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

Michael E Von Fricken,Kathryn M Hogan,Randal J Schoepp,Matthew A Voorhees,Carmen Asbun,Jeffrey W Koehler,Brandon Lam,Barbara Qurollo,Battsetseg Jigjav,Uyanga Baasandagva

doi:10.3390/pathogens9110943

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 Hyalomma asiaticum 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.

Highlights

Rickettsial infections are on the rise globally and pose an emerging threat to human health [1,2,3].Transmission and infection occur after arthropods such as ticks and fleas suck blood from a host, causing mild to fatal illnesses characterized by non-specific fever, myalgia nausea, and rash [4]
The highest Rickettsia spp. pool detection rate was observed in Govi-Altai at 95% (195/204)
Maximum likelihood estimates (MLE) found Rickettsia spp. present at an average prevalence of 33.2% in Dermacentor ticks, and 7.4% Hyalomma ticks collected along the southern border (Figure 1)

Summary

Introduction

Rickettsial infections are on the rise globally and pose an emerging threat to human health [1,2,3].Transmission and infection occur after arthropods such as ticks and fleas suck blood from a host, causing mild to fatal illnesses (ex. spotted fevers and typhus) characterized by non-specific fever, myalgia nausea, and rash [4]. Rickettsial infections are on the rise globally and pose an emerging threat to human health [1,2,3]. Transmission and infection occur after arthropods such as ticks and fleas suck blood from a host, causing mild to fatal illnesses Spotted fever group (SFG) rickettsial organisms are gram-negative obligate intracellular coccoid-shaped bacteria that can infect a variety of mammalian species, including livestock and humans. Tick-borne SFG Rickettsia are distinguished from the Rickettsia typhus group (TG) by vector, clinical presentation, and the presence of the outer membrane protein ompA, which is absent in the TG Rickettsia [5]. The epizootiology of Rickettsia spp. is further complicated by transovarial and transstadial transmission within the vector tick species [6].

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Results

Discussion

Conclusion