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D R Bhattacharyya

Publications and source records attributed to D R Bhattacharyya.

At least 19 recordsLinked to original sources
PubMed2006

Molecular characterization and species identification of the Anopheles dirus and An. minimus complexes in north-east India using r-DNA ITS-2.

The sibling species composition of the Anopheles minimus and Anopheles dirus complexes is poorly known in the highly malarious north-eastern region of India where these two vector taxa are accountable for most of the malaria transmission among 30.7 million inhabitants. Prevalent members of these two complexes in this part of India were identified using sequences for the second internal transcribed spacer (ITS2) of ribosomal DNA. Anopheles baimaii (species D) of the An. dirus complex and An. minimus s.s. (species A) of the An. minimus complex were detected in Arunachal Pradesh, Assam, Meghalaya and Nagaland states. No intraspecific variation was observed in the ITS2 sequence (479bp) of An. baimaii whereas a single substitution was detected in the ITS2 sequence (372bp) of An. minimus from Nagaland state.

Animals↗
PubMed2005

Malaria transmission risk by the mosquito Anopheles baimaii (formerly known as An. dirus species D) at different hours of the night in North-east India.

The risk of acquiring malaria transmitted by Anopheles baimaii Sallum & Peyton, 2005, formerly known as An. dirus species D (Sallum et al., 2005) (Diptera: Culicidae), at different hours of the night in a forest-fringed village of Assam, North-east India was assessed through all-night mosquito landing catches during 1995-2000. An estimated overall mean biting rate of 36.1 bites/person/night (95% CI = 26.2-45.8), a sporozoite rate of 1.9% (95% CI = 1.1-2.9%) and a parous rate of 58.7% (95% CI = 55.3-62.0%) were recorded. Parous and sporozoite-positive females tended to be caught mainly before midnight. The effective entomological inoculation rate was the highest (0.249 positive bites/person/night) from 21.00 to 24.00 hours, suggesting that the second quartile of the night is the most risky period for malaria transmission by An. baimaii. Considering that approximately 21% of mean inoculations take place before 21.00 hours, it appears that there is a need for appropriate protective measures during the pre-bed time period to supplement the impact of insecticide-treated nets against An. baimaii in north-east India.

Animals↗
PubMed2005

Evaluation of chloroquine (CQ) and sulphadoxine/pyrimethamine (SP) therapy in uncomplicated falciparum malaria in Indo-Myanmar border areas.

Chloroquine (CQ) and sulphadoxine/pyrimethamine (SP) are two first-line antimalarials used under the existing Indian National Drug Policy in the north-eastern region of India bordering several countries including Myanmar. Although widespread resistance to antimalarials in Plasmodium falciparum has been reported from western Myanmar, information from the Indian side of the border is scarce. We studied the therapeutic response to CQ and SP at four sites in Changlang and Lohit, two administrative districts of Arunachal Pradesh bordering Myanmar. We monitored uncomplicated falciparum malaria patients after treatment with standard regimens of CQ and SP for 28 days following the revised in-vivo protocol of the World Health Organization. A total of 236 patients, 95 in the CQ group and 141 in the SP group, participated. We recorded 23.8% early treatment failures to CQ and 14.1% to SP; late clinical failures of 14.3 and 12.6%; late parasitological failures of 10.7 and 8.1% and adequate clinical and parasitological responses of 51.2 and 65.2%, respectively. The significantly different treatment failure rates seen in Chowkham (furthest from Indo-Myanmar border) and Jairampur/Nampong (nearest to Indo-Myanmar border) for chloroquine (Cox proportion hazard ratio 9.1, P<0.0001) and SP (Cox proportion hazard ratio 7.35, P=0.001) denote a non-response gradient to the two antimalarials extending from the international border. The gradient is probably indicative of the direction of movement of the drug-resistant P. falciparum parasite. The utility of chloroquine as the first-line drug under the present National Drug Policy in these areas needs reconsideration.

Adolescent↗
PubMed2005

Potential of Anopheles philippinensis-nivipes complex mosquitoes as malaria vector in north-east India.

Anopheles philippinensis-nivipes complex mosquitoes, captured in outdoor human landing catches and light traps in human dwellings from four different sites in Assam state and adjoining areas, were examined (n=1670) for the presence of circumsporozoite antigen (CSA) through enzyme linked immunosorbent assays (ELISA), using species specific capture monoclonal antibodies, of Plasmodium falciparum and two Plasmodium vivax polymorphs (Pv 210 and VK 247). In ELISA, 28 pools were found positive for CSA that accounted for minimum sporozoite rate of 1.7% (95% CI 1.11-2.41). Twenty five percent (7/28) of the positive pools were reactive for P. falciparum and between the two polymorphs of P. vivax, VK 247 was predominant with 77% (20/26) of all P. vivax positive pools. Results were suggestive of most likely involvement of Anopheles philippinensis-nivipes complex mosquitoes in malaria transmission in north-east India.

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PubMed2004

Role of the prevalent Anopheles species in the transmission of Plasmodium falciparum and P. vivax in Assam state, north-eastern India.

In north-eastern India, Anopheles minimus, An. dirus and An. fluviatilis are considered the three major vectors of the parasites causing human malaria. The role in transmission of the other Anopheles species present in this region is not, however, very clear. To examine the vectorial role of the more common anopheline mosquitoes, the heads and thoraces of 4126 female Anopheles belonging to 16 species (collected using miniature light traps set in human dwellings in a foothill village in the Jorhat district of Assam state) were tested, in ELISA, for the circumsporozoite proteins (CSP) of Plasmodium falciparum or the VK-210 and VK-247 polymorphs of P. vivax. Sixty-five pools of head-thorax homogenates, representing 10 different species of Anopheles, were found reactive, giving an overall minimum prevalence of infection (MPI) of 1.58%, with a 95% confidence interval (CI) of 1.21%-2.0%. Among the CSP-reactive pools of mosquitoes, 31% were positive only for P. falciparum, 45% only for P. vivax VK 247, 6% only for P. vivax VK 210, and 18% for both P. falciparum and P. vivax VK 247. The results indicate that not only the proven vector, An. minimus s.l. (MPI = 0.71%), but also several species of Anopheles previously considered unimportant in the epidemiology of malaria, especially An. aconitus (MPI = 3.95%), An. annularis (MPI = 5.8%), the An. hyrcanus group (MPI = 0.48%), An. kochi (MPI = 1.28%), the An. philippinensis-nivipes complex (MPI = 0.94%), and An. vagus (MPI = 3.87%), are important vectors in the foothills of Assam.

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PubMed2004

Taxonomical observations on Anopheles philippinensis/nivipes group mosquitoes in north-east India.

To examine the distribution pattern of Anopheles philippinensis and An. nivipes, mosquitoes belonging to An. philippinensis/nivipes group were collected from five sites in north-east Indian state of Assam and its adjoining areas and identified. Presence of both An. philippinensis and An. nivipes, with predominance of the latter taxon, was recorded with conformity on the basis of pupal paddle characteristics. Based on adult wing characters, 91.4% specimens were identified as An. philippinensis and 8.6% as An. nivipes with gradually increasing proportion of An. nivipes in westwardly direction. An. philippinensis/ nivipes was noted to be mid night biter, mainly exophagic and exclusively exophilic. Of the two species, An. philippinensis appears to be mostly anthropophilic and available in broken forest areas whereas An. nivipes seems to be mostly zoophilic and generally found in ecotone zones in plains areas.

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PubMed2002

Physico-chemical characteristics of breeding habitats of Anopheles dirus (Diptera:Culicidae) in Assam, India.

Larval ecology of Anopheles dirus, the main vector of forest malaria in north-eastern region of India, was studied in relation to physico-chemical characteristics of its breeding habitats in a rain forest area of Assam, India. Shady stream side pools, positive for the breeding of An. dirus, had significantly higher amounts of total hardness (P < 0.024) in comparison to negative pools of similar type. When compared with An. dirus negative breeding habitats, in hot-wet as well as in cool-dry seasons, An. dirus positive shady ground pools showed higher mean values of total alkalinity, hardness and chloride content, whereas lower pH, dissolved oxygen along with higher total alkalinity and hardness were possessed by An. dirus positive stream side pools. Specificity of breeding habitats of An. dirus in relation to its ecology has been discussed.

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PubMed2001

Estimation of vectorial capacity of Anopheles dirus (Diptera: Culicidae) in a forest-fringed village of Assam (India).

To estimate the vectorial capacity of Anopheles dirus, the main vector of forest malaria in the northeastern region of India, in order to gain an understanding of entomological factors related to malaria transmission in forest-fringe areas of Assam, India, an isolated village in the tropical rain forest-fringed area in the district of Dibrugarh, Assam, under the influence of An. dirus alone was studied. Data on various entomological variables required for computation of the vectorial capacity were generated in each month from June 1999 to May 2000 in the field using standard techniques. Malaria prevalence was also studied during the same period in the study village and correlated with the estimated vectorial capacity of An. dirus. Vectorial capacity of An. dirus was highest, 0.779 for Plasmodium vivax (Pv) and 0.649 for Plasmodium falciparum (Pf), during the hot-monsoon season (June-September) and decreased to 0.08 (Pv) and 0.07(Pf) in the temperate postmonsoon season (October-November) before attaining zero values in the cool-dry season (December-February). With increasing temperature in the temperate premonsoon season (March-May), vectorial capacity recorded was 0.119 and 0.82 for Pv and Pf, respectively. Significant positive correlation was seen between the estimated vectorial capacity of An. dirus and the number of new Pf (r = 0.86, p < 0.001) and Pv (r = 0.69, p < 0.02) cases in the study village in different months. Thus, this study highlights the pattern of malaria transmission by An. dirus in a forest-fringe area of Assam that begins in March, peaks in July/August, subsides by November, and remains interrupted between December and February. Measures for controlling malaria in forest-fringe areas should be scheduled accordingly.

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PubMed2000

Epidemiology of malaria outbreak (April/May, 1999) in Titabor Primary Health Centre, district Jorhat (Assam).

An investigation was undertaken of a malaria outbreak in the Primary Health Centre Titabor, district Jorhat, Assam during May/June 1999. The fever rate in the community since March 1999, was 44.4 per cent with an average case load of 2.5 per family. The fever cases peaked in the third week of May. Slide positive and slide falciparum rates in mass blood survey, in the study village were 16.1 and 14.5 per cent respectively with 90 per cent infection of Plasmodium falciparum. Males (SPR 17.5%) suffered relatively more than females (SPR 14.7%). Malaria prevalence was significantly less in individuals above 15 yr of age (SPR 11.0%) as compared to those below 15 yr (SPR 22.9%). Prevalence of malaria as well as mosquito densities in different clusters of the village were inversely related to the distance from the forested Naga hills. Anopheles minimus and A. dirus were collected in good numbers with comparatively higher densities of the former. Several factors like unusual climatic conditions, inadequate surveillance, unsatisfactory laboratory services and inadequate indoor residual insecticide spray were instrumental for the outbreak.

Adolescent↗
PubMed1998

Investigation on malaria vectors and mosquito fauna in south Tripura district, Tripura state.

In an entomological study in South Tripura district of Tripura state during June 1998, a total of 31 species of mosquitoes belonging to eight genera were recorded. Among the known malaria vectors in India, Anopheles annularis, An. jeyporiensis, An. minimus, An. philippinensis/nivipes and An. varuna were collected but none of them could be incriminated. During the survey, Aedes pallidostriatus and Malaya genurostris were recorded for the first time in the north-eastern region and Tripura state respectively. Presence of host seeking An. minimus in light-trap collections indoors and its absence during morning indoor resting collections indicated the probability of some degree of exophilic behaviour of An. minimus population in Tripura.

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PubMed1998

Epidemiological importance of younger age group during malaria epidemic in PHC Tamulpur, Assam.

An investigation of a malaria epidemic was carried out in Tamulpur Primary Health Centre, district Nalbari, Assam during April 1995. The analysis revealed that children between 3 and 12 years of age who were treated and who recovered clinically from fever during the epidemic were instrumental in the progression of the epidemic by acting as Plasmodium falciparum gametocyte reservoirs. Special efforts are required for treatment of children below 12 years during an epidemic.

Age Distribution↗
PubMed1997

Seasonal prevalence of Anopheles dirus and malaria transmission in a forest fringed village of Assam, India.

Seasonal abundance of Anopheles dirus (s.l.) and malaria prevalence in an isolated forest fringed village was monitored at monthly intervals during August 1995 to July 1996. An. dirus was the only vector species detected during the study period. Its density pattern showed distinct seasonality with the peak occurring in the month of July and very low number during cool dry months. Positive correlation (r = 0.721) was found between the density of An. dirus and the amount of rainfall occurring two weeks prior to the collections. Overall sporozoite rate of 1.6% and parous rate of 64.7% were found in the study. Malaria transmission closely followed the density pattern of An. dirus and was seasonal with slide positivity rate and P. falciparum percentage of 47 and 83% respectively. Mean malaria prevalence was higher (p < 0.05) in females.

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