RELAPSING FEVER IN ARDABIL, A NORTHWESTERN PROVINCE OF IRAN

Background– The main area of Iran affected by relapsing fever (RF) is Ardabil Province, for which Borrelia persica is the most common cause in this country. The aim of this study was to determine the epidemiologic characteristics of the disease, and the frequency of infection among ticks in this region. Method– This clinical epidemiology and entomology study was performed on a total of 391 patients diagnosed with tickborne relapsing fever between 1998 to 2001. The presence of Borrelia with any species as well as the clinical characteristics were observed. Borrelia was identified in blood smears of 1,421 ticks collected from 130 indoor and 14 outdoor sites. The ticks were crushed and the suspension obtained was injected into the peritoneum of two mice and two guinea pigs to determine the frequency of infection among the ticks living in this region. Data including the tick species determination were collected through a questionnaire and analyzed using Chi-square and ANOVA tests. Results– The most prevalent clinical manifestations were fever, chills and headache. Other findings included nausea, vomiting, sweating, abdominal pain, arthralgia, cough, photophobia, eosinophilia, hematuria, jaundice, petechiae and scleral congestion. Laboratory tests performed on 60 patients showed leukocytosis, high erythrocyte sedimentation rate (ESR) and anemia. Of the 1,421 ticks collected, 45.9%, 40.3% and 13.8% were of the Ornithodoros lahorensisi, Ornithodoros tholozani and Argas persicus species, respectively. The prevalence of ticks was highest in Khandabil village. The ticks collected from three villages were found to be infected with Borrelia. Conclusion– This study is the first large-sized published report of tick-born RF until that time. The clinical manifestations were similar to those reported in other studies. Petechiae occurred less frequently in our study compared to louse-borne RF. The high frequency of anemia, which was not stated in most other reference articles, requires further investigation.