Blood meal analysis to identify reservoir hosts for Amblyomma americanum ticks.
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ABSTRACT:
SUBMITTER: Allan BF
PROVIDER: S-EPMC3322017 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:A collection of 1145 clones from an EST project on female tick salivary gland genes was hybridized on glass slides to RNA extracted from several feeding stages of adult female tick salivary glands, including unfed and replete, and from adult male ticks, either unfed or fed in the presence or absence of female ticks. In the female ticks, the early fed (<50 mg) and partially fed (30-200 mg) groups were very similar. The fast feeding (350-500 mg) and replete ticks were similar to each other, but different from the partially fed. The unfed ticks were more similar to the fast feeding â replete groups than the early fed-partially fed groups. In the males, there were differences between the males fed in the presence or absence of females, but overall, these groups were very similar. The unfed ticks were significantly different from the fed ticks. Males showed clear differences with females in expression, as well. The unfed females had high levels of genes involved in protein synthesis, while genes possibly involved in survival on the host, such as anticoagulants, seemed to be most expressed in the early and partially fed states. By contrast, in the males, the protein synthesis genes were expressed more in all three groups, while the putative secreted genes for survival were expressed less. Keywords: time course, effect of feeding, sex, effect of presence of females All samples were compared to the partially fed females. Females consisted of five groups: unfed, early fed, partially fed, fast feeding and replete. Four or five biological replicates were done of each, with the dyes used in both possible ways. In the males, three groups were used: unfed, feeding in the presence of females, and feeding in the absence of females. Two biological replicates were done of the feeding males, and one of extracts was hybridized twice for the males fed in the presence of females. Unfed males used one RNA sample, extracted from a large pool of ticks.
2010-06-11 | E-GEOD-5010 | biostudies-arrayexpress
Project description:The Lone Star tick, Amblyomma americanum, transmits several bacterial pathogens including species of Anaplasma and Ehrlichia. Amblyomma americanum also hosts a number of non-pathogenic bacterial endosymbionts. Recent studies of other arthropod and insect vectors have documented that commensal microflora can influence transmission of vector-borne pathogens; however, little is known about tick microbiomes and their possible influence on tick-borne diseases. Our objective was to compare bacterial communities associated with A. americanum, comparing Anaplasma/Ehrlichia -infected and uninfected ticks. Field-collected questing specimens (n = 50) were used in the analyses, of which 17 were identified as Anaplasma/Ehrlichia infected based on PCR amplification and sequencing of groEL genes. Bacterial communities from each specimen were characterized using Illumina sequencing of 16S rRNA gene amplicon libraries. There was a broad range in diversity between samples, with inverse Simpson's Diversity indices ranging from 1.28-89.5. There were no statistical differences in the overall microbial community structure between PCR diagnosed Anaplasma/Ehrlichia-positive and negative ticks, but there were differences based on collection method (P < 0.05), collection site (P < 0.05), and sex (P < 0.1) suggesting that environmental factors may structure A. americanum microbiomes. Interestingly, there was not always agreement between Illumina sequencing and PCR diagnostics: Ehrlichia was identified in 16S rRNA gene libraries from three PCR-negative specimens; conversely, Ehrlichia was not found in libraries of six PCR-positive ticks. Illumina sequencing also helped identify co-infections, for example, one specimen had both Ehrlichia and Anaplasma. Other taxa of interest in these specimens included Coxiella, Borrelia, and Rickettsia. Identification of bacterial community differences between specimens of a single tick species from a single geographical site indicates that intra-species differences in microbiomes were not due solely to pathogen presence/absence, but may be also driven by vector life history factors, including environment, life stage, population structure, and host choice.
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Project description:A rickettsial isolate (isolate MOAa) belonging to the spotted fever group (SFG) was obtained from the lone star tick Amblyomma americanum. We used PCR to characterize the genes for the rickettsial outer membrane proteins rOmpA and rOmpB. We sequenced the PCR products (domains I of both the rompA gene and the rompB gene) of MOAa and WB-8-2, another rickettsial isolate from A. americanum. To place MOAa and WB-8-2 and two other nonpathogenic isolates (Rickettsia rickettsii Hip2 and Rickettsia montana M5/6) with respect to their putative sister species, we included them in a phylogenetic analysis of 9 Rickettsia species and 10 Rickettsia strains. Our phylogenetic results implied three evolutionary lineages of SFG rickettsiae and that WB-8-2 and MOAa were most closely related to R. montana. New World isolates were not the most closely related to each other (they did not form a clade). Rather, our results supported four independent origins (introductions) of rickettsiae into North America from different Old World regions. The results of our phylogenetic analysis did not support the hypothesis of a stable coevolution of rickettsiae and their tick hosts. Finally, we examined the rompA gene of a nonpathogenic rickettsial symbiont isolated from the tick Ixodes scapularis. In a phylogenetic analysis, the symbiont was placed as the sister to R. montana and its isolates. The relationship of this symbiont to R. montana raised questions as to the potential origin of pathogenic SFG rickettsiae from nonpathogenic tick symbionts, or vice versa.
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Project description:A collection of EST clones from female tick Amblyomma americanum salivary glands was hybridized to RNA from different feeding stages of female tick salivary glands and from unfed or feeding adult male ticks. In the female ticks, the expression patterns changed dramatically upon starting feeding, then changed again towards the end of feeding. On beginning feeding, genes possibly involved in survival on the host increased in expression as did many housekeeping genes. As feeding progressed, some of the survival genes were downregulated, while others were upregulated. When the tick went into the rapid feeding phase, many of the survival genes were downregulated, while a number of transport-associated genes and genes possibly involved in organ degeneration increased. In the males, the presence of females during feeding made a small difference, but feeding made a larger difference. Males showed clear differences from females in expression, as well. Protein synthesis genes were expressed more in all male groups than in the partially fed females, while the putative secreted genes involved in avoiding host defenses were expressed less.
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