OBJECTIVE: To study the infection rate, epidemiological features of Far-East tick-borne spotted fever in the Northeastern area of China and to provide evidence for prevention and control. METHODS: Nine cities from the three Northeastern provinces were chosen. Human serum, rat, serum, free tick sample as well as blood from suspected patients were determined by indirect immuno-fluorescence assay. Rickettsiae was identified by guinea pigs plant method. RESULTS: The overall rate of infection among human beings was 17.46%, with R. heilongjiangensis antibody the major one among the nine cities. The annual infection rate was 9.4%. In a two year period, the rates of being bitten by ticks among forestry workers was 92.8%, and 33.5% among soldiers. The antibody positive rate and tick-bite rate were positively correlated. The serum positive rate in rats was 27.3%. 20 strains were isolated from blood which confirmed that 16 cases were related to R. heilongjiangensis and another 16 cases were Far East tick-borne spotted fever. Clinical features of the patients were also analyzed. CONCLUSION: Nine cities from the east part of the Northeastern areas of China were confirmed of having R. heilongjiangensis infection (3.4% - 27.4%). Our results also demonstrated that in those above-mentioned areas, there had been an existing natural foci of Far East tick-borne spotted fever.
OBJECTIVE: To study the infection rate, epidemiological features of Far-East tick-borne spotted fever in the Northeastern area of China and to provide evidence for prevention and control. METHODS: Nine cities from the three Northeastern provinces were chosen. Human serum, rat, serum, free tick sample as well as blood from suspected patients were determined by indirect immuno-fluorescence assay. Rickettsiae was identified by guinea pigs plant method. RESULTS: The overall rate of infection among human beings was 17.46%, with R. heilongjiangensis antibody the major one among the nine cities. The annual infection rate was 9.4%. In a two year period, the rates of being bitten by ticks among forestry workers was 92.8%, and 33.5% among soldiers. The antibody positive rate and tick-bite rate were positively correlated. The serum positive rate in rats was 27.3%. 20 strains were isolated from blood which confirmed that 16 cases were related to R. heilongjiangensis and another 16 cases were Far East tick-borne spotted fever. Clinical features of the patients were also analyzed. CONCLUSION: Nine cities from the east part of the Northeastern areas of China were confirmed of having R. heilongjiangensis infection (3.4% - 27.4%). Our results also demonstrated that in those above-mentioned areas, there had been an existing natural foci of Far East tick-borne spotted fever.