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RESEARCH ARTICLE
Year : 2022 | Volume
: 59
| Issue : 2 | Page : 139-144
The effectiveness of MyMAT Aedes mosquito trap in reducing dengue cases
Mohd Khadri Shahar1, Suzilah Ismail2, Rohani Ahmad1, Topek Omar3
1 Medical Entomology Unit, Institute for Medical Research, National Institute of Health, Ministry of Health, Malaysia
2 School of Quantitative Sciences, Universiti Utara Malaysia, UUM Sintok, Kedah, Malaysia
3 Disease Control Division, Ministry of Health, Malaysia
Correspondence Address:
Suzilah Ismail
School of Quantitative Sciences, Universiti Utara Malaysia, UUM Sintok, Kedah
Malaysia
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/0972-9062.335727
Malaysia Mosquito Autocidal Trap (MyMAT) is a green technology Aedes mosquito trap that does not use harmful chemical substances. This study aimed to evaluate the efficiency of MyMAT in reducing dengue cases and relating the cases to rainfall. An experimental field study was conducted for 42 weeks at Pangsapuri Nilam Sari, Shah Alam, Selangor. A total of 624 MyMAT was allocated at four blocks: inside each apartment and outside at the corridors in each level. Mosquito and rainfall data were collected weekly using MyMAT and a mobile rain gauge, respectively. The dengue cases data was retrieved from the e-dengue system obtained from the Malaysia Ministry of Health. The findings showed that MyMAT could catch 97% of Aedes mosquitoes and reduced dengue cases on average of 78%, indicating MyMAT is a reliable Aedes mosquito trap. Interestingly the findings also revealed a significant relationship between dengue cases, the number of Aedes mosquitoes, and rainfall. This week notified dengue cases increased when last two weeks mosquitoes increased due to previous two weeks rainfall increment. Thus indicating an indirect but significant relationship between this week notified dengue cases with the last four weeks rainfall. These relationships can be used in establishing a dengue outbreak forecasting model, which can act as an early warning system.
Keywords: Malaysia Mosquito Autocidal Trap; MyMAT; green technology; dengue cases; rainfall
Dengue is a deadly vector-borne disease that has been spreading at an alarming rate for decades[1],[2]. In tropical and sub-tropical nations, it has become one of the most frequent public health issues[1],[3],[4]. Dengue outbreaks and cases have increased dramatically in recent decades in many parts of the world, including Africa, the Americas, Southeast Asia, Europe, the Eastern Mediterranean, and the Western Pacific[1],[5]. According to a report on the global distribution and burden of dengue, approximately 390 million dengue infections are recorded each year, with the number of clinically manifested dengue-infected persons ranging from 67 to 136 million[6].
Interactions between individuals, mosquitoes, viruses, and environmental variables cause dengue transmission[5]. Dengue virus (DENV) is transmitted to human through bites of infective female Aedes mosquito. DENV infection causes a variety of clinical states, including mild asymptomatic dengue fever (DF), severe dengue haemorrhagic fever (DHF), and dengue shock syndrome (DSS), all of which can be fatal[7],[8].
DF has been documented in Malaysia since 1902, with the first case of DF being identified in Penang[9] and the first case of DHF being reported in Penang in 1962[10]. Dengue fever has been on the increase in Malaysia since the late 20th century. In recent years however Malaysia recorded a downward trend in dengue cases and deaths caused by dengue. Annual dengue cases dropped by 20%, 17%, and 2.87% in 2016, 2017, and 2018, respectively. Except for 2019, the number of dengue cases has been rising about 61% from 2018[11]. In the absence of specific treatment or extensive, effective immunization, the prevention and control of dengue relies primarily on reducing the population of Aedes mosquitoes to interrupt virus transmission[7],[12]. Limited success has been achieved using conventional vector control methods to prevent dengue transmission. Integrated control programs, including alternative tools, may provide greater potential for monitoring and reducing dengue vector populations[7],[8],[12],[13].
The mosquito breeds in both natural and artificial containers showed an opportunistic feeding behavior on a wide range of hosts[14]. Oviposition trap, also known as ovitrap, has been an important tool for detecting and monitoring Aedes populations. The ovitrap can be modified to render it to be lethal to either the immature or adult populations of Aedes. The addition of a larvicide or autocidal mechanism allows long-term use of the ovitrap with minimal risk of the device becoming a productive source of adult mosquitoes[13]. Ovitrap can also be modified to collect gravid females by incorporating an adhesive surface, also known as sticky ovitrap. Adult mosquitoes collected in the sticky ovitraps may be identified by morphology in the field, thus providing a faster and more direct measure of adult abundance. In addition, gravid female mosquitoes can be processed for the detection of pathogens and/or identification of host blood meal[13].
A sticky autocidal trap named Malaysia Mosquito Autocidal Trap (MyMAT®), [Figure 1] & [Figure 2], has been applied in high dengue cases in residential areas in Malaysia. It was reported to be successful in trapping both the males and females of Aedes aegypti, Aedes albopictus and Culex quinquefasciatus[12],[15]. In addition, the traps could catch gravid females attracted to lay eggs, with an impact on dengue transmission evident from the decreasing trend of reported dengue cases in a large scale trial at the residential area[15]. Therefore, in this study, the effectiveness of this green technology, MyMAT, in trapping Aedes mosquitoes was further explored in relation to dengue cases and rainfall.
Figure 1: MyMAT and its components; A. Main body of MyMAT cylindrical plastic container, B. Floater with mesh netting, C. Sticky ring, D. Funnel with filter, E. Skrew cap cover with holder, F. Sachet containing 30 mg Bti of 3000 ITU. Material & Methods This experimental field study was conducted at Pangsapuri Nilam Sari, Section 7, Shah Alam Selangor. The apartments consisting of 7 blocks (52–58) [Figure 3] & [Figure 4]. There are two clusters where Cluster 1 containing Blocks 52, 53, 54, and 55, while Cluster 2 comprising of Blocks 56, 57, and 58. Cluster 1 practiced self-cleaning by residents in their apartments, but Cluster 2 has regular cleaning services hired by the residents. This location was selected due to high dengue cases for three consecutive years. The past reported number of dengue cases was similar among the blocks in each cluster. However, there were different numbers of dengue cases, where Cluster 1 has higher dengue cases than Cluster 2. This unique characteristic of natural groupings of the two clusters added a valuable experimental condition in this study. [Figure 4] displays the location of MyMAT according to the blocks in each cluster; a total of 132 apartments per block. There are 6 levels in each block. The ground level consists of 12 apartment units and a parking space. Level 1 until 5 comprises 24 apartment units at each level. One MyMAT was allocated inside each apartment and four MyMAT outside along the corridor for each level, thus a total of 156 MyMAT per block. Two blocks from each cluster were selected to allocate the MyMAT; Block 52 and 54 in Cluster 1 and Block 57 and 58 in Cluster 2 [Figure 4]. A total of 624 MyMAT were allocated at the four blocks for 42 weeks. A weekly adult mosquito data was collected by identifying species and counting the number of mosquitoes caught on the sticky ring of MyMAT. The water and sticky ring in MyMAT were replaced weekly. Rainfall data was also collected weekly using a mobile rain gauge located in the middle of the two clusters. The dengue cases data was retrieved from the e-dengue system obtained from the Malaysia Ministry of Health.
Ethical statement
Community consent was obtained beforehand from all selected study sites. This study was approved by Medical Research & Ethics Committee, Ministry of Health, Malaysia (NMRR-13-947-17794).
Results & Discussion[Figure 5] displays the number of mosquitoes caught by MyMAT according to species and blocks. Aedes aegypti was the highest (average of 56%), followed by Aedes albopictus (average of 41%) and Culex (average of 3%). This indicated that MyMAT was able to catch 97% of Aedes mosquitoes. The findings also showed that there was a significant difference in the number of Aedes mosquitoes caught based on the clusters where Cluster 1 has higher percentages (57%) as compared to Cluster 2 (43%) although the same number of MyMAT was allocated at both clusters. This was perhaps due to regular cleaning services conducted in Cluster 2, which may have contributed to fewer mosquitoes in that area. This result also shows that proper or routine cleaning activities do help in reducing the number of mosquitoes compared to improper cleaning area. There was also a significant difference within Cluster 1, where Block 52 has slightly higher percentages (52%) than Block 54 (48%). However, there was no significant differences within Cluster 2 (Block 57 and 58). Overall, MyMAT was able to catch 12838 (97.4%) Aedes mosquitoes of both species and 340 (2.6%) of Culex quiquefasciatus using 624 traps for 42 weeks. A similar finding was obtained by Malijan[16] when MyMAT was set up at the school perimeter, canteen, and toilets for eight weeks that managed to trap 614 (91.6%) Aedes mosquitoes and 56 (8.4%) of Culex species. In the school setup, they do not report any Aedes aegypti compared to the apartment environment in this study which has trapped 7,381 (57%) of Aedes aegypti and 5457 (43%) of Aedes albopictus. Mohd Farihan et al.[17] also reported high percentages of Aedes mosquitoes caught using MyMAT where 77.5% (6960) were Aedes aegypti, and 22.5% (2018) were Aedes albopictus when the trap was located inside and outside housing areas.
Figure 5: Number of mosquitoes according to species and blocks using MyMAT.[Figure 6] displays notified dengue cases based on blocks with and without MyMAT. The Chi-Square test indicated that the notified dengue cases percentages were significantly different for Overall, Cluster 1 and Cluster 2. The percentages of notified dengue cases were smaller when MyMAT was located at the blocks. Therefore, it shows the effectiveness of MyMAT in reducing notified dengue cases.
[Table 1] presents the mean of notified dengue cases. The T-test indicated significant differences in the mean dengue cases with and without MyMAT for Overall, Cluster 1 and Cluster 2. Blocks with MyMAT have smaller mean dengue cases. The percentages of mean dengue cases reduction for Overall, Cluster 1 and Cluster 2 were 77%, 68%, and 88%, respectively. The average effectiveness of MyMAT was 78% in reducing the dengue cases. Cluster 1 and 2 also show significant differences in the mean dengue cases, and percentages difference of the mean reduction for both clusters was 20%. This finding indicated that notified dengue cases were reduced 20% more in Cluster 2 and perhaps this was due to the regular cleaning services conducted.
[Figure 7] shows the relationship between Aedes mosquito and rainfall. There was a strong significant correlation (0.833) between them, as indicated by the circles in the graph. The number of mosquitoes for this week increased due to the increment of past two weeks rainfall (an average minimum of 3 millimetre and above). This finding is supported by several previous studies that have found a significant association between rainfall and Aedes population in determining dengue outbreaks[18],[19],[20]. A high amount of rainfall has been discovered to influence mass egg hatching, resulting in an increase in mosquito population abundance[21]. Meanwhile, Rohani et al.[18] has recorded that a minimum rainfall of 0.1 inches (2.54 millimetre) has been enough to drive the number of larvae. Earlier rainfall was reported to have a significant influence on mosquito-viral transmission in general[22],[23], as well as adult lifespan[22].
[Figure 8] shows the relationship between Aedes mosquito and notified dengue cases. There was a quite strong significant correlation (0.747) between them, as highlighted by the circles in the graph. This week notified dengue cases increased based on the increment of last two weeks Aedes mosquitoes, and as explained earlier in [Figure 7], the number of Aedes mosquitoes for this week increased when the last two weeks rainfall increased. This revealed an indirect but significant strong relationship (correlation 0.840) between this week notified dengue cases and the last four weeks rainfall, where the increment of the last four weeks rainfall influences the increment of this week notified dengue cases. Similarly, moderate correlations were reported by Rohani et al.[20] between this week notified dengue cases and last four weeks rainfall. Consequently, the current study suggests a better prediction for dengue vector population that has been increasing during a certain time, and it is critical for program managers, particularly those in endemic areas, to take rapid vector control precaution to prevent future dengue outbreaks.
ConclusionThe findings showed that MyMAT could catch 97% of Aedes mosquitoes and reduced dengue cases on average of 78%, indicating MyMAT is a reliable Aedes mosquito trap. Proper routine cleaning activities can significantly reduce Aedes mosquitoes and dengue cases in the study area. This study also revealed a significant connection between epidemiological (notified dengue cases), entomological (number of Aedes mosquito), and environmental (rainfall) factors, allowing for a better understanding of the connections between the three factors in dengue outbreaks. These relationships can be used to establish a dengue outbreak forecasting model that can act as an early warning system.
Conflict of interest: None
AcknowledgementsThe authors are grateful to the Director-General of Health, Malaysia for permission to publish this paper. We especially thanked the staff of Medical Entomology Unit of IMR, NIH and Selangor State Health Department without whose diligence and hard work under difficult field conditions this research would not have been accomplished. The study was funded by National Institutes of Health (JPP-IMR 13-057), Ministry of Health, Malaysia.
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