Canine parvovirus: strain difference in haemagglutination activity and antigenicity.

Canine parvovirus (CPV) strains were compared for haemagglutination (HA) activity and antigenicity and were divided into two types by HA activity. Strains Cp49 and 29-F showed temperature-dependent HA, like feline panleukopenia virus (FPLV) and mink enteritis virus (MEV), whereas strains Sp-80 and Y-1 showed temperature-independent HA with erythrocytes from eight species of animals. The results of a cross HA inhibition test using immunized rat sera suggested that of the two types of CPV those showing temperature-dependent HA were antigenically like FPLV and MEV whereas those showing temperature-independent HA were not. This antigenic difference between the two types was confirmed by a HA inhibition test with monoclonal antibodies. A chronological survey revealed that CPV isolates from earlier years have HA activity and antigenicity similar to those of FPLV and MEV, whereas current CPV isolates do not. There are some exceptional isolates from the transitional period which have similar antigenicity to FPLV and MEV but different HA activity. These results suggest that the haemagglutinin of CPV altered from one form resembling that of FPLV to a somewhat different structure during passage in dogs in nature.