Susceptible status of temephos (1% sand granules) against dengue vector Aedes aegypti larvae. Aye Aye Myint, Thiha, Zaw Lin, Nay Yi Yi Lin (NMCP) & Bandi Tharpa (WHO) 47th Myanmar Health Research Congress Ministry of Health and sports 10th January, 2019

Introduction Dengue Haemorrhagic Fever (DHF) is one of the major public health problems in Myanmar. During 1968, sporadic DHF cases occurred in Yangon. Two years later, first outbreak had resulted in 1654 cases and 91 deaths in same place, Yangon. Since then, dengue becomes one of important leading causes of mortality among children. Highest case-load was 42,913 in 2015 and death, 444 in 1994. In 2017, 31288 cases & 192 deaths were occurred. Dengue Prevention and Control Program put efforts to reduce the number of cases and deaths since 1968. But, program encountered a lot of challenges. The program has used environmental manipulation & modification, biological and chemical measures including abate. The program has used massive abate treatment since 2008 (after Cyclone Nargis). Abate showed significant impact on reduction of entomological indices. But, as all chemical measures, program needs to assess sensitivity of abate to larvae of dengue vector. Therefore there is a need to study the susceptibility of the temephos sand granule formulation (1% active ingredient) against the larvae dengue vector. So, urgently needed to assess the susceptibility of abate to Aedes larvae of dengue vector in selected states and regions.

Reported Dengue Case & CFR in Myanmar (1970-2017) 31, 288 cases of Dengue/DHF were reported in 2017 192 persons died from DHF in 2017 Case fatality rate is 0.61% (below 1% of national target)

Objective To assess the susceptibility of temephos sand granules formulation (1% active ingredient)

Material & method (1) Larvae collection: There were five townships from Yangon regions and two townships from five States & Regions with the highest number of Dengue cases in Jan-June 2017 was choose. For each sampling site, 5 larval (Ae. aegypti) breeding places were collected. Ae.aegypti larvae were collected in the field and choose the larvae were late-third or early-fourth instars.

Aedes aegypti larvae were collected in the field Selecting the late 3rdstage and early 4th stage Aedes larvae

Larvae bioassay: The susceptibility of larvae to temephos (SDS Ramcides Crop science Pvt. Ltd., India) was assessed using standard WHO bioassays. Each bioassay were used 25 (late-third or early-fourth) instars in glass beaker with 99 ml of mineral water and 1 ml insecticide solution at the required concentration. Two different concentrations in the range of activity of temephos (0.5 ppm & 1 ppm) and 25 larvae per concentration with four replicates were used. Each bioassay included a control group which received 1 ml of ethanol. Tests were run at 27°C ± 2°C, and mortality was assessed every 15 minutes until 180 minutes (3 hours) and after 24 hour of insecticide exposure.

Weighting of Temephos 1% sand granules Screening of larvae before test Testing with Temephos 1% sand granules

Localities Six States and Regions includes: – (1) Yangon :- Hlaintharyar Shwepyithar, Insein, Bahan, Mayangone, (2) Ayeyarwaddy :- Pathein, Hinthada (3) Bago :- Bago, DeikU (4) Mon :- Mawlamyine, Mudon (5) Kayin :- Hpa-an, Hlainbwe (6) Rakhine :- Sittwe, Myinpyar

Sentinel sites of States and Regions

Results and Discussion

Conclusion According to results, 100% mortality was occurred after 24 hour in six States and Regions, therefore, temephos is still susceptible to Aedes larvae in these States & Regions. There were no difference between dosage of 0.5 ppm and 1ppm of temephos sand granules, causing 100% mortality of Ae.aegypti larvae in these states and regions. It was assumed that dosages of 0.5 ppm was also can be used and applied in larval control for Dengue. But practically, there are many factors in public used and so, should be used the recommended dosage of 1ppm.

Acknowledgement The study team wanted to show special gratitude to Dr. Zaw Lin, Deputy Director & Dr. Nay Yi Yi Lin, Deputy Director, National Malaria Control Program. Regional and township health departments of Yangon, Bago, Ayeyarwaddy Region and Mon, Kayin and Rekhine State. We wish to express our sincere thanks to all participants who contributed in the study.

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