Gapeworm head. Coloured scanning electron micrograph of the head of a female gapeworm (Syngamus trachea) from an owl. Gapeworms are parasitic nematode worms that infect the trachea (windpipe) of certain birds. The resulting disease, known as gape, occurs when the worms clog and obstruct the airway. Magnification: x150, when printed 10 centimetres wide.