Risk Mapping and Situational Analysis of Cutaneous Leishmaniasis in an Endemic Area of Central Iran: A GIS-Based Survey

Abstract

Introduction: Cutaneous leishmaniasis (CL) is among the top 10 infectious disease priorities in the world, and the leading cause of morbidity in Iran. The present study was conducted to assess the risk of CL, and to determine some epidemiological features of the disease in endemic areas of Qom Province in Central Iran during 2009 to 2013.

Methods: Data regarding human cases of the disease were obtained from the Qom Province Health Center, prepared and stored in a spatial database created in ArcGIS10.3. A total of 9 out of 212 Leishmania spp. positive slides taken in 2013 from patients residing in Qom city were examined using molecular methods and the species of Leishmania was identified by PCR-RFLP. Those 9 patients had no history of travel outside the city. Spatial analysis and clustering methods were applied to find major hot spots and susceptible areas for the establishment of novel foci of the disease. Transmission patterns were examined for spatial autocorrelation using the Moran's I statistical application, and for the clustering of high or low values using the Getis-Ord Gi* statistics.

Results: During the period of study, a total of 1767 CL cases were passively reported in the area, out of which were 65% males and 35% females. The highest and lowest numbers of cases were reported in 2010 and 2013, respectively. Importantly, 979 cases were reported from urban areas, while the remainder came from rural areas. Leishmania major was detected as the causative agent of CL in the city of Qom. Remarkably, most patients recorded in Qom city were associated with a history of travel to the endemic areas of CL within the province, or to other endemic areas of the disease in Iran. Spatial distribution of CL cases revealed northeastern and southwestern quarters of the city were the major hot spots of the disease (P<0.05). Hot spot and CL transmission risk analysis across the province indicated that more than 40 villages were located in high and very high risk areas of CL transmission.

Conclusions: Due to the existence of hot spots (P<0.05) of CL in successive years in some quarters of Qom city, along with detection of L. major from the patients without a history of travel, there may be potential of local transmission of the disease within the city. Therefore, it is necessary to conduct a comprehensive study concerning the hot spots of CL in Qom city for curtailing the incidence of the disease in the city. The methodology and the results of this study is essential in serving as a yardstick for subsequent similar studies that will be carried out in other endemic areas of CL in Iran and providing an adequate tool for the establishment of a national database of cutaneous leishmaniasis.

Fig 1. Qom Province in Iran.

Fig 2. Cutaneous leishmaniasis morbidity in different years, Qom Province of Iran.

Fig 3. Incidence of cutaneous leishmaniasis in different age groups, Qom Province of Iran, 2009–2013.

Fig 4. Temporal distribution of cutaneous leishmaniasis in different months of the year, Qom Province of Iran, 2009–2013.

Fig 5. Results of PCR test for species detection of Leishmania parasite isolated from human lesions, Qom Province, Central Iran.

(a): PCR product of Leishmania isolates from positive slides (Lanes 1–6); M: 100 bp size marker; (b): Electrophoresis of PCR products Leishmania species after endonuclease digestion with Hae III, Lanes 1–5: Leishmania major, NTC: negative test control, M: Marker (100bp).

Fig 6. Cumulative spatial distribution of CL incidence in different residential areas of Qom Province of Iran, 2009–2013.

Fig 7. The estimated incidence of CL across Qom Province of Iran, 2009–2013.

Fig 8. Hot spot clusters of CL in Qom City, Central Iran, 2009–2013.