Infectious Bronchitis — variations on a theme

Infectious bronchitis (IB) was first described in 1931 in the USA as a respiratory disease of chicks. In the 1950’s egg production and egg quality problems were associated with IB infection and in the 1960’s a kidney problem was attributed to IB virus infection..

Since then IB has remained a significant problem for poultry producers all over the world affecting both meat and egg laying birds.

Once the virus associated with the early disease problems had been identified vaccines were produced to give protection to poultry flocks. Indeed many of the vaccines we use today are derived from the original IB virus isolates.

Unfortunately IB viruses tend to be ’one jump ahead’. As fast as vaccine companies produce vaccines to control a current IB problem a new IB variant virus pops up against which vaccine may not be effective. In Europe and the UK recent variants include IB793/B (also known as 4-91 or CR88), D274 and 42/96.

IB infection

In laying flocks IB or IB variant infection may cause a variety of symptoms. These include:

· Drops in production often with associated egg quality problems such as increased mis-shapes, rough shells, loss of shell colour and watery whites. (problems are usually most severe in young flocks at peak production and older flocks)

· An increased incidence of peritonitis following IB challenge.

· Respiratory symptoms – runny eyes, sneezing or coughing and sometimes swelling of the head.

· Kidney damage – this is uncommon now as most IB vaccination programs offer good protection.

Diagnosis

Your veterinary surgeon should be able to confirm whether your flock has suffered an IB challenge from the clinical history of your birds, post mortem and/or blood test results and in some cases from isolation of the virus.

Control

Reducing the risk of IB causing problems in your flocks relies on:

· Good biosecurity as discussed in a previous article – to reduce the risk of IB virus being introduced on to your site

· Good vaccination in rear and in lay to give optimum protection against IB and IB variants. Vaccines are not available in the UK to protect birds against all known IB variants but good vaccine cover with the existing IB and IB variant vaccines will help to give some protection. Your veterinary surgeon will be able to advise you on the best vaccination strategy for your flocks.

· Maintaining your flock in optimum health. If your birds are free from other infections, parasitic diseases and other ’stresses’ they will be better able to withstand any viral challenge. For example, an IB challenge is likely to have much more severe effects in a flock that is mycoplasma positive than in a mycoplasma negative flock.

· Good air quality. Fresh air will help to keep the respiratory tract healthy. High dust or ammonia levels will damage the respiratory tract and make birds much more vulnerable to respiratory diseases such as IB.

Conclusions

IB and IB variants will always be with us and it is likely that new strains will continue to appear to cause new problems. If you can maintain good biosecurity coupled with optimum flock health and a good vaccination policy you will go a long way towards controlling IB problems.