DHF Endemicity and Aedes aegypti Larvae Density Mapping in West Purwokerto Community Health Center’s Working Area in 2023

ABSTRACT


INTRODUCTION
Indonesia has the highest number of DHF cases in Southeast Asia.In 2022, the Directorate of Infectious Disease Prevention and Control of the Indonesian Ministry of Health recorded a total of 131,265 DHF cases with around 40% of them being children aged 0 to 14 years.Meanwhile, the number of deaths reached 1,135 cases with 73% occurring in children aged 0 to 14 years 1 .According to the gathered data, the Case Fatality Rate (CFR) is evident at 0,86%.
Banyumas Regency is one of the dengue endemic areas in Central Java with high number of annual cases 2 .West Purwokerto District ranked among the 27 subdistricts in Banyumas Regency for the number of DHF cases in 2022.The density of Aedes aegypti mosquitos, which are common in tropical and subtropical areas, influences the spread of dengue disease 3 .The density of mosquito larvae describes the population of Aedes aegypti mosquitoes in a region 4 .High mosquito populations have a high risk of dengue transmission 5 .
The density of mosquito larvae in an area is related to the performance of the larvae monitor (Wiggler Monitoring Officers) 6 .Wiggler Monitoring Officers interact directly with the community through periodic larvae monitoring activities, Eradication of Mosquito Nest (EMN), and providing communication, information, and education to the community.The larvae-free index indicator can be used to assess the success of EMN activities 7 .A larvae-free index value greater than 95% indicates that it is in the "good" category, while a value less than 95% indicates a high risk of transmitting and spreading DHF [8][9] .The larvaefree index value in the working area of the West Purwokerto Community Health Center is 96.9%, but there are many DHF cases.
Another factor that can be linked to DHF cases is environmental conditions 10 .Physical environmental conditions, such as rainfall, are closely associated with the breeding of Aedes aegypti 11 .Rainfall affects where mosquito larvae breed, which explains why DHF cases vary with the rainfall.Previous research conducted by Thessalonika Bone, Wulan P.J. Kaunang, and Fina L.F.G.Langi indicated a significant correlation between rainfall and dengue outbreaks 12 .
As part of the effort to identify DHF cases, it is necessary to analyze the factors that influence DHF cases.These factors are linked through the mapping of DHF cases using GIS.The objective of mapping DHF cases is to provide detailed spatial information about the distribution of DHF cases and their transmission models, as well as the factors that affect DHF cases, i.e., the density of Aedes aegypti larvae.In addition, an analysis of the relationship between DHF cases and rainfall in the West Purwokerto Community Health Center work area will be conducted using rainfall graph media.

MATERIALS AND METHODS
The research method employed was qualitative with an exploratory approach.This study was conducted to obtain an overview of DHF cases and the density of Aedes aegypti mosquito larvae through mapping designed with GIS modeling.The goal of exploratory research is to discover the connection to a problem 13 .Data analysis on two variables, e.g., DHF cases and Aedes aegypti mosquito larvae density; including Container Index (CI), House Index (HI), Breteau Index (BI), and larva-free index indicators, as well as DHF cases with Wiggler Monitoring Officers performance, was carried out by looking at the results of mapping performed with GIS applications.Then, using rainfall graph media, the relationship between DHF cases and rainfall in the West Purwokerto Community Health Center work area was examined.
With only 78 DHF cases in the West Purwokerto Community Health Center work area in 2022, the subjects of this study were mapping DHF cases.The density of mosquito larvae was measured in the homes of dengue patients and in homes within 100 meters of the patient's residence.Cadres of Wiggler Monitoring Officers were evaluated for performance in hamlets where DHF cases have been identified.

Result
This research was conducted in dengueendemic areas located in the working area of the West Purwokerto Community Health Center.DHF cases in the West Purwokerto Community Health Center's working area were 78 cases spread across 7 villages, e.g., Kedungwuluh, Kober, Pasir Muncang, Bantarsoka, Rejasari, Pasir Kidul, and Karanglewas Lor (Table 1).

Rainfall
Rainfall data is derived from secondary data sourced from the Banyumas Regency's Central Bureau of Statistics. Figure 1 shows a graph of the relationship between rainfall and DHF cases.
Rainfall is inversely linked to the number of DHF cases.Rainfall is low in April (265 mm) and May (255 mm), accompanied by an increase in cases.The highest number of DHF cases was in May (14 cases), indicating an increase from April.Light rainfall will, over time, create many puddles as breeding sites for mosquitoes, leading to an increase in the mosquito population and possibly an increase in the number of cases [14][15] .
Furthermore, the highest variation in rainfall occurred in October (810 mm), followed by a decrease in DHF cases from September.It can be due to washing away any of the remaining puddles of rainwater in September by rainfall that could be used as a breeding ground for mosquito larvae, causing mosquito larvae to die and fail to breed 16 .

The density of Aedes aegypti mosquito larvae
Examination of Aedes aegypti mosquito larvae was carried out at the home of dengue patients and a radius of 100 meters from the patient's house using visual methods or by seeing and recording the presence or absence of larvae in containers 17 .Container Index (CI), House Index (HI), and Breteau Index (BI) indicators were used to calculate mosquito larvae density.Furthermore, the value of the larvae-free index was measured as an indicator of Wiggler Monitoring Officer performance.
The results of measuring the density indicator of Aedes aegypti mosquito larvae in the working area of the West Purwokerto Community Health Center are displayed in Table 2.The measurement results revealed that 6 out of 7 villages had CI, HI, and BI values in the low categories and larvae-free index values more than 95%, e.g., Kedungwuluh, Kober, Pasir Muncang, Bantarsoka, Rejasari, Pasir Kidul, and Karanglewas Lor Villages.Meanwhile, Karanglewas Lor Village had a medium category and a larvae-free index value of less than 95%.

Spatial Analysis
The spatial analysis performed is a description of the results of maps produced by spatial data processing software in the form of ArcGIS applications.Secondary data obtained from West Purwokerto Community Health Center data in 2022 was used to collect DHF cases in the working area of the West Purwokerto Community Health Center in 2022.Then, coordinate points were taken at each dengue patient's house in all outputs located in the West Purwokerto Community Health Center work area.The obtained coordinate points were then entered into spatial data processing software in the form of ArcGIS applications.Meanwhile, the DHF cases transmission model is described using the Buffer feature.
The distribution of DHF cases can be seen in Figure 2, while the DHF cases transmission model can be seen in Figure 3.In both maps, DHF cases are represented by red dots, providing a visual depiction of the case distribution.The use of red dots as symbols enhances clarity and facilitates a quick understanding of the prevalence and potential pathways of DHF transmission.a. Distribution of DHF Cases  d.Larva-free Index Analysis of larvae-free index on DHF case was carried out by classifying larvae-free index data, which was divided into two, e.g., the value of larvae-free index ≥ 95% and the value of larvae-free index < 95%.The results of mapping larvae-free index values in the working area of the West Purwokerto Community Health Center can be seen in Figure 7. Wiggler Monitoring Officers cadre respondents' questionnaire scores were used to determine how well they handled DHF cases.Respondents came from every community that had dengue patients.There are two performance categories for Wiggler Monitoring Officers, e.g., good and poor.If the questionnaire score is greater than 80%, the category is good; otherwise, the category is bad. Figure 8 shows the Wiggler Monitoring Officers' performance map.

b. DHF Cases Transmission Model
Dengue case transmission can be classified into two types, e.g., cluster and separated.Cluster transmission are 100 meters away, while the separated transmission are further away18.The distance is based on the flight range of the Aedes aegypti mosquito, which is limited to 100 meters19.
In the data collected for this study, two transmission models were identified in the data collected for this study, e.g., a cluster model and a separated model (Figure 3).Dengue patients' radius is represented by two colors, i.e., light pink for a radius of 100 meters and light green for a radius of 200 meters.There are 15 distinct separate transmission models and 15 distinct cluster transmission models.A cluster transmission occurs within a specific area, whereas a separated transmission occurs over a distance greater than 100 metersTwo2,20.This is connected to the 100meter mosquito flight range and the time it takes for dengue fever to develop (incubation period)21.
Based on data obtained from the community health center, the first dengue case was reported in Pasir Muncang village on January 1, 2022; the second case was identified in Bantarsoka village on January 3, 2022; and the third case was reported in Kober village on January 4, 2022.All three cases occurred at distance greater than 100 meters.Thus, it can be concluded that the three cases are the first case index.Based on the mosquito's flight distance of 100 meters, it is possible to conclude that the three cases are exceeded the mosquito's flight ability.
The fourth case experienced symptoms on January 7, 2022.The patient was less than 100 meters away from the first case.As a result, the fourth case was considered as a secondary case or one that was transmitted from the first case.This is based on the DHF incubation period of seven days and the maximum flight distance of mosquitoes of 100 meters.These two cases are cluster transmissions located in Pasir Muncang village.
Furthermore, in the separated transmission model, dengue disease transmission over a distance of more than 100 meters.This relates to the flight distance of mosquitoes at most 100 meters.Transmission separately can come from several types of mosquitoes or other factors such as the patient being exposed outside the home area.According to research, many homes of dengue patients do not contain mosquito larvae and have clean, well-maintained environments, therefore the chance of the patient being bitten by mosquitoes outside the home environment is low.

c. The density of Aedes aegypti mosquito larvae
The density of Aedes aegypti mosquito larvae is depicted through maps that can be seen in Figure 4-6.It shows the category of indicators of the density of Aedes aegypti mosquito larvae.The indicators of mosquito larvae density measured are CI, HI, and BI which have direct relevance to the transmission of DHF cases22.Based on the map image, it can be seen that villages with low categories for CI, HI, and BI indicators have a large number of DHF cases, whereas villages with medium categories have the fewest DHF cases.
The results of measurements against CI, HI, and BI indicators can be used to determine the level of mosquito larvae density or density figure (DF), which indicates the level of transmission risk23.The DF level of the village with the green color is low, which means the risk of dengue transmission is low while the DF level of the village with yellow color is medium, which means the risk of dengue transmission is medium.
Karanglewas Lor village has a medium density of larvae because, according to research, people in Karanglewas Lor village do not keep the environment clean.Many used items, such as used bottles, were discovered scattered throughout the village.A dirty environment could potentially be a breeding ground for mosquito larvae24.Karanglewas Lor village is in the medium category, which may be due to calculation factors such as the small number of houses examined in comparison to other villages.Meanwhile, in villages with a high number of cases, the density of larvae is low because only a few containers and houses are positive for larvae, according to research findings.This is related to the fact that researcher discovered that the research was conducted at a time after the simultaneous EMN, therefore the houses of residents used as research subjects were still clean and no mosquito larvae were found.

d. Larva-free Index
The results of mapping larvae-free index values in the working area of the West Purwokerto Community Health Center can be seen in Figure 7.It shows a map of the distribution of DHF cases based on larvae-free index with two categories differentiated by color, green for the larvae-free index category ≥ 95% and red for the larvae-free index category < 95%.The study found that only one village, Karanglewas Lor village, had the larvae-free index category < 95%, and six other villages, Kedungwuluh, Kober, Pasir Muncang, Bantarsoka, Rejasari, and Pasir Kidul villages, had the larvae-free index category > 95%.
The larvae-free index value is high in each village because only a few houses found mosquito larvae out of the total number of houses inspected.Meanwhile, Karanglewas Lor village has a larvaefree index value of < 95% also due to the calculation factor where the houses examined are only neglible compared to other villages.The larvae-free index values below the 95% standard can be risky in accelerating the transmission of DHF cases25.A low larvae-free index value in an area indicates a lack of community participation in eradicating mosquito nests (EMN), allowing mosquito populations to grow and pose a high risk of dengue transmission26.
Before the larvae inspection, the community was informed that larvae inspection activities would be carried out so that residents could clean their homes, including draining the bathtub and cleaning the refrigerator water reservoir and dispenser.As a result, at the time of inspection, the larvae-free index value in six urban villages within the West Purwokerto Community Health Center's service area was greater than 95%.

e. Wiggler Monitoring Officers performance
Figure 8 shows a color-coded Wiggler Monitoring Officers performance map, with green representing good performance and red representing poor performance.From 7 sub-

Figure 2 .Figure 3 .Figure 4 .
Figure 2. Map of the distribution DHF cases in 2022 b.DHF Cases Transmission Model

Figure 6 .
Figure 6.Map of Breteau Index (BI) c.The density of Aedes aegypti mosquito larvae The measured indicators of the density of Aedes aegypti mosquito larvae are container index (CI), house index (HI), and breateau index (BI), which are depicted through maps that can be seen in Figure 4-6.It shows the category of indicators of the density of Aedes aegypti mosquito larvae in the working area of the West Purwokerto Community Health Center.The mosquito larvae density indicators category is distinguished by color, i.e., green for the low category and yellow for the medium category.The category of Karanglewas Lor village is medium, whereas six other villages, namely Kedungwuluh, Kober, Pasir Muncang, Bantarsoka, Rejasari, and Pasir Kidul, are low.

Figure 7 .
Figure 7. Map of larvae-free index e.Wiggler Monitoring Officers performance Wiggler Monitoring Officers cadre respondents' questionnaire scores were used to determine how well

Figure 8 .
Figure 8. Map of Wiggler Monitoring Officers performance Discussion a. Distribution of DHF Cases Figure 2 shows the distribution of DHF cases in 2022 in the working area of the West Purwokerto Community Health Center.DHF patients are indicated by red dots scattered in each village.It was found that Kober Village had the most dengue patients with 18 cases, while Karanglewas Lor Village had the fewest dengue patients with 2 cases.

Table 1 .
Number of DHF Cases

Table 2 .
Results of measuring the density of Aedes aegypti mosquito larvae

relation between rainfall and DHF cases
Rainfall of West Purwokerto District DHF Cases hamlet in the West Purwokerto Community Health Center's service area where dengue fever cases had been reported.The percentage of Wiggler Monitoring Officers' performance questionnaire responses in each village is shown in Table 3.According to the study's findings, only three of seven urban villages had good Wiggler Monitoring Officers performance.With a questionnaire score of 96.7%, Bantarsoka Village has the best Wiggler Monitoring Officers performance.Meanwhile, Kober Village has the lowest Wiggler Monitoring Officer performance with a questionnaire score of 70%.

Table 3 .
Percentage of Wiggler Monitoring Officers performance questionnaire results