Distances from mangrove forest affecting mosquito larvae species and abundance in Nakhon Si Thammarat, Thailand Rungrit Rattanapan, Apiwat Pramchu, Supakrit Srimorkmek Nang – Ueay Wittaya School, Nakhon Si Thammarat, Thailand Teacher: Pennapa Kooviboonsin, email: [email protected] 8 March 2016 ABSTRACT In this study, we investigated how the distances from the mangrove area affecting species diversity and abundance of mosquito larvae in Nakhon Si Thammarat, Thailand. We randomly selected ten houses at 0, 200, 400, 600, 800 and 1000 m from the mangrove area and collected mosquito larvae from both indoor and outdoor water containers. All mosquito larvae were identified up to genus or species levels under a microscope. Our results showed that there were five mosquito species/genus: Aedes aegypti, Aedes albopictus, Culex spp., Toxorhynchites spp., and Armigeres spp. present in this area. Ae. aegypti was higher in numbers at 200 and 400 m, Ae. albopictus was higher in numbers at 1000 m, Culex spp. was higher in numbers at 400 and 800 m, Toxorhynchites spp. was higher in numbers from 600- 1000 m, and Armigeres spp. was higher in numbers at 1000 m. This result indicates that distances from mangrove area have a strong effect on mosquito larvae species and abundance. Dengue is primarily transmitted by Aedes aegypti and secondarily by Aedes albopictus. Our study would help us gain a better standing on how we could actively prevent dengue incidences in the area. Keywords: Distance, Mangrove area, Aedes aegypti, Aedes albopictus, Culex spp., Toxorhynchites spp., Armigeres spp. 2 Introduction Mangrove is an important ecosystem between the land and the sea (Jin et al., 1995). Mangrove wetlands are considered as breeding grounds for different mosquito species (Department of Fisheries, 2012). Mosquitoes have a worldwide distribution occurring throughout the tropical and temperate regions (Service, 1996). Besides their widespread distribution, mosquitoes show higher density in their habitats. Mosquitoes that inhabit freshwater and brackish water habitats play an important role in the ecological food chain, and many of them are vicious biters and transmitters of various human and animal diseases (Rued, 2008). Dengue is primarily transmitted by Aedes aegypti and secondarily by Aedes albopictus. Both mosquitoes breed in both natural (e.g., rock pools, tree holes and leaf axis) and artificial (e.g., water tanks, blocked drains, pot plants and food and beverage containers) water containers in both rural and urban areas (Naish et al., 2014). However, many factors such as container types, distances from forests, fishery and non-fishery households affect the types and density of different mosquito populations and topography (Wongkoon et al., 2005, 2007; Preechaporn et al., 2006; Lipps, 2008). Ecological and behavioral knowledge about mosquito species and abundances are required as a baseline to understand the transmission dynamics of vector - borne pathogens and therefore to implement effective control programs. In the last decades, the knowledge about ecology, disease transmission and control of Aedes spp. has increased worldwide (Vezzani, 2007). However, the information regarding mosquito types and their numbers in mangrove forest is limited (Rajavel et al., 2005). The objective of this study is to examine species and abundance mosquito larvae at 0, 200, 400, 600, 800 and 1,000 m from mangrove forest. Research question Do distances from mangrove area affect the type and abundance of mosquito larvae? Hypothesis If the distances from mangrove areas have some effect on the type and abundance of mosquito larvae, then there should be some differences in the type and abundance of mosquito larvae among distances from mangrove areas. Materials and Methods Study sites Nakhon Si Thammarat is one of the 77 provinces of Thailand, that is located in south of Thailand (Figure 1). The area of total mangrove forest is about 117.68 km2 in southern Thailand, and 2.79 km2 in Thasala district, Nakhon Si Thammarat. We conducted this study at Moo 7 Ban Na Thap and Moo 14 Ban Leam villages, Thasala district. We selected six distances (at 0, 200, 400, 600, 800 and 1,000 m), starting near the mangrove forest to further distance (Figure 1). We selected ten houses randomly at each distance, and collected all mosquito larvae from all indoor and outdoor containers. Entomological studies All collected mosquito larvae were brought to the Vector Borne Disease Control Centre, 11.2 Nakhon Si Thammarat laboratory, preserved and identified up to species and/or genus level under microscope by using Rattanarithikul and Panthusiri’s keys (Rattanarithikul 3 et al., 1994). We found five mosquito larvae (Ae. aegypti, Ae. albopictus, Culex spp. Toxorhynchites spp. and Armigeres spp.) in this study. Figure 1. Map of the study sites. The six distances from mangrove areas in Thasala district, Nakhon Si Thammarat province, Thailand Statistical analysis We used crosstab chi-square test to know the numbers of mosquito larvae species among different distances, and chi square tests to see the differences in numbers of each mosquito larvae among distances. The significant tests were two tailed with significant levels at P<0.05. Results Numbers of different mosquito larvae among distances The numbers of mosquito larvae varied among distances (Table 1). Among distances, Ae. aegypti was higher in numbers than other mosquito larvae at 200, 400, 600, and 1000 m. On the other hand, Ae. albopictus was higher in numbers than other mosquito larvae at 0 and 800 m. Ae. aegypti and Ae. albopictus were found at all distances, but Toxorhynchites spp. was not found at 0 m, Culex spp. was not found at 1000 m, and Armigeres spp. was not found at 600 and 800 m distances. We found 1-25 mosquito larvae per container at all distances but at 400 m, we found mosquito larvae greater than 25 larvae per container (Figure 2). 4 Figure 2. The number of containers and mosquito larvae/container at 0, 200, 400, 600, 800 and 1000 m from mangrove areas. 0, 1 – 25, and > 25 mosquito larvae/container. Table 1. Mosquito larvae species and abundance from six distances from mangrove forest (*P<0.05) Numbers of mosquito larvae species and genus Distances Ae. aegypti Ae. Culex spp. Toxorhynch Armigeres Statistical (m) albopictus ites spp. spp. test 0 140 272 2 0 59 200 917 114 12 3 4 2 20 = 400 1110 344 58 2 53 600 553 154 20 9 0 1335.13, 800 60 146 53 10 0 P < 0.001 1,000 529 425 0 7 103 2 2 2 2 2 5 = 5 = 4 = 86.76 4 = 8.19, 3 = 89.95 1553.81 322.21 P < 0.001 ns P < 0.001 P < 0.001 P < 0.001 Mosquito larvae and distances from mangrove areas When we compared the number of mosquito larvae species among distances using chi-square tests, we observed that Ae. aegypti was higher in numbers at 200 and 400 m, Ae. albopictus was higher in numbers at 1000 m, Culex spp. was higher in numbers at 400 and 800 m, Toxorhynchites spp. was higher in numbers from 600-1000 m, and Armigeres spp. was higher in numbers at 1000 m (Table 1). At 0 m from the mangrove area, there were seven types of positive containers (ranging from high to low numbers of mosquito larvae): small earthen jars, plastic buckets, coconut shells, bowls, gallon plastics, used foam boxes and plastic bottles. We found one 5 container (i.e. small earthen jar) that had the number of mosquitoes higher than 100 larvae (Figure 3a). At 200 m from the mangrove area, there were seven types of positive containers (ranging from high to low numbers of mosquito larvae): small earthen jars, plastic buckets, cement tanks, animal pans, ant guards, used foam boxes, others (bike seat and old refrigerators), aluminum containers, plastic bottles and bowls. There were two types of water containers that found the number of mosquitoes exceed 100 larvae, i.e. small earthen jars and plastic buckets) (Figure 3b). At 400 m from the mangrove area, there were nine types of positive containers (ranging from high to low numbers of mosquito larvae): plastic buckets, bowls, cement tanks, small earthen jars, aluminum containers, refrigerator drainages, discarded tires, coconut shells and plastic bottles. There were five types of water containers that found the number of mosquitoes exceed 100 larvae, i.e. plastic buckets, bowls, cement tanks, small earthen jars and aluminum containers (Figure 3c). At 600 m from the mangrove area, there were six types of positive containers (ranging from high to low numbers of mosquito larvae): plastic buckets, bowls, cement tanks, preserved areca jars, flower vases and used foam boxes. There was one type of water containers that found the number of mosquitoes exceed 100 larvae, i.e. plastic bucket (Figure 3d). At 800 m from the mangrove area, there were eight types of positive containers (ranging from high to low numbers of mosquito larvae): plastic buckets, plastic bottles, old boat, small earthen jars, plant pot, aluminum containers, other (mat), and cement tanks. There was one type of water containers that found the number of mosquitoes exceed 100 larvae, i.e. plastic bucket (Figure 3e). At 1000 m from the mangrove area, there were ten types of positive containers (ranging from high to low numbers of mosquito larvae): plastic buckets, cement tanks, bio fermentation tanks, small earthen jars, aluminum containers, mortar, ceramic bowl, plastic bottles, basins, and refrigerator drainages. There were two types of water containers that found the number of mosquitoes exceed 100 larvae, i.e. plastic bucket and cement tanks. (Figure 3f). Discussion We observed five mosquito species (Ae. aegypti, Ae. albopictus, Culex spp. Toxorhynchites spp. and Armigeres spp.) in this mangrove forest. Previous many studies showed the differences in mosquito larvae species from different mangrove forests such as Benjaphong et al.