Page 1 of 7
British Journal of Healthcare and Medical Research - Vol. 11, No. 4
Publication Date: August 25, 2024
DOI:10.14738/bjhmr.114.17477.
Bhakdeenuan, P., Thavara, U., Sirisopa, P., Srivarom, N., Kunhachan, P., Khumsawad, C., Samaimai, S., & Tawatsin, A. (2024). Field
Evaluation of Sumilarv 2MR Efficacy Against Aedes aegypti Larvae in Water-Storage Containers in Thailand. British Journal of
Healthcare and Medical Research, Vol - 11(4). 302-308.
Services for Science and Education – United Kingdom
Field Evaluation of Sumilarv 2MR Efficacy Against Aedes aegypti
Larvae in Water-Storage Containers in Thailand
Payu Bhakdeenuan
National Institute of Health,
Department of Medical Sciences,
Muang, Nonthaburi 11000, Thailand
Usavadee Thavara
Department of Medical Sciences,
Muang, Nonthaburi 11000, Thailand
Patcharawan Sirisopa
National Institute of Health,
Department of Medical Sciences,
Muang, Nonthaburi 11000, Thailand
Navy Srivarom
Medical Science Technical Office,
Department of Medical Sciences,
Muang, Nonthaburi 11000, Thailand
Phanukit Kunhachan
National Institute of Health,
Department of Medical Sciences,
Muang, Nonthaburi 11000, Thailand
Chayada Khumsawad
National Institute of Health,
Department of Medical Sciences,
Muang, Nonthaburi 11000, Thailand
Srisuda Samaimai
Suan Dusit University,
Dusit, Bangkok 10300, Thailand
Apiwat Tawatsin
Medical Science Technical Office,
Department of Medical Sciences,
Muang, Nonthaburi 11000, Thailand
Page 2 of 7
303
Bhakdeenuan, P., Thavara, U., Sirisopa, P., Srivarom, N., Kunhachan, P., Khumsawad, C., Samaimai, S., & Tawatsin, A. (2024). Field Evaluation of
Sumilarv 2MR Efficacy Against Aedes aegypti Larvae in Water-Storage Containers in Thailand. British Journal of Healthcare and Medical Research,
Vol - 11(4). 302-308.
URL: http://dx.doi.org/10.14738/bjhmr.114.17477.
ABSTRACT
Vector-borne disease transmission by Aedes mosquitoes, including Dengue,
Chikungunya, and Zika fever, is estimated to increase massively worldwide. An
alternative strategy for disease control is to limit the vector populations by using a
larvicide. This study was initiated to evaluate the residual efficacy of a newly
developed larvicide, Sumilarv® 2 MR, against larvae of Aedes aegypti that thrive in
water-storage containers under simulated field conditions in Thailand. The
Sumilarv® 2 MR, a 5.5 cm diameter resin disc containing 2% (w/w) pyriproxyfen, was
used in this study against Aedes aegypti larvae in the simulated field trial method.
The discs were immersed in 40L, 80L, and 160L of tap water in water-storage
containers (1 piece/container); resulting in 3 different dosages of Sumilarv® 2 MR
treatment. The controls were immersed in similar containers filled with tap water
but without the disc. Five containers were used for each treatment and the controls.
Pupal skins in each containerwerecounted weekly, and the Emergence Inhibition Rate
(%IE) was calculated. For the field simulation, half the volume of water in each container
was removed weekly and replaced with new tap water for 114 weeks. During the 114
weeks of evaluation, average IE rates of 98.58% 1.73, 98.25% 2.20, and 97.94%
2.55 were observed in the 40L, 80L and 160L containers, respectively. There was
no significant difference (p>0.05) in residual efficacy among the three dosages used
in this study. Furthermore, the average %IE of all dosages was not less than 96.0%,
even at the lowest dosage (160-liter containers) until the last weeks of evaluation.
All dosages of Sumilarv® 2 MR in this study provided a high level of larvicidal
efficacy (almost 100 %IE) in a water exchange regimen for up to 2 years post- treatment. This could be an effective environmentally friendly device for
controlling Aedes aegypti larvae in water-storage containers.
Keywords: Sumilarv® 2 MR, Pyriproxyfen, Larvicide, Aedes aegypti, Field evaluation
INTRODUCTION
Diseases caused by arboviruses are one of the most important infections for human beings [1].
Over decades, the health burden of dengue fever, in terms of health and economic impact has
been enormously increasing worldwide. In the absence of an effective vaccine, controlling
mosquito vectors using various agents such as repellents, insecticides and larvicides were used
as the strategy to eradicate and prevent the disease outbreak. Aedes aegypti mosquito is known
as an important vector of Dengue and Chikungunya fever worldwide [2-3]. In Thailand, a large
number of Ae. aegypti breeding sites are still found due to the use of outdoor containers around
the houses to collect and store water. As the water is kept for domestic use, a larvicide used in
the container is an important alternative strategy for limiting vector populations and thus
preventing diseases. Insect growth regulators (IGRs) appear to be an advantage in mosquito
larval control, with a different mode of action such as mimicking the juvenile growth hormone
and chitin synthesis inhibitor, which prevent mosquito larvae from developing into
reproduction-capable adults [4]. Pyriproxifen (PPF) is the juvenoid broad-spectrum IGR, which
acts on the hormonal system of insects. It has been used worldwide as a pesticide and was
approved by the World Health Organization (WHO) for controlling mosquito vectors [5], due to
its excellent residual efficacy and much lower dose than other larvicides. Sumilarv® 2 MR is a
novel mosquito larval control product, based on the PPF, which has been evaluated as a safe
insecticide for application in drinking water [6-7]. It is contained in a small resin disc with slow- release technology for easy use in water storage [8]. The main objective of this study was to
Page 3 of 7
304
British Journal of Healthcare and Medical Research (BJHMR) Vol 11, Issue 04, August-2024
Services for Science and Education – United Kingdom
evaluate the residual efficacy of this newly developed larvicide against Aedes aegypti larvae in
water-storage containers under simulated field conditions in Thailand.
MATERIALS & METHODS
Study Area, Temperature Conditions, and Test Duration
This study was carried out at a field research station in Bang Bua Thong district, Nonthaburi
province, Thailand, to evaluate larvicidal products and other experimental agents for vector
control. Water jars were located under a roof. During this study, the ambient temperatures at
this site were between 24oC and 37oC. The ranges of minimum and maximum temperatures in
the jars were 22-29oC and 28-36oC, respectively. This study was carried out continuously for
114 weeks.
Mosquito Larvae
Laboratory reared 3rd instar larvae of Aedes aegypti used in this study were provided by the
National Institute of Health (NIH), Thailand. Larvae were reared at ambient temperature in a
round plastic tub filled with filtered non-chlorinated water and fed with ground mouse food.
Sumilarv2MR Treatment
The Sumilarv 2MR, developed by Sumitomo Chemicals Company, Japan, is a resin concave- shaped disc containing 2% (w/w) PPF. A Sumilarv 2MR disc was immersed into a water jar
filled with 40L, 80L, and 160L of tap water, respectively. Water jars in the control group were
filled with the same volume of water without placing the disc. Five replicates were evaluated
for each set. Then, each jar was covered with a lid to minimize water evaporation and
contamination of debris. The water jars were allowed undisturbed for a week.
Simulated Field Trial
Every week, a new cohort of third-instar Ae. aegypti larvae were used in testing. A total number
of 25 larvae were transferred into each jar, and one gram of ground mouse food was added as
larval food. As to the warm temperature in Thailand, mosquito larvae tend to develop quickly
within a week. Therefore, the adult emergence was observed after one week by counting the
pupal skins. After adults emerge from pupae, their skins are floated at the water surface and
can easily be aspirated with the transferable pipette. Then, the pupal skins were placed in white
plastic tray filled with water and counted. It is notable that as an effect of IGRs, the mosquito
mortality occurs at pupal stage. Therefore, pupal skins provide a good evaluation yield of
emerging inhibition of IGRs. After aspirated all pupal skins in each water jar, all of the remained
dead and alive immature mosquitoes were removed by using fishing net prior to replacing a
new cohort of Ae. aegypti larvae. After stirring the water, 50% of its volume was removed and
replaced with the same amount of tap water. The replacement of water and the new cohort of
Ae. aegypti larvae was carried out every week. All of the jars were covered with lids to prevent
the oviposition by wild mosquitoes and the invasion of predators.
Emergence Inhibition Rate & Data Analysis
The Emergence Inhibition Rate expressed as a percentage (%IE) is calculated based on the
number of larvae that did not develop into emerging adults, as compared to the initial number
of larvae added, as by the following formula [9-10]: