Ehrlichia chaffeensis seroprevalenee among children in the southeast and south-central regions of the United States

Background: The reported annual incidence of human monocytic ehrlichiosis, which is due to infection with Ehrlichia chaffeensis, is as high as 5.5 per million in some states, but serosurveys suggest much higher infection rates in some populations. Objective: To estimate the prevalence of E chaffeensis infection among children aged 1 to 17 years living in the southeast and south-central United States. Design: Cross-sectional serosurvey. Setting: Seven academic pediatric medical centers in the southeastern and south-central United States. Patients: Nineteen hundred ninety-nine children (approximately 300 at each center) having their blood drawn for any reason. Main Outcome Measure: The presence of antibody at 2 different cutoff titers to E chaffeensis, as detected by indirect immunofluorescence assay. Results: Overall, 250 children (13%) had E chaffeensis antibody titers of 1:80 or higher and 61 (3%) had titers of 1:160 or higher. Age-adjusted seroprevalence rates varied widely between sites. At 1:80 or higher, the highest rate was in Winston-Salem, NC (22%), and the lowest was in Louisville, Ky (2%). At 1:160 or higher, the highest rate was in Kansas City, Mo (9%), and the lowest was in Oklahoma City, Okla (<1%). In univariate analyses, no associations were found between seroprevalence at either cutoff value and sex, race, source of specimen, or residence demographics. However, age was a significant predictor of seroprevalence at both cutoff values. In multiple logistic regression analysis, study site and age remained strong predictors of seroprevalence, but living in a nonurban ZIP code was not significantly related. Conclusion: Infection with E chaffeensis, or related ehrlichiae, may be more common in children than previously recognized.