Clinical Signs and Lesions associated with Avian Metapneumovirus Infection

Chickens and turkeys of all ages are susceptible to infection with Avian Metapneumovirus (aMPV) but clinical signs may vary.

Respiratory signs are the most conspicuous and are usually seen first after infection, particularly in younger birds. In chickens aMPV infection could go unnoticed as no clinical signs may be seen. However, the tropism of the virus for the oviduct in birds in production is often more important.

Clinical signs in turkeys and chickens

The following may be seen:

  • Young chickens and turkey poults are depressed and huddle under the heat source.
  • Respiratory signs – gasping, coughing, tracheal rales and frothy ocular or nasal discharge, especially in young turkeys.
  • Birds in lay have a marked drop in egg production and produce more poor quality eggs.
  • Affected flocks appear to be very quiet.
  • The external and internal quality of the eggs may be affected, resulting in misshapen or soft-shelled eggs with watery content. The hatchability rate of the eggs may be affected.
  • In chickens aMPV infection can form part of the so called “Swollen Head Syndrome”, the birds appearing very quiet.


Lesions are more obvious in turkeys and are characterized as:

  • Deciliation of the trachea by 48/72 hours after infection
  • Watery to mucous exudates in the turbinates up to 9 days p.i.
  • Excess mucus in the trachea
  • Peritonitis, regression of ovary and oviduct and misshapen eggs in birds in lay
  • Fluid yolk material may be found in the abdomen of birds in production
  • Pneumonia, air-sacculitis, pericarditis and perihepatitis due to secondary infections.
  • In chickens gross lesions may also include extensive yellow gelatinous – purulent oedema in the subcutaneous tissues of the head, neck and wattles and swelling of the infraorbital sinuses.


chicken with ampv
Nasal dischage and eyelids swollen shut in a chicken infected with aMPV
clinical signs of aMPV

Signs – chickens

Images of clinical signs in chickens.

TRT in turkeys

Signs – turkeys

Images of clinical signs in turkeys.