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

Abstract

Five QX-like infectious bronchitis virus (IBV) strains, isolated from different field outbreaks and two reference IBV strains of known serotypes (M41 and 793/B), were used in the present study to investigate and compare their pathogenicity for 1-day-old specific pathogen free chickens. The ability of the strains to inhibit trachea epithelium ciliary activity, to induce immune response, to replicate and to cause histopathological lesions in designated organs was followed by repeated samplings during a period of 42 days post infection. Clear differences in pathogenicity and in organ distribution of the three serotypes were found. Strain 793/B had the least capacity to invade the investigated organs, while it produced a good humoral response as measured by enzyme-linked immunosorbent assay. The QX-like strains generally replicated to higher titres, although differences were found among the five strains in their pathogenicity and affinity for different organs. The Chinese isolate of QX-like virus caused the most severe lesions and induced the highest antibody titres. Severe kidney damage and dilatation of the oviduct were the prominent lesions that could be related to the QX-like IBV strains, although neither marked virus replication nor histopathological lesions were detected in the oviduct.

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

“…One of these variant IBV genotypes, named QX, has been associated with respiratory problems, nephritis, drops in egg production and 'false layers' syndrome (Landman et al, 2005;Benyeda et al, 2009). In Europe, a QX-like strain was first detected in November 2003 by the GD (Dutch Animal Health Service) in an 18-day-old Dutch broiler flock that was suffering from nephritis.…”

“…Broadfoot et al (1956) reported that ''recent observations with experimental groups of chicks from bronchitis immune and non-immune sources indicate that passive immunity may protect the young chicks from the development of abnormal oviducts when exposed to a virulent field strain of IBV''. In the years after this publication, several other groups reported their results on the induction of false layers or cystic oviducts, but only in SPF birds (Crinion et al, 1971a, b;Crinion, 1972;Crinion & Hofstad, 1972;Jones & Jordan, 1972;Benyeda et al, 2009) or in commercial chickens without MDA (Broadfoot et al, 1956). It cannot be excluded that the present authors are unaware of some relevant, missed publications, but it seems apparent that the amount of accessible work regarding the role of MDA in the prevention of the induction of false layers by IBV is limited.…”

“…It has been reported for only a few IBV strains that they are able to cause false layers (Crinion & Hofstad, 1972;Chew et al, 1997;Benyeda et al, 2009). False layers have been induced in very young chicks using several Mass strains, an Australian T strain and several QX strains (Crinion et al, 1971a, b;Crinion & Hofstad, 1972;Jones & Jordan, 1972;Benyeda et al, 2009).…”

“…False layers have been induced in very young chicks using several Mass strains, an Australian T strain and several QX strains (Crinion et al, 1971a, b;Crinion & Hofstad, 1972;Jones & Jordan, 1972;Benyeda et al, 2009). Field observations also suggest that only a small minority of the IBV strains are able to induce false layers, as there are many new types of IBV detected every decade, without any indication of the appearance of false layers related to the detection of these new types of IBV.…”

Survey indicates circulation of 4/91 and QX-type infectious bronchitis viruses in Hungary in 2014 — Short communication

“…The QX-type IBVs have spread all over Europe and become a predominant strain (Terregino et al, 2008;de Wit et al, 2011), although so-called European QX strains are quite rarely associated with kidney problems (Worthington et al, 2008). In Hungary it was first reported in 2008 (Benyeda et al, 2009). …”