Serum antibody titer to Rickettsia Tsutsugamushi in Taiwan Rodeuts

1987 Vol.3 NO.8

Correspondence Author:


It has been well documented since long ago that tsutsugamushi disease has been endemic in certain parts of the Taiwan area1 Although the disease was officially announced as a reportable disease since 1955. only 71 cases have been reported for the past thirty years2 The present situation is rather ambiguous due to severe underreporting Our recent field investigation of tsutsugamushi disease. with full support of the local clinicians and health authorities, resealed 130 confirmed cases in Penghu in 1985. 2, 7 and 7 cases respectively in Ilan, Hwalien and Taitung Counties in 1986 All these cases were confirmed serologically by indirect immunofluorescent antibody test (IFA) Chigger mite is the sector of tsutsugamushi disease and rodents are one of its main host We undertook an island-wide field investigation of geographic and seasonal distribution of the mite and its host’s serum antibody titer to tsutsugamushi disease during the period from June 1985 to July 1986 The areas selected for study of geographic distribution of the mite were those townships and villages which had never been investigated to avoid duplication Fenglin. Juisui and Shoufeng townships in 1-Iwalien County were selected specifically for Investigation of seasonal distribution of the mite from July 1986 o April 1987 In both studies live traps were used to capture rodents Peanuts coated with butter were used as bait to increase attractiveness during the cool season, while plain peanuts were used during the hot season to avoid the disturbance of ants Participants in these studies consisted of three persons At 3 or 4 p m 30 live traps were set out in bushes closed to the animal tracks leading to, or right in front of their burrows in the peanut, sugar cane, maize (Indian corn), or sweet potatoes fields All traps were recollected early next day at 7 or 8 a m For study of seasonal distribution, trappings were undertaken at the same way as mentioned above except that all traps were set out and recollected at the fixed places as monthly routine The sera used for antibody titer test were from the blood taken from the heart of the animals captured A special shaped filter paper was smeared with the blood from the heart of animals and let dry naturally The results of the results of the studies Table 1) revealed that rodent capture rate as well as positive rate of serum antibody to R tsutsugamushi was higher in Rattus losea and Bandicota indica nemorivaga than in other rodents trapped on Taiwan It seems feasible to use these indices to show the endemic level of the disease in the area investigated Three areas with highest rate of positive serum antibody in the animals R losea plus B indica nemorivaga were noted in Taitung, Hwalien and Nantou Counties (Taichung County was excluded due to the fact that the number of rodents captured was too small to be significant) Taipei, Ilan and Tainan Counties had the second highest rates The rates for the remaining counties were very low R losea and B indica nemorivaga are absent in Penhu, an off-shore county which consist of many islands The county has been shown to be an endemic area of tsutsugamushi disease in many previous studies1 The titer of serum antibody to R tsutsugamushi in the species present in Penghu was rather high