Newcastle disease (ND), also known as chicken pox, is a dangerous acute infectious disease in chickens. The disease has symptoms and lesions similar to avian influenza, characterized by inflammation, hemorrhage and ulceration of the gastrointestinal mucosa.
This is one of the diseases that causes the most damage to the poultry industry, not only in developing countries but also in developed countries. Eradicating the disease also requires a large cost for monitoring and disease prevention programs. Fivevet shares solutions for preventing and treating Newcastle disease in chickens: signs of recognition, diagnosis, and vaccines to help farmers protect their poultry flocks.
1. Newcastle disease in poultry
a. Classification
Newcastle virus belongs to the
Paramyxoviridae family , which has 7 genera (genera) that cause disease in both humans and animals. In which the
Avulavirus genus includes
Newcastle disease virus and avian
paramyxovirus (avian-paramyxoviruses-APMV)
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APMV-1 (Newcastle virus): is the most dangerous strain, causing great damage to the poultry industry, especially in Asia and Africa.
- In addition, other strains such as APMV-2, APMV-3, APMV-6 and APMV-7 can also cause disease in chickens, affecting the health of the flock.
Currently, scientists have identified 20 serotypes from APMV-1 to APMV-20, of which APMV-1 is still the biggest threat to farmers.
b. Resistance
Newcastle virus can survive quite well in the environment, but is also easily destroyed when encountering unfavorable conditions:
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Sensitive to chemicals: easily destroyed by ether, chloroform, formalin and phenol.
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Temperature:
+ At 60°C for 30 minutes or 100°C for only 1 minute, the virus is destroyed.
+ At 4–20°C, the virus can survive for months.
- At negative temperatures, the virus can survive for years.
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pH: environments that are too acidic (pH < 2) or too alkaline (pH > 10) cause the virus to lose its ability to cause disease.
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Ultraviolet rays: can destroy the virus quickly.
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50% glycerin solution: keeps the virus for 7 days at 37°C.
In addition, the heat resistance of
Newcastle virus is genetic. Some special strains can live at 56°C for 6 hours and still be able to cause infection. This characteristic has been applied in research to create heat-resistant vaccines (such as the V4 strain isolated from Australia), making it more convenient for storage and vaccination in rural areas with hot climates.
2.Epidemiology
a.Affected animals
In nature, chickens are the most susceptible to
Newcastle disease. All ages and breeds of chickens can get the disease.
In addition to chickens, some other bird species are also susceptible to the disease such as:
- Pigeons, sparrows, quail and many wild birds.
- Ducks and geese can also be infected, but often do not or rarely show obvious symptoms.
Under experimental conditions,
Newcastle virus can also cause disease in mice and rabbits, but these are not natural hosts.
b.Transmission method
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Route of entry: Newcastle virus mainly enters the chicken's body through the digestive tract (eating and drinking pathogens). In addition, the virus can also be transmitted through the respiratory tract when chickens inhale dust or aerosols containing pathogens.
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Source of infection in the flock: Sick chickens excrete a large amount of virus through feces, polluting the barn environment and becoming a source of rapid spread for the entire flock.
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In experiments: When the virus is injected directly into the muscle, vein or injected into the brain of the chicken, it can cause obvious neurological symptoms.
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Transmission through eggs: Vertical transmission through egg embryos is still controversial; there is no solid evidence to confirm.
Epidemiological characteristics
Newcastle disease can occur year-round, but is most concentrated in winter and spring. When an epidemic breaks out, the disease spreads very quickly.
3. Symptoms of Newcastle disease in poultry
The incubation period usually lasts from 2-15 days, depending on the virulence of the virus strain and the disease form.
a. Hyperacute form
- Occurs due to highly virulent virus strains.
- Often occurs in the early stages of an epidemic.
- The disease progresses very quickly: chickens are severely depressed, and die after a few hours without showing any clinical symptoms.
b. Acute form
Initial symptoms:
- Chickens are depressed, less active, and stop eating.
- Feathers are ruffled, and wings are spread out like "wearing a raincoat".
- Chicks are sluggish, often gather in groups; older chickens often separate from the flock.
- Roosters stop crowing, hens stop laying eggs.
- Diarrhea appears with white droppings like stork droppings.
- Body temperature increases, fever up to 42.5–43°C.
Respiratory symptoms:
- After the disease starts, chickens become lethargic and have severe difficulty breathing.
- The nose runs with a light red or gray-white mucus.
- Chickens sneeze, their beaks continuously, making a characteristic "crackling" sound.
- The mucous membranes of the mouth, pharynx, throat, and nasal cavity contain a lot of dark gray fibrin → the chickens have to stretch their necks and open their mouths to breathe.
- The area around the eyes and head is often swollen.
Digestive symptoms:
- Chickens stop eating but drink a lot of water.
- Food in the crop is not digested, bloated; when turned upside down, mucus flows out with a sour, foul smell.
- A few days later, the chicken has diarrhea: at first the stool is solid, mixed with blood, dark brown → then gradually thinner, grayish white due to containing urate salts.
- Feathers in the tail area are dirty, covered with feces.
General symptoms:
- Comb and wattle are purple due to lack of oxygen, then gradually pale due to blood loss.
- Chickens have muscle tremors, crooked neck, paralyzed legs and wings, many lie in the "opisthotonus" position.
In the acute form, chickens often die within 3 days due to sepsis. In particular, in susceptible flocks, the mortality rate can be up to 100%, causing serious damage to farmers.
c. Chronic form
The chronic form often appears in the late stage of the epidemic, mainly related to central nervous system disorders. Typical manifestations include:
Neurological symptoms:
- Due to damage to the cerebellum, sick chickens often turn their heads back, suddenly stop while walking, walk backwards or walk in circles.
- Many chickens peck at food continuously but do not hit the grain.
- When stimulated, chickens can fall down, convulse, and have epileptic seizures.
Effects on health and reproduction:
- Hens lay significantly fewer eggs.
- Many chickens die from hunger and exhaustion.
- If well cared for, chickens can survive but often have long-term neurological sequelae, affecting productivity.
- Chickens that recover from the disease will have lifelong immunity.
4. Lesions of Newcastle disease in poultry
a. Acute form Lesions
are often unclear, when examining by autopsy, sometimes bleeding can be seen in the pericardium, thorax and respiratory tract mucosa.
b. Acute form
When examining chickens that died from the acute form of
Newcastle disease , many characteristic lesions are often seen:
External manifestations:
- The chicken's body is weak, the comb and wattles are purple.
- The nasal and oral sinuses contain a lot of cloudy mucus.
Respiratory tract:
- The mucous membranes of the pharynx, throat, and trachea are inflamed, hemorrhagic, and covered with a fibrinous pseudomembrane.
- The air sacs are thick and swollen; if there is a bacterial superinfection, there will be catarrh or emphysema.
- In some cases, the connective tissue in the head, neck, and pharynx is emphysematous, with a yellow fluid that easily solidifies like gelatin (can be seen in the pericardial or thoracic sinus).
Digestion:
- The mucosa of the glandular stomach has point hemorrhages at the digestive gland orifices.
- Severe cases: there are hemorrhages before and after the glandular stomach; the muscular stomach has gelatinous osmotic hemorrhage under the stratum corneum.
- Early stage of the small intestine: hemorrhagic inflammation, catarrh.
- Later stage: ulcerated lymphoid follicles, most obvious in Peyer's patches. The ulcer, seen from the outside, is round, oval or bean-shaped, ripe plum-red; when dissected, the ulcer is thick, brown, and easy to peel off.
Internal organs:
- Spleen: not swollen but has necrotic foci.
- Liver: necrotic, hemorrhagic, with pale yellow fatty degeneration.
- Kidney: slightly swollen, with white stripes due to accumulation of urate salts.
- Reproductive organs: testicles and ovaries have streaks or patches of hemorrhage; in many cases, the ovaries adhere tightly to the fallopian tubes, immature eggs rupture, and the yolk spills into the abdominal cavity.
Hemorrhage occurs in the serous membranes such as the pericardium, thoracic cavity, and sternum. Brain inflammation and hemorrhage.
5. Diagnosis of Newcastle disease in poultry
a. Clinical diagnosis
Diagnosis is based on epidemiological characteristics, typical symptoms and characteristic lesions during autopsy. However, to ensure accuracy, it is necessary to distinguish
Newcastle from several diseases with similar symptoms such as: Chicken typhoid, septicemia, avian influenza, ...
b. Paraclinical diagnosis
Pathological samples are often taken from the brain, spleen, liver or excretion, then sent to
FiveLab - Veterinary Diagnostic Testing Center. With a modern testing system,
FiveLab provides fast and accurate results, helping veterinarians and breeders identify diseases promptly and develop effective treatment regimens. Contact now 0822 120 555 or 0972 249 555 for
FiveLab's fastest consultation and testing support!
6. Preventing Newcastle disease in poultry
- Preventing disease by vaccination using the following products:
Five-ND.IB ,
Five-Lasota ,
Five-Newcastle (M strain) ,
Five-Newcastle (G7) ,
Five-ND.IB AI (H9N2) ,
Five-ND.IB.EDS , ... according to each farm's schedule.
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