Darioush Emdadi MSc*, Mohammad Hossein Derakhshan MD***

The aim of this study was to determine the epidemiologic and clinical characteristics of RF in Ardabil Province during the last 4 years, as well as the frequency and infection rate of Ornithodoros in Khalkhal district, the main disease area in Ardabil Province.

We made an assumption that Borrelia was very prevalent in Khalkhal, thus chose this city and its villages for entomologic study. Thirteen villages (10% of all villages of Khalkhal) were randomly selected and specimens collected from indoor sites. One of the villages was selected at random and specimens were collected from outdoor areas and animal shelters. There were five designated areas in each village (North, South, East, West, and Center) and the specimens were collected from one human residence and one animal shelter within a specified hour. For outdoor sampling, two active rodent nests were targeted.

All ticks were transferred alive to the parasitology laboratory of the Pasteur Institute, Tehran, Iran. They were subsequently crushed and suspension was prepared by standard methods and each one injected into the peritoneum of two white mice and two guinea pigs, simultaneously. Peripheral blood smears were then prepared at regular intervals and examined for presence of Borrelia under light microscopy.⁵

A complete blood count was also done for 60 patients, which showed leukocytosis with a WBC count more than 10,000 in 43% and a WBC count less than 7000 in 20.7% of cases. The mean WBC count was 10,000 ± 3100 (neutrophils 74.9% ± 11.3%, Lymphocytes 23.1% ± 10.6% and eosinophils 0.8% ± 1.7%). Regardless of sex, hemoglobin level was less than 11mg/dL in 34% of cases and MCHC was 32.5 ± 1.8. Erythrocyte sedimentation rate was more than 40 mm in the first hour in 35 of 40 patients.

Table 1. Comparison of clinical manifestations in different patient groups.

These findings were based solely on entomologic studies performed in the Khalkhal district, where 60 % of all cases of RF occurred.

Table 2. Relative frequency of soft ticks in the village colonies of Khalkhal

Ornithodoros were found in 13 villages in Khalkhal. Among the 130 indoor sites studied, 1,421 ticks of the Argasidae family (soft ticks) were collected and identified. Of these, 45.9 %, 40.3 % and 13.8% were of O. lahorensis, O. tholozani and Argas persicus. Soft ticks were not found in 14 rodent nests.

Out of the 1,421 ticks collected, only 54 (48 O. lahorensis and six O. tholozani) were collected from human residences and the remainder were collected from animal shelters. O. lahorensis and O. tholozani were more prevalent in mountain areas whereas A. persicus, which is usually more common in the villages, was more common in non-mountainous areas. Soft ticks were more prevalent in indoor sites in West Khanehbil, with a prevalence of nearly 16 % (Table 2). The ticks collected from three villages in Khalkhal, namely Tazranaq (22 %), Khojin (12 %), and Biraq (9 %) were found to be infected with Borrelia.

In this study, almost 90 % of the patients did not work outdoors and were comprised of children, housewives and students. It was not uncommon to keep cattle and sheep near or inside their homes. Our findings show that RF occurs more frequently in indoor areas rather than outdoors, which correlates with the findings of Abidov et al, who studied RF in Uzbekistan.⁶ As the Otholozani tick is rarely found in human residences, transmission of infection probably occurs through family contact. Most studies, including that of Vasil’eva, et al.⁷ state that the most important risk factor involved in the transmission of infection is the close proximity of human residences and animal shelters.

Table 3. Comparison of clinical manifestations of relapsing fever in four different studies.

Most cases of RF reported from endemic regions, were caused by an overnight stay in wooden shelters or inns in mountainous areas, or by traveling to endemic areas.^8,9 In our study, 16 patients who came from non-endemic areas (especially from Tehran) had become infected after traveling to endemic areas. As this figure only refers to those diagnosed with RF in the clinics or hospitals of Ardabil Province, we would expect the actual number of patients to be more. Hence, a patient with fever who has returned from an endemic region should be assumed to have RF.

Most cases of RF diagnosed in Ardabil Province were from Khalkhal, Kowsar and Nir districts. The prevalence was highest in Khandabil village (Table 2). However, the study performed by the Pasteur Institute of Iran in 1976 showed that RF was most prevalent in the village of Koraim (a county of Nir). In our study, although weak diagnostic tests were used, 38% of the patients who presented with fever finally developed RF.¹⁰ RF had not been reported in the cities of Namin, Meshkin Shahr, Bileh Savar and Parsabad. Malaria and lyme disease are the most common afflictions to be considered in the differential diagnosis of RF. As stated in some articles, RF is rarely considered in the differential diagnosis of fever and chills in areas where malaria is the main health problem.^11,12 As malaria is highly prevalent in the cities of Parsabad and Bileh Savar, RF should be considered in the differential diagnosis of fever and chills in patients of these areas.

The majority of cases in our study were children, which is similar to the finding of Barclay and Coulter on tickborne RF in Tanzania.¹² However, the mean age of the infected children in their study was lower than ours: 88% of their patients were less than 5 years of age compared to 33% of the patients in our study.¹ Although differences between the population distribution pyramid of Iran and Tanzania may explain these findings, it does not fully explain the differences. In Barclay and Coulter's study, 36% of the cases were infants, whereas there were no infants in our study. Other differences may be due to numberous causes, including: the type of spirochete, genetic factors, entomologic factors, underdiagnosis of the infection in newborns, different methods of infant care, and management of fever by healthcare personnel.¹³ Some articles have reported vertical transmission as a possible route of acquiring the infection in newborns.^14,15 The most common clinical manifestations of RF in the present study were fever, chills and headache which is similar to other studies performed in this field. We found no studies on the symptoms of tickborne RF. The signs and symptoms of RF in our study can be compared with those of louseborne RF in the study by Borgnolo et al during the epidemic outbreak of RF in Ethiopia,^16,17 another study by Brongolo on 103 children hospitalized in an Italian hospital in Ethiopia,^16,17 and a study performed by Brown et al (Table 3).¹⁸ Compared to the other studies, the incidence of petechiae in our study was very low (2.8% vs. 34%). This difference could be explained by the type of RF; for example, thrombocytopenia is a common finding in louseborne rather than in tickborne RF. Coughing, photophobia, sweating and hematuria were not indicated in the other studies. Considering the methodologic and statistical limitations of our study in identifying differences between the clinical manifestations of RF in those residing, or those visiting, the high prevalence area and the higher incidence of chills in females, the probable causes of these differences are not discussed here.

Leukocytosis is not an unexpected finding in RF and has been mentioned in many studies, including ours. Although anemia occurred in a large number of patients with RF, we are unable to provide possible explanations for this as there was no control group or randomization and, most importantly, anemia is common in Iran.

Although only 40 consecutive patients were assessed for ESR in our study, the mean values were higher than the normal range. With the exception of Dr. Karimi’s report,¹⁰ other studies and most textbooks do not mention high ESR values in RF. We suggest further research on tickborne RF based on laboratory findings. Due to the high prevalence of RF in Ardabil, further studies should be performed in this region.