Today, as ever, if you ask any producer to name the most significant cause of egg production problems, IB is still likely to top the charts, being rivalled only by feed problems as the number one candidate.
The IB virus has been known about for over half a century and remains with us into the new millennium. Since its first isolation, there has been much research and much money spent on understanding how the virus works and how we might control it. Wherever poultry are produced, the IB virus can lose us birds, performance, eggs and money.
IB infection is certainly capable of causing egg production drops with or without a seconds problem and increasingly without respiratory signs or complications. Frequently, there may be an associated increase in mortality, mainly through peritonitis. Peritonitis is not unique to IB infection, but can occur if the egg laying cycle is suddenly interrupted.
Keeping things in perspective, we must always remember that not all drops in production will be due to IB infection. As in many areas of production these days, things are never that simple. There are a whole range of factors that can affect production, some to do with disease, some management, and some that just leave us scratching our heads.
In the case of IB we are increasingly talking about new variants or new strains of the virus, some of which may or may not be covered in our conventional vaccination programmes. Like any good HACCP programme for disease control, you need to know the real cause before you can establish your effective critical control points (CCP’s). It really is a case of know thy enemy!
In the case of IB (and as covered more recently in Ranger articles), the most important weapon for diagnosis of infection is a structured approach to blood sampling and testing. Firstly, blood sampling can help to judge how well your birds have responded to the IB strains you have had your birds vaccinated against. Secondly, further sampling can help tell you when birds have been challenged with a field strain, and in many cases, with which strain. Whereas this may not always enable you to wave a magic wand over your current flock, it can give useful pointers for preventative action in the future. It also helps you and other producers to know what viruses are active in your particular area.
Part of the confusion over the clinical and production problems attributed to IB infection lies with the emergence of the so called new strains or variants. One of the reasons IB manages to stay ahead of our best endeavours is this ability to generate these strains. Some are probably very close relatives to the classical M41 strains but it is the more distant cousins that come to visit and spoil the party. Carrying this analogy a bit further, the IB "family" consists of the following:
M41 – the grandfather! The classical strain on which most of the standard vaccines have been based.
D274 & D1466 – closely related Dutch visitors which appeared in the 1980’s, left home, and come back to visit from time to time.
793B - Part of the family but acting like a very distant relation.
4/91 & CR88 - Other names for the 793B variant or a set of identical triplets with it.
42/96 & 288/98 - Newcomers to the family appearing to be throwbacks to some previous generation or simply more new offspring.
This family seems to be constantly growing with new members appearing, some being too closely related to classical strains or so mild as to hardly be noticed, others are capable of causing significant problems.
So where do we go from here?
- Firstly, be as sure as you can be of your diagnosis. Don’t assume all egg drops are IB, even if the shape of the dip in production looks "IB like".
- Use blood testing as part of your veterinary health plan to help monitor vaccination, protection and disease challenges.
- Pay attention to vaccination techniques. Just because you have been vaccinating birds for many years, don’t assume you are automatically assured of always doing it right.
- Liaise with your pullet supplier as to the most suitable vaccination programme to protect your birds on the laying site bearing in mind the likely challenges in your area, whilst appreciating the logistics and planning the rearer needs to do to comply with this.
- Use the vaccines we do have in the most effective programme. There is work to suggest that using a combination of live IB vaccines in rear can lead to a much broader protection against many of the "family members" in lay. This then needs to be built upon with dead vaccine prior to lay.
- There is also some evidence that "topping up" this protection with the use of live IB vaccines during lay can help to spread this protection still further. Speak to your vet about the best programme for your birds.
- Appreciate that new variants of IB will continue to arise and vaccination programmes will need to evolve to cope with this. However, remember that the vaccine companies are beavering away trying to keep ahead of the game producing new vaccines to answer the questions of new variants, as well as hoping to improve the efficiency of the vaccines we already have.
- Although we don’t have all the answers to IB control, we do have a number of tools at our disposal, and using these techniques will give you the best chances of gaining good performance in your birds.
