Geographic Distribution and Presentation of Spotted Fever Group Rickettsioses and Zoonoses
Rickettsioses, a Gram-negative obligate intracellular bacteriumare, are a group of diseases that historically include rickettsial diseases. Current classification of rickettsial diseases includes 3 main biogroups: spotted fever group rickettsioses (SFGR), typhus group rickettsioses (TGR), and scrub typhus. SFGR are found worldwide while its geographic distribution varying for different Rickettsia spp., and the causative rickettsiae are often named according to the location or the arthropod vectors where they are first described. Most SFGR are tick-borne, except Rickettsia akari and R. felis. SFGR are neglected emerging diseases, particularly in developing countries In Taiwan, there havebeen increased reports of isolation and identification of SFGR, including novel strains, from arthropods in recent years. However, serological investigation of human SFGR was poorly characterized. Besides, researches of geographic distribution of human SFGR infections and rickettsial diseases such as Q fever, scrub typhus and murine typhus are rarely reported by clinicians in Taiwan.
Q fever, scrub typhus, and murine typhus are notifiable diseases in Taiwan, and clinicians are requested to report patients who are clinically suspected of having these diseases to Taiwan CDC. Suspected cases of Q fever, scrub typhus and murine typhus reported to Centers for Disease Control, Taiwan (Taiwan CDC) are excluded by confirmatory tests for each suspected disease. It is reasonable to speculate that SFGR might account for some of these cases that have either similar clinical manifestations or share exposure to arthropod vectors as a risk factor but are treated with agents effective against rickettsioses without appropriate diagnosis.
Patients who were clinically suspected of Q fever, scrub typhus, and murine typhus were enrolled because these diseases are common zoonoses or arthropod-vectored diseases in Taiwan and are clinically difficult to differentiate them from SFGR. The confirmation or exclusion of each disease was determined according to the final reports of notifiable diseases of Taiwan CDC. However, it is rare to find information related to geographic distribution of SFGR in Taiwan.
1. Retrospective study is employed to inspect if suspected or confirmed cases of zoonoses are infected with SFGR.
2. SuperGIS software are adopted to map geographic distribution of cases of Q fever, scrub typhus and murine typhus, to assist readers in comprehending the cases of diverse diseases and SFGR infections were distributed in both mountainous and plains areas.
1. From April 2004 to December 2009, resident address of each confirmed case of Q fever, scrub typhus, murine typhus and leptospirosis are marked as points on map to present case locations.
2. Inspect reported residual specimen of cases that are clinically suspected of Rickettsioses or dengue fever, and mark resident address of cases that are suspected of SFGR on the same map according to inspection result.
Steps of Creating Geographic Distribution Map of SFGR Infection Cases:
1.Downloaded world maps (HYP_HR_SR_OB_DR and ne_10m_admin_0_countries_lakes) on Nature Earth website (http://www.naturalearthdata.com/downloads/), and overlaid the two layers on SuperGIS Desktop to display the map and names of Taiwan and countries around.
2. Entered resident address of each case into query bar of Google earth to show location of confirmed cases of Q fever, scrub typhus, murine typhus and leptospirosis on map. And saved location data of each case as kml file for following usage of data converting.
3. Adopted SuperGIS DataConvertor to convert location data in kml format into *.geo format so that geographic distribution of infection cases could be used and displayed on SuperGIS Desktop.
4. On SuperGIS Desktop, added case locations as points on layers downloaded from Nature Earth website, and zoom in/out the layers to the required scale to get geographic distribution of infection cases. (Please notice that pixel quality of layers from Nature Earth website can not support to display case distribution on Taiwan map clearly.)
5.Employed contour data of Taiwan provided by Supergeo to make and overlay Taiwan terrain layer on layers from Nature Earth website. In this way, geographic distribution of cases can be visibly viewed on the layer with terrain data.
6.Switched to Layout View on SuperGIS Desktop, insert legends like symbol, north arrow, scale bar, etc., and modified legend format according to requirements.
7.Repeated the steps above to map geographic distribution of SFGR infection cases.
8.Afterwards, utilized Microsoft PowerPoint to edit and compose maps and legends created on SuperGIS Desktop.
1.This is the first investigation of human SFGR in Taiwan. The results of this investigation illustrate that human SFGR infections do exist in Taiwan, but no further indigenous human SFGR was reported. Besides, working with SuperGIS products, the investigation illustrates case geographic distribution in Taiwan and shows relation between terrain and case area on map clearly instead of conveying case distribution and characteristics just in texts or tables. In this way, visibility and value of this investigation result would be heightened.
2.With case geographic distribution map built by SuperGIS software, we found that nearly half of scrub typhus cases were distributed in mountainous areas, but most cases of Q fever, murine typhus, and leptospirosis were distributed in plains areas. The cases of SFGR infections were distributed in both mountainous and plains areas, similar to scrub typhus. In concept of epidemiology, SFGR infections and scrub typhus that happened in Taiwan might share same source of infection or animal reservoir. Therefore, in clinical inference, scrub typhus infectious patients might be infected with SFGR.
3.The result that case distribution of SFGR infections is similar to scrub typhus comes from compare of two maps with bare eye. To better analyze result of this inference, we need Spatial Statistical Analyst and Spatial Analyst of SuperGIS Desktop for further statistical analyses.
4.GIS software can be extensively applied on clinical study to enrich analysis results, especially in infectious diseases. For example, we can overlay distribution layers of Infection Chain elements – Source, Susceptible Host and Transmission, and analyze geographic distribution and sequence to deploy infectious disease investigation. Such GIS applications also have a huge amount of influence over diverse aspects in addition to infectious disease investigation, including public health policy construction, Epidemiological studies, investigation of disease outbreak, monitoring of specific diseases, etc.
5.Developed by Supergeo, SuperGIS Desktop is a comprehensive and easy-to-use geographic information system with traditional Chinese and English interfaces. By utilizing SuperGIS Desktop, common-used office tools and web tools, beautiful and comprehensive maps can be built to enrich visibility and value of investigation results. For clinicians who are too busy to conduct research, SuperGIS products are highly recommended software to quickly perform investigation concepts and results in forms of meaningful maps and graphs. It can be done effortlessly through SuperGIS software, self-learning and professional assistance from Supergeo staff.
Resource: Lai, et al. (2014) “Human Spotted Fever Group Rickettsioses Are Underappreciated in Southern Taiwan, Particularly for the Species Closely-Related to Rickettsia felis”