Anaplasma phagocytophilumInfection in Small Mammal Hosts ofIxodesTicks, Western United States

Janet E Foley,Richard N Brown,Nathan C Nieto,Jennifer Adjemian,Haydee Dabritz

doi:10.3201/eid1407.071599

Abstract

A total of 2,121 small mammals in California were assessed for Anaplasma phagocytophilum from 2006 through 2008. Odds ratios were >1 for 4 sciurids species and dusky-footed woodrats. High seroprevalence was observed in northern sites. Ten tick species were identified. Heavily infested rodent species included meadow voles, woodrats, deer mice, and redwood chipmunks.

Highlights

A total of 2,121 small mammals in California were assessed for Anaplasma phagocytophilum from 2006 through 2008
Deer mice have been reported to be exposed to A. phagocytophilum [10,11], we found little evidence of this in our study
I. spinipalpis, which occurred on woodrats, deer mice, squirrels, and chipmunks, functions as a primary vector for B. bissettii in a woodrat enzootic cycle [16], and Neotoma mexicana and I. spinipalpis have an enzootic cycle in Colorado for A. phagocytophilum

Summary

Anaplasma phagocytophilum Infection in Small

A total of 2,121 small mammals in California were assessed for Anaplasma phagocytophilum from 2006 through 2008. Infested rodent species included meadow voles, woodrats, deer mice, and redwood chipmunks. The northern coast range and Sierra Nevada foothills of California [4,7], where abundant rodents include deer mice (Peromyscus spp.), woodrats, and chipmunks (Tamias spp.), have moderate to high levels of granulocytic anaplasmosis. We sought to evaluate granulocytic anaplasmosis exposure and infection and describe the Ixodes spp. tick fauna in small mammals from central and northern coastal California. Individual small mammals’ risk for A. phagocytophilum exposure and infection were assessed as a function of sex, species, and location by calculating odds ratios (OR) and 95% confidence intervals (CI). A total of 2,121 small mammals, including 2,100 rodents, 20 shrews, and 1 lagomorph, were evaluated for exposure to and infection with A. phagocytophilum and infestation with Ixodes spp. ticks (Table 1).

Tamiasciurus douglasii

Yolo County

Findings

Conclusions