The Epidemiology and Confirmation of Diagnosis of Scrub Typhus in Prachuap Khiri Khan Province

Abstract

   The survey was carried out to evaluate the situation and prevalence of scrub typhus case by comparing between clinical diagnosis and laboratory confirmation and the infection rate of reservoir animals and type of vector. The study selected 100 cases from the patients undergoing clinical diagnosis in Prachuap Khiri Khan province during February 2002 - August 2003. Primarily, the laboratory results as confimed by IFA (Indirect Immunofluorescent Antibody) technique reported 16 percent scrub typhus and 1 percent murine typhus. In the follow up 1-2 weeks later, only 14 out of 77 patients were positive for scrub typhus using IFA (IgM) technique. The epidemiological data showed that more females were infected than males in a ratio of 1.2:1. The infection rates as confirmed by immunological investigation of females and males were 19.0 percent and 17.1 percent respectively, showing the peaks in the age group of 45-59 years. Most of their occupations were in agriculture and laborers. The main clinical symptoms were acute fever, headache and myalgia. No
eschar could be found in any cases. The reservoir animals survey indicated that the trap success rate was 14.05 percent in 6 areas and 34 rats were trapped. As such, 52.9 percent were Rattus rattus, 29.4 percent Tupaia glis, 8.8 percent Rattus exulans and 8.8 percent Menetes berdmorei. The chigger infested rate was 73.5 percent. Of the 1,644 mites collected 82.9 percent were scoschoengastia indica, 11.7 percent Leptotrombidium delienses, 1.1 percent Sacoptes scabiei and 0.3 percent tropical rat mite. The infection rate in reservoir of Bang Saphan area was 50 percent. This paper indicates that the diagnosis of scrub typhus infection should be supported by laboratory investigation as
symptoms alone are common to those of other disorders. Health education should be provided to high risk groups, as identified by their occupations or vicinities.

Key words: Scrub typhus, epidemiology, diagnosis reservoir and vector