Replacing a conventional Newcastle disease or infectious laryngotracheitis vaccine with a recombinant can simplify the vaccination schedule, improve control of these as well as other important poultry diseases and provide a good return on investment, says biologist Francisco Ríos.
Areas in Latin America with no or low (lentogenic) Newcastle disease (ND) challenge include Brazil, Chile and Argentina. At the other end of the spectrum are high-challenge areas, such as Mexico and Venezuela, where velogenic ND can cause mortality as high as 90%.
“And we are learning now that Peru may be included in this list,” adds Ríos, a technical service manager for MSD Animal Health*, Mexico
Despite vaccination, ND alone still accounts for about 2% to 3% of the total yearly mortality in broilers in Mexico. “If we are talking about a yearly production of about 1.5 billion broilers, that’s millions and millions of dollars lost,” Ríos says.
For layers, the average loss due to ND is about 15% but can be as high as 25%. “The curious thing is that the hens do not die from ND; they just don’t lay,” Ríos adds.
Conventional vaccines ‘problematic’
Conventional vaccination programs are costly and problematic, he continues. As an example, broilers in Mexico may have to be vaccinated against ND at least once with an individually applied, killed vaccine that stresses birds due to handling, potentially causes serious local reactions and runs up labor costs. Most companies also apply at least two live ND vaccines; these vaccines can cause severe respiratory distress, increase medication expenses, also run up labor costs and interfere with infectious bronchitis (IB) vaccines.
Control of infectious laryngotracheitis (ILT), which is endemic in major poultry-producing countries including Brazil, Argentina, Colombia, Mexico and Peru, is equally challenging, Ríos says.
The consequences of conventional ILT vaccination include potential respiratory reactions and, with some of the vaccines, house-to-house spread of the ILT virus; the result is reduced bird performance, he says.
Conventional vaccines for ILT and ND have to be applied separately, sometimes spaced several weeks apart depending on the situation. “Given the short life span of the broiler, this complicates vaccination-schedule planning,” Ríos says.
Benefits of recombinants
Replacing conventional ND vaccines with the recombinant INNOVAX-ND-SB (sold in some markets as FUSION-ND-SB) decreases the viral load in the environment, improves vaccine uniformity, eliminates the problem of interference between live ND and other respiratory vaccines, and causes no vaccine reactions. Flocks will have solid protection against all known genotypes of ND, he says.
The “SB” in INNOVAX-ND-SB represents serotype 2 of the SB1 Marek’s strain, which protects against the very virulent form of Marek’s, Ríos says, adding that INNOVAX-ND-SB can be administered either in ovo or subcutaneously.
“Add up the cost of conventional ND vaccines, associated labor costs and export restrictions due to poor disease control. When you consider that switching to one dose of the recombinant vaccine removes all these negatives from the equation, you realize that it represents a good return on investment for both broilers and layers,” Ríos maintains.
In addition, by gaining good control of ND, producers can focus on other disease problems, such as IB, and additional ways that poultry production and profits can be improved, he adds.
Ríos reminds producers that two herpesvirus-of-turkey (HVT) vaccines cannot be used together. This caution applies to regular or recombinant HVT vaccines. He advises choosing the recombinant HVT respiratory vaccine that controls the biggest problem and using conventional live vaccines for the other diseases.
For instance, infectious bursal disease (IBD) virus — commonly called Gumboro — can still be controlled well with conventional vaccines, especially in areas where the presence of IBD antigenic variants are documented, Ríos says.
With the recombinant vaccines, he says, there are no respiratory reactions, no interference with other conventional respiratory vaccines, decreased mortality from ILT, decreased productive failure and improved possibilities for export.
“Our recombinant vaccines are now the best tool that we have available for control of ND and ILT,” he says.
*Known as Merck Animal Health in the US and Canada.