The single 500-mg dose of azithromycin was as effective as the 1-week course of daily 200-mg doses of doxycycline for the treatment of mild scrub typhus acquired in South Korea.

To identify potential vector species of scrub typhus in the Republic of Korea (ROK), chigger mites were harvested from wild rodents captured at nine localities in October 2005. The bodies of the chigger mites were individually punctured with a fine pin, squeezed out internal contents, and examined for Orientia tsutsugamushi DNA by nested polymerase chain reaction. The exoskeleton of associated chiggers was mounted on glass slides with polyvinylalcohol (PVA) medium for identification. Among 830 individuals belonging to 4 genera and 14 species, O. tsutsugamushi was detected from 22 chiggers of six species, with an overall infection rate of 2.7%. The infection rate was highest for Leptotrombidium palpale (5.3%), followed by Neotrombicula japonica (4.3%), Leptotrombidium scutellare (3.7%), Leptotrombidium orientale (3.6%), Eushoengastia koreaensis (1.9%), and Leptotrombidium pallidum (1.5%). This study first reported O. tsutsugamushi infection from N. japonica and E. koreaensis larvae in the ROK. The population densities of L. pallidum (33.4 chiggers/rodent), historically confirmed as a primary vector of scrub typhus in the ROK, were high, whereas its infection rate was relatively low (1.5%). However, E. koreaensis was only collected from 154 individuals at seven collection sites and its infection rate was demonstrated relatively high (mean 1.9%). Additional studies are needed to determine the role of vector species in the epidemiology of scrub typhus.

The nucleotide sequences (534 to 546 bp) of the groEL gene, which encodes the 60-kDa heat shock protein GroEL, from 15 rickettsial strains were determined and compared. In the phylogenetic tree created by the unweighted pair group method with arithmetic averages and the neighbor-joining method, rickettsial strains could be distinguished from Ehrlichia strains. Five spotted fever group strains, four typhus group strains, and six scrub typhus group (STG) strains were differentiated as distinct entities. Unlike gltA and ompA gene analyses, differentiation between members of the genus Rickettsia and the STG rickettsiae by groEL gene analysis was possible. In comparison with 16S rRNA gene analysis, the groEL gene has a higher degree of divergence among the rickettsiae. We therefore successfully developed rapid differentiation methods, PCRrestriction fragment length polymorphism analysis and a species-specific PCR, based on the groEL gene sequences. Four Korean isolates were identified by these methods and groEL gene analysis. The results suggest that the groEL gene is useful for the identification and characterization of rickettsiae.

We report here on the case of a child who was infected with scrub typhus, and we made the diagnosis according to the serology and by performing PCRs on the child's eschar. The patient was treated with azithromycin, and he did not experience any complications. Performing nested PCR on the eschar might be both a rapid diagnostic test for scrub typhus in the early acute stage and a differential test as to whether or not a scab is a scrub typhus eschar. CASE REPORTA 7-year-old boy was admitted to Seonam University Hospital because of his 7-day history of a high fever and rash. The physical examination at the time of admission revealed a papulomacular skin rash on his trunk that soon spread to his extremities. Enlarged tender lymph nodes were palpable in his right neck and back of the neck areas. The body temperature was 39°C, the heart rate was 115/min, and the respiration rate was 28. The patient's leukocyte count was 5,700/mm 3 (68.5% polymorphonuclear cells and 23.9% lymphocytes), his hemoglobin level was 11.2 g/dl, and the platelet count was 91,000/mm 3 . Other laboratory values were as follows: aspartate aminotransferase, 170 U/liter; alanine aminotransferase, 189 U/liter; lactate dehydrogenase, 230 U/liter; and creatine phosphokinase, 255 U/liter. We suspected that the patient was suffering from viral exanthema or infectious mononucleosis with a mobiliform rash. The patient was treated symptomatically with acetaminophen. Over the next 2 days, dyspnea developed and his temperature increased to 39.8°C. Radiographs of the chest showed an interstitial pneumonia pattern. On the third hospital day, we inadvertently found an eschar-like crust lesion on the front part of the scalp (Fig. 1), but his mother insisted that the crust was caused by minor trauma. We carefully took the history once again. Seven days before admission, he had played with his brother on the grass of Citizen's Park in Gwangju City. We wanted to know whether the crust was eschar or not. An informed consent was obtained to take a sample of the eschar and blood samples, and then a piece of crust was removed from the scalp. We immersed the crust into about 1 ml of saline. We performed nested PCR for the gene that encodes the 56-kDa protein that is specific for Orientia tsutsugamushi. Based on the clinical diagnosis of scrub typhus, azithromycin therapy was initiated. Defervescence occurred within 12 h. However, because the optimal dosage of azithromycin for the treatment of scrub typhus has not been determined, especially for children, we added another 500 mg of azithromycin at 24 h after the first dose to experimentally reduce the risk of relapse or therapeutic failure. Sixty hours after the azithromycin administration was stopped, a fever of 38.0°C, malaise, and headache were again developed. The therapy with azithromycin was restarted. Azithromycin (250 mg) once a day for an additional 5 days was added. After this administration, his symptoms, such as fever and malaise, were relieved and he was discharged without complications. A second serology f...