Behind stable production figures, CRD remains a persistent threat and can lead to significant losses if biosecurity is not properly implemented.

In the modern poultry industry, there is a disease that often does not cause sudden mortality, yet gradually and consistently erodes production performance. That disease is Chronic Respiratory Disease (CRD), caused by Mycoplasma gallisepticum (MG). It is chronic, progressive, and often underestimated in its early stages. However, if not properly controlled, MG can result in economic losses, particularly in breeder and layer operations.

“I need to give a disclaimer first—I’m not a bacteriology or immunology expert. But based on what I’ve studied and observed in the field, MG is a bacterium that attacks the respiratory system of poultry, and its effects are slow but consistent,” said drh. Tiffany Asri Kusumastuti, Hatchery Epidemiologist at Bounty Segar Indonesia, during an online interview on Wednesday (Feb 11).

Biologically, Tiffany explained that MG has characteristics that distinguish it from many other bacteria. Unlike most bacteria, MG lacks a cell wall and only has a cell membrane. This absence of a cell wall makes it more flexible and able to adapt to host tissues.
“Because it doesn’t have a cell wall, it’s more flexible and can strongly attach to the ciliated epithelium in the respiratory tract, especially the trachea and air sacs,” she explained.

The ciliated epithelium functions as a natural defense mechanism in the respiratory system. The cilia help move mucus outward, allowing foreign particles and microorganisms to be cleared. When MG attaches to and damages the cilia, this mucus-clearing mechanism is disrupted. As a result, mucus accumulates and creates an ideal environment for secondary infections.

“This is why MG rarely acts alone. It is often accompanied by other bacterial infections such as E. coli, which further worsen the condition. The combination of MG and secondary infections is what we commonly refer to as CRD complex (Chronic Respiratory Disease Complex) in the field,” she added.

Mild Clinical Signs, Significant Impact

One of the biggest challenges in controlling MG is that its symptoms appear mild, yet the impact is substantial. In broilers, these signs are often mistaken for weather changes or suboptimal ventilation management.

“Usually, chickens show respiratory sounds—what we call ‘ngorok’ or ‘cetrek.’ There may be nasal discharge, and sometimes swelling of the infraorbital sinus. Although it may seem common, once there are signs of decreased performance, disease infection should be suspected,” she explained.

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

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