Breeding Preference of Aedes Mosquitoes According To the Position of Water Storage Containers in Thanlyin Township, Yangon Region, Myanmar
Mya MM, Swe TT, Htun TM, Thew TL and Nyunt NOO
Published on: 2021-10-10
Abstract
Aedes mosquitoes are the major vector of dengue fever, dengue hemorrhagic fever and serious public health problem mainly in children population, prevention of DHF outbreaks in endemic areas is based on long term anti mosquito control measures. Breeding preferences of Aedes mosquitoes on the position of water storage containers as covered, uncovered, half covered, shade and open areas were measured in Amuehtan Ward, Thanlyin Township, Yangon from July, 2018 to June, 2019 using non-intervention descriptive field investigation method. Larval survey in the selected areas was carried out according to WHO. Aedes larvae positivity in all kinds of water storage containers (major, minor and miscellaneous) were detected and recorded according to their position. Breeding preference on Aedes larvae of uncovered, covered and half covered containers and shade and open areas placed containers were recorded. Result revealed that uncover containers were found the highest positivity rates, 66.67% in major containers, 95.24% in minor containers and 100% in miscellaneous containers respectively. Open and shade areas placed containers were found the highest larval positively rate was found in open area placed containers (54.92%), of this 58.33% of major and 92.86% of miscellaneous containers (larval positive) were placed in open area and 76.20% of minor containers (larval positive) were placed in shade areas. In key containers, the highest positivity rate 87.50% was found in uncovers containers and 62.50% of the key containers were placed in shade area. In key premises, the highest positivity rate was found 78.05% in uncovers containers and 58.54% of the containers were placed in shade area. Key containers and Key premises houses were found highly positive in uncovered containers which were situated in shade areas. Therefore, study suggested that all the water storage containers need to proper covered and placed open areas to reduce Aedes larval density and adult population.
Keywords
Positivity; Uncover; Cover; Half cover; Open; Shade; Key container; Key premisesIntroduction
There are three genera of mosquitoes. They are Aedes, Culex and Anopheles. Aedes aegypti is one of the world's most widely distributed mosquitoes and is of considerable medical importance as a vector of dengue fever, dengue haemorrhagic fever (DHF) and yellow fever [1]. Mosquito is prevalent world over especially between latitude 45° north and latitude 40 south and the tropic regions [2]. Especially in recent years, the distribution space of both mosquitoes and mosquito-borne disease has been changing and expanding for reasons such as increasing rates of environmental corruption, climatic changes, vector and pathogen resistance to insecticides and drugs, progressive urbanization and population movement [3]. Aedes aegypti is considered as the major vector of dengue fever, dengue haemorrhagic fever and dengue shock syndrome (DF, DHF, DSS) in many subtropical and tropical countries throughout the world. Prevention of DHF outbreaks in endemic areas is based on long term anti mosquito control measures particularly household and environmental sanitation with emphasis on larval source reduction. Only vector control promises permanency and a cost effective solution [4]. The breeding places of A. aegypti are almost entirely confined to artificial collections of water, small artificial collections of water; water receptacles of all kinds [5], artificial containers or things resembling these [6], any receptacle holding fresh water [7]. Such breeding places may be in the dwelling itself, for example the earthenware pots (chatties) or calabashes almost universal in native huts for storing water; anti-formicas, flower vases, neglected cups or jugs or other household collections of water in better-class houses. Or another type of breeding place about the house arises from defects or neglected features of the building itself, for example uncovered cisterns [8,9] roof gutters [10] in the masonry, traps of drains, or flush tanks or pans of water-closets when temporarily out of use. Aedes aegypti habit is more diurnal than nocturnal and is widely recognized in the tropics as the ‘day biting mosquito’. Nevertheless, it shows a marked preference for shade and dark corners and in general avoids bright light and open spaces. It will feed, however, readily in moderate or bright daylight at any time of the day. An estimate, 50 million people are at risk in dengue endemic countries [11]. In South East Asia and Western Pacific Regions, which bear nearly 75% of the current global disease burden due to dengue [12]. Dengue Fever and DHF are increasingly becoming serious public health problems in Myanmar especially among the 5-10 and 11-15 years old age groups and now noted 15 years above, a vast majority of the cases occur in 5-8 years old age group [13,14]. In Myanmar, the highest numbers of DHF cases were reported from Irrawaddy, Kachin, Magway, Mandalay, Mon, Rakkine, Sagaing, Taninthayi and Yangon regions [15]. Clinically recognizable DHF was first noticed in 1969 in Yangon Children's Hospital followed by the first epidemic in Yangon in the year 1970 [15]. High number of dengue hemorrhagic fever (DHF) transmission occurs during raining season from May to October. Water storage practices in Yangon city provide year round breeding opportunities for the vector. In States and Regions, Aedes breeding sites become established only in raining season when the locals store rain water for the domestic usages. Population growth and industrial installation in Thanlyin Township, Yangon Region is necessary accompanied by simultaneous urban development. Therefore, a considerable number of inhabitants living in over crowed peri-urban districts with unhygienic living conditions provide favourable breeding sites for mosquitoes. In drawing up strategies of Aedes control, it is essential that detail bionomic of the mosquito should be studied and clearly understood. As the DHF cases are correlated to the density of Aedes aegypti of the locality, factors influencing the seasonal abundance of the vector needed to be studied in detail. The present study was conducted with the following objectives; (1) to determine the prevalence of immature Aedes aegypti population in water storage containers in one ward of Thanlyin Township and (2) to investigate the larval indices, key containers and key premises of Aedes larvae as well as containers placing site, covered and without covered containers and coloured of the containers were recorded and calculated.
Materials and Methods
The present study was conducted in Amuehtan Ward, Thanlyin Township, Yangon Region from July, 2018 to June, 2019. It is situated between 96° 15¢ 5.38¢¢ East longitude and 16°45¢ 38.14¢¢ North latitude (Figure 1).
Figure 1: Location map of the study site (Source: from Google Earth, 2019).
Study design
The study was conducted using non-intervention descriptive field investigation method. Larva positive containers and types were recorded and compared with each other. The breeding sources were divided into major, minor and miscellaneous (Plate 2, 3, 4). Materials as bowl and cup, net sweeper, thermometer etc… were used in survey time (Plate 1).
Larval collection
Breeding preferences of Aedes mosquitoes on the position of water storage containers. Study conducted in Amuehtan Ward, Thanlyin Township, Yangon Region. Aedes larvae positive and negative containers in Amuehtan Ward were recorded according to covered, uncovered, half covered containers and placing position of the containers in shade and open areas were investigated and recorded. Larval survey in the selected area was carried out according to WHO, [2]. Percentage of Key containers (> 500 larvae/container) and Key premises (three and above positive containers/house) were calculated.
Species Identification: species Identification of adult mosquitoes collected from larval survey were done according to Rampa and Prachong, [16].
Data analysis: Collected data were calculated by according to covered, uncovered, half covered containers and placing position of the containers in shade and open areas and Key containers, Key premises.
Results
Larval positivity rates of Aedes mosquito larvae were carried out in Amuehtan Ward Thanlyin Township, Yangon Region according to uncover, cover and half cover containers and containers placing sites of open and shade areas from July, 2018 to June, 2019.
Table 1: Larval positivity rate according to uncovered, covered and half covered domestic water storage containers.
Container condition |
Major Container |
Minor Container |
Miscellaneous container |
Total containers |
|||||||
Ins. |
(+) Con.% |
Total (+) |
Ins. |
(+)Con. |
Total (+) |
Ins. |
(+)Con. |
Total (+) % |
(+) Con.% |
Total(+) Con. % |
|
Un covered |
75 |
24 |
66.67 |
164 |
20 (12.20) |
95.24 |
24 |
14 (58.33) |
100 |
263 (78.74) |
58 (81.69) |
Half covered |
45 |
10 |
27.78 |
11 |
1 (9.10) |
4.76 |
0 |
0 |
0 |
56 (16.77) |
11 (15.49) |
Covered |
12 |
2 |
5.56 |
3 |
0 |
0 |
0 |
0 |
0 |
15 (4.49) |
2 (2.82) |
Total % (+) |
132 |
36 |
100 |
178 |
21 (11.80) |
100 |
24 |
14 (58.33) |
100 |
334 |
71 |
Ins. Con.= Inspected container Total (+) %= Percentage of total positive container (+) Con. % = percentage of positive container
(Table 1) shows that a total of 334 water storage containers were investigated and found that 71(21.26%) of the e containers were Aedes larvae positive. Of this in major container, 132 containers were investigated and 36 (27.27%) containers were positives. In minor container, 178 containers were investigated and 21(11.80%) containers were positives. In miscellaneous container, 24 containers were investigated and 14(58.33%) containers were positives. The positivity rate was found in uncover containers of major 66.67%, minor 95.24% and miscellaneous 100% respective.
Table 2: Larva positivity rate according to place the containers open and shade areas.
Major Container |
Minor Container |
Miscellaneous container |
Total container |
||||||||
Places |
Ins.Con. |
(+)Con. % |
Total (+) % |
Ins.Con. |
(+)Con. % |
Total (+) % |
Ins.Con. |
(+)Con. % |
Total (+) % |
Total % |
Total (+) Con. % |
Open areas |
82 |
21 (25.61) |
58.33 |
52 |
5(9.62) |
23.80 |
19 |
13(68.42) |
92.86 |
153 (45.81) |
39 (54.92) |
Shade areas |
50 |
15(30.00) |
41.67 |
126 |
16(12.70) |
76.20 |
5 |
1 (20.00) |
7.19 |
181 (54.19) |
32 (45.07) |
Total |
132 |
36 (27.27) |
100 |
178 |
21(11.80) |
100 |
24 |
14(58.33) |
100 |
334 100 |
71 100 |
(Table 2) shows that larva positive rate in open areas was highest in Miscellaneous containers (92.86%) followed by major containers (58.33%) and lowest was observed 23.80% of Minor containers. In shade areas the highest percentage of containers were found 76.20% in Minor containers followed by Major containers 41.67% and lowest was found 1.19% of Miscellaneous containers respectively.
Table 3: Key containers: larva positivity rate on uncover, cover and half cover containers according to the placing areas.
Total |
|
Key Containers |
Placing areas |
||||
Inspected containers |
positive containers |
Total |
Un |
Half |
Covered |
Open area |
Shade area |
covered |
covered |
||||||
334 |
71 |
16 |
14 |
2 |
0 |
6 |
10 |
% Positivity rate |
21.26 |
|
87.5 |
12.5 |
0 |
37.5 |
62.5 |
(Table 3) shows that a total of 16 Key containers were found according to different placing areas in Amuehtan Ward. The highest positivity of Key containers was found 14 in uncovered containers followed by half covered containers and no Key containers were observed in covered containers. Higher percentage of Key containers were placed 10(62.50%) in shade areas than in open area placed containers (37.50%) in the study period.
Table 4: Key premises larva positivity rate on uncover, cover and half cover containers according to placing areas.
Total inspected houses |
Key premises |
|
Placing areas |
||||
Houses |
Positive Containers |
Uncovered |
Half-covered |
Covered |
Open area |
Shade area |
|
53 |
10 |
41 |
32 |
7 |
2 |
17 |
24 |
% positivity |
18.87 |
|
78.05 |
17.07 |
4.88 |
41..46 |
58.54 |
(Table 4) shows that a total of 10 Key premises were observed in 53 inspected houses in study area. In 10 key premises houses, 41 containers were found larvae positive. The highest larval positivity rate of different containers was found 78.05% in uncover containers followed by half covered containers 7(17.07%) and lowest was observed covered containers 2 (4.88%) and shade area placed containers were found higher positivity 24 (58.54%) than open area placed containers 17(41.46%).
Discussion
The mosquito Ae. aegypti is one of several species of the family Culicidae that are vectors of human pathogens. Among the most important human diseases caused by viruses are Dengue, and Urban Yellow Fever, both transmitted by the biting of Aedes mosquitoes. Aedes aegypti is the main vector of above viral diseases and Ae. albopictus is a secondary role. Also transmitted by this species of mosquito, the viruses Chihungunya and Zika have been severely affecting human populations over the last 3-5 years, mainly in South America [17]. Antiviral therapies for these diseases are currently unavailable of inaccessible by most of the population. Thus, strategies for vector control are the best alternatives to restrict the spread of these viruses [17]. Ae. Aegypti vector control is primarily directed against larval or adult stages. In the present study gravid Aedes aegypti mosquitoes laid their eggs in various manmade containers as major, minor and miscellaneous containers. Of this the highest investigated containers were minor containers but the highest positivity rate was found in major containers in Amuehtan Ward, Thanlyin Township. Other researchers revealed that major containers were highly Aedes larvae positivity in high density in metal drums, big Bago jars, concrete tanks, concrete jars in different parts of Shanchaung, Thakeyta, and Shwepyithar Townships in Yangon Region these results are agreed with the present study [18-20]. In the study area, manmade containers of nearly almost all the major, minor and miscellaneous containers were uncovered and the placing sites of the containers were found more of the containers were placed in open area than in the shade area except the minor containers, were high in shade area. In major containers, ten containers were covered but these containers were positive with Aedes larvae. It may be due to the fact that, lids of those containers were uncertain or uncovered the containers for a long time behind to use. And also half covered container two with positive. Same larval positive result has been found in covered and half covered big Bago jars and concrete jars in Thakeyta Township which were placed under the roof of the house (shade areas) [20]. In minor container, only one container was covered with larval positive. If the lids were uncertain, gravid females were laid in them. The highest positivity rate was found in uncover containers. The lowest positivity rate was found in half cover containers. Properly covered overhead tanks were found clean and no Aedes larvae positivity in water [18-21]. In containers placing site, all total of 153 containers were placed in open and 181 containers were placed in shade areas, of these high percentage of larvae positivity was found in Miscellaneous containers followed by major containers in open areas although in shade areas placed containers, the highest percentage of minor containers were positive for Aedes larvae followed by major containers and lowest was observed Miscellaneous containers. Although in Thakeyta Township in Yangon Region and Pakakku Township, Magway Region found that high number of major containers was found larvae positive in shade areas and high number of Miscellaneous containers were found Aedes larvae positive in open areas [20-22]. Study observed that uncovered Minor containers were more larvae positive in shade area and Miscellaneous containers were found more positive than major containers in open areas. In 16 key containers, 14 were uncovered and two were covered in the study area. So key containers of uncovered were more positive than the others. In 16 key containers, six containers were found in open area and ten containers were found in shade area. Result revealed that shade area placed containers were high density of Aedes larvae positivity than the open area placed containers. This results are agreed with the results of Hpa–a Township Kayin State by Maung Maung Mya and his party revealed that in this area most of the key containers were placed under the roof of the house for rain water collection, metal drums, plastic drums, big Bago Jars, Concrete jars, big plastic jars and big three hole or cribs (which were used for holding cow food) were highly larval positivity and which were key containers in Kayin State [23]. Although other researchers observed that metal drums, spirit bowls, Bago jars and concrete jars were observed key containers in Yangon Region [18-20,24]. In 10 key premises, total 53 houses were investigated and 10 houses were found 3 and above water storage containers positive with Aedes larvae. In 10 houses, total 41 containers were investigated and 32 (78.05%) were uncovered, 7(17.07%) were half covered and 2(4.88%) were covered. Therefore, uncovered containers were more larval positive than the others. And 17 (41.46%) containers were found in open area and 24 (58.56%) were found in shade area. Therefore, shade area containers were more larvae positivity than the open areas placed containers. Same results have been found in Shanchaung, Shwepyitha and Thakeyta, Townships in Yangon Region and Pakakku Township Magway Region [18-20,22].
Conclusion
Breeding preferences of Aedes mosquitoes on the position of water storage containers as covered, uncovered, half covered containers according to major, minor and miscellaneous containers which were placed in shade and open areas were measured in Amuehtan Ward, Thanlyin Township, Yangon. Larval survey in the selected areas was carried out according to WHO, 1996. Aedes larvae positivity in all kinds of major, minor and miscellaneous water storage containers were detected and recorded according to their position such as uncovered, covered and half covered as well as open and shade area placed containers. Result revealed that uncover containers were found the highest positivity rates, 66.67% in major containers, 95.24% in minor containers and 100% in miscellaneous containers respectively. The highest larval positively rate was observed in open area placed containers (54.92%), of this 58.33% of major and 92.86% of miscellaneous containers (larval positive) were placed in open area and 76.20% of minor containers (larval positive) were placed in shade areas. In key containers, the highest positivity rate was found 87.50% in uncovers containers and 62.50% of the key containers were placed in shade area. In key premises, the highest positivity rate was found 78.05% in uncovers containers and 58.54% of the containers were placed in shade area. Key containers and containers of Key premises houses were found highly positive in uncovered containers which were situated in shad areas. Therefore, study suggested that all the water storage containers need to proper covered and placed open areas to reduce Aedes larval density and adult population.
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