Updating in container selection and temperature relation of Aedes Mosquito Species in Bangkok Thailand.

Transcription

1 Available online at 5 th Burapha University International Conference 2016 Harmonization of Knowledge towards the Betterment of Society Updating in container selection and temperature relation of Aedes Mosquito Species in Bangkok Thailand. Oranicha Khamprapa, Narumon Komalamisra, Siriluck Attrapadung, Ronald Enrique Morales Vargas* Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand Abstract Despite that fifty years ago, the presence of Aedes aegypti, Ae. albopictus, Ae. scutellaris was reported in some areas of Bangkok, the bioecology of Ae. albopictus and Ae. scutellaris in sub-urban area of Bangkok have been scarcely ascertained. To better planning vector control strategies for the prevention and control of mosquito borne diseases up to date information on presence of potential disease vectors and their bioecology is of paramount importance. Therefore, we aimed to ascertain the breeding container type selection, and the population structure relation with temperature, of the Aedes mosquito species in the sub-urban of Bangkok, with specific emphasis on Ae. albopictus and Ae. scutellaris. Two kinds of human made artificial containers (earthenware jars and plastic buckets) were set up around houses located in Bang-Khae and Taling-Chan, selected base on previous history of dengue cases report. The containers were set around the house, one beside each other at 1 to 5 meters from the ground edge of the houses. Pupa abundance was monitored bi-weekly, and reared to adult at the laboratory, then identified based on their morphological characters. Higher number of pupa were collected from containers located close to the house, at 1 meter or under the house roof, moreover a positive association between the pupae abundance and temperature was observed in two kinds of container in both study sites. In Taling-Chan, two species were present, Ae. aegypti, and Ae. scutellaris; whereas in Bangkhae tree species were present, Ae. aegypti, and Ae. scutellaris, and Ae. albopictus. Overall, Ae. aegypti was the dominant specie followed by Ae. scutellaris and Ae. albopictus. Plastic buckets was preferred as a breeding place by the tree species when were set up close to the house, at 1 meter or under the house roof, whereas the earthenware jar was preferred at farther distance from the house, at areas surrounded by bushes, where was also observed the co-existence of Ae. aegypti with Ae. scutellaris and Ae. aegypti with Ae. albopictus. Moreover, our results showed a positive association between temperature and the abundance of Ae. aegypti and Ae. scutellaris, whereas with the abundance of Ae. albopictus a negative association was observed. Thus, our results seed the ground for the inclusion of the Ae. albopictus and Ae. scutellaris for the better planning an effective vector control in the studies areas, and by extension in the sub-urban of Bangkok Published by Burapha University. Keywords: Aedes, Dengue, Vector, Bangkok * Corresponding author. Tel.: or fax: address: ronald.mor@mahidol.ac.th 352

2 Some species of Aedes are vector for important arboviral diseases, for instance dengue, chikungunya and zika in tropical and subtropical regions. Aedes aegypti, Ae. albopictus are worldwide considered as the principal vectors of dengu (DENV-1, DENV-2, DENV-3, and DENV-4), chikungunya (CHIKV), and zika (ZIKV) viruses (Rueda, 2004; Thavara et al., 2009). Whereas Ae. scutellaris have been reported as dengue vector throughout Papua New Guinea, South Pacific and Australasian region (Rueda, 2004; Tsutomu and Akio, 1984). In Thailand, Yasuno and Tonn (1969) found three Aedes species, Ae. aegypti, Ae. albopictus and Ae. scutellaris, sharing breeding places in several areas of Bangkok. Currently, no vaccine or antiviral therapy is available for those viral diseases, thus vector control is the only method to prevent outbreak of those diseases. Implementing successful mosquito control program requires understanding what factors regulate vector population, as well as how it changes behavior to adapt to control measure (Wong et al., 2011). Control of Aedes mosquito is made challenging by their behavior. Ae. aegypti, considered the primary vector of dengue virus in urban areas, it mainly use artificial containers closely associated with human environment as their larva habitat (Yasuno and Tonn, 1969; Pant et al., 1973; Ponlawat et al., 2005; Ponlawat and Harrington, 2005). Whereas, Ae. albopictus mainly use natural habitats (coconut shells, tree holes, bamboo stumps, orchid, plant leaf etc.) as well as human made containers (flower pots, earthenware jars, tin cans, etc.) in the rural areas (Woogkoon et al., 2007; Estrada-Franco and Craig, 1995). More than 50 years ago, Ae. scutellaris has been found in Trat, Suratthani and Bangkok, breeding in natural container such as coconut shells, tree-holes life axils etc., and artificial container such as in tins, bottles, cement tanks (Yasuno and Tonn, 1969; Huang, 1972). However, Ae. albopictus and Ae. scutellaris distribution, eco-biology and behavior in sub-urban area of Bangkok is yet little know. Many Asia countries such as Philippine and Thailand usually use artificial container to store water for using in their house, generally, earthen jar, cement tank, and plastic containers (Focks and Alexander, 2007). Female mosquito water container selection for breeding is important to provide the highest offspring survival rate. Thus, to identify the selected container by mosquito species is important for a targeted reduction of number of new emerging adult population, the understanding of oviposition site is required. Choice of layingegg site is influenced by container type, lid and sun-exposure (Wong et al., 2011). Wongkoon et al. (2007) studied development site of Aedes in Thailand, they found that Aedes species was higher productive in artificial containers especially, earthen jar and plastic bucks, than that in natural containers. Moreover, Aedes larva higher abundant in dark color container and container without lid, that prevent gravid mosquito to oviposit in the container. In addition, the larger surface area, volume and depth container can increase number of Aedes egg (Derraik and Slaney, 2005; Harrington et al., 2008). The population of Aedes mosquito is regulated by climate factors such as rainfall, temperature, and relative humidity. Many studies have shown that Aedes mosquito abundance is higher in wet season because rainfall can provide larva habitat, especially the containers that are located outdoor (Wee et al., 2013; Wongkoon et al., 2007; 2013). However, Aedes mosquito can be founded in the containers during dry season. Generally, Asian people such as Thai, stored water in artificial and natural human made water containers during dry season, containers that are regularly fill up with water for storage purpose can provide oviposition sites throughout whole year (Focks and Alexander, 2007). Aedes mosquito takes longer periods to develop at low temperature (Rueda et al., 1990; Scott et al., 2000) and survived longer in high relative humidity conditions (Banu et al., 2014). In Thailand there is considerable information available on the Ae. aegypti bio-ecology and behavior, however little is still known about of Ae. albopictus and Ae. scutellaris in sub-urban areas of Bangkok. Thus, understanding the container type selection of Aedes mosquito species and the relation of temperature on that mosquito population are useful for help the community to planning vector control for the prevention and control of dengue in Thailand. 353

3 1. Materials and methods 1.1. Study sites This study was conducted in 2 sites, Bang-Khae and Taling-Chan districts, located in the west side of Bangkok, Thailand, far from each other around 6.6 kilometer. The study site were selected base on dengue incident and following our preliminary study that was found three species of Aedes; Ae. aegypti, Ae. albopictus and Ae. scutellaris around sub-urban areas of Bangkok. In general, these two sites compressed residential areas, canal and small orchard plantations. Three houses in Taling-Chan and five house in Bang- Khae were selected, based on previous dengue case report. In each study sites separated one house from another house at least 500 meter. The environment in Taling-Chan, two house consists of residential area, canal and plantations (T1-1, T1-2, T1-3, T3-1 and T3-2) and one house consists of residential complexes and canal (T2-1 and T2-2). Whereas in Bang-Khae, located in the south of Taling-Chan, First house consist of chicken farm surrounding by bushes and canal (B1). Another three houses consists of residential area, bushes and canal (B2, B4 and B5). And the last house consists of residential area and canal (B3). According climatological data for the period from Bangkok station of the meteorological department, the annual average temperature is 29.9ºC and average rainfall mm (Fig. 1.). Fig.1. The annual average temperature and rainfall of Bangkok, Thailand 1.2. The collection The pupa abundance was monitored bi-weekly, the life cycle from an egg to a pupa, take approximately days, from September 2015 to February 2016, by using two kinds of containers; black color plastic (20 cm diameter x 17.5 cm high x 17 cm deep x 13 cm bottom diameter) and earthenware jars (11 cm upper diameter x 16 cm high x 14 cm deep x 11 cm bottom diameter), that commonly find in any household of Thailand. At the beginning of the observation period both kind of container was filled up with 2,000 ml (at 10 cm deep of plastic container and 11 cm deep of earthenware jar) of clear water and placed together outside of each house. At the collection day, the whole contains of the container was empty in a plastic tray and pupa was collected and the rest was returned to the container. Only container that had water volume less than 1,000 ml (at 6 cm deep of plastic container and 7 cm deep of earthenware jar) was refilled with clear water. Pupae were reared to adult and identified by their morphological characters following the morphological key of Rattanarithikul et al (1994). 354

4 1.3. The temperature data Temperature data was obtained from the meteorological department. The average temperature from six days before collection were uses for analyze the relation with Aedes population. 1.4 Data analysis Chi-square test was used analyze differences between two kind of containers (black color plastic and earthenware jars), and the number of pupa and the emerged specie. The significance level at p < Spearman's correlation analysis was conducted to examine the correlation between the numbers of pupa or emerged adult from pupa and temperature. All test was two-tailed and the analysis was performed by using SPSS 18.0 software. 2. Results 2.1. The number of immature stage (pupa) in two kind of container In both study sites, the number of immature stage (pupa) was high in container set up close to house T1-2, T2, and B5 that have high human activity. The number of immature stage (pupa) significantly higher in black plastic container than that earthenware jar in house T1-2, T3-1, T3-2, and B5, whereas that significantly higher in that earthenware jar than black plastic container in house T2 and B1. House T1-1, T1-3, B2, B3, and B4 did not differ in two kinds of containers (Fig. 2.). Fig. 2. (a) The number of immature stage (pupa) in two kinds of container in Taling-Chan and (b) Bang-Khae. 2.2 The correlation between number of immature stage (pupa) and temperature In both study sites, the six days average temperature was positively associated with the number of pupa in both kind of containers (Fig.3. and Table 1.). 355

5 Fig. 3. (a) The correlation between immature stage (pupa) and temperature (ºC) in Taling-Chan and (b) Bang-Khae. Table 1. Spearman correlation coefficients between the number of immature stage (pupa) and temperature in both study sites. Container type Spearman correlation Taling-Chan Bang-Khae Plastic container 0.658** 0.504** Earthenware jar 0.733** 0.277* * p < 0.05, **< The number of emerged Aedes mosquito in two kind of container The immature stage (pupa) that emerged to be Aedes aegypti and Aedes scutellaris were found in both study sites except Aedes albopictus was found only in Bang-Khae. Ae. aegypti was dominant in both sites, Ae. scutellaris and Ae. albopictus were present in houses surrounding by bushes. In Taling-Chan, Ae. aegypti and Ae. scutellaris were significantly higher in black plastic container than earthenware jar but that both species did not differ in two kind of containers in house 3-1, and Ae. scutellaris did not differ in two kind of containers in house 1-1 and 1-2. (Fig. 4a.) In Bang-Khae, Ae. aegypti was significantly higher in black plastic container than earthenware jar except in house 1 and 3. There was found Ae. scutellaris in earthenware of house 1 and 5 while in black plastic container was found in house 2, 4 and 5. For Ae. albopictus, It s was found in earthenware of house 3 and 4 while in black plastic container was found in house 1, 2 and 4. (Fig. 4b.) The co-existence of Ae. aegypti with Ae. scutellaris and Ae. aegypti with Ae. albopictus were commonly observe in container located near the houses surrounding with bushes. Fig. 3. (a) The number of emerged Aedes mosquito in two kind of container in Taling-Chan and (b) Bang-Khae. 2.4 The correlation between the numbers of emerged of Aedes mosquito and temperature In both study sites, the six days average temperature were positively associate with the number of immerging stage (pupa) that emerged to be Ae. aegypti and Ae. scutellaris whereas that temperature was negatively associate with the number of immature stage (pupa) that emerged to be Ae. albopictus (Fig.5. and Table 2.). 356

6 Fig. 5. (a) The correlation between the numbers of emerged of Aedes mosquito and temperature Taling-Chan and (b) Bang-Khae. Table 2. Spearman correlation coefficients between the numbers of emerged of Aedes mosquito and temperature in both study sites. Container type Spearman correlation Taling-Chan Bang-Khae Ae. aegypti 0.758** 0.826** Ae. scutellaris 0.777** 0.828** Ae. albopictus n/a ** ** p < 0.01 Ae. albopictus was not present in Taling-Chan 3. Discussion This research studied the container type selection of Aedes species and relation of that with temperature in Bangkok, Thailand that can have important consequence for regulation new emerging adult mosquito population. Two kind of container, black plastic container and earthenware jar were set up in two study sites; Taling-Chan and Bang-Khae. Pupa surveillance have been promoted more accurate than larva surveillance (Focks and Chadee, 1997; Strickman and Kittayapong, 2003; Focks and Alexander, 2007). The pupae were monitoring bi-weekly then reared to adults for identification by morphology. Three species of Aedes, Ae. Aegypti, Ae. albopictus, and Ae. scutellaris was found in study site that related with the studied of Yasuno and Tonn (1969) around 50 years ago. However, little know yet about bio-ecology of Ae. albopictus and Ae. scutellaris in sub-urban area of Bangkok. The combination factors of human activity, vegetation cover, container type and climate affect to oviposition site selection of female mosquito (Okogun et al., 2003; Wai et al., 2012). In this study, the number of immature larva (Pupa) was associate with human host activity (Fig. 2.), which similar to the work of Carvajal et al (2009) and Nelson (1976), most of the positive Aedes mosquito pupa were found in the container located near the houses, mainly Ae. aegypti (Yasuno and Tonn, 1969). The distribution Ae. albopictus and Ae. scutellaris can overlap with Ae. aegypti in the same urban environment in Thailand (Yasuno and Tonn, 1969). While the more commonly found Ae. albopictus and Ae. scutellaris in open area with vegetated space are prevalent. They prefer to lay egg in water reservoirs containing decaying matter (Estrada-Franco and Craig, 1995; Yasuno and Tonn, 1969). Similarly to our 357

7 study, these two species and co-exist of them with Ae. aegypti were highly present in the house that surrounding by bushes. The visual parameter of color, sun-exposure and texture of container are affect to seeking the oviposition site of mosquitoes (Hoel et al., 2011). The containers that widely used for water storage that can be oviposition site in Thailand are plastic container and earthenware jar (Yasuno and Tonn, 1969.; Wongkoon et al, 2007). In this research, we found high number of Ae. aegypti and Ae. scutellaris in black plastic container than earthenware jar (Fig. 4.). Many studies support that black color container are more attractive to Aedes mosquito (Muir et al., 1992; Hoel et al, 2011). Moreover, plastic container in this study had wider surface of water that exposure to the sun, sun-exposure reach warmer temperature. Female mosquito detect container with warmer water where their offering develop faster and find bigger size of container for laying more eggs (Derraik and Slaney, 2005; Harrington et al., 2008; Banu et al., 2014). For container texture, The earthenware jar are heat resistant and keep water cool for long periods despite mild environmental temperature changes, however water easy evaporate from pores of a jar compare with plastic container. Temperature is important abiotic factor that influent to population dynamic of Aedes. High temperature grater produce Aedes adult and that increased development rate (Rueda et al., 1990; Scott et al., 2000). Similar with our research, temperature positively correlation with the number of immature (pupa) and their emerged Aedes adult. The greater production of mosquito maybe associate with microbial activity and decomposition rate are positive relate to high temperature (Livdahl et al., 1984). Aedes species are important vector of dengue (DENV-1, DENV-2, DENV-3, DENV-4), chikungunya (CHIKV), and zika (ZIKV) viruses in tropical and sub-tropical regions (Rueda, 2004; Thavara et al., 2009). Urbanization, globalization and lack of effective mosquito control drive emergence of epidemic dengue (Gubler, 2011).Thus, updating information of Aedes mosquito ecology are important to investigate effective method to control this mosquito in community. For further, we will study the correlation of Aedes mosquito with microenvironment inside the container, including water temperature and microorganism to give more useful information about Aedes mosquito distribution of each kinds container. References Banu, S., Hu, W., Guo, Y., Hurst, C., & Tong, S. (2014). Projecting the impact of climate change on dengue transmission in Dhaka, Bangladesh. Environ Int, 63, Carvajal, J. J., Moncada, L. I., Rodriguez, M. H., Perez Ldel, P., & Olano, V. A. (2009). [Characterization of Aedes albopictus (Skuse, 1894) (Diptera:Culicidae) larval habitats near the Amazon River in Colombia]. Biomedical, 29(3), Derraik, J. G., & Slaney, D. (2005). Container aperture size and nutrient preferences of mosquitoes (Diptera: Culicidae) in the Auckland region, New Zealand. Journal of vector ecology: Journal of the Society for Vector Ecology, 30(1), Estrada-Franco, J. G., & Craig, G. B. (1995). Biology, disease relationships, and control of Aedes albopictus: Pan American Health Organization. Focks, D. A., & Alexander, N. (2007). Multicountry study of Aedes aegypti pupal productivity survey methodology: Findings and recommendations. Focks, D. A., & Chadee, D. D. (1997). Pupal survey: an epidemiologically significant surveillance method for Aedes aegypti: an example using data from Trinidad. Am J Trop Med Hyg, 56(2), Gubler, D. J. (2011). Dengue, Urbanization and Globalization: The Unholy Trinity of the 21st Century. Tropical Medicine and Health, 39(4 Suppl), 3 11 Harrington, L. C., Ponlawat, A., Edman, J. D., Scott, T. W., & Vermeylen, F. (2008). Influence of container size, location, and time of day on oviposition patterns of the dengue vector, Aedes aegypti, in Thailand. Vector borne and zoonotic diseases, 8(3), Hoel, D. F., Obenauer, P. J., Clark, M., Smith, R., Hughes, T. H., Larson, R. T., & et al. (2011). Efficacy of ovitrap colors and patterns for attracting Aedes albopictus at suburban field sites in north-central Florida. Journal of the American Mosquito Control Association, 27(3), Huang, Y. M. (1972). Contributions to the Mosquito Fauna of Southeast Asia. XIV. The Subgenus Stegomyia of Aedes in Southeast Asia I - The Scutellaris Group of Species, 110 p. Livdahl, T. P., Koenekoop, R. K., & Futterweit, S. G. (1984). The complex hatching response of Aedes eggs to larval density. Ecological Entomology, 9(4),

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