Dataset Information

Detection of Ehrlichia chaffeensis DNA in Amblyomma americanum ticks in Connecticut and Rhode Island.

ABSTRACT: 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.

SUBMITTER: Ijdo JW

PROVIDER: S-EPMC87657 | biostudies-literature | 2000 Dec

REPOSITORIES: biostudies-literature

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Detection of Ehrlichia chaffeensis DNA in Amblyomma americanum ticks in Connecticut and Rhode Island.

Ijdo J W JW Wu C C Magnarelli L A LA Stafford K C KC Anderson J F JF Fikrig E E

Journal of clinical microbiology 20001201 12

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. chaf ...[more]

PMID: 11101616

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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.

Project description:Cytauxzoon felis is a tick-borne hemoprotozoan parasite that causes life-threatening disease in domestic cats in the United States. Currently, the platforms for C. felis research are limited to natural or experimental infection of domestic cats. This study aims to develop an alternative model by infecting Amblyomma americanum ticks with C. felis via direct injection. Amblyomma americanum adults were injected with C. felis-infected feline erythrocytes through two routes: directly into the digestive tract through the anal pore (IA injection), or percutaneously into the tick hemocoel (IH injection). RNAscope® in situ hybridization (ISH) was used to visualize the parasites within the ticks at different time points after injection. Four months after injection, ticks were divided into 3 infestation groups based on injection methods and inoculum type and fed on 3 naïve cats to assess the ticks' ability to transmit C. felis. Prior to the transmission challenge, selected ticks from each infestation group were tested for C. felis RNA via reverse transcription-PCR (RT-PCR). In both IA- and IH-injected ticks, ISH signals were observed in ticks up to 3 weeks after injection. The number of hybridization signals notably decreased over time, and no signals were detected by 4 months after injection. Prior to the transmission challenge, 37-57% of the sampled ticks were positive for C. felis RNA via RT-PCR. While the majority of injected ticks successfully attached and fed to repletion on all 3 cats during the transmission challenge, none of the cats became infected with C. felis. These results suggest that injected C. felis remained alive in ticks but was unable to progress to infective sporozoites after injection. It is unclear why this infection technique had been successful for other closely related tick-borne hemoprotozoa and not for C. felis. This outcome may be associated with uncharacterized differences in the C. felis life cycle, the lack of the feeding or molting in our model or absence of gametocytes in the inoculum. Nonetheless, our study demonstrated the potential of using ticks as an alternative model to study C. felis. Future improvement of a tick model for C. felis should consider other tick species for the injection model or utilize infection methods that more closely emulate the natural infection process.

Dataset Information

Detection of Ehrlichia chaffeensis DNA in Amblyomma americanum ticks in Connecticut and Rhode Island.

Publications

Detection of Ehrlichia chaffeensis DNA in Amblyomma americanum ticks in Connecticut and Rhode Island.

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