Sylvatic maintenance of granulocytic anaplasmosis in the western US

Anaplasma phagocytophilum is an emerging tick-borne
pathogen of humans, horses, sheep, dogs, and
wildlife. In humans, granulocytic anaplasmosis (GA)
may be associated with pyrexia, headache, myalgia,
nausea, and ataxia, organ failure, susceptibility to
opportunistic infections, neuritis, or respiratory
complications with a case fatality rate up to 5% in
some areas. The putative reservoir for A.
phagocytophilum in the western United States is the
dusky-footed woodrat (Neotoma fuscipes). Evidence to
implicate the woodrat as the reservoir includes high
PCR- and seroprevalence in enzootic areas, frequent
infestation with the tick vector, Ixodes pacificus,
and results of experimental infection studies that
show woodrat infection persisting for 1-8 months.
Unlike in the eastern United States where a single
vector species and a dominant reservoir host species
maintain a sylvatic cycle, in the western US, there
are multiple ecologically significant reservoir hosts
including gray squirrels (Sciurus griseus) and
chipmunks (Tamias spp.). The goal of this research
was to identify the role of a number of abundant but
potential reservoirs for A. phagocytophilum in the
Western United States.