[Investigation on natural foci of autumn-winter type tsutsugamushi disease in Shandong province].

OBJECTIVE

In order to provide basic data of tsutsugamushi disease in Shandong province, for the control and prevention of this disease in residents and army-men.

METHODS

Aetiological, serological and epidemiological methods were used to investigate the natural foci of autumn-winter type tsutsugamushi disease.

RESULTS

The peak of tsutsugamushi disease epidemic in Shandong province was in October with cases in this month accounted for 80% of all in a year, that showed autumn-winter type. The main reservoir hosts were Apodemus agrarius, Rattus norvegicus and Cricetulus triton, accounted for 82.87%, 85.47% and 13.04% respectively. It was confirmed that natural infection existed among Leptotrombidium (L.) scutellare, L. palpalis, L. linhuaikonense and Walchia pacifica. The main vector of transmission was Leptotrombidium scutellare. 41 strains of Rickettsia tsutsugamushi were isolated from the blood samples of patients, rodents and chigger mites but with weak toxicity. 90% of the serotypes of the strains belonged to Gilliam type. The distribution of the cases had a sporadic nature. More than 80% of the cases were young or middle aged peasants. Clinical symptoms were mild, with some differences in different areas.

CONCLUSION

The natural foci type of tsutsugamushi disease in Shandong could be divided into plain and hilly types.