Genetic Characterization of Canine morbillivirus (Canine Distemper Virus) Field Strains in Dogs, Chile, 2022-2023

Canine distemper virus (CDV) poses a significant threat to dogs and wildlife worldwide, and this study sought to provide an updated genetic characterization of CDV field strains in Chile during 2022-2023. We collected samples from 52 suspected CDV cases in domestic dogs and detected viral RNA through real-time RT-PCR in 28 dogs (54%). Factors like age and vaccination status were determinants of CDV positivity, with young adult and unvaccinated dogs facing a higher infection risk. We isolated CDV from positive samples in VeroDogSLAM cells. From these isolates and direct samples, we obtained sequences and estimated the phylogeny based on gene H. CDV isolates from nasal and conjunctival swabs exhibited cytopathic effects, and sequence analysis unveiled a substantial genetic diversity among the strains. Chilean CDV strains demonstrated a genetic distance to vaccine strains of approximately 10%, antigenic-change-related amino acid substitutions, and novel putative glycosylation sites. In the phylogeny, Chilean CDV field strains clustered into two lineages, Europe/South America-1 and North/South America-4, indicating the emergence of the North/South America-4 lineage in Chile and underscoring the genetic complexity of CDV in the country. Interestingly, certain Chilean viruses shared a close common ancestor with Brazilian and Peruvian viruses, suggesting viral spreading patterns. Further investigations are warranted to comprehend the potential antigenic implications of these genetically diverse CDV strains.