Severe Fever with Thrombocytopenia Syndrome Virus RNA in Ticks from Wild Mongooses in Okinawa Prefecture, Japan.

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging zoonotic tick-borne disease caused by SFTS virus (SFTSV). SFTSV has a wide spectrum of animal hosts and is considered to circulate in an enzootic tick-vertebrate-tick cycle. A previous seroepidemiological study showed the presence of anti-SFTSV antibodies in wild mongooses (Herpestes auropunctatus) and indicated that outdoor activity was associated with an increased risk of tick bites among Okinawa residents. However, the association of SFTSV with wild mongooses and ticks remains unclear. To understand the association between ticks and mongooses with respect to the SFTSV enzootic cycle, we investigated the presence of SFTSV RNA in ticks collected from wild mongooses on the Okinawa Island. A total of 638 ticks belonging to 2 genera and 3 species (Haemaphysalis hystricis, Haemaphysalis formosensis, and Ixodes granulatus) were collected from 22 wild mongooses from 2016 to 2021. SFTSV RNA was detected in two pools of H. hystricis larvae collected from a wild mongoose in the central area of the main island of Okinawa in 2017. Although the prevalence of SFTSV in ticks from wild mongooses is low, endemic circulation of the virus in Okinawa should be carefully monitored to prevent future infections.

Seroepidemiological study of severe fever with thrombocytopenia syndrome in animals and humans in Okinawa, Japan.

In Okinawa prefecture, Japan, the first case of severe fever with thrombocytopenia syndrome (SFTS) was confirmed in August 2016, and this case remains to be the only reported case of SFTS in Okinawa. The epidemiological investigation indicated that the patient had been infected on the main island of Okinawa, but source and route of infection were unknown. Therefore, to understand the possible source and route of SFTS virus (SFTSV) infection in Okinawa, we performed a seroepidemiological study of SFTSV among animals and dwellers in Okinawa and conducted a questionnaire survey to investigate risk factors for tick bites in Okinawa. Among the 1,035 serum samples from four different animal species, anti-SFTSV antibodies were detected in only 4.2% wild mongoose (Herpestes auropunctatus) serum samples. To our knowledge, this is the first study to report the detection of anti-SFTSV antibodies in wild mongooses. Meanwhile, all 1,104 human inhabitants tested negative for anti-SFTSV antibodies, suggesting that the frequency of SFTSV exposure is low in Okinawa. Logistic regression analysis of the questionnaire results showed that outdoor activity was associated with an increased risk of tick bite among Okinawa residents. Despite the current low frequency of SFTSV infection in animals and humans, endemic circulation of the virus in Okinawa should be carefully monitored in the area for preventing future infections.

Clinical characteristics of stonefish "Oni-daruma-okoze" envenomation in Japan.

AIM: Stonefish, known in Japan as "Oni-daruma-okoze" (Synanceia verrucosa Block et Schneider), inhabit the waters surrounding the Okinawa/Amami districts. By far, habubites have been limited to these areas mainly due to climatic conditions. Due to changes promoted by global warming and increasing tourism, concerns regarding the potential for stonefish envenomation as well as jellyfish stings on the main island of Japan are increasing. However, few studies of stonefish envenomation have been reported in Japan. The current study aimed to comprehensively examine for the first time the clinical characteristics of stonefish envenomation in Japan. METHODS: We administered retrospective questionnaire surveys between January 2013 and December 2017 to determine patient characteristics, treatment, and clinical outcomes of stonefish envenomation. We compared patient characteristics between tourists and non-tourists. RESULTS: Over the 5-year study period, 15 patients were identified from four hospitals. More than 70% of stonefish envenomation cases occurred in the northern part of Okinawa Main Island. All patients recovered well, including four patients with severe stonefish envenomation. In two severe cases, the length of hospitalization was more than 1 week (8-9 days). Antivenom was not given. There were no significant differences between tourists and non-tourists with regard to baseline characteristics. CONCLUSIONS: During a 5-year period, 15 cases of stonefish envenomation occurred in Japan. The patients recovered well without treatment with antivenom.

Clinical characteristics of jellyfish stings in Japan.

AIM: Jellyfish known as "habu-kurage" (Chironex yamaguchii) inhabit the waters surrounding Okinawa and Amami, Japan, and jellyfish stings are limited to areas outside the Japanese main island. However, the shifts promoted by global warming and increasingly intensive interactions with people have led to concerns regarding the possibility of increased jellyfish stings on the main island of Japan. Similar concerns are being raised all over the world. However, studies examining clinical characteristics of jellyfish stings have been limited to Australia, the USA, Europe, and South-East Asia. Thus, this study aimed to examine for the first time the clinical characteristics of jellyfish stings in Japan. METHODS: We undertook retrospective questionnaire surveys from January 2013 to December 2017 to determine patient characteristics, treatment, and clinical outcomes. We compared patient characteristics between tourists and non-tourists. The primary end-point of the present study was to clarify the clinical characteristics of jellyfish stings. RESULTS: Over the 5-year study period, 204 patients were identified from eight hospitals based on the basic questionnaire, and 35 patients with moderate-to-severe jellyfish stings were also identified. All patients recovered well, including five patients with severe jellyfish stings. Antivenom was not given. The time intervals from the occurrence of jellyfish stings to hospital arrival significantly differed between tourists and non-tourists (P = 0.049), and all tourists visited the emergency department (P = 0.009). CONCLUSIONS: Approximately 40 cases of jellyfish stings occurred annually in Japan between 2013 and 2017. Patients recovered well without the use of antivenom.