Avian Pneumovirus = TRT = Dikkop (Swollen Head Syndrome)

Avian Pneumovirus = TRT = Dikkop (Swollen Head Syndrome)

Aug 7, 2013

The virus that causes Dikkop (Swollen Head Syndrome) belongs to the Pneumovirus group of respiratory viruses and should always be on the list of differential diagnoses when it comes to a “snick” in the poultry house.

In broilers, we see a unilateral or bilateral swelling of the head due to inflammation under the skin of the head. This is actually an extension of inflammation from the sinus, under the eye, to the tissues under the skin of the head. Broilers don’t usually die but do struggle to eat as the swelling can be so severe that they cannot see to eat.

Swollen heads, due to sinusitis, can also be due to poor air quality, especially dust. When a few swollen heads are seen in the house it may be due to one of these 2 things (viral or poor air quality). If the cause is viral, you will see it spread through the house with the percentage of affected birds increasing daily. If its poor air quality, then it’s seen in birds scattered throughout the house. In this case the number of birds affected does not increase rapidly.

Blood can be collected at slaughter and tested for the presence of TRT antibodies. If the presence of TRT is indicated then vaccination is recommended. This usually takes place at around 7 days of age.

In layers, TRT causes a severe unilateral to bilateral conjunctivitis and marked swelling of the eyes due to the accumulation of a firm yellow material under the eyelids (fibrin). If these masses are manually removed from behind the conjunctiva early on, the eyeball will be saved. If not, then the eyeball is damaged and the bird loses sight in that eye. TRT is also a cause of white shelled eggs in laying birds. It is important to differentiate from other causes of white eggs such as calcium deficiency, Newcastle Disease and IB viruses. Again, blood tests will show exposure to TRT. The rearing vaccination programme must then be adjusted accordingly.