Abstract
Tick-borne rickettsioses are world-spreading infectious zoonoses. Ticks serve as reservoirs and vectors for Rickettsia and play a key role in transmission of rickettsioses. Most of the Chinese rickettsiosis patients are reported from Northeastern China but the distribution of tick and tick-borne Rickettsia species in Northeastern China remain poorly studied. In this study, a total of 1,286 ticks were captured from the seven counties of Harbin, an area in Northeastern China, and the tick-borne Rickettsia species were identified by PCR and sequencing of rrs, gltA, groEL, ompA and 17-kDa antigen-encoding genes. Of the 5 identified tick species, Haemaphysalis longicornis and Ixodes persulcatus were the predominant tick species in the livestock and vegetation, respectively. Rickettsia raoultii and “Candidatus Rickettsia tarasevichiae” were the two detectable Rickettsia species in the ticks with a 28.8% positive rate but no rickettsiae were found in ticks of Haemaphysalis concinna. R. raoultii detected in 37.6% of the Dermacentor nuttalli, Dermacentor silvarum and H. longicornis ticks while “Ca. R. tarasevichiae” was only present in 22.8% of the I. persulcatus ticks. In particular, the positive rate of both R. raoultii and “Ca. R. tarasevichiae” in ticks from the livestock (40.7%) was significantly higher than that from the vegetation (19.5%). The results indicate that the tick and tick-borne Rickettsia species are diverse in different regions of Harbin due to geographic difference and the ticks from livestock may play a more important role in transmission of rickettsioses to human.
Highlights
Rickettsiae are a large group of Gram-negative obligate intracellular prokaryotic microbes that can cause rickettsioses in human and many animals [1]
The disease has been prevailing in Northeastern China but the distribution of tick and tick-borne Rickettsia species from different areas of Northeastern China remain poorly studied
We collected a total of 1,286 ticks in the seven counties with different geographic environments of Harbin, an area of Northeastern China, and all the ticks were classified as Dermacentor nuttalli, Dermacentor silvarum, Haemaphysalis concinna, Haemaphysalis longicornis or Ixodes
Summary
Rickettsiae are a large group of Gram-negative obligate intracellular prokaryotic microbes that can cause rickettsioses in human and many animals [1]. These microbes are widely distributed throughout the world, and maintained and transmitted by arthropods such as ticks, fleas, mites and lice [2]. In the recent years, novel Rickettsia species that cause human diseases have been continuously reported, such as R. monacensis in Europe and South Korea [4, 5], and R. sibirica subsp. Headache, nausea, anorexia, rash and occasional eschar at the tick biting sites are common clinical manifestations of rickettsioses caused by most rickettsiae [10, 11]. More specific and accurate laboratory diagnostic methods, for example, PCR and sequencing and genetic analysis, have been widely employed to diagnose human rickettsiosis in clinic [9]
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