Attaches the virus to cell receptors and thereby initiating infection. Binding of H protein to the receptor induces a conformational change that allows the F protein to trigger virion/cell membranes fusion. The cellular receptor might be SLAM, and may explain the lymphotropism of the virus. Binds canine SLAMF1 at the cell surface. Belongs to the paramyxoviruses hemagglutinin-neuraminidase family. Non-sialidase subfamily. Morbiliviruses hemagglutinins have no neuraminidase activity.