Case Report: Family Cluster of Japanese Spotted Fever

Trends in the Incidence of Japanese Spotted Fever in Japan: A Nationwide, Two-Decade Observational Study from 2001-2020

The worldwide spread of tick-borne diseases (TBDs) has become a public health concern. Therefore, this study aimed to clarify trends in the incidence of Japanese spotted fever (JSF), one of Japan's most prevalent TBDs. Weekly infectious disease reports were used to calculate the annual incidence rates (AIRs) of JSF. Data were stratified by age and sex, and joinpoint regression analysis was performed to estimate the annual percentage change (APC). AIR and APC were geographically compared among the 47 prefectures. A total of 3,453 JSF cases were observed from 2001 to 2020. The AIR per 100,000 population was 0.03 in 2001, which increased approximately 10-fold to 0.33 in 2020. The average APC (AAPC) during the study period was 12.3% (95% CI: 10.7-13.9). By age group, the incidence of JSF increased more rapidly among the older population: 11.5% (95% CI: 10.1-12.9) in those aged ≥ 65 years and 8.9% (95% CI: 6.4-11.5) in those aged < 50 years. Although the AIR over the past two decades was higher in climatically warm regions located in southwestern Japan and on the Pacific coast, increases in the AAPC were notable in colder regions located in eastern Japan. The incidence of JSF continues to increase in Japan, especially among older populations and in eastern prefectures, where the disease has not been previously diagnosed.

A Cluster of Japanese Spotted Fever Cases Associated with Cemetery Visits in Wakayama City, Japan

Japanese spotted fever (JSF) is a tick-borne rickettsiosis caused by Rickettsia japonica. Although the number of JSF cases has been increasing, exceeding 300 per year since 2017, clusters of cases are rare. Here, we report a cluster of seven JSF cases, the first nonfamilial cluster of the disease documented in the Japanese literature, and describe the management of the outbreak through prompt investigation and control-and-prevention measures performed collaboratively by members from the clinical, laboratory, and public health fields. All seven cases in the cluster had visited a cemetery in September or October of 2019. R. japonica was detected in whole-blood and/or skin samples from six patients and in the larvae of Haemaphysalis hystricis collected in a field survey. The evidence suggested that this cluster of cases was caused by the conjunction of two circumstances within a short period of time: an increase in the number of visitors to a cemetery during a Buddhist event and an increase in the number of infectious tick larvae in the cemetery through hatching (vertical transmission from infected females). Delays in the treatment of JSF can lead to severe manifestations. Early interventions through collaborative efforts among members from the clinical, laboratory, and public health fields are important for controlling outbreaks, raising the awareness of the public, and diagnosing and treating patients.

Clinical, epidemiological, and laboratory features of Rickettsia africae infection, African tick-bite fever: A systematic review

African tick-bite fever (ATBF), caused by Rickettsia africae, is the main tick-borne rickettsiosis and the second most frequent cause of fever after malaria in travelers returning from sub-Saharan Africa. General descriptions on ATBF were made in the first two decades after recognized as a new infectious entity, and since then, many authors have contributed to the knowledge of the disease by reporting clinical cases in scientific literature. We developed a systematic review that evaluated all available evidence in the literature regarding clinical, epidemiological, and laboratory features of confirmed R. africae rickettsiosis cases. We followed the recommendations made by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guide. A total of 48 scientific publications (108 confirmed cases) were analyzed in order to extract data for developing this review. Overall, our results show that R. africae rickettsiosis is more frequent in males in the age group of 18-64 years, more than 80% of the cases occurred in European travelers, South Africa was the country where most infections were acquired, and almost 40% of cases occurred in clusters. Clinically, more than 80% of the cases had fever and eschar (55% developed multiple eschars), rash was present in less than the half of cases, and lymphangitis was not a common sign (11%). Headache, myalgia and regional lymphadenopathy were predominant nonspecific clinical manifestation (mean of 60%, 49% and 51%, respectively). Our results show that at least 70% of R. africae cases had altered laboratory parameters, most often showing an increase in transaminases and C-reactive protein. Tetracycline-class antibiotics, as monotherapy, were used in most (>90%) of the patients. Overall, only 4% of cases had complications, 12% required hospitalization, and there was a 100% rate of clinical recovery.