National Surveillance of Spotted Fever Group Rickettsioses in the United States, 2008–2012

Abstract

Abstract. Spotted fever group (SFG) rickettsioses are notifiable conditions in the United States caused by the highly pathogenic Rickettsia rickettsii and less pathogenic rickettsial species such as Rickettsia parkeri and Rickettsia sp. 364D. Surveillance data from 2008 to 2012 for SFG rickettsioses are summarized. Incidence increased from 1.7 cases per million person-years (PY) in 2000 to 14.3 cases per million PY in 2012. During 2008-2012, cases of SFG rickettsiosis were more frequently reported among males, persons of white race, and non-Hispanic ethnicity. Overall, case fatality rate (CFR) was low (0.4%), however, risk of death was significantly higher for American Indian/Alaska Natives (relative risk [RR] = 5.4) and Asian/Pacific Islanders (RR = 5.7) compared with persons of white race. Children aged < 10 years continue to experience the highest CFR (1.6%). Higher incidence of SFG rickettsioses and decreased CFR likely result from increased reporting of tick-borne disease including those caused by less pathogenic species. Recently, fewer cases have been confirmed using species-specific laboratory methods (such as cell culture and DNA detection using polymerase chain reaction [PCR] assays), causing a clouded epidemiological picture. Use of PCR and improved documentation of clinical signs, such as eschars, will better differentiate risk factors, incidence, and clinical outcomes of specific rickettsioses in the future.

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

“…On the three most affected reservations, the average annual incidence rate for 2009-2012 was approximately 1,360 cases per million persons (17). The 7%-10% case-fatality rate in these communities, which is the highest of any region in the United States, has been associated predominantly with delayed recognition and treatment (4,18).…”

“…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.…”

“…During 2008-2012, 63% of reported SFG rickettsiosis cases originated from five states: Arkansas, Missouri, North Carolina, Oklahoma, and Tennessee (4). However, SFG rickettsiosis cases have been reported from each of the contiguous 48 states and the District of Columbia (4,9,12,14).…”

“…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.…”

“…Activities that commonly result in contact with potential tick habitats include recreational pursuits (e.g., camping, hiking, fishing, hunting, gardening, and golfing) and occupational activities (e.g., forestry work, farming, landscaping, and military exercises). Although peak tick season is an important consideration, health care providers should remain aware that tickborne rickettsial illnesses have been reported in every month of the year, including winter (3)(4)(5)25,81). Climate differences and seasonal weather patterns can influence the duration and peak of tick season in a given geographic region and a given year.…”