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Background: Gujarat State has been witnessing large scale urbanization, in last two decades, resulting changes in local environment and microclimate may have also influenced the resting, feeding habits and development of Anopheles culicifacies sensu 1ato. Therefore, a systematic longitudinal study was undertaken to know the bionomics of An. culicifacies s.l. in present study. Methods: The study was conducted in four sentinel villages in Kheda and Panchmahal Districts. The mosquitoes resting indoors and outdoors were collected in early morning hours, using mouth aspirator, pyrethrum space spray and light traps. Mosquito landing collections on human volunteers was carried out from dusk to dawn. Species composition, abundance, seasonal prevalence, resting behavior (Endophily and Exophily), sibling species composition, vector potential and insecticide susceptibility status of malaria vectors was studied. Results: Six Anopheles species were collected, An. subpictus s.l. was the predominant species followed by An. culicifacies s.l., a known malaria vector was resting indoor and zoophagic behaviour. Anopheles culicifacies, sibling species B (89%) was found. The sporozoite rate (%) and entomological inoculation rate in Kheda was 2.33%, 3.09 per bite/ person/ annum and they were 1.05% and 0.475 bite/person/annum in Panchmahal, respectively. Anopheles culicifacies s.l. was found possible resistance to alpha-cypermethrin. Conclusion: Anopheles culicifacies s.l. showed endophillic, zoophagic behaviour and found possible resistance to alpha- cypermethrin. Early biting behaviour of An. culicifacies s.l. in this area is a cause of concern. Therefore, there is need for frequent monitoring and evaluation of vector control measures in order to achieve the elimination target of malaria in this area. [ABSTRACT FROM AUTHOR]

Abstract Background Chloroquine resistance (CQR) phenotype in Plasmodium falciparum is associated with mutations in pfcrt and pfmdr-1 genes. Mutations at amino acid position 72-76 of pfcrt gene, here defined as pfcrt haplotype are associated with the geographic origin of chloroquine resistant parasite. Here, mutations at 72-76 and codon 220 of pfcrt gene and N86Y pfmdr-1 mutation were studied in blood samples collected across 11 field sites, inclusive of high and low P. falciparum prevalent areas in India. Any probable correlation between these mutations and clinical outcome of CQ treatment was also investigated. Methods Finger pricked blood spotted on Whatman No.3 papers were collected from falciparum malaria patients of high and low P. falciparum prevalent areas. For pfcrt haplotype investigation, the parasite DNA was extracted from blood samples and used for PCR amplification, followed by partial sequencing of the pfcrt gene. For pfmdr-1 N86Y mutation, the PCR product was subjected to restriction digestion with AflIII endonuclease enzyme. Results In 240 P. falciparum isolates with reported in vivo CQ therapeutic efficacy, the analysis of mutations in pfcrt gene shows that mutant SVMNT-S (67.50%) and CVIET-S (23.75%) occurred irrespective of clinical outcome and wild type CVMNK-A (7.91%) occurred only in adequate clinical and parasitological response samples. Of 287 P. falciparum isolates, SVMNTS 192 (66.89%) prevailed in all study sites and showed almost monomorphic existence (98.42% isolates) in low P. falciparum prevalent areas. However, CVIETS-S (19.51%) and CVMNK-A (11.84%) occurrence was limited to high P. falciparum prevalent areas. Investigation of pfmdr-1 N86Y mutation shows no correlation with clinical outcomes. The wild type N86 was prevalent in all the low P. falciparum prevalent areas (94.48%). However, mutant N86Y was comparably higher in numbers at the high P. falciparum prevalent areas (42.76%). Conclusions The wild type pfcrt gene is linked to chloroquine sensitivity; however, presence of mutation cannot explain the therapeutic efficacy of CQ in the current scenario of chloroquine resistance. The monomorphic existence of mutant SVMNT haplotype, infer inbreeding and faster spread of CQR parasite in areas with higher P. vivax prevalance and chloroquine exposure, whereas, diversity is maintained in pfcrt gene at high P. falciparum prevalent areas.

Abstract Background Rainfall variability and associated remote sensing indices for vegetation are central to the development of early warning systems for epidemic malaria in arid regions. The considerable change in land-use practices resulting from increasing irrigation in recent decades raises important questions on concomitant change in malaria dynamics and its coupling to climate forcing. Here, the consequences of irrigation level for malaria epidemics are addressed with extensive time series data for confirmed Plasmodium falciparum monthly cases, spanning over two decades for five districts in north-west India. The work specifically focuses on the response of malaria epidemics to rainfall forcing and how this response is affected by increasing irrigation. Methods and Findings Remote sensing data for the Normalized Difference Vegetation Index (NDVI) are used as an integrated measure of rainfall to examine correlation maps within the districts and at regional scales. The analyses specifically address whether irrigation has decreased the coupling between malaria incidence and climate variability, and whether this reflects (1) a breakdown of NDVI as a useful indicator of risk, (2) a weakening of rainfall forcing and a concomitant decrease in epidemic risk, or (3) an increase in the control of malaria transmission. The predictive power of NDVI is compared against that of rainfall, using simple linear models and wavelet analysis to study the association of NDVI and malaria variability in the time and in the frequency domain respectively. Conclusions The results show that irrigation dampens the influence of climate forcing on the magnitude and frequency of malaria epidemics and, therefore, reduces their predictability. At low irrigation levels, this decoupling reflects a breakdown of local but not regional NDVI as an indicator of rainfall forcing. At higher levels of irrigation, the weakened role of climate variability may be compounded by increased levels of control; nevertheless this leads to no significant decrease in the actual risk of disease. This implies that irrigation can lead to more endemic conditions for malaria, creating the potential for unexpectedly large epidemics in response to excess rainfall if these climatic events coincide with a relaxation of control over time. The implications of our findings for control policies of epidemic malaria in arid regions are discussed.

Abstract Background Malaria vectors have acquired widespread resistance to many of the currently used insecticides, including synthetic pyrethroids. Hence, there is an urgent need to develop alternative insecticides for effective management of insecticide resistance in malaria vectors. In the present study, chlorfenapyr was evaluated against Anopheles culicifacies and Anopheles stephensi for its possible use in vector control. Methods Efficacy of chlorfenapyr against An. culicifacies and An. stephensi was assessed using adult bioassay tests. In the laboratory, determination of diagnostic dose, assessment of residual activity on different substrates, cross-resistance pattern with different insecticides and potentiation studies using piperonyl butoxide were undertaken by following standard procedures. Potential cross-resistance patterns were assessed on field populations of An. culicifacies. Results A dose of 5.0% chlorfenapyr was determined as the diagnostic concentration for assessing susceptibility applying the WHO tube test method in anopheline mosquitoes with 2 h exposure and 48 h holding period. The DDT-resistant/malathion-deltamethrin-susceptible strain of An. culicifacies species C showed higher LD50 and LD99 (0.67 and 2.39% respectively) values than the DDT-malathion-deltamethrin susceptible An. culicifacies species A (0.41 and 2.0% respectively) and An. stephensi strains (0.43 and 2.13% respectively) and there was no statistically significant difference in mortalities among the three mosquito species tested (p > 0.05). Residual activity of chlorfenapyr a.i. of 400 mg/m2 on five fabricated substrates, namely wood, mud, mud+lime, cement and cement + distemper was found to be effective up to 24 weeks against An. culicifacies and up to 34 weeks against An. stephensi. No cross-resistance to DDT, malathion, bendiocarb and deltamethrin was observed with chlorfenapyr in laboratory-reared strains of An. stephensi and field-caught An. culicifacies. Potentiation studies demonstrated the antagonistic effect of PBO. Conclusion Laboratory studies with susceptible and resistant strains of An. culicifacies and An. stephensi, coupled with limited field studies with multiple insecticide-resistant An. culicifacies have shown that chlorfenapyr can be a suitable insecticide for malaria vector control, in multiple-insecticide-resistant mosquitoes especially in areas with pyrethroid resistant mosquitoes.

Deemed University, Deonar, Bombay, India Journal of Asian and African Studies Vol.22 (1987) pp. 87-95 [Research Communication] In the present paper, an attempt has been made to estimate trends in [...]