Ranikhet Disease:

Syn: New Castle Disease, Avian distemper, Doyle’s disease

• It is highly infectious, acute, rapidly transmitting viral disease of domestic poultry and other avian groups.
• It is characterized by respiratory signs; distress, coughing, sneezing, nervous signs leading to wing paralysis, incoordination, torticollis, swelling of head and chalky white diarrhea.
• It causes significant losses in poultry through morbidity, mortality and drop in egg production.

Etiology:

• Avian paramyxovirus-I, NDV, Paramyxoviridae family
• RNA virus
• Classified into three main types; velogenic, mesogenic and lentogenic strain based on their pathogenicity.

Epidemiology:

• Virulent NDV are endemic in poultry in most of Asia, Africa, Mexico and some countries of South America.
• Chickens are most susceptible and waterfowl are least susceptible.
• It is distributed globally.
• Disease was first recorded in New Castle, U.K by Doyle in 1926.
• In India, it was recorded in 1927 by Edward from Ranikhet hilly station of Uttaranchal.
• Heavy mortality ranging from 50-100%.
• Concurrent outbreak of disease along with infectious laryngotracheitis in Punjab has been reported.
• Virus having affinity for respiratory tract is known as Asiatic form of virus, virus affecting GI tract is viscerotropic and nervous system; neurotropic virus.

Transmission:

• Chickens are infected with droplet (aerosol) method.
• Infection may spread through feces, eggs and infected carcasses.
• Coughing and sneezing may shed huge quantity of virus and contaminate house, equipment, clothing.
• Virus also transmits through contaminated beddings, incubator and infected eggs.

Pathogenesis:

• Inhalation or ingestion of virus
• Virus multiply in upper respiratory tract
• Acute respiratory signs; coughing, sneezing, dyspnea
• Virus in blood (viremia)
• Virus reaches CNS via blood leading to depression, circling and paralysis
• Virus reaches GI tract which causes diarrhea.

Clinical Signs:

• Clinical signs observed in birds depends on virulence of strain.
• Mortality reaches upto 100% and morbidity rates varies among species and strain of virus.
• Sudden death, depression, Inappetance.

a. Respiratory and Nervous Signs:

• Gasping and coughing
• Drooping wings
• Dragging legs
• Twisting of head and neck (torticollis)
• Circling, depression
• Inappetance, complete paralysis

b. Gastrointestinal Signs:

• Dullness, depression
• Birds pass watery diarrhoeic feces- color varies from greenish to white chalky
• Sharp decline in egg production; eggs are abnormal in shape, thin-shelled, watery albumen

c. Other Signs:

• Swelling of tissues and around eyes and in neck.

Post-Mortem Findings:

• Pinpoint hemorrhage on the tips of proventriculus glands
• Air sacculitis; cloudiness of air sac
• Hemorrhage under the horney layer of gizzard.
• Hemorrhagic lesion in intestine; ulceration or bran-like deposition.
• Congestion of mucosa in trachea, lung tissues.
• Degeneration of nerve fibres, neuron and ganglionic cell of spinal cord
• Degenerative changes in ovary
• Hemorrhagic kidney
• Hemorrhages in spleen

Diagnosis:

• Based on clinical findings
• Based on PM findings
• Isolation and identification of virus by inoculation of tissue suspension in week old, embryonated eggs by chorio-allantoic route.
• Serological tests; HA, HI, CFT, VNT, FAT, PCR

Differential Diagnosis:

a. Infectious bronchitis (IB):

• Respiratory symptoms are more marked.
• Air sacculitis
• Eggs are of abnormal shape and usually of low quality
• Low production

b. Infectious laryngotracheitis (ILT):

• It is more prevalent in adult birds.
• Prolonged drop in egg production
• No abnormality in egg
• No involvement of air sac
• Hemorrhage in larynx and trachea

c.  Avian encephalomyelitis (AE):

• Young birds are usually affected.
• It spreads slowly in flock.
• There is no involvement of air sac.
• No enlargement of spleen.
• Nervous signs usually include ataxia, paralysis, nodding of head, torticollis.

d. Avian influenza (AI):

• Respiratory signs are more marked.
• Greenish diarrhea
• Edema of head and neck
• Slight decrease in egg production
• CNS involvement

e. Vitamin E deficiency:

• Young birds are affected.
• Prostration, unable to move
• Birds move in circle.
• Body cavity is filled with gelatinous exudate
• Cavity formation in brain.

f. Marek’s disease:

• Disease is slow spreading
• Paralysis of wings and legs
• Enlargement of brachial and sciatic nerves
• Infiltration of lymphocytes and plasma cells in nerve fibres.

Treatment:

• No effective treatment is available. Broad-spectrum antibiotics may be tried to prevent secondary bacterial infections.

Control Measures:

• Standard hygienic measures and sanitary measures are to be adopted.
• Sick birds should be segregated immediately from rest of flock.
• Strict biosecurity measures should be adopted in farm.
• Disposal of dead birds with proper care with bleaching powder or lime.
• All in and all out methods should be adopted to control disease.
• Entry of visitors should be restricted.
• Contaminated food and water shouldnot be used.
• Disinfection of premise should be made. It may be done with 2% sodium hydroxide or 1 in 1000 Lysol.
• Fumigation of house, hatchery or incubators is to be done for every 100 cubic feet area, 20g KMnO₄, with 40 ml formalin should be used.
• Vaccine should be used; 3 types of vaccine are used:
  • Lasota strain or F-strain:
    • 4-10 days- intraocular or nasal drop
    • 4-5 weeks- intraocular or DW
    • 15-16 weeks- Drinking water as 2^ndD
  • R₂B vaccine:
    • 8-10 weeks of age, booster at 17 weeks for commercial layer
    • At 6 weeks following F₁, in general @0.5 ml IM or SC by needle of 20-22G.
  • ND killed vaccines:
    • Layer and broiler flock at 16^th-20^th
    • Dose: 0.2 ml