[Tsutsugamushi disease found in the northern districts of Awaji Island--epidemiological study of the outbreak season temperature].
Ten cases of tsutsugamushi disease which were diagnosed and treated among the outpatients from 1987 through 1999 in a clinic of internal medicine locating at the northern districts of Awaji Island were investigated. The patients were consisted of 8 males and 2 females and their ages ranged from 6 to 69 years old. The infected areas were distributed in hilly districts extending over three towns. The outbreak season was from November through December. The following two facts seemed to be worthy of notice. 1) There was a time lag on the patient's onset among the different years. 2) When the incidences were more than two cases a year, the time difference of onset was within a few days each other. Then the relationship between atmospheric temperature and the date of onset was studied. Meterological observing records at Gunge Ichinomia Town near the northern districts of Awaji Island were investigated into the temperature every 10 days from 1987 to 1999. Average temperature every 10 days including the presumable day when each patient was infected with Orientia tsutsugamushi (O.T) ranged between 9.1 degrees C and 13.3 degrees C and in 7 of 10 cases ranged between 11.6 degrees C and 13.3 degrees C. The maximum temperature ranged between 11.3 degrees C and 17.5 degrees C, the minimum one between 6.6 degrees C and 9.1 degrees C. It is likely that the seasonal occurrence of tsutsugamushi disease greatly depends upon the optimum temperature for the activity of tsutsugamushi mites in these areas. The high titer of serum IgM and IgG antibody to Karp, Gilliam Kato type O. tsutsugamushi was detected by an immunofluorescense assay (IF) in all cases. IgG antibody, titers fell drastically to 20 or 10 times within a few years but 10 times titer was still detected in three cases in more than ten years. It is suggested that IgG antibody titer more than 10 times in healthy people indicates the infection in the past and titer more than 20 times implies the infection during the past few years.
Okada
Nagayasu
N
Okada Clinic of Internal Medicine.
D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D002648:Child; D004196:Disease Outbreaks; D016021:Epidemiologic Studies; D005260:Female; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012285:Orientia tsutsugamushi; D012612:Scrub Typhus / Q000453:epidemiology*; D012621:Seasons; D013696:Temperature