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

Abstract

Tick-borne infections are a significant threat to public health, particularly in regions where individuals frequently enter tick habitats. Roughly 26% of the population in Mongolia practice nomadic pastoralism and are considered at high risk of exposure to ticks and the diseases they carry. This study tested ticks from Mongolia’s southern border for Rickettsia spp. to better understand the epidemiology of tick-borne diseases in the region. Dermacentor nuttalli and Hyalomma asiaticum ticks (n = 4022) were pooled and tested for Rickettsia spp. by real-time PCR. Melt-curve analyses and Sanger sequencing were used to identify Rickettsia species. Approximately 64% of the 786 tick pools tested positive for Rickettsia bacteria. Melt curve analyses identified four different Rickettsia species circulating in these tick pools. Amplicon sequencing of the ompA gene identified Rickettsia spp. that closely resembled R. raoultii and R. sibirica. Dermacentor nuttalli ticks from Govi-Altai had the highest maximum likelihood estimation infection rate 48.4% (95% CI: 41.7–56.5%), while Hyalommaasiaticum collected in Omnogovi had a rate of 7.6% (95% CI: 6.2–9.2%). The high detection of Rickettsia suggests a substantial risk of infection in southern Mongolia. Further studies are necessary to investigate the clinical burden of tick-borne diseases in Mongolia.

Ehrlichia chaffeensis and Four Anaplasma Species With Veterinary and Public Health Significance Identified in Tibetan Sheep (Ovis aries) and Yaks (Bos grunniens) in Qinghai, China

“…Anaplasmosis and ehrlichiosis are important diseases caused by tick-borne pathogens, which result in additional economic losses to livestock ( 1 , 2 ). To date, seven Anaplasma species have been identified, including A. bovis, A. phagocytophilum, A. centrale, A. platys, A. marginale, A. ovis , and A. capra ( 3 , 4 ).…”

Metagenomic profiles of Dermacentor tick pathogens from across Mongolia, using next generation sequencing

“…While previous work has documented high pool positivity levels for Rickettsia spp. in Dermacentor ticks from southern and central aimags of Mongolia ( Fischer et al, 2020 ; von Fricken et al, 2020b ), this study has a much wider geographic range and represents, to our knowledge, the first time NGS methods have been applied to testing Dermacentor ticks in Mongolia. The finding of higher MLEs and pool-positivity rates in the eastern part of Mongolia may indicate a potential hotspot for Dermacentor tick-related Rickettsia spp.…”

“…Of note, the total MLE in this study (37.30%; 95% CI: 33.50–41.01) is similar to a previous work that sampled ticks from five southern aimags, where the MLE for Dermacentor spp. was 33.2% (95% CI: 30.1–36.2; von Fricken et al, 2020b ). Additionally, zero larvae and few nymphs were found across 191 geographically distinct collection events spread out through 15 aimags, which we believe is suggestive of Dermacentor ticks spending earlier life cycle stages underground in rodent burrows, given harsh dry winter seasons common in Mongolia.…”

“…Importantly, certain results of this study corroborate what has previously been reported concerning the epidemiology of tick-borne pathogens within Mongolia. This includes the high prevalence of Rickettsia spp., particularly R. raoultii , among Dermacentor ticks collected across the country ( Fischer et al, 2020 ; von Fricken et al, 2020b ). We also report the detection of A. ovis exclusively in ticks removed from livestock, which is in agreement with a previous study demonstrating higher levels of Anaplasma spp.…”

“…The potential threat tick-borne diseases present to both the Mongolian population and its growing ecotourism industry is substantial, given the high rates of various pathogens reported in previous tick survey studies ( Černý et al, 2019 ; Fischer et al, 2020 ; von Fricken et al, 2020b ). Improved molecular characterization of TBDs within Mongolia may help inform future preventative measures for locals and visitors, while also establishing baseline sequence data to monitor evolution over time.…”