Molecular epidemiology and emerging genotypes of canine distemper virus in Istanbul, Türkiye.

Abstract

BACKGROUND: Canine distemper virus (CDV) is a highly contagious, globally distributed pathogen that remains a serious concern even with available vaccines. In T&#xfc;rkiye, reports of CDV outbreaks among vaccinated dogs suggest the emergence of genetically divergent strains. This study investigated CDV prevalence, clinical correlations, molecular characteristics, and phylogenetic relationships in Istanbul, T&#xfc;rkiye, using rectal swabs from 202 clinically ill dogs (2018&#x2013;2023). RESULTS: Results revealed a 27.2% infection rate (55/202), with significantly higher prevalence in puppies (<&#x2009;6 months;&#x2009;<&#x2009;0.05). Clinical signs (fever, seizures, gastrointestinal distress) and hematological alterations (elevated neutrophils, reduced RBC counts) were strongly associated with infection (&#x2009;<&#x2009;0.05). Phylogenetic analysis of the hemagglutinin (H) gene revealed three circulating genotypes: Arctic-like (72%), Asia 1 (24%), and Europe (4%). Arctic-like strains clustered with Turkish and European variants, while Asia 1 strains closely matched Chinese lineages suggesting multiple introduction routes. Notably, amino acid substitutions in antigenic regions and glycosylation sites were identified, that may facilitate immune evasion, particularly concerning given T&#xfc;rkiye&#x2019;s complex dog population dynamics. CONCLUSION: Our findings indicate the Arctic-like CDV lineage now dominates in Istanbul&#x2019;s canine population. This study provides valuable insights into the epidemiology and genetic diversity of circulating CDV genotypes in T&#xfc;rkiye and its implications for vaccine efficacy. Continuous surveillance is critical to monitor emerging strains and optimize control strategies. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12917-025-04963-x.