Bacterial Diversity in <I>Amblyomma americanum</I> (Acari: Ixodidae) With a Focus on Members of the Genus <I>Rickettsia</I>

Abstract

The lone star tick, Amblyomma americanum (Acari: Ixodidae), is commonly reported from people and animals throughout the eastern U.S. and is associated with transmission of a number of emerging diseases. To better define the microbial communities within lone star ticks, 16S rRNA gene based analysis using bacteria-wide primers, followed by sequencing of individual clones (n = 449) was used to identify the most common bacterial operational taxonomic units (OTUs) present within colony-reared and wild A. americanum. The colony-reared ticks contained primarily sequence affiliated with members of the genus Coxiella (89%; 81/91), common endosymbionts of ticks, and Brevibacterium (11%; 10/91). Similarly, analysis of clones from unfed wild lone star ticks revealed that 96.7% (89/92) of all the OTUs identified were affiliated with Coxiella-like endosymbionts, as compared with only 5.1-11.7% (5/98-9/77) of those identified from wild lone star ticks after feeding. In contrast, the proportion of OTUs identified as Rickettsia sp. in wild-caught ticks increased from 2.2% (2/92) before feeding to as high as 46.8% (36/77) after feeding, and all Rickettsia spp. sequences recovered were most similar to those described from the spotted fever group Rickettsia, specifically R. amblyommii and R. massiliae. Additional characterization of the Rickettsiales tick community by polymerase chain reaction, cloning, and sequencing of 17 kDa and gltA genes confirmed these initial findings and suggested that novel Rickettsia spp. are likely present in these ticks. These data provide insight into the overall, as well as the rickettsial community of wild lone star ticks and may ultimately aid in identification of novel pathogens transmitted by A. americanum.

Update on Tick-Borne Rickettsioses around the World: a Geographic Approach

“…"Candidatus Rickettsia amblyommii" was first documented in 1981 and has since been identified as a commonly occurring and widely distributed SFG rickettsia in A. americanum ticks (127)(128)(129). "Candidatus Rickettsia amblyommii" produces a generalized infection in A. americanum that is distributed throughout multiple tissues, including the salivary glands, midgut, and ovaries (130).…”

Similarities and seasonal variations in bacterial communities from the blood of rodents and from their flea vectors

“…Most studies of vector-borne microbiota have focused on microbial communities within the microenvironment of the arthropod vector, including studies on lice (Reed and Hafner, 2002), fleas (Jones et al, 2010;Hawlena et al, 2013), mosquitoes (Rani et al, 2009;Osei-Poku et al, 2012), flies (Hornok et al, 2008), ticks (Heise et al, 2010;Andreotti et al, 2011;Hawlena et al, 2013), mites (Netusil et al, 2005;Reeves et al, 2006) and leeches (Worthen et al, 2006). Diverse microbial communities were found in these vectors, and most microbial species were represented sparsely or occurred in only a few individual vectors.…”

“…Diverse microbial communities were found in these vectors, and most microbial species were represented sparsely or occurred in only a few individual vectors. Some studies also indicated that the composition of these microbial communities often varies across time and space (Kirstein et al, 1997;Wielinga et al, 2006;van Overbeek et al, 2008;Jones et al, 2010) and that these variations are linked largely to the characteristics of the arthropod (for example, its species, life stage, diet and blood engorgement level; Pidiyar et al, 2004;Moreno et al, 2006;Heise et al, 2010;Jones et al, 2010;Hawlena et al, 2013). Nevertheless, because vector-borne microbes spend a part of their lives in the blood of the vertebrate host, it is important to consider also the internal environment of this host.…”

Pathogen-mediated manipulation of arthropod microbiota to promote infection

“…The diversity of microbial communities has been characterized in different ticks (16)(17)(18)(19)(20)(21). The effect of tick microbiota on the transmission of human infectious diseases, and the molecular mechanisms underlying these processes, has only recently received attention.…”