Solutions for IBD Control Discussed in Marrakech

Every seat was taken in the hall for an evening seminar at the World Veterinary Poultry Association (WVPA) Congress 2009 organised by Merial and entitled 'A Unique Solution for IBD Control'. The high level of participation was a reflection of the difficulties encountered by farmers and veterinarians in the control of Infectious Bursal Disease (IBD; Gumboro disease) and their thirst for knowledge on new solutions, reports Jackie Linden for ThePoultrySite.
calendar icon 3 March 2010
clock icon 9 minute read

As an introduction, Jean-Louis Crosia, the head of the Europe, Middle East and Africa region at Merial, gave a brief overview of the company's history. Following the founding of the first veterinary school in Lyon, France, in 1761, innovator Charles Mérieux set up the world's first industrial production of veterinary and medical vaccines in the city in 1947. Now, Merial forms part of the so-called 'Lyon Cluster' of companies working on the control of infectious diseases.

Dr Jean-Louis Crosia

Khalid Tadlaoui

Looking to the future, Dr Crosia predicts the growing importance of vector vaccines, because they are more efficient and have fewer side-effects. The first such vaccine was against rabies, and the H5 avian flu vaccine, Trovac, is another example.

Dr Crosia added that Merial offers not only vaccines but also a range of services to support the products.

Khalid Tadlaoui, CEO of MCI Santé Animale, the first vaccine producer in Morocco, emphasised the importance of service to its customers. When he started working with Merial, he realised the development of proper methods for vaccine administration is vital for good protection, as is ensuring that the equipment remains in good condition.

Dr Crosia explained that Merial launched Vaxxitek for the control of IBD in Brazil four years ago and since then, 4.4 billion birds across the world have received the vaccine.

Taking centre stage next was François-Xavier Le Gros, director of research for Merial Avian, who explained why Merial saw the development of an IBD vaccine as a top priority.

IBD is a viral disease of young chickens, he said, which attacks the lymphoid system, targeting the bursa of Fabricius. In acute cases, the bursa develops haemorrhages or oedema, and mild cases reduce performance.

Vaccination is more-or-less unavoidable, he said, but the first vaccines were produced in eggs and were too 'hot'. Later, there was a wider variety of vaccine strains, and breeders were also vaccinated to protect their progeny with maternal antibodies.

But the problems with classical IBD vaccination, explained Dr Le Gros, were the difficulties of balancing safety and efficacy, and the immunity gap. This is the period between the end of protection for maternal antibodies and the effective response to the classic live vaccines, which makes it complicated to decide on the right timing for vaccination. Furthermore, proper oral vaccination is hard to achieve and it requires a lot of work, he said.

Dr François-Xavier Le Gros

Dr Francesco Prandini

The solution was found in vector technology, using turkey herpes virus (HVT) with the viral protein 2 gene of IBD virus inserted to induce immunity.

Dr Le Gros outlined the advantages of such a vector vaccine:

  • a single vaccination is all that is required, without any immunity gap
  • vaccination in the hatchery – automatically in ovo on day 18 of incubation or in day-old birds with the Marek's disease vaccine
  • protection continues throughout life, which is important for laying hens
  • broad protection against all IBD virus strains, including classical, very virulent and variants, as well as against Marek's disease.
  • there is no safety/efficacy dilemma, as shown by similar bursa scores for vaccinated and uninfected birds.

Finally, Dr Le Gros mentioned the two tools that are necessary to manage vaccination. The first is a simple serological monitoring, using ELISA, to measure seroconversion. This differentiates birds that have been vaccinated with Vaxxitek from those that have been vaccinated with classic vaccines or have been infected with the IBD virus. Second is a quantitative PCR method, which has been specially developed by Merial to detect Vaxxitek in feather follicles or in other tissues.

Summarising a number of trials with Vaxxitek, Dr Francesco Prandini (Merial's regional technical services director) began by explaining that the IBD virus is widespread across the globe. The World Organisation for Animal Health (OIE) estimates that more than 95 per cent of its member countries see the disease, mostly in the acute form, while the sub-clinical form occurs in the USA, Australia and other countries.

The virus targets the bursa of Fabricius, which he described as "the cornerstone of the bird's immune system". The severity of disease depends on the virulence of the strain (classical, variant or very virulent), the immune status of the bird and finally, its genetics. Layers may have mortality up to 50 per cent while economic losses from poor performance are a more likely consequence in broilers.

Dr László Körösi

Early efficacy trials with Vaxxitek showed very good protection against the IBD virus in SPF birds, said Dr Prandini, and total protection was achieved with subcutaneous or in-ovo application. In efficacy trials with commercial broilers, the vaccine offered complete protection from seven days of age.

For IBD vaccines, a useful measure of efficacy is to calculate the ratio between the weight of the bursa of Fabricius and bodyweight. Challenge with the E variant from the US, in chickens vaccinated with Vaxxitek did not affect this ratio compared to unvaccinated birds.

Protection was also found to be complete following a challenge with a very virulent strain of the IBD virus, which emerged in Europe in the 1980s and can cause up to 50 per cent mortality.

Furthermore, Dr Prandini said, the vaccine has been proven to be effective when applied in ovo. Under semi-commercial conditions, Vaxxitek administered in the hatchery gave good IBD protection compared to a live vaccine given in the water in an industrial farm. Finally, efficacy of the vaccine in layers has been demonstrated as full protection against clinical signs and mortality and by comparing the size of bursa. The bursae of Vaxxitek-treated hens were larger than those of unprotected and infected birds, as well of those receiving the live vaccines.

Dr Cleber Martins

Dr Antonio Carlos Pedroso

Dr Clovis Oliveira

The seminar then moved on to a roundtable session, where several 'Vaxxitek pioneers' had come from all over the world to share their experiences with the unique vaccine.

"We found that broilers vaccinated with Vaxxitek performed much better – a difference of eight per cent in the European Performance Index (EPI) – compared to vaccination with an IBDV antigen antibody complex vaccine used during previous cycles at the same five broiler farms," said Dr László Körösi, a poultry consultant from Hungary.

This was followed by testimony from France, where the performance of slow growing and 'label' birds was also better with Vaxxitek than live IBD vaccines.

In Italy, savings of 1.25 Euro cents per kilo of bodyweight were made when using Vaxxitek, amounting to almost €30,000 for one million birds.

Sergey Pilipenko of Agromars, the second largest broiler company in Ukraine, commented on the two- to three-gramme increase in daily weight gain since they started using Vaxxitek and a halving of the condemnation rate.

Brazil is the country where Vaxxitek was first launched and it has the greatest experience with the vaccine. More than one billion broilers have already received the vaccine there.

"We are delighted with the improved ease of administration and the consistency in vaccination," said Dr Cleber Martins, poultry production manager of Perdigão.

"We no longer have the 'drinking water headaches' and the uniformity of vaccination has led to improved uniformity of the animals," added Dr Antonio Carlos Pedroso, Sadia's poultry veterinary manager.

"Field trials in more than four million broilers comparing Vaxxitek with an IBD antigen-antibody complex vaccine has shown a clear difference in average weight at slaughter, feed conversion, mortality, condemnation rates and EPI, leading to a lower production cost and improved return on investment," said Dr Clovis Oliveira, Merial's head of avian business in Brazil.

He added that Vaxxitek has also been used successfully in more than 70 million layers in Brazil, which represents a 45 per cent penetration of the layer market.

Dr Sjaak de Wit

Professor Mohammed El Houadfi

Despite the widespread use of live vaccines, there were several IBD outbreaks on layer farms in the Netherlands in 2007 and 2008. As a result, field trials with the new vaccine were carried out under conditions of high viral pressure, reported Dr Sjaak de Wit, poultry expert at the Animal Health Service at Deventer.

He said: "The vaccine's potency was confirmed by serology, while we found an average bursa-to-bodyweight ratio around 4.5 to 5 – much higher than we tended to find in live-vaccinated layers. Furthermore, the histological lesion score was zero, which is really good."

Last but by no means least, Professor Mohammed El Houadfi of the Agronomy and Veterinary Institute in Rabat gave an overview of his experience with Vaxxitek.

He said: "Besides being an excellent vaccine against IBD with a very high safety and potency profile, Vaxxitek is also clearly of benefit to the bird's immune system." Field trials in Morocco also showed enhanced antibody response to Newcastle disease vaccines compared to a vaccine protocol with an IBD intermediate vaccine, he said.

It was left to Dr Frank Milward, director of R&D for Merial in the USA and the event moderator, to sum up the evening's seminar. Vaxxitek is the first vaccine using new technology, he said, and it is still a unique product. It can be used in many regions of the world, for chickens of different ages, and it is applied in the hatchery, subcutaneously or in-ovo.

"Vaxxitek improves bird quality, it protects the bursa of Fabricius and it strengthens the immune response to other disease," Dr Milward concluded.

Merial Symposium speakers

Further Reading

- You can view other reports from events organised by Merial at the WVPA Congress 2009 by clicking here.

Further Reading

- Find out more information on infectious bursal disease (IBD) by clicking here.

February 2010
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