F. Scott Dahlgren

Increasing Incidence of Ehrlichia chaffeensis and Anaplasma phagocytophilum in the United States, 2000–2007

Ehrlichia chaffeensis causes human monocytic ehrlichiosis, and Anaplasma phagocytophilum causes human granulocytic anaplasmosis. These related tick-borne rickettsial organisms can cause severe and fatal illness. During 2000-2007, the reported incidence rate of E. chaffeensis increased from 0.80 to 3.0 cases/million persons/year. The case-fatality rate was 1.9%, and the hospitalization rate was 49%. During 2000-2007, the reported incidence of A. phagocytophilum increased from 1.4 to 3.0 cases/million persons/year. The case-fatality rate was 0.6%, and the hospitalization rate was 36%. Rates among female patients were lower than among male patients for ehrlichiosis (rate ratio = 0.68) and anaplasmosis (rate ratio = 0.70). Most (80%) ehrlichiosis and anaplasmosis cases met only a probable case definition, although, use of a polymerase chain reaction to confirm infections increased during 2000-2007. Heightened reporting of these diseases will likely continue with improving recognition, changing surveillance practices, and appropriate application of diagnostic assays.

No Visible Dental Staining in Children Treated with Doxycycline for Suspected Rocky Mountain Spotted Fever

OBJECTIVE To evaluate whether cosmetically relevant dental effects occurred among children who had received doxycycline for treatment of suspected Rocky Mountain spotted fever (RMSF). STUDY DESIGN Children who lived on an American Indian reservation with high incidence of RMSF were classified as exposed or unexposed to doxycycline, based on medical and pharmacy record abstraction. Licensed, trained dentists examined each childs teeth and evaluated visible staining patterns and enamel hypoplasia. Objective tooth color was evaluated with a spectrophotometer. RESULTS Fifty-eight children who received an average of 1.8 courses of doxycycline before 8 years of age and who now had exposed permanent teeth erupted were compared with 213 children who had never received doxycycline. No tetracycline-like staining was observed in any of the exposed childrens teeth (0/58, 95% CI 0%-5%), and no significant difference in tooth shade (P=.20) or hypoplasia (P=1.0) was found between the 2 groups. CONCLUSIONS This study failed to demonstrate dental staining, enamel hypoplasia, or tooth color differences among children who received short-term courses of doxycycline at <8 years of age. Healthcare provider confidence in use of doxycycline for suspected RMSF in children may be improved by modifying the drugs label.

Fatal Rocky Mountain Spotted Fever in the United States, 1999–2007

Death from Rocky Mountain spotted fever (RMSF) is preventable with prompt, appropriate treatment. Data from two independent sources were analyzed to estimate the burden of fatal RMSF and identify risk factors for fatal RMSF in the United States during 1999-2007. Despite increased reporting of RMSF cases to the Centers for Disease Control and Prevention, no significant changes in the estimated number of annual fatal RMSF cases were found. American Indians were at higher risk of fatal RMSF relative to whites (relative risk [RR] = 3.9), and children less than 10 years of age (RR=5.1) [corrected] and adults ≥ 70 years of age (RR = 3.0) were also at increased risk relative to other ages. Persons with cases of RMSF with an immunosuppressive condition were at increased risk of death (RR = 4.4). Delaying treatment of RMSF was also associated with increased deaths. These results may indicate a gap between recommendations and practice.

Human granulocytic anaplasmosis in the United States from 2008 to 2012: a summary of national surveillance data.

Human granulocytic anaplasmosis is an acute, febrile illness transmitted by the ticks Ixodes scapularis and Ixodes pacificus in the United States. We present a summary of passive surveillance data for cases of anaplasmosis with onset during 2008-2012. The overall reported incidence rate (IR) was 6.3 cases per million person-years. Cases were reported from 38 states and from New York City, with the highest incidence in Minnesota (IR = 97), Wisconsin (IR = 79), and Rhode Island (IR = 51). Thirty-seven percent of cases were classified as confirmed, almost exclusively by polymerase chain reaction. The reported case fatality rate was 0.3% and the reported hospitalization rate was 31%. IRs, hospitalization rates, life-threatening complications, and case fatality rates increased with age group. The IR increased from 2008 to 2012 and the geographic range of reported cases of anaplasmosis appears to have increased since 2000-2007. Our findings are consistent with previous case series and recent reports of the expanding range of the tick vector I. scapularis.

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

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, 4,613 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.

Phylogeography of Rickettsia rickettsii Genotypes Associated with Fatal Rocky Mountain Spotted Fever

Rocky Mountain spotted fever (RMSF), a tick-borne zoonosis caused by Rickettsia rickettsii, is among the deadliest of all infectious diseases. To identify the distribution of various genotypes of R. rickettsii associated with fatal RMSF, we applied molecular typing methods to samples of DNA extracted from formalin-fixed, paraffin-embedded tissue specimens obtained at autopsy from 103 case-patients from seven countries who died of RMSF. Complete sequences of one or more intergenic regions were amplified from tissues of 30 (29%) case-patients and revealed a distribution of genotypes consisting of four distinct clades, including the Hlp clade, regarded previously as a non-pathogenic strain of R. rickettsii. Distinct phylogeographic patterns were identified when composite case-patient and reference strain data were mapped to the state and country of origin. The phylogeography of R. rickettsii is likely determined by ecological and environmental factors that exist independently of the distribution of a particular tick vector.

Q Fever in the United States: Summary of Case Reports from Two National Surveillance Systems, 2000-2012

Q fever is a worldwide zoonosis historically associated with exposure to infected livestock. This study summarizes cases of Q fever, a notifiable disease in the United States, reported to the Centers for Disease Control and Prevention through two national surveillance systems with onset during 2000-2012. The overall incidence rate during this time was 0.38 cases per million persons per year. The reported case fatality rate was 2.0%, and the reported hospitalization rate was 62%. Most cases (61%) did not report exposure to cattle, goats, or sheep, suggesting that clinicians should consider Q fever even in the absence of livestock exposure. The prevalence of drinking raw milk among reported cases of Q fever (8.4%) was more than twice the national prevalence for the practice. Passive surveillance systems for Q fever are likely impacted by underreporting and underdiagnosis because of the nonspecific presentation of Q fever.

Self-reported treatment practices by healthcare providers could lead to death from Rocky Mountain spotted fever.

Among 2012 Docstyle survey respondents, 80% identified doxycycline as the appropriate treatment for Rocky Mountain spotted fever in patients ≥ 8 years old, but only 35% correctly chose doxycycline in patients <8 years old. These findings raise concerns about the higher pediatric case-fatality rate of Rocky Mountain spotted fever observed nationally. Targeted education efforts are needed.

Community-Based Control of the Brown Dog Tick in a Region with High Rates of Rocky Mountain Spotted Fever, 2012–2013

Rocky Mountain spotted fever (RMSF) transmitted by the brown dog tick (Rhipicephalus sanguineus sensu lato) has emerged as a significant public health risk on American Indian reservations in eastern Arizona. During 2003–2012, more than 250 RMSF cases and 19 deaths were documented among Arizonas American Indian population. The high case fatality rate makes community-level interventions aimed at rapid and sustained reduction of ticks urgent. Beginning in 2012, a two year pilot integrated tick prevention campaign called the RMSF Rodeo was launched in a ∼600-home tribal community with high rates of RMSF. During year one, long-acting tick collars were placed on all dogs in the community, environmental acaricides were applied to yards monthly, and animal care practices such as spay and neuter and proper tethering procedures were encouraged. Tick levels, indicated by visible inspection of dogs, tick traps and homeowner reports were used to monitor tick presence and evaluate the efficacy of interventions throughout the project. By the end of year one, <1% of dogs in the RMSF Rodeo community had visible tick infestations five months after the project was started, compared to 64% of dogs in Non-Rodeo communities, and environmental tick levels were reduced below detectable levels. The second year of the project focused on use of the long-acting collar alone and achieved sustained tick control with fewer than 3% of dogs in the RMSF Rodeo community with visible tick infestations by the end of the second year. Homeowner reports of tick activity in the domestic and peridomestic setting showed similar decreases in tick activity compared to the non-project communities. Expansion of this successful project to other areas with Rhipicephalus-transmitted RMSF has the potential to reduce brown dog tick infestations and save human lives.

Q Fever Is Underestimated in the United States: A Comparison of Fatal Q Fever Cases from Two National Reporting Systems

Two national surveillance systems capturing reports of fatal Q fever were compared with obtained estimates of Q fever underreporting in the United States using capture-recapture methods. During 2000-2011, a total of 33 unique fatal Q fever cases were reported through case report forms submitted to the Centers for Disease Control and Prevention and through U.S. death certificate data. A single case matched between both data sets, yielding an estimated 129 fatal cases (95% confidence interval [CI] = 62-1,250) during 2000-2011. Fatal cases of Q fever were underreported through case report forms by an estimated factor of 14 and through death certificates by an estimated factor of 5.2.