INVESTIGATION ON THE VECTORS OF SCRUB TYPHUS IN THE FOCI OF SHANDONG PROVINCE.

Objective:In order to investigate the vectore of scrub typhus in Shandong province.Methods:Rodents were captured from May 1995 to April 2002,Observation of fluctuation of chigger mites and isolation of Orientia tsutsugamushi(Ot) therefrom were carried out.Results:A total of 15467 chigger mites,consisting of 6 species from two genera,were collected from 527 rodents(including 335 Apodemus(A.) agrarius,119 Cricetulus(C.) triton,6 C.barabensis,63 Rattus(R.) norvegicus,2 Crocidura(C.) suaveolens,2 Mus(M.) musculus) captured in Fei county,Jinan,Junan and zouping.Walchia(W.) pacifica was the most predominant in number,followed by leptotrombidium(L.) scutellare,L.linhuaikongense,L.palpale,L.taishanium,and W.fragilis.L.scutellare was present from September to December(the epidemic season of scrub typhus in Shandong) with a remarkable peak in November,whereas L.palpale occurred from October to April(the second year) with peak in December.L.linhuaikongense was found from May to November,with peak in August.W.pacifica appeared from April to December with peak in July.Ot was isolated from L.scutellare,L.palpale,L.linhuaikongense and W.pacifica.The main serotypes of Ot isolated from the chigger mites were of the Gilliam type,but Karp type also existed in L.linhuaikongense.Conclusion:L.scutellare is the most important vector whice caused the endemic of this disease in Shangdong province,and L.palpale,L.linhuaikongense and W.pacifica may serve as the vectors in this and L.palpale,L.linhuaikongense and W.pacifica may serve as the vestors in this area.