1. Poultry Industry in Saudi Arabia

The strategic national food security goals of Saudi Vision 2030 are driving the extraordinary structural expansion of the poultry industry in the Kingdom of Saudi Arabia (KSA). Under the direction of the Ministry of Environment, Water, and Agriculture (MEWA), the sector is quickly moving away from reliance on imports and toward total local self-sufficiency.

Poultry Population and Sector Dynamics

• Massive Capital Investment: The industry has experienced rapid capacity expansions as to a multibillion-dollar agricultural funding boost from the Saudi Agricultural Development Fund (ADF). This includes multi-million bird capacity expansions by industry heavyweights like Al-Watania Poultry, Tanmiah Food Company, and Balady Poultry, as well as huge infrastructure projects like the livestock city project in the Eastern Province (the largest integrated poultry complex in the Middle East).
• Self-Sufficiency Milestones: By 2030, the Kingdom hopes to achieve an ambitious 80% self-sufficiency rate for poultry meat, up from around 70% in prior years. Highly automated, biosecure, and climate-controlled closed housing systems that can withstand the intense heat of the Arabian desert are crucial to the change.
• Consumption of Poultry Meat: For the Saudi population and its massive seasonal influx of pilgrims (Umrah and Hajj), poultry is the main and most economical source of animal protein. The General Authority for Statistics (GASTAT) reports that the yearly per capita availability and consumption of poultry meat range from 40 kg to 46.90 kg, which is a very high rate. Fresh and chilled poultry products, which account for more than 55% of customer demand, are highly favored by the market.
• Table Egg Consumption: With domestic output exceeding 8 billion eggs per year, MEWA formally declared in March 2025 that Saudi Arabia has reached 100% full self-sufficiency in table eggs. At roughly 150 to 190 eggs per person per year, per capita egg consumption is strong and in line with high GCC benchmarks. This is largely due to the enormous institutional demand in Makkah and Madinah’s hospitality industries.

2. Newcastle Disease Brief and First Detection in the Country

Pathogen Essentials

Newcastle Disease (ND) is a highly contagious and economically devastating viral infection affecting domestic poultry and a vast range of wild and peridomestic avian species. The disease is caused by virulent strains of Avian Orthoavulavirus-1 (AOAV-1)—historically classified as Avian Paramyxovirus-1 (APMV-1)—an enveloped, single-stranded, RNA virus belonging to the family Paramyxoviridae.

Pathotypes and Clinical Presentation

Based on the severity of clinical manifestations in susceptible chicken models, the virus pathotypes are categorized into three primary classes:

• Velogenic Strains: Highly virulent lineages causing acute, systemic disease with mortality rates approaching 100%. They present as either viscerotropic (severe hemorrhagic lesions in the gastrointestinal tract, proventriculus, and cecal tonsils accompanied by greenish diarrhea) or neurotropic (acute respiratory distress followed by severe neurological signs, including torticollis, paralysis, and tremors).
• Mesogenic Strains: Intermediate virulence, typically associated with mild respiratory signs and sharp drops in egg production, with low mortality confined mostly to young birds.
• Lentogenic Strains: Low virulence or completely avirulent field strains. These cause subclinical infections and serve globally as master seeds for live vaccines.

Historical First Detection

In Saudi Arabia, structural veterinary diagnostics and formal tracking of avian pathogens began intensifying in the late 20th century. The first official documentation of velogenic Newcastle Disease Virus strains circulating within the Kingdom occurred in the 1980s, published by researcher A. El-Zein. Since this initial characterization, the virus has maintained a hyper-endemic status across the Arabian Peninsula, fluctuating between subclinical persistence in well-vaccinated commercial flocks and severe, localized outbreaks in backyard systems.

3. Most Prevalent Genotypes and Recent Outbreaks

The molecular epidemiology of Class II Newcastle Disease viruses in Saudi Arabia is highly dynamic, characterized by the co-circulation of multiple genotypes heavily influenced by regional trade, live-bird markets, and migratory bird flyways.

Most Prevalent Genotypes

Phylogenetic sequencing focusing on the hypervariable region of the viral fusion ($F$) gene has identified two distinct genotypes actively affecting avian populations:

• Genotype VII (Specifically Sub-genotypes VII.1.1 and VIId): This represents the predominant velogenic lineage driving major commercial breakthroughs and economic losses within the Kingdom. These isolates carry the multi-basic amino acid cleavage site motif ($^{112}\text{RRQKRF}^{117}$), conferring high systemic replication efficiency. They share high nucleotide identity with highly pathogenic strains circulating across the Middle East and East Asia.
• Genotype VI (Specifically Sub-genotype VI.2.1): Frequently isolated from Columbiform species (pigeons and doves). Recent molecular surveillance from 2021 to 2023 in the Eastern Region (Al-Ahsa) confirmed a high prevalence of velogenic Genotype VI.2.1 alongside Genotype VII.1.1 in backyard pigeon holdings.
• Genotype II: Widely detected across commercial operations, though predominantly classified as low-virulence, vaccine-derived lentogenic strains (resembling LaSota or B1 master seeds).

Recent Outbreak Dynamics and Vulnerabilities

Epidemiological mapping shows that outbreaks are heavily clustered in regions with dense poultry operations, particularly the Eastern and Central Regions.

Recent field data highlights that while modern, environmentally controlled commercial houses restrict clinical outbreaks to less than 10% of cases due to strict structural biosecurity, traditional backyard holdings and open-air live bird markets account for nearly 70% of clinical cases. These backyard environments act as permanent viral reservoirs. Furthermore, infected peridomestic pigeons showing dominant nervous and respiratory manifestations serve as critical vectors for cross-species transmission, spilling the virulent virus into adjacent commercial zones.

4. Control, Recommendations, and Vaccination

Controlling Newcastle Disease in Saudi Arabia requires addressing the continuous threat of antigenic mismatch between historic vaccine strains and evolving field viruses.

Integrated Vaccination Protocols

• Overcoming Antigenic Divergence: The majority of standard live vaccines used in the Kingdom (e.g., LaSota, Clone 30) belong to Genotype II. While these effectively prevent mass mortality, they do not completely halt the replication and environmental shedding of circulating Genotype VII field strains.
• Homologous Inactivated Emulsions: Commercial operations are increasingly utilizing a strategic combination: administering live Genotype II strains to establish rapid local mucosal immunity, paired with oil-adjuvanted, inactivated vaccines containing homologous Genotype VII antigens. This dual approach maximizes humoral antibody titers and curtails environmental viral shedding.
• Hatchery Recombinant Vectors: Large-scale commercial hatcheries widely utilize recombinant vector vaccines—specifically Turkey Herpesvirus expressing the NDV fusion gene (rHVT-NDV)—at day-old stages to guarantee long-term cellular immunity that bypasses maternal antibody interference.

Biosecurity and Policy Recommendations

• Strict Vector and Wild Bird Exclusion: Due to the verified role of pigeons and migratory waterfowl in carrying Genotypes VI and VII, farms must enforce complete physical exclusion by installing high-density wire mesh netting over all ventilation louvers, air pads, and feed silos.
• Live Bird Market Regulation: MEWA and local municipalities should mandate routine real-time RT-PCR molecular screening at live bird trading hubs to intercept subclinical viral shedding before birds are transported across governorates.
• Upgrading Smallholder Infrastructure: Transitioning remaining open-sided, traditional semi-intensive farms into closed, negative-pressure environmental control systems drastically reduces exposure to airborne viral particles and minimizes climate-induced stress during seasonal transitions.