All Posts Tagged With: "lone star ticks"

Excerpt:

In this study, we evaluated Amblyomma americanum (lone star tick)
in Mississippi for the presence of Ehrlichia chaffeensis,
causative agent of human monocytic ehrlichiosis; Ehrlichia
ewingii, causative agent of human and canine granulocytic
ehrlichiosis; Borrelia lonestari, putative agent of southern
tick-associated rash illness; Francisella tularensis, the agent
of tularemia; and Rickettsia spp., particularly R. amblyommii, a
suspected pathogen. We collected adult A. americanum from four
regions of Mississippi: Northeast, Northwest, Southeast, and
East. Of the ticks collected, 192 were dissected and DNA was
extracted for nested polymerase chain reaction (PCR) assays to
detect the above bacteria. In all, 3% of tick extracts had
evidence of Borrelia sp., 4% for E. chaffeensis, 6% for E.
ewingii, and 44% for a Rickettsia species. As determined by
sequencing, most Rickettsia spp. were R. amblyommii. In addition,
extracts from 42 pools (total of 950) of larval A. americanum
collected in Southwest Mississippi were tested for the presence
of E. chaffeensis and Rickettsia species. Of these extracts from
pools, nine of 37 (24%) were PCR positive for a Rickettsia sp.,
most often, R. amblyommii; none had evidence of E. chaffeensis,
supporting the ability of lone star ticks to transovarially
transmit R. amblyommii, but not E. chaffeensis. This study
demonstrates E.

Excerpt:

A quantitative real-time polymerase chain reaction assay to detect and quantify a portion of the outer membrane protein B gene (ompB) of Rickettsia amblyommii was employed to assess the threat of R. amblyommii exposure to humans parasitized by Amblyomma americanum (the lone star tick).

A total of 72 pools of lone star ticks removed from humans were acquired from two collections and used in this study: 44 pools of A. americanum submitted to the Department of Defense Human Tick Test Kit Program in 2003 collected from 220 individuals from 14 states, and 28 pools of A. americanum representing 120 ticks obtained from boy scouts and adult leaders at the Boy Scouts of America National Jamboree held at Fort A.P. Hill, Virginia, in 2005.

Of the 72 lone star tick pools representing 340 lone star ticks, 58 pools (80.5%) were positive for R. amblyommii. In addition, individual A. americanum ticks parasitizing humans collected as part of the Department of Defense Human Tick Test Kit Program in 2002 and 2003 from 17 states were evaluated. It was found that 244 of 367 (66.5%) individual A. americanum ticks tested positive for the presence of R. amblyommii DNA. These results clearly show that lone star ticks parasitizing humans are highly infected with R. amblyommii, which may potentiate rickettsial infection of and possibly disease in humans.

Full article: http://www.cdc.gov/ncidod/eid/index.htm

Excerpt:

To determine the cause of spotted fever cases in the southern United States, we screened Gulf Coast ticks (Amblyomma maculatum) collected in Arkansas for rickettsiae. Of the screened ticks, 30% had PCR amplicons consistent with Rickettsia parkeri or Candidatus Rickettsia amblyommii.

The Centers for Disease Control and Prevention identified Arkansas as a leading state for the incidence of Rocky Mountain spotted fever (causative agent Rickettsia rickettsii) and reported >15 cases per 1,000,000 persons in 2002 (1). Given the known cross-reactivity of serologic testing results for spotted fever group (SFG) rickettsia, it is unclear if cases outside the natural range of the vectors for R. rickettsii are misdiagnosed, if the pathogen is less virulent than previously suggested, or if additional rickettsiae are responsible for pathogenesis (2).