Increasing Incidence of Ehrlichiosis in the United States: A Summary of National Surveillance of Ehrlichia chaffeensis and Ehrlichia ewingii Infections in the United States, 2008–2012

Abstract

Abstract. Human ehrlichiosis is a potentially fatal disease caused by Ehrlichia chaffeensis and Ehrlichia ewingii. Cases of ehrlichiosis are reported to Centers for Disease Control and Prevention through two national surveillance systems: Nationally Notifiable Diseases Surveillance System (NNDSS) and Case Report Forms. During 2008-2012,613 cases of E. chaffeensis infections were reported through NNDSS. The incidence rate (IR) was 3.2 cases per million person-years (PYs). The hospitalization rate (HR) was 57% and the case fatality rate (CFR) was 1%. Children aged < 5 years had the highest CFR of 4%. During 2008-2012, 55 cases of E. ewingii infection were reported through NNDSS. The national IR was 0.04 cases per million PY. The HR was 77%; no deaths were reported. Immunosuppressive conditions were reported by 26% of cases. The overall rate for ehrlichiosis has increased 4-fold since 2000. Although previous literature suggests E. ewingii primarily affects those who are immunocompromised, this report shows most cases occurred among immunocompetent patients. This is the first report to show children aged < 5 years with ehrlichiosis have an increased CFR, relative to older patients. Ongoing surveillance and reporting of tick-borne diseases are critical to inform public health practice and guide disease treatment and prevention efforts.

Diagnosis and Management of Tickborne Rickettsial Diseases: Rocky Mountain Spotted Fever and Other Spotted Fever Group Rickettsioses, Ehrlichioses, and Anaplasmosis — United States

“…During 2008-2012, cases were primarily reported from Missouri; however, cases also were reported from 10 other states within the distribution of the principal vector, the lone star tick, A. americanum (5,57) ( Figure 13). Although E. ewingii ehrlichiosis initially was reported predominantly among persons who were immunosuppressed, passive surveillance data from 2008-2012 indicated that the majority of persons (74%) with reported E. ewingii infection did not report immunosuppression (5). No fatal cases of E. ewingii ehrlichiosis have been reported.…”

“…Incidence generally increases with age, with the highest age-specific incidences occurring among persons aged 60-69 years (5,13,50). Case-fatality rates are highest among children aged <10 years and adults aged ≥70 years, and an increased risk for death has been documented among persons who are immunosuppressed (5,13). In areas where ehrlichiosis is endemic, the actual disease incidence is likely underrepresented in estimates that are based on passive surveillance (51)(52)(53).…”

“…Cases have been reported from an increasing number of counties (5) (Figure 11). Incidence generally increases with age, with the highest age-specific incidences occurring among persons aged 60-69 years (5,13,50). Case-fatality rates are highest among children aged <10 years and adults aged ≥70 years, and an increased risk for death has been documented among persons who are immunosuppressed (5,13).…”

“…SFG rickettsiosis, ehrlichiosis, and anaplasmosis are nationally notifiable in the United States. Cases have been reported in each month of the year, although most cases are reported during April-September, coincident with peak levels of tick host-seeking activity (3)(4)(5)(9)(10)(11)(12)(13)(14). The distribution of tickborne rickettsial diseases varies geographically in the United States and approximates the primary tick vector distributions, making it important for health care providers to be familiar with the regions where tickborne rickettsial diseases are common.…”

“…The reported incidence of tickborne rickettsial diseases in the United States has increased during the past decade (3)(4)(5). Tickborne rickettsial diseases continue to cause severe illness and death in otherwise healthy adults and children, despite the availability of effective antibacterial therapy.…”