Laboratory studies on mosquito larvicidal efficacy of aqueous & hexane extracts of dried fruit of Solanum nigrum Linn.

Background & objectives: Aqueous and organic solvent extracts of plants/plant parts were effective in killing the mosquito larvae. Comparative efficacy of the aqueous and hexane extracts of dried fruit of Solanum nigrum was tested against five laboratory colonized strains of mosquito species, namely Anopheles culicifacies species A, An. culicifacies species C, An. stephensi, Culex quinquefasciatus and Aedes aegypti to assess the possibility for use of these extracts for their control. Methods: Concentrations of aqueous extract of dried fruit in the range of 62.5 to 2000 ppm and hexane extract of dried fruit in the range of 0.781 to 150 ppm were used in bioassays. The mortality data were subjected to log probit regression analysis to detertmine the median lethal concentrations (LC50 and LC90) to kill 50 and 90 per cent of the treated larvae of the respective species. Results: All the five species registered 100 per cent mortality in larval bioassays at 1000 ppm with aqueous extract and at 100 ppm with hexane extract of dried fruit. In bioassays with aqueous extract An. culicifacies species A registered the lowest LC50 of 208.5 ppm (range-208.5-359 ppm for different mosquito species) while with hexane extract, An. stephensi registered the lowest LC50 of 6.25 ppm (6.25- 17.63 ppm for different mosquito species). The LC50 of aqueous extract was 13-39 fold higher than the values of hexane extract of dried fruit for different species. The calculated LC90 for hexane extract of dried fruit for different species was in the range of 43.38-95.28 ppm. Interpretation & conclusion: Hexane extract showed good mosquito larvicidal efficacy than that of the aqueous extract. The calculated LC 90 for the extract for different species was below 100 ppm and could be effective for comprehensive control of disease vectors.

Impact of DDT spraying on malaria transmission in Bareilly District, Uttar Pradesh, India.

BACKGROUND & OBJECTIVES: Impact of indoor residual spraying of DDT on malaria transmission and vector density was evaluated in six villages of Shergarh PHC, Bareilly district, Uttar Pradesh under the operational condition of National Vector Borne Disease Control Programme (NVBDCP) from July 2001 to March 2002 (one transmission season only). METHODS: Two rounds of DDT (50% WDP) spraying @ 1 g/m2 were done both in the experimental and control villages by the state health authorities. The spraying in experimental villages was supervised by Malaria Research Centre (MRC) whereas the district health authorities supervised the operation in control villages. Mass blood surveys were made three times--before the first round, in between the first and second rounds and after the second round of spraying. The blood smears were examined by the trained microscopists of MRC, Haldwani. From the above examinations epidemiological indicators such as slide positivity rate (SPR), slide falciparum rate (SFR) and infant parasite rate (IPR) were calculated. All malaria positive cases were given radical treatment as per NVBDCP schedule. Entomological parameters such as per man hour mosquito density, parity rate, gonotrophic condition and adult susceptibility status of Anopheles culicifacies to diagnostic dosages of DDT (4%) were monitored as per the standard techniques. RESULTS: A total of 988.5 kg of DDT was consumed during two rounds of spray. The house coverage varied from 87 to 95.3%. Parasitological evaluation revealed significant reduction in malaria cases (p < 0.0005) and infant parasite rate declined from 2.9 to 0%. Entomological observations revealed considerable reduction in the density of malaria vector An. culicifacies despite of its 21.4% mortality against DDT test papers. INTERPRETATION & CONCLUSION: The overall results of the study revealed that DDT is still a viable insecticide in indoor residual spraying owing to its effectivity in well supervised spray operation and high excito-repellency factor.

Morphotaxonomic studies to identify the members of the Anopheles subpictus Grassi (Diptera: Culicidae) species complex in riverine villages of District Sonepat, Haryana State, India.

Anopheles subpictus was reported to be a complex of four sibling species provisionally designated as species A, B, C and D. Present studies in District Sonepat, Haryana have revealed the sympatricity of species A, C and D based on the reported distinct morphotaxanomical identification characters in different life stages of the mosquito. Studies on field collected adult mosquitoes and isofemale progeny did not show variations in the prevalence of sibling species and also showed a possibility of use of a single reported morphological character in a given life stage for the identification of the members of this complex.

Assessment of therapeutic efficacy of chloroquine and sulphadoxine-pyrimethamine in uncomplicated falciparum malaria.

A standardised protocol has been developed by World Health Organization (CDS/RBM/2002) to assess the efficacy of common antimalarials in the treatment of clinically manifested infection with uncomplicated P. falciparum malaria for areas with low to moderate transmission. The therapeutic efficacy protocol is based on clinical and parasitological responses of the patients and it has the purpose of determining the practical efficacy of the drug regimen in study areas with the ultimate objective of ascertaining its continued usefulness or the necessity for replacing it in the routine treatment. Present study has been conducted at seven sites--Kathiatali and Simonabasti of District Nowgaon, Assam; Sonapur and Boko of District Kamrup, Assam; Keonjhar Town, Padampur and Basudebpur of District Keonjhar, Orissa. In order to reduce the patient recruitment time, health centre close to well-defined community was identified to conduct the activities at peak malaria season by selecting local pockets and organising mobile clinics. Microscopically confirmed cases of P. falciparum were enrolled according to the criteria for inclusion and exclusion. Treatment with recommended drug was given under supervision and a follow-up schedule at various intervals for 28 days was maintained. In chloroquine (CQ) study areas, wherever patients showed treatment failure, they were treated with second line drug--sulphadoxine-pyrimethamine (SP) combination and then followed-up as per study protocol. It was observed that 30% cases showed treatment failure to CQ in District Nowgaon, where revised drug policy has already been introduced. In Kamrup district, treatment failure with CQ was found to be less than 25%, which denotes the said regimen is still effective. Almost all the patients from Padampur and Basudebpur of District Keonjhar responded to CQ, treatment failure was noticed only in two patients (3%). The antifolate combination found to be fully effective as second line and also as first line wherever revised drug policy has been introduced.