KUALA LUMPUR, Sept 19 — Despite over 70 years of vaccine development, Newcastle disease, a highly contagious poultry virus, continues to wreak havoc on Malaysian farms. This alarming reality raises significant questions about the efficacy of existing vaccination strategies, especially in environments with poor biosecurity and sanitation measures.

According to Prof Dr. Abdul Rahman Omar, a professor of immunology and infectious diseases at Universiti Putra Malaysia (UPM), vaccines may alleviate symptoms but fail to halt infections completely. He likened the situation to COVID-19, stating, "Even if vaccinated, people can still catch the virus due to insufficient immunity. The same applies to Newcastle disease."

Understanding Newcastle Disease: The Virus and Its Variants

Newcastle disease is caused by the Newcastle disease virus (NDV), characterized by several crucial proteins, including the F, H, and G genes. While there is only one serotype of NDV, making vaccinations theoretically straightforward, the virus is genetically diverse. At least 21 distinct genotypes have been identified, with genotype VII emerging as the most prevalent globally.

Dr. Abdul Rahman highlighted that locally, genotype VII.2 shares genetic differences from older vaccine strains like LaSota and V1, which could diminish vaccine effectiveness. He noted that over 20% of the genotype VII virus differs from the LaSota strain, particularly in its F gene.

Beyond Commercial Farms: The Hidden Reservoirs of Infection

Moreover, Newcastle disease isn't confined to commercial poultry; it spreads among backyard flocks, ducks, geese, and even wild birds. Many of these species can carry the virus asymptomatically, acting as silent carriers that complicate containment efforts. Dr. Abdul Rahman elaborated that geese and ducks, which might not show signs of illness, can effectively transport the virus over vast distances.

The Crucial Role of Biosecurity and Farm Management

Recurring outbreaks are not solely attributable to the virus; they are significantly influenced by inadequate farm management and immunity. Dr. Abdul Rahman stated, "Outbreaks frequently occur when the virus re-infiltrates farms, particularly when bird immunity remains low despite vaccination and sanitation practices are lax." This emphasizes that without solid biosecurity measures, the threat of Newcastle disease remains ever-present.

Rethinking Vaccination Strategies

Farmers often repeat vaccination protocols without revising their strategies, and this oversight may exacerbate outbreaks. "If vaccination doesn’t yield results, it’s time to reassess your program," he advised. Concurrent infections and factors like immunosuppression can hinder vaccine effectiveness, underscoring the need for a tailored vaccination approach.

The Promise of Genotype-Matched Vaccines

Dr. Abdul Rahman pointed to the future of vaccines, suggesting that genotype-matched versions could be the game-changer needed for effective prevention. Trials in Malaysia have shown stronger antibody responses and lower transmission rates with these tailored vaccines. South Korea has seen a remarkable decline in Newcastle disease incidence post-implementation.

The Takeaway: Biosecurity is Key!

Despite the advancements in vaccine technology, Dr. Abdul Rahman cautioned that vaccines cannot substitute for robust farm management practices. Biosecurity must be a top priority to eliminate the virus from farms. He concluded that while Newcastle disease remains endemic in Malaysia, enhancing biosecurity, adjusting vaccination strategies, and maintaining diligent farm management can significantly mitigate its impact.