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Recent studies on scrub typhus and Rickettsia tsutsugamushi in Shandong Province--China
C Xiangrui1, W Jinju, Z Yongguo
1Institute of Microbiology and Epidemiology, Beijing, China.
Abstract:
In an outbreak of scrub typhus occurred 138 cases in 1986 in Menying County of Shandong Province of China which were confirmed through clinical and epidemiological surveys and laboratory techniques. In the endemic areas, the predominant species of mite is Leptotrombidium (L.) scutelarae and the predominant rodent is Apodemus agrarius, which may be the main vector and reservoir. Several strains of Rickettsia tsutsugamushi (R.T.) were obtained from mites, wild mice and patients, of which 3 human strains (SDH871, SDH875, SDH878) cause illness and some deaths in mice, except SDH871. The LD50 of SDH878 is 3.4. Cross-protection was observed among the strains, SDH871, SDH878, and prototype strain karp. Also the antibodies in mucoid peritoneal fluid were detectable with high titer. Shandong R.T. belongs to the serotype of the Gilliam strain.
Insights
An outbreak of scrub typhus in China identified Leptotrombidium mites and Apodemus rodents as key vectors. Rickettsia tsutsugamushi strains were isolated, showing cross-protection and belonging to the Gilliam serotype.
Area of Science:
- Epidemiology
- Medical Entomology
- Microbiology
Background:
- Scrub typhus outbreaks pose significant public health challenges.
- Identifying vectors and reservoirs is crucial for controlling disease transmission.
Purpose of the Study:
- To investigate an outbreak of scrub typhus in Menying County, Shandong Province, China.
- To identify the predominant vectors and reservoirs of the disease.
- To characterize the Rickettsia tsutsugamushi strains involved.
Main Methods:
- Clinical and epidemiological surveys were conducted.
- Laboratory techniques confirmed cases and identified Rickettsia tsutsugamushi strains.
- Mite and rodent populations were surveyed in endemic areas.
Main Results:
- 138 cases of scrub typhus were confirmed in 1986.
- Leptotrombidium (L.) scutelarae mites and Apodemus agrarius rodents were identified as the predominant species.
- Three human Rickettsia tsutsugamushi (R.T.) strains (SDH871, SDH875, SDH878) were isolated, with SDH878 showing an LD50 of 3.4.
- Cross-protection was observed between strains SDH871, SDH878, and the Karp strain.
- Antibodies were detected in high titers in mucoid peritoneal fluid.
- Shandong R.T. strains belong to the Gilliam serotype.
Conclusions:
- Leptotrombidium mites and Apodemus rodents are likely the primary vectors and reservoirs for scrub typhus in the studied region.
- The isolated Rickettsia tsutsugamushi strains exhibit antigenic relationships and belong to the Gilliam serotype, informing potential vaccine development and treatment strategies.