Molecular detection of Rickettsia felis in ticks and fleas from the environment in Hanoi and Phu Tho province, Vietnam

Abstract

Introduction: Surveillance for Rickettsia spp. is necessary given the recent emergence and re-emergence of various rickettsioses in Vietnam. However, data on their circulation in off-host arthropods from natural environments remain limited. This study aimed to investigate the presence and distribution of Rickettsia species in ticks and fleas collected from the environment in Hanoi and Phu Tho provinces, northern Vietnam, between September and December 2021.

Methodology: The ticks and fleas were collected using dragging, light traps, and carbon dioxide traps. Arthropods were identified morphologically and screened for Rickettsia species using real-time PCR targeting the 17kDa antigen gene. Positive samples were further analyzed using species-specific real-time PCR assays and multilocus sequence typing (MLST) for confirmation and phylogenetic analysis.

Results: A total of 758 arthropods were collected, including 748 ticks (747 larval ticks grouped into 101 pools and 1 adult tick) and 10 fleas. The minimum field infection rate (MFIR) of Rickettsia spp. in ticks was 2.94% (22/748), while the prevalence in fleas was 50% (5/10). Rickettsia felis was detected in 9 larval tick pools and 2 individual fleas by species-specific real-time PCR and MLST. No other Rickettsia species were identified.

Conclusions: This study provides the first evidence of Rickettsia spp. in off-host ticks and fleas from the natural environment in Vietnam. These findings indicate a potential risk of environmental exposure to Rickettsia and emphasize the need for integrated vector surveillance strategies.