The effect of geo-climatic determinants on the distribution of cutaneous leishmaniasis in a recently emerging focus in eastern Iran

Abstract

Background Cutaneous leishmaniasis (CL) has been reported in recent years in South Khorasan Province, a desert region of eastern Iran, where the main species is Leishmania tropica. Little is known of the influence of geography and climate on its distribution, and so this study was conducted to determine geo-climatic factors by using geographic information system. Methods The home addresses of patients with CL patients who were diagnosed and notified from 2009 to 2017 were retrieved from the provincial health center and registered on the village/town/city point layer. The effects of mean annual rainfall (MAR) and mean annual humidity (MAH), mean annual temperature (MAT), maximum annual temperature (MaxMAT), minimum annual temperature (MinMAT), mean annual number of high-velocity wind days (MAWD), mean annual frosty days (MAFD) and snowy days (MASD), elevation, soil type and land cover on CL distribution were examined. The geographical analysis was done using ArcMap software, and univariate and multivariate binary logistic regression were applied to determine the factors associated with CL. Results A total of 332 CL patients were identified: 197 (59.3%) male and 135 (40.7%) female. Their mean age was 29.3 ± 2.1 years, with age ranging from 10 months to 98 years. CL patients came from a total of 86 villages/towns/cities. By multivariate analysis, the independent factors associated with increased CL were urban setting (OR = 52.102), agricultural land cover (OR = 3.048), and MAWD (OR = 1.004). Elevation was a protective factor only in the univariate analysis (OR = 0.999). Soil type, MAH, MAT, MinMAT, MaxMAT, and MAFD did not influence CL distribution in eastern Iran. Conclusions The major risk zones for CL in eastern Iran were urban and agricultural areas with a higher number of windy days at lower altitudes. Control strategies to reduce human vector contact should be focused in these settings. Graphical abstract

Geographical and climatic risk factors of cutaneous leishmaniasis in the hyper-endemic focus of Bam County in southeast Iran

“…Various studies have confirmed that higher maximum temperature, lower rainfall, and lower relative humidity are effective factors in the geographic distribution of leishmaniasis, especially in semi-arid areas of central Iran (47, 49, 50). Also, in arid areas of eastern Iran and another focus in southeast Iran, mainly including semi-arid areas, lower rainfall increased the chance of disease (17,18). In the current study, higher temperatures, lower humidity, rainfall, and the lower number of frozen days had a positive effect on the occurrence of CL.…”

“…Urban settings are large residential areas including cities and large villages that are identified in the primary satellite images and then drawn as a part of the land cover maps. Different studies from various areas in Iran have shown a significant increase in the risk of leishmaniasis in large and more populated residential areas (17,18,30). The dominant type of CL in Bam County is ACL caused by L. tropica, which is known as urban leishmaniasis (8,31) The main vector of ACL in Bam County is Ph.…”

“…Salt land was found as another effective land cover that increases the chance of CL in the Bam County. There are a few studies that have investigated the effect of salt land on leishmaniasis though no association was found (17,42). Observation of the land cover map shows that CL was reported from parts of salt lands that were just nearby to agriculture areas while there is no infected place in other parts of salt lands especially in the eastern region of Bam County (Figure 3).…”

“…GIS is a powerful and efficient technology that has been used to investigate the spatial patterns of various public health problems, including parasitic diseases. Using spatial data and analyzing it can improve the health of society in a short time and be cost-effective (17)(18)(19). The epidemiology CL is related to interactions between the parasite, vector, host, and the environment.…”

Epidemiological Study and Reservoir Identification of Cutaneous Leishmaniasis From Ardestan in Isfahan, Iran (2015-2016)

“…In Iran, both types of CL, including wet or rural type (one-third of the provinces involved), were caused by L. major, and dry or urban type (all provinces involved) were caused by L. tropica. [10][11][12] The causes of the spread of CL are divided into five sections, including environmental, carrier-related, and reservoir-related factors and the lack of health education or community awareness. Currently, 10 million people in the world suffer from this disease.…”