Infectious laryngotracheitis is a highly contagious respiratory disease of chickens caused by an alpha herpes virus. It results in severe breathing difficulties and coughing due to laryngitis and tracheitis. The virus can survive for weeks in the environment and is transmitted between flocks through contaminated equipment, litter and people. Clinical signs include eye discharge, coughing and the expectoration of blood from the trachea. Prevention relies on vaccination of chickens with modified live vaccines starting at 2-4 weeks of age.

1. INFECTIOUS
LARYNGEOTRACHEITIS

2. Laryngeotracheitis
 Infectious laryngeotracheitis (ILT),
 Avian diphtheria
History:-
 First described 1925 in Canada
 Australia and Great Britain in 1935
 Isolated (1930)
 Caused by alpha herpes virus (Beaudette 1937)

3. Etiology
 Alpha herpes virus commonly known as
infectious laryngotracheitis virus (ILTV)
 Double stranded DNA (155kb)
 Enveloped
 Size: 195-250 nm

4. Aetiology strain differentiation
 Based on virus neutralization (VN),
immunofluorescence (IF) and cross-
protection studies, ILTV strains are
considered to be Antigenically homogeneous.

5.  Infectious laryngotracheitis virus is an acute,
highly contagious infection of chickens and
pheasants.
 Result in severe production losses due to
mortality and/or decreased egg production.
 Characterized by severe dyspnoea,
coughing, expectoration of bloody exudate
and severe necrotizing laryngitis and/or
tracheitis.

6. Survival out the Host
 Virus survives for 47 days at room
temperature on swabs, for 8-10 days in
droopings at 10-23c° and for 21-27 days in
carcass.
 Virus is destroyed in 44 hours in the trachea
tissue of an unrefrigerated chicken carcass.

7. Susceptible Hosts
 Primarily in chickens
 Usually older birds
 Pheasants & pheasant crosses are rarely affected.
 Virus has been isolated from trachea of Peafowl.
 Other birds resistant (ducks, pigeons, doves,
sparrows, crows, starlings, guinea fowl).

8. Physical/Chemical Susceptibility
 Susceptible to heat
 Susceptible to many chemicals
 Chloroform, ether, iodophors, cresols,
 Hydrogen peroxide fumigant (5%)

9. Structure Of Virus

10. Transmission
 Between flocks
 Mechanical carriage of infective foci such
contaminated implements, feathers, litter,
clothing, poultry dust and faeces, broken
eggs and faeces dried on egg trays and
equipment are a good source of infection.
 Purchased sick and carrier birds.

11. Transmission
Horizontal transmission
 Aerosolization of virus
 Birds, feed, water
 Contaminated litter
 Fomites (equipment, boots, clothes)
No vertical or egg transmission known

12. Factors influencing susceptibility
 More prevalent in cold months.
 Clinical disease is more severe in hotter
climates.
 Occurs from year to year on the same
premises or in the same general areas.
 Seen mainly in mature age.
 Male are more susceptible

13. Pathogenesis
 Virus present in trachea for 6-10 days PI
 Inflammation and necrosis (tracheal cores)
 Produce intranuclear inclusions in the
epithelium of infected birds.
 Necrotic cells, blood, inflammatory debris,
cellular edema
 High virus shed during infection
 Leads to Death b/c of asphysia

14. Clinical Signs
 Acute respiratory disease
 Conjunctivitis – almond eye (often first signs)
 Nasal discharge
 Moist rales, coughing, gasping
 Dyspnea
 Expectoration of blood (only in severe infections)
 Decreased production
 Egg production 5-15%: no problems with shell quality
 Unthrifty birds
 Recovery in ~7-28 days (usually 10-14 days)
 Duration ~2-6 weeks in flock

15. Clinical Signs
 Incubation 6-12 days post infection (PI)
 2-4 days experimentally
 Severe
 90-100% morbidity
 5-70% mortality
 Mild (‘silent LT’)
 As low as 5% morbidity and 1% mortality

16. Clinical Signs

17. Clinical Signs

18. Clinical Signs

19. Gross Necropsy
 Conjunctivitis and sinusitis
 Hemorrhage, edema
 In mild cases, may be only sign (inflammation)
 Laryngotracheitis
 Mucus, hemorrhage
 Tracheal plug
 Lungs are normal or show congestion

20. Gross Necropsy

21. Diagnosis
 Clinical signs
 Histopathology
 Virus isolation
 Detection of LT antigens
 Detection of LT viral DNA
 Electron microscopy
 Serology

22. Gross Necropsy

23.  Type A intranuclear inclusions
 3 day PI (only found for ~ 1-5 days)
 Syncytia (multi-nucleated giant cells)
 Epithelial edema, enlargement, and decilliation
 Inflammatory cells mucosa
 Loss of goblet cells
 Separation of epithelial layers
 Sloughing into lumen
Histopathology

24. Differential Diagnosis
 Pox (diptheretic or wet)
 Infectious bronchitis
 New castle disease
 Coryza
 CRD
 Avitaminosis

25. Prevention and Control
 Avoid mixing of vaccinated or recovered chickens
with susceptible chickens
 Contaminated litter
 Fomites
 Anything that has contacted infected/vaccinated
birds
 Boots, hands, clothes, equipment, vehicles
 People, rodents, wild birds, and dogs may
 mechanically carry LT

26. Prevention –
MLV (Vaccine Program)
 Broiler vaccination 2-4 wks of age
 Frequently given in drinking water
 May be as early as 10-12 day.
 Immunity to 8-15 wks post vaccination
 Breeders: (re)vaccinate at 10-12 wks of age
 Eyedrop
 Layer vaccination ~ 7 & 15 weeks of age

27. THANKS