Insecticide susceptibility status of Phlebotomus argentipes, a vector of visceral leishmaniasis in different foci in three states of India.

Background & objectives: Phlebotomus argentipes is the vector for visceral leishmaniasis in India. The development of resistance in kala-azar vector to DDT has been reported from various parts of India. The main objective of this study was to generate information on insecticides susceptibility status of P. argentipes to DDT, malathion and deltamethrin in different parts in three states of India. Methods: Phlebotomus argentipes were collected from different villages, identified and used to investigate the susceptibility status against DDT, malathion and deltamethrin as per the WHO standard methods. Results: Phlebotomus argentipes was resistant to DDT in different areas, viz. PHCs Murumgaon in Maharashtra; Ramgarh in Jharkhand; Kodah, Falka, Mahua and Lalganj in Bihar. In Phulwari Shareef PHC of Patna district in Bihar, DDT produced 89% mortality in P. argentipes, indicating resistant/tolerance (verification required) to DDT. The corrected percent mortality to malathion (5%) in different areas ranged between 98 and 100%; and to deltamethrin (0.05%) between 98.4 and 100%. The results showed that the tested P. argentipes are susceptible to malathion and deltamethrin. Conclusion: Phlebotomus argentipes are still susceptible to malathion and deltamethrin, but resistant to DDT. The susceptibility status of P. argentipes should be monitored regularly in diversified situations to ascertain the judicious use of insecticides being used for indoor residual spraying in the programme for rational use of appropriate insecticide.

Situation Analysis of Malaria in Godda District of Jharkhand During Malaria Epidemic.

The epidemiological and entomological investigations were carried out in 18 tribal villages of Godda district of Jharkhand state revealed average slide positivity rate (SPR) 9.9% and slide positivity rate for Plasmodium falciparum (SfR) 5.0%, respectively. P. falciparum was the dominant parasite accounting 51.2 per cent of the total infections. All the villages are situated in the deep forest and forest fringes. A total of 416 blood slides were collected and examined. Out of which 41 slides were found positive for malaria parasite (21 positive for P. falciparum and 20 positive for P. vivax). All the positive cases were treated with Blister Packs of anti-malarial of chloroquine and primaquine as per NBVDCP schedule to prevent further transmission of malaria, which were available. Rapid diagnostic Kits were used selectively only on the recommendation of the Physician/Medical Officer. Results of house to house fever survey indicated the presence of high percentage of symptomatic carriers of malaria parasites in the local population and in our study Pf % is more than reported data by District Malaria Office, Godda district, Jharkhand. In entomological studies, for mosquito fauna with reference to both Anopheline, 11 species belonging to one genus Anopheles were collected and identified during the survey; among them some species were most prevalent. A total of 599 mosquitoes were recorded and average density of mosquitoes recorded was 13.19 in human dwellings and 86.11 in cattle sheds.

Studies on mosquito larvicidal properties of Eucalyptus citriodora Hook (family-Myrtaceae).

Hexane extract obtained from leaves of Eucalyptus citriodora Hook was tested against larvae of Anopheles stephensi Liston, Culex quinquefasciatus Say and Aedes aegypti Linn to assess its toxicity and growth inhibiting activity. The results showed better activity of hexane extract against larvae of An. stephensi Liston as compared to the larvae of Cx. quinquefasciatus Say and Ae. aegypti Linn. The LC50 values against IVth instar larvae of three species were 69.86, 81.12 & 91.76 ppm respectively after 24 hours and 26.7, 29.9 & 38.8 ppm respectively after 72 hours. At lowest concentration viz. 10 ppm, 73% larvae of An. stephensi Liston failed to emergence as adult mosquito while in Cx. quinquefasciatus Say and Ae. aegypti Linn only 10 & 6% larvae failed to emerge. Further observations showed some morphological abnormalities in same pupae which could not moult normally. These results clearly indicated growth inhibition effect of the hexane extract of Eucalyptus against mosquito larvae, particularly Anopheles species. Thus Eucalyptus citriodora Hook, which is commonly found in Northern India, has a great potential for the development of an eco-friendly herbal insecticidal product for control of mosquito breeding.

Laboratory study on larvicidal properties of leaf extract of Calotropis procera (Family-Asclepiadaceae) against mosquito larvae.

Fresh leaf extract of milkweed (Calotropis procera) showed larvicidal properties against mosquito larvae of Anopheles stephensi, Culex quinquefasciatus and Aedes aegypti. Methanolic extracts of the same plant were, however, more effective as larvicide. C. procera is a weed growing in uncultivated soils as well as in dry, arid zones in Indian subcontinent throughout the year. The results of this study suggest the utility of milkweed as potential technology for control of mosquito larvae.

Evaluation of pirimiphos-methyl (50% EC) against the immatures of Anopheles stephensi/An. culicifacies (malaria vectors) and Culex quinquefasciatus (vector of bancroftian filariasis).

BACKGROUND & OBJECTIVES: In India, temephos and fenthion are used as larvicides in fresh and polluted waters. Since use of same insecticide may precipitate resistant, as an alternative bioefficacy of pirimiphos-methyl--an organophosphorus insecticide was evaluated against immatures of Anopheles and Culex species in different breeding habitats in District Ghaziabad (U.P.) and Goa. METHODS: Laboratory bioassays were carried out using standard WHO procedure. LC50 and LC90 were calculated using Probit analysis. Abbott's formula was used to calculate per cent corrected mortality in laboratory exposures while, Mulla's formula was applied for calculating per cent reduction in mosquito immatures under field conditions. RESULTS: Pirimiphos-methyl was found to be most effective against larvae of An. stephensi followed by An. culicifacies and Cx. quinquefasciatus. The LC50 and LC90 values against three species were 0.023, 0.032 and 0.04 ppm; and 0.045, 0.057 and 0.114 ppm respectively. In field, pirimiphos-methyl @ 200 g a.i./ha against Anopheles species and @ 300 g a.i./ha against Culex species can produce > 80% reduction in density of immatures up to one week in different habitats. Pirimiphos-methyl < 0.25 ppm is not toxic to fish. INTERPRETATION & CONCLUSION: Pirimiphos-methyl is more effective against anophelines in clean water than culicines in polluted water. This larvicide should not be used at a concentration above 0.25 ppm in habitats harbouring the larvivorous fish.

Laboratory studies on the predatory potential of dragon-fly nymphs on mosquito larvae.

Biocontrol potential of dragonfly nymph, Brachythemis contaminata Fabricius against the larvae of Anopheles stephensi, Culex. quinquefasciatus and Aedes aegypti was studied under laboratory conditions. It was found that dragonfly nymph had highest predation efficacy against An. stephensi followed by Cx. quinquefasciatus and Ae. aegypti. Feeding rate increased with decrease in prey size/stage. Analysis of data indicated that dragonfly nymphs have good predatory potential and can be used as a biological control agent for control of mosquito breeding.

Investigation of malaria outbreak in Bahraich district, Uttar Pradesh.

BACKGROUND & OBJECTIVES: Based on the reports of 139 fever related deaths in Jarwal primary health centre (PHC) of Bahraich district, Uttar Pradesh (UP) during April to September 1999, a study was undertaken to explore the possibility of outbreak of Plasmodium falciparum malaria in the area and reasons of outbreak. METHODS: The study was undertaken during September-October 1999 in Bahraich district, UP. The study included a parasitological and an entomological survey. Blood slides from fever cases were collected and examined following standard procedures for detection of species and stage of parasite. The resting adult mosquitoes were collected from human dwellings and cattle sheds from selected villages. Susceptibility status of Anopheles culicifacies to 4 per cent DDT and 0.05 per cent deltamethrin was determined under laboratory conditions following the WHO procedure. In vitro drug sensitivity of P. falciparum to chloroquine was also estimated. RESULTS: Overall slide positivity rate (SPR) was found to be 33.8 with a preponderance of P. falciparum (88.4%). There was an outbreak of Pf malaria in Jarwal and surrounding areas as well. Foci of P. falciparum malaria were found in Jarwal, Fakharpur and Hazoorpur PHCs around Kaisarganj PHC. In addition, P. falciparum cases, were also reported from Motipur and Tejwapur. INTERPRETATION & CONCLUSION: Poor surveillance of affected areas resulting in low annual parasite incidence (API), lack of insecticidal spray in the currently affected PHCs as the API was less than 2 and development of resistance in P. falciparum to chloroquine were found as the possible reasons for the outbreak. It is recommended that surveillance be strengthened in all PHCs of Bahraich district to contain further extension of malaria in northeastern UP.

Laboratory evaluation of the biocontrol potential of Mesocyclops thermocyclopoides (Copepoda: Cyclopidae) against mosquito larvae.

Biocontrol potential of Mesocyclops thermocyclopoides against first instar larvae of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus was studied under laboratory conditions. It was found that M. thermocyclopoides had the highest predation efficacy against Ae. aegypti followed by An. stephensi and Cx. quinquefasciatus. There was a significant reduction in the predation efficacy of M. thermocyclopoides against Cx. quinquefasciatus in the presence of alternate food (p < 0.01). The cage simulation trial indicated that M. themocyclopoides has the potential to control Ae. aegypti breeding effectively in a container type of habitat.

The biology and predatory potential of notonectid bug, Enithares indica (Fabr) against mosquito larvae.

The biology of a notonectid bug Enithares indica against immatures of Anopheline, Culicine and Aedine mosquitos was studied in the laboratory. The life cycle of the bug consists of the egg and five nymphal stages and takes about 64 +/- 1.54 days for completion. All stages of E. indica have good predatory potential. It can be used as a biological control agent in an integrated disease vector control program.