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Transcript
Infectious Bronchitis Virus (IBV)
• Group 3 coronavirus
• Main cause of economic loss in poultry farms
•
•
•
Young chickens
Broiler chickens
Layers
healthy chicks
IBV-infected egg defect
IBV-infected
embryo
normal
embryo
Infectious Bronchitis
• An acute, highly contagious respiratory disease of
chickens.
• All ages infected; particularly a problem in laying
flocks.
• Chicks - growth suppression & predisposition to
other diseases.
• Hens - variable production loss and affects egg
quality.
• Turkeys resistant.
Etiology
• Coronavirus - The positive sense RNA - heat sensitive.
• Many serotypes and strains with great antigenic variation have been
identified.
• Mass 41 & Conn 46 are used as vaccine and protect against closely related
serotypes.
• Different strains affect different organ systems: respiratory, renal,
reproductive.
• Some important field strains are JMK, Ark. 99, Fla. 88, Holland, 072, GA
variant, and many others.
• The QX type virus causes a severe disease including nephritis in young
birds, high mortality, respiratory distress in broilers and drops in egg
production in breeders and layers (false layer syndrome).
• In Iraq CH Baghdad F1 2013, CH Babylon F2 2013 were genetically close
related with variant strain IB Egypt 12177.1FSP1 and IS/885 and
IS/1494/06.
Taxonomy of the IBV
• Infectious bronchitis virus belongs to the order Nidovirales.
• family Coronaviridae.
• genus Gammacoronavirus.
• The Coronaviridae comprises two genera, Corona virus and
Toro virus.
• Corona viruses are divided in to three groups, IBV is
placed in group three .
Incubation Period
• 18-36 hours - used in diagnoses.
• Rapid spreading and highly contagious.
Course of Disease
1-2 weeks, secondary problems can linger.
Predisposes birds to chronic respiratory
problems.
Method of Spread
• Airborne aerosol from infected birds ( respiratory tract).
• Direct contact with short time carriers.
• fecal transmission and fomites.
• Virus shedding lasting for several weeks after infection and persistent
carriers may be present.
• Disease also transmitted through materials, equipment and movement of
field worker from the infected flocks to health farm also movement of live
birds.
• Wild birds may play a crucial role as reservoirs and long-distance carriers
of IBV.
Mortality
• Respiratory IB usually not significant but in recent year high mortality nots
- although tracheal plugs at the bifurcation cause asphyxiation.
• Some serotypes can cause serious airsacculitis.
• Depends on secondary infection such as Mycoplasma.
• Nephrotropic strains may cause high mortality in chicks and layers. Causes
urolithiasis.
• Nephrotropic strains include Holt and Gray.
Clinical Signs
CHICKS –
The nature and severity of the disease are influenced by the age
and immune status of the flock and virulence of the causal
strain.
The main clinical signs were restless and huddled together,
difficult in breathing, gasping, coughing, sneezing, tracheal
rales, nasal discharge, wet eye and swollen sinus, ruffled
feathers, morbidity up to 100%
• Facial swelling may also occur occasionally, particularly with
concurrent bacterial infection of the sinuses.
• Depressed and cold decrease of feed intake and conversion,
loss of body weight
• increased water intake, wet droppings, depression,
lethargy and poor growth in broilers
Nephropathogenic strains can produce interstitial nephritis
with high mortality (up to 60%) in young chickens. In most
outbreaks, although secondary bacterial infections may cause
higher losses.
Clinical Signs
LAYERS • Rales and seldom have nasal or ocular discharge.
• Egg production may drop 20-50%.
• mainly affects egg quality (thin, rough, fragile,
misshapen egg shells and thin watery egg) and
causes decrease in egg production In some cases the
virus infection may cause severe damage to the
oviduct and result in decreased or permanent loss of
egg production
Postmortem Lesions
CHICKS AND BROILERS
• Infected chickens have serous, catarrhal or caseous exudates may be seen
in the trachea, nasal cavity and sinuses
• Congested blood vessels in trachea and caseous plugs of mucus in the
primary bronchi (Tracheal plugs at the bifurcation)may followed secondary
infection and cause asphyxiation. Lungs may appear congested and
airsacculitis is common Slight airsacculitis - severity varies with serotype of
IBV.Ark causes airsacculitis.
• Nephropathogenic strains, the kidneys become pale and swollen and urate
deposits may form in the kidneys and ureters
Postmortem Lesions
PULLETS AND LAYERS
• Hyperemia of trachea
• Serous & catarrhal exudate of trachea
• the ovarian follicle may be flaccid, Deposition of yolk material in the
peritoneal cavity (egg peritonitis) is common Salpingitis & permanently
damaged oviduct.
• Infection of 2-3 week old pullets with IBV may cause infertility,
salpingitis, and internal laying.
• Swollen kidneys with urates
• Necropsy finding of bird infected with QX strain frequently showed either
cystic oviduct with watery contents that could exceed one liter or partially
atrophic oviduct with large cystic dilatation .
Differential Diagnosis
•
•
•
•
•
Newcastle Disease
Laryngotracheitis (ILT) - slow moving
Infectious Coryza(Haemophilus gallinarum) - swollen head
Avian Influenza
turkey rhinotracheitis (TRT) also causes a swollen head
syndrome
Diagnosis
• History of fast spreading respiratory disease
• ELISA - uses Mass. antigen but get cross reaction with other
serotypes.
• HI - IBV is treated with neuraminidase enzyme before testing
because IBV is not naturally hemagglutinating.
• VN - rises in titer between paired serum samples (2 wks.
apart)
• Agar-gel precipitation test (AGPT)
Diagnosis
• Isolation and identification of virusembryonating eggs – stunting, curled, and
hemorrhagic - vaccine strains are embryo
adapted and often affect embryos on the 1st or
2nd passage whereas field strains may require
additional passages before lesions appear.
• Identification of IBV serotype - PCR, monoclonal
antibody test, etc.
• Detection of virus genome (RT-PCR)
Stunted, Curled Embryos
Prevention
Establish and enforce a biosecurity program.
Vaccination - complete prevention of IB is
difficult because of variation of field strains
and the ability of the virus to change. There is
little cross protection between serotypes.
Prevention (Cont.)
VACCINES:
LIVE - Monovalent - usually Mass
Bivalent - Mass. & Connecticut
Other attenuated strains such as Holland
andArk. 99 are used as vaccines.
Prevention (Cont.)
VACCINES:
KILLED - used in breeders and layer pullets to
prevent production losses and produce
consistently high antibody titers.
Prevention (Cont.)
• Management Procedures
• Ideal management includes strict isolation,
high biosecurity, and repopulation with only
day-old chicks following the cleaning and
disinfection of the poultry house and
equipment in contact with poultry or poultry
litter and removal of the feces from the
premises.
Treatment:
 None for the virus (acyclovir, amantadine)
 Broad spectrum antibiotics for secondary bacterial involvement