Download Infectious-laryngotracheitis-2010

INFECTIOUS
LARYNGOTRACHEITIS
Infectiöse Laryngotrachitis
Infekční laryngotracheitida
Infectious Laryngotracheitis
• viral respiratory disease affects chicken.
• first report in USA in 1924
• It is recognise worldwide.
• Serious disease outbreaks occur periodically when
strains of infectious laryngotrachitis viru (ILTV) spread
from persistently infected flocks to nonvaccinated birds.
Infectious Laryngotracheitis
Cause
Family Herpesviridae
Subfamily Alfaherpesvirinae
Gallid herpesvirus 1
(Iltovirus =ILT-like virus)
Field strains may show considerable variaton in virulence.
Infectious Laryngotracheitis
Host
Naturally infect only domestic fowl and occasionally
pheasants.
All age of fowl are susceptible, the disease is most
commonly seen in field in birds 3-9 months old.
In general males are more susceptible then females and
heavier breeds more susceptible than light ones.
Disease my be exacerbated concurrent infection with
variety of others patogens such ND, infectious bronchitis
and fowl pox viruses, and Haemophillus paragalinarum
and Mycoplasma gallisepticum.
Infectious Laryngotracheitis
Spread
Virus enters the bird in infective droplets or mucus via
the upper respiratory tract and cunjunctiva.
It is shed mainly in exudates from nares, oropharynx,
trachea and conjunctiva an is transmitted in aerosol or
expectorant form (blood or mucus).
The virus remains in latent form in the trigeminal ganglia
in brain.
Source of infection
living infected bird, fomite
mechanical cariers – personnel, wild birds
Infectious Laryngotracheitis
Clinical sings
period of incubation
6-12 days
possible
peracute
acute
or mild or asymptomatic infection
Infectious Laryngotracheitis
Peracute form
• Sudden acuted dyspnoe with severe coughing and
expectoration of mucus, blood stained exudate or
blood clots.
• Spreading of disease is very fast
• High morbidity 70% of affected birds may die,
mortality more then 50%
Infectious Laryngotracheitis
Peracute form
Lesions
– haemorrhagic tracheitis in which the trachea contains blood
cast throughout the whole or part of its length or is filled
with blood-stained mucus
– respiratory obstruction
Infectious Laryngotracheitis
Acute form – clinical sings
•
Dyspnoe, but with not as sudden in onset
•
Breathe with a wide-open beak
•
Moist rales can be heard
•
Nasal discharge and conjunctivitis with frothy exsudate
•
morbidity is high, mortality 10 - 30%
•
Drop in egg production – loss 60 %
Lesion
– mukoid exsudate with or without blood in trachea
– Caseous diphteric exsudate
– Obstructive plugs in laryng and syring
Infectious Laryngotracheitis
Mild form
Clinical sings
• moist rales, slight coughing and head shaking
• nasal exudate, conjunctivitis
Asymptomatic form
• without clinical sings and its presence in small flock
may go undetected
Infectious Laryngotracheitis
Others patological findings
• in peracute and acute forms very good body
condition of dead birds
• atrophy of ovary
• congestion of lungs
• thickening of air sac walls
Infectious Laryngotracheitis
Diagnostic methods:
• histological examination of trachea
• virus detection
• antibody detection
Infectious Laryngotracheitis
Histological findings in trachea
• inflamatory response and necrosis with or without haemorrhage
• diagnostical sings – presence of intranuclear inclusion bodies Cowdry
type A in some epithelial cells
• are present only for a few days before desquamation of epithelial cells
Infectious Laryngotracheitis
Virus detection/isolation
• embryonated eggs or cell cultures
• samples – exudate, epithelial scrapings or tracheal
swabs
• Inoculation on chorioallanoic membrane (CAM)1012 day-old eggs
– positive findings – production of posck on CAM
• on monolayer of chick embryo liver cell cultures
– positive findings – syncytium formation after several days
Infectious Laryngotracheitis
Rapid methods
- Immunofluorescence or immunoperoxidase
staining of tracheal sections
- antigen capture ELISA
- electron microscopy – negative staining
- DNA hybridization techniques
- PCR
Infectious Laryngotracheitis
Serology
Aim– detection of antibodies to ILTV in chicken serum
Methods
AGID – agar gel imunodiffusion
Virus neutralisation – gold standard (time consuming)
Indirect immunofluorescence – serum to fixed cell cultures
ELISA – ease testing of large numbers of sera with
commercial kits
- system of choice for flock testing
Infectious Laryngotracheitis
Vaccination
Live vaccine
in area with no-high risk in age between 3 and 18 weeks
repeated vaccination past 2-3 weeks
Methods
- eye drop vaccination, coarse spray, inclusion in the
drinking water
Disadvantage
- Possibility of latent infection, in first occurence is better
destock completely and clean and disinfect