Molecular Characteristics of Rickettsia in Ticks Collected Along the Southern Border of Mongolia

Abstract Introduction: Tick-borne infectious dDermacentor and iseases represent a significant threat to public health, particularly in regions where individuals frequently enter tick habitats. This is especially true in Mongolia, where 26% of the population are pastoral herders whose lifestyle results in high risk of tick-borne diseases, which include Rickettsial diseases. In this study, ticks collected along Mongolia’s southern border were tested for the presence of Rickettsia spp. DNA to better understand the risk of this bacterial infection in the region. Methods: Dermacentor and Hyalomma ticks (n = 4,022) collected across southern Mongolia (aimags Bayankhongor, Dornogovi, Govi-Altai, Khovd, and Omnogovi) were pooled and tested for Rickettsia spp. by real-time PCR. Subsequent melt-curve analyses and Sanger sequencing were used to identify specific Rickettsia species. Results: Approximately 64% of the 786 tick pools tested positive for Rickettsia bacteria. Melt curve analyses identified between four and six different Rickettsia species circulating in these tick pools. Amplicon sequencing of the ompA gene from selected positive samples identified Rickettsia spp. that closely resembled R. raoultii and R. sibirica. Detection rates varied greatly by sampling region and tick genus. Dermacentor ticks from the Govi-Altai region had the highest maximum likelihood estimation (MLE) infection rate of 48.4% (95% CI: 41.7-56.5%) while Hyalomma ticks collected in Omnogovi had an MLE rate of 7.6% (95% CI: 6.2-9.2%). Conclusions: Multiple Rickettsia species were found to circulate at high rates within native tick species in southern Mongolia. Further studies are required to investigate the clinical burden of disease associated with these Rickettsia spp. in exposed Mongolian populations.