ABSTRACT
@#Tsutsugamushi disease, also known as scrub typhus, is a zoonosis caused by Orientia tsutsugamushi, with rats as the main sources of infection and chigger mites as the only medium of transmission, and has no effective vaccines. Tsutsugamushi disease can be divided into summer, autumn and winter types according to seasons in China, while the summer type is characterized by strong virulence, typical and severe symptoms, high rates of misdiagnosis and mortality. The summer type of tsutsugamushi disease is distributed in the south of 31°N in China, with the epidemic time from June to August, and the cases are predominantly females, farmers and people at ages of over 40 years. Affected by natural environment, social and economic factors, the epidemic areas and the number of cases of summer type of tsutsugamushi disease are increasing continuously. Based on publications pertaining to the epidemiology of summer type of tsutsugamushi disease in China from 1960 to 2023, this review summarizes the mechanism of transmission, epidemiological characteristics and influencing factors, so as to provide the basis for prevention and control of summer type of tsutsugamushi disease in China.
ABSTRACT
@#Abstract: Chigger mites belong to the phylum Arthropoda, class Arachnida, sub-class Acari, order Parasitiformes, family Trombiculidae and Leeuwenhoekiidae, with a wide range of species. There are more than 3 700 known species of mites globally, of which 531 species in 46 genera from three sub-families have been recorded in China, and 320 species of chigger mites recorded from 3 subfamilies and 32 genera in Yunnan Province. At this stage, chigger mites are the only vectors of scrub typhus, with about 60 species worldwide being potential vectors. Six vectorial mite species have been confirmed in China, including Leptotrombidium deliense, L.scutellare, L.rubellum, L.sialkotense, L.kaohuense, L.insulare. Yunnan Province has reported five vectorial mite species, including the previously-mentioned five species except for L.sialkotense. The zoogeographic study divided Yunnan Province into 5 zoogeographic areas, namely, Central Hengduan Mountains subregion, Southern Hengduan Mountains subregion, Eastern Yunnan Plateau subregion, Western Yunnan Plateau subregion, Southern Yunnan Mountainous subregion. The Southern Hengduan Mountains subregion has the highest number of known genera and species of scrub typhus and the highest number of scrub typhus cases, with 216 species in 22 genera from 3 subfamilies, and all 5 species of vector scrub typhus were distributed. Southern Yunnan Mountain subregion has the least number of mite species, with 91 species in 12 genera from three sub-families, with L. scutellare being the dominant vectorial mite species across the province. Due to suitable natural geographic conditions in Yunnan Province, vectorial mites can propagate rapidly, leading to a large number of scrub typhus cases. According to statistics, the number of scrub typhus cases in Yunnan Province has rapidly increased, with 15.40 times, 20.64 times and 28.91 times more cases in 2016, 2017 and 2018 respectively than in 2006. Scrub typhus remains a serious public health problem in Yunnan Province, posing a threat to the health of the local population. Therefore, prevention and control efforts should continue to focus on the affected areas and the general public.