Cross-Neutralization of Vanguard C4 Vaccine Against Australian Isolates of Canine Parvovirus Variants CPV-2a, CPV-2b, and CPV-2c.

Canine parvovirus type 2 (CPV-2) remains one of the most significant viral pathogens in dogs in Australia and worldwide despite the availability of safe and effective CPV vaccines. At least three different variants of CPV-2 have emerged and spread all around the world, namely CPV-2a, CPV-2b, and CPV-2c. The ability of the current vaccines containing either original CPV-2 type or CPV-2b variant to cross protect the heterologous variants has been well demonstrated in laboratory studies, despite some concerns regarding the vaccine efficacy against the emerging variants. Vanguard®, a series of multivalent vaccines, has been in the market for a considerable period of time and demonstrated to provide efficacy against all three types of CPV variants CPV-2a, CPV-2b, and CPV-2c. The purpose of this study was to evaluate the ability of the recently registered Vanguard C4 vaccine to induce cross-neutralizing antibodies against the Australian isolates of CPV-2a, CPV-2b, and CPV-2c variants. Blood samples collected from dogs vaccinated with Vanguard C4 were analyzed by virus neutralizing assays developed for each of three CPV variants. The results of the study demonstrated that Vanguard vaccine induced cross-neutralizing antibodies against the Australian isolates of CPV-2a, CPV-2b, and CPV-2c, thus offering cross protection against all three Australian CPV variants.

Diagnostic Challenges in Canine Parvovirus 2c in Vaccine Failure Cases.

In this study, three different diagnostic tests for parvovirus were compared with vaccination status and parvovirus genotype in suspected canine parvovirus cases. Faecal samples from vaccinated (N17) and unvaccinated or unknown vaccination status (N41) dogs that had clinical signs of parvovirus infection were tested using three different assays of antigen tests, conventional and quantitative PCR tests. The genotype of each sample was determined by sequencing. In addition to the suspected parvovirus samples, 21 faecal samples from apparently healthy dogs were tested in three diagnostic tests to evaluate the sensitivity and specificity of the tests. The antigen test was positive in 41.2% of vaccinated dogs and 73.2% of unvaccinated diseased dogs. Conventional PCR and qPCR were positive for canine parvovirus (CPV) in 82.4% of vaccinated dogs and 92.7% of unvaccinated dogs. CPV type-2c (CPV-2c) was detected in 82.75% of dogs (12 vaccinated and 36 unvaccinated dogs), CPV-2b was detected in 5.17% dogs (one vaccinated and two unvaccinated) and CPV-2a in 1.72% vaccinated dog. Mean Ct values in qPCR for vaccinated dogs were higher than the unvaccinated dogs (p = 0.049), suggesting that vaccinated dogs shed less virus, even in clinical forms of CPV. CPV-2c was the dominant subtype infecting dogs in both vaccinated and unvaccinated cases. Faecal antigen testing failed to identify a substantial proportion of CPV-2c infected dogs, likely due to low sensitivity. The faecal samples from apparently healthy dogs (n = 21) showed negative results in all three tests. Negative CPV faecal antigen results should be viewed with caution until they are confirmed by molecular methods.