Predatory Efficiency of Larvivorous Fish against Mosquito Larvae in Different Water Temperature Levels: Implication in Control Measure of Dengue Vector.

Background: Reduction of the Aedes aegypti population is the priority effort to control dengue virus transmission including the use of larvivorous fish. Biologically, the predatory efficiency of fish will slow down when the water acidity and temperature change from normal conditions. This study aimed to determine the predatory efficiency of three species of larvivorous fish against the Ae. aegypti larvae in different water temperatures. Methods: Three well-known species of larvivorous fish namely Poecilia reticulata, Betta splendens, and Aplocheilus panchax were placed into 12 cm diameter jars with three water temperature ranges namely 20-21 °C, 27-28 °C, and 34-35 °C, and allowed to three days acclimatization. As many as one hundred 4th-instars larvae of Ae. aegypti were gradually entered into each jar, and a longitudinal observation was made at 5, 10, 30, 60, 120, 240, 360, 480, 600, and 720 minutes. The predated larvae were recorded. Results: In normal temperature ranges, the predatory efficiency of the larvivorous fish was 75%, 72.3%, and 32.8% for B. splendens. Aplocheilus panchax, and P. reticulata, respectively. The predation abilities decreased due to temperature changes. Betta splendens and A. panchax indicated the best predatory efficiency against Ae. aegypti larvae in different temperature conditions. Conclusion: Betta splendens is the best larvivorous fish in the lower to normal, but A. panchax is the best in the normal to higher temperature ranges. This finding should be considered by public health workers in selecting larvivorous fish to control the Dengue vectors.

Susceptibility of Aedes albopictus Larvae to the Larvicidal Activity of Three Types of Derris elliptica Extract.

<b>Background and Objective:</b> The methanol, ethyl acetate and n-hexane extracts of <i>D. elliptica</i> root have high larvicidal activity against <i>Aedes aegypti</i> larvae, the primary vector of dengue but have not been understood their potential against <i>Ae. albopictus</i> larvae, the secondary vector of dengue that also transmits Chikungunya and Zika viruses. This <i>in vitro</i> study aims to understand the larvicidal activity of the 3 extract types of <i>D. elliptica </i>root against <i>Ae. albopictus</i> larvae. <b>Materials and Methods:</b> The tuba root extract types were obtained from the sequential extraction process with 3 steps of liquid-liquid partition as described in the previous report. Six concentrations were occupied in this experiment ranging of 0.5, 1.0, 2.0, 4.0, 10.0 and 15.0 mg L¹ each concentration was 5 times replicated and placed in 250 mL plastic cups. As many as 20 of 3rd instar larvae of <i>Ae. albopictus</i> were subjected in each treatment cup and larval mortality was observed after 24 and 48 hrs of exposure. <b>Results:</b> Larval mortality rates based on concentration range of 13.75-97.00 and 43,75-100%, 14.00-44.00, 34.00-90.00%, 12.00-47.00 and 28.00-88.00%, with the LC₅₀ after 24 and 48 hrs of exposure were 2.925 and 0.414, 16.184, 2.900, 15.789 and 4.380 mg L¹, respectively for methanol, ethyl acetate and n-hexane extracts. <b>Conclusion:</b> The methanol, ethyl acetate and n-hexane extract of tuba root have high larvicidal activity against <i>Ae. albopictus</i> larvae. Further study on prototype formulation of larvicide and elucidation of the specific phytochemical compounds of the extracts were necessarily conducted.

Evaluation of Larvicidal Activity of Kaempferia galanga Extracts Against Aedes aegypti Larvae.

<b>Background and Objective:</b> The resistance of <i>Aedes aegypti</i> larvae against temephos become an obstacle in controlling the arboviral vector. This condition triggered researchers to investigate the larvicidal activity of phytochemical compounds that are effective, safe, biodegradable and eco-friendly from various medicinal plants. This study evaluated the larvicidal activity of <i>Kaempferia galanga</i> extracts against <i>Ae. aegypti</i> larvae. <b>Materials and Methods:</b> Four solvents with different polarities, namely ethanol, ethyl acetate, n-hexane and water were used in the sequential extraction. The final larvicidal bioassay test of the four extract types was designed in five replicates of five concentration ranges, namely 1.0, 8.75, 17.5, 35.0 and 70.0 ppm. A total of 20 3rd instar larvae of <i>Ae. aegypti</i> were contacted with each replicate in a plastic cup. Larval mortality and effective concentration of larvicide were calculated and determined after 24 and 48 hrs of exposure. <b>Results:</b> The average range of larval mortality according to the concentration of larvicide extracts of ethanol, ethyl acetate, n-hexane and water was 40-91, 2-36, 7-83 and 44-86% after 24 hrs and 88-100, 11-84, 12-99 and 77-100% after 48 hrs of exposure. The data yielded LC₅₀ for 24 and 48 hrs of exposure at 1,563 and 0.061 ppm, 206,739 and 7,623 ppm, 47,579 and 38,063 ppm and 1.33 and 0.300 ppm, respectively. <b>Conclusion:</b> The polar extract of <i>K. galanga</i> showed high effectiveness so it is necessary to design the right formulation for field application, potency stability and active period of this larvicide residue.

Larvicidal Activity of Ethyl Acetate Extract of Derris elliptica Root against the Third-Instar Larvae of Cypermethrin-Resistant Aedes aegypti Offspring.

BACKGROUND: Derris elliptica extracts have a high larvicidal potential against the laboratory strain of Aedes aegypti larvae, but the effect on offspring larvae of pyrethroid-resistant strains of the species is lack understood. This study aimed to determine the larvicidal activity of the ethyl acetate extract of tuba root against the third-instar larvae of the Cypermethrin-resistant Ae. aegypti offspring. METHODS: The experimental study occupied four levels of ethyl acetate extract of D. elliptica namely 10, 25, 50, and 100 ppm, and each level was four times replicated. As many as twenty of healthy third-instar larvae, offspring of Cypermethrin-resistant Ae. aegypti were subjected to each experiment group. Larval mortality rate and lethal concentration 50% subject (LC50) were calculated after 24 and 48 hours of exposure time. RESULTS: Mortality of larvae increased directly proportional to the increase of extract concentration. Larval mortality rates after 24 and 48 hours of exposure were 40-67.5% and 62.5-97.5%, and LC50 were 34.945 and 6.461ppm, respectively. CONCLUSION: The ethyl acetate extract of D. elliptica has the high effectiveness larvicidal potential against the third-instar larvae, offspring of the Cypermethrin-resistant Ae. aegypti. Isolation of the specific compound is necessarily done to obtain the active ingredient for larvicide formulation.

Effect of D-Allethrin Aerosol and Coil to the Mortality of Mosquitoes.

BACKGROUND: Commercial insecticides were widely used by communities to control the mosquito population in their houses. D-allethrin is one of insecticide ingredients widely distributed in two different concentrations namely 0.15% of aerosol and 0.3% of coil formulations. We aimed to understand the mortality of indoor mosquitoes after being exposed to d-allethrin 0.15% (aerosol) and 0.3% (coil) formulations. METHODS: This quasi-experiment study applied the posttest-only comparison group design. The aerosol and coil d-allethrin were used to expose the wild mosquitoes in twelve dormitory bedrooms of SMKN Jawa Tengah, a vocational high school belonging to Central Java Provincial Government, on March 2017. The compounds were exposed for 60 min to each bedroom with four-week interval for both of formulations. The knockdown mosquitoes were collected into a plastic cup and delivered to the laboratory for 24h holding, morphologically species identification and mortality recording. History of insecticide use in the dormitory was recorded by an interview with one student in each bedroom. Data were statistically analyzed with independent sample t-test and Mann-Whitney. RESULTS: As many as 57 knockdown mosquitoes belonging to three species were obtained namely Culex fuscocephala, Cx. quinquefasciatus and Aedes aegypti with mortality rate of 50.88% after 24h holding. Knockdown and mortality of mosquitoes were significantly different based on d-allethrin formulations. D-allethrin concentrations were not effective for controlling Culex mosquitoes but effective for Ae. aegypti. CONCLUSION: Further efficacy of d-allethrin 0.15% aerosol to eradicate Ae. aegypti is necessary to be conducted in supporting the Dengue vector control.

Impact of Dengue Surveillance Workers on Community Participation and Satisfaction of Dengue Virus Control Measures in Semarang Municipality, Indonesia: A Policy Breakthrough in Public Health Action.

OBJECTIVES: The aim of this study was to assess community participation in Dengue virus control measures, and community satisfaction in the Dengue surveillance workers (DSWs) performance in Semarang municipality after 3 years of empowerment. METHODS: A cross-sectional survey involved 1,018 selected participants from 12 groups of social roles in 141 villages in Semarang municipality, Indonesia. A direct interview was performed using a structured questionnaire to evaluate the acceptance, and satisfaction of the community towards the DSWs. The data were analyzed descriptively. RESULTS: The majority of the members of the community considered that the DSWs play an important role in reducing Dengue cases, and vectors of the Dengue virus, as well as increasing the community participation in Dengue control measures. The survey showed that DSWs performance, attitudes, and abilities regarding their main tasks were perceived to be good. CONCLUSION: Overall, people in Semarang municipality were satisfied with the performance of the DSWs, and considered them important enough to be maintained and strengthened in the future so that Dengue could be controlled. This new policy needs to be disseminated to other regions that may encounter the problems associated with Dengue virus.

Altitudinal distribution of Aedes indices during dry season in the dengue endemic area of Central Java, Indonesia

Aedes mosquitoes, mainly Aedes aegypti and Aedes albopictus, are the primary and secondary vectors of dengue viruses in Indonesia, with transmission occurring by sucking blood. The density of the vectors is influenced by season and rainfall, but limited by altitude. The aim of the study is to describe the density and distribution of dengue vectors during the dry season based on the altitudes of recent dengue cases in five regencies of Central Java Province, Indonesia. Mosquito larvae and pupae were collected from the indoor and outdoor water containers from 253 houses within 50 m of houses occupied by a dengue patient. A considerable dengue vector population was found in all localities and altitudes based on the Aedes indices: an HI of 41.7% (15.0­70.6), CI of 33.6% (8.1­69.6) and BI of 57.1 (15.0­94.1). The highest indices were found in the highest altitude settlement; as the most common larval habitat in this village was a large-sized cement tank, larvivorous fish can act as effective predators in this case. This finding indicates an expansion of the dengue problem from low to high altitudes, causing a high potential for dengue transmission in all of the localities.

Distribution of Voltage-Gated Sodium Channel (Nav) Alleles among the Aedes aegypti Populations In Central Java Province and Its Association with Resistance to Pyrethroid Insecticides.

The emergence of insecticide resistant Aedes aegypti mosquitoes has hampered dengue control efforts. WHO susceptibility tests, using several pyrethroid compounds, were conducted on Ae. aegypti larvae that were collected and raised to adulthood from Semarang, Surakarta, Kudus and Jepara in Java. The AaNaV gene fragment encompassing kdr polymorphic sites from both susceptible and resistant mosquitoes was amplified, and polymorphisms were associated with the resistant phenotype. The insecticide susceptibility tests demonstrated Ae, aegypti resistance to the pyrethroids, with mortality rates ranging from 1.6%-15.2%. Three non-synonymous polymorphisms (S989P, V1016G and F1534C) and one synonymous polymorphism (codon 982) were detected in the AaNaV gene. Eight AaNaV alleles were observed in specimens from Central Java. Allele 3 (SGF) and allele 7 (PGF) represent the most common alleles found and demonstrated strong associations with resistance to pyrethroids (OR = 2.75, CI: 0.97-7.8 and OR = 7.37, CI: 2.4-22.5, respectively). This is the first report of 8 Ae. aegypti AaNaV alleles, and it indicates the development of resistance in Ae. aegypti in response to pyrethroid insecticide-based selective pressure. These findings strongly suggest the need for an appropriate integrated use of insecticides in the region. The 989P, 1016G and 1534C polymorphisms in the AaNaV gene are potentially valuable molecular markers for pyrethroid insecticide resistance monitoring.