Overview of Ranikhet Disease
There are various synonyms for this disease in which ‘Ranikhet Disease’ (RD) is most popular in India while ‘Newcastle Disease’ (ND) in the West.
In India, farmers are facing frequent outbreaks and heavy losses leading them to close their farms. The mortality percentage is as high as 100% in chicks. In layers, an early symptom is shell-less or soft-shelled eggs, followed by the complete stoppage of laying. That is the reason this disease still ranks as one of the most serious viral diseases of poultry.
Ranikhet disease is largely a disease of chickens, but it also affects turkeys, pigeons, ducks, geese, guinea-fowls and doves. Laboratory workers and persons handling infected birds may feel severe conjunctivitis.
It is a very severe, sudden, and rapidly spreading disease; and may be seen from 6 to 7th day onward up to 72 weeks. Ranikhet Disease occurs throughout the year but is most common in the summer.
The incubation period for the disease ranges from 4 to 6 days. An infected bird may exhibit several signs, including respiratory signs, nervous signs, swelling of the tissues around the eyes and neck, greenish, watery diarrhoea, misshapen, rough or thin-shelled eggs and reduced egg production.
The main causative agent for this disease is a variant of avian paramyxovirus 1 (APMV-1). We can categorise the strains of this virus as Velogenic (highly virulent), Mesogenic (intermediate virulence), or Lentogenic (non-virulent).
Mode of Transmission:
Transmission occurs through;
The virus spreads through the air.
Infection occurs mainly through inhalation or ingestion.
Contaminated feed and water spread infection.
Movements of people and equipment also spread infection.
Ranikhet Disease virus survives for days to weeks in the shed.
In the dead bird or faeces, the virus can survive for several months.
Sign and Symptoms:
Depending on the nature of the Ranikhet disease virus, symptoms vary.
The first indication is sudden death. Then, symptoms such as depression, weakness, lying down, green diarrhoea, swelling of the face, and nervous signs may appear, ending in exhaustion and death.
Signs also include twisting of the neck, arched position of the body and paralysis of legs. Severe respiratory disease and respiratory symptoms.
In adult birds, there is a marked drop in egg production for several months. Mortality is low. The affected birds are dull and depressed with ruffled feathers. The saliva often accumulates in the mouth and obstructs respiration, which results in the production of gurgling sound.
These symptoms are accompanied by diarrhoea with an offensive smell.
* The pinpoint haemorrhages on the tip of the proventriculus.
* Enlarged and haemorrhagic caecal tonsils.
* Haemorrhagic lesions on the intestinal wall.
* Spleen shows necrosis on its outer surface.
* Marked congestion of trachea, often with haemorrhages.
Ranikhet Disease Virus Isolation:
For routine isolation of NDV, we should collect a sample by swabbing the trachea and the cloaca. Cotton swabs will be the best choice. We can isolate the virus from the lungs, brain, spleen, liver, and kidneys.
Before sending it to laboratory, We should store samples at 4°C (refrigerator) and place it in a padded envelope or box. Make sure that it is reaching overnight to the laboratory for further investigation.
Enzyme-linked immunosorbent assay, polymerase chain reaction, and sequence technology tests have been used to identify and confirm the disease.
Treatment of Ranikhet Disease:
There is no drug available for the treatment of this disease. We use broad-spectrum antibiotics to cover systemic/secondary bacterial infection and immune boosters for fast recovery.
* Birds showing symptoms of Newcastle disease should be isolated immediately.
* New birds should also be vaccinated before being introduced to a flock.
However, under field conditions vaccination alone is not sufficient to control RD. It must, therefore, be accompanied by good hygiene, good management and good biosecurity practices.