Esta Página en Español

Esta Página no Português

Infectious bronchitis virus variant D388 (QX)

Introduction

Since 2004, severe egg production problems have been reported in The Netherlands in several farms housing different breeds of chicken (broiler and layer breeders and commercial layers). Respiratory signs are reported in broilers older than 4 weeks of age. In birds in production the problems are characterized by a low production rate with peak levels reaching only between 30% to 55% in apparently healthy flocks. Some of the birds show a peculiar stance (penguin-like) and a pendulous abdomen. These cases were associated to earlier outbreaks of nephropathogenic infectious bronchitis that had occurred in 2003 in broilers and pullets (layer and broiler rearing pullets) from which a variant IB virus, called D388 by the Animal Health Service in Deventer, the Netherlands, was isolated. Using a PCR test it was demonstrated that this isolate could be classified with 99% genotypic agreement as a Chinese isolate called “QX” and this is the name by which this IB variant is now known.

When this isolate was inoculated into both SPF and commercial birds it was shown to be nephropathogenic and could also be detected in the oviducts of the infected birds.

This IB virus has continued to be a cause of major disease problem in poultry flocks in some parts of Europe, being associated with nephritis and so called “false layers” as a result of early infection with this virus.  In a recent survey using the RT-PCR technique (Worthington, KC et al, 2008). The QX IB variant has been detected frequently in the Netherlands, Belgium, Germany and France, but not in UK or Spain.

Post mortem examinations of affected chickens

Necropsy of birds infected with the QX virus frequently show either cystic oviducts with watery contents that could exceed one litre or (partially) atrophic oviducts with large cystic dilatations. The walls of the oviduct are thin and transparent in the cystic areas. The ovaries in the birds are functional and look normal.

Click on the following thumbnails to see photographs of the above lesions:

Protection

Initial experiments carried out at the Animal Health Service in Deventer showed that a single application of a live vaccine of the Massachusetts serotype does not confer sufficient protection against challenge with the D388 isolate. Better protection is achieved when vaccines of other serotypes are included in the vaccination program. For example, giving an initial vaccination at 1 day of age with a live Massachusetts type of vaccine (for example Nobilis IB Ma5) followed by revaccination at 14 days of age with a live vaccine of the 4/91 type. This reinforces the importance of the concept of protectotypes (for more information see Serotypes and protectotypes).

Experimental Challenge 28 days post vaccination with IB isolate D388: Percentage of ciliostasis score

Protected = < 50%
Unprotected= >50%

The birds were vaccinated at one day of age with Nobilis IB Ma5 and Nobilis IB 4/91 and were challenged at 28 days of age. The vaccinated group shows an excellent protection level against a challenge with IBV D388.

References

Beato MS, De Battisti C, Terregino C, Drago A, Capua I, Ortali G. (2005).
Evidence of circulation of a Chinese strain of infectious bronchitis virus (QXIBV) in Italy.
Veterinary Record, 2005, 156:720.

Davelaar FG, Kouwenhoven B, and Burger AG (1984)
Ocurrence and significance of infectious bronchitis virus strains in egg and broiler production in the Netherlands. Veterinary Quarterly(1984), 6, 114-120

Dolz, R., Pujols, J., Ordóñez, G., Porta, R. & Majó N. (2007).  Molecular epidemiology and evolution of avian infectious bronchitis virus in Spain over a fourteen-year period. Virology, 12, 20.

Landman, WJM, Dwars RM, and de Witt JJ (2005). High incidence of false layers in (re)production hens supposedly attributed to a juvenile infectious bronchitis virus infection
Proceedings of the fifty-fourth Western Poultry Disease Conference,
Vacncouver, Canada, 25-27 April, 2005

Worthington, K. J., Currie, R. J. W.  & Jones, R.C. (2008). An RT-PCR survey of infectious bronchitis virus genotypes in Western Europe from 2002 to 2006. Avian Pathology, 37

Top of page

Some chickens infected with IB variant D388 (QX) show a penguin like stance with a pendulous abdomen.