Study On The Cross Prevention Of Meals Live Attenuated Vaccine For Young Dogs Against Canine Distemper

Canine distemper virus (CDV) and meals virus (MV) vaccine strain were respectively isolated from the 5-combined canine and meals attenuated vaccine with the Vero cell line. They multiplied as highly as 104.5 and 104.76TCID50/0.1ml on the cell line. 14 young dogs at different ages and their mother were used for measuring the maternal neutralizing antibody to CDV. The results showed that when the titer of mother-dog's neutralizing antibody was 1:75, the average titers of maternal antibody were 1∶14, 1∶27, 1∶46 and 1∶2 5 at the age of 2, 9, 16 and 23 days, respectively. At the age of 23 days, the young dogs were divided into 3 groups,Ⅰ,ⅡandⅢ. Three groups were inoculated with 104.5 TCID50 CDV vaccine, 104.76 TCID50 MV vaccine and Vero cell culture, respectively. The maternal antibodies of dogs at 7 and 14 days after inoculation with CDV vaccine were 1∶6 and 1∶5, respectively. But maternal antibodies of dogs inoculated with MV vaccine and vero cell culture did not decline significantly. The assay of leukocyte migration inhibition proved that dogs inoculated with MV vaccine had high-level cell immunity. Then dogs were challenged with CDV vaccine, MV vaccine and vero cell culture. The results showed that disease incidence of dogs challenged with CDV vaccine was 80% (4/5), and disease incidences of dogs challenged with MV vaccine and vero cell culture were much lower. When maternal antibody of young dog was 1∶20, the maternal antibody could be blocked by CDV vaccine, MV vaccine neither neutralized maternal antibody of young dogs nor was disturbed by maternal antibody. It supplied immunity protection against CD for young dogs. This research provided a theoretical basis for acquiring the cross protection against CD by the clinical application of MV vaccine inoculating young dogs.