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United Kingdom

Avian Metapneumovirus

Turkey Rhinotracheitis - TRT, Swollen Head Syndrome - SHS

Turkey with grey background


Avian metapneumovirus (aMPV) causes an acute respiratory tract infection of turkeys, but is also associated with swollen head syndrome in broilers and broiler breeders, as well as egg production losses in layers. The virus is spread horizontally from bird to bird, but can also be transferred by contaminated personnel and equipment.


  • Respiratory clinical signs: snicking, sneezing, nasal discharge, foamy conjunctivitis

  • Swollen head

  • Head shaking in older birds

  • Drop in egg production

  • Morbidity is high (up to 100%), mortality varies, depending on secondary infections

Post mortem lesions vary depending on the severity of the infection. Obtaining samples from the upper respiratory tract of birds in the early stages of the disease is extremely important, as once clinical signs are obvious, the isolation of replicating aMPV may not be successful. The most suitable samples for aMPV detection are tracheal and choanal swabs. A number of commercial ELISA kits are available and are commonly used, but other techniques, including virus neutralization and indirect immunofluorescence tests, as well as PCR and RT-PCR have also been used.

Currently there is no treatment for aMPV infections. Antibiotics are used to treat the secondary infections.

Good farm management techniques can significantly reduce the severity of infection. This includes: optimal ventilation, stocking densities, temperature control, litter quality and strict biosecurity. Both live and inactivated vaccines are available for immunization of chickens and turkeys and are widely used around the world. Short living birds will only be vaccinated with live vaccines and long lived birds are advised to be primed with live and boosted with inactivated vaccines.