Canine parvovirus type 2 antigenic variants and in-hospital mortality in central Spain: Retrospective and prospective data (2003-2014).

Background: Canine parvovirus type 2 (CPV-2) remains a major cause of morbidity and mortality in young dogs. Clinical and molecular data obtained between 2003 and 2014 from a veterinary teaching hospital in central Spain were analyzed to characterize circulating CPV-2 antigenic variants and associated in-hospital outcomes. As the samples were collected more than a decade ago, the reported frequencies represent historical CPV-2 data rather than the current circulation. Aim: This study aimed to describe the historical distribution of CPV-2 antigenic variants (2a, 2b, and 2c) detected in hospital-presenting clinical samples collected between 2003 and 2014, document rare detections of feline panleukopenia virus (FPV) and the Cornell vaccine strain, and analyze clinical variables associated with in-hospital mortality. Methods: A retrospective series of 110 clinical samples were analysed using rapid antigen tests and polymerase chain reaction. Adequate amplification yielded 583-bp VP2 fragments, of which 50 were selected for sequencing (42 produced high-quality reads). Species identification (CPV-2 vs. FPV) was based on full-length amplicon alignment and phylogenetic clustering. Amino acid residue 426 was used as a supporting marker to distinguish the CPV-2a, CPV-2b, and CPV-2c antigenic variants. Logistic regression models estimated odds ratios (OR) with 95% confidence intervals (CI). Results: In the sequenced archival cases, CPV-2c was the predominant variant (42.9%, 18/42), followed by CPV-2a (31.0%, 13/42), the Cornell vaccine strain (11.9%, 5/42), CPV-2b (9.5%, 4/42), and FPV (4.8%, 2/42). Small-breed dogs (<15 kg) exhibited higher odds of in-hospital death (OR = 2.74; 95% CI = 1.18-6.37). Dogs presenting with gastrointestinal signs in combination with neurological and/or respiratory signs had markedly increased odds of mortality (OR = 9.14; 95% CI = 2.29-36.40). No statistically significant associations were observed between mortality and antigenic variant or vaccination status. Conclusion: This archival cohort provides a historical reference for CPV epidemiology in central Spain. CPV-2c was the most common variant. Breed size and multisystemic involvement were significantly associated with in-hospital mortality. However, contemporary sequencing would be necessary to monitor the evolution of CPV-2 beyond the study period due to the historical nature of the study.