Visceral leishmaniasis (VL) is a fatal disease caused by sandfly-borne protozoa of the Leishmania genus. This study explored the influence of environmental factors on the distribution of VL in Sinkiang province, Mainland China, which is a known natural focus of leishmaniasis. Disease identification records were obtained from publicly available data, in which the existence of VL at each geographical location had been recorded as part of the surveillance of leishmaniasis in Sinkiang province. Maximum entropy modelling (Maxent) was used to predict the distribution of VL across Sinkiang province, and to match this distribution against environmental variables relating to elevation, climate and land cover, obtained from the WorldClim database, China Meteorological Data Sharing System and the National Geomatic Center of China dataset, respectively. Finally, a regional-scale map was developed to show the potential distribution of VL in the Sinkiang province. Receiver-Operating characteristic (ROC) analysis was used to evaluate the performance of the model. The daily average temperature, maximum temperature of the warmest quarter, daily precipitation and precipitation of the driest month were each found to be predictive of the distribution of VL in Sinkiang. Moreover, we found that presence of VL was significantly influenced by the distribution of grassland and shrubland. The results demonstrate that with proper construction and design, probability surfaces using Maxent can be used as an accurate method by which to predict the distribution of VL in Sinkiang province. The information generated by the model could be used to inform the design of detailed prevention and control strategies for leishmaniasis in this region of Mainland China.

Introduction

Visceral leishmaniasis (VL), which is caused by Leishmania genus, is a fatal global disease. Every year, approximately 200,000 to 400,000 VL cases occur in the world, which result in 20,000 to 40,000 deaths per year (Alvar et al., 2012; WHO, 2010). Due to the expenses incurred in treating the disease, as well as the interruption to development programmes that results from disease outbreaks, VL is also associated with the propagation of poverty (Alvar et al., 2006; Cortes et al., 2012). Moreover, because there is an overlap in the distribution of leishmaniasis and human immunodeficiency virus (HIV), there has been an emergence of Leishmania/HIV co-infection (Desjeux, 2004). Because this background, leishmaniasis is ranked 9th in the list of global infectious disease and constitutes a serious global public health risk (Dilger, 2013). VL was a very prevalent infectious disease in Mainland China before the 1950s. Only in 1951, N530,000 VL cases have been reported in this region (Wang et al., 2012). However, as a result of a major national control program, the disease has now effectively been controlled in the east and southeast China (Lun et al., 2015). In the northwest of Mainland China, including Sinkiang province, the disease is still endemic. Previous research has clearly demonstrated that Sinkiang province is a natural focus of VL (Wang et al., 2011).