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S K Subbarao

Publications and source records attributed to S K Subbarao.

At least 55 records · Page 3Linked to original sources
PubMed1991

Genetic markers in refractory and susceptible malaria patients in village Bhanera, Distt. Ghaziabad, U.P.

Malaria 'susceptible' and 'refractory' subjects from village Bhanera in District Ghaziabad (Uttar Pradesh) were examined for various genetic markers, viz., ABO, haptoglobin, haemoglobin and glucose-6-phosphate dehydrogenase polymorphism. One hundred and nine susceptible and 36 refractory subjects were studied. No significant differences with respect to distribution patterns of the genetic markers were observed in the two groups except for AB blood group. In general, a high incidence of ahaptoglobinaemia was observed in this population and incidence increased with the increase in malaria attacks, suggesting that repeated malaria attacks cause ahaptoglobinaemia.

ABO Blood-Group System↗
PubMed1991

Resistance in Anopheles culicifacies sibling species B and C to malathion in Andhra Pradesh and Gujarat States, India.

Studies conducted in Warangal, Khammam and Mahabubnagar districts in Andhra Pradesh and Surat district in Gujarat have revealed that Anopheles culicifacies sensu lato (s.l.) populations were resistant to malathion. In the absence of indoor spraying of malathion in public health programs in the 3 districts of Andhra Pradesh, resistance is attributed to the extensive use of pesticides in agriculture. Species B and C were sympatric in all areas surveyed, and both the species were resistant to malathion. In most of the surveys carried out in Mahabubnagar, Khammam and Warangal, levels of resistance were higher in species C than in B. In Mahabubnagar district an increase in resistance from 5.5 to 64% was observed from 1985 to 1987 in An. culicifacies s.l. The proportion of species C was low in the initial 2 surveys, and in the later surveys the proportion was almost equal to that of species B; the resistance level was also significantly higher than in species B. In Surat district, where resistance ranged from 74 to 93%, the level of resistance in the 2 species was almost the same.

Animals↗
PubMed1990

Genetics of golden-yellow larva in Anopheles stephensi.

Two larval body color mutants, golden-yellow larva (gy) and Black larva (Bl) were isolated from laboratory strains of Anopheles stephensi. The inheritance pattern revealed that golden-yellow larva was an autosomal recessive and Black larva an autosomal semi-dominant mutant. Both of these mutants were found to be linked with a map distance of 3.75 +/- 0.42 and have been placed in linkage group III.

Animals↗
PubMed1988

Susceptibility of Anopheles culicifacies species A and B to Plasmodium vivax and Plasmodium falciparum as determined by immunoradiometric assay.

We have used a two-site immunoradiometric assay and species-specific antisporozoite monoclonal antibodies to determine the relative roles that sibling species A and B of the Anopheles culicifacies complex play in malaria transmission in western Uttar Pradesh, India. The results unequivocally establish species A as the primary vector of both Plasmodium vivax and P. falciparum in this area. Our results indicate active transmission of P. vivax from May to October and of P. falciparum from August to December. The identification of species A as the primary malaria vector in northern India will now allow suitable malaria control strategies to be designed.

Animals↗
PubMed1988

The Anopheles culicifacies complex and control of malaria.

Of the 50 or so species and varieties of anopheline mosquito in India, about 20 are implicated as vectors of human malaria. Of these, perhaps the most important and widespread is Anopheles culicifacies s.l. For the first 10 years of widespread DDT spraying, An. culicifacies remained susceptible to this insecticide - indeed, some thought it lacked resistance genes altogether. By 1960 however, resistance to DDT was apparent. DDT is a cheap insecticide, and its use is still favoured for mosquito control wherever it remains effective. But by the end of the late 1970s it appeared that DDT resistance in An. culicifacies (and other species) was a major barrier to effective vector control in several areas - particularly in parts of the northwestern states. Yet in other areas DDT still seemed to be effective. There was also increasing evidence from other studies suggesting differences in An. culicifacies found in different areas - particularly differences in seasonal prevalence and man-biting activity. We now know - as Sarala Subbarao discusses here - that An. culicifacies s.l. represents a complex of at least four sibling species. But in this case, one of the most important findings is that DDT resistance is mainly associated with species B which proves to be a very poor vector of malaria. Such findings, made possible by careful cytogenetic studies, have very important consequences for malaria epidemiology and control policies.

Journal Article↗
PubMed1988

Responses of Anopheles culicifacies sibling species A and B to DDT and HCH in India: implications in malaria control.

Differential responses of Anopheles culicifacies Giles sibling species A and B to DDT were evident from higher survival rate of species B in laboratory bioassays and greater proportions of species B in DDT-sprayed villages of northern India, compared with those under HCH pressure. Both species A and B have become almost completely resistant to HCH in this area due to regular house-spraying with HCH for about the last 10 years. Because species A predominates in northern India, where it has been incriminated as an important vector of malaria, and species A is more susceptible than species B to DDT, it is suggested that DDT would control malaria transmission more effectively than HCH in this situation. Monitoring of insecticide resistance in species A is therefore recommended as the basis for future choice of insecticides to be used by the National Malaria Eradication Programme.

Aerosols↗
PubMed1988

Anopheles culicifacies: siblings species composition and its relationship to malaria incidence.

Entomological and epidemiological surveys in May, August and November 1985 and March 1986 were conducted in villages in Bulandshahr, a western district in Uttar Pradesh and in three eastern districts, Jaunpur, Ballia and Saran. In Bulandshahr, Anopheles culicifacies sibling species A and B were found, with a predominance of species A. Both Plasmodium vivax and P. falciparum were present and the malaria incidence remained high (SPR, 6-50%) indicating an active transmission. In contrast, in three eastern districts predominance of species B with an occasional occurrence of species A was observed. Malaria cases were almost absent in Ballia and Saran and in Jaunpur 10.3% slide positivity rate was observed in May but in later surveys cases were considerably lower (SPR, 0.5-2.9%) indicating the absence of indigenous transmission. In the eastern districts, malaria parasites are regularly brought in from endemic areas by the migrant labor population. Although An. culicifacies s.l. occurs in both the areas, the difference in malaria incidence appears to be due to the difference in the composition of the sibling species which is, the predominant presence of species A in the western district and its absence in eastern districts. This indicates that species A is responsible for active malaria transmission while species B is not.

Animals↗
PubMed1988

Host feeding patterns of Anopheles culicifacies species A and B.

Countercurrent immunoelectrophoresis was used to assay bloodmeals to determine the host specificity of Anopheles culicifacies species A and B, collected from areas in Delhi, Uttar Pradesh and Bihar. Results indicated the predominantly zoophagic nature of species A and B with a relatively higher degree of anthropophagy for species A. Further, the human blood index was found to be related to the proportion of human and cattle population in an area. This study is significant because, of the two species only species A was incriminated as the vector of malaria in these areas.

Animals↗
PubMed1987

Egg-float ridge number in Anopheles stephensi: ecological variation and genetic analysis.

Eight Indian laboratory stocks of Anopheles stephensi Liston could be grouped into three categories with, respectively, 14-22, 12-17 and 9-15 ridges on the egg-floats. The mode number of ridges among the eggs laid by individual females in these stocks was 16-19, 13-16 and 10-14, respectively. The category with the highest egg-float ridge number corresponded with the type-form and the lowest with var. mysorensis Sweet and Rao; the new egg-float category with ridge number modes of thirteen to sixteen was designated as 'intermediate'. All three forms, i.e. type-form, intermediate and myosorensis were observed in semi-urban areas while only intermediate and mysorensis were seen in rural areas. Breeding experiments indicated no post-copulatory barriers between the populations. Likelihood analysis of the results of crosses and back crosses indicated that variation in ridge number is controlled by more than one genetic factor. The stocks with different ridge numbers are best considered as 'ecological variants'.

Animals↗
PubMed1984

Genetics of three esterase loci in Anopheles stephensi Liston.

A survey of laboratory strains of Anopheles stephensi for nonspecific esterases by polyacrylamide gel electrophoresis revealed 10 zones of esterase activity. In 3 of the 10 zones, three electromorphs were observed. Genetic analysis revealed that these three zones are controlled by three loci, viz., Est-3, Est-4, and Est-5, and that the electromorphs are codominant alleles at each locus. The three esterase loci were found linked to each other and to an autosomal marker colorless-eye. The esterase loci have tentatively been placed in linkage group II. The probable gene sequence on chromosome 2 is either c-Est-3-Est-4-Est-5 or c-Est-4-Est-3-Est-5.

Animals↗