Journal of Sustainability Science and Management eISSN: 2672-7226 Volume 16 Number 1, January 2021: 120-128 © Penerbit UMT

ENVIRONMENTAL ASSESSMENT AND INFESTATION LEVEL OF THE DENGUE VECTORS AT RESIDENTIAL AREA IN PUNCAK ALAM,

FATIN AZURA1, NAZRI CHE DOM*1,2 AND SITI NAZRINA CAMALXAMAN1,2

1Centre of Environmental Health & Safety, 2Integrated Mosquito Research Group (IMeRGe), Faculty of Health Sciences, Universiti Teknologi MARA, 42300 Puncak Alam, Selangor, .

*Corresponding author: [email protected] Submitted final draft: 21 May 2020 Accepted: 3 June 2020 http://doi.org/10.46754/jssm.2021.01.011

Abstract: The control of mosquitoes in residential areas calls for in-depth knowledge of the breeding habits of the mosquitoes, especially Aedes aegypti and Aedes albopictus. Therefore, this study aims to assess the environmental condition and infestation level of Aedes vectors at selected residential areas in Puncak Alam, Selangor. The aims of this study are to understand the environmental profile of residential areas towards infestation level of dengue vectors. A pilot study was conducted in Puncak Alam in order to understand the infestation profile of dengue vectors in residential areas by assessing the environmental condition index (ECI) in front and yard area of residential area. In this study, a minimum of a hundred houses in each residential area was observed for the environmental condition of front and yard of the premises. Concurrently, a total of thirty ovitraps were placed randomly at outdoor premises in order to measure the infestation level of the Aedes mosquitoes. A

total of 318 households were inspected in both front area (FA) and yard area (YA) where in general, the environmental condition in front of houses is better than the yard area. The same pattern was also observed in which the infestation level of Aedes mosquito

population in FA and YA ranged from 15.40 – 35.25 and 11.88 – 47.91, respectively. In conclusion, environmental conditions play a main role in the distribution of dengue vector.

Keywords: Residential area, environmental condition, infestation level, Aedes.

Introduction (Sarfraz et al., 2012) and brackish waters Urbanisation is a factor that can increase the (Idris et al., 2013; Ramasamy et al., 2011). number of preferred habitats for Aedes mosquito The presence of vegetation condition between thus increasing the density and survival of Aedes community area and mosquito breeding site mosquito especially in a residential area (Saleeza provides a disposal route for biting insect to et al., 2011). Another factor that contributes community areas. According to Kesetyaningsih in dengue transmission and distribution is et al., (2016) the mosquito survival was environmental parameters. This parameter can affected by humidity that is maintained by the cause changes in dengue transmission that is presence of vegetation. Next, human ecology is related to the host, such as the demographic responsible for the creation of a mosquito genic pattern. Furthermore, the land use such as housing environment. Generally, residential area is a type, soil moisture and greenness can contribute potential source for the existence of breeding to the epidemic of dengue transmission (Aziz et sites due to environment condition, either indoor al., 2011). or outdoor area. Community areas, particularly residential Vector surveillance can be used to determine areas, are located in close proximity to major changes in the distribution and vector density mosquito habitats. Previous entomological and to obtain relative control measurement studies showed that dengue vectors have been of the vector population. It also can serve to captured in vegetated areas (Hayden et al., 2010; identify high-density infestation study area and Vezzani et al., 2005), rubber plantations (Paily selection of sampling method depending on et al., 2013; Sumodan, 2003), marshy swamps the vector surveillance objective. Thus, several ENVIRONMENTAL ASSESSMENT AND INFESTATION LEVEL OF THE DENGUE VECTORS 121 indices have been described as vector population eggs laid in their habitat. Therefore, this study monitor for dengue transmission. There are was aimed to assess the environmental condition three approaches of dengue measures commonly and infestation level of Aedes vectors at selected used in Aedes surveillance in residential areas residential areas in Puncak Alam, Selangor. namely: (i) premise condition index (Roberto et al., 2013; Parasuraman et al., 2012a) (ii) ovitrap Materials and Methods surveillance (Rozilawati et al., 2007 and Ligia et al., 2013) and (iii) integrating both approaches Study Site and Study Population (Roberto et al., 2013 and Leticia et al., 2005). Puncak Alam is the main township development Premise condition index (PCI) value score in the District, State of Selangor, indicates a simple index incorporating predictor Malaysia and has been selected as the case of the mosquito breeding (house condition, study area. is one of yard tidiness and degree of shade) that does not the less urbanised districts in Selangor. It is require indoor inspection of the premises (Tun- located approximately 20 kilometres in the Lin et al., 1995). However, vulnerability of the northwest direction from , the state PCI includes inability of the inspector to observe capital of Selangor. Puncak Alam development many rear yards’ condition and the risk of seeing started in the late 90’s under the management inconsistent PCI scoring between different of Bukit Cherakah Development Sdn Bhd inspectors (Parasuraman & Radhakrishnan with approximately 57km2 in size. Currently, 2012b). Review conducted by from Ligia et most of the developments in Puncak Alam al., (2013) showed that mosquito behaviour are housing area with a small percentage of is the main factor in the disease epidemiology commercial and industrial units. As a sub-urban transmitted by mosquitoes. Therefore, the area, Puncak Alam is surrounded by rural lands ovitrap acts as an effective tool for providing within the boundary of Kuala Selangor district. spatial and temporal data in dengue control Puncak Alam was selected due to its population measures. In general, most of the surveillance distribution with a variety of new residential studies, either the epidemiological evidence or areas and has a significant public health quantitative methods were used for assessing the implication in relation to control and prevention dengue transmission. of dengue outbreak. Ovitrap surveillance was used as a sampling technique to detect and measure the Study Design density of mosquito population by measuring A minimum of 318 houses in selected the positive ovitrap index (POI) (Ligia et al., residential areas in Puncak Alam was inspected 2013; Wan Norafikah et al., 2009; Rozilawati in each zone (A, B and C). Within the selected et al., 2007). POI is a percentage of Aedes residential area 30 houses chosen randomly/ positive ovitrap divided by number of ovitraps zones were used to observe the condition of the collected from the study (Wan Norafikah et environment and to measure the infestation of al., 2009). Prevention and control measures Aedes vectors, using ovitrap. The front and back of the dengue disease are dependent on vector yards of the premises were used to evaluate the surveillance and control measures by integrating environmental condition of the residential areas both approaches of ovitrap surveillance and using the criteria that contribute to the existence the environmental condition index (ECI) as an of mosquito activities which include house indicator of mosquito infestation that could be maintenance, solid waste management, degree used to relate between ECI and infestation to of shade and drainage facilities. Then each determine the density of mosquito population premise was scored from lower to the highest (Roberto et al., 2013). The ovitrap has been according to the method developed by Tun-Lin used as a proxy to measure a number of adult et al., (1995). At the same time, the ovitraps mosquitoes present from the total number of were placed randomly at outdoor premises in a

Journal of Sustainability Science and Management Volume 16 Number 1, January 2021: 120-128 Fatin Azura et al. 122 shaded area in order to measure the infestation As for scoring of the environmental of Aedes vectors. After consecutive days of condition index (ECI), the house was classified exposure, the ovitraps were recollected and then into three classes. Score 1 = well maintained were brought to the laboratory for egg count and house (structure in good condition, new paint, species identification (Hasnan et al., 2017). place is visibly clean and well maintained), Score 2 = reasonably well maintained (poor or Environmental Condition Assessment simple structure, but well organised and clean) and Score 3 = poorly maintained (poor structure, The purpose of this assessment is to evaluate peeling walls, broken or improvised items, little the environmental condition including drainage organisation or cleanliness). Yard classified facilities and solid waste management. The as Score 1 = well maintained (organised, no poorly built and improperly managed drainage apparent waste or scrap, grass is short, yard system can contribute to the high mosquito well maintained), Score 2 = reasonably well infestation. For instance, the clogged drains maintained (moderately well-kept or poor with clear stagnant water are considered good structure, but well organised and clean) and artificial container to female mosquitoes that lay Score 3 = poorly maintained (disorganised, their eggs to complete the life cycle. Mosquito waste or scrap seen, unkempt grass, tires, infestation can become worse when residents bottles). The degree of shadow classified as illegally dump the waste or garbage around the Score 1 = little or no shade (external area with housing area. Meanwhile, the condition of the less than 25% of 41 shade, no large tress or any premises was observed if they are structurally other structure that works as a sunblind), Score well kept or poorly maintained that could 2 = some shade (degree of shade in external area contribute to mosquito infestation. Table 1 shows ranging from 25% to 50%) and Score 3 = plenty the descriptions of components and scores used of shade (external area with over 50% of shade, to assess the environmental condition. large tress, a sunblind-like structure and layers

Table 1: The descriptions of components and scores used to measure the environment condition index (ECI) (Tun-Lin et al.,1995)

Score House Condition Front/Yard Condition Degree of Shade Drainage Facilities

3 Poorly maintained Poorly maintained Plenty of shade Poorly maintained (poor structure, (disorganised, waste or (external area with over (poor structure, peeling walls, scrap, unkempt grass, 50% of shade, large little organisation or broken or tires, bottles) tress, a sunblind-like cleanliness) improvised items, structure, and layers of little organisation or shrubs with a greenhouse cleanliness) effect) 2 Reasonably well Reasonably Some shade (degree of Reasonably well maintained (poor or well maintained shade in external area maintained (poor or simple structure, but (moderately well-kept ranging from 25 to 50%) simple structure, but well organised and or poor structure, but well organised and clean) well organised and clean) clean) 1 Well maintained Well maintained Little or no shade Well maintained (structure in good (organised, no apparent (external area with less (structure in good condition, new paint, waste or scrap, grass than 25% of shade, no condition, well place is visibly clean is short, yard well large trees or any other organised and well and well maintained) maintained) structure that works as a maintained) sunblind)

Journal of Sustainability Science and Management Volume 16 Number 1, January 2021: 120-128 ENVIRONMENTAL ASSESSMENT AND INFESTATION LEVEL OF THE DENGUE VECTORS 123 of shrubs with a greenhouse effect. Whereas, the was calculated and classified into four levels, score of drainage facilities regarded as Score 1 namely level 1 (POI<5%), level 2 (5% < = well maintained (structure in good condition, POI<20%), level 3 (20% < POI < 40%) and well organised and well maintained), Score 2 level 4 (POI > 40%) to determine the infestation = reasonably well maintained (poor or simple level. The trend analysis was used to determine structure, but well organised and clean) and the pattern of environmental condition and Score 3 = poorly maintained (poor structure, infestation level at selected residential areas. little organisation or cleanliness). Finally, the All statistical calculation was performed using environmental condition was classified based Statistical Package for Social Science (SPSS). on the average score. The interpretations of the scores are: Good (Score 4 & 5), Regular (Score Results and Discussion 6 & 7), Bad (Score 8 & 9) and the Worst (Score 10 & 11). A total of 318 households were inspected

in both the front area (FA) and the yard area Infestation of Aedes Vector Using Ovitrap (YA) for the presence of pre-mature and adult Surveillance Aedes albopictus. The number and percent distribution of the positive houses according A total of thirty ovitraps were placed randomly to the environmental condition assessment was in each residential area and was pre- ranked as shown in Table 2. The lowest score determined to be placed outdoor. Wan Norafikah indicates a good condition and low risk for et al., (2011) mentioned that all mosquito infestation at a residential area, while ovitraps should be placed in proximity to other the highest score indicates the worst condition potential breeding containers with minimum and favourable breeding environment for physical and environmental disturbance and mosquitoes. then recovered after three to four days. Before that, the remaining water contained inside the Environmental condition assessment: ovitrap was not disposed, instead, it was kept Generally, the majority of houses in the and the ovitrap container was wrapped by with residential areas in Puncak Alam were classified plastic to prevent water from leaking and then as regular condition. Furthermore, the conditions brought to the insectarium. Next, the water in of the front and the yard of houses were also the ovitrap container was filtered in order to evaluated where the yard condition recorded the collect eggs that had fallen from the paddle. highest score (YA: 105) as compared to the front condition of the houses (FA: 94). This finding Data Analysis and Management indicates that the environmental condition in front of the houses is better than the yard area. (i) Environmental condition assessment: This finding reflects the favourable breeding Premises was scored from lower to the highest. environment condition in residential housing After scoring each parameter, the final score areas (Figure 2). was evaluated to indicate the environmental condition of the residential area. (ii) Infestation of Aedes vectors: Positive ovitrap index (POI)

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Figure 2: Environmental condition of housing in the residential area in the front and the yard conditions based on different scores, which reflect the favourable condition for Aedes vectors

Infestation profile of Aedes in residential very little shade (25%). Furthermore, the ECI areas: A total number of 270 ovitraps were score in the front/yard conditions may affect the deployed randomly which were placed in occurrence of the Aedes species eggs (Figure residential areas. During the survey, 87% - 90% 3B). of ovitraps were recovered after four consecutive From this study, some patterns of habitat days. In general, all residential areas in both preferences were observed. This result shows settings, either in the front of houses or the that the infestation of Aedes vectors in this yard, the conditions had high infestation level study is related to human population and human and the POI percentage was recorded at more activities due to some factors such as low relative than 50% (Figure 3A). The results indicate shaded area at human settlement (Gerusa that the residential area acts as the main area et al., 2014; Dom et al., 2016). Polystyrene for distributing the dengue virus due to the cups, tins and plastic bottles are widely used by availability of artificial breeding places, mainly our community nowadays. Improper disposal caused by the surrounding conditions that are or littering of these materials may increase capable of storing water. the number of containers made available for Trend analysis was conducted in searching mosquitoes to breed. Source reduction or the connection between the pattern of elimination is known as the most effective way environmental condition and infestation of Aedes to reduce the population of Aedes mosquitoes vectors in residential areas and this has led to a and the diseases they caused to - the human comparison of the environmental condition and population. If the effort is done frequently it infestation of Aedes vectors. This preliminary will lead to a permanent and effective control. analysis has demonstrated that most of the Other than that, source reduction is also known high infestation of Aedes vector was observed as the most economical and easy method to in residential areas with bad environmental be conducted within the affected areas of this conditions. In fact, the possibility of detecting disease-bearing insect. This can be done easily positive breeding of Aedes was higher in the by turning upside down large earthenware to premises with more shade (75%) compared with prevent Aedes female mosquitoes from breeding,

Journal of Sustainability Science and Management Volume 16 Number 1, January 2021: 120-128 ENVIRONMENTAL ASSESSMENT AND INFESTATION LEVEL OF THE DENGUE VECTORS 125 Bad ECI Level Regular Regular Regular Regular Regular Regular Regular Regular Regular ) and drainage ) and drainage 3 6.46 6.13 6.79 6.74 6.29 6.47 6.92 8.19 7.33 6.82 ECI ). The result was The result was ). A (TS/TP) *Average *Average Score A 226 196 265 256 220 220 252 295 242 (TS) 2169 Total Total Score 4 ), degree of shade (V 60 58 75 63 52 70 71 83 60 V 2 592 Yard Area, Y Area, Yard 3 ) and in the yard area (Y 48 37 53 55 53 38 53 53 64 V A 454 2 83 67 92 93 80 78 85 85 V 105 768 Criteria for Environmental Condition Index (ECI) Environmental Criteria for 1 35 34 45 45 35 34 43 54 33 V 358 ), waste management (V 1 ) 4 Bad ECI Good Good Good Good Level Regular Regular Regular Regular Regular 6.11 6.66 5.49 5.37 6.40 5.65 8.47 5.89 6.21 6.14 ECI facilities (V (TS/TP) *Average *Average Score A 214 181 214 204 224 192 305 214 205 1951 Total Total Score (TS) Score 4 39 38 40 43 55 37 74 41 45 V 412 Front Area, Area, Front F 3 87 59 75 55 70 70 87 56 55 V 614 2 53 52 60 68 64 51 94 70 72 V 584 Criteria for Environmental Condition Index (ECI) Environmental Criteria for 1 35 32 39 38 35 34 50 47 33 V 343 35 32 39 38 35 34 36 36 33 318 (TP) Total Total Premises 1 (B) 1 (C) 2 (B) 2 (C) 3 (B) 3 (C) 1 (A) 2 (A) 3 (A) Table 2: Pattern of environmental condition residential area based on the front houses (F Table Average Locality based on the criteria for environmental condition namely house (V *Note: The environmental condition was classified based on the average score. The interpretations of the score are: Good (Scores 4 & 5), Regular (Scores (Scores Regular 5), & 4 (Scores Good are: score the of interpretations The score. average the on based classified was condition environmental The *Note: The annotations in bracket, (A, B and C) represent the zones used to observe environmental ( Scores 10 & 11). Worst 6 & 7), Bad (Scores 8 9) and the Aedes vectors by using ovitrap surveillance. condition and measuring the infestation of

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Figure 3: (A) Infestation profile of Aedes vectors in different settings in residential areas (B) Relationship of the environmental condition score with the infestation of Aedes vectors in residential areas. discarding water retained from all old containers experimental studies may be required to make it around the houses, as well as properly cleaning more suitable up all containers like flower vases that could Community-based approach should go hand retain stagnant water. Individuals should be in hand with educational approach to ensure that tactful at all times and conduct self-inspection the community is exposed to the knowledge of around their houses to see whether there are vector control and what the diseases are that positive breeding sites under shaded trees or vectors would likely spread. Several parties like other hidden places that could retain water. JKKK (Jawatankuasa Kemajuan Kampung) and RT (Rukun Tetangga) should play their roles in Conclusion taking care of safety, health and welfare of the community in their areas. This could be done Overall this study found that environmental through “gotong-royong” by cleaning the areas condition of houses may provide a favourable and compounds that are prone to be mosquito condition for the Aedes species. The conditions breeding sites. Also, they can together clean up differ based on peoples’ habits, such as in clogged drains and unused wells to prevent the water management, water storage due to water breeding. Communities that understand the need scarcity, and works associated with water, like to make behavioural changes are the ones that cement works. Thus, the use of ECI indicator are most effective in controlling diseases like can be used in improving the method for vector dengue. surveillance. An effective surveillance system is essential for planning, implementation, and monitoring of disease control programmes. Acknowledgements Findings from this study help to conduct a rapid The authors would like to sincerely thank the survey of Aedes mosquitoes in a place with a Ministry of Health, Malaysia for providing minimal number of manpower and in turn, with ground data on dengue surveillance for this the help of ECI, delimitation is very possible in research work. University of Technology MARA residential areas based on the sources of Aedes and the Ministry of Higher Education (MOHE) species breeding habitats. To employ ECI, more Malaysia are also duly acknowledged.

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References Ligia L. N. S. G., Ana P. L., Julio C. V., Aziz, A., Abdullah, R., Ibrahim, H. (2011). A Marylene B. A., V., G. V. (2013). Study of model of knowledge mapping in visualizing the distribution and abundance of the eggs the hotspot of dengue. In Open Systems of Aedes aegypti and Aedes albopictus (ICOS), 2011 IEEE Conference on (pp. according to the habitat and meteorolical 444-449). IEEE. variables, municipality of Sao Sebastiao, Sao Paulo State, Brazil. Parasites & Dom, N., Faiz Madzlan, M., Nadira Yusoff, S. Vectors, 6, 321 N., Hassan Ahmad, A., Ismail, R., Nazrina Camalxaman, S. (2016). Profile distribution Nazni, W. A., Lee, H. L., Wan Rozita, W. M., of juvenile Aedes species in an urban area of Lian, A. C., Chen, C. D., Azahari, A. H. Malaysia. Transactions of the Royal Society Sadiyah, I. (2009). Oviposition behaviour of of Tropical Medicine and Hygiene, 110(4), Aedes albopictus in temephos and Bacillus 237-245. thuringiensis israelensis-treated ovitraps. Dengue Bulletin, 33, 209-216. Gerusa G., Reinaldo S. S., Nildimar A. H., & Antonio Guilherme P. (2014). Pablo Manrique-Saide, Clive R. Davies, Paul G. Coleman and Azael Che-Mendoza. Condition of the household and peridomicile (2013). The risk of Aedes aegypti breesing and severe dengue: a case-control study in and premises condition in South Mexico. Brazil. Infection Ecology & Epidemiology, Journal of the American Mosquito Control 4, 22110. Association,337-345. Hasnan, S. N. A., Che-Dom, N., Abd-Latif, Z., & Paily K. P. Paily, K. Chandhiran, P. Vanamail, N. Madzlan, F. (2017). Surveillance of Aedes P. Kumar, P. Jambulingam. (2013). Efficacy mosquitoes in different residential types in of a mermithid nematode Romanomermis central zone of Shah Alam, Selangor. Asian iyengari (Welch) (Nematoda: Mermithidae) Pacific Journal of Tropical Disease, 7, 332- in controlling tree hole-breeding mosquito 340. Aedes albopictus (Skuse) (Diptera: Hayden, M. H., Uejio, C. K., Walker, K., Culicidae) in a rubber plantation area Ramberg, F., Moreno, R., Rosales, C., of Kerala. India Parasitology Research, & Janes, C. R. (2010). Microclimate and 112(3), 1299-1304 human factors in the divergent ecology Parasuraman B., & Radhakrishnan E. (2012a). of Aedes aegypti along the Arizona, US/ Study on the correlation of premises Sonora, MX border. EcoHealth, 7(1), 64-77 condition index and the presence of larvae Idris, F. H., Idris, A., Usman, S. N. (2013). of Aedes species mosquitoes in human Surendran, R. Ramasamy. Detection of dwellings of the Cuddalore district of Tamil Aedes albopictus pre-imaginal stages Nadu, India. Osong Public Health and in brackish water habitats in Brunei Research Perspectives, 3(1), 3-7. 7 Darussalam. Journal Vector Ecology, 38(1), Parasuraman B., & Radhakrishnan E. (2012b). 197-199. Study on the correlation of premises Leticia A., Nogueira, Leticia T., Gushi, Joao condition index and the presence of larvae E., & Miranda. (2005). Short report: of Aedes species mosquitoes in human application of an alternative Aedes species dwellings of the Cuddalore district of Tamil (diptera: culicidae) surveillance method Nadu, India. Osong Public Health and in Botucatu city, Sao Paulo, Brazil. The Research Perspectives, 3(1), 3-7. 7. American Journal of Tropical Medicine and Ramasamy, R., Ramasamy, S. N., Surendran, Hygiene, 309-311. P. J., Jude, S. Dharshini, M., & Vinobaba. (2011). Larval development of Aedes

Journal of Sustainability Science and Management Volume 16 Number 1, January 2021: 120-128 Fatin Azura et al. 128

aegypti and Aedes albopictus in peri-urban relationship between dengue vector larval brackish water and its implications for density and land-use using factor analysis transmission of arboviral diseases. PLoS and spatial ring mapping. BMC Public Neglected Tropical Diseases, 5(11), e1369 Health, 12(1), 853. Roberto C. P., Reginaldo R., and Farael M. F. Sumodan, P. K. & Sumodan (2013). Potential (2013). The use of the premise condition of rubber plantations as breeding source for index (PCI) to provide guidelines for Aedes Aedes albopictus in Kerala, India. Dengue aegypti surveys. Journal of Vector Ecology, Bull, 27, 197–198. 190-191. Tun-Lin, W., Kay, B. H., Barnes, A. (1995). Rozilawati, H., Zairi, J., and Adanan, C.R. The premise condition index: a tool for (2007). Seasonal Abundance of Aedes streamlining survey of Aedes aegypti. The albopictus in Selected Urban and Suburban American Journal of Tropical Medicine and Areas in Penang, Malaysia. Tropical Hygiene, 591-594. Biomedicine, 24(1), 83-94. Vezzani, D., Vezzani, A., Rubio, S. M., Saleeza S. N. R., Norma R. Y., and Sofian M. Velazquez, N., Schweigmann, T., Wiegand. (2011). Mosquitoes Larval Breeding Habitat (2005). Detailed assessment of microhabitat in Urban and Suburban Areas, Peninsular suitability for Aedes aegypti (Diptera: Malaysia. World Academy of Science, Culicidae) in Buenos Aires, Argentina. Acta Engineering and Technology, International Trop, 95(2), pp. 123-131. Journal of Biological, Biomolecular, Wan-Norafikah O., Chen C.D., Soh H.N., Lee Agricultural, Food and Biotechnological H. L., Nazni W. A., Sofian- Azirun M. Engineering, 5(10), 599-603. (2009). Surveillance of Aedes mosquitoes Sarfraz, M. S. Sarfraz, N. Tripathi, T. Tipdecho, in a university campus in . T. Thongbu, P. Kerdthong, M. Souris. Malaysia. Tropical biomedicine, 26(2), (2012). Analyzing the spatio-temporal 206-215.

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