Genetic variants of Ehrlichia chaffeensis in southern Indiana

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dc.contributor.advisor Pinger, R. R. en_US Seddighzadeh, Ali en_US
dc.coverage.spatial n-us-in en_US 2011-06-03T19:39:54Z 2011-06-03T19:39:54Z 2003 en_US 2003
dc.identifier LD2489.Z78 2003 .S43 en_US
dc.description.abstract Human monocytotropic ehrlichiosis (HME) is a tick-borne infectious disease caused by the bacterium Ehrlichia chaffeensis and transmitted by the lone star tick, Amblyomma americanum. The disease was recognized in Indiana for the first time in 1994. Since 1999, 11 cases have been confirmed in Indiana and two additional cases are under investigation. In the past five years, the cases have been reported from Crawford, Harrison, Warrick, Martin, Perry, Spencer, and Madison counties.A total of 2765 adult Amblyomma americanum ticks were collected from eight counties in southern Indiana during two field trips in May 2000. Ticks were pooled and examined for the presence of Ehrlichia chaffeensis using nested PCR with primers HE1 and HE3, specific for the 16S rRNA gene of the pathogen. Ninety-six pools of A. americanum specimens tested positive for E. chaffeensis DNA. This represented a minimum infection rate (MIR) of 3.5%.To identify different genetic forms (strains) of E. chaffeensis, the positive tick pools were probed for the Variable Length PCR Target (VLPT) gene of E. chaffeensis. The data were used to develop a geographic map of the distribution of the different strains of the pathogen. Overall, nine different genetic variants (91HE17, Arkansas, Jax, Liberty, Osceola, Sapulpa, St. Vincent, Wakulla, West Paces) of E. chaffeensis were identified from pools of ticks collected in four counties (Harrison, Perry, Pike, Warrick). All samples positive for the 16S rRNA were also positive for the VLPT gene.E. chaffeensis isolates are polymorphic in the number of repetitive sequences within the genes encoding the VLPT, and the isolates obtained illustrate this phenomenon. The high concordance rate between the 16S rRNA and the VLPT gene reveals that the VLPT gene is a very sensitive tool for detecting E. chaffeensis in the lone star ticks. We found no clear correlation between geographic distribution of different genetic variants of E. chaffeensis and the genetic polymorphism of the VLPT gene. Further study with a relatively larger sample size from a wider geographical area might be able to detect such a pattern.
dc.description.sponsorship Department of Physiology and Health Science
dc.format.extent viii, 59 leaves : ill., maps ; 28 cm. en_US
dc.source Virtual Press en_US
dc.subject.lcsh Ehrlichia chaffeensis -- Indiana. en_US
dc.subject.lcsh Amblyomma americanum -- Indiana. en_US
dc.subject.lcsh Ticks as carriers of disease -- Indiana. en_US
dc.title Genetic variants of Ehrlichia chaffeensis in southern Indiana en_US Thesis (M.S.)
dc.identifier.cardcat-url en_US

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  • Master's Theses [5293]
    Master's theses submitted to the Graduate School by Ball State University master's degree candidates in partial fulfillment of degree requirements.

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