November 2018 Punch PDF

Infectious viral diseases of chicken
Dr. Satuti Sharma (PhD Scholar), Dr. Shilpa Sood (Associate Professor), Dr. Nawab Nashiruddullah
(Professor), Dr. Shafiqur Rahman (Assistant Professor), Dr. Sankalp Sharma (PhD Scholar), Dr. Prabjot
Singh (MVSc), Division of Veterinary Pathology, F.V.Sc & AH, SKUAST- Jammu, J&K, India (181102).
Introduction: Respiratory infections in chicken are seen worldwide but especially in temperate poultry-producing areas
in winter months. There are many common viral diseases which can affect the respiratory system (air passages, lungs, air
sacs) of poultry. Dust, ammonia and other gases, and other factors associated with poor ventilation, may act as predisposing
factors. Morbidity is typically 10-20%, mortality 5- 10%. If condemned birds are included mortality may be more than 10%.
Ranikhet disease: Ranikhet disease also known as Newcastle disease is highly contagious of chicken caused
by paramyxovirus. There are five main forms of the disease: the highly pathogenic viscerotropic velogenic, neurotropic
velogenic, mesogenic, mildly pathogenic is lentogenic and lastly is asymptomatic. In case of severely pathogenic form of
the disease there is very high morbidity and mortality. Within a span of three or four days most birds on the farm can get the
infection. In disease produced by less severe stains of the virus, the birds may remain asymptomatic. However, in birds that
survive or those suffering less virulent form of the disease, the case get complicated and the birds become predisposed to
develop secondary bacterial infections like Collibacillosis or mycoplasmosis.
Spread: The disease can spread mechanically by means of contaminated equipment, shoes, clothing and aerosol.
Recovered birds are not known to act as carriers. The virus can be transmitted by contaminated equipment, shoes, clothing
and free-flying birds.
Clinical Signs: In virulent forms of the disease, the sick birds exhibit clinical signs reflecting the involvement of
respiratory system, nervous system and digestive system. Signs of respiratory system involvement are non specific and
include nasal discharge, difficulty in breathing, gasping and sneezing. Birds also show nervous signs which are manifested
as paralysis of wings, legs or twisting of the head and neck. Birds may also suffer from diarrhea.
Lesions: Gross lesions are seen in the digestive tract or respiratory tract. Varying amounts of mucous can be seen
in the trachea. Sometimes, there may be presence of casts or plugs in the air passages of the lungs and cloudiness of the
air sacs. Lungs may be congested. In the viscerotropic velogenic form of disease, which affects the digestive tract, lesions
include presence of haemorrhages in proventriculus, especially at the tip of proventriculus glands, and necrotic lesions or
ulceration elsewhere in the intestinal tract especially involving the region of caeca and caecal tonsils.
Vaccination and Prevention: Vaccination is the recommended method for prevention. Use of the mild live virus
vaccines called as the B1and LaSota commonly done for prevention of the disease. The vaccines are applied into the nostril
or eye or added to the drinking water or applied in the form of spray. Broiler chickens are usually vaccinated when seven to
ten days of age. Chickens kept for egg production are usually vaccinated at least three times. The vaccine is given when
birds are approximately seven days, again at about four weeks and a third time at about four months of age. Revaccination
while in lay is commonly practiced. There is no treatment for Newcastle disease. Good management programs and good
“biosecurity” measures may reduce the occurrence of Newcastle disease virus.
Infectious Bronchitis: Infectious bronchitis caused by corona virus is an extremely contagious acute respiratory
disease of chickens. The disease is characterized by coughing, sneezing and respiratory rales (rattling).In young chickens,
there is severe respiratory distress occur. In layers, respiratory distress, nephritis, decrease in egg production, and loss of
internal quality and external egg quality are reported.
Spread: The disease is transmitted by aerogenous route. Other modes of spread of virus include spread by mechanical
means such as clothing, poultry crates and equipment. The disease is also spread by droplet infection through the air, from
bird to bird. The virus may also be spread by contaminated material and equipment, and via faeces.
Clinical Signs:There many different strains of the virus and can affect different organ systems like respiratory tract,
reproductive tract and kidneys. In broilers, the infection is mostly confined to the respiratory system. Symptoms are difficulty
in breathing, gasping, sneezing, rales and watery nasal discharge. In chickens under three weeks of age, mortality may
reach thirty or forty percent. In birds over five weeks of age, this disease does not cause a significant mortality. Feed
consumption decreases sharply and growth is retarded. When infectious bronchitis occurs in a laying flock, production
usually drops to near zero with a few days. Four weeks or more may be required before the flock returns to production. Some
flocks never regain an economical rate of lay. During an outbreak, small, soft-shelled, irregular-shaped eggs are produced.
Lesion: The trachea, sinuses, and nasal passages may contain serous, catarrhal, or caseous exudates and the air
sacs have foamy exudates initially, progressing to cloudy thickening. Birds infected when very young may have cystic
oviducts, whereas those infected while in lay have an oviduct of reduced weight and length and regression of the ovaries.
114 November, 2018