The disease is caused by a pneumovirus. Turkeys and chicken can be affected.
The virus may be transmitted horizontally by contaminated water, personnel and equipment as well as from bird to bird.
Clinical signs and lesions
In young turkeys sneezing. Rales and nasal discharge, conjunctivitis, swelling of the infraorbital and submandibular sinuses can be seen.
In laying flocks a drop in production may occur along with respiratory distress. Morbidity is high whereas mortality may vary being usually higher in young poults.
In chickens, the pneumovirus may be involved in the so called "Swollen head Syndrome" (SHS). In such cases affected chickens may show swelling of the periorbital and infraorbital sinuses, torticollis, cerebral disorientation and depression. Marked egg production losses can be associated with SHS.
At necropsy, the lesions seen may vary due to other microorganisms that may complicate the original picture. In cases of SHS, apart from oedema in the head, purulent or caseous subcutaneous exudates can also be found. Rhinitis, tracheitis and sinusitis are frequently noted in both chickens and turkeys, hence also the name turkey rhinotracheitis (TRT).
Polyserositis affecting the air sacs and pericardium may be due to secondary infections (E.coli). The kidneys may be swollen and congested as well as the lungs which may show a fibrinous exudate in the pleural cavity.
The diagnosis based only on clinical signs is difficult to establish since other agents may be involved. The most certain diagnosis may be obtained by the isolation of the organism from nasal secretions or tissue scraped from the sinus of affected birds. Antibodies can be detected by several serological methods such as the VN test, IFT and ELISA.
Treatment and control
Treatment with antibiotics can be given to control secondary bacterial infections. The use of vaccines should be the best approach to control the disease.
Point of attention:
If a breeder flock suffers from swollen head syndrome, it might be necessary to take of some grills from the female feeder tracks, to allow the birds to eat freely and avoid a drop in production.