Spatial Analysis of Environmental Conditions in The Incidence of Leptospirosis in Kebumen Regency

Background: Kebumen Regency recorded 23 cases of leptospirosis in 2021 and 37 cases of leptospirosis in 2022 until August. One of the efforts to overcome and prevent disease is the environment-based spatial disease. GIS


INTRODUCTION
Leptospirosis is a zoonotic disease that has become a health problem in the global scope, especially in areas with poor sanitation and infrastructure. 1 This disease is caused by bacterial microorganisms of the genus Leptospira. Currently, the genus Leptospira has two species, namely, at least 12 species are pathogenic and 4 species are saprophytes, which have more than 250 pathogenic serovars. 2 The disease has caused cases of more than 1 million people and found at least 58,000 deaths each year in parts of the world. 3 The incidence of leptospirosis found in subtropical countries is around 0.1-1 per 100,000 inhabitants per year, while in tropical countries it is around 10-100 per 100,000 inhabitants per year. 4 The prevalence of leptospirosis in Indonesia tends to increase with case mortality rates ranging from 5 to 12%. 5 The main transmission of leptospirosis, especially in Indonesia, is through rats. Some species of rats that are reservoirs of leptospirosis in Indonesia include Rattus tanezumi, Rattus norvegicus, Bandicota indica, Rattus exculan, Mus musculus and Suncus murinus. 6 Transmission of Leptospira to humans occurs directly due to exposure to fluid or urine of reservoir animals or indirectly through the medium of water, soil, and plants that have been contaminated with Leptospira. 7.8 Humans infected with leptospirosis will experience clinical symptoms such as acute fever, jaundice, or functional dysfunction of several organs of the body. 9 Leptospira bacteria enter the human body through wounds present on the skin, mucous membranes (nose, mouth, and eyes), or even through drinking water. Leptospira bacteria that have entered the human body will be in the blood and attack the body's tissues and organs. 6 The incidence of leptospirosis in Kebumen Regency was first reported in 2015 as 1 case with 1 death. Leptospirosis cases were not found in 2016. The incidence of leptospirosis in Kebumen Regency has increased cases of leptospirosis where 87 cases were found with 10 deaths in 2017. Furthermore, the Kebumen District Health Office re-reported the findings of cases, namely 9 cases with 1 death in 2018, 2 cases with 2 deaths in 2019 and in 2020 no reported cases of leptospirosis. The Kebumen District Health Office again reported the findings of leptospirosis cases of as many as 23 cases with 9 deaths in 2021 and further rediscovered leptospirosis cases of as many as 37 cases with 7 deaths in 2022 until August. The emergence of leptospirosis in an area can be influenced by environmental factors, habits, work, and the presence of a source of transmission. 10 The environmental factors that affect leptospirosis include the presence of rats, the presence of farm animals, a history of contact with floods, poor sanitary conditions, and the presence of poor trash cans. 11,12 One descriptive approach in planning disease management and prevention programs is environmental-based disease spatial. Spatial analysis in epidemiology is useful for evaluating the occurrence of differences in events by geographic area and identifying disease clustering. 13 Spatial analysis using Geographic Information Systems (GIS) is one of the important methods in disease surveillance. The ability of GIS to compile data into layers commonly called "overlays" can provide benefits in disease surveillance. 14 GIS is used to improve health surveillance systems that can visualize diseases in time and space with output in the form of maps. 15 GIS in the form of mapping can make it easier for health workers to see disease distribution patterns and risk factors. 16 Based on the description above, the purpose of this study is to determine the distribution of leptospirosis cases and conduct a spatial analysis of environmental factors for the incidence of leptospirosis in Kebumen Regency in the form of land use, © 2023, JKLI, ISSN: 1412-4939e-ISSN: 2502-7085. All rights reserved. population density, altitude, and flood history. The results of this study are expected to provide benefits for policymakers and leptospirosis program managers in Kebumen Regency in carrying out problem-solving and appropriate leptospirosis interventions in an area.

MATERIALS AND METHODS
This type of research is analytical observational and the research design is cross-sectional using spatial analysis. This research has been submitted to obtain ethical approval from the Health Research Ethics Commission (KEPK) of the Faculty of Public Health, Diponegoro University, namely No: 346 / EA / KEPK-FKM / 2022. Data collection is carried out for approximately 2 months from September 1 to October 22, 2022. The study is all leptospirosis cases recorded in the Kebumen Regency Health, Population Control, and Family Planning Office as many as 60 cases consisting of 23 cases in 2021 and 37 cases in 2022 until August. However, based on inclusion and exclusion, the total research sample was 56 cases. The inclusion criteria are leptospirosis sufferers who were found and recorded at the Kebumen Regency Health, Population Control, and Family Planning Office in 2021 and 2022 until August while the exclusion criteria were patients who had moved their homes outside Kebumen Regency and had been visited 3 times but were not successfully interviewed.
Primary data in the form of measurement of coordinate points from the case house using the Garmin Monterra brand GPS (Global Positioning System) tool and characteristic data of respondents of leptospirosis cases by interviewing cases or families of cases. Secondary data was obtained from the Health, Population Control, and Family Office of Kebumen Regency as well as the local community health center (Puskesmas) in the form of case data and address data for leptospirosis cases, the Regional Disaster Management Agency (BPBD) in the form of flood data, the Central Statistics Agency (BPS) in the form of population density data, the Regional Development Planning Agency (Bappeda) in the form of administrative data for Kebumen Regency, land use data, and regional topographic data.
Spatial data analysis in this study used ArcGIS 10.3 and SaTScan 10.1 software. The data analysis carried out was based on overlay, buffering, and clustering analysis. Overlay analysis aims to determine the spread of leptospirosis based on data on land use, population density, altitude, and flood history. The buffering analysis aims to determine the spread of leptospirosis with spatial elements so that a certain distance area will be formed. Elements used in the buffering analysis include rivers and rice fields. Clustering analysis was performed with SaTScan 10.1 software to determine which clusters occurred using the Space-Time Permutation model method. This analysis aims to describe a significant pattern of grouping leptospirosis cases in Kebumen Regency with an aggregate time of one month.
The results showed that leptospirosis sufferers were mostly aged between 50-59 years (32.14%) with the average age of cases being 43 years. The majority of leptospirosis cases are suffered by men (83.93%) compared to women (16.07%). Education from leptospirosis cases is mostly lower education (48.21%) and secondary to upper education (46.43%). The majority of leptospirosis cases work as farmers (66.07%) followed by self-employed (10.71%). More can be seen at Table 1. The results of the overlay analysis of the leptospirosis case map with a population density map obtained results that leptospirosis cases were spread in areas with low population density (417-1025 people/km 2 ) of 54% and high population density (1154-3145 people/km 2 ) of 46% (Figure 1b). Figure  1c shows that leptospirosis cases occur in areas with land use in the form of village settlements surrounded by rice fields, yards, and gardens (80.36%). Figure 1d shows that most of the leptospirosis cases are at an Buffering analyses to be linked to leptospirosis cases in this study are rivers and rice fields. In figure  2a, the results of case buffering analysis with rivers show that leptospirosis cases in Kebumen Regency were found in a river radius of 0-1 km as many as 24 cases (42.86%) and > 1 km as many as 32 cases (57.14%). In figure 2b the results of the buffer analysis of the distance of leptospirosis cases with the presence of rice fields show that in a radius of up to 500 m with rice fields found 87.5% of cases were and in a radius of 500-1000 m found 12.5% of cases.   The results of clustering analysis using Satscan with an aggregate time of one month in leptospirosis cases from 2021 to August 2022 showed that there were six clusters of leptospirosis infection sources as shown in Table 2 below.

Table1. Distribution of leptospirosis case frequency in 2021-August 2022 in Kebumen Regency
Based on the results of the satscan analysis, it shows that there is one significant meaningful cluster (p-value = 0.0015) which occurred on March 8, 2021 -May 7, 2021, located in Mirit District, Wirogaten Village with a coordinate center (109.766850 E, 7.776667 S) with a radius of 10.59 km. Meanwhile, the other five clusters formed are not significantly meaningful (Figure 3).
The incidence of leptospirosis in Kebumen Regency from 2021 until August 2022 spread in 20 districts from 26 districts. This is possible because the condition of the Kebumen Regency area, which has many rice fields, gardens, and settlements, is very supportive of rat habitat. According to Joharina's research, in 2019 the percentage of Leptospira-positive rats was found in many residential habitats, rice fields, and gardens. 17 In addition, leptospirosis cases in Kebumen Regency are dominated by farmer workers because when doing activities in environments such as rice fields and gardens, they often do not wear footwear so that Leptospira bacteria have the potential to enter the body. 18 This result is following research in Banyumas which states that in leptospirosis cases as many as 62.1% are men and the majority worked as farmers (40%). 19 Overlay results on population density in Kebumen Regency show that leptospirosis cases tend to be found more in low-population density areas. In addition, the results of overlays with land use show that the majority of leptospirosis cases occur in village settlement areas that are surrounded by rice fields, yards, and gardens. The land use map obtained from the Regional Development Planning Agency (Bappeda) is the result of satellite imagery in 2017. Rural areas where there is a lot of agricultural land, yards, and plantations in Kebumen Regency, especially in areas with low population density, will be the optimal place for rat breeding. This result is following Nurbeti's research, 2016 which states that the most cases of leptospirosis are not found in areas with the highest population density. 20 These results are different from studies in Banyumas and Semarang that leptospirosis cases occur in areas with moderate to high densities where there are many residential areas. 19.21 These results show that the transmission of leptospirosis is not only in densely populated settlements such as urban areas, but can also occur in rural areas where there are many agricultural areas such as rice fields, gardens, mangroves, and forests. 17 The results of overlaying leptospirosis cases with altitudes in Kebumen Regency show that many cases are found at altitudes of 0-100 meters above sea level. Low-lying areas tend to cause a lot of waterlogging and flooding, especially when the rainy season arrives. The existence of standing water has the potential to be a source of indirect transmission to humans if it has been contaminated by rat urine containing Leptospira bacteria. The results of this study are in line with several other studies such as in the provinces of South Sumatra, Sampang, and Demak which show that cases of leptospirosis or mice that are positive for Leptospira are found in areas with an altitude of <100 meters above sea level. [22][23][24] The results of studies in Pati Regency showed that rats were widely caught in low-lying areas. 25 Studies state that the altitude of a place ≤100 meters above sea level has a 2.3 times higher risk of being infected with Leptospira compared to an altitude of 101-600 meters above sea level. 26 The results of the overlay of cases and flood history in Kebumen Regency show that the majority of leptospirosis cases occur in flooded areas. Flood conditions will make rat nests waterlogged so that rats will come out of hiding places and move to human settlement environments where this is a chance of developing a risk of leptospirosis transmission due to contact with rats. After the flood, there will be a lot of puddles that have not receded, mud, or muddy soil so it can be a risk factor for humans to be exposed to water and soil that has contained Leptospira bacteria. 27 These results are in line with research in Karangtengah District, Demak which shows that as many as 61% of cases occur in areas that have experienced floods. 28 The presence of contact with flooding is a significant factor in the occurrence of leptospirosis (OR: 2.19, 95% CI: 1.48-3.24, I 2:86%). 12 Cases of leptospirosis in Kebumen Regency are widely found to be related to the presence of rivers. The existence of rivers is one of the risk factors for the occurrence of leptospirosis, rivers can be a medium of indirect transmission of Leptospira. 29 Rivers in Kebumen Regency in some places found garbage scattered on the banks of the river so that potentially rats forage for food so it is feared that the river is polluted by rat urine containing Leptospira. Some studies state that the influence of the distance between the river and the residents' homes can be a risk factor for leptospirosis. Research in the Gajahmungkur Subdistrict area of Semarang City stated that many cases of Leptospirosis were found in a river buffer radius of 50-300 meters. Areas adjacent to the river have the potential to be exposed to river overflows due to flooding during the rainy season where the river water may have been infected with Leptospira. 30 Another study in Malaysia stated that as many as 90.2% of leptospirosis cases were found to be 3 kilometers away from the river. 31 Cases of leptospirosis in Kebumen Regency are also found in a radius of up to 500 m with rice fields. These results are following research in Banyumas Regency, all cases of leptospirosis were found at a distance of 0-1 km from rice fields. 32 Kebumen Regency area has found many rice fields so it has the potential to become a place of transmission. According to BPS data in 2021, it was recorded that land use for rice fields amounted to 31.30% of the total land. Rice © 2023, JKLI, ISSN: 1412-4939e-ISSN: 2502-7085. All rights reserved.
fields are a suitable place for rats to get the availability of feed so it becomes one of the habitats preferred by rats. Mice in search of food can explore up to a radius of 1-2 km. In this study, many cases were found at a radius of 0-1 km from the rice fields so that they still corresponded to the home range of rats. This of course risks the transmission of leptospirosis in rice fields. Mice in their foraging range will secrete urine that potentially contains Leptospira along the way. The existence of rice fields can be a means of transmitting Leptospira bacteria indirectly. The existence of transmission through rice fields is related to the activities of residents in Kebumen Regency, most of whom work as farmers and do not wear PPE when working in the rice fields. 29 The results of the Satscan analysis obtained 6 (six) groupings of sources of infection. The cluster radius formed from the results of the satscan analysis is the radius of the risk of transmission. 14 Significant cluster locations are in Wirogaten Village. This shows that there is transmission in the village so if there are sufferers in the village, people who live up to a radius of 10.59 km have the potential to have a risk of contracting leptospirosis. The results of the Satscan analysis were used to see the grouping pattern of the source of leptospirosis infection. The existence of a strong and significant cluster grouping indicates the suspected spread of mice and Leptospira bacteria in the cluster so that it has the potential to be a source of leptospirosis infection and has a high risk in the population living in the area. 33 The existence of strong and significant clusters identified in this study can be used by health policymakers to carry out integrated control, prevention, and health promotion activities in the area to break the chain of transmission of leptospirosis.

CONCLUSIONS AND SUGGESTIONS
The incidence of leptospirosis in Kebumen Regency is spread across 20 districts with the most cases in Kutowinangun and Rowokele districts. Characteristic cases of leptospirosis occur most at the age of 50-59 years, male sex, poorly educated, and working as farmers. The results of spatial analysis of environmental conditions show that the incidence of leptospirosis at the study site is mostly found in areas with low population density (417-1025 people/km 2 ), altitudes of 0-100 meters above sea level, flood history, land use in the form of village settlements surrounded by rice fields, yards, and gardens, the distance of houses to rivers > 1 km and the distance of houses to the rice fields < 500 m. A cluster of significant cases suspected to be the source of leptospirosis transmission is in Mirit District. The results of this study can be information for health policymakers to carry out integrated control, prevention, and health promotion activities in Kebumen Regency, especially in areas that are suspected to be clusters of sources of transmission.