Infectious laryngotracheitis (ILT) infections in small poultry flocks
Marina Brash, Csaba Varga, Al Dam, Lloyd Weber
Below is an excerpt from AHL LabNote 58, which can be shared with small flock owners:
Quick facts about ILT:
- Infectious laryngotracheitis (ILT) is a contagious viral respiratory disease, primarily of chickens and gamebirds, that can cause elevated morbidity and mortality.
- Small non-commercial chicken flocks are more likely to be infected with the ILT virus than commercial chicken flocks.
- The incubation period is 4-7 days; subclinically infected chickens can easily be introduced into a naive flock.
- The virus can survive in expelled ocular, nasal, and tracheal discharge in the environment for several days to months at room temperature. The virus can survive for even longer periods of time if kept cold or frozen (e.g., in buried infected carcasses).
- ILTV is an enveloped virus and is sensitive to heat, direct sunlight, and common disinfectants. However; disinfectants are less effective in the presence of organic matter such as fecal material.
- ILTV can be introduced into small flocks via infected live birds and numerous vectors and fomites.
- ILTV can persist for extended periods of time in birds that have recovered from the disease or have been previously vaccinated with either the live attenuated ILT vaccine of chicken embryo origin (CEO) or tissue culture origin (TCO).
- Both the field and CEO vaccine strains of the virus are more likely to be re-activated during periods of stress, allowing the infection to spread to susceptible, unvaccinated birds.
- To prevent infections, it is important that all of the chickens in a flock are annually vaccinated, and good biosecurity protocols are in place.
- For more information about disease vectors and proper biosecurity protocols for small flocks, please visit the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) website at: http://www.omafra.gov.on.ca/english/livestock/poultry/health.html
How to diagnose ILT:
Typically, chickens older than 3-4 wk are most susceptible to ILTV. In the acute phase of disease, the birds may just be found dead or have:
- swollen eyelids and/or infraorbital sinuses;
- sneezing and bubbly ocular and nasal discharge.
The birds are in respiratory distress, and may have:
- extended heads and necks to aid breathing,
- gasp or cough up blood-tinged mucus or exudate,
- increased mortality in the flock.
At postmortem, birds may have:
- ocular and nasal discharge,
- plaques of pale fibrinous exudate on the oropharyngeal and esophageal mucosa (Fig. 1),
- laryngeal opening plugged with fibrinous exudate (Fig. 1),
- reddened tracheal mucosa with luminal blood or fibrinous exudate (Fig. 2).
Diagnosis of ILT can only be confirmed by identifying the herpesvirus through laboratory testing such as postmortem, histology, and virology. This is important because other viral and bacterial respiratory pathogens can cause similar clinical signs. AHL
Figure. 1. The laryngeal opening is occluded by fibrinous exudate (arrow). Plaques of fibrinous exudate are on the oropharyngeal and esophageal mucosa.
Figure 2. There is fibrinous exudate in the laryngeal opening and also in the tracheal lumen. The tracheal mucosa is hyperemic. A few small plaques of fibrinous exudate are also on the oral and esophageal mucosa.