Tick Vector of Heartland Virus Identified
Viable viruses yielded from eight pools comprising deplete nymphs of Amblyomma americanum
TUESDAY, July 23 (HealthDay News) -- The tick Amblyomma americanum has been identified as the vector of the heartland virus (HRTV), the first pathogenic Phlebovirus (Family: Bunyaviridae), according to a study published online July 22 in the American Journal of Tropical Medicine and Hygiene.
Noting that HRTV infection was recently described in two Missouri famers, Harry M. Savage, Ph.D., from the U.S. Centers for Disease Control and Prevention in Fort Collins, Colo., and colleagues collected 56,428 ticks representing three species at 12 sites, including the patients' farms.
The researchers found that nearly all the ticks collected were Amblyomma americanum (97.5 percent of collected ticks) and Dermacentor variabilis. Ten pools, which included deplete nymphs of Amblyomma americanum obtained from a patient farm and a nearby conservation area, were positive for HRTV on reverse transcription-polymerase chain reaction. Viable viruses were yielded from eight pools. Tick strains and human strains were found to be very similar based on sequence data from the nonstructural protein of the small segment, with ≥97.6 percent sequence identity.
"This is the first study to isolate HRTV from field-collected arthropods and to implicate ticks as potential vectors," the authors write. "Amblyomma americanum likely becomes infected by feeding on viremic hosts during the larval stage, and transmission to humans occurs during the spring and early summer when nymphs are abundant and actively host seeking."
Abstract (http://www.ajtmh.org/content/early/2013/06/27/ajtmh.13-0209.abstract )Full Text (http://www.ajtmh.org/content/early/2013/06/27/ajtmh.13-0209.full.pdf+html )