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 (By similarity). Binds canine SLAMF1 at the cell surface. Belongs to the paramyxoviruses hemagglutinin-neuraminidase family. Non-sialidase subfamily. Morbiliviruses hemagglutinins have no neuraminidase activity.