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 – 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
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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.
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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 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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Project description:Ehrlichia chaffeensis, the causative agent of human monocytic ehrlichiosis, is transmitted by Amblyomma americanum ticks, which are most abundant in the southern United States. Because serologic evidence suggests that residents of Connecticut are exposed to E. chaffeensis, A. americanum ticks were collected in Connecticut and Rhode Island for PCR analysis to detect E. chaffeensis DNA. Eight of 106 (7.6%) A. americanum ticks from Connecticut and 6 of 52 (11.5%) from Rhode Island contained E. chaffeensis DNA. Thus, E. chaffeensis is present in ticks in southern New England and transmission of E. chaffeensis may occur there.
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Project description:The predominant human-biting tick throughout the southeastern United States is Amblyomma americanum. Its ability to transmit pathogens causing Lyme disease-like illnesses is a subject of ongoing controversy. Results of previous testing by the Department of Defense Human Tick Test Kit Program and other laboratories indicated that it is highly unlikely that A. americanum transmits any pathogen that causes Lyme disease. In contrast, a recent publication by Clark and colleagues (K. L. Clark, B. Leydet, and S. Hartman, Int. J. Med. Sci. 10:915-931, 2013) reported detection of Lyme group Borrelia in A. americanum using a nested-flagellin-gene PCR. We evaluated this assay by using it and other assays to test 1,097 A. americanum ticks collected from humans. Using the Clark assay, in most samples we observed nonspecific amplification and nonrepeatability of results on subsequent testing of samples. Lack of reaction specificity and repeatability is consistent with mispriming, likely due to high primer concentrations and low annealing temperatures in this protocol. In six suspect-positive samples, Borrelia lonestari was identified by sequencing of an independent gene region; this is not a Lyme group spirochete and is not considered zoonotic. B. burgdorferi was weakly amplified from one pool using some assays, but not others, and attempts to sequence the amplicon of this pool failed, as did attempts to amplify and sequence B. burgdorferi from the five individual samples comprising this pool. Therefore, B. burgdorferi was not confirmed in any sample. Our results do not support the hypothesis that A. americanum ticks are a vector for Lyme group Borrelia infections.
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