Michael Clarke, avian technical adviser at Boehringer Ingelheim Animal Health UK, explores the issues around vaccination for Gumboro disease
This article first appeared in the Poultry Business Innovation supplement
Isn’t it fantastic that broiler or pullet replacer chicks can hatch out with the capability of mounting an immune response against potentially fatal chicken diseases? Not only that, but there are also some clever clogs in laboratories that have developed vaccines to enhance bird immunity in the fight against serious disease. It all sounds so simple.
Firstly, hatch out some vibrant chicks with high levels of circulating maternal derived antibodies (MDA). What’s needed for that are some great parent stock birds where the hens can gift their chicks antibodies. These antibodies – which are pathogen specific – will remain in the chicks’ system for the first couple of weeks.
Infectious bursal disease (IBD) virus, which causes Gumboro disease, is one of the pathogens that everyone would want their chicks to have high levels of antibodies against. Secondly, it makes sense to top up those MDAs with some further antibodies, which the chicks can produce having been vaccinated with a commercially available IBD vaccine.
Where speed is of the essence and margins are tight, surely administering the cheapest vaccine as early as possible is the way forward. Guess what? It’s not that simple.
A poultry producer and their vet have the luxury of a plethora of Gumboro disease vaccines on the market. Taking the financial consideration out of the equation, there are two main points to consider: the potency of the vaccine in relation to the field challenge, and the impact the vaccine could have on the birds.
In the UK we have vvIBD virus circulating. The “vv” tells us the field viruses we encounter are upping their game and some are very virulent. It’s bad enough knowing these viruses that can cause serious disease are about, but we know that there are also new emerging strains.
The live Gumboro vaccines that tend to be administered to birds via the drinking water are great. We at Boehringer Ingelheim are proud of our live Gumboro vaccines, Gallivac IBD and Gallivac IBD S706 Neo. But whether an intermediate or a hot live vaccine is being administered, its effectiveness is very much predicated by whether it can break through MDA levels in the chick. Gumboro predication dates have been used for years to determine the optimal date for vaccination.
Alas with big sites, with numerous flock codes and split placement dates there is always the possibility that the elected vaccination date results in some birds having a gap between the diminishing of MDAs and the onset of vaccine antibodies. At the other end of the spectrum some birds may have such high levels of MDAs on vaccination day that the vaccine response is compromised.
Where this scenario is not acceptable it is possible to use vaccines in the hatchery irrespective of each bird’s MDA status. There are two options. Immune-complex Gumboro vaccines use the same vaccine strain seen in live Gumboro vaccines, but the vaccine strain is protected from MDAs. Once MDAs drop the immune-complex vaccine virus can start replicating in the Bursa of Fabricius (this is the organ involved in the maturation of B-cells and hence the development of antibodies). You know what’s coming – there is a “but”. These types of vaccines only start producing antibodies once MDAs have dropped quite low so there is an immunity gap.
Thank goodness for innovation. For some time we have known that vector vaccines are available, such as Vaxxitek.
These vaccines are administered in the hatchery too, but immunity is induced by a VP2 Gumboro insert on a HVT virus. This means, as a bonus, there is some Marek’s disease protection induced by these vaccines. Also, there is no immunity gap. The chick can have sky-high MDAs yet still the vaccine will get to work inducing an immune response.
Despite this rapid response there is little or no damage to the birds’ immune system. This appears to be the sweet spot where maternally derived antibodies and vaccinal derived antibodies can work in harmony. Virtually all commercial chickens are vaccinated for Gumboro disease, but are yours optimally vaccinated?