Behavioral Response of Aedes aegypti Mosquito towards Essential Oils Using Olfactometer

Background: Aedes aegypti mosquito is responsible for transmitting human diseases like dengue and chikungunya. Personal or space protection with insect repellents is a practical approach to reducing human mosquito contact, thereby minimizing disease transmission. Essential oils are natural volatile substances from plants used as protective measure against blood-sucking mosquitoes. Methods: Twenty-three essential oils were evaluated for their repellent effect against Ae. aegypti female mosquito in laboratory conditions using Y-tube olfactometer.  Results: The essential oils exhibited varying degree of repellency. Litsea oil showed 50.31%, 60.2 %, and 77.26% effective mean repellency at 1 ppm, 10 ppm and 100 ppm respectively, while DEET exhibited 59.63%, 68.63%, 85.48% and DEPA showed 57.97%, 65.43%, and 80.62% repellency at respective above concentrations. Statistical analysis revealed that among the tested essential oils, litsea oil had effective repellency in comparison with DEET and DEPA against Ae. aegypti mosquito at all concentration. Essential oils, DEET and DEPA showed significant repellence against Ae. aegypti (P< 0.05) at all 3 concentration tested. Conclusion: Litsea oil exhibited effective percentage repellency similar to DEET and DEPA. The essential oils are natural plant products that may be useful for developing safer and newer herbal based effective mosquito repellents

Differential Larval Toxicity and Oviposition Altering Activity of Some Indigenous Plant Extracts against Dengue and Chikungunya Vector Aedes albopictus.

Background: Mosquitoes are well known as vectors of several disease causing pathogens. The extensive use of synthetic insecticides in the mosquito control strategies resulted to the development of pesticide resistance and fos- tered environmental deterioration. Hence in recent years plants become alternative source of mosquito control agents. The present study assessed the larvicidal and oviposition altering activity of six different plants species- Alstonia scholaris, Callistemon viminalis, Hyptis suaveolens, Malvastrum coromandelianum, Prosopis juliflora, Vernonia cinerea against Aedes albopictus mosquito in laboratory. Methods: Leaf extracts of all the six plants species in five different solvents of various polarities were used in the range of 20–400ppm for larval bioassay and 50,100 and 200ppm for cage bioassay (for the study of oviposition be- havior) against Ae. albopictus. The larval mortality data were recorded after 24 h and subjected to Probit analysis to determine the lethal concentrations (LC50), while OAI (Oviposition activity index) was calculated for oviposition altering activity of the plant extracts. Results: Vernonia cinerea extract in acetone and C. viminalis extract in isopropanol were highly effective against Aedes albopictus larvae with LC50 value 64.57, 71.34ppm respectively. Acetone extract of P.  juliflora found to be strong oviposition-deterrent which inhibited >2 fold egg laying (OAI-0.466) at 100ppm. Conclusion: Vernonia cinerea and C. viminallis leaf extracts have the potential to be used as larvicide and P.juliflora as an oviposition-deterrent for the control of Ae. albopictus mosquito

Midgut Microbial Community of <i>Culex quinquefasciatus</i> Mosquito Populations from India

<div><p>The mosquito <i>Culex quinquefasciatus</i> is a ubiquitous species that serves as a major vector for west nile virus and lymphatic filariasis. Ingestion of bloodmeal by females triggers a series of physiological processes in the midgut and also exposes them to infection by these pathogens. The bacteria normally harbored in the midgut are known to influence physiology and can also alter the response to various pathogens. The midgut bacteria in female <i>Cx. quinquefasciatus</i> mosquitoes collected over a large geographical area from India was studied. Examination of 16S ribosomal DNA amplicons from culturable microflora revealed the presence of 83 bacterial species belonging to 31 bacterial genera. All of these species belong to three phyla i.e. Proteobacteria, Firmicutes and Actinobacteria. Phylum Proteobacteria was the most dominant phylum (37 species), followed by Firmicutes (33 species) and Actinobacteria (13 species). Phylum Proteobacteria, was dominated by members of γ-proteobacteria class. The genus <i>Staphylococcus</i> was the largest genus represented by 11 species whereas <i>Enterobacter</i> was the most prevalent genus and recovered from all the field stations except Leh. Highest bacterial prevalence was observed from Bhuj (22 species) followed by Nagrota (18 species), Masimpur (18 species) and Hathigarh (16 species). Whereas, least species were observed from Leh (8 species). It has been observed that individual mosquito harbor extremely diverse gut bacteria and have very small overlap bacterial taxa in their gut. This variation in midgut microbiota may be one of the factors responsible for variation in disease transmission rates or vector competence within mosquito population. The present data strongly encourage further investigations to verify the potential role of the detected bacteria in mosquito for the transmission of lymphatic filariasis and west nile virus. To the best of our knowledge this is the first study on midgut microbiota of wild <i>Cx. quinquefasciatus</i> from over a large geographical area.</p></div

Pair wise matrix of common species (Upper half) and Sφrrensen similarity index (Lower half).

<p>Pair wise matrix of common species (Upper half) and Sφrrensen similarity index (Lower half).</p

Collection sites of <i>Culex quinquefasciatus</i> mosquito in India.

<p>1: Jamnagar(JMN), 2: Bhuj(BHJ), 3: Barmer(BAR), 4: Jodhpur(JOD), 5: Bathinda(BHT), 6: Amritsar(ASR), 7: Nagrota(NAG), 8: Leh(LEH), 9: Hathigarh(HGR), 10: Masimpur(MSM).</p

of bacterial species identified from <i>Cx. quinquefasciatus</i> midgut and their occurrence in each location with their sequence accession number.

<p>of bacterial species identified from <i>Cx. quinquefasciatus</i> midgut and their occurrence in each location with their sequence accession number.</p

showing occurrence of bacterial taxa identified, Good's coverage and diversity indices at 10 different field stations.

<p>showing occurrence of bacterial taxa identified, Good's coverage and diversity indices at 10 different field stations.</p