Serum epidemiological investigation of F1 antibody of population having healed from plague in Yunnan Province / 中国地方病学杂志

ABSTRACT

Objective To provide theoretical and scientific evidences for plague control,through understanding the F1 antibody level distribution and affected factor of population having healed from plague from plague natural focus of Rat.flavipectus in Yunnan Province.Methods The places and population investigated were chosen according to plague surveillant data in Yunnan Province from 1986 to 2005,using caso-control study and quesfionary. All samples were detected by indirect hemagghtination(IHA),including 248 serum samples from population having heaIed from phsue in 23 counties as case group.295 senlm samples from healthy population inoculated with EV vaccine in 7 counties as artificial immunization group, and 235 serum samples from healthy population not inoculated it in a non-plagued foei county as negative comparison group,with the diagnosing standard for positive titor being not less than 120.Results(①The difference WSS statistically significant(X2=44.80,P<0.05)between plague and non-plagued foci with F1 antibody positive rates being 22.10%(120/543)and 0(0/235),respectively.② The F1 antibodv positive rate of case group,35.89%(89/248)and geometric mean titer(GMT)184,was higher than that of artiIicial immunization group,which was 10.51%(31/295)and with GMT 134,respectively,the difference being statistically significant(X2=50.41,P<0.0125);the positive rate of case group wgs hisher than the neganve comparison group,the difference being statistically significant(X2=103.39,P<0.0125)the posifive mte of artificial immunization group was higher than the negative comparison group,the difference being statisticallv significant(X2=26.23,P<0.0125).③The differences were not statistically significant in the F1 antibedy positive rates of case group for age,sex,nation and occupation(X2=1.88,2.01,5.46,0.04,P>0.05).④The difference was not statistically significant in 89 plague patients with positive F1 antibody at the time of onset and rehabilitation(t= 1.23,P>0.05).Conclusions ①Plague FI antibody in people distributes the sanle a8 the plague natural focus of Rat.flavipectus does in Yunnan Province.②For naturally infected plague patients,only 1/3 popuhtion get long- term immunity,and still 2/3 can be infected again.The protecting rate and effect of naturally acquired immunity due to infection of plague are better than amfieially acquired immunity from inoculation of EV vaccine.③For the population having healed from plague,the positive rotes of FI antibody are not affected by age,sex,nation and occupation,however for those whose plague F1 antibody is still positive after some time,the titer will remain or even increase.