Canine parvovirus (CPV), a new virus of the Canidae first appeared during the 1970s, but disease caused by this virus was not reported until 1978. Then within a few months the virus crossed national and continental boundaries causing high fatality in domestic dog populations. A similar pattern of transmission was seen in sylvatic canines but infection was largely subclinical. Between 1979 and 1981 CPV was replaced worldwide by an antigenic variant designated CPV-2a. The epidemiological advantage of this variant over CPV is not understood. CPV is a new pathogen of dogs that has attracted an...