Improving Awareness and Transmission Risk Reduction Related To Japanese Encephalitis in Endemic Region of Mon State Myanmar
Mya MM, Win AYN, Mon POo, Thaung S, Tin Oo and Wai KT
Published on: 2022-08-20
Abstract
Japanese encephalitic (JE) is one of the public health problems in Myanmar. It is a zoonotic disease caused by JE virus spreading to human through the bite of Culex mosquitoes. The study was conducted in Khalock Kanine village, Mu Kawe village, Anout Ward and Toe Cheat Ward in Chaung Sone Township and Abaw village, Chaung Taung Village, Shwe Pyi Thar Ward and Aung Metter Phyo Ward in Ye Township in Mon State from September 2019 to October 2020, where JE suspected cases were reported. 50 houses each was randomly selected from each village and ward near with the pig farm. Mosquitoes were collected in all selected houses and pig farms using WHO sucking tubes. Result found that JE main vector Cx. tritaeniorhynchus was abundantly collected in all study areas. The JE vector density was higher in Chaung Sone than Ye Township. The highest number of JE vector was found n=1188 in Khalock Kanine village followed by n=1069 Toe Cheat Ward in Chaung Sone Township and n=1032 in Adawe village in Ye Township, and lowest was observed n=715 Mu Kawe village. Although suspected vectors such as Cx,vishnui and Cx. gelitus were abundantly found in all selected areas. Filarial vector Cx. quinquefasciatus was highest n=228 in Abaw village followed by n=279 in Chaung Taung Village followed by 229 in Abaw village and lowest was observed 67 in Anout Ward. Small number of Anopheles mosquitoes were collected. Culex tritaeniorhynchus larvae were abundantly found in rice field water and polluted water pools and creeks. Highest density of main vector Cx tritaeniorhynchus and suspected vectors Cx. vishnui and Cx.gelidus were found in both Chaung Sone and Ye Townships areas. Pig are main host of JE virus, Cx tritaeniorhynchus adult and larvae were abundantly collected in pig farms, polluted water pools, creeks and rice fields in all selected villages and wards JE suspected cases and JE cases are available in both areas. Over 95% of the populations known JE transmission is occurred by the biting of JE infected mosquitoes in night time. For the prevention of JE over 80% of population reported that sleeping in mosquito nets, burning mosquito coils, used spray and vaccination to human for prevention of mosquito bite. Over 80% of population known most susceptible age group was under 5 years old children. Over 90% of the villagers knew the mosquitoes were bred in polluted water. Attitude of half of the respondents was satisfactory for all items asked. Practices were relatively good. Study recommended that modified agriculture practices, pig vaccination, rigorous monitoring, vector control, and improved living standards can reduce morbidity of JE cases This study provides further information on risk of JE transmission in study areas. Environmental and ecological factors are responsible for the spread of JE virus. Therefore VBDC need to distribute LLINs nets and health education to all family members to prevent JE transmission in village and wards.
Keywords
Japanese encephalitic; Virus; Cx. tritaeniorhynchus; Vector; Transmission; Human; MosquitoesIntroduction
Japanese Encephalitis (JE) is a zoonotic disease caused by Japanese encephalitis virus (JEV). JEV exists in a transmission cycle between mosquitoes, pigs and/or water birds and is transmitted to humans through bites from infected mosquitoes of the Culex species (mainly Culex tritaeniorhynchus) [1]. JE usually presents as acute encephalitis syndrome (AES) and is confirmed by serology. JE is a disease of public health importance as billions of people are at risk of getting infected by JEV and children below 15 years are more susceptible [1,2]. A systematic review reported that 67 900 clinical cases of JE occur annually in 24 Asian and western Pacific countries despite widespread availability of vaccine, with approximately 13 600 to 20 400 deaths. While the overall incidence of JE is 1.8 per 100 000 per year in endemic countries, it is 5.4 among 1 to 15 years old children [3] . The infection can lead to severe complications with high case fatality. There is no specific treatment till date. However, this disease can be easily prevented by protection from mosquito bite, mosquito control and safe and effective vaccination [1]. Vaccination is the most effective form of prevention. A 30-year retrospective study conducted in Taiwan concluded that the vaccine had an estimated effectiveness of 97% against disease incidence, 98% against disease mortality in adult and 19.3% in decreasing the fatality of confirmed JE in 1 to15 year old children [4].
To date, threats of JE outbreaks are mostly found in 27 countries in Asia and the Pacific Regions including Myanmar. In 1974, Myanmar reported its first outbreak of JE and in 2014, there was an outbreak in 46 villages of nine townships of Rakhine State coupled with lack of awareness of JE transmission and prevention among the villagers [4,5]. As JE is endemic in many parts of Myanmar, the existence of source, vectors and seed virus outbreak can occur at any time. Cases reported were slightly higher in rural population than in urban population. Simultaneously, VBDC implements awareness raising activities to improve alertness but there are limitations. Department of Public Health indicated a total of 491 JE cases occurred in the whole country especially from Yangon, Bago, Tanintharyi and Ayeyarwady Regions and Kayin, Rakhine and Shan States and suspected cases in Mon State [6]. In Dawbon Township, Yangon Region JE virus infection was detected in 52.1% of pigs. The known JEV vector mosquito species, especially Culex tritaeniorhyncltus, were found in the study area but no concurrent human JEV infection were elicited [7]. In Myanmar, isolates of virus from pigs in Dike U pig farm were identified as genotype III by PCR and isolates from pig blood sample from Thakayta Township were found to be Genotype I by DNA sequencer [8,9]. An investigation on JEV infection in Bogalay Township was done in 1999. Findings showed that JEV antibodies were detected in 33% of the pigs. They also found the Culex vector mosquitoes especially Culex vishnui and Culex tritaeniorhynchus. JE virus antibodies were not detected among the villagers during the study [10].
In Myanmar, Culex tritaeniorhynchus is the main JE vector [11]. In 2012, there were only 14 confirmed JE cases which increased to 151 in 2015 and more than 380 in 2016 and 2017 [12]. Yangon is the region with the highest JE burden [13]. Similar to national trends, the number of JE cases (both acute encephalitis syndrome and laboratory confirmed positive JE) in Yangon has been on a rise since 2012. In Mon State, suspected JE cases were reported in Chaung Zone and Ye Townships in 2013 to 2015 where most of the household has one to two or 2 above pigs were cultured under the house or beside the households, some people has big pig farm has 10 to 20 CP pigs are available per household. And also JE suspected case were reported annularly [14].
Adequate knowledge and positive perception of JE are important for adoption of preventive measures [15]. In addition, high coverage of JE vaccine in populations at risk of disease is required to reduce the JE cases even when the virus remains in circulation in other hosts because human is a dead-end host [3]. A study done in one township in north Shan state in Myanmar showed the level of awareness on JE and its vaccine was low but the perception was generally positive [16]. The vaccination coverage was 93% among 391 study participants.
Little is known about community’s (especially parents/guardians of children) awareness regarding JE and JE vaccine and JE vector proportion in Yangon and other States and Regions which bears the highest JE burden in the country. This data alongside with the vaccination coverage data of the children may help regional vector borne disease control (VBDC) programme and expanded programme on immunization (EPI) under the Department of Public Health, Ministry of Health and Sports, so that they can develop a new coordinated strategic plan to successfully reduce JE transmission in endemic regions.
Out of four major strategies for JE prevention and control (health education, vector control, immunization of people and pigs and epidemic preparedness and response) guided by World Health Organization, Southeast Asia Regional Office (WHO/SEARO), In Myanmar, after JE vaccination in national immunization program for children starting from September 2017. However, community has poor understanding about the interplay of human health, animal health, changing agricultural practices, environment and socio-economic factors, and health care infrastructure. There is a need to focus disease prevention by mitigating the transmission risk through improvement of the awareness raising programs and risk reduction actions by incorporating health concept in rural areas of vulnerable sites in Myanmar. Therefore, the study planned to determine the vector bionomics of Culex species, responsible for Japanese encephalitis transmission and knowledge of JE in household members in 4 villages each of Chaungzone and Ye Townships in Mon State.
Materials and Methods
Study Design: A cross-sectional descriptive study design was used.
Study Population: Mosquitoes, pig farmers, household members of villages, village authority persons and health staff from rural health centers were included in the study.
Study Area and Study Period: Four villages each from Chaung Zone and Ye Townships in Mon State were selected. The selection is based on the 2012-2016 data of JE cases reported. The study was done from September 2019 to October 2020.
Sample Size Determination and Sampling Procedure
Assuming that the prevalence of community awareness of JE in each township being 10% with 6% precision at 95% CI, the sample size was 97 » 102 per Township considering for 5% non-response rate Multistage sampling procedure was used. Total 2 RHCs were selected. Two villages were selected from each RHC, one village that reported JE cases was selected purposively and one was by random selection. From each village, 50 persons who keep pigs in their household (pig farms) were randomly recruited. Therefore, this study covered two RHC areas, four villages and 200 pig farmers in each Township. Purposive sampling was done to recruit the villagers for one focus group discussion (FGD) per village amounting to four FGDs. For each FGD, 7-10 participants were selected. For key informant interviews (KII), one BHS, one health volunteer and one village authority were selected per village, totaling 12 respondents each. For entomological surveys, breeding sites and vector density were sought in all selected villages. The occurrence of JE vectors and its breeding sites and density were measured in four villages each of Chaung Sone and Ye Townships Mons State. From Khalock Kanine RHC, Khalock Kanine and Mu Kawe village and from Anout RHC, Anout Ward and Anout Toe Cheat Ward in Chaung Sone Township and also from Abaw RHC, Abaw village and Chaung Taung Village, and from Shwe Pyi Thar RHC, Shwe Pyi Thar Ward and Aung Metter Phyo Ward in Ye Township were selected to do research. Khalock Kanine village and Anout Ward in Chaung Sone Township and Abaw village and Shwe Pyi Thar Ward in Ye Towhship had high density of Pig farms (80-90% of Pig farms) and Mu Kawe village and Anout Toe Cheat Ward in Chaung Sone and Chaung Taung village and Aung Metter Phyo Ward in Ye Township had low density of pig farm (40% to 50% of pig farms). Therefore, the study covered 2 RHC, 4 villages, and 200 pig farmers in each Township.
Data Collection Methods
Mosquitoes were collected from fixed mosquito catching stations between pig farms and human dwellings of both field areas of Khalock Kanine RHC and Anout RHC in Chaung Sone Township and Abaw RHC and Shwe Pyi Thar RHC in Ye Township, using kanda big mosquito nets (330 x 330 x 180 cm) (K-net) for animal bait and CDC light traps method was used for indoor and outdoor mosquito collection and pig farms collection in the selected eight villages of both Townships. Mosquito catching in pig farms, cow sheds and big animal bait mosquito nets according to, WHO sucking tubes was conducted from 18:00 to 06:00 hours of the next day and morning resting collection was done in 5 houses/village at 06:00-07:00 hours for 5 days [17]. Mosquito resting behavior and feeding behavior were recorded.
Resting Place: resting mosquitoes were searched in indoor and outdoor of the household and pig farms and cow sheds.
Larva collection:For identification of breeding sites, larval surveys was conducted in polluted water sources such as brick kilns, ponds, paddy fields domestic wells, stream/creeks and all different types of water holding places, marshes around the irrigation ditches in paddy fields, hyacinth vegetation and water pools in and around three kilometers radius from the study site, by 3 dips/water holding place with WHO dipper [17]. The captured larvae and pupae were put in labeled plastic bags and brought back to the laboratory for species identification and colonization.
Identification of Mosquitoes: Collected adult mosquitoes and adults emerged from larva survey were identified by species according to different identification key [18-20].
Susceptibility Test: susceptibility test of Culex adult mosquitoes was done with deltamethrin 0.05%, permethrin 0.75% and cyfluthrin 0.15% using WHO test kits [21].
Data Analysis: Data from various sources were triangulated for meaningful interpretation. Larval density was calculated by larvae/dip and percentages were computed for adult mosquito density per village by Excel software. Epi data were calculated in percentage by Excel software.
Results
Table 1: Prevalence of JE vector, secondary vector and other mosquito species in 4 areas of Chaung Sone Township.
No. |
Species |
Chaung Sone Township |
|||||||||
Khalock Kanine RHC |
Anout RHC |
||||||||||
Khalock Kanine village |
Density |
Mu Kawe village |
Density |
Anout Ward |
Density |
Toe Cheat Ward |
Density |
Total |
Density |
||
1 |
Cx. tritaeniorhenchus |
1188 |
39.9 |
715 |
32.5 |
756 |
52.98 |
1069 |
33.17 |
3728 |
37.93 |
2 |
Cx. vishnui |
984 |
33 |
552 |
25.1 |
229 |
16.05 |
385 |
11.95 |
2150 |
21.87 |
3 |
Cx. gelidus |
217 |
7.28 |
337 |
15.3 |
115 |
8.06 |
1512 |
46.91 |
2181 |
22.19 |
4 |
Cx. quinquefasciatus |
73 |
2.45 |
129 |
5.87 |
67 |
4.7 |
73 |
2.26 |
342 |
3.48 |
5 |
Cx. fuscocaphala |
18 |
0.6 |
66 |
3 |
31 |
2.17 |
43 |
1.33 |
158 |
1.61 |
6 |
Mansonia |
361 |
12.1 |
253 |
11.5 |
72 |
5.05 |
39 |
1.21 |
725 |
7.38 |
7 |
Armegeris |
25 |
0.84 |
47 |
2.14 |
37 |
2.59 |
15 |
0.47 |
124 |
1.26 |
8 |
An. barbirostris |
19 |
0.64 |
37 |
1.68 |
57 |
3.99 |
43 |
1.33 |
156 |
1.59 |
9 |
An. vagus |
49 |
1.64 |
25 |
1.14 |
39 |
2.73 |
25 |
0.78 |
138 |
1.4 |
10 |
An. hyrcanus |
47 |
1.58 |
37 |
1.68 |
24 |
1.68 |
19 |
0.59 |
127 |
1.29 |
Total |
2981 |
100 |
2198 |
100 |
1427 |
100 |
3223 |
100 |
100 |
100 |
Simulation Procedure: Excited Surface Plasmon
Figure 1: Mosquito densities in KhalockKanine RHC( KhalockKanine, Mu Kawe villages) and Anout RHC (Anout Ward, Toe Cheat Ward) in Chaung Sone villages.
(Table 1) and (Figure 1) shows that highest number of main JE vector Cx. tritaeniorhynchus was found n=1188(39.85%) in Khalock kaine village followed by n=1069(33.17%) Toe Cheat ward and lowest was observed 715(32.53%) in Mu Kawe village in Chaungsone Township. Secondary vector Cu.vishnui was found highest number n=984(33.01%) in Khalock Kaine village followed by n= 552(25.11%) Mu Kawe and lowest was found n=229(16.05%) in Anout ward. Cx. quinquefasciatus was collected in highest number n=129(5.87%) in Mu Kawe village followed by n=73(2.45%) in Khalock Kanine village and n=73(2.26%) in Toe Cheat ward. Other species as Mansonia was found 361(12.11%) in Khalock Kanine and followed by 253(11.51%) in Mu Kawe village lowest was observed 39 (1.21%) in Toe Cheat ward. An.barbirostris An vagus and An.hyrcanus were collected in small number.
Table 2: Occurrence of JE vector, secondary vector and other mosquitoes were collected in selected 4 areas in Ye Township.
Ye Township |
|||||||||||
Abaw RHC |
Shwe Pyi Thar RHC |
All total |
|||||||||
No. |
Species |
Abaw village |
Density |
Chaung Taung Village |
Density |
Shwe Pyi Thar Ward |
Density |
Aung Metter Phyo Ward |
Density |
Total |
Density |
1 |
Cx. tritaeniorhenchus |
1032 |
40.84 |
997 |
38.52 |
823 |
46.24 |
787 |
44.21 |
3639 |
40.42 |
2 |
Cx. vishnui |
504 |
19.94 |
247 |
9.54 |
175 |
8.3 |
229 |
12.87 |
1155 |
12.83 |
3 |
Cx. gelidus |
457 |
18.08 |
773 |
29.87 |
726 |
34.42 |
325 |
18.26 |
2281 |
25.33 |
4 |
Cx. quinquefasciatus |
228 |
9.02 |
279 |
10.78 |
78 |
3.7 |
126 |
7.08 |
711 |
7.9 |
5 |
Cx. fuscocaphala |
33 |
1.31 |
13 |
0.5 |
30 |
1.42 |
47 |
2.64 |
123 |
1.37 |
6 |
Mansonia |
25 |
0.99 |
49 |
1.89 |
79 |
3.75 |
65 |
3.65 |
218 |
2.42 |
7 |
Armegeris |
54 |
2.14 |
84 |
3.25 |
49 |
2.32 |
30 |
1.69 |
217 |
2.41 |
8 |
An. barbirostris |
67 |
2.65 |
55 |
2.13 |
36 |
1.71 |
48 |
2.7 |
206 |
2.29 |
9 |
An. vagus |
31 |
1.23 |
18 |
0.7 |
36 |
1.71 |
15 |
0.84 |
100 |
1.11 |
10 |
An. hyrcanus |
24 |
0.95 |
30 |
1.16 |
23 |
1.09 |
43 |
2.42 |
120 |
1.33 |
11 An. maculatus |
72 |
2.85 |
43 |
1.66 |
54 |
2.56 |
65 |
3.65 |
234 |
2.6 |
|
Total |
2527 |
100 |
2588 |
100 |
2109 |
100 |
1780 |
100 |
9004 |
100 |
Figure 2: Mosquito densities in Abaw RHC( Abaw, Chaung Taung villages) and Shwe Pyi Thar RHC (Shwe Pyi TharWard, Aung Metter Phyo Ward) in Ye Township.
(Table 2) and (Figure 2) shows that in Abaw village highest number of Je vector Cx. trytaeniorhynchus was found n=1032(40.84%) followed by Cx vishnui n=504 (19.94%) and lowest was observed n=24 (0.95%) An.hyrcanus in Abaw village. In Chaung Taung village the highest number of JE vector of Cx. tritaeniorhynhus was found n=997(38.52%) followed by Cx. gelidus 773(29.87%) and lowest was found 13(0.50%). In Shwe Pyi Thar ward, the highest number of main JE vector Cx. tritaniorhynchus was found highest number n=823 (46.24%) and follow by Cx. gelidus n=726(34.42%) and lowest was observed An. Hyrcanus n=23(1.09%). In Aung Metter Phyo ward,main vector Cx.tritaniorhynchus was found highest number n=787(44.21%) followed by Cx. gelidus n=325 (18.26%) and lowest was observed An. vagus n=15(0.84%). In overall data observed that the highest number of main vector Cx.tritaeniorhynchus was found highest number 3639 (40.42%) followed by Cx, gelidus n=2281(25.33%) and lowest was found 100(1.11%) of An vagus.
Table 3: Breeding sites and collection of primary and secondary vectors of JE in selected areas in Chaung Sone and Ye Townships.
No. |
Type of water holding places |
Chaung Sone Township |
Ye Township |
Total collected |
|||||||||||||||||||||||||||||
Khalock Kanine RHC |
Anout RHC
|
Abaw RHC |
Shwe Pyi Thar RHC |
|
|||||||||||||||||||||||||||||
Khalock Kanine village |
Mu Kawe village |
Anout Ward |
Toe Cheat Ward |
Abaw village |
Chaung Taung village |
Shwe Pyi Thar Ward |
Aung Metter Phyo Ward |
Total |
% Density |
||||||||||||||||||||||||
|
Tr |
Vi |
Tr |
Vi |
Tr |
Vi |
Tr |
Vi |
Tr |
Vi |
Tr |
Vi |
Tr |
Vi |
Tr |
Vi |
Tr |
Vi |
Tr |
Vi |
|||||||||||||
1 |
Pond |
8 |
5 |
13 |
8 |
7 |
3 |
1 |
3 |
0 |
0 |
1 |
2 |
0 |
0 |
3 |
3 |
33 |
24 |
2.15 |
2.06 |
||||||||||||
2 |
Rice field |
97 |
73 |
35 |
31 |
54 |
67 |
88 |
76 |
34 |
45 |
96 |
75 |
93 |
77 |
36 |
43 |
533 |
487 |
34.68 |
41.84 |
||||||||||||
3 |
Creeks |
5 |
3 |
7 |
9 |
6 |
1 |
0 |
0 |
5 |
9 |
5 |
1 |
2 |
2 |
5 |
8 |
35 |
33 |
2.28 |
2.84 |
||||||||||||
4 |
Irrigation ditches |
23 |
12 |
34 |
17 |
28 |
15 |
38 |
26 |
12 |
16 |
37 |
24 |
15 |
11 |
23 |
25 |
210 |
146 |
13.66 |
12.54 |
||||||||||||
5 |
Water pools |
89 |
76 |
85 |
34 |
75 |
24 |
77 |
64 |
47 |
23 |
88 |
54 |
97 |
75 |
91 |
72 |
649 |
422 |
42.23 |
36.25 |
||||||||||||
6 |
Brick kilns |
0 |
0 |
3 |
5 |
7 |
3 |
18 |
7 |
23 |
12 |
17 |
12 |
4 |
2 |
5 |
11 |
77 |
52 |
5.01 |
4.47 |
||||||||||||
|
|
222 |
169 |
177 |
104 |
177 |
113 |
222 |
176 |
121 |
105 |
244 |
168 |
211 |
167 |
163 |
162 |
1537 |
1164 |
100.0 |
100.0 |
Tri = Cx.tritaeniorhynchus Vi = Cx.vishnui
Figure 3: Breeding sites and collection of primary and secondary vectors of JE in selected areas in Chaung Sone and Ye Townships.
(Table 3) and (Figure 3) shows that highest number of main vector Cx. tritaeniorhynchus and secondary vector Cx. vishnui were collected in water pools (n=649) and (n=422), followed by rice field (n=533) and (n=487) and lowest was observed in pond (n=33) and (n=24). Other species as Anopheles and Cx. quinquefasciatus were found small number in water wells. In Chaung Sone Township the highest number of main vector Cx. tritaeniorhynchus (n=222) was collected in Khalock Kanine village and Toe Cheat Ward followed by (n=177) from Mu Kawe village and Anout ward. In Ye Township the highest number of main vector of JE was collected from Chaung Taung village (n=244) followed by Shwe Pyi Thar Ward (n=211) and lowest was observed in Abaw village(n=121). Of these the highest number of larvae were collected n=97 from rice field followed by Water pools n=89 and lowest was observed 5 from Creeks in Khalock Kanine village. Rice fields and water pools were found favorable for mosquito breeding source and found high number of main vector Cu.tritaeniorhynchus larvae were collected, of this over 90 larvae were collected from Khalock Kanine village(n=97) , Chaung Taung village(n=96) and Shwe Pyi Thar Ward 93. In addition, in Water pools over 90 larvae were collected from Shwe Pyi Thar Ward (n=96) and Aung Metter Phyo Ward (n=91) and below 90 to 80 number of larvae were collected from Khalock Kanine village (n=89), Chaung Taung village (n=88) and Mu Kawe village (n=85).
Table 4: Insecticide susceptibility status of JE vector and secondary vector collected from four villages.
Species |
Chaung Sone Township |
Ye Township |
WHO Test Kits |
Remarks |
||||||
KKV |
MKV |
AW |
TCW |
AV |
CTW |
SPTW |
AMPW |
|||
Cx. tritaeniorhenchus |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
Deltamethrin 0.05%, Permethrin 0.75% Cyfluthrin 0.15% |
Susceptible |
Cx. vishnui |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
||
Cx. gelidus |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
||
Cx. quinquefasciatus |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
||
Cx. fuscocaphala |
18 |
30 |
30 |
30 |
30 |
13 |
30 |
30 |
||
Mansonia |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
||
Armegeris |
30 |
30 |
30 |
15 |
30 |
30 |
30 |
30 |
||
An. barbirostris |
19 |
30 |
30 |
30 |
30 |
30 |
30 |
30 |
||
An. vagus |
30 |
30 |
30 |
30 |
30 |
18 |
30 |
15 |
||
An. hyrcanus |
30 |
30 |
30 |
19 |
24 |
30 |
23 |
30 |
||
An. maculatus |
0 |
0 |
0 |
0 |
30 |
30 |
30 |
30 |
Table 4) shows that insecticide susceptibility status of JE vector Culex tritaeniorhynchus and secondary vector Cx. vishnui and other collected Culex and Anopheles mosquitoes from Chaung Sone and Ye Townships were found susceptible to WHO recommended Deltamethrin 0.05%, Permethrin 0.75%, Cyfluthrin 0.15% insecticides.
(Table 5) Indoor and outdoor resting behavior of main vector Cx. tritaniorhynchus and secondary vector Cx. vishnui in Chaung Sone and Ye Township.
Table 5: Indoor and outdoor resting behavior of main vector Cx. tritaniorhynchus and secondary vector Cx. vishnui in Chaung Sone and Ye Township.
Population in 5 houses (n) |
Species |
Chaung Sone Township |
Ye Township |
|||||||||
Indoor |
Outdoor |
Indoor |
Outdoor |
|||||||||
Mean indoor resting mosquitoes/ house |
Mosquito bite /man /hour |
Mean outdoor resting mosquitoes/ house |
Mosquito bite /man /hour |
Population |
Mean indoor resting mosquitoes/ house |
Mosquito bite /man /hour |
Mean outdoor resting mosquitoes/ house |
Mosquito bite /man /hour |
|
|||
36 |
Cx. tritaniorhynchus |
46.5 ±3.63 |
1.32 |
13.45 ±0.74 |
0.38 |
37 |
40.4 ±1.68 |
1.12 |
5.95 ±0.36 |
0.16
|
|
|
Cx. vishnui
|
48.4 ±2.39 |
1.37 |
12.05 ±1.06 |
0.34 |
29.6 ±2.71 |
0.82 |
3.9 ±0.12 |
0.10
|
|
(Table 5) shows that Indoor and outdoor resting behavior of main vector Cx. tritaniorhynchus and secondary vector Cx. vishnui in Chaung Sone and Ye Township were found higher in indoor than in outdoor. Mean indoor resting mosquito/ house of Cx. tritaniorhynchus (46.5±3.63 ) and Cx. vishnui (48.4±2.39) were higher in Chaung Sone than 40.4±1.68 and 29.6±2.71 in Ye Townships. Mosquito bite /man /hour of Cx. tritaeniorhynchus and Cx. vishnui were found higher 1.32 and 1.37 in Chaung Sone than 1.12 and 0.82 in Ye Townships. Mean outdoor resting mosquitoes/house and Mosquito bite /man /hour of Cx. tritaeniorhynchus (13.45±0.74 and 0.38) and Cx. vishnui (12.05±1.06 and 0.34) in Chaung Sone were also found higher than Mean outdoor resting mosquitoes/house and Mosquito bite /man /hour of Cx. tritaniorhynchus (5.95±0.36 and 0.16) and Cx. vishnui 3.9±0.12 and 0.10 in Ye Township. The ratio of indoor against outdoor resting of both Cx. tritaeniorhynchus and Cx. vishnui were found 3.46 and 4.02 in Chaung Sone and 6.79 and 7.59 in Ye Townships respectively.
According to resting behavior revealed that both Culex mosquitoes were endophagic and morning resting behavior revealed that both mosquitoes were found more endophagic and endophilic than exophagic and exophilic. Both mosquitoes were found higher in indoor than outdoor, it means that both are indoor biter.
Figure 4: Biting behavior of main vector Cx. tritaeniorhynchus and secondary Cx. vishnui on different hosts.
(Figure 4) shows that highest number of Cx. tritaeniorhynchus and Cx. vishnui bite to cattle (485±5.43 and 267±5.67) in Chaung Sone and 451±4.74 bite to cattle and 141±3.33 bite to pig in Ye Township followed by pig (426±1.58 and 256±4.33) in Chaung Sone and 443±3.67 bite to pig and 136±3.33 bite to cattle and lowest was observed (21±1.58 and15±0.67) bite to human in Chaung Sone and (16±0.71 and 12±1.00) bite to human in Ye Township.
According to biting preferance of both mosquitoes, Cx tritaeniorhynchus and Cx. vishnui like to bite cattle and pig than human. The biting rates of Cx. tritaeniorhynchus and Cx. vishnui were found 23.1 and 17.8 fold higher on cattle and 20.29 fold and 17.07 fold higher on pig than on human in Chaung Sone. And 28.19 and 11.33 fold higher on cattle and 27.69 fold and 11.75 fold higher on pig than on human in Ye Township. According to biting preference revealed that Cx. tritaeniorhynchus and Cx. vishnui were observed as anthrophophilic mosquitoes.
Biting rates of both Cx. tritaeniorhynchus and Cx. vishnui were observed 2.67 bites/hour and 3.5 bite/hour on human, 10.17bite/hour and 15.83 bite/hour on cattle and 9.33 bite/hour and 7.5 bite/hour on pig, respectively.
A total of 200 members each were interviewed, 181 members from Chaung Sone and 187 members from Ye Townships answered all questions in this study, comprising 85(46.96%) male and 96(53.04%) female from Chaung Sone and 78(41.71%) male and 109(58.29%) female in Ye. Concerning their education level, 84( 46.41%) and 81(43.32%) were primary school, 56( 30.94%) and 58(31.02%) were middle school, 24(13.26%) and 29(15.51%) were high school, 11(6.08%) and 11(5.88%) were graduates and 6(3.32%) and 8(4.28%) were illiterates in the study areas of Chaung Sone.and Ye Township.
The primary source of hearing the news of JE was television 101(55.81%) and 135(72.19%), radio 57(31.49%) and 71(37.97%), poster 23(12.71%) and 37 (19.79%) and health staff 166(91.71%) and 178(95.19%) in Chaung Sone and Ye Townships.
For the transmission of JE, the community members answered that the transmission was occurred from the pigs 145(80.11%) and 155(82.89%), water birds 21(11.60%) and 27(14.44%) and cows 15 (8.29%) and 5(2.67%) respectively in Chaung Sone and Ye Townships,
The most susceptible hosts for the transmission of JE in Chaung Sone and Ye Townships were under five years old children 145(80.11%) and 153(81.82%), 5-15 years old children 157(86.74%) and 168(89.84%) and pig farmers 64(35.36%) and 74(39.57%).
For the transmission of JE, household members mentioned that it was from the bite of infected mosquitoes at night time (106, 58.56%) and (133, 71.12%), day time (24,13.26%) and (12, 6.42%), close contact with pigs (51, 28.18%) and 42(22.46%) in Chaung Sone and Ye Townships.
Knowledge about breeding site of Culex mosquito was high; 167(92.27%) and 179(95.72%) said to polluted water pools and some said to clear water 14(7.74%) and 8(4.27%) in Chaung Sone and Ye Townships.
For the symptoms of JE, severe headache 104(57.46%) and 132(70.59%), high fever 96(53.04%) and 109(58.29%), fits 78(43.09%) and 88(47.06%) and loss of consciousness 67(37.02%) and 79(42.25%) were observed in Chaung Sone and Ye Townships.
For the JE prevention in in Chaung Sone and Ye Townships, 174(96.13%) and 182(97.33%) members answered and found different prevention methods, as sleeping in mosquito nets 163(90.06%) and 177(94.65%), burning mosquito coil 98(54.14%) and 114(60.96%), using insecticide spray 98(54.14%) and 78(40.64%) and vaccination to human 145(80.11%) and 173(92.51%) respectively were observed. For the removal of JE vectors, respondents answered spray or fumigation 162(89.50%) and 179(95.72%), removal of garbage dump 58(32.04%) and 44(23.53%) and larvicides 123(67.96%) and 143(76.47%), respectively in Chaung Sone and Ye Townships.
Discussion
Pig are through to represent the most significant host in the supply of JE virus in blood for infection of feeding mosquitoes. Although generally asymptomatic, there is clear evidence that JEV infection in pigs causes measurable viraemia [22]. Japanese encephalitis virus is transmitted to humans through bites from infected mosquitoes of the Culex species (mainly Cx. tritaeniorhynchus). Humans, once infected, do not develop sufficient viraemia to infect feeding mosquitoes [23] .
Present study of JE vectors surveillance in Chaung Sone and Ye Townships in Mon State, found high numbers of pig farms were available in Khalock Kanine village and Anout Ward in Chaung Sone Township and Abaw village and Shwe Pyi Thar Ward in Ye Township. High density of Je vector Cx. tritaeniorhynchus are found in all study areas although highest in 1188 in Khalock Kanine village in Chaung Sone and 1032 in Abaw village in Ye Township followed by 1069 in Toe Cheat Ward in Chaung Sone and 997 in Chaung Taung Village in Ye Township and lowest was observed in Mu Kawe village in Chaung Sone and Aung Metter Phyo Ward in Ye Township. Most Cx. tritaeniorhynchus mosquitoes were found in morning resting collection in pig farms and highly bite in night time when pigs were sleeping. High number of main vector Cx. tritaeniorhynchus and secondary vector Cx vishnui were collected in night time catch in Pig farms and Cow sheds and also morning resting collection was observed under the plastic sheets and cloths in pig farms and Cow sheds than human dwelling Same results has been found in Letpadan Township, Bago Region [24].
Culex tritaeniorhynchus larvae were abundantly collected in polluted water pools with vegetative and rice fields in all selected villages. Other researchers revealed that main JE vector Culex tritaeniorhynchus breeds predominantly in rice fields and open sunlit temporary and permanent habitats with vegetation was agreed with the present study and they have average flight range of 1.5 kilo meters [24-26]. A South Korean researcher revealed that Cx. tritaeniorhynchus is a main vector of JE in South Korea27. Although in India researcher observed that Cx. tritaeniorhynchus, Cx. vishnui, Cx. seudovishnui, Ma. annulifera Ma. indiana An. barbirostris. And An.subpictus were found JE virus positive by PCR method [28].
Secondary vectors Cx. vishnui were found in high density in adult collection. Other species Cx. quinquefasciatus, Cx. gelidus, Cx. fuscocaphala, Mansonia, Armegeris species and some Anopheles species as An. vagus, An. barbirostris, An.hyrcanus were collected in both Chaung Sone and Ye Townships except An.maculatus was collected from Ye Township by different collection methods. The natural hosts of the Japanese encephalitis virus are pigs, birds, not humans, and many people, therefore, believe the virus will never be completely eliminated [26]. In a study in South Korea, the Japanese encephalitis virus was presented in Cx. bitaeniorhynchus mosquitoes [27].
Many species of Culex mosquitoes can transmit JE. For Southern Asia, Eastern Asia, and Southeastern Asia, the main vector of JE is Cx. tritaeniorhynchus. In Myanmar Cx. tritaeniorhynchus is a main vector of JE and Cx. vishnui is a secondary vector of JE. A study of JE in Bago in Myanmar revealed that main vector and Secondary vector Cx vishnui adult were abundantly collected on pig body and pig farms and their larvae were abundantly collected from rice fields and polluted water pools in lapdon Township Bago Region was agreed with the present study [24]. For Northern Australia, the main vector is Cx. annulirostris. However, various other secondary vectors may be important [29]. Vectors observation study in India revealed that Culicine mosquitoes, mainly Cx. vishnui group (Cx. tritaeniorhynchus, Cx. vishnui and Cx. seudovishnui), are the major vectors of JE in different parts of India. In Anopheles group as An. barbirostris An. paeditaeniatus and An. subpictus isolates and Mansonia group as Ma. annulifera Ma. indiana and Ma. uniformis isolates were found JE virus positive [28]. Culex vishnui groups are present in many countries of South-East Asia and usually found in rural rice-growing and pig-farming regions of Asia as well as at the outskirts of cities in close proximity to human populations [30,31].
Indo resting behavior of Cx. triteaniorhynchus and Cx. vishnui were found higher in indoor than outdoor the ratio of indoor and outdoor were found 3.55:1 for Cx. triteaniorhynchus and 4.11:1 for Cx. vishnui. The biting rates of both Cx. tritaeniorhynchus and Cx. vishnui were observed highest on cattle followed by pig and lowest on human in Chaung Sone although in Ye Township. Culex tritaeniorhynchus and Cx. vishnui were observed anthrophophilic mosquitoes. Other researcher revealed that Cx. vishnui subgroup is very common and widespread and are primarily outdoor resting in vegetation and other shaded places but they may also rest indoors in summer [32]. In the present study, morning resting collection was found higher in indoor than in outdoor i.e. 3.796:1 ratio which means both mosquitoes were more endophagic and endophilic than exophagic and exophilic, and both were mostly rested under the hanging clothes and plastic sheet on the wall, on the moist wall in dark areas, under the baskets, in the opening bags and moist dark place. Same result of resting behavior of both Cx. tritaeniorhynchus and Cx. vishnui were found in a JE vectors study in Bago Region [24].
Both Culex mosquitoes are principally cattle feeders, though pigs and human feeding were also recorded in Chaung Sone. In Ye Township Cx. tritaeniorhynchus mosquitoes were found the same as above cattle feeder followed by pig and lowest feeding was observed on human although Cx. vishnui was found pig feeder than cattle and human but not highly difference feeding on between pigs and cattle in Ye Township. This observation of feeding on pig is not agreed with previous study in Bago Region and Ayeyawady Region [24]. Pig farms were found very close to human dwelling and some pig farms were situated beside, back and under the houses. It is a high risk to transmit JE infection to children and adult. Aung Zaw Hlatt and his party revealed that some pigs blood sample in Thakeyta Township Yangon Region and in Dikeoo Township, Bago Region were detected JE virus positivity by PCR methods [8-10]. Pig are considered to be the most important amplifying host, providing a link to humans through their nearness to housing [33]. In Chaung Sone and Ye Townships, suspected JE case’s houses were found very close to pig farms and polluted water pools and rice fields where plenty of Cx. tritaeniorhynchus and Cx. vishnui larvae. Maung Maung Mya and his associates observed that most of the JE positive cases available houses were situated very close to pig farms which were 2-3 meters away from houses and some pig farms were situated under the high houses in Bago Region [24].
Community-based educational interventions have been shown to affect understanding and involvement in mosquito control and vector-borne disease prevention [34,35]. A researcher from India revealed that an 87% reduction in mosquito density could be achieved for a per capita cost using community education for vector control [36].
In the present study, primary JE vector Cx. tritaeniorhynchus and secondary vector Cx. vishnui mosquitoes were found susceptible to deltamethrin 0.05, permethrin0.75% and cyfluthrin 0.15%. It means that JE vectors can be controlled by LLINs nets. A population based case-control study in China found that use of insecticide treated nets was associated with significant reduction in JE cases [37]. In another observation in Assam, India, a sharp reduction in JE zero-conversion rates in people and pigs was achieved when insecticide-treated nets were used in both people and pigs [38]. Deltamethrin impregnated long lasting insecticidal nets (LLINs) prevent men vector contact effectively in malaria endemic areas and 100% restricted to entrance the mosquito nets when sleeping in LLINs nets [39].
The knowledge about mosquitoes was found high percentage of 92.27% in Chaung Sone and 95.72% in Ye Townships respondents knew about breeding site of C ulex mosquitoes, was highly bred in polluted water pools and rice fields. A study from India observed that knowledge about breeding site of mosquito was poor (36.9%) in their study [40]. Higher awareness level about breeding place (50%), it was not agreed with the present study due to in present study found high level of knowledge about the breeding sources of both main and secondary JE vectors of Culex mosquitoes [41]. But not agreed with another study from Karnataka had observed low level of knowledge about breeding site of mosquitoes [42]. Researcher had physically verified the water drainage condition of dwelling in the present study. Most of the houses were found unsatisfactory due to polluted water pools were getting behind the house. These were the potential breeding site for mosquitoes and they never removed this polluted water pools although they knew stagnant water could be a potential breeding site for mosquitoes. They prefer to breed in rice fields, and outbreaks of Japanese encephalitis are commonly associated with intensive rice cultivation [43]. Service mentioned that main vector of JE breeds in water with luxuriant vegetation mainly in paddy fields and the abundance is related to rice cultivation, shallow ditches and pools [44].
Japanese encephalitic risk factors were common across pig farms and farm families in all villages in both Townships but there were differences in levels of knowledge and practices of villagers related to JE risk reduction. The findings of the study showed that there were good attitude and practices regarding about JE in local population, 91.71% and 95.19% of respondents from both Chaung Sone and Ye heard about JE from health staff followed by from television 55.80% and 72.19%. Earlier studies reported that radio TV and newspapers as most important sources of knowledge. Similar, finding (54%) was reported in Nepal in 2012 at Rupandehi District [45-48]. A KAP study from Malwa district on mosquito-borne disease among students revealed that only 6.5% were aware that JE is a mosquito-borne disease [46]. In the present study, the community members well knew that JE transmission occurred by the biting of mosquitoes and 58.56% and 71.12 of the respondents from Chaung Sone and Ye Townships mentioned that JE was infected by mosquito bite at night time and some said as close contact with pigs. The community members thought that the transmission of JE was mainly from the pigs and small number of members said as birds and cows. Same JE transmission result has been found in Bago Region [24].
Most of the people from Chaung Sone and Ye Townships answered the most susceptible host to the transmission of JE was under five years old children and 5-15years children. Most of the respondents could not correctly identify the typical sign and symptoms of JE, most members said as severe headache and high fever and these results agreed [40]. For the prevention of JE transmission in human being, 96.13% from Chaung Sone and 97.33% from Ye of the participants said as sleeping under the mosquito nets and some mentioned burning coil and spraying insecticide although 80.11% and 92.51% of the members from Chaung Sone and Ye Townships believed JE vaccination to human was the effective control method. Most of the members from both study areas mentioned that spraying or fumigation with larvicides were most suitable for removing JE vectors and some people said removal of garbage dump. people were using one or more methods of personal protective measures against mosquito bite [48]. Most common was repellent followed by mosquito net. Our study contradicts these findings because the use of mosquito net was most common (90.06% and 94.65%) in Chaung Sone and Ye Townships followed by vaccination 80.11% and 92. 51%, other members answered that insecticide sprays and mosquito coil which are agreed with the results of JE study in rural areas of Uttar Pradesh, India [40].
In the present study, Culex mosquito’s larvae were abundantly present in stagnant water pools and in rice field water and also knowledge of respondents about breeding site of Culex mosquito was high (92.27% and 95.72) from Chaung Sone and Ye Townships. Yadav and Ahmad and his party revealed that only 36.3% of households agreed that stagnant water can be a potential breeding site for mosquitoes [40]. A similar study from Pondicherry reported the collection of stagnant water in 70% of households49. This type of community perception favors mosquito breeding in their areas [49]. Same results have been found in Labadon Township in Bago Region [24].
Risk Factor
In both areas, pig farms, mosquito breeding sources as rice fields and polluted or stagnant water pools are situated very close to human dwelling (5-15 meters). In each village, 20 to 50% of the households have 1-20 pigs in one to two pig farms and 90% of the pig farms are open type. Main JE vector breeding sites as polluted water pools, creeks, gutters and rice fields are situated in and beside the villages and also Culex larvae were abundantly presented. Most of the villagers and their family members have not used mosquitoes net when they go to sleep. All the human dwelling are situated within the flight range of JE vector (1.5 Kilo meter).
Conclusion
Japanese Encephalitis is rising throughout Asia, because epidemics are typically noticed only after outbreaks. This study helps not only to improve the awareness of JE in the community but also to reduce the transmission risk and to fill the knowledge gaps of stakeholders and community members to implement an integrated one health approach at village level in high risk endemic regions. Pigs are main host for JE virus, Cx. tritaeniorhynchus adult and larvae were abundantly collected in polluted water pools and rice fields in all selected villages. Old and new JE history was available villages. Implementation of a vaccination program for young children, as well as modified agricultural practices, pig vaccination, rigorous monitoring, vector control, and improved living standards can reduce the number of JE cases. This study provides further information on risk of JE transmission in study areas. Environmental and ecological factors are responsible for the spread of JE virus. Therefore, the study recommended that VBDC need to provide LLINs nets and health education to all family members to prevent JE transmission in villages.
Acknowledgements
The authors are thankful to the Ministry of Health and Sports for supporting the IR grant to do this research. We would like to thank Dr. Zaw Than Htun Director-General, Department of Medical Research for permission to do research. We also thank the staff of Medical Entomology Research Division, Department of Medical Research for providing financial support over the many fruitful years of entomological research.
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