Persistent foci of falciparum malaria among tribes over two decades in Koraput district of Odisha State, India.

BACKGROUND: Koraput, a predominantly tribe-inhabited and one of the highly endemic districts of Odisha State that contributes a substantial number of malaria cases to the India's total. Control of malaria in such districts would contribute to change the national scenario on malaria situation. Hence, a study was carried out to measure the magnitude of malaria prevalence in the district to strengthen the malaria control activities. METHODS: Prevalence of malaria was assessed through a sample blood survey (SBS) in seven randomly selected community health centres (CHCs). Individuals of all age groups in the villages selected (one in each subcentre) were screened for malaria infection. Both thick and thin smears were prepared from blood samples collected by finger prick, stained and examined for malaria parasites searching 100 fields in each smear. The results of a blood survey (n = 10,733) carried out, as a part of another study, during 1986-87 covering a population of 17,722 spread in 37 villages of Koraput district were compared with the current survey results. Software SPSS version 16.0 was used for data analysis. RESULT: During the current study, blood survey was done in 135 villages screening 12,045 individuals (16.1% of the total population) and among them, 1,983 (16.5%) were found positive for malaria parasites. Plasmodium falciparum was the major malaria parasite species accounted for 89.1% (1,767) of the total positives; Plasmodium vivax and Plasmodium malariae accounted for 9.3% (184) and 0.2% (5), respectively. Gametocytes were found in 7.7% (n = 152) of the positive cases. The majority of parasite carriers (78.9%) were afebrile. The 1986-87 blood survey showed that of 10,733 people screened, 833 (7.8%) were positive for malaria parasites, 714 (85.7%) with P. falciparum, 86 (10.3%) with P. vivax, 12 (1.4%) with P. malariae and 21 (2.5%) with mixed infections. CONCLUSION: The results of the current study indicated a rising trend in transmission of malaria in Koraput district compared to the situation during 1986-87 and indicated the necessity for a focused and reinforced approach for the control of the disease by improving people's access to diagnosis and treatment and ensuring implementation of the intervention measures with adequate coverage and compliance.

Bionomics of Anopheles minimus and An. fluviatilis (Diptera: Culicidae) in east-central India, endemic for falciparum malaria: human landing rates, host feeding, and parity.

The host feeding of Anopheles minimus Theobald and An. fluviatilis James was studied in the villages of east-central India by conducting human landing collections between 1800 and 0600 hours at monthly intervals from May 2006 to July 2007. Four species of anopheline mosquitoes, An. minimus, An. fluviatilis, An. maculatus Theobald, and An. subpictus Grassi, were collected, the former two known vector species of malaria being the most abundant (97.1%). The An. minimus complex has been identified as sibling species A and An. fluviatilis complex as species S (90.9%) and T (9.1%). Both the species were prevalent throughout the year and obtained from landing collections indoors and outdoors. The average human landing density (HLD) of An. minimus and An. fluviatilis was 1.76 and 1.78 indoors and 1.71 and 1.56 per human per night outdoors, respectively. The HLD was relatively higher during the rainy season, although not significant in the case of An. fluviatilis. The human landing activity of An. minimus and An. fluviatilis occurred between 2000 and 0400 hours and peaked during 2300-0200 hours both indoors and outdoors.

In Silico analysis of voltage-gated sodium channel in relation to DDT resistance in vector mosquitoes.

The voltage-gated sodium channel (VGSC) is the target site for insecticides such as DDT and synthetic pyrethroids. A single base (A-T) change in the knock-down resistance (kdr) allele leads to an amino acid substitution at position 267 that confers the target-mediated resistance to DDT and synthetic pyrethroids in Anopheles gambiae. A theoretical model of the VGSC domain II that contains the site of mutation was constructed using the K;+ channel protein of Aeropyrum pernix as a template. The validated model with 88.6% residues in the favored region was subjected to the CASTp program that predicted 30 pockets in the modeled domain II for ligand interaction. In the model, at position 267, leucine was manually replaced with phenylalanine. When this altered model was subjected to the CASTp program, the search results showed the same number of pockets. The docking results indicate that DDT interacts with the modeled VGSC domain II at position 275 in the presence of leucine or in the presence of phenylalanine (binding energy =-5.32 kcal/mol, -6.21 kcal/mol). It appears from the results that the mutation at position 267 has no direct influence on the interaction of DDT with the target protein. Therefore, to understand the interaction affinity of DDT with the target and influence of the mutation on the existence of active sites/pockets in relation to ligand binding, a whole VGSC model is necessary.