Epidemiology of tsutsugamushi disease and its relationship with meteorological factors in Xiamen city, China.

Li Luo,Xingchun Liu,Min Chen,Zeyu Zhao,Qingqing Hu,Zhinan Guo,Tianmu Chen,Yao Wang,Jia Rui,Yuanzhao Zhu,Fanghua Chen,Zhao Lei,Meng Yang,Jeanne Salje

doi:10.1371/journal.pntd.0008772

Abstract

Tsutsugamushi disease (TD) is an acute infectious disease caused by Orientia tsutsugamushi. This study aimed to analyze the epidemiological features of TD, investigate chigger mites and their hosts, and investigate the meteorological factors affecting TD incidence and the host of O. tsutsugamushi in Xiamen city, China. Data on reported TD cases were collected from 2006 to 2018. Spearman’s correlation test were used for identifying the relationship between meteorological factors and TD incidence and whether meteorological factors affect the host of O. tsutsugamushi. The incidence of reported TD increased gradually from 2006, reached a peak of 4.59 per 100,000 persons in 2014, and then decreased gradually. The TD incidence was seasonal, with epidemic periods occurred mainly in summer and autumn. Patients aged 40–60 years had the highest proportion of cases, accounting for 44.44% of the total cases. Farmers had the largest number of cases among all occupational groups. Rattus Norvegicus was the most common host, accounting for the largest proportion of rats (73.00%), and the highest rat density was observed in March and October every year. There were significant positive correlations between the number of reported cases and average temperature, sunshine duration, and rainfall as well as between rat density and average temperature. On phylogenetic analysis, 7 sequences of hosts and human TD cases obtained from health records demonstrated the highest similarities to the Kato, Karp, and Gilliam strains. No correlations were observed between rat density, and sunshine duration and rainfall. The transmission of TD in Xiamen city, China, was seasonal, and its incidence was affected by several meteorological factors including average temperature, sunshine duration, and rainfall. However, the host of O. tsutsugamushi was only affected by average temperature.

Highlights

Tsutsugamushi disease (TD), known as scrub typhus, is an acute infectious disease caused by Orientia tsutsugamushi (Rickettsia tsutsugamushi)
Tsutsugamushi disease (TD) is a natural focal disease caused by Orientia tsutsugamushi, which is widespread in some areas
We aimed to explore the relationship between meteorological factors and the incidence of TD and host of O. tsutsugamushi

Summary

Introduction

Tsutsugamushi disease (TD), known as scrub typhus, is an acute infectious disease caused by Orientia tsutsugamushi (Rickettsia tsutsugamushi). It is a zoonotic disease, with rodents as the main source of infection and chigger mite larvae as the vector. TD is widely distributed in southern Asia in a triangular form, from northern Japan and far eastern Russia in the north to northern Australia in the south and to Pakistan and Afghanistan in the west along with the islands of the western Pacific and the Indian Ocean [2]. In Southeast Asia, TD is a leading cause of treatable non-malarial febrile illness [4]

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