Spiroplasma Infection among Ixodid Ticks Exhibits Species Dependence and Suggests a Vertical Pattern of Transmission

Abstract

Members of the genus Spiroplasma are Gram-positive bacteria without cell walls. Some Spiroplasma species can cause disease in arthropods such as bees, whereas others provide their host with resistance to pathogens. Ticks also harbour Spiroplasma, but their role has not been elucidated yet. Here, the infection status and genetic diversity of Spiroplasma in ticks were investigated using samples collected from different geographic regions in Japan. A total of 712 ticks were tested for Spiroplasma infection by PCR targeting 16S rDNA, and Spiroplasma species were genetically characterized based on 16S rDNA, ITS, dnaA, and rpoB gene sequences. A total of 109 samples originating from eight tick species were positive for Spiroplasma infection, with infection rates ranging from 0% to 84% depending on the species. A linear mixed model indicated that tick species was the primary factor associated with Spiroplasma infection. Moreover, certain Spiroplasma alleles that are highly adapted to specific tick species may explain the high infection rates in Ixodes ovatus and Haemaphysalis kitaokai. A comparison of the alleles obtained suggests that horizontal transmission between tick species may not be a frequent event. These findings provide clues to understand the transmission cycle of Spiroplasma species in wild tick populations and their roles in host ticks.

mNGS Investigation of Single Ixodes pacificus Ticks Reveals Diverse Microbes, Viruses, and a Novel mRNA-like Endogenous Viral Elements

“…Blattabacterium, Buchnera, Spiroplasma , and Candidatus Midichloria were all present in at least 90% of samples, and Candidatus Carsonella was identified in 25% of samples (Figure 2). To our knowledge, none of these known endosymbionts have been commonly identified in I. pacificus , and Blattabacterium, Buchnera , and Candidatus Carsonella represent the first report of these genera in any tick 44,45 .…”

Tick-Borne Zoonotic Diseases and Its Control

“…Members of the genus Spiroplasma are Gram-positive bacteria without cell walls. Some Spiroplasma species can cause disease in arthropods such as bees, whereas others provide their host resistance to pathogens [66]. The presence of the bacteria in the tick eggs used to initiate the primary cultures confirms that transovarial transmission of this Rickettsia occurs [67].…”

What do we know about the microbiome of I. ricinus?

“…Only two Spiroplasma spp. were validated in ticks: Spiroplasma mirum and Spiroplasma ixodetis ( Ogata et al., 2021 ). The first reported tick Spiroplasma , S. mirum , was isolated from the tick Haemaphysalis leporispalustris ( Tully et al., 1982 ).…”

“…They are commonly transmitted from ticks to vertebrate hosts through hematophagous bites ( Hofhuis et al., 2017 ). There are multiple ways of bacteria propagation in tick populations - vertical (transovarial) transmission (from females to eggs and the subsequent generation) ( Harris et al., 2017 ; Ogata et al., 2021 ; Tufts and Diuk-Wasser, 2021 ) or horizontal transmission (from tick to tick through co-feeding on a host or by feeding on an infected host) ( Belli et al., 2017 ; Moraes-Filho et al., 2018 ; Nah and Wu, 2021 ). The vertebrate pathogens may persist for long periods in infected ticks thanks to their ability to be transmitted from one stage to another (transstadial transmission) ( Kalmár et al., 2015 ; Răileanu et al., 2020 ).…”