INTRODUCTION

Effective mosquito control is pivotal in the epidemiology of vector-borne diseases, but no successful preventive measures have been recorded for dengue vector control. Hence, possible alternatives to chemical larvicides have been explored, including plant alcoholic extracts. This study determined the larvicidal efficacy of Annona squamosa ethanolic leaf extracts against third instar larvae of Aedes aegypti.

METHODS

Three replicates of varying concentrations of Annona squamosa ethanolic extract (i.e., 10%, 40%, and 70%) versus positive (Novaluron) and negative controls (tap water) were used to determine larval mortality.

RESULTS

Greatest larval mortality was noted using the 70% concentration (i.e., 24% versus the observed values of 20% and 8%, respectively for the 40% and 10% ethanolic concentrations). Relative to the controls, the mean differences in the mortality rates of the Aedes aegypti larvae across the leaf ethanolic concentrations were statistically significant (i.e., p-value < 0.05). There was increasing trend in larval mortality over time, but 50% lethal dose was not achieved. In conclusion, the different Annona squamosa ethanolic leaf extracts could be used as alternative botanical larvicides against Aedes species.

Plants ; Animals ; Epidemiology ; Mosquito Control

OBJECTIVE: To analyze the density, distribution and insecticide resistance of Aedes albopictus in Ningbo City in 2021, so as to provide insights into formulation of dengue fever control strategies. METHODS: Four administrative villages were randomly selected from each county (district) in Ningbo City from April to November, 2021, to investigate the indoor population density of Aedes larvae, and the Breteau index (BI) was calculated. The population density of adult mosquitoes was investigated in residential areas, parks/bamboo forests, waste tire stacking sites/waste stations/construction sites in each county (district). On June 2021, larvae of the natural strain A. albopictus were collected from epidemic sites of dengue fever in Ningbo City in 2018, and raised in laboratory. Then, larvae and female mosquitoes without blood feeding were selected for insecticide resistance bioassays, while insecticide-sensitive strains of A. albopictus served as controls. The resistance of A. albopictus larvae to deltamethrin, beta-cypermethrin, propoxur, temephos and dichlorvos using the impregnation method, and the medium lethal concentration (LC₅₀) and resistance ratio (RR) were calculated. The resistance of adult A. albopictus to beta-cypermethrin, permethrin, deltamethrin, propoxur and malathion was determined using the tube bioassay, and the mosquito mortality was calculated. RESULTS: A total of 10 072 small water containers from 9 935 households were investigated in Ningbo City in 2021, and there were 1 276 containers with Aedes larvae detected, with an average BI of 12.89. Totally 1 422 mosquito nets were allocated and 954 female A. albopictus were captured, with an average net trapping index of 1.34 mosquitoes/(net·hour). Both larval and adult A. albopictus mosquitoes were found from April to November, and the density of larval A. albopictus peaked in September (BI = 21.21), while the density of adult A. albopictus peaked in August, with a net trapping index of 2.38 mosquitoes/(net·hour). The LC₅₀ values of delta-methrin, beta-cypermethrin, propoxur, temephos and dichlorvos were 0.017 4, 0.000 9, 0.364 1, 0.038 1 mg/L and 0.001 6 mg/L against larvae of natural strains of A. albopicchus, with RRs of 49.66, 25.53, 9.65, 2.24 and 6.06, and the mortality rates of adult mosquitoes were 66.00% (66/100), 69.39% (68/98), 25.00% (25/100), 98.97% (96/97) and 100.00% (98/98) 24 hours post-treatment with 0.08% beta-cypermethrin, 0.03% deltamethrin, 0.4% permethrin, 0.05% propoxur, and 0.5% malathion for 24 h, respectively. CONCLUSIONS A. albopictus is widely distributed in Ningbo City, with a high population density and presents high-level resistance to common pyrethroid insecticides. The population density and insecticide resistance of A. albopictus requires to be reinforced.
Animals ; Female ; Malathion ; Temefos ; Aedes ; Propoxur ; Permethrin ; Dichlorvos ; Mosquito Vectors ; Larva ; Dengue/prevention & control*

OBJECTIVE: This study assessed the species composition of mosquitoes collected from ovitraps in selected public schools of Metro Manila, Philippines.

MATERIALS AND METHODS: Ovitraps were installed from November 2013 to February 2014, in purposively selected public elementary and high schools of Metro Manila. Ovitraps were installed inside classrooms and collected weekly and examined for mosquito eggs and larvae. Speciation was done once a month from November 2013 to February 2014. All positive paddles were immersed in water for larval emergence, reared to fourth instars and were identified using taxonomic keys.

RESULTS: A total of 1,482 ovitraps were installed in the selected public schools, and 18,325 larvae were collected from elementary schools, while 16,670 larvae were collected from high schools. The mean ovitrap index or infestation rate was 49.69% during the period of data collection. Mosquito larvae were identified as Aedes aegypti (88.94%) and Aedes albopictus (11.06%). Aedes aegypti and Aedes albopictus coexisted in some of the examined paddles. No significant differences were observed between the type of school and the presence of Aedes larvae. Significant differences were observed between total number of mosquito larvae and months of collection.

CONCLUSION: The presence of Aedes mosquitoes in schools evidently shows that continuous vector surveillance in schools is necessary as this information will help in the formulation of proactive vector control activities, thereby preventing the occurrence of mosquito-borne diseases.

Mosquito ; Aedes ; Vector ; School ; Surveillance

BACKGROUND: International Health Regulations controls international travel including human movement, disease vector, and imported items to prevent the spread of dengue, especially in seaports, airports, and border crossing posts. This study aimed to determine dengue Transovarial Transmission Index (TTI) and distribution of dengue virus in the areas around Adisucipto Airport of Yogyakarta, Indonesia. METHODS: The study was a descriptive analytic study with cross sectional design, conducted by mapping the spread of the dengue virus and identifying TTI in Adisucipto Airport. A total of 145 ovitraps were installed in both perimeter and buffer areas of the airport. Positive Ovitrap Index (OI), TTI, and serotype of dengue virus were examined. The TTI was identified using immunocytochemistry immunoperoxidase streptavidin biotin complex (IISBC) method in mosquito head squash preparations. RESULTS: OI in the buffer area was 32 (45.1%), whereas OI in the perimeter area was 24 (32.4%). The TTI in the buffer and perimeter areas were 21 (18.3%) and 11 (18.9%), respectively. The TTI was found greater in the Aedes aegypti population compared to the Aedes albopictus population, both in the perimeter area (20% versus 16.7%) and the buffer area (20.3% versus 16.1%). Dengue virus serotype-2 (DENV-2) and dengue virus serotype-3 (DENV-3) were predominantly found in Ae. aegypti and Ae. albopictus. CONCLUSIONS Buffer areas of Adisucipto Airport of Yogyakarta have higher risk as breeding sites for Aedes spp., predominantly DENV-2 and DENV-3 serotypes. High OI shows that the areas are likely to have higher risk of developing dengue outbreak.
Aedes ; virology ; Air Travel ; Airports ; Animals ; Cross-Sectional Studies ; Dengue ; transmission ; virology ; Dengue Virus ; classification ; isolation & purification ; Female ; Indonesia ; Mosquito Vectors ; virology ; Ovum ; virology ; Serotyping

Communicable Diseases, Emerging ; Communication ; Dengue ; prevention & control ; Dengue Vaccines ; therapeutic use ; HIV Infections ; prevention & control ; Health Education ; Health Policy ; Humans ; Mosquito Control ; Obesity ; prevention & control ; therapy ; Public Health ; Public Health Practice ; Risk ; Risk Reduction Behavior ; Sexually Transmitted Diseases ; prevention & control ; Singapore ; Tobacco Use ; prevention & control ; therapy

OBJECTIVETo investigate the toxicity of indigenous Bacillus thuringiensis (B. thuringiensis)isolates from Malang City for controlling Aedes aegypti (Ae. aegypti) larvae.

METHODSSoil samples were taken from Purwantoro and Sawojajar sub-districts. Bacterial isolation was performed using B. thuringiensis selective media. Phenotypic characteristics of the isolates were obtained with the simple matching method. The growth and prevalence of spores were determined by the Total Plate Count method, and toxicity tests were also performed on the third instar larval stage of Ae. aegypti. The percentage of larval mortality was analysed using probit regression. The LC50 was analysed by ANOVA, and the Tukey HSD interval was 95%.

RESULTSAmong the 33 selected bacterial isolates, six were obtained (PWR4-31, PWR4-32, SWJ4-2b, SWJ4-4b, SWJ-4k and SWJ5-1) that had a similar phenotype to reference B. thuringiensis. Based on the dendrogram, all of the bacterial isolates were 71% similar. Three isolates that had a higher prevalence of reference B. thuringiensis were PWR4-32, SWJ4-4b and SW5-1, of which the spore prevalence was 52.44%, 23.59%, 34.46%, respectively. These three indigenous isolates from Malang City successfully killed Ae. aegypti larvae. The PWR4-32 isolates were the most effective at killing the larvae.

CONCLUSIONSSix indigenous B. thuringiensis isolates among the 33 bacterial isolates found in the Sawojajar and Purwantoro sub-districts were toxic to the third instar larvae of Ae. aegypti. The PWR4-32 isolates were identical to the reference B. thuringiensis and had 88% phenotype similarity. The PWR4-32 isolates had the highest spore prevalence (52.44%), and the early stationary phase occurred at 36 h. The PWR4-32 isolates were the most effective at killing Ae. aegypti larvae (LC50-72 h=2.3×10(8) cells/mL).

Aedes ; microbiology ; Animals ; Bacillus thuringiensis ; isolation & purification ; physiology ; Biological Control Agents ; Indonesia ; Insecticides ; Larva ; microbiology ; Lethal Dose 50 ; Mosquito Control

OBJECTIVE: Dengue fever remains a public health problem in the Philippines. Eliminating key container artificial breeding sites of mosquito vectors is a vital part of dengue control. The objective of this descriptive cross-sectional study was to conduct an entomological survey of artificial container breeding sites of Aedes mosquitoes in households of two puroks in Batasan Hills, Quezon City.

METHODS: All potential artificial container breeding sites of dengue in each household were inspected for mosquito larvae. Water was sampled from all containers that had mosquito larvae. Water was sampled from all containers that had mosquito larvae and the larval species determined through microscopic examination. Using the World Health Organization list of recognized containers, each container was classified as recognized or an unrecognized container.

RESULTS: The larval indices computed were: container index = 6.4%, household index = 23.9% and Breteau index = 29%. The proportion of containers positive for A. aegypti larvae was significantly higher for the unrecognized containers (9.9%) than that of the recognized containers (3.9%) (p=0.002).

CONCLUSION: The high household index and Breteau index indicate that the potential for dengue transmission is high in the study area. Unrecognized artificial containers contributed significantly to the number of Aedes breeding sites. "Search-and-destroy" campaigns in the community should be expanded to include these containers. Crafting specific vector control messages that address the problem of particular unrecognized containers as well as those of recognized containers with the highest proportion positive for Aedes larvae will also aid dengue control and prevention. Repeat surveys to monitor larval indices may be used to help ascertain the effectiveness of these messages in decreasing mosquito breeding sites.

Animal ; Aedes ; Larva ; Water ; Public Health ; Mosquito Vectors ; Dengue ; Cities ; Breeding

OBJECTIVETo assess the larvicidal and irritant activities of the hexane extracts of leaves of Citrus sinensis (C. sinensis) against the early fourth instars and female adults of Aedes aegypti (Ae. aegypti).

METHODSThe larvicidal potential of the prepared leaf extract was evaluated against early fourth instar larvae of Ae. aegypti using WHO protocol. The mortality counts were made after 24 h and LC50 and LC90 values were calculated. The efficacy of extract as mosquito irritant was assessed by contact irritancy assays. Extract-impregnated paper was placed on a glass plate over which a perspex funnel with a hole on the top was kept inverted. Single female adult, 3-day old unfed/blood-fed, was released inside the funnel. After 3 min of acclimatization time, the time taken for the first take-off and total number of flights undertaken during 15 min were scored.

RESULTSThe citrus leaf extracts from hexane possessed moderate larvicidal efficiency against dengue vector. The bioassays resulted in an LC50 and LC90 value of 446.84 and 1 370.96 ppm, respectively after 24 h of exposure. However, the extracts were proved to be remarkable irritant against adults Ae. aegypti, more pronounced effects being observed on blood-fed females than unfed females. The extract-impregnated paper was thus proved to be 7-11 times more irritable as compared with the control paper.

CONCLUSIONSThe hexane extracts from C. sinensis leaves are proved to be reasonably larvicidal but remarkably irritant against dengue vector. Further studies are needed to identify the possible role of extract as adulticide, oviposition deterrent and ovicidal agent. The isolation of active ingredient from the extract could help in formulating strategies for mosquito control.

Aedes ; drug effects ; Animals ; Citrus sinensis ; metabolism ; Dengue ; transmission ; Disease Vectors ; Female ; Insecticides ; pharmacology ; Larva ; drug effects ; Mosquito Control ; methods ; Plant Extracts ; pharmacology ; Plant Leaves ; metabolism

OBJECTIVETo assess the larvicidal and repellent potential of the essential oil extracted from the leaves of peppermint plant, Mentha piperita (M. piperita) against the larval and adult stages of Aedes aegypti (Ae. Aegypti).

METHODSThe larvicidal potential of peppermint oil was evaluated against early fourth instar larvae of Ae. aegypti using WHO protocol. The mortality counts were made after 24 and 48 h, and LC50 and LC90 values were calculated. The efficacy of peppermint oil as mosquito repellent was assessed using the human-bait technique. The measured area of one arm of a human volunteer was applied with the oil and the other arm was applied with ethanol. The mosquito bites on both the arms were recorded for 3 min after every 15 min. The experiment continued for 3 h and the percent protection was calculated.

RESULTSThe essential oil extracted from M. piperita possessed excellent larvicidal efficiency against dengue vector. The bioassays showed an LC50 and LC90 value of 111.9 and 295.18 ppm, respectively after 24 h of exposure. The toxicity of the oil increased 11.8% when the larvae were exposed to the oil for 48 h. The remarkable repellent properties of M. piperita essential oil were established against adults Ae. aegypti. The application of oil resulted in 100% protection till 150 min. After next 30 min, only 1-2 bites were recorded as compared with 8-9 bites on the control arm.

CONCLUSIONSThe peppermint essential oil is proved to be efficient larvicide and repellent against dengue vector. Further studies are needed to identify the possible role of oil as adulticide, oviposition deterrent and ovicidal agent. The isolation of active ingredient from the oil could help in formulating strategies for mosquito control.

Aedes ; drug effects ; growth & development ; Animals ; Insect Repellents ; pharmacology ; Insecticides ; pharmacology ; Larva ; drug effects ; growth & development ; Mentha piperita ; chemistry ; Mosquito Control ; methods ; Oils, Volatile ; pharmacology ; Plant Leaves ; chemistry ; Plant Oils ; pharmacology

In Nigeria, malaria causes up to 11% of maternal mortality. Our main aim was to find out the most common mosquito control measures employed by the pregnant women in Lagos and their effects on malaria infection. The study was carried out over a period of 6 months during which trained interviewers administered questionnaires to 400 pregnant women. The prevalence of malaria was 8.4%. There was no significant association between the prevalence of malaria and age, level of education, or occupation of the participants. Pregnant women in the age range 26-30 had the mean parasite density (409.9+/-196.80). Insecticide spray (32.8%), mosquito coil (27.5%), and insecticide-treated nets (ITN) (15.5%) were the major mosquito control measures employed by the participants while the prevalence of infection among them were 2.3%, 6.2%, and 3.2%, respectively (P<0.05). Only 18.3% of the women had taken more than one dose of intermittent preventive treatment (IPT), while another 11.8% had taken a single dose. The infection rate among them was 4.1% and 6.4%, respectively. Malaria prevalence was highest among those who had not received any dose of IPT (10%). This study showed that the use of ITN and IPT among the pregnant women were still unacceptably low. It also showed that the use of insecticide spray which was the most common malaria control measure adopted by the participants was effective despite the fact that it is not a National Malaria Control Policy. We recommend that a sustained integrated mosquito management and public education should be strengthened in Nigeria.
Adolescent ; Adult ; Animals ; *Culicidae/parasitology ; Female ; Health Knowledge, Attitudes, Practice ; Humans ; *Insect Vectors/parasitology ; Insecticides ; Malaria/epidemiology/*prevention & control ; Mosquito Control/*methods ; Nigeria/epidemiology ; Plasmodium/*physiology ; Pregnancy ; Pregnancy Complications, Parasitic/epidemiology/*prevention & control ; Prenatal Care ; Prevalence ; Public Health ; Questionnaires ; Young Adult