Vector vaccine helps address Newcastle disease challenges

Caused by avian paramyxovirus type 1 (APMV-1), it affects the respiratory, digestive, and nervous systems. While NDV has only one recognised serotype, the virus is genetically diverse, comprising multiple genotypes. Genotype VII, and particularly sub-genotype VIIh, have become predominant in many parts of Asia, the Middle East, and Africa, prompting urgent demand for vaccines that offer robust cross-genotypic protection.

“In theory, any well-constructed ND vaccine should provide cross-protection due to the single serotype nature of NDV,” according to CK Mah, DVM, global commercial development livestock lead for Asia at Zoetis. “However, the ongoing evolution of new genotypes has made it evident that more specific immunity may be required, especially in areas with virulent strains like genotype VII and its numerous sub-genotypes. This is where vector vaccines offer a distinct advantage,” Mah said, explaining the Poulvac Procerta HVT-ND vaccine* was developed to deliver effective cross-protection against emergent NDV genotypes.

“The herpesvirus of turkey (HVT) vector in Poulvac Procerta HVT-ND contains the NDV fusion (F) gene, a critical immunogenic component responsible for viral entry into host cells. The F protein is a major target of neutralising antibodies, making it highly effective in eliciting immunity across NDV genotypes.” he said. “This specific insertion allows the vaccine to stimulate robust protection without the adverse reactions typically associated with live ND vaccines.”

Solid protection and reduced DNV shedding

Multiple studies have demonstrated that this HVT-ND vaccine, when administered in ovo or subcutaneously at hatch, provides protection to poultry against ND and Marek’s disease from as early as 19 days of age. In research using specific-pathogen-free (SPF) birds challenged with a velogenic NDV strain, protection rates of 93% (subcutaneous) and 95% (in ovo) were observed at 19 days post-hatch.

In Malaysia, a study using genotype VIIh demonstrated that 100% of SPF birds vaccinated in ovo at 18 days of incubation were protected against NDV challenges at both 21 and 28 days of age. Birds vaccinated subcutaneously at day of age achieved 95% protection when challenged at 21 days of age and 100% at 28 days. Notably, all unvaccinated control birds succumbed to infection, while vaccinated birds showed no clinical signs of disease.

Beyond clinical protection, the capacity of Poulvac Procerta HVT-ND to reduce virus shedding is crucial. Reduced shedding curtails the spread of NDV in poultry populations and diminishes the chance for virus evolution under immune pressure. In the Malaysian study, birds vaccinated with the HVT-ND vaccine shed significantly less virus than unvaccinated controls or those on mixed live/killed ND vaccine regimens.

“For quite a long time, the producers’ main objective was to prevent the high mortality caused by this disease. As scientific knowledge progressed, ND vaccines are increasingly evaluated by their capacity to significantly reduce the shedding of challenge virus, as this has an important impact on the long-term control of ND,” Mah explained.

Single dose sufficiency and field flexibility

The Malaysian study also evaluated the recombinant HVT-ND vaccine used in combination with either a live vaccine alone, or a combination of a live and an inactivated ND vaccine, simulating real-world mixed vaccination programs – a common approach likely to be used by producers facing high-risk and complex virulent NDV field challenges. Despite this, the single-dose use of Poulvac Procerta HVT-ND alone provided robust protection and reduced virus shedding. This highlights its flexibility and practical value in high-risk field settings, where genotype VII and other virulent strains circulate.

“The ability to simplify vaccination protocols while maintaining high efficacy makes Poulvac Procerta HVT-ND a vital tool for producers in endemic regions,” Mah noted.