In July, Poultry Business held a virtual round table discussion, sponsored by Boehringer Ingelheim.
PB editor Chloe Ryan was joined by a panel of experts to discuss what factors determine an optimal
vaccination programme for commercial poultry
PHILL CRAWLEY – Egg producer and packer from Leicestershire, free-range and colony birds
GREG KOULIANOS – Poultry clinician, head of veterinary services at Moy Park
DANA SIMPSON – Poultry vet, St David’s Poultry Team, based in Northern Ireland, working mainly with
commercial layers, plus some broilers and breeders
MICHAEL CLARK – Veterinary advisor for Boehringer Ingelheim, and head of pathology and public health for Nottingham Vet School
ALEX MCDANIEL – Veterinary advisor for Boehringer Ingelheim
Disease threats are continually evolving. New strains of viruses emerge all the time, and commercial poultry producers and their vets must be alert to the risks. As well as the hugely costly and damaging outbreak of avian influenza over the past year, new strains of diseases such as infectious bursal disease (Gumboro) have been identified in the UK, and the rise of pathogenic and opportunistic bacteria such as certain species of Enterococcus are on the rise.
So, what things need to be considered when planning vaccinating schedules for commercial poultry? Poultry vet Dana Simpson says while there are differences depending on the type of bird and specific disease risks of the location, most producers have similar priorities. They want to protect the birds against disease, protect the reputation of the industry, and protect the reputation of the end product.
GETTING THE MOST FROM THE BIRD
Whether broilers, layers, or breeders, vaccination is about getting the most out of the genetic potential of the bird. As we know sick birds often have reduced egg production so as Simpson points out “keeping birds on the right track with an appropriate vaccination schedule is one the roles of a poultry vet”.
The schedule, which usually includes vaccines against Marek’s disease, coccidiosis, Gumboro disease, Newcastle disease, infectious bronchitis, and Salmonella, must be paced appropriately so the birds don’t get put under too much stress. “You must allow sufficient time between vaccines to allow birds to develop immunity,” says Simpson.
“If you crowd the vaccine schedule too much you overwhelm the juvenile immune system and you don’t get the response you are looking for.
“We don’t go in all guns blazing; if it is not necessary, and you are putting the birds under too much pressure,” she says. “But going in too sparsely means you are leaving them potentially vulnerable.”
It is a process of constant refinement, she says. “If there are any signs or concerns, we review the schedule and add in an appropriate vaccine.”
Continued surveillance of vaccine efficacy, disease pressure and the geographical prevalence of disease strains provides important information which allows us to mitigate potential issues through adaptation of the vaccination schedule.
HEALTH AND ECONOMIC PRIORITIES
Health and economic priorities differ depending on the type of bird. “As a general rule, with longer lived birds there are significantly more diseases you would vaccinate for compared to broilers for example which are shorter lived,” says Alex McDaniel, veterinary advisor to Boehringer Ingelheim.
“It is a cost benefit analysis of course,” she adds. “Margins are tight.” Choosing the number and type of vaccine is partly dependent on the type of production system. For example, with inactivated vaccines administered on the farm, there is the labour cost of picking up each bird and vaccinating them. “That is something that
has to be taken into account.”
BELT AND BRACES
Leicestershire-based Phill Crawley, of Sunrise Eggs, has adopted what he calls “a strong vaccination programme, against multiple potential disease challenges such as Gumboro.”
Gumboro is highly infectious and causes immunosuppression, making birds vulnerable to other illnesses. He operates a multi-age site, which means he needs to take a belt and braces approach to vaccination. “As a producer packer we need to have a guaranteed flow of egg to our customers, so while it would be nice to have a single age site, it is not feasible to do that.
“I think as a shed gets older it becomes more difficult to maintain levels of production. Our new buildings could get away with a less comprehensive vaccine programme, but I think, ‘I’m happy with that, so why would I want to
“I am a big believer in spending a little more on vaccines if it pays the dividend at the other end. Protection is better than cure and there is a limited amount of antibiotic available to us in the laying industry, and an ongoing responsibility to minimise its use.”
Crawley says the comprehensive vaccination programme for his hens means he gets better end of lay shell quality and can extend the laying period to 80 weeks. He acknowledges this is partly due to genetic improvements with the birds alongside a comprehensive well administered vaccination programme.
Greg Koulianos, head of veterinary services at Moy Park, says the key factors when trying to optimise a vaccine schedule are the species of poultry you’re dealing with and the specific pathogens prevalent in the region. “For our breeding stock we design a vaccination programme that will protect our birds against pathogens during their production cycle but also will pass on immunity to their progeny by means of maternal antibodies. Therefore we strategically apply a series of live vaccines followed by inactivated vaccines. On occasions we may prepare a farm specific autogenous vaccines to deal with more targeted challenges.
“For our broiler birds the vaccination programme is aiming to protect the birds during their life and ensure their optimum health, welfare and productivity.”
Moy Park is continually monitoring the birds to evaluate the efficacy of the vaccination schedules as well as potential disease prevalence in each geographic area. A recent example is the discovery last year of ILT in
Northern Ireland, after an absence of the disease for many years.
“We suddenly saw an increase in cases last year in the last quarter. So, we started vaccinating. Our breeders have been vaccinated against ILT for a number of years but we started to vaccinate our broilers as well in areas where there was a hot spot taking advantage of our in-ovo facilities in our hatchery.”
Responding in this way helped suppress the emergence of the disease, and there are now very few cases. “Similarly, if we see emerging pressure from Gumboro we will tailor our programme accordingly,” he says.
Simpson also had to deal with the ILT outbreak on farms in Northern Ireland, where she works. “We tested everywhere that had symptoms, and we educated producers on how to look for certain traits of this disease.
“From a veterinary perspective, it’s very easy to say, ‘if you see critical signs give us a call,’ but sometimes it’s not clear what we are asking them to look for. You want people to recognise the early symptoms, before production has dropped and mortality has increased. We put a lot of emphasis on that. Then we go out and test
them with PCR and serology.
“Initially, we carry out on farm post-mortem examinations, if further diagnostics are required then PCR and serology come into play. It is important to try and stay ahead of any new strains of disease that are emerging, so the vaccine schedule can be modified if necessary.
“We do a lot of surveillance and monitoring of serotypes that are prevalent and assess whether
our vaccine schedule is covering against those,” says Simpson.
She works with pharmaceutical companies in routine infectious bronchitis programmes to look for circulating and emerging strains, and randomly selects certain flocks, which are tested at different ages from rear through to end of lay, to determine whether vaccination has been successful.
It is rare to see clinical cases of Gumboro, but the sub-clinical impact is important. It weakens the immune system of broilers and allows other bacteria and viral challenges to come through.
Northern Ireland, where Simpson works, has quite a low infectious clinical problem with Gumboro. This has allowed her to reduce vaccinations given to pullets to just one dose, administered between 25 and 28 days depending on vaccine prediction results and the disease pressure in certain geographical areas.
“We have done that now for years and it works very well. There are plenty of areas in GB that couldn’t do that,” she says. “They need two vaccine doses and would have to use a hotter strain than we do.
“We are not seeing extremely sick birds,” adds Simpson, with regard to infectious bronchitis. “We are seeing shell quality affected, maybe shell colour affected, possibly the birds not laying to their full potential. But when we tested those birds, we found the common denominator, which allowed us to go back to the vaccine
schedule and enhance protection.
“Overall, you are trying to balance out bird health and production and food safety.”
The picture in other parts of the UK on Gumboro is different. Koulianos cites a resurgence in certain field strains. “We routinely survey field strains,” says Koulianos. “There is a new strain of Gumboro, UK661, but also other new strains falling into this group.
Moy Park has in recent years invested in in-ovo vaccination to enhance protection of its breeding stock against Gumboro, and avoid the ‘immunity gap’ when birds have limited protection. “Our breeding stock is higher value
so there are significant investments when it comes to vaccine choices and application methods,” says Koulianos.
So effective has this been that the company has expanded this approach to two of Moy Park’s broiler hatcheries, where in-ovo vaccination systems have also been added.
“Our broiler birds have a higher level of protection coming from their parents because of their antibodies, so there is great confidence broilers are protected. But with field vaccination there is always the risk of an immunity gap when the maternally derived antibodies drop before the chick has time to mount its own immune
It is important to use hatchery administered IBD vaccines that generate immunity early enough to eliminate that gap.
Whether new strains of Gumboro, including UK661 are more pathogenic than previous strains was discussed by the panel.
“When it comes to genotyping it is classed as very virulent,” says McDaniel, “but what we don’t know at the moment is the true pathogenicity of it, because here and in Europe the industry has not yet conducted the true pathogenicity studies. So, the jury is out as to exactly how virulent these new strains are and until new work
is done in that area with challenge studies and pathogenicity studies we won’t know.”
While businesses such as Moy Park have embraced in-ovo vaccination to try and close the immunity gap, Crawley said the Gumboro vaccination programme he has for his birds is providing good levels of protection.
“I’ve been pullet rearing for just over two years. I’ve not seen an issue, so I’m doing the right job,” he says. “I have not seen any Gumboro issues to date, so hopefully our programme is giving the required protection.”
As well as diseases that cause clinical problems in birds, vaccinating against salmonella is something the egg industry needs to take seriously because of food safety. “What I worry about is with flocks living longer, they could potentially be more at risk of being infected later in life,” says Crawley, whose birds receive three live vaccines and an inactivated vaccine as standard. “Vaccine companies know that many of their products are effective to 72 weeks of life but birds are remaining in production for longer and longer.
“I would like to go up to 80 weeks on the brown feathered birds, so we need that protection.”
This presents a quandary. How do producers maintain the level of protection? “I don’t think it’s practical to give an inactivated vaccine to the birds individually during the laying period, but neither is it licensed to give a live salmonella vaccine during the laying period. Food safety is of paramount concern,” says Crawley.
For the past four years, Crawley has been using a combination of three live vaccines against Salmonella, using on veterinary advice a combination of Salmovac 440, plus Gallimune Se & St on transfer.
Simpson says that while vaccines are licensed for birds until a particular age, there is a possibility they last for longer. This would need to be assessed through trials. While the prevalence of Salmonella in longer living birds
may be higher, there are no definite figures, and there are fewer of those flocks around. “Re-enacting those trials is extremely expensive and takes a long time,” she adds.
“In Northern Ireland we have pushed the boat out and have several flocks that go to 100 weeks,” and Simpson recommends her clients use three live and an inactivated vaccine against Salmonella and finds this offers good
Alongside the vaccine schedule, she offers ‘nutraceutical support’, to help the birds’ gut health and minimise colonisation. “We are getting to the stage where we are going to have to push from several sides, we can’t just rely on the vaccine schedule, but I agree with Phill as we are moving on from where the vaccine schedule’s ability lies.”
It is also very important to maintain vermin and pest control.
The panel turned their attention to which vaccines would make a welcome addition to current schedules. Crawley said the time had come to consider vaccinating against avian influenza.
The 2021-2022 AI season has been tough for the UK poultry industry on all fronts and he has “never seen anything like it”.
“If we can do anything to protect the birds and the mental stress of the people who work with the birds, that is a good thing for both people and chicken. Obviously, it can’t put too much restriction on our market, but I think there are a lot of countries particularly after this year will look very differently at a vaccine than they would have done nine or 12 months ago.”
“I think it is something we need as an industry to look into,” he says.
While vaccines are available globally and the technology is there, deciding whether to embrace vaccinating against AI is, says Michael Clark, veterinary advisor to Boehringer Ingelheim, “for lots of governments a really
uncomfortable discussion to have, because AI is notifiable, so it is different from Gumboro or MD.
“There are serious implications if you decide to start vaccinating. But there could be a tipping point.”
In other parts of the world, birds are vaccinated against AI, so there are some options available. “There are vector vaccines, there are live vaccines, there are inactivated vaccines,” says Clark. “We need to have a discussion about
where we go from here because there is a question mark over whether the current control strategy is adequate.
“This year has been incredibly difficult, and I would be hard pushed to say to producers like Phill, ‘oh don’t worry, next year will be fine.’
We have got to seriously consider whether AI vaccines are made available, because we can’t go from October through to June with ongoing cases of AI in kept poultry. It is unsustainable.”
Koulianos also said it was time for the industry to start discussing avian influenza vaccinations. “I think we should consider it. The EU has approved the use of certain types of vaccine as a means to controlling the disease, so it has opened up experimenting and strategic ways of controlling the spread. We know other countries have stepped into trials of vaccine protocols, including France, the Netherlands, and Italy.
“Within the UK we ought to consider the options as part of an eradication strategy. There is no doubt that governments have to work very hard to make sure trade is not impacted but when it comes to tackling the disease, I think considering strategic vaccination should be part of this discussion.”
Moy Park is keen to take part in trials of avian influenza vaccinations, he says. “We have the facilities to trial a vaccination protocol, if that was permissible, in collaboration with the authorities.
“I appreciate a lot of discussions would have to take place about trading corridors, but when it comes to the safety of the vaccine we absolutely would like to collaborate with pharmaceutical companies and the authorities.”
ESSENTIAL PILLARS OF IBDV CONTROL
The panel discussed the factors other than vaccination that are important in protecting birds against disease and in particular IBDv.
“Biosecurity and vermin control is paramount,” says Simpson. “Vaccines are only one tool in the toolbox,” adds Crawley. “Biosecurity is key, rodent control is key. Every vaccine, no matter how well it is given, if the challenge is high enough, the vaccine will break down. And that is not the vaccine’s fault. You can’t just think because I’ve vaccinated, I’m safe. It is a multifactorial thing that has to come together. On a multi-age farm it is difficult because there can be spread between sheds, but biosecurity, rodent control, good staff discipline are all things that help. Vaccinations on their own are not the answer, it has to be multifactorial.”
“The vaccination programme is there to protect the health and welfare of the birds, but it will not be 100% bullet proof if there is a challenge from the environment to our sheds,” adds Koulianos. “So good biosecurity is paramount. Cleaning and disinfection programmes if we know a flock has been challenged by disease just to prevent that carry over into the following cycles, so both biosecurity and hygiene will be paramount to support the vaccination programmes.”
Clark emphasised the importance of correct vaccination technique: “The vaccines are there to enhance immunocompetence. When it comes to that helping hand, there is no point having the
best vaccine in the world, if you inadvertently kill that vaccine.
“Or if you jab a bird with a dirty needle and that bird dies of septicaemia you haven’t helped that bird out at all. Vaccine technique is so critical.”
Producers and vets need to consider whether they are best administering the vaccine in the hatchery either at day old or through in-ovo machine. The options on the farm are at what time in the bird’s life do you give the vaccine and how do you get that vaccine in the bird.
In the context of Gumboro disease for example, closing the immunity gap is key, says Koulianos. “By choosing hatchery application over on-farm vaccination and choosing the right type of vaccination you are really closing that immunity gap, and protecting those birds early and you don’t allow the field strains to come in.”
GETTING THE BASICS RIGHT
And when administering vaccines, getting the basics right is also crucial. “A lot of attention needs to be paid to not just the vaccine, but the storage and the transport,” says Simpson.
“Any process from when you have a vaccine out of the fridge to when it goes into the bird, needs to be done correctly. If you’ve killed the vaccine prior to administering it, you’re just getting water into the bird.”
Stress can also play a major role in bird health and stressed birds are more vulnerable to disease, adds Simpson. Heat stress is one problem, as are the lockdowns imposed to tackle AI, plus routine changes like transferring pullets from the rearing site to the laying site or coming into peak lay. “We pay close attention to stress management,” she says.
Crawley has been rearing his own pullets for the past two years, and he says this has helped reduce stress on his birds, as he is able to manage the transition smoothly. “We use a multi-tier system so the birds can adapt very quickly to the laying house, this reduces stress on housing the birds have a good bone structure and are used to living in a three-dimensional environment, it is a pleasure to see the moving confidently around their new laying system.”
Simpson adds parasite control is another crucial factor in ensuring the health of birds, reducing stress, and therefore allowing vaccines to work to their full potential.
“A lot of the time when birds are housed, people might think there might be a lower chance of worms, but that’s not true because the birds are closed up and the house temperature is higher, the humidity is higher, so the conditions are actually more suitable, so we see more issues with worm burdens in birds that are housed than the farmers expect. When the houses are closed up it can be 23-25 degrees and the red mite population thrives on that, which also contributes to stress,” adds Simpson.
IMPORTANCE OF HEALTH
Paying close attention to these factors will help ensure healthy birds that are more responsive to vaccines.
Simpson says: “That starts from the second they hatch, the brooding conditions on farm and how well they are started, making sure the chicks start well is key.
“That means the development of their immune system and intestinal system is optimal because we need them to be at optimal ability to respond to a vaccine.
“So, in addition to the cleaning and disinfection and everything that has been mentioned, it is the housing
conditions, the environmental conditions, the starting, the water and feed, the floor temperatures and everything surrounding the first week of life is optimal. Because if they don’t get a good start and then we start vaccinating them, their ability to mount an immune response may be affected.”
Clark concludes that the process of designing an optimal vaccination schedule will have to continue to be tweaked and refined in the years to come: “Whatever works now will need to be fine-tuned as the genetics of the birds changes, as the disease threats change, and public perception of disease threat changes. Most of the UK poultry population is very well vaccinated, but we will have to constantly evolve these vaccine schedules over the years to come.”