Respiratory disorders in poultry often become a serious threat to farms and can even turn into routine problems that are difficult to control. One disease that is often unnoticed and spreads silently on farms is Infectious Laryngotracheitis (ILT). The symptoms of ILT resemble those of other respiratory diseases, which often leads to misdiagnosis and inappropriate treatment. Mortality in poultry infected with ILT can increase if the disease is not properly managed. The World Organisation for Animal Health (WOAH) in 2021 stated that vaccination can help protect poultry from infection, while biosecurity measures can prevent the spread of the virus.
Understanding Infectious Laryngotracheitis (ILT)
Infectious Laryngotracheitis (ILT) is a respiratory disease in poultry caused by Gallid alphaherpesvirus 1 (GaHV-1), commonly known as ILTV. The virus belongs to the Alphaherpesvirinae subfamily within the Herpesviridae family (Yunita et al., 2025). Chickens are particularly susceptible to the virus, although peafowl, pheasants, and partridges can also be infected (WOAH, 2021).
Figure 1. Structure of the ILT virus: schematic diagram of the virus (a) and ILT genome (b) (Mo and Mo, 2025).
Transmission occurs through direct and indirect contact with the environment. ILT can lead to decreased production and weight loss in chickens. According to WOAH, the morbidity rate can reach 90–100%, while mortality may exceed 50%.
One of the major challenges in controlling ILT is the virus’s ability to hide in nerve tissue and remain latent. The virus can reactivate when chickens experience stress and their immunity declines, triggering new outbreaks. Therefore, prevention and control measures are crucial to protect poultry farms.
ILT can enter farms through multiple routes—not only via infected birds but also through the surrounding environment. Newly introduced chickens that have been exposed to the virus, even if they appear healthy, can bring the virus into the farm. Human activity can also contribute significantly to disease spread if strict biosecurity procedures are not followed.
Close distances between farms and wind direction may also facilitate viral spread. Additionally, equipment that is not properly cleaned and disinfected can become a transmission route. Therefore, strict biosecurity procedures and routine cleaning of farm equipment are essential to prevent ILT transmission (Pajic et al., 2022).
Figure 2. Routes through which the virus enters farms and infects other chickens (personal illustration).
ILT Threat in Indonesia Over the Past Three Years
Based on data collected by the Medion surveillance analyst team, suspected ILT cases remain a serious issue in Indonesia. During 2022–2024, a total of 1,017 reported cases were identified based on clinical findings and necropsy lesions in chickens. In 2025, 98 cases were already reported between January and April.
An increase in ILT cases occurred toward the end of 2024, particularly during the rainy season.
A recent study conducted by Saepulloh et al. (2025) found that farms in Bogor, Bekasi, and Cianjur showed chickens with acute respiratory symptoms associated with ILT infection. Meanwhile, in Tangerang, no positive ILT cases were detected through PCR testing, although clinical symptoms were still observed.
These findings provide a general overview of the disease situation and indicate that ILT remains a real threat to poultry farms in Indonesia. Therefore, farmers and the poultry industry must remain vigilant and take steps to control the spread of ILT.
Clinical Signs of ILT and Organ Changes: What Should You Watch For?
ILT is a disease that can cause sudden death in poultry and can affect birds of all ages. The severity of ILT cases depends on several factors, including virus virulence, stress conditions, co-infection with other pathogens, flock immunity status, and the age of the birds (Saepulloh et al., 2025).
According to Gowthaman et al. (2020), ILT has three clinical forms:
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Peracute
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Acute
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Chronic
Each form presents different clinical symptoms. Clinical signs and organ changes observed during necropsy can be seen in Figures 3 and 4.
Long-Term Prevention and Control Plan for ILT Outbreaks
**Infectious Laryngotracheitis can cause significant losses if not handled properly. Since ILT is caused by a virus, antibiotics are not the primary solution for controlling outbreaks.
The following long-term prevention and control plan is recommended (Zavala 2007; Volkova et al., 2012; Manisaran et al., 2025):
| No. | Step | Action |
|---|---|---|
| 1 | Diagnosis and Surveillance | Conduct rapid and accurate ILT diagnosis based on clinical signs and organ lesions. WOAH recommends laboratory methods such as virus isolation, immunofluorescence, PCR, ELISA, histopathology, and virus neutralization tests. Continuous monitoring of farm conditions is also necessary. |
| 2 | Isolation and Quarantine | Isolate infected birds and quarantine the affected house to prevent viral spread. |
| 3 | Biosecurity | Implement strict biosecurity measures, such as dividing clean and dirty zones, using footbaths, changing boots, and ensuring workers shower and change clothes before and after entering poultry houses. |
| 4 | Vaccination | Vaccinate chickens using live or recombinant vaccines to help prevent disease outbreaks. |
| 5 | Environmental Management | Improve house ventilation to reduce humidity, ammonia levels, and airborne transmission. Ensure proper disposal and decontamination of litter and equipment. |
| 6 | Monitoring and Reporting | Continuously monitor farm conditions and report suspected ILT cases to veterinarians or authorities. |
| 7 | Education and Training | Provide training for farm workers on ILT prevention and control. |
| 8 | Review and Adaptation | Continuously evaluate and adapt prevention strategies to ensure effectiveness. |
