K. John Ravindran

Screening of twenty five plant extracts for larvicidal activity against Culex quinquefasciatus Say (Diptera: Culicidae)

Abstract Objective To determine the larvicidal activity of twenty five plant extracts against Culex quinquefasciatus ( Cx. quinquefasciatus ). Methods The larvicidal activity was determined against the third instar larvae of Cx. quinquefasciatus at 1 000 ppm concentration. Larval mortality was assessed after 24 and 48 h. Results The hexane extracts of Cleistanthus collinus ( C. collinus ) and Murraya koeingii ( M. koeingii ) plants showed 100 percent mortality at 24 h bioassay followed by diethyl ether, dichloromethane and ethyl acetate extracts of C. collinus, Leucas aspera ( L. aspera ), Hydrocotyle javanica ( H. javanica ), M. koeingii, Sphaeranthus indicus ( S. indicus ) and Zanthoxylum limonella ( Z. limonella ) after 48 h exposure. Conclusions The results indicate larvicidal activity against Cx. quinquefasciatus and further investigations are needed to elucidate this activity against a wide range of all stages of mosquito species and also the active ingredients of the extract responsible for larvicidal activity should be identified.

GIS based malaria information management system for urban malaria scheme in India

A GIS based information management system has been developed to help Urban Malaria Control in India. The basic objective is to develop a model to assist planning and implementation of a suitable control measure. The system can help in: (i) identifying high receptive areas in time and space domain; (ii) identifying risk factors for high receptivity; (iii) monitoring and evaluating control measures. To demonstrate this system, information on 33 parameters and malaria cases has been attached to a digitised map of Dindigul, an urban town in Tamil Nadu. Functionalities of the system and its utility are described in this paper. A GIS based information management system ensures that if a localised spurt of the disease occurs, it can be associated rapidly with a likely cause, a specific vector, and a probable human source, so that appropriate preventive action can be taken to arrest any rising trend.

Chloroquine efficacy studies confirm drug susceptibility of Plasmodium vivax in Chennai, India.

BackgroundAssessing the Plasmodium vivax burden in India is complicated by the potential threat of an emerging chloroquine (CQ) resistant parasite population from neighbouring countries in Southeast Asia. Chennai, the capital of Tamil Nadu and an urban setting for P. vivax in southern India, was selected as a sentinel site for investigating CQ efficacy and sensitivity in vivax malaria.MethodsCQ efficacy was evaluated with a 28-day in vivo therapeutic study, while CQ sensitivity was measured with an in vitro drug susceptibility assay. In both studies, isolates also underwent molecular genotyping to investigate correlations between parasite diversity and drug susceptibility to CQ. Molecular genotyping included sequencing a 604 base pair (bp) fragment of the P. vivax multidrug resistant gene-1 (Pvmdr1) for single nucleotide polymorphisms (SNPs) and also the amplification of eight microsatellite (MS) loci located across the genome on eight different chromosomes.ResultsIn the 28-day in vivo study (N=125), all subjects were aparasitaemic by Day 14. Passive case surveillance continuing beyond Day 28 in 22 subjects exposed 17 recurrent infections, which ranged from 44 to 148 days post-enrollment. Pvmdr1 sequencing of these recurrent infections revealed that 93.3% had identical mutant haplotypes (958M/Y976/1076L) to their baseline Day 0 infection. MS genotyping further revealed that nine infection pairs were related with ≥75% haplotype similarity (same allele at six or more loci). To test the impact of this mutation on CQ efficacy, an in vitro drug assay (N=68) was performed. No correlation between IC50 values and the percentage of ring-stage parasites prior to culture was observed (rsadj: -0.00063, p = 0.3307) and the distribution of alleles among the Pvmdr1 SNPs and MS haplotypes showed no significant associations with IC50 values.ConclusionsPlasmodium vivax was found to be susceptible to CQ drug treatment in both the in vivo therapeutic drug study and the in vitro drug assay. Though the mutant 1076L of Pvmdr1 was found in a majority of isolates tested, this single mutation did not associate with CQ resistance. MS haplotypes revealed strong heterogeneity in this population, indicating a low probability of reinfection with highly related haplotypes.

Bioefficacy of botanical insecticides against the dengue and chikungunya vector Aedes aegypti (L.) (Diptera: Culicidae)

Abstract Objective To determine the bioefficacy of plant extracts viz ., whole plants of Sphaeranthus indicus (Asteraceae) and Citrullus colocynthis (Cucurbitaceae), leaves of Abutilon indicum (Malvaceae), Cleistanthus collinus (Euphorbiaceae), Leucas aspera (Lamiaceae) and Murraya koenigii (Rutaceae), and aerial parts of Hyptis suaveolens (Lamiaceae) against the dengue and chikungunya vector Aedes aegypti . Methods The larvicidal activity was determined against the early third instar larvae at concentrations of 250, 500, 750 and 1000 ppm. Larval mortality was assessed after 24 h. Results The ethyl acetate extract of Sphaeranthus indicus (201.11ppm) and hexane extract of Abutilon indicum (261.31ppm) was found to be effective. Conclusions Further in-depth investigations on the crude extract/phytotoxic compounds of Sphaeranthus indicus are needed to elucidate the larvicidal activity against a wide range of all stages of mosquito species and also the active ingredients of the extract responsible for larvicidal activity in Aedes aegypti should be identified, and small scale field trials are needed for usage of this plant as a mosquitocidal agent.

In vitro antioxidant activity of Ageratum houstonianum Mill. (Asteraceae)

Abstract Objective To determine the antioxidant property of Ageratum houstonianum leaves. Method The present study was conducted in three different solvent extracts of leaves of Ageratum houstonianum Mill. (Asteraceae) to evaluate the antioxidant properties such as 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radicals which were carried out at various concentrations under in vitro condition. Results It was found that ethyl acetate extract could scavenge both the oxidants at 500μg/mL with high percentage inhibition (88.26 ±0.35) of DPPH, and in the case of hydroxyl radicals the maximum percentage inhibition was 75.81 ±0.39, which were found to be greater in ethyl acetate extract than in positive controls such as Butylated hydroxytoluene (BHT) and ascorbic acid. The next higher inhibitory extract was found to be methanol. Conclusion This shows that the plant Ageratum houstonianum may be a potent source of natural antioxidant.