A. Jebanesan

Repellent activity of Ferronia elephantum Corr. (Rutaceae) leaf extract against Aedes aegypti (L.).

The repellent activity of a methanol extract of Ferronia elephantum leaves against Aedes aegypti was studied in the laboratory. The percentage protection in relation to the dose method was used. The repellent activity at 1.0 and 2.5 mg/cm2 concentrations gave 100% protection up to 2.14 +/- 0.16 h and 4.00 +/- 0.24 h, respectively. The total percentage protection of Ferronia elephantum was 45.8% at 1.0 mg/cm2 and 59.0% at 2.5 mg/cm2 for 10 h.

Larvicidal efficacy of Pavonia zeylanica L. and Acacia ferruginea D.C. against Culex quinquefasciatus Say.

Larvicidal efficacy of leaf extracts of Pavonia zeylanica and Acacia ferruginea were tested against the late third instar larvae of Culex quinquefasciatus. The larval mortality was observed after 24 h of treatment. The LC50 values of P. zeylanica and A. ferruginea were 2214.7 and 5362.6 ppm, respectively.

Larvicidal and repellent activity of tetradecanoic acid against Aedes aegypti (Linn.) and Culex quinquefasciatus (Say.) (Diptera:Culicidae)

OBJECTIVE To investigate the larvicidal and repellent efficacy of tetradecanoic acid against Aedes aegypti (Ae. aegypti) L. and Culex quinquefasciatus (Cx. quinquefasciatus) Say (Diptera: Culicidae). METHODS Larvicidal efficacy of tetradecanoic acid was tested at various concentrations against the early third instar larvae of Ae. aegypti and Cx. quinquefasciatus. The repellent activity was determined against two mosquito species at three concentrations viz., 1.0,2.5 and 5.0 ppm under the laboratory conditions. RESULTS The tetradecanoic acid was found to be more effective against Cx. quinquefasciatus than Ae. aegypti larvae. The LC(50) values were 14.08 ppm and 25.10 ppm, respectively. Tetradecanoic acid showed lesser repellency against Ae. aegypti and Cx. quinquefasciatus. The highest repellency was observed in higher concentration of 5.0 mg/cm(2) provided 100% protection up to 60 and 90 min against Ae. aegypti and Cx. quinquefasciatus respectively. CONCLUSIONS From the results it can be concluded the tetradecanoic acid is a potential for controlling Cx. quinquefasciatus and Ae. aegypti mosquitoes.

Effect of leaf essential oil of Coccinia indica on egg hatchability and different larval instars of malarial mosquito Anopheles stephensi.

OBJECTIVE To assess the larvicidal and egg hatching inhibition property of the leaf essential oil of Coccinia indica (C. indica) against Anopheles stephensi (An. stephensi). METHODS The larvicidal potential of C. indica leaf essential oil was evaluated against 1st, 2nd, 3rd and 4th instars larvae of An. stephensi using WHO protocol. The 24h LC(50) and LC(90) values of the essential oil were determined following probit analysis. The egg hatching inhibition activity was also tested at 10, 20, 40, and 60 mg/L. The IC(50) value of essential oil was determined against eggs of An. stephensi. RESULTS The essential oil extracted from C. indica possessed excellent larvicidal and egg hatching inhibition activity against An. stephensi. The bioassays showed LC(50)-LC(90) of 54.3-140.3, 65.5-155.6, 86.8-180.7 and 95.3-192.6 for 1st, 2nd, 3rd, and 4th larval instars, respectively. The 50% egg hatching inhibition concentration (IC(50)) was noted at 16.5 mg/L. CONCLUSIONS The present finding suggest that the C. indica leaf essential oil provided an excellent potential for controlling An. stephensi mosquito at earlier stage of their life cycle.

Synergistic effect of Andrographis echioides and Cadaba trifoliata leaf extracts against larvae of dengue mosquito Aedes aegypti L

Abstract Objective The larvicidal potential of Andrographis echioides and Cadaba trifoliata leaf extract was tested separately against larvae of Aedes aegypti and also tested mixture of these two plant extracts for synergistic effect against the larvae. Methods Pulverized leaves of A. echioides and C. trifoliata were subjected separately to soxhlet extraction using organic solvent of ethanol. These two plant extracts were examined separately against 4th instar larvae of A.aegypti with gradually increasing concentration i.e. from 50 to 250mg/l using WHO protocol. To observe the synergistic effect, extracts of these two plants were mixed at different concentrations and tested against the larva. The 24h LC 50 values of individual plant extract and mixed extracts were determined following probit analysis. Results A. echioides extract shows more lethal effect than C. trifoliata extract towards larvae of A.aegypti with LC 50 values of 108.3 and 123.4 mg/l, respectively, whereas, synergistic larvicidal effect was found to be even more effective than the plant extract tested separately in terms of LC 50 being 68.3 mg/l. Conclusions From the results, it is evident that synergistic effect of A. echioides and C. trifoliata can be considered as a more powerful arsenal for the control of A.aegypti than the usage of these two extract separately.

Entomofaunal diversity of tree hole mosquitoes in Western and Eastern Ghats hill ranges of Tamilnadu, India

The distribution and abundance of various mosquito vectors is important in the determination of disease prevalence in disease endemic areas. The aim of the present study was to conduct regular entomological surveillance and to determine the relative abundance of tree hole mosquito species in Tamilnadu, India. In addition to this, the impact of weather-conditions on tree hole mosquito population were evaluated between June, 2014 and May, 2015. Six hills ranges viz., Anaimalai hills, Kodaikanal hills, Sitheri hills, Kolli hills, Yercaud hills, and Megamalai were selected, the immatures collected from tree holes by the help of suction tube. Collections were made at dusk and dawn at randomly selected 15 different tree species. The collected samples were stored and morphologically identified to species level in the laboratory. Mosquito diversity was calculated by Simpsons and Shannon-Weiner diversity indicies with spatial and temporal aspects. Over 2642 mosquitoes comprising the primary vectors of dengue, chickungunya, malaria, filariasis were identified. Other species collected from the fifteen sites in each hill during the study included Christophersiomyia annularis, Christophersiomyia thomsoni, Downsiomyia albolateralis, Downsiomyia nivea and Toxorhynchites splendens, etc. Study revealed high species diversity and relative density associated with different study sites. Based on the Shannon diversity index high number of species was recorded with Aedes pseudoalbopicta (0.0829) followed by Ae. aegypti (0.0805) and least species was recorded as Anopheles elegans (0.0059). The distribution of the primary vectors of DF along the high occurrence was evident with most study sites representing proportions of this vector population. This showed the high risk level associated with the livestock movement in amplification and circulation of the virus during the outbreaks. The findings of this study, therefore, demonstrated the potential vulnerability of nomadic communities to infection by arboviral diseases transmitted by mosquito vectors.

Diversity of mosquitoes and larval breeding preference based on physico-chemical parameters in Western Ghats, Tamilnadu, India

Abstract Objective To study the diversity and distribution of mosquitoes in Western Ghats of Coimbatore and Nilgiris District, Tamilnadu, India. Methods Random collections were carried out during August-2013 to July-2014 in cesspits, animal footprints, rock holes, tree holes, drainages at study areas of Marudhamalai, Valparai, Mettupalayam in Coimbatore District and Dhottapeta, Coonoor, Gudalur in Nilgiris District of Tamilnadu, India by using suction tube and kerosene pump. Mosquitoes were identified by standard entomological procedures. Results A total of 1 018 mosquitoes (larvae and pupae) were collected from all over the study areas comprising 6 genera and 23 species. They are, Culex mimulus, Culex pseudovishnui, Culex quinquefasciatus, Culex vishnui, Culex khazani, Culex uniformis, Heizmannia chandi, Heizmannia grenii, Heizmannia indica, Oclerotatus anureostriatus, Oclerotatus albotaeniatis, Oclerotatus deccanus, Oclerotatus gubernatoris, Aedes aegypti, Aedes albopictus, Aedes edwardsi, Aedes krombeini, Toxorhynchites minimus, Toxorhynchites splendens, Anopheles aitkenii, Anopheles barbirostris, Anopheles culiciformis and Anopheles maculatus. Shannon-Weaver diversity index, Margalefs index of richness and Simpsons dominance index was also studied. From 6 sites, the highest mosquitoes were collected from Marudhamalai (309) and the least mosquitoes were collected in Mettupalayam (68). The study determined whether physicochemical characteristics differ between habitats with high and low presence of mosquito larvae. Based on Margalefs index of richness (D mg ), the highest values were present in Mettupalayam (5.214) study area and the lowest in Marudhamalai (3.837). It can be concluded from Shanon-Weaver index of diversity that, the highest values were present in Mettupalayam (2.947) and the least value were in Gudalur (2.410) during the study period. Conclusions In areas with reservoirs of disease, mosquito abundance information can help to identify the areas at higher risk of disease transmission. The study identifies mosquito species density and diversity of culicine and anopheline larvae. Hence, this research contribution has more significance for basic biological research and developing control strategies for vector borne diseases.

Distribution study of tree hole mosquitoes (Diptera : Culicidae) during pre-and post-monsoon seasons in kolli hills of Eastern Ghats, Tamilnadu

The biodiversity and their relative abundance of tree hole breeding mosquitoes occurring in four localities (Anankadu, Solakkadu, Nigayanallur and Pallakkuli) of Kolli hills in Eastern Ghats, Tamilnadu, India, were studied between Premonsoon (May-June 2013) and Post monsoon (November-December 2013) period. Six species of mosquitoes belonged to 4 genera namely Aedes aegypti, A. albopictus, Culex uniformis, Orthopodomyia anopheloides, Toxorhynchites viridibasis, and T. rutilus were found to breed in tree holes frequently. The collected samples were studied by Simpson Index ‘D’(0.2073, 0.1753) and Brillouin Index ‘HB’(1.5486, 1.6186). It is concluded that the tree hole breeding mosquitoes in Kolli hills could act as vectors for the possible outbreak of mosquito borne disease.