Respiratory Disease in Broiler Production: Why the Risk Extends to Breeder Flocks

Respiratory disease remains one of the most common health challenges in modern broiler production. Coughing, nasal discharge, reduced growth rate, and secondary bacterial infections are frequently observed in affected flocks. In many cases, infectious bronchitis (IB) or Newcastle disease is initially suspected.

However, another viral agent continues to circulate in poultry populations and deserves closer attention: Avian Metapneumovirus (aMPV).

Although aMPV is commonly associated with swollen head syndrome and upper respiratory disease, its impact may extend beyond broiler flocks. When infection occurs in breeder operations, the consequences may include disruptions to egg production, egg quality, and hatchability.

This article draws on academic insights and field investigations by Dr. Niwat Chansiripornchai, Faculty of Veterinary Science, Chulalongkorn University, whose research has examined respiratory viral infections in commercial poultry systems.

aMPV in Broiler Flocks

Avian Metapneumovirus primarily infects the upper respiratory tract of poultry. The virus attaches to the ciliated epithelial cells lining the respiratory tract, disrupting normal ciliary movement — a process known as ciliostasis. These cilia normally help remove pathogens and debris from the respiratory system.

When this natural defense mechanism is impaired, birds become more susceptible to secondary infections caused by bacteria or other respiratory pathogens.

Clinical signs in broilers may include:

• Coughing and sneezing

• Nasal discharge

• Respiratory sounds

• Increased susceptibility to bacterial complications

  
  

Mortality is generally low unless secondary infections occur. However, respiratory damage can contribute to processing losses, particularly when airsacculitis develops in birds affected by multiple pathogens.

Greater Impact in Breeder Flocks

The consequences of aMPV infection can be more significant in breeder and layer flocks.

Field observations in commercial poultry systems indicate that susceptible breeder flocks may experience production disturbances following infection. According to investigations led by Dr. Niwat and colleagues, affected flocks have shown:

• Egg production drops exceeding 20%

• Reduced eggshell strength and shell quality

• Decreased hatchability

• Slower recovery of egg production

  
  

In some cases, swollen head syndrome and severe upper respiratory inflammation are observed, particularly when secondary bacterial infections are involved.

Because breeder flocks must maintain stable egg production over a long laying cycle, respiratory disease can affect productivity for an extended period.

Evidence of Field Exposure

Serological evidence suggests that aMPV continues to circulate in commercial poultry populations.

In field investigations, flocks without prior vaccination have shown positive antibody responses, indicating natural exposure under commercial production conditions. These findings highlight that the virus may be present within poultry production systems even when clinical signs are not always obvious.

Field observations indicate that egg production decline and eggshell quality problems may coincide with evidence of infection, emphasizing the importance of monitoring respiratory health in breeder flocks.

The Role of Secondary Infections

A key feature of aMPV infection is its interaction with other pathogens.

Because the virus damages the cilia lining the respiratory tract, birds become more vulnerable to secondary infections such as Mycoplasma, E. coli, or infectious bronchitis virus. According to investigations led by Dr. Niwat, co-infections are frequently observed in affected flocks.

In breeders, these combined infections may intensify respiratory inflammation and contribute to swollen head syndrome, which can prolong recovery and worsen production losses.

This highlights an important point for poultry management: respiratory disease problems often involve multiple pathogens rather than a single infection.

Vaccination and Prevention

Vaccination remains an important tool to reduce the impact of aMPV in poultry production.

Live vaccines derived from subtype A or B strains may be administered early in life, including at day-old age. In breeder programs, inactivated vaccines are often used before the onset of lay — typically between 16 and 20 weeks — to strengthen immunity during the production period.

Serological monitoring can help evaluate flock exposure and vaccination response. Combined with strong biosecurity and proper health management, vaccination programs can help reduce the severity of production losses associated with respiratory infections.

Strengthening Disease Prevention in Breeder Operations

Respiratory viruses such as aMPV can influence both flock health and production performance. In breeder flocks, infection may affect egg production, shell quality, and hatchability.

Field observations and serological evidence suggest that understanding viral circulation, implementing appropriate vaccination strategies, and maintaining strong biosecurity are essential for protecting flock performance.

Dr. Niwat Chansiripornchai will further explore vaccination strategies and disease prevention approaches in broiler breeder operations during the upcoming Broiler Breeder Management Course organized by Progressus, where participants will gain practical insights into designing effective health programs to protect breeder productivity.