Newcastle Disease (ND), also known as avian paramyxovirus type 1 (APMV-1), is a highly contagious viral infection that primarily affects birds, especially poultry. It is caused by a member of the Paramyxoviridae family and has several strains with varying levels of severity. The disease is named after Newcastle upon Tyne in England, where it was first identified in 1926 during a severe outbreak among domestic poultry.
Newcastle Disease virus can infect a wide range of bird species, including chickens, turkeys, pigeons, ducks, and wild birds. The virus is transmitted through direct contact with infected birds, their bodily fluids, and contaminated surfaces. It can also spread indirectly through contaminated feed, water and equipment, and even by airborne transmission over short distances.
The severity of Newcastle Disease can vary widely depending on the strain of the virus.
There are three main classes of strains:
1. Lentogenic Strains:
These are the mildest strains and usually cause only mild respiratory and digestive symptoms in birds. They are commonly used in vaccines to provide immunity against more virulent strains.
2. Mesogenic Strains:
These strains cause moderate symptoms, affecting both the respiratory and nervous systems. Birds infected with mesogenic strains may exhibit coughing, sneezing, nasal discharge, and nervous signs such as trembling and paralysis.
3. Velogenic Strains:
These are the most virulent and dangerous strains of Newcastle Disease. They can lead to severe respiratory distress, nervous system disorders, and high mortality rates in infected flocks. Velogenic strains are responsible for the most devastating outbreaks of the disease.
Clinical Signs and Symptoms of Newcastle Disease
New Castle disease mainly affects the respiratory, digestive, and nervous systems of infected birds;
Respiratory Signs of ND:
- Nasal discharge (running nose)
Digestive Signs of ND:
- Greenish dropping
- Reduced feed intake
- Drop in egg production
- Thin-shelled or misshapen eggs
Nervous Signs of ND:
- Paralyzed legs and wings
- Twisting of the neck (torticollis)
- Incoordination and stumbling
Postmortem Lesions of ND
Chicken Newcastle Disease (ND) lesions can differ according to the virus strain, the organs affected, and the disease’s severity.
Respiratory Lesions of ND:
- Tracheitis: Inflammation of the trachea (accumulation of mucus in trachea).
- Sinusitis: Inflammation of the sinuses.
- Conjunctivitis: Inflammation of the conjunctiva (membrane covering the eyes).
Digestive Lesions of ND:
- Enteritis: Inflammation of the intestines can cause changes in the intestinal lining and watery or greenish droppings.
- Typical pinpoint hemorrhages on Proventriculus.
Nervous Lesions of ND:
- Inflammation of the brain leads to paralysis, twisting of the neck (torticollis), and incoordination.
Prevention and Control of Newcastle Disease ND
A comprehensive approach consisting of biosecurity precautions, vaccinations, surveillance, and quick response to outbreaks is required to prevent and control Newcastle Disease (ND). Here are the main techniques for controlling and dealing with ND in poultry:
Biosecurity measures of Newcastle Disease:
- Isolation and Quarantine
- Restricted Access
- Cleanliness and Disinfection
- Footbaths and Hand Sanitization
Newcastle Disease Vaccine:
A key strategy for preventing Newcastle Disease is vaccination. It aids in the development of avian immunity and lessens the severity of the illness should an outbreak take place.
Surveillance and Monitoring of the effected flock:
- Perform regular monitoring of the flock’s health and behavior to detect any unusual signs or symptoms.
- Conduct diagnostic testing to confirm the presence of Newcastle Disease in suspected cases.
What is the Zoonotic Risk of Newcastle Disease?
All Newcastle disease virus strains can cause temporary conjunctivitis in humans; however, these cases have mostly affected lab workers and vaccination teams who have been exposed to high viral loads.
Conjunctivitis from NDV infection occurred among crews dissecting poultry in processing factories prior to the widespread adoption of poultry vaccinations. No cases of the illness have been reported in people who consume or rear chicken.