A Canine Parvovirus Type 2 Vaccine Protects Dogs Following Challenge with a Recent Type 2C Strain
Since the emergence of canine parvovirus type 2 (CPV2) in the 1970s, the virus has been evolving. The first variant which appeared was called type 2a, subsequently a second variant appeared and was called type 2b. The original type 2 virus now appears to have been replaced in the field by the type 2a and 2b variants. There is evidence that this evolution is continuing and reports of the emergence of a new variant - type 2c - have appeared over the last few years. The initial canine strain vaccines were based on the original type 2 virus. Concern has already been expressed as to whether these vaccines protect as effectively against the 2a and 2b variants, and the more recent appearance of CPV type 2c has again raised this question. One of the original live attenuated vaccines which are still widely used today was based on a type 2 field strain isolated in the UK (Nobivac® Parvo-C - Intervet). This vaccine has already been shown to protect dogs from both clinical disease and virus shedding following challenge with CPV type 2, 2a and 2b. The following study was set up to investigate whether this type 2 vaccine could also successfully protect against challenge with a field isolate of the new type 2c variant. Twelve seronegative beagle dogs were divided into two equal groups. One group was vaccinated with Nobivac Pi and Nobivac Lepto at 8-10 weeks of age and Nobivac DHPPi and Nobivac Lepto three weeks later. The control group received no vaccinations. Four weeks following the second vaccination both groups of dogs were challenged with a recent field isolate of canine parvovirus type 2c. Blood samples, in order to monitor antibody response and leucocyte numbers, and rectal swabs, in order to detect any viral excretion post challenge, were taken at various intervals. Dogs were also clinically monitored from two days prior, to 14 days post challenge. In the unvaccinated control group all the dogs became severely ill. Three of the six control dogs had to be euthanised and although the three remaining control dogs survived they required supportive oral administration of electrolytes. In addition all of the unvaccinated control dogs shed parvovirus in their faeces for at least four days post challenge. In contrast all the vaccinated dogs remained clinically normal throughout the course of the study and no virus could be isolated from rectal swabs at any stage post challenge. This study demonstrates that a single dose of the Nobivac CPV vaccine is able to successfully protect against clinical signs of disease and prevent shedding of virus, following challenge with the recent type 2c variant of canine parvovirus.