DEPARTMENT OF COMPARATIVE PATHOBIOLOGY
Jennifer McQuiston, DVM, MS,
DACVPM
Leader, Zoonoses
Team, Geographic Medicine and Health
Promotion Branch, Centers
for Disease Control and Prevention
Atlanta, GA
“Emergence
Of Rocky Mountain Spotted Fever
In The Brown Dog Tick In Eastern Arizona”
Thursday, January 25,
2007
VPTH 112
3:30 p.m.
Abstract:
Rocky Mountain
spotted fever (RMSF), caused by Rickettsia
rickettsii, is a tickborne disease that can cause severe or fatal illness
in humans and dogs. In some cases, fatality rates may approach 20-30% in
untreated cases. In the United States,
the principal tick vectors of RMSF are Dermacentor
variabilis (the American dog tick) and Dermacentor
andersonii (the Rocky
Mountain wood tick).
Although the pathogen is distributed in ticks throughout much of the
continental United States,
RMSF is rarely reported from Arizona,
which lies outside the range of the common tick vectors and has a hot, dry
climate generally unfavorable to most species of ticks. However, from June 2002
through October 2004, 16 cases of RMSF, including 2 fatal cases, were
identified from 2 small communities in rural eastern Arizona.
An investigation provided evidence
that the outbreak in this Arizona
community was likely caused by a novel tick vector, Rhipicephalus sanguineus (the brown dog tick). This outbreak most
likely occurred because of unique ecological circumstances that supported an
uncontrolled stray dog population, high densities of ticks, and frequent dog-human
interactions, especially among children and dogs. The emergence of RMSF in
previously unrecognized areas due to transmission by novel tick vectors, or due
to habitat expansion of established vectors, should be recognized as a
possibility by both medical and veterinary practitioners.
References:
1. Demma LJ, Traeger MS, Nicholson WL, Paddock CD, Blau DM,
Eremeeva ME, et al. Rocky Mountain spotted fever from an unexpected tick vector
in Arizona.
NEJM 2005; 353(6):5870594