Distribution and The Habitat Characteristics of Anopheles vagus (Diptera: Culicidae) Larvae at Paddy Fields in The Vicinity of Dramaga IPB University Campus Dramaga Bogor West Java

Dramaga sub-district is an area that has rice fields close to buffalo stalls and a population of wild Macaca fascicularis as natural hosts for several species of Plasmodium. This causes the Dramaga sub-district to become a potential vector habitat for malaria, including Anopheles vagus. This study aims to analyze distribution of An. vagus larval stage in 4 villages (Cikarawang, Babakan, Margajaya, and Ciherang) in Dramaga subdistrict which have paddy field areas. Larvae were collected using a dipper, and each collection sites of the larvae habitat were marked using Global Positioning System. The physical characteristics of the water habitat measured were temperature, pH, total dissolved solids and the electrical conductivity of the water. Pearson's correlation test was used to analyze the relationship between the number of larvae An. vagus with each of the parameters water physical characteristics. The results of this study obtained 309 An. vagus larvae from the 27 collection points. Larvae of An. vagus was found in 3 villages (i.e. Cikarawang, Babakan and Ciherang), but was not found in Margajaya village. The habitat characteristics of An. vagus in paddy fields showed a water temperature of 26.631.7C, pH 6.40-8.10, the total dissolved solid 36-285 ppm, and the electrical conductivity 72-262 μm/cm. The Pearsons correlation test results did not show a significant difference between the number of An. vagus larvae and each parameter (r= -0.26, 0.13, -0.15 and -0.16, respectively). The presence of An. vagus in this area could be considered in malaria vector control programs.


INTRODUCTION
Malaria is a vector-borne disease caused by parasites from the genus Plasmodium that can infect a wide variety of animals including humans. The transmission of malaria is mediated by the Anopheles mosquito as a vector. The variety of Anopheles species in Indonesia is quite high, namely around 81 species and 25 of them have been proven to be malaria vectors (Ministry of Health 2015). This vector is distributed throughout the region in Indonesia and each region has different species, bioecology, habitat, distribution and density. The existence and survival of Anopheles larvae are strongly influenced by the conditions of their breeding sites such as the physical characteristics of water.
The villages around the Dramaga IPB campus are residence for students, teaching staffs, education personnel and other academicians as well as the natives of Dramaga District. IPB students are very unique because they come from various regions in Indonesia, including from malaria endemic areas. Barodji (1980) and Andiyatu (2005) conducted research on the species diversity of mosquitoes in the villages surrounding the Dramaga IPB campus including rice fields. Both of them reported several genus of Anopheles mosquitoes including Anopheles vagus. The rice fields around the Dramaga IPB campus are also close to animal sheds such as buffalo, cow, goat, and also wild Macaca fascicularis habitats as natural hosts for various species of Plasmodium.
The existence of An. vagus needs serious attention as a potential vector of malaria. Wigati et al. (2006) reported An. vagus originating from Hargorejo Village, Kokap District, Kulon Progo Regency has been confirmed by ELISA containing circum sporozoite protein of Plasmodium falciparum. An. vagus and An. sinensis in Muara Enim, South Sumatra was also confirmed by ELISA containing P. falciparum and P. vivax (Budiyanto et al., 2017). In addition, Munif et al., (2019) reported An. vagus was also a companion vector during the outbreak of malaria in Sukabumi because it contained P. falcifarum with a sporozoite index of 0.12% and an inoculation rate of 0.213.
Based on those informations, a study on the distribution and habitat characteristics of An. vagus larvae in the rice fields around the Dramaga IPB campus is important to study.

MATERIAL AND METHODS
The method used in this research was purposive sampling method. Anopheles larvae were collected using a dipper on watery rice fields in four villages around the Dramaga campus (Cikarawang, Babakan, Ciherang and Margajaya). The mosquitoes that were successfully collected were put into a small container to be identified up to the species level using the key morphology of the larvae according to O' Connor and Soepanto (1989). Each collection point was marked using the Global Positioning System and presented in a distribution map of An. vagus. in rice fields in the village around the Dramaga campus. The physical characteristics of water that were measured include temperature, pH, total dissolved solids, and electrical conductivity. The number of larvae that were collected was then performed the Pearson correlation test with each of the physical characteristics of the water.

RESULTS AND DISCUSSION
The results of this study obtained 309 Anopheles vagus larvae in 27 points of rice fields in Cikarawang Village, Babakan Village, and Ciherang Village, while in Margajaya Village they were not found (( Table 1 dan Fig. 1). The presence of An. vagus in the village rice fields around the campus was not evenly distributed. Rice fields in Cikarawang Village are the most points where An. vagus larvae can be found. The rice fields in Cikarawang Village are located close to residential areas that have buffalo and other livestock, while in Babakan, Ciherang, and Margajaya Villages, there are no buffalo stalls found around the rice fields. An. vagus was reported to have a preference for sucking animal blood (zoophilic) in Pesawaran and Muara Enim Districts (Hanafy 2015;Budiyanto et al. 2017).
The results of the measurement of the physical characteristics of water including pH, temperature, total dissolved solid and electrical conductivity varied between points where An. vagus larva was found, however did not show a significant correlation between each measurement and the number of larvae found (Fig 2). The pH value of rice field water where An. vagus found was 6.40-8.10 (mean 7.37). In Ogan Komering Ulu Regency, Maretasari et al. (2019) reported the pH value in the rice fields of An. vagus habitat was in acidic pH (5-6). Another study repoted that An. gambiae larvae lived in water with a pH of 4 -7.8 if there was sufficient food for consumption (Oyewole et al. 2009).
According to Clark et al. (2004) pH of water affects the successful breeding of mosquito larvae where mosquito larvae will die at pH <3 and >12. Akhiriyanti and Nugroho (2019) reported neutral pH levels (6.8-7.2) have a higher potential (86.4%) for breeding place of Aedes aegypti larvae. Neutral pH water conditions supported the plankton growth and its presence became a source of food  (Sunarti et al. 2018).
The temperature of the rice fields where An. vagus larvae found was between 26.6-31.7 o C (mean 28.78 o C). This temperature is still in line with the research of Kenglueca et al. (2005) who stated that larva An. vagus in Northwestern Thailand can be found in water temperatures of 25.4-32 o C. Rice fields are areas without shade so that sunlight can penetrate the water and provide a higher temperature value than areas shaded by trees. Warm water in sunlit habitats may be an important factor for larval development because warm water speeds up their development. In addition, warm temperatures allow more microbes to develop microorganisms that provide a food source for mosquito larvae (Minakawa et al. 1999).
Total dissolved solid value and water electrical conductivity in paddy-field where An. vagus was found hold a range of value of TDS (36-285) ppm  Astuti (2014), a larger value on TDS in a liquid imposes a probability of higher numbers of ion in the liquid, which makes the electricity conductivity in a larger value. Water EC value hold a negative correlation to An. Arabiensis larvae density. Anopheles gambiense larvae and An. arabiensis were detected in an environment where water conductivity is low and water electricity conductivity is above 2000 µm/cm which impose significant larvae decrease (Fillinger et al., 2009). High electricity conductivity caused by salinity and dissolved ion may trigger a negative impact on mosquito larvae growth (Closs et al., 2003). The TDS (total dissolved solid) and EC (electrical conductivity) values of water in rice fields where An. vagus found were 36-285 ppm and 71-262 µm/cm, respectively. According to Astuti (2014)