Newcastle disease (ND) is a highly contagious viral infection that poses significant challenges in poultry farming globally. Caused by avian paramyxovirus type 1 (APMV-1), this disease impacts the respiratory, digestive, and nervous systems of birds. Despite its single recognized serotype, NDV exhibits genetic diversity, particularly among its various genotypes, with genotype VII and its sub-genotype VIIh gaining prominence in several regions, including Asia, the Middle East, and Africa. This shift has escalated the need for robust vaccines capable of offering cross-genotypic protection.
“In theory, any well-constructed ND vaccine should provide cross-protection due to the virus’s single serotype nature,” states CK Mah, DVM, global commercial development livestock lead for Asia at Zoetis. “However, the emergence of new genotypes has highlighted the necessity for more specific immunity, especially in areas suffering from virulent strains like genotype VII and its various sub-genotypes. This is where vector vaccines, such as the Poulvac Procerta HVT-ND vaccine, offer a notable advantage.”
The Poulvac Procerta HVT-ND utilizes a herpesvirus of turkey (HVT) vector, which incorporates the NDV fusion (F) gene. This gene is critical in facilitating viral entry into host cells and is a major target for neutralizing antibodies. This unique design enables the vaccine to elicit a strong immune response across different NDV genotypes while minimizing adverse reactions that are often seen with live ND vaccines.
Solid Protection and Reduced NDV Shedding
Research has consistently demonstrated that the HVT-ND vaccine, administered either in ovo or subcutaneously at hatch, effectively protects poultry against both ND and Marek’s disease as early as 19 days post-hatch. In studies involving specific-pathogen-free (SPF) birds challenged with a virulent NDV strain, the vaccine exhibited protection rates of 93% (for subcutaneous) and 95% (for in ovo).
A notable study in Malaysia involving genotype VIIh reported that all SPF birds vaccinated in ovo at 18 days of incubation were safeguarded against NDV challenges at both 21 and 28 days of age. Birds vaccinated subcutaneously on the day they hatched achieved 95% protection when challenged at 21 days and a remarkable 100% at 28 days. In stark contrast, unvaccinated control birds faced a high mortality rate, while vaccinated birds showed no clinical signs of the disease.
Importantly, the Poulvac Procerta HVT-ND vaccine’s ability to minimize virus shedding is vital, as reduced shedding lowers the risk of NDV transmission within poultry populations. According to the Malaysian study, vaccinated birds shed significantly less virus than their unvaccinated counterparts or those receiving mixed live and killed ND vaccine regimens.
“Historically, producers focused primarily on minimizing mortality caused by ND. However, with advancements in science, ND vaccines are increasingly scrutinized for their effectiveness at reducing challenge virus shedding, which is pivotal for the long-term control of ND,” Mah elaborated.
Single Dose Sufficiency and Field Flexibility
The Malaysian study also examined the HVT-ND vaccine’s compatibility with either a live ND vaccine or a mixed regimen of live and inactivated vaccines, reflecting typical vaccination practices in high-risk areas. Remarkably, even when used alone, the single-dose Poulvac Procerta HVT-ND vaccine provided solid protection and reduced virus shedding, showcasing its flexibility and practical use in challenging field situations where virulent strains circulate.
“The potential to streamline vaccination protocols while retaining high efficacy makes Poulvac Procerta HVT-ND an essential tool for producers operating in endemic regions,” noted Mah.
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References are available upon request.
