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Objective: To monitor the current duration of the application rates in vector programme and the level of Aedes albopictus larvae susceptibility from three selected areas in northeast district of Penang on two selected larvicides, temephos and Bacillus thuringiensis subsp. israelensis (Bti) which are commonly used by Penang Health Department for vector control. Methods: The mosquito larvae were tested against two types of larvicides: (1) temephos (Abate
ABSTRACT
Objective: To explore the larvicidal activities of different plant parts of Melanochyla fasciculiflora (. M. fasciculiflora), Gluta renghas (. G. renghas), Anacardium occidentale and Mangifera indica from family Anacardiaceae against the laboratory and field strains of dengue vectors Aedes aegypti and Aedes albopictus (. Ae. albopictus). Methods: Leaves and bark parts of study plants were collected from Taman Nageri, Bukit Pancor and Teluk Bahang National Park, Penang, Malaysia. Leaves and stem barks were separated, air dried, ground and extracted with methanol by Soxhlet apparatus. Crude extract was obtained by evaporating the extra solvent in rotary evaporator. The 4th instar larvae from laboratory and field strains were exposed to 50-1. 300 mg/L concentrations according to World Health Organization standard larval bioassay. Larval mortality was recorded after 24 h of exposure. Results: Highest larvicidal activity was exhibited by G. renghas bark extract against Ae. albopictus laboratory strain at 600 mg/L. G. renghas also showed the highest larvicidal activities for other strains as compared to other plant extracts, followed by Mangifera indica and M. fasciculiflora and Anacardium occidentale. Conclusions: Ae. albopictus has been found to be more susceptible as compare to Aedes aegypti in both laboratory and field strains in this study. G. renghas and M. fasciculiflora were tested for the first time and exhibited prompting larvicidal activities against dengue vectors. These results revealed that all the plants especially G. renghas and M. fasciculiflora have the higher larvicidal activities and can be used for the control of dengue vector as a new environment friendly, target specific and low cost phytochemical.
ABSTRACT
Objective: To evaluate the lethal concentration, oviposition deterrence and ovicidal activity of acetone extracts of Melanochyla fasciculiflora (M. fasciculiflora) leaf and Gluta renghas (G. renghas) leaf against Aedes albopictus (Ae. albopictus). Methods: To determine the lethal concentration of Anacardiaceae, ten test concentrations of the extracts ranging from 200 to 650 mg/L were selected for larvicidal bioassays and 25 early fourth instar larvae were exposed to the extracts for 24 h. The sub-lethal concentrations used for oviposition deterrence was the value of LC25, LC50 and LC75 from above study which is 235 mg/L, 470 mg/L and 705 mg/L for M. fasciculiflora extract and 187.5 mg/L, 375 mg/L and 562.5 mg/L for G. renghas extract, respectively. Twenty gravid Ae. albopictus were allowed to oviposit in different treated concentrations. For oviciding procedure, a total of 300 eggs of Ae. albopictus were soaked in solution with each treated concentration as mentioned above for 24 h. After 24 h, eggs were sieved and soaked in seasoned water, and hatching rates were calculated. For comparison, only seasoned water was used in control experiment. Results: G. renghas demonstrated lower LC50 value of 372.80 mg/L compared to M. fasciculiflora (467.90 mg/L). The activity index of negative oviposition revealed the deterrent effect and thus, caused a remarkable negative response resulting in oviposition of fewer eggs compared with control (without plant extract). The acetone extract of M. fasciculiflora was more effective than G. renghas extract in displaying oviposition deterrence potential since the latter did not possess the deterring effect within the concentration range tested. However, both plant extracts exhibited excellent oviciding effect as 92.33% of eggs failed to be hatched when treated with 705.0 mg/L of M. fasciculiflora and 86.67% with 562.5 mg/L of G. renghas. The oviposition deterrence and percentage of egg mortality were directly proportional to the concentrations of extracts in both plants tested. Conclusions: These results clearly indicate that the acetone extract of G. renghas could be served as potential larvicide, whereas M. fasciculiflora has better sub-lethal effect for oviposition deterrence and against Ae. albopictus as an oviciding agent.
ABSTRACT
<p><b>OBJECTIVE</b>To investigate the prevalence of container breeding mosquitoes with emphasis on the seasonality and larval habitats of Aedes aegypti (Ae. aegypti) in Makkah City, adjoining an environmental monitoring and dengue incidence.</p><p><b>METHODS</b>Monthly visits were performed between April 2008 and March 2009 to randomly selected houses. During each visit, mosquito larvae were collected from indoors and outdoors containers by either dipping or pipetting. Mosquitoes were morphologically identified. Data on temperature, relative humidity, rain/precipitations during the survey period was retrieved from governmental sources and analyzed.</p><p><b>RESULTS</b>The city was warmer in dry season (DS) than wet season (WS). No rain occurred at all during DS and even precipitations did fall, wetting events were much greater during WS. Larval survey revealed the co-breeding of Aedes, Culex and Anopheles in a variety of artificial containers in and around homes. 32 109 larvae representing 1st , 2nd, 3rd, and 4th stages were collected from 22 618 container habitats. Culicines was far the commonest and Aedes genus was as numerous as the Culex population. Ae. aegypti larval abundance exhibited marked temporal variations, overall, being usually more abundant during WS. Ten types of artificial containers were found with developing larvae. 70% of these habitats were located indoors. 71.42% of indoor containers were permanent and 28.58% was semi-permanent during WS. Cement tanks was the only container type permanent during DS. Ae. aegypti larval indices (CI, HI, BI) recorded were greater during WS.</p><p><b>CONCLUSIONS</b>Taken together, these results indicate a high risk of dengue transmission in the holy city.</p>