First detection and molecular identification of a pathogenic spotted fever group Rickettsia, R. massiliae, from Rhipicephalus haemaphysaloides ticks infesting dogs in southern Taiwan.

Tick-borne Rickettsia pathogens become an emerging zoonotic infection worldwide. The prevalence and genetic identity of Rickettsia infection was determined firstly in Rhipicephalus haemaphysaloides ticks collected from dogs in southern Taiwan. A total of 141 Rh. haemaphysaloides ticks were examined for Rickettsia infection by nested-PCR assay targeting the citrate synthase (gltA) and outer membrane protein B (ompB) genes of Rickettsia. The Rickettsia infection was detected with a general infection rate of 2.84%, and was detected in male and female ticks with an infection rate of 3.13% and 2.60%, respectively. Genetic relationships were analyzed by comparing the gltA and ompB sequences obtained from 4 Taiwan strains and 15 other strains representing 13 genospecies of Rickettsia. Phylogenetic analyses reveal that all Taiwan strains were genetically affiliated with the R. massiliae (spotted fever group) and can be distinguished from other genospecies of Rickettsia. These results demonstrate the epidemiological significance of a human pathogenic Rickettsia species (R. massiliae) detected in Rh. haemaphysaloides ticks. Further study focused on the vector competence of this tick species may help to illustrate the potential threat for human infection in southern Taiwan.