Phylogenetic diversity of Orientia tsutsugamushi isolates in patients with scrub typhus in Bengaluru, India.

Scrub typhus has re-emerged as an important cause of acute febrile illness in India. There is a dearth of information on strain diversity of Orientia tsutsugamushi from Karnataka, India, hence the present study sought to address this issue. One hundred clinically suspected cases of scrub typhus/rickettsiosis (as per the DHR-ICMR guidelines) were included. Nested-polymerase chain reaction (PCR) for 56-kDa gene and phylogenetic analysis was performed. PCR was positive in 22 cases and phylogenetic analysis showed the presence of different strains, with predominance of clustering (57%) with Gilliam-type for the first time in Karnataka. Knowledge of genetic diversity has implications in development of diagnostics and vaccine.

[Studies on three types of natural foci of tsutsugamushi disease in eastern part of China].

OBJECTIVE: In order to identify the types of natural foci of tsutsugamushi disease to provide basis for prevention, a series of studies were carried out in Fujian, Zhejiang and Jiangsu Provinces. METHODS: (1) Representative points for investigation in three Provinces were selected. (2) Data on geographical landscape and epidemiology were collected. (3) Field survey and experimental studies on rats and chigger mites in relation to the disease. RESULTS: Three representative types of natural foci of tsutsugamushi disease were demonstrated. They were (1) Coastal island type, mainly in Fujian with major reservoir host as Rattus losea and major vector mite as L. deliense; prevalent season: summer; type of Rt: Gilliam: (2) Inland mountain - forest type in Zhejiang with major reservoir host as R. confucianus and major vector miteas L. gaohuense; prevalent season: summer; type of Rt: Gilliam. (3) Inland plain - hills type in Jiangsu with major reservoir hosts: Apodemus agrarius, R. confucianus, R. norvegicus and Crocidura lasiura; major vector mite: L. scutellare; prevalent seasons: autumn and winter; type of Rt: Kawasaki. CONCLUSION: The types of Rt, reservoir hosts, vector chigger mites and epidemiological features of tsutsugamushi disease in Fujian, Zhejiang and Jiangsu Province were found different. Thus, the preventive measures should also be distinct from one another.

[Studies on natural foci of tsutsugamushi disease of the autumn-winter type in Jiangsu].

Before 1986, tsutsugamushi disease was known only prevalent in south to Zhejiang Province in our country, belonged to the summer type and Leptotrombidium (L.) deliense was regarded as the main vector. In October 1986, the authors found this disease in Nanjing and carried out a series of studies in 1986-1992. The results were as follows: Tsutsugamushi disease was epidemic in Nanjing and north of Jiangsu (including: Dongtai, Haian, Rudong, Jinhu, Hanjiang, Jiangdu); belonged to the autumn-winter type; the main reservoir hosts were Apodemus agrarius, Rattus confucianus, R. norvegicus and Crocidura lasiura; the transmitting vector was L. (L.) scutellare; the pathogen of tsutsugamushi disease of the autumn-winter type-Rickettsia tsutsugamushi belonged to low-virulent strain, and could not easily be detected; after the inoculated mice were treated with diluted cyclophosphamide solution, 14 strains of R. tsutsugamushi have been isolated from rats, mites and patients; serological typing of their sera showed that they belonged to the Gilliam type; natural foci in Jiangsu could be divided into two types--flat land and hilly land.

Rickettsiosis in Japan.

The rickettsial diseases of man in Japan include Tsutsugamushi disease (scrub typhus), murine typhus, which occurs sporadically, and one of spotted fever group diseases, recognized as a new entity since 1984. Starting from 1976, there has been a remarkable resurgence in the number of reported cases of Tsutsugamushi disease in Japan after several years of virtual absence, and endemics are still continuing after reaching a prominent outbreak in 1984. Its yearly incidences from 1982 to 1986 were 538, 749, 971, 890 and 738, respectively. This resurgence is most likely related to an increase of vector mite colonies that carry Rickettsia tsutsugamushi. However, it cannot be explained as to how these foci of vector mites developed. The existence of spotted fever group disease had not been recognized until quite recently. This rickettsiosis was first identified in Tokushima and Kochi Prefectures in 1984. To date, the estimated total number of sero-positive cases is over 45 cases. The causative rickettsiae were isolated from the blood of 5 patients using cell culture methods and the identification of these rickettsiae is now being carried out.