Newcastle Disease in Poultry: Symptoms, Vaccination, and Biosecurity

 Newcastle Disease (ND) is a highly contagious, often severe, viral disease affecting birds worldwide, especially poultry. It is caused by virulent strains of Avian Orthoavulavirus 1 (formerly Avian Paramyxovirus type 1). It is a major threat to the poultry industry due to its potential for high mortality and trade restrictions.

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Symptoms

Symptoms vary greatly depending on the virus strain (pathotype), bird species, age, immune status, and co-infections. The main pathotypes are:

1. Velogenic (Viscerotropic) - Very virulent, causes acute, lethal systemic disease.

   • Sudden, high mortality (can reach 100%).

   • Severe depression, loss of appetite.

   • Greenish, watery diarrhea.

   • Facial edema (swelling) around eyes and neck.

   • Respiratory distress: gasping, coughing, gurgling, nasal discharge.

   • Neurological signs (also common in neurotropic strains): tremors, paralyzed wings/legs, twisted necks (torticollis), circling, paralysis.

   • Hemorrhages at the tips of the glandular stomach.

2. Velogenic (Neurotropic) - Very virulent, primarily causes neurological and respiratory signs.

   • High mortality in young birds.

   • Pronounced neurological signs (head twisting, paralysis).

   • Respiratory distress.

3. Mesogenic - Moderately virulent.

   • Respiratory illness, occasional nervous signs.

   • Reduced egg production, thin-shelled eggs.

   • Low mortality in adults, higher in young.

4. Lentogenic - Mildly virulent.

   • Mild or subclinical respiratory infection.

   • Asymptomatic enteric infection (common in waterfowl).

Note: A drastic drop in egg production with misshapen, thin-shelled, or albumen (white)-less eggs is a classic sign in laying hens, even with milder strains.

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Vaccination

Vaccination is a critical control tool but does not prevent infection or shedding entirely. It reduces disease severity, mortality, and viral spread.

• Vaccine Types:

  • Live Vaccines (Lentogenic strains): e.g., La Sota, B1, B1 (Hitchner), VG/GA, Clone 30.

    • Pros: Strong cellular & local mucosal immunity (IgA), administered via drinking water, spray, or eye/nose drop.

    • Cons: Can cause mild vaccine reactions, may be unstable in water.

  • Inactivated (Killed) Vaccines:

    • Pros: No vaccine reaction, stable, administered by injection (individual).

    • Cons: Primarily systemic immunity, requires individual handling, needs a live vaccine primer first.

• Common Vaccination Programs:

  1. Priming: Day 1-14 with a live vaccine (eye drop or spray).

  2. Boosting: At 3-4 weeks with a live vaccine (water or spray).

  3. Layers/Breeders: Revaccinate with live vaccine before lay (12-16 weeks) and follow with an inactivated vaccine to ensure high, persistent antibody levels for chick protection (maternal antibodies).

• Key Point: Vaccination must be part of a comprehensive biosecurity program.

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Biosecurity

This is the FIRST and MOST IMPORTANT line of defense to prevent the virus from entering or spreading on a farm.

1. Restrict Access:

   • Control human, vehicle, and equipment movement.

   • Use footbaths, wheel dips, and change clothing/footwear before entering poultry houses.

   • Implement a "shower-in/shower-out" policy for high-risk sites.

2. Sanitation & Disinfection:

   • Thoroughly clean and disinfect houses between flocks (effective against NDV).

   • Disinfect equipment, crates, and tools regularly.

3. Pest & Wild Bird Control:

   • Wild birds (especially cormorants, pigeons) are natural reservoirs. Seal houses from wild birds and rodents.

   • Control insects.

4. Water & Feed Security:

   • Ensure drinking water is clean and sanitized. Water sources should be protected from wild bird droppings.

   • Store feed in sealed containers to prevent contamination.

5. All-In/All-Out Management:

   • Depopulate entire site, clean/disinfect, and restock with birds of the same age.

6. Sick Bird Protocol:

   • Isolate sick birds immediately. Do not move birds off the farm.

   • Dead birds should be composted, incinerated, or buried properly.

7. Diagnosis & Reporting:

   • Report any suspicion of Velogenic ND to animal health authorities immediately. It is a notifiable disease in most countries.

   • Confirm diagnosis through laboratory testing (virus isolation, PCR).

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Conclusion

Newcastle Disease remains a constant threat to poultry health and food security. Effective control relies on a three-pillar approach:

1. Vigilance: Recognizing clinical signs early.

2. Prevention: Implementing strict, continuous biosecurity to block virus introduction.

3. Immunization: Following a well-designed vaccination program tailored to the local challenge.

Always consult with a poultry veterinarian or animal health official to develop a control plan specific to your region and operation.