[Investigation on the epidemiology of Far-East tick-borne spotted fever in the Northeastern area of China].
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.


CONCLUSIONS
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.
Wu
Yi-min
YM
Centre of Disease Control and Prevention of Shenyang Command, Shenyang 110034, China.
Zhang
Zhi-qiang
ZQ
Wang
Hong-jun
HJ
Yang
Qing
Q
Feng
Li
L
Wang
Jian-wei
JW
D000293:Adolescent; D000328:Adult; D000818:Animals; D002648:Child; D002681:China / Q000453:epidemiology; D005260:Female; D006168:Guinea Pigs; D006801:Humans; D008297:Male; D051381:Rats; D012282:Rickettsia Infections / Q000453:epidemiology*; D012286:Rickettsia typhi / Q000302:isolation & purification*; D013987:Ticks / Q000382:microbiology*; D055815:Young Adult