Velogenic Viscerotropic Newcastle Disease (VVND) : A Highly Lethal Threat to India’s Poultry Sector
🔬 What is VVND?
Velogenic Viscerotropic Newcastle Disease (VVND) is the most severe form of Newcastle Disease (ND), caused by a highly virulent strain of the Avian Paramyxovirus Type 1 (APMV-1). This virus targets the digestive tract (viscera) and is highly contagious and often fatal in poultry, especially in chickens.
Classification of Newcastle Disease Virus (NDV) Strains
A. Lentogenic (Mild) – Causes mild respiratory infections. Used in vaccines (e.g., LaSota, B1, F strain).
B. Mesogenic (Moderate) – Causes moderate disease with lower mortality.
C. Velogenic (Severe & Deadly) – Further divided into:
Velogenic Neurotropic NDV (VNND) – Primarily affects the nervous system.
Velogenic Viscerotropic NDV (VVND) – Primarily affects the digestive system and internal organs.
⚠️ Key Characteristics of VVND:
- Causative Agent: Avian paramyxovirus serotype 1 (APMV-1)
- Strain Type: Velogenic (highly virulent), viscerotropic (affecting intestines)
- Species Affected: Primarily chickens; also ducks, turkeys, pigeons, wild birds
- Transmission: Aerosols, direct contact, contaminated feed/water, fomites (equipment, clothing)
- Incubation Period: 2–15 days
Symptoms & Clinical Signs
VVND affects multiple organs, leading to severe systemic infection.
a. Digestive Symptoms (Viscerotropic Form)
Severe greenish or yellowish diarrhea.
Hemorrhages in the intestines (bloody droppings).
Swollen and hemorrhagic proventriculus (glandular stomach).
b. Respiratory Symptoms
Severe respiratory distress (gasping, coughing, sneezing).
Swelling of the head, eyelids, and wattles.
Nasal discharge and conjunctivitis (swollen eyes).
c. Nervous System Symptoms
Twisted neck (torticollis) and paralysis.
Complete paralysis in advanced cases.
d. Mortality Rate
Near 100% mortality in unvaccinated flocks.
Death occurs within 48–72 hours after infection.
🧪 Clinical Signs of VVND:
- Sudden high mortality (up to 90-100% in unvaccinated flocks)
- Severe diarrhea (greenish, bloody)
- Swollen proventriculus and hemorrhages in intestines
- Respiratory distress (rales, sneezing, nasal discharge)
- Neurological signs (torticollis, paralysis)
- Drop in egg production
- Hemorrhages in trachea, cecal tonsils, and other organs (seen post-mortem)
🧫 Diagnosis:
- Clinical signs and gross lesions
- Laboratory tests:
- Hemagglutination inhibition (HI) test
- Virus isolation
- RT-PCR
- Pathogenicity index (ICPI, MDT, IVPI)
Prevalence in India:
VVND is endemic in India and has caused several outbreaks, particularly in:
- Backyard and desi poultry
- Poorly vaccinated commercial farms
- Hotspots: Bihar, Jharkhand, Odisha, Uttar Pradesh, Andhra Pradesh, Assam, and North East states
The climate, biosecurity gaps, and low vaccination coverage contribute to frequent outbreaks, especially in rural and tribal areas.
📉 Economic Impact of VVND in India:
- 💸 High Mortality Losses
- Mortality rates of 70–100% in unvaccinated flocks
- Direct loss of livestock asset for smallholders and rural poor
- 🐣 Reduced Productivity
- Drop in egg production by 30–80%
- Poor growth in broilers
- 🏭 Market Disruption
- Loss of consumer confidence during outbreaks
- Trade bans on live birds and poultry products
- Disruption in supply chains for hatcheries, feed, and pharmaceuticals
- 🧬 Cost of Control
- Vaccination and revaccination campaigns
- Surveillance and diagnostic testing
- Culling and compensation in case of outbreaks
- 👩🌾 Livelihood Threat
- Backyard poultry is a critical livelihood for rural women, SC/ST communities, and landless farmers
- VVND outbreaks push families into economic vulnerability
💡 Estimated Economic Loss:
India loses hundreds of crores annually due to ND outbreaks, including VVND. The estimated loss per outbreak in a medium-sized flock can exceed ₹2–5 lakhs, depending on scale and region.
🛡️ Prevention and Control Measures:
✅ Vaccination Protocol
- Live Lentogenic (F1 or LaSota) vaccine at day 5–7 and booster every 4–6 weeks
- Inactivated (killed) vaccine for breeders and layers
- Thermostable vaccines like I-2 and Mukteswar for remote/rural areas
🔒 Biosecurity
- Isolation of new birds
- Disinfection of premises
- Control of visitors, rodents, and wild birds
📢 Community Awareness
- Training rural poultry keepers on symptoms and vaccination
- Promoting ND control under livestock health missions
🧠 VVND & One Health Approach
Since ND virus can affect wild birds and is part of the avian-migratory disease network, controlling VVND aligns with the One Health concept, linking animal health, environment, and public health surveillance.
✅ Government & Institutional Efforts
- ND control under National Animal Disease Control Programme (NADCP)
- ND vaccination through Livestock Health and Disease Control (LHDC)
- Research on indigenous ND vaccine strains by ICAR-NIHSAD, IVRI, TANUVAS, etc.
- Distribution of thermostable ND-I2 vaccine by State Animal Husbandry departments
VVND remains one of the biggest threats to India’s poultry sector, especially to the rural poultry economy. Through robust vaccination, biosecurity, and awareness among farmers, the disease can be controlled effectively. Strengthening veterinary services, cold chain logistics, and community-based poultry health workers is key to minimizing its impact in the long term.
