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Laura Villarreal, DVM

New approach needed for ND control

Laura Villarreal, DVM, Merck animal health, reviews the advantages of a recombinant vaccine for Newcastle disease

Q: How big of a problem is Newcastle disease (ND) in poultry production?

LV: Newcastle is one of the oldest diseases affecting poultry worldwide. When the virulent, velogenic form of this paramyxovirus strikes, mortality can exceed 80% to 90%. Even if chickens survive, they may have no value if they develop neurological signs and have to be discarded.

The milder, lentogenic form of ND can reduce broiler flock performance and cause economic losses due to condemnation for airsaculitis, especially when ND occurs along with other agents such as mycoplasmas, pneumovirus or secondary bacterial infections. In laying hens affected by ND, egg production drops.

Q: Tell us more about the economic consequences of ND.

LV: ND is probably one of the most costly diseases affecting the global poultry industry. Losses are obviously high when recurrent outbreaks result in widespread mortality and morbidity or they are associated with drops in egg production in layers and breeders. Other economic consequences result from restrictions on exports and commercialization.

Virtually all commercial poultry operations in the world need to vaccinate against ND — yet there is a high price for ND prevention with conventional protocols. Besides the cost of multiple live and killed vaccines, conventional programs require handling birds in the field, and they can cause post-vaccination reactions. These are stresses that adversely affect uniformity and weight gain in broilers and in layers, and can result in reduced egg production.

Let’s consider the world population of 61 billion commercial birds, which includes broilers and layers. If only one dose of a live ND vaccine is administered — and that would provide bare-minimum protection — the cost is about US $137 million. If you factor in the cost of additional vaccinations and the impact of post-vaccination reactions on performance, the cost is far, far higher.

Q: Are conventional vaccine programs effectively controlling ND?

LV: Conventional programs can provide good protection, but outbreaks still occur for many reasons. These include improper administration, immunosuppression, inadequate hygiene, poor biosecurity and ND field viruses that are very virulent.

Continued ND outbreaks coupled with the problems associated with conventional ND programs leaves producers eager for ND-control methods that are more efficient and convenient and that improve their return on investment.

Q: What should producers do for better ND control?

LV: Good hygiene and biosecurity will always be important, but we need to do some things differently. Einstein is widely quoted as saying the definition of insanity is “doing the same thing over and over again and expecting different results.”

This saying can be applied to the poultry industry. We need updated, simpler, convenient immunization programs designed to address the ND challenge in a given area. The program should enable birds to develop immunity without causing reactions, while minimizing field-handling of birds.

The best vaccine program must complement industry trends, such as the move toward higher-yield broilers produced in a shorter period.

Q: How does the recombinant vaccine INNOVAX-ND figure into today’s management programs?

LV: This innovative vaccine has several advantages compared to conventional ND vaccines. Its foundation is the herpesvirus of turkey (HVT), which is known to be safe for chickens and protects against Marek’s disease. It carries the fusion or “F” protein of the ND virus, which initiates immunity against ND. So, you get protection against two important diseases with one vaccine.

The vaccine can be administered in ovo to 18-day-old embryos or soon after hatching by subcutaneous injection at the hatchery, where application is more likely to be properly done than in the field. INNOVAX-ND is effective in the presence of maternal antibodies.

One application provides lifelong protection and eliminates or minimizes the need for ND field vaccination.

Q: Does the recombinant vaccine protect against virulent ND?

LV: Yes. The F protein protects against all ND strains and genotypes, including velogenic ND. Experience with millions of birds already vaccinated with INNOVAX-ND — including those challenged by more virulent forms of ND — has demonstrated that INNOVAX-ND is effective. In addition, for licensure in different countries, studies were conducted that showed INNOVAX is effective when vaccinated birds are challenged with a variety of ND strains, including the virulent Texas GB strain and strains with an intra-cerebral pathogenicity index between 1.89 and 2.0, such as Hertz 33, Chimalhuacán and Asian virulent CU2 strains.

Q: How long does it take for immunity to develop with INNOVAX-ND?

LV: Immunity gradually increases after vaccination and is complete 21 to 28 days later. A key to success with INNOVAX is the inclusion of a conventional ND vaccine to cover birds while immunity from the recombinant vaccine develops. Usually one live vaccine administered at the hatchery is adequate.

In high-challenge areas facing velogenic viscerotropic ND, a second live ND booster can be administered before 21 days to help ensure total protection. On the other hand, in regions with a low ND challenge, INNOVAX-ND alone should be all that’s needed.

Q: Is the recombinant cost effective?

LV: Economic analyses have shown that whether flocks are challenged by mild or virulent forms of ND, INNOVAX-ND will provide a high return on investment because it controls ND mortality and morbidity, and it eliminates the problem of post-vaccinal reactions and associated production losses that can occur with conventional vaccine protocols. It increases productivity and, consequently, profitability.

Convenience Program helps producers protect flocks against respiratory diseases and maintain marketing goals

Merck Animal Health has developed a hatchery-based Convenience Program designed to help poultry producers protect chickens against respiratory diseases while achieving optimal bird performance and marketing goals.

In today’s competitive, global marketplace, poultry producers are under increased pressure to reduce the growing period, says Laura Villarreal, DVM, global marketing director, Merck Animal Health. “there will be less time for field vaccination and no time for vaccine application mistakes, vaccine reactions or performance setbacks. Even one day of lost performance is expensive,” she says.

The Convenience Program features hatchery application of recombinant INNOVAX vaccines, which provide lifelong protection with one dose, and the PROTECTOTYPE concept, which provides broad protection against infectious bronchitis (IB).

Depending on the predominant disease in their area, producers can use either INNOVAX-ND to protect against Newcastle disease (ND) or INNOVAX-ILT to protect against infectious laryngotracheitis. Like INNOVAX-ND, INNOVAX-ILT does not cause performance-damaging respiratory reactions, Villarreal says. She notes that both vaccines, which are based on the herpesvirus of turkey, cannot be used together, but says that INNOVAX vaccines do not interfere with administration of live respiratory vaccines.

In areas with a high ND challenge, hatchery administration of NOBILIS ND C2 and/or NOBILIS Clone 30 will protect chicks while immunity from INNOVAX-ND develops, Villarreal says.

The PROTECTOTYPE concept lets producers provide broad-spectrum protection against iB with hatchery vaccination. NOBILIS IB MA5, a vaccine based on the Massachusetts serotype, NOBILIS 4/91 and SHOR-BRON DE072 vaccines can be administered from day 1 in the hatchery.

For more information, contact your Merck/MSD Animal Health representative.

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