Effect of Eosin Solution Exposed to Sunlight against Anopheles Mosquito Larvae

Mosquitoes are a menace for millions of people around the world, they are vectors for destructive microorganisms which cause diseases like Malaria, Dengue fever and Lymphatic filariasis, affecting people in developing countries and areas with tropical climates. Anopheles, a predominant genus transmits malaria, and the World Health Organization have shown that 350,000 lives especially children and pregnant women are lost annually by it. The aim of this study is to determine the effect of eosin solution exposed to sunlight on larvae of Anopheles mosquito. The use of control method was aid at eliminating the larva stages of the mosquito life cycle. A total of one hundred and twenty (120) Anopheles mosquito larvae were harvested using dipper with handle and net from drainages at Eagle Island and Rivers State University both in Port Harcourt. Five different concentrations of Eosin solutions were prepared in volumes of 1000 microlitre (µl), 800µl, 600µl, 400µl, 200µl after a stock solution of 1gram(g) in 100ml and a control, the physicochemical parameters of the solutions were determined using Extech model DO700 measuring instrument. Twenty (20) mosquito larvae, were carefully introduced into each of the concentrations, exposed to sunlight and observed for 24 hours (hrs) for a period of six (6) days for susceptibility. A hundred percent (100%) mortality was recorded in eosin volume of 1000µl and 800µl. The separate solutions of eosin showed significant effects of their concentrations on the Anopheles mosquito larvae of P-value 0.017 at P<0.05. The result obtained for the physicochemical parameters were; pH 5.24, temperature 30.4oC, conductivity 168µS/cm, salinity 0.08%, total dissolved solids 118 milligram per litre(mg/L) and dissolved oxygen was 6.5mg/L for the control. Changes occurred in the values of the dissolved oxygen before and after exposure to sunlight in all the dilutions. The results obtained showed that after 24 hrs, the mortality rate of the larvae increased, indicating that Anopheles mosquito larvae expose to concentrations of eosin solutions results in their mortality within 48 hrs. It may be concluded that this study has provided some evidence of larvicidal effect of eosin solution exposed to sunlight on larvae of Anopheles mosquito.

Mosquito larva distribution and natural Wolbachia infection in campus areas of Nakhon Ratchasima, Thailand

Objective: To determine the prevalence of mosquito larvae in campus areas and the infection rate of endosymbiotic bacteria, Wolbachia in mosquito larvae. Method: The mosquito larvae samples were collected in residential areas and academic buildings of Suranaree University of Technology located in Northeastern Thailand during 2017-2018. Mosquito species identification was performed using GLOBE mosquito protocols and Rattanarithikul & Panthusiri's keys. The gene encoding for the surface protein of Wolbachia was amplified by PCR and confirmed by DNA sequencing. Results: Armigeres sp. is the highest proportion of mosquito larvae followed by Culex spp., Aedes albopictus, Aedes aegypti, and Toxorynchites spp., respectively. Aedes aegypti have breeding sites mostly in the containers found indoors, whereas the main breeding sites of Aedes albopictus were found in both outdoors and indoors. The House Index and Breteau Index for Aedes spp. was more than 5% and 20%, respectively, in both areas, indicating that these areas are dengue sensitive. The highest proportion of Wolbachia infection was found in the larvae of Culex spp. (86.21%), followed by Aedes albopictus (69.23%) and rarely detected in Aedes aegypti (9.09%). Conclusion: The present study reported the first natural infection of Wolbachia in mosquito larvae in Thailand. Our result suggested that the mosquito species containing higher proportion of Wolbachia are less likely to be vectors for dengue. Therefore, Wolbachia transfection in mosquito larvae could be applied as a biocontrol for dengue and other mosquito-borne disease prevention.

Studies on Malaria Vector Population Density in Three Selected Areas in Sokoto Metropolitan, Sokoto State - Nigeria

This study is conducted to determine the population density of mosquitoes in three selected area (Kofar Taramniya, Mabera and Bello Way) in Sokoto metropolis. To identified and count the population of mosquito, different breeding sites were investigated for the preferences of mosquitoes. Mosquito larvae were collected using dipper, ladle spoon from drainages, stagnant water, gutters, open wells, local pots, water tanks and cattle sheds. A total population of 4,764 mosquito larvae were collected and identified From the three (3) selected areas larvae and pupae were encounters in abundance. In Mabera area, a total of 1799 (37.7%) larvae are collected in which 1199 (45.8%) belonging to Anophelesgenera and 600 (27.9%) belong to culexgenera. In kofar Taramniya a total of 1649 (34.6%) larvae are collected in which 1000 (38.2%) belong to Anopheles genera and 649 (30.2%) belong to culexgenera, in Bello Way, A total of 1317 (27.5%) larvae were collected,417 (15.9%) belong to Anophelesgenera and 900 (41.9%)belongto culexgenera. Statistical analysis conducted indicated a significant difference (p<0.05) between the three collections. Mosquitoes encountered belong to two genera of Anophelesand Culex. The predominant genus was Anopheleswith a total of 2,615 larvaewhile Culexhas a total of 2149 larvae in all the three study areas. Considering the medical importance of mosquitoes, the information provided from this study will serve as a basis for understanding the implication of mosquitoes nuisance and provide effective control strategies against the vector and to reduce mosquitoes born disease

Spatial and temporal country-wide survey of temephos resistance in Brazilian populations of Aedes aegypti

The organophosphate temephos has been the main insecticide used against larvae of the dengue and yellow fever mosquito (Aedes aegypti) in Brazil since the mid-1980s. Reports of resistance date back to 1995; however, no systematic reports of widespread temephos resistance have occurred to date. As resistance investigation is paramount for strategic decision-making by health officials, our objective here was to investigate the spatial and temporal spread of temephos resistance in Ae. aegypti in Brazil for the last 12 years using discriminating temephos concentrations and the bioassay protocols of the World Health Organization. The mortality results obtained were subjected to spatial analysis for distance interpolation using semi-variance models to generate maps that depict the spread of temephos resistance in Brazil since 1999. The problem has been expanding. Since 2002-2003, approximately half the country has exhibited mosquito populations resistant to temephos. The frequency of temephos resistance and, likely, control failures, which start when the insecticide mortality level drops below 80%, has increased even further since 2004. Few parts of Brazil are able to achieve the target 80% efficacy threshold by 2010/2011, resulting in a significant risk of control failure by temephos in most of the country. The widespread resistance to temephos in Brazilian Ae. aegypti populations greatly compromise effective mosquito control efforts using this insecticide and indicates the urgent need to identify alternative insecticides aided by the preventive elimination of potential mosquito breeding sites.

Evaluation of entomopathogenic Bacillus sphaericus isolated from Lombok beach area against mosquito larvae

Objective: To isolate, characterize and evaluate toxicity of Bacillus sphaericus (B. sphaericus) from beach area of Lombok Island. Methods: Soil was collected from determined locations and suspended in sterile physiological saline water. After heat shock was applied, suspension was spread on NYSM agar medium. Colonies grown were then observed and isolated. Colony, cell morphology, and biochemical/physiological characteristics were tested and compared to B. sphaericus 2362 as standard. Initial toxicity testing was done against three species of mosquito larvae (Culex quinquefasciatus, Anopheles aconitus and Aedes aegypti) and isolates that showed more than 50% larvae killing will be assayed to obtain LC

The effects of a behavioral change program in reducing the house index of mosquito larvae in households in Phetcabun province, Thailand.

Introduction: The purpose of this quasi-experimental research was to study the effectiveness of a behavioral change program in reducing house index of mosquito in Village Baan-Wangpong, Lomsak district in Phetcabun province, Thailand. Methods: The sample size of experimental and control group was 42 representatives of household in each group. Representatives of each sampled household were tested for knowledge, perception and behavioral practice in prevention of dengue fever before and after the program intervention. The program included training on dengue fever prevention by health personnel, demonstration of making mosquito repellents from local product, organising an awareness contest, broadcasting health messages through media and surveying households for mosquitoes’ larvae. Results: The study found that most households in village Baan-Wangpong had low knowledge (60.4%), perceived risk (60.4%), perceived severity (64.6%) and behavioral practice (77.1%) in the prevention of dengue fever prior to the program, with comparability in intervention versus control. The results showed that after the program intervention, the experimental group had a significantly higher level of knowledge (p=0.001), perceived risk (p=0.042), perceived severity (p=0.002) and behavior (p=0.028) in preventing dengue fever than before the program intervention and higher than the control group post-intervention. The experimental group’s house index was also significantly (p=0.001) lower than before the program and lower than the control group post-intervention. Conclusions: This study suggests that a proactive program about knowledge, perceptions and behaviors on prevention of dengue fever with support from public health personnel and community participation, can positively change health behavior, resulting in reducing the house index of mosquito larva.

Application of Remotely-sensed Data for Modeling Malaria Infection in Lokoja, Nigeria.

Aims: To estimate incidences of malaria infection in an urban setting using Remotely sensed data and matching same with hospital records to validate the use of Remote sensing data as a methodology for studying the prevalence of malaria. Study Design: Analyses of 2006 Nigeriasat-1 and Land sat ETM+satellite data for modeling malaria infection. Place and Duration of Study: Lokoja, Capital city of Kogi State in Central Nigeria, between March 2012 and January 2013. Methodology: Extraction of land use types, NDVI and LST maps using ILWIS 3.3 and Idrisi software. Cross tabulation of extracted maps to carry out correlational analyses while buffer analysis was conducted to ascertain risk zones of malaria infection in the town. The clinical data was used in determining the recorded incidence of malaria in the study area. Results: Built-up area, sand bars and vacant land occupy least land cover (i.e. 28.31%) while urban agricultural land, vegetation and water bodies covered 344.33km2 (59.72%), 41.98km2 (7.28%) and 18.51km2 (3.21%), respectively. The LSE value ranges from 0.92 to 0.989 with an average of 0.955 whereas the highest emissivity is recorded where vegetation is very dense and the lowest recorded for Sand bars. The LST for sand bars, vacant land and built-up area recorded the highest average temperatures of 41.13°C, 35.66°C and 34.56°C, respectively. The highest negative correlation was found in vegetation (-0.96) with other negative values recorded for urban agricultural land and water bodies. The lowest correlation (0.65) was recorded from areas covered with sand bars. The UHI map shows that temperatures at the periphery are lower (about 18°C) but higher at the core (from 26°C to 40°C). Conclusion: The interplay of NDVI, LST and land use/cover types of Lokoja provides the impetus for the rising incidence of malaria in Lokoja town. Proper urban planning which will support sufficient drainages, effective waste removal, sanitary landfill sites, vegetation control, fumigation, etc. can boost sanitary conditions whilst minimizing the availability of breeding sites for mosquito larvae. At the household levels, extensive use of bed nets and periodic fumigation appear to be the most appropriate short-term measures for curtailing the incidences of malaria at the study area.

Experimental observation of toxic effect of Bacillus thuringiensis var. israelen-sis against Aedes,Culex and Anopheles larvae / 中国血吸虫病防治杂志

Objective To evaluate the toxic effect of Bacillus thuringiensis var. israelensis(Bti)wettable powder against Ae-des,Culex and Anopheles larvae. Methods The biological assay was applied to test the lethal concentration of 50%(LC50)of Bti wettable powder against Aedes,Culex and Anopheles larvae. Results The LC50(s) of Bti wettable powder against Aedes albopictus, Culex pipiens pallens and Anopheles sinensis larvae were 0.104,0.160μg/ml and 0.324μg/ml,respectively;its biological poten-cies against them were 0.125,0.192 IU/ml and 0.389 IU/ml,respectively. The LC50(s) of continuous contact of Bti wettable powder with An. sinensis stageⅢlarvae for 1,2 d and 3 d were 0.324,0.092μg/ml and 0.032μg/ml,respectively,and its biological po-tencies were 0.389,0.110 IU/ml and 0.038 IU/ml,respectively. The LC50(s) of the bacteria against An. sinensis stageⅠ,Ⅱ,Ⅲ,Ⅳwere 0.024,0.137,0.324 μg/ml and 0.450 μg/ml,respectively,and the biological potencies were 0.029,0.164,0.389 IU/ml and 0.540 IU/ml,respectively. Conclusion Bti wettable powder has a good toxicity to Aedes,Culex and Anopheles larvae,espe-cially for the latter two. It is better to apply the bacteria at the early stage of mosquito larvae.

Efficacy of indigenous larvivorous fishes against Culex quinquefasciatus in the presence of alternative prey: Implications for biological control.

Background & objectives: Indigenous larvivorous fishes bear potential for regulating vector mosquitoes through trophic interactions. The mosquito prey preference of five indigenous larvivorous fishes in the presence of alternative food items was assessed to highlight their use in mosquito vector management. Methods: Laboratory experiments were carried out using the larvivorous fishes Ambassis (=Chanda) nama, Parambassis (=Chanda) ranga, Colisa fasciatus, Esomus danricus and Aplocheilus panchax, as predators and IV instar Culex quinquefasciatus larvae as target prey. Mosquito prey preference of these fishes in the presence of chironomid larvae, tubificid worms and artificial fish foods, in varied proportions, were assessed using preference index. Results: The fishes consumed considerable amount of mosquito larvae both in absence and presence of alternative food items. However, the positive selectivity for mosquito larvae at all densities were significantly (p <0.05) affected by the alternative foods. The chironomid larvae and tubificid worms were consumed proportionately higher than expected (p <0.05), while the artificial fish food was consumed at lower than expected proportions (p <0.05). The niche overlap was significantly similar among the fish species suggesting likeliness in predation pattern and prey preference. Interpretation & conclusion: The results reflect that the alternative food items influence the mosquito prey selectivity and thus the efficacy of indigenous larvivorous fishes. While use of these fishes in the wetlands and allied mosquito larval habitats in different parts of the country is suggested, impact of the alternative prey may affect the successful regulation of mosquitoes. Assessment of appropriate predator-prey ratio under natural habitat conditions is recommended to enhance successful mosquito control by these fishes.

Potential Larvicidal Properties of Blighia sapida Leaf Extracts against Larvae of An. gambiae Cu. quinquefasciatus and Ae. aegypti.

Blighia sapida is a medicinal plant used in Southern Nigeria for the treatment of some eye ailments and headache. The Centre for Scientific Research into Plant Medicine (CSRPM), Ghana, has used this plant for the treatment of diarrhea for over 20 years. Objective: This study was designed to investigate the lethal effect of aqueous, ethanol, and ethyl acetate extracts of the leaf of B. sapida on fourth instar larvae of An. gambiae, Cu. quinquefasciatus and Ae. aegypti. Methods: The lethal effect of aqueous, ethanol and ethyl acetate extracts of the leaves of B. sapida at concentrations of 0.15, 0.30, 0.45, 0.60 and 0.75% w/v each were investigated in static bioassays on 4th 15 instar larvae of An. gambiae, Cu. quinquefasciatus and Ae. aegypti. Results: The 72hLC50 values of the aqueous extract were 0.393, 0.488 and 0.423%w/v for larvae of An. gambiae, Cu. quinquefasciatus and Ae. aegypti respectively, while the values for the ethanol extract were 0.319, 0.407 and 0.384%w/v for An. gambiae, Cu. quinefasciatus and Ae. aegypti larvae respectively. For the ethyl acetate extract tested against larvae of An. gambiae, Cu. quinquefasciatus and Ae. agypti, the 72hLC50 values were 0.135, 0.177 and 0.133% w/v respectively. As judged by the 72hLC50 values ethyl acetate extract was the most potent of the three extracts. Conclusions: Results obtained demonstrate that the leaves of B. sapida have marked larvicidal potential against mosquito larvae used in this study.

Optimization of medium composition for the production of mosquitocidal toxins from Bacillus thuringiensis subsp. israelensis.

Optimization of chicken feather (CF) based culture medium for the production of Bacillus thuringiensis subsp. israelensis (Bti) biomass in combination with the agro industrial by-product (coconut cake, CC) and manganese chloride (MnCl2) has been evaluated. The biomass yield of Bti spore/crystal toxin was highest (12.06 g/L) from the test medium (CF+CC+MnCl2) compared to the reference medium (Luria Bertani, LB). Toxicity assay with Bti produced from the test medium against mosquito vectors (Culex quinquefasciatus, Anopheles stephensi and Aedes aegypti) was also satisfactory and results were comparable with bacteria produced from LB. The results suggest that Bti can be produced to the maximum extent possible as a potential mosquitocidal activity as suggested by the test medium (CF+CC+MnCl2).

Comparative studies of the feeding capacity and preference of Aphyosemion gularis (Boulenger 1901) on some aquatic macroinvertebrates.

Background & objectives: An efficient larvivorous fish must show a predilection for mosquito larvae in the presence of alternative preys. This study compares the feeding capacity and preference of Aphyosemion gularis exposed to different kinds of aquatic macroinvertebrates. Methods: Various prey organisms such as Anopheles larvae and pupae, Culex larvae, chironomid larvae and ostracods were either singly and/or jointly presented at different densities to the fish and the number of prey consumed in 12 h light and dark periods were recorded. Results: The result showed that in terms of capacity and preference, the fish significantly consumed (p <0.05) more Anopheles larvae than pupae and more Anopheles larvae compared to Culex and chironomid larvae. It was also found that the fish preferred Culex larvae to chironomids larvae while significantly (p <0.05) more Anopheles larvae were consumed compared to the more abundant ostracods. Conclusion: The results indicate that A. gularis is adapted to feed more on Anopheles than Culex larvae on one hand and generally preferred mosquito larvae to non-mosquito macroinvertebrates. The implication of this observation is that the presence of other non-mosquito organisms considered in this study is unlikely to divert the attention of the fish from mosquito larvae, especially Anopheles larvae. The fact that the fish are able to feed on some of the non-mosquito organisms such as chironomids and ostracods, means that they can subsist on these organisms in the absence of mosquito larvae.

Habitat heterogeneity and prey selection of Aplocheilus panchax: an indigenous larvivorous fish.

Objective: The ability of the native larvivorous fish Aplocheilus panchax (Hamilton, 1822) (Cyprinodontiformes: Aplocheilidae) as predator of mosquito larvae was assessed under laboratory conditions using multiple prey and habitat conditions. Methods: The consumption of larvae of the mosquito Culex quinquefasciatus Say 1823 (Diptera: Culicidae) by A. panchax was evaluated in the presence of tubificid worms and chironomid larvae under complex and simple habitat conditions. The number of mosquito larvae consumed in comparison to other prey types was noted and an index of prey selectivity was used to evaluate the preference for mosquito larvae. Results: Aphlocheilus panchax consumed 53 to 65 mosquito larvae in a three hour feeding bout contrast to 29– 38 tubificid worms and 43–62 chironomid larvae depending on the habitat conditions. The prey consumption differed significantly between the habitats and the prey type. The index of prey selectivity was positive for Cx. quinquefasciatus larvae over other alternative prey in all the habitat conditions. Conclusion: It is apparent from the study that the larvivorous fish A. panchax can be employed for biological regulation of mosquitoes in rice-fields and similar wetlands where the multiple prey choices are available under complex habitat conditions. However, field studies including other prey species will be required to substantiate this finding.

Infestación de Smittium culisetae (trichomycetes) en larvas de mosquitos (diptera: culicidae) en el Valle Central de Costa Rica / Infestacion of Smittium culisetae (trichomycetes) in larvae of mosquitos (diptera: culicidae) in the Central Valley of Costa Rica

Los trichomycetes incluyen un interesante grupo de hongos filamentosos de distribución cosmopólita que se han adaptado a vivir como comensales obligados en el intestino de diversos grupos de artrópodos. Al menos una especie de Smittium es patogénica para los mosquitos que infecta. Esta investigación se realizó con el propósito de establecer que tan amplia es la infestación de Smittium culisetae en larvas de mosquito colectados en el Valle Central de costa Rica entre 1998 y el 2001. Se empleó técnicas entomológicas usuales para la colecta de los insectos, su cría con fines de identificación taxonómica y larvas de 3er. y 4o estadío se disecaron para exponer y estudiar el contenido del tracto digestivo. Se encontró un porcentaje de infestación de 25.8 por ciento, un valor semejante a lo informado por otros autores en otras regiones. No se encontró parásitos de otro tipo en los especímenes colectados.

Trichomycetes constitute a cosmopolitan group of filamentous fungi which are obligate symbionts in the digestive tracts of arthropods. Although this relationship in most species is apparently of a commensalistic nature, at least one species of Smittium has been reported as pathogenic. This study was conducted to determine the level of infestation of S. culisetae in mosquito larvae in the central region of Costa Rica, and to detect other parasites of this medically important group of insects during 1998-2001. Larvae were reared using standard entomological techniques to obtain adults for taxonomic identification; third and fourth stage larvae were dissected to reveal gut contents. A total of 27 mosquito species were collected. The infestation rate in 670 larvae examined was 25.8% which is similar to findings in other areas. Infested larvae did not show any pathological symptoms nor were other parasites of mosquitoes found.

Efficacy of Five Mosquito Larvicides Against Mosquito Larvae in Field / 环境与健康杂志

malathion.68 days after chlopyrifos was sprayed,the decrease rate of larvae density was still 95.34%.Conclusion The efficacy and persistent activity of chlopyrifos and the mixture of Bti and Bs-10 against mosquito larvae was better than the others.To control mosquito larvae in field,the suitable larvicides and application dosages should be applied according to the environment,characteristics,the pollute condition of water body etc.