Pathogenicity of a QX strain of infectious bronchitis virus in specific pathogen free and commercial broiler chickens, and evaluation of protection induced by a vaccination programme based on the Ma5 and 4/91 serotypes

Abstract

The aims of this study were firstly to evaluate the pathogenicity of an Italian isolate of the QX strain of infectious bronchitis (IB) virus using 1-day-old female specific pathogen free chicks (layer type) and 1-dayold female commercial broiler type chickens, and secondly to assess the level of protection induced in these birds by a vaccination programme including the IB Massachusetts and 4/91 serotype live attenuated vaccines. Unvaccinated birds showed clinical signs of varying severity, predominantly affecting the upper respiratory tract. Vaccinated birds appeared healthy, with the exception of a very mild conjunctivitis affecting a limited number of the broilers. Vaccination fully protected specific pathogen free birds, since no histopathological lesions were observed, nor was virus detected following challenge. In broilers, replication of the challenge virus was not prevented but was significantly reduced. This study confirms that vaccination at 1 day old and at 14 days of age using the Ma5 and 4/91 IB vaccines may be instrumental in reducing the economic impact of QX IB virus infections in layer and broiler farms.

Comparison of the pathogenicity of QX-like, M41 and 793/B infectious bronchitis strains from different pathological conditions

“…type of IBV were found (reviewed by Fabricant, 1998). The majority of the previously unknown serotypes or variants, identified in the past two decades around the world, have either disappeared or become endemic in certain geographical areas (Bochkov et al, 2006), while some of them have become widespread and predominant in the majority of the countries with a significant poultry industry over a period of time (Terregino et al, 2008).…”

Induction of cystic oviducts and protection against early challenge with infectious bronchitis virus serotype D388 (genotype QX) by maternally derived antibodies and by early vaccination

“…Several groups have shown that a vaccination schedule using a live attenuated Massachusetts (Mass) vaccine at 1 day old, followed by a heterologous live attenuated IBV vaccine at 14 days, is able to induce considerable cross-protection against challenge with a QX field strain in young specific pathogen free (SPF) birds at 35 days of age Terregino et al, 2008). However, to prevent the induction of false layers, a high level of protection is needed at a very young age.…”

“…To achieve broad protection against damage caused by challenge with IBV variants at several weeks post vaccination, the use of different combinations of live IBV vaccines has been shown to be able to induce a high level of protection against challenges with several heterologous strains (Cook et al, 1999;Gelb Jr et al, 2005;Terregino et al, 2008), although the same combinations can be unsuccessful in inducing a satisfactory level of protection against other heterologous strains (Cook et al, 1999;Ladman et al, 2002). Several groups have shown that a vaccination schedule using a live attenuated Massachusetts (Mass) vaccine at 1 day old, followed by a heterologous live attenuated IBV vaccine at 14 days, is able to induce considerable cross-protection against challenge with a QX field strain in young specific pathogen free (SPF) birds at 35 days of age Terregino et al, 2008).…”

Systemic and local immune mechanisms stimulated in the course of chicken infectious bronchitis

“…Może to wynikać z faktu, iż pojedyncze mutacje nukleotydów w analizowanym genie S1 nie muszą wpływać na zmianę przynależności antygenowej IBV, a dodatkowo analiza przynależności genotypowej odbywa się jedynie poprzez analizę fragmentu genomu wirusa, nie uwzględniając przy tym udziału innych struktur immunogennych zaangażowanych w rozwój protekcji. Zjawiska te wykorzystywane są w terenowych strategiach uodporniania ptaków przed negatywnymi następstwami zakażenia IBV, w myśl definicji odporności protektotypowej, która zakłada, iż równoczesne wykorzystanie dwóch filogenetycznie niespokrewnionych szczepionkowych szczepów IBV skutkuje rozwojem protekcji krzyżowej w stosunku do szerokiej gamy geno-i serotypów wirusów IB (9,30,36). Immunologicznych podstaw skuteczności tej strategii uodporniania można dopatrywać się między innymi w fakcie, iż skutkuje ona silniejszą infiltracją komórek T CD8 + oraz produkcją wyższego poziomu IgA w GDO w porównaniu ze szczepionką monowalentną (6).…”