Molecular epidemiological study of Scrub Typhus in residence, farm and forest habitats from Yunnan Province, China

Abstract

The number of people suffering from scrub typhus, which is not of concern, is increasing year by year, especially in Yunnan Province, China. From June 1, 2021 to August 15, 2022, a total of 505 mammalian samples were collected from farm, forest, and residential habitats with high incidence of scrub typhus in Yunnan, China, for nPCR (nested PCR) and qPCR (quantitative real-time PCR) detection of Orientia tsutsugamushi. A total of 4 orders of murine-like animals, Rodentia (87.52%, n=442), Insectivora (10.29%, n=52), Lagomorpha (1.79%, n=9) and Scandentia (0.40%, n=2) were trapped. Comparing the qPCR infection rates in the three habitats, it was no significant difference that the infection rate of residential habitat (44.44%) and that of the farm habitat (45.05%, P>0.05), which is much larger than that of the forest habitat (3.08%) (P<0.001). Three genotypes (Karp, Kato and TA763) of O. tsutsugamushi were found from Yunnan, China in this study. We found a tendency for scrub typhus to migrate from forests to residential habitats. Author SummaryScrub typhus is acute febrile infectious disease caused by Orientia tsutsugamushi that threatens nearly 1 billion people. According to the data we have obtained, the incidence rate of infected people has reached 23.84/100,000 population until December 2022 in Yunnan, China. The incidence rate has increased non-negligibly Compared with 0.65/100,000 population in 2006. Among them, the incidence rate has increased by 71.14% from 2019 to 2022. Scrub typhus is transmitted by the bite of chigger larvae with murine-like animals as the main source of infection Rodentia are the most important reservoir hosts, followed by Insectivora. Therefore, in view of the influencing factor of human habitat, we used qPCR (quantitative real-time PCR) and nPCR (nested PCR) techniques to analyze the prevalence of O. tsutsugamushi in hosts of different human habitats from June 2021 to August 2022. Our research shows that the diversity of O. tsutsugamushi genotypes in Yunnan Province provides guidance for the prevention and Control of scrub typhus. And it was found that the infection rate of O. tsutsugamushi in murine-like animals is quite different in different human habitats, especially the high infection rate in residential habitat and farm habitat, suggesting that O. tsutsugamushi can be infected without wilderness history.