New Data on Ixodid Ticks and Their Infection with Borrelia and Coxiella burnetii in Vietnam.

The distribution of medically significant ticks in Vietnam requires ongoing monitoring. This study presents data on tick distribution and molecular screening for Borrelia spp. and Coxiella burnetii DNA. Ticks were collected from domestic animals and vegetation in four provinces over the period of 2024-2025. Species identification was performed based on morphology and confirmed by sequencing mitochondrial COI and 16S rRNA genes. A total of 2347 ticks were collected, representing eight species from the genera Haemaphysalis, Rhipicephalus, and Amblyomma. The study provides new distribution records for H. bispinosa, H. cornigera, A. integrum, and several rarely reported species (H. lagrangei, H. hystricus, and H. wellingtoni). PCR screening revealed a relatively high detection rate of Borrelia DNA in H. cornigera from Cao Bang province. Sequencing identified the pathogen as B. theileri, the agent of bovine borreliosis. Borrelia theileri was also detected in R. microplus in other regions, indicating wider circulation. PCR screening for Coxiella burnetii was positive for 13 ticks from cattle in Cao Bang province. To rule out false-positive results due to detection of DNA from Coxiella-like endosymbionts, we sequenced a fragment of the IS1111 element for three positive samples. The sequences confirmed that the DNA belongs to bacteria of the genus Coxiella, but the data do not allow confident assignment to C. burnetii at the species level. These positive ticks originated from eight neighboring households, suggesting a potential localized focus that requires further assessment in livestock and humans to determine the epidemiological significance. This research enhances the understanding of Vietnam's tick fauna and associated pathogens of medical and veterinary importance.