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S K Subbarao

Publications and source records attributed to S K Subbarao.

At least 37 records · Page 2Linked to original sources
PubMed2000

Cytotaxonomic evidence for the presence of Anopheles nivipes in India.

Anopheles philippinensis mosquitoes were collected from 5 states in India: Assam, Meghalaya, Arunachal Pradesh, Manipur, and Nagaland. Half-gravid females were examined for variations in wing venation using the presector dark mark on vein I and polytene chromosomes derived from ovarian nurse cells. Polytene chromosomes were examined for diagnostic inversions, t on chromosome arm 2 and I on arm 5. Based on wing characteristics, both An. philippinensis and An. nivipes were identified. Polytene chromosome examinations revealed that all specimens from these 2 populations had 2t; 51 inversion genotype, a diagnostic character for An. nivipes. The wing character was not diagnostic; therefore, it was concluded that all the specimens examined were actually An. nivipes and not An. philippinensis. Further, the X chromosome was of x+b type, that is, the standard arrangement with reference to the inversion b, reported in the An. nivipes population in Thailand. This is the 1st report that unequivocally establishes the occurrence of An. nivipes in India and also shows that the adult wing character is not reliable in distinguishing An. philippinensis from An. nivipes, as has been observed in Thailand.

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PubMed2000

Studies on Anopheles fluviatilis and Anopheles culicifacies sibling species in relation to malaria in forested hilly and deforested riverine ecosystems in northern Orissa, India.

In a malaria-endemic region in northwestern Orissa, India, a longitudinal study was undertaken to delineate information on the sibling species of Anopheles fluviatilis and Anopheles culicifacies and their bionomics and role in malaria transmission in forested and deforested ecosystems. In forested villages, An. fluviatilis sibling species S (97.97%) and T (2.02%) were present. The former was highly anthropophagic (human blood index 0.88). Among the sibling species of An. culicifacies, species B (27.96%), C (71.1%), and B/C heterozygotes (0.94%) were present and were highly zoophagic. In deforested riverine villages An. fluviatilis was nearly absent and An. culicifacies sibling species A (0.48%), B (21.1%), C (77.94%), and B/C heterozygotes (0.48%) were present. In forested villages, the annual parasite incidence (269 cases/1,000) and the slide positivity rate (45%) were significantly higher than those in deforested areas, which had values of 39 cases/1,000 and 27%, respectively. The study showed that the high endemicity of malaria in the forested villages was due primarily to 2 vectors, the high rate of anthropophagy of An. fluviatilis species S, and also the more favorable ecological conditions for this vector.

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PubMed2000

Investigation of malaria prevalence at National Thermal Power Corporation, Shaktinagar, Sonbhadra District (Uttar Pradesh), India.

Malaria in industrial complexes is promoted by extensive mosquitogenic potential generated by excavations and importation of parasite through migratory labor. The National Thermal Power Corporation (NTPC), Shaktinagar, Sonbhadra district was surveyed for malariogenic conditions from 1994 to 1996. The major mosquito breeding sites were drains, storm-water drains, lakes, outside tanks, overhead tanks, sluice-valve chambers, ornamental tanks, wells, pit wells and water reservoirs, etc. Anopheles culicifacies was the major vector of malaria in this area. Sibling species identification of An. culicifacies revealed that species C predominated during the transmission season and responsible to transmit malaria. Insecticide susceptibility tests against An. culicifacies sl showed that An.culicifacies population was 100% susceptible to malathion, fenitrothorn and deltamethrin while it was found 44% resistant to DDT. The malaria cases recorded in 1994, 1995 and 1996 were 847, 590 and 409 respectively. In vitro study on P. falciparum cases showed that 41, 70, 50% of the isolates tested were resistant to chloroquine in 1994, 1995 and 1996 respectively while an in vivo follow-up study showed 20-30% P. falciparum cases resistant to chloroquine. An integrated approach involving alternate vector control measures along with judicious use of insecticides has been suggested to bring down malaria in industrial complexes.

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PubMed1999

Evidence for a new malaria vector species, species E, within the Anopheles culicifacies complex (Diptera: Culicidae).

Female Anopheles culicifacies Giles from Ramanathapuram district, Tamil Nadu state, India, were examined for oocysts and sporozoites and their larval progeny for mitotic karyotype. Collections were made from Mandapam and Uchipuli on the mainland, and Thangachimadam and Pamban on Rameshwaram Island. Of the 451 An. culicifacies females that were collected and dissected, 24 were found positive for Plasmodia (21 for sporozoites and 3 for oocysts). Both acrocentric and submetacentric Y-chromosome karyotypes were observed among the progeny of females from all villages. All 11 iso-female lines whose parental females were positive for sporozoites or oocysts had progeny with submetacentric Y-chromosomes. Total absence of sporozoite-positives among mothers of acrocentric males was evidence of assortative mating between these 2 sympatric populations (i.e., 2 species). We propose that the nonvector population with acrocentric Y-chromosome sons retain the original designation of species B and that the vector population with the submetacentric Y-chromosome sons be designated as species E, a new species.

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PubMed1998

Studies on bionomics of Anopheles fluviatilis and its sibling species in Nainital district, U.P.

A study on the bionomics of Anopheles fluviatilis sensu lato was carried out in two physiographic regions, viz. Bhabar and Terai of District Nainital, Uttar Pradesh. In both areas, An. fluviatilis was found resting indoors predominantly in cattlesheds. Cytological examination of An. fluviatilis revealed that species T and U were sympatric in Bhabar and Terai villages with predominance of species T. These two sibling species appear to be poor vectors of malaria.

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PubMed1998

Stage-specific effects of antimalarials on an Indian isolate of Plasmodium falciparum.

In this study, effects of timed sequential exposure to various concentrations of chloroquine and its two metabolites (SA100387/050 B, SA 100487/053 B), quinine, hydroquinine and quinidine were monitored by morphological analyses, using synchronous cultures of Plasmodium falciparum. The trophozoites and schizonts were sensitive to chloroquine and its metabolites. However, quinine and two of its derivatives were lethal without particularly being stage-specific.

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PubMed1997

Anopheline species complexes & malaria control.

Species complexes comprising morphologically indistinguishable biological species that are reproductively isolated, are of common occurrence among anophelines. A list of anopheline species complexes identified so far in the world has been given. To demonstrate the importance of species complexes in malaria control, we report the Anopheles culicifacies complex as a case study. An. culicifacies is a major vector of malaria in India and neighbouring countries. This complex comprises four sibling species, A, B, C and D. Stratification of U.P. state and district Allahabad has been shown taking into consideration the biological differences among sibling species, viz., sibling species composition and vectorial potential- species B is a non-vector while others are vectors. To achieve cost effective vector control, microlevel stratification at least at the block level has been suggested. Implications of differential responses of sibling species to DDT and malathion in field operations have been discussed. To achieve selective and sustainable control, and to reduce the unnecessary selection pressure of insecticides, an insecticide spray strategy to control An. culicifacies has been provided.

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PubMed1996

Anopheles fluviatilis complex: host feeding patterns of species S, T, and U.

The host feeding specificity of Anopheles fluviatilis sibling species S, T, and U was determined by analyzing blood meal source using countercurrent immunoelectrophoresis. A distinct difference in the feeding patterns was observed among these species. Species S was found to be predominantly anthropophagic with 91% of the population having fed on human blood. In contrast, species T and U were either exclusively or primarily zoophagic.

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PubMed1994

Lactate dehydrogenase allozyme differentiation of species in the Anopheles culicifacies complex.

Genetically controlled enzyme variation exists within and between four sibling species of the Anopheles culicifacies complex of malaria vectors in India. A study on electrophoretic variation of nine enzymes in An. culicifacies sibling species revealed that the lactate dehydrogenase (Ldh) locus has Fast (F) and Slow (S) allozymes distinguishing species A+D from species B+C with a probability of c. 95%.

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PubMed1994

Correlation of malaria endemicity with An. culicifacies sibling species composition and malaria antibody profile in district Allahabad (U.P.).

Entomological, parasitological and serological surveys were conducted between October 1989 and November 1990 in 27 villages (population 33,250) belonging to three topographically different areas of district Allahabad, viz. Gangapar, Doaba and Yamunapar. A good correlation existed in all the three areas between malaria incidence vis-a-vis An. culicifacies sibling species composition and malaria antibodies titre in the populations. In Gangapar and Doaba villages, An. culicifacies densities were low and the proportions of vector species A and C were much less than that of species B, the non-vector species. Low endemicity of malaria was supported by low antibody titres observed in the population. In contrast, in Yamunapar villages An. culicifacies densities were high, species A and C together were almost equal to species B, and malaria incidence as well as antibody titre were high. Based on these observations, district Allahabad, Uttar Pradesh, could be divided into two zones, low malaria transmission zone--Gangapar and Doaba areas and high malaria transmission zone--Yamunapar area.

Adolescent↗
PubMed1994

Two-site immunoradiometric assay (IRMA): detection, efficiency, and procedural modifications.

A 2-site immunoradiometric assay (IRMA) has been done using Anopheles stephensi fed on Plasmodium vivax blood through parafilm to ascertain at what time in the sporogonic cycle circumsporozoite (CS) antigen can be detected, and to detect CS antigen in mosquitoes squashed on filter paper (FP) and cellulose acetate membrane (CAM). The CS antigen was detectable only in mature oocysts, a day prior to sporozoite liberation, and in salivary gland sporozoites. Dissected sporozoites adsorbed on FP/CAM also can be analyzed by IRMA for Plasmodium species identification.

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PubMed1993

Role of An. culicifacies and An. stephensi in malaria transmission in urban Delhi.

Studies on adult densities, vector incrimination and breeding habitats of An. culicifacies and An. stephensi were carried out during June 1984 to May 1986 in three different ecological areas of urban Delhi. Both An. culicifacies and An. stephensi prevailed throughout the year in peri-urban areas with higher densities during the post-monsoon months. In south and northwest areas, low densities of these vector species were recorded. An. culicifacies was found naturally infected with sporozoites in peri-urban and south areas, whereas An. stephensi showed gland infection in south areas only. Out of 827 blood smears collected, 302 were positive for malaria parasites. Of the positives, P. vivax formed 48.3% and P. falciparum 51.7%. Peri-urban areas showed a higher number of malaria cases than south and northwest areas.

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PubMed1993

Inheritance and linkage of malic enzyme in Anopheles stephensi.

Genetics and linkage analysis of malic enzyme (Me) have been worked out in Anopheles stephensi. Genetic analysis revealed the 2 variants to be codominant alleles at a locus Me, which is sex-linked. Linkage studies with another X-linked mutant red-eye (r), indicated that the map distance between 2 loci was 44.60 +/- 1.07.

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PubMed1993

Role of Anopheles culicifacies s.l. and An. pulcherrimus in malaria transmission in Ghassreghand (Baluchistan), Iran.

A 2-site immunoradiometric assay (IRMA) was performed on the head and thorax of Anopheles culicifacies s.l. and An. pulcherrimus females, the 2 most common anopheline species in the District of Ghassreghand (Baluchistan, Iran), collected during the 2 peak malaria transmission seasons (May and September-October 1991). Positive IRMA results revealed the 2 species as potential vectors of malaria in this highly endemic district. This finding serves as the first report on natural infection of An. pulcherrimus in Iran and is the second on natural infection of An. culicifacies since the previous report of 1959.

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PubMed1993

Anopheles culicifacies complex: cytogenetic characterization of Rameshwaram island populations.

Anopheles culicifacies sensu lato collected from Rameshwaram island, Tamil Nadu state, India was identified as species B based on the diagnostic inversion karyotype Xab 2g1+h1 as observed in polytene chromosomes. Among male mitotic karyotypes made from larval neurogonial cells, two types were observed: one with an acrocentric Y-chromosome and the other with a sub-metacentric Y-chromosome, both had sub-metacentric X and metacentric autosomes. The Rameshwaram population is identical to species B in its genetic relationship with species A and C as determined by experimental hybridizations (sterile and fertile male hybrids, respectively).

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PubMed1992

Assignment of 6-phosphogluconate dehydrogenase and malate dehydrogenase to chromosome 3 of Anopheles stephensi.

Genetics and linkage analysis of 6-phosphogluconate dehydrogenase (6-PGD) and malate dehydrogenase (MDH) have been investigated in Anopheles stephensi. Both these markers were found to be autosomal and linked and have been assigned to linkage group III. Two mutant markers, Black larva (Bl) and golden-yellow larva (gy), were used to establish the map distances, and the current sequence of loci on chromosome 3 is as follows: Bl (3.75)-gy (14.53)-Mdh-2 (49.83)-6-pgd.

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PubMed1992

Differential selection of malathion resistance in Anopheles culicifacies A and B (Diptera: Culicidae) in Haryana State, India.

In November 1989, for the first time after the introduction of malathion spray in 1982, increased densities of Anopheles culicifacies Giles s.l. were observed in Chhatera and Barota, two villages in Halalpur block in Sonepat District, Haryana State, India. In bioassay tests against the diagnostic dose of malathion (5% for 1 h), 41-47% of mosquitoes survived. An culicifacies populations in this area comprise two sibling species, A and B. Differential malathion resistance was observed; in species A it was 2-9% and in species B 62-66%. Likewise, species A was found to be more susceptible to DDT than was species B. The possible use of DDT spray to delay the onset of malathion resistance is discussed.

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