Although classified as low pathogenic, H9N2 has adapted well and often causes chronic respiratory disorders.

The rainy season is always a challenging phase for the national poultry industry. On one hand, cooler temperatures are often considered beneficial for poultry performance. However, on the other hand, increased humidity, declining air quality inside poultry houses, and management dynamics that are not always optimal can create opportunities for various diseases to emerge, particularly respiratory diseases. One that has recently come back into the spotlight is Avian Influenza (AI) subtype H9N2.

To explore this topic further, the Poultry Indonesia team interviewed drh. Akbar Ramandito, Research Farm Supervisor at PT Charoen Pokphand Indonesia Tbk, in a written response received on Wednesday (28/1). On that occasion, he explained that Avian Influenza is an infectious disease in poultry caused by the Influenza A virus from the Orthomyxoviridae family.

“This virus has a key characteristic: an eight-segmented RNA genome, which makes it highly dynamic genetically. With a segmented genome, the AI virus has a high ability to mutate and adapt. This is what makes AI, including H9N2, quite difficult to control,” the source explained.

Based on its pathogenicity classification, H9N2 falls into the Low Pathogenic Avian Influenza (LPAI) group. However, the term “low pathogenic” often leads to misunderstanding in the field. Many farmers assume the virus is harmless because it rarely causes high mortality. In fact, based on various scientific publications and field experience, the economic impact of H9N2 outbreaks can be significant due to declining production performance.

Field cases show that H9N2 has demonstrated very good adaptation in commercial poultry, particularly broiler and layer chickens. The virus replicates efficiently in the upper respiratory tract, causing damage to the respiratory epithelium and reducing local immunity. Once immunity declines, the door for secondary pathogen infections becomes wide open.

“In the field, H9N2 almost never appears alone. The cases we encounter are usually combined with E. coli, Mycoplasma gallisepticum, and Infectious Bronchitis (IB). This combination of infections is quite difficult to control if the handling is only partial,” Akbar explained.

In broiler chickens, the infection affects growth and worsens feed conversion ratio (FCR). Meanwhile, in layer chickens, H9N2 often causes a gradual decline in egg production, accompanied by poorer shell quality and an increase in abnormal eggs. Mortality is generally relatively low, but the long-term economic impact can be significant and is often not immediately recognized by farmers.

Vigilance During the Rainy Season

The increase in Avian Influenza (AI) cases during the rainy season is not a coincidence. Scientifically, viruses tend to have better stability at relatively low temperatures with high humidity levels. Environmental conditions typical of the rainy season in Indonesia—high rainfall, limited air circulation, and litter that easily becomes wet—provide an ideal environment for the virus to survive.

This article is an excerpt from the Health section of Poultry Indonesia magazine, March 2026 edition. Read the full article in Poultry Indonesia Magazine – March 2026 Edition. For subscriptions or further information, contact: https://wa.me/+6287780120754 or sirkulasipoultry@gmail.com.

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