The mosquitocidal activity of methanolic extracts of Lantana cramera root and Anacardium occidentale leaf: role of glutathione S-transferase in insecticide resistance.

Larvicidal activity of methanolic plant extracts of Lantana cramera (P1) root and Anacardium occidentale (P2) leaf was investigated against the larvae of the three mosquito species (Culex quinquefasciatus, Anopheles stephensi, and Aedes aegypti reared in the laboratory), and the respective glutathione S-transferase (GST) activity was analyzed as an index of protection against the extracts. The LC50 (extract concentration that shows 50% mortality) values of P1 extract for An. stephensi, Ae. aegypti, and Cx. quinquefasciatus were 132.55, 27.82, and 11.68 ppm, respectively, whereas those of P2 extract were 56.81, 912, and 10.79 ppm, respectively. In general, in the untreated groups, the level of GST activity was significantly higher in Ae. aegypti in comparison with An. stephesi and Cx. quinquefasciatus. However, the enzyme activity failed to show any response when treated with either of the plant extracts in Ae. aegypti. However, an increase in the GST activity was recorded in extract-treated larvae of both An. stephensi and Cx. quinquefasciatus. The results of the current study suggest that both the plant extracts show species-specific mosquitocidal potential. Induction of GST activities in survived An. stephensi and Cx. quinquefasciatus larvae suggests the role of this enzyme in conferring resistance to the plant extracts.

Emergence of chikungunya virus infection in Orissa, India.

From September through October 2006, an unknown disease characterized by acute onset of fever, joint pain with or without swelling, and maculopapular rash along with fatigue was reported from three villages of Cuttack and one village of Kendrapara district of Orissa, India, by the State Health Department. Upon learning this, a team from Regional Medical Research Centre (Indian Council of Medical Research), Bhubaneswar, Orissa, conducted an epidemiological investigation in the area. Household survey was carried out and clinical examination of the symptomatic individuals (n = 1289: Kendrapara, 752; Cuttack, 537) undertaken. Based on the recorded chikungunya (CHIK) fever symptoms, a vector-borne viral disease was considered for provisional diagnosis. Blood samples were collected from 217 symptomatic individuals; to confirm the diagnosis, sera were tested for anti-CHIK antibody (immunoglobulin M), which revealed 63% (64/101) and 40% (47/116) seropositivity in the samples from Kendrapara and Cuttack district, respectively. The illness was managed with analgesics like paracetamol. No death was recorded due to the illness. Entomological survey in the areas revealed the presence of Aedes mosquitoes: aegypti, albopictus, and vittatus. The per-man-hour density of Aedes vectors ranged from 0.8 to 7.6. High larval indices, house index >17% and Breteau index >70%, also indicated Aedes breeding in the area. The investigation documented circulation of CHIK in Orissa, India, and helped to take preventive steps in the outbreak area, with the suggested vector control measures.