Diagnostic Challenges in Canine Parvovirus 2c in Vaccine Failure Cases

Abstract

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.

Molecular Investigation of Canine Parvovirus-2 (CPV-2) Outbreak in Nevis Island: Analysis of the Nearly Complete Genomes of CPV-2 Strains from the Caribbean Region

“…A total of 39 (90.6%) of the 43 dogs tested CPV-2 positive by SNAP ® Parvo Test (24/43 dogs, 55.8%) and/or PCR (32/32 dogs, 100%) (Table 1), while 4 samples that were negative for CPV-2 antigen could not be tested by PCR. Fifteen of the PCR positive dogs tested negative by the SNAP ® Parvo Test (Table 1), which might be attributed to the lower sensitivities of the CPV-2 antigen tests compared to PCR/qPCR assays, even in dogs with CPV-2-like clinical signs, as reported in previous studies [2,27]. We did not observe any differences in clinical severity between dogs that tested negative and positive to the SNAP ® Parvo Test.…”

The Changes in Canine Parvovirus Variants over the Years

“…Due to the rapid evolution of CPV-2 and the continuous emergence of new variants, some immunized dogs still develop the disease [ 12 , 13 , 14 , 15 ]. Overall, understanding the molecular biological characteristics and epidemic status of CPV-2 is of great significance for the prevention and control of parvovirus disease.…”

Untitled

“…As novas mutações genotípicas do vírus da parvovirose (CPV-2a, 2b e 2c) influenciam na eficácia das vacinas há mais tempo no mercado e consequente falha na proteção dos animais vacinados contra a doença (Castro et al, 2011). Um estudo revelou que a maioria dos animais vacinados (85,71%) infectada pela CPV-2c, sendo a cepa predominante entre animais vacinados e não vacinados com parvovírus (Yip et al, 2020). No nosso estudo, apenas 37 animais tinham informações sobre a origem e tipo de imunizante, contabilizando 37,8% (14/37) da nacional e 21,6% (8/37) da importada, mas não foi possível realizar a análise de qual cepa foi a infectante nos participantes.…”