Viral infections in poultry remain a significant challenge in maintaining the health and productivity of chicken farms in Indonesia. One disease that requires attention is Swollen Head Syndrome (SHS) is a respiratory disease caused by Avian Metapneumovirus (aMPV) (Zhang et al. 2025). A single-stranded RNA virus belonging to the Pneumoviridae family. It is currently classified into four main subtypes, namely aMPV-A, aMPV-B, aMPV-C, and aMPV-D (Hatfield et al., 2026). The presence of this infection has been reported in Indonesia and can attack various types of poultry at different ages (Sutrisno et al. 2013).
Based on Technical Education data and According to Consultation Medion (2026), SHS cases in layers can be found across various age groups, with a higher proportion of cases occurring in chickens aged 11-55 weeks. In 2025, the highest proportion of cases was recorded in chickens aged 27-55 weeks at approximately 28%, followed by chickens aged 11-17 weeks at 26% and chickens aged 18-26 weeks at 23%. Meanwhile, in 2026, the 27-55 week age group continued to show the highest proportion, at approximately 28%, followed by chickens aged 11-17 weeks at 24%.
The data indicates that SHS requires special attention, especially in chickens entering the final growth phase and into production. Incidents at younger ages also warrant vigilance, as the proportion of cases in chickens aged 6-10 weeks is projected to increase to around 20% by 2026, compared to around 14% in 2025.
Clinical Symptoms
The virus primarily attacks the respiratory system. Manifestations can include sinusitis, head swelling (intramandibular, intracutaneous, and intrasynovial), increased mortality, and decreased egg production (Nakamura et al. 1997). Chickens can exhibit snoring, sneezing, weakness, conjunctivitis, and even difficulty breathing.
Swollen Head Syndrome (SHS) requires vigilance because its early symptoms can resemble other respiratory illnesses. This condition often leads to viral infections being overlooked or even mistaken for bacterial infections, especially Infectious Coryza causes swelling throughout the head area (Al-Hasan et al. 2022).
Clinical conditions can become more severe if aMPV is co-infected with other agents, especially bacteria, such as coryza. chronic respiratory disease, colibacillosis, mycotoxicosis, infectious laryngotracheitis (ILT), and others. These co-infections can worsen the manifestations of the disease and complicate treatment in the field (Couto et al. 2016; Medion, 2026).
Confirmation of Diagnosis
Observations of chicken condition, disease history, changes in production performance, and pathological examinations can be used to guide initial suspicion. Laboratory testing is essential for confirming the presence of aMPV. One method that can be used is real-time RT-PCR to detect viral genetic material and help identify the aMPV subtype (Saeed et al. 2026).
The examination was carried out. The examination target was directed at a specific gene against the G gene in aMPV-A and aMPV-B. While the SH gene for aMPV-C (Zhang et al. 2025). Serological tests such as ELISA can also be used to detect antibodies to aMPV. Virus isolation can be performed, but aMPV is known to be quite difficult to isolate because the viral shedding period after infection is relatively limited and the virus is unstable in diagnostic specimens (Goraichuk et al. 2024). Not only through molecular methods, but the ineffective use of antibiotics in treatment also points to a non-bacterial source of infection.
Case Findings Swollen Head Syndrome
One example of a case found in a cage open house densely populated area of layer chickens in East Java. The cages are shaped like open house with a population of 7.000 chickens of age grower 10 weeks. In the affected flock, chickens were found to have respiratory problems, facial swelling, lethargy, anorexia, and elevated body temperature. Measurements showed the chickens' body temperature reached approximately 42,5°C.
Meanwhile, diarrhea was not found in any of the observed chickens. Similar symptoms were also identified in several flocks, indicating a health issue requiring further attention. Necropsies revealed a cheesy mass and mucus in the trachea, causing respiratory obstruction. Infected chickens would lift their heads to try to breathe. A yellowish mass was found in the upper respiratory muscle, indicating a viral infection.
Handling and Prevention
Vaccination is an important component in controlling aMPV. Experience in controlling aMPV in various regions shows that vaccination can play a role in reducing disease and economic losses (Anil et al. 2026). In vaccination programs, live vaccines can be used to prime the immune response, followed by inactivated vaccines as boosters, depending on the program and the farm's needs (Jin Kim et al. 2025).
Vaccination programs cannot be designed uniformly for all farms. Vaccine selection and timing must consider the type of bird, age, flock health, risk level, disease history, circulating virus subtypes, and recommendations from the vaccine manufacturer and veterinarian. Therefore, vaccination is mandatory for areas or farms with a history of infection or those that have previously received SHS vaccination. It is recommended to allow a four- to eight-week interval between two live aMPV vaccinations (MSD Animal Health, 2026).
Repeat vaccinations following previous failed vaccinations can be done with economic considerations, as field infections can potentially lead to death in populations with weakened immune systems.
Author: Azhar Burhanuddin (Student of Wave III of Veterinary Professional Education)
Reference
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