Morphological and Molecular Identification of Brown Dog Ticks Rhipicephalus linnaei “Tropical Lineage” Isolated From Pet Dogs in Some Small Animal Hospitals Around Hanoi, Vietnam

Background: The brown dog ticks, Rhipicephalus sanguineus complex, are distributed worldwide. According to the molecular data and geographical distribution, the R. sanguineus complex is divided into two clades: R. sanguineus sensu lato “tropical lineage” and R. sanguineus sensu stricto “temperate lineage.” However, the recent morphological and molecular identification data re-established a new neotype, R. linnaei, that shares similar morphological characteristics to R. sanguineus, leading to misidentification. Objectives: This study aims to identify and confirm that Rhipicephalus dog tick species are prevalent in Vietnam. Methods: Adult ticks were collected from pet dogs in small animal hospitals around Hanoi, Vietnam. They were then identified based on morphological characteristics and molecular analysis, such as PCR and sequencing techniques. Results: The species of Rhipicephalus identified in this study was R. linnaei with typical morphological characteristics, including narrowly elongated comma-shaped spiracular in males and broadly U-shape genital pore atrium in females. The phylogenetic analysis indicated that this isolate was closely related to R. linnaei from Angola, and the genetic divergences between this isolate in this study with R. linnaei Angola strain were 0.24%, 0.5%, and 0.0% for cox1, 12S rDNA, and 16S rDNA genes, respectively. Conclusion: This is the first report on the prevalence of R. linnaei in dogs in Vietnam and the genetic variation of this species within the referenced R. sanguineus complex in Vietnam, providing essential data for tick taxonomy.