Scrub Typhus, a Disease with Increasing Threat in Guangdong, China

February Scrub Typhus, a Disease with Increasing Threat in Guangdong, China Wu De 0 1 Kou Jing 0 1 Zhang Huan 0 1 Zhou Hui Qiong 0 1 Corina Monagin 0 1 Zhong Jian Min 0 1 Huang Ping 0 1 Ke Chang Wen 0 1 Lin Jin Yan 0 1 0 1 Institute of Pathogenic Microbiology, Center for Disease Control and Prevention of Guangdong , Guangzhou, People's Republic of China, 2 Metabiota , Inc. , San Francisco , California, United States of America, 3 Department of Biological Sciences, Humboldt State University , Arcata, California 95521 , United States of America 1 Academic Editor: Ulrike Gertrud Munderloh, University of Minnesota, UNITED STATES There has been a rapid increase in the number of scrub typhus cases in Guangdong Province, China. For this reason, an epidemiologic study was conducted to understand the characteristics of scrub typhus epidemics in Guangdong. From 2006 to 2013, the incidence of human cases increased from 0.4321 to 3.5917 per 100,000 with a bimodal peak in human cases typically occurring between May and November. To detect the prevalence of Orientia tsutsugamushi among suspected human cases and rodents, we performed ELISA tests of IgM/IgG and nested PCR tests on 59 whole blood samples from the suspected cases and 112 spleen samples from the rodents. Suspected cases tested positive for anti-O. tsutsugamushi IgM and IgG 66.1% (39/59) and 50.8% (30/59) of the time, respectively. Additionally, 20.3% (12/59) of blood samples and 13.4% (15/112) of spleen samples were positive for PCR. Phylogenetic analysis revealed that there were four definable clusters among the 27 nucleotide sequences of the 56-kDa antigen genes: 44.4% Karp (12/27), 25.9% Kato (7/ 27), 22.2% Gilliam (6/27) and 7.4% TA763 (2/27). We concluded many suspected cases may result in diagnostic errors; therefore, it is necessary to perform laboratory tests on suspected cases in hospitals. The high infection rate of O. tsutsugamushi among the limited rodents tested suggested that further rodent sampling throughout the province is necessary to further define high-risk areas. Furthermore, the multiple co-circulating genotypes of O. tsutsugamushi play a key role in the pervasiveness of scrub typhus in the Guangdong area. - Funding: Blood sample collection of suspected cases and surveillance data analysis were supported by the Twelfth Five-Year Medical Research Key Project of PLA (AWS 11L 009), samples collection of rodents and sequencing were supported by Metabiota Inc. (formally known as Global Viral Forecasting). Co-author Corina Monagin is employed by Metabiota, Inc. Metabiota, Inc. provided support in the form of salary for author CM, and helped in the preparation of the manuscript, but did not have any Approximately one billion people are affected with Scrub typhus [1]. Scrub typhus caused by O. tsutsugamushi is a major cause of acute febrile illnesses in the Asia-Pacific region. Descriptions of scrub typhus have been found in Chinese writings as early as 313 A.D. and were first described in modern literature in Japan in 1810 [2,3]. Moreover, the O. tsutsugamushi strain Ikeda was originally isolated from a patient in 1979 in the Niigata Prefecture, Japan [4]. Scrub typhus is an endemic disease threatening a wide area of the Asia-Pacific rim, extending from additional role in the study design, data collection and analysis, or decision to publish. Competing Interests: Metabiota Inc., provided funding towards this study. Co-author Corina Monagin is employed by Metabiota, Inc. There are no patents, products in development or marketed products to declare. This does not alter the authors adherence to all the PLOS ONE policies on sharing data and materials. Mainland China initially considered Scrub typhus an infectious disease in 1952. Nationwide surveillance data showed that approximately 315-1,844 cases had been reported annually before 1985 [6]. However, this disease was not reported in northern China (north of the Yangtze River) until 1986 when it appeared in the Shandong Province [7] and has since rapidly expanded further north. Subsequently, over 2,000 cases were reported on annually [8]. Since scrub typhus is not a notifiable infectious disease in mainland China, the registration of scrub typhus cases was aborted in 1990. As a result this has led to an underestimation of its prevalence and risk. Due to an increasing number of cases and multiple outbreaks in the past two decades [8,9,10], scrub typhus surveillance was restarted by the China Information System for Disease Control and Prevention (CISDCP) in some Chinese provinces beginning in January 2006. Since 1948 when the first case of scrub typhus was reported in the subtropical zone of southern China in the Guangdong Province, it has been considered the main focus of scrub typhus studies [11]. However, the local epidemiological characteristics of scrub typhus and the molecular genotype of O. tsutsugamushi remain unclear. For this reason, this study analyzed the surveillance data from 2006 to 2013 in order to describe the epidemiological characteristics of scrub typhus. We collected specimens from suspected human patients and rodents to perform antibody tests and genetic typing based on the 56-kDa type-specific antigen (TSA). Materials and Methods Ethics statement This study was carried out in strict accordance with AnimalProtection Law of the Peoples Republic of China and with the local governments approvals and permits to conduct this study. The rodents in this study were not an endangered or protected species and were collected from hills and villages in Qingyuan and Shantou area. The protocol was approved by Guangdong Provincial Animal Care and Use Committee (Permit Number: 140025) and Medical Ethical Committee of the Center for Disease Control and Prevention of Guangdong Province. All surgery was performed under diethyl ether anesthesia and all efforts were made to minimize suffering. All participants were voluntary with written informed consents and the data was analyzed anonymously. The definition for a suspected case was a fever, a field exposure history within 3 weeks before onset, and either lymphadenectasis or rash. Additionally, suspected cases could simultaneously present with a fever, lymphadenectasis, and a rash. The criterion for a clinical case was the definition of a suspected case plus an eschar/ulcer, or the concurrent presentation of a fever and an eschar/ulcer along with a history of previous epidemic contact. Confirmed cases were suspected cases or clinical cases with one of the following laboratory test results: WeilFelix OXK agglutination titer 1:160, a 4-fold increase in immunoglobulin G (IgG) using indirect immunofluorescent assay (IFA), a positive result in pathogenic isolation, and/or a positive result with nested polymerase chain reaction (PCR). Following these definitions, scrub typhus cases diagnosed by physicians in Guangdong were reported to the local CDC through the CISDCP. Surveillance data, including demographi (...truncated)