Ticks expand their US distribution

By |  April 8, 2016
Distribution by county of recorded presence of I. scapularis and I. pacificus in the continental United States. “A” is from Denis et al. 1998, and shows 1907–1996 distribution. “B” shows 1907–2015 distribution. Counties classified as established (red or green) for a given tick species had at least six ticks or two life stages recorded within a single calendar year. Counties with fewer ticks of a single life stage were classified as reported (blue or yellow) for the tick species. Counties shown in white indicate “no records.” Image: CDC/Oxford University Press

Distribution by county of recorded presence of I. scapularis and I. pacificus in the continental United States. “A” is from Denis et al. 1998, and shows 1907–1996 distribution. “B” shows 1907–2015 distribution. Counties classified as established (red or green) for a given tick species had at least six ticks or two life stages recorded within a single calendar year. Counties with fewer ticks of a single life stage were classified as reported (blue or yellow) for the tick species. Counties shown in white indicate “no records.”
Image: CDC/Oxford University Press

A study by the U.S. Centers for Disease Control & Prevention (CDC) division of Vector-Borne Infectious Diseases researchers Drs. Rebecca Eisen, Lars Eisen and Charles Ben Beard finds that two Lyme disease vector species are being documented more frequently in the continental United States. The team updated a 1998 distribution map, and found the following:

  • Ixodes scapularis, the blacklegged tick, has been documented in 1,420 (45.7 percent) of the 3,110 continental United States counties.
  • I. pacificus, the western blacklegged tick, as been documented in 111 (3.6 percent) of the counties — and thus, the risk of Lyme disease (and other disease agents) have been identified in a total of 1,531 (49.2 percent) counties spread across 43 states.

“This marks a 44.7 percent increase in the number of counties that have recorded the presence of these ticks since the previous map was presented in 1998, when 1,058 counties in 41 states reported the ticks to be present,” the team writes in the January issue of the Journal of Medical Entomology.

The majority of county status changes from the previous distribution study occurred in the North-Central and Northeastern states, the team found. Southern distribution remained fairly stable.

More Information:
JME.oxfordjournals.org
EntomologyToday.org

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1 Comment on "Ticks expand their US distribution"

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  1. Jordan says:

    Pretty disturbing news! Hopefully awareness is being spread to these new areas where ticks are moving towards. Understanding the dangers of ticks and what diseases they can spread is important.