic and serotypic variants of infectious bronchitis virus (IBV) exist worldwide, making diagnosis difficult, and challenging control strategies. Vaccination, requiring the use of both live-attenuated and inactivated vaccines, is needed to control IBV infections; to date, attempts to develop vectored vaccines as effective as the traditional vaccines have been unsuccessful.
In an initial study in specified pathogen free (SPF) chickens, a heterologous virus neutralizing (VN) antibody response to IBV variants Q1, Variant 2 (Var 2), D388/QX (D388), D274 and Arkansas (DPI) ...was observed using a vaccination programme incorporating two different live-attenuated IBV vaccines, followed by boosting with an inactivated vaccine containing IBV Massachusetts (Mass) antigen. Therefore, a more detailed study was undertaken in SPF layer-type chickens primed with IBV Mass and 793B vaccines. The efficacy of single or repeated vaccination with a multivalent inactivated vaccine containing IBV antigen was determined against challenge with five virulent IBVs: Mass (M41), 793B (4/91), D388, Q1 and Var 2. The parameters assessed were serological response, respiratory signs, egg production, post mortem abnormalities in the reproductive organs and abdomen, and incidence of IBV antigen in kidneys. Increased VN titres were recorded against the five IBV challenge strains, with a significantly higher level of protection against drops in egg production following challenge. The difference between one or two vaccinations with inactivated vaccine was not significant in terms of egg production. However, a significantly increased level of protection was seen in the lower percentage of hens with free yolk in the abdomen and/or peritonitis post challenge with IBV variants, D388, Q1 and Var 2 not included in the vaccination programme. A lower incidence of acute, degenerated ovaries was found in groups given one injection of inactivated vaccine following live priming, and this was significantly lower than in groups given only live priming.
To achieve long term protection of laying and breeding hens against aberrant egg production caused by infectious bronchitis virus (IBV), a vaccination programme incorporating both live-attenuated and ...inactivated IBV vaccines is required. High quality IBV vaccines of both types are widely available, but the number of IBV variants of global importance continues to increase and it is not possible to develop vaccines against each one of them. Therefore, it is desirable to perform studies under controlled conditions to determine which IBV vaccine(s) provide the best protection for laying hens against different IBV challenges. Previous vaccination and challenge studies have shown that it is possible to obtain relevant data in a small number of laying hens housed under conditions of strict isolation. The present work extends this finding by investigating the efficacy, against challenge with five IBV strains of global importance, of an IBV vaccination programme including two live-attenuated IBV vaccines (Massachusetts and 793B types) and three different commercially available inactivated vaccines each containing antigen against at least one IBV strain. The results reported here confirm the importance of IBV vaccination for laying hens, show that efficient live priming makes a beneficial contribution to this protection and confirm that inactivated IBV vaccines contribute significantly to effective protection against at least the five IBV challenge strains used here. Furthermore, we provide data to support the "protectotype concept", long-established using different live-attenuated IBV vaccines in young chickens, is valid in broadening protection against IBV challenges in laying birds.
RESEARCH HIGHLIGHTS
IBV vaccination is essential as an aid in protecting laying hens against IBV infection.
Live priming is a beneficial part of the IBV vaccination programme.
IBV inactivated vaccine improves IBV protection.
Heterologous IBV protection is confirmed in laying hens.
The H strain of infectious bronchitis (IB) was one of the earliest live attenuated IB vaccines to be developed and has continued to be use in most parts of the world for almost 50 years. It was ...developed for used at both the 52nd (H52) and 120th (H120) vaccine levels and, because of it ability to provide heterologous cross-protection against a number of IB viruses of different serotypes, has proved to be one of the most enduring live attenuated IB vaccines. In fact, the H120 vaccine is possibly the most widely used live attenuated IB vaccine globally to this day. The use of H52 has, however, declined with the introduction of safe and highly efficacious inactivated IB vaccines. This review documents the original studies to isolate and attenuate the H strain by serial embryo passage, and describes the early studies to demonstrate its efficacy in laboratory studies and under field conditions. The efficacy of the H vaccine in providing cross-protection against some of the many IB variants now reported worldwide is also discussed, and possible future vaccination strategies for IB considered.
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