On the conspecificity ofAnopheles fluviatilis species S withAnopheles minimus species C

Anopheles fluviatilis and An. minimus complexes,each comprising of at least three sibling species, are closely related and important malaria vectors in Oriental Region. Recently An. fluviatilis species S, which is a highly efficient malaria vector in India, has been made conspecific with An. minimus species C (senior synonym) on the basis of homology in 335 base pair nucleotide sequence of D3 domain of 28S ribosomal DNA (rDNA). We examined the conspecificity of these two nominal species by obtaining and analysing the DNA sequences of nuclear ribosomal loci internal transcribed spacer 2 (ITS2) and D2-D3 domain of 28S rDNA (28S-D2/D3) from those of An. fluviatilis S and An. minimus C. We found that the sequences of An. fluviatilis S are appreciably different from those of An. minimus C with pair-wise distance (Kimura-2-parametre model)of 3.6 and 0.7%for loci ITS2 and 28S-D2/D3, respectively. Pair-wise distance and phylogenetic analyses using ITS2 sequences of members of Minimus and Fluviatilis Complexes revealed that An. fluviatilis S is distantly related to An. minimus C as compared to any other members of the Fluviatilis Complex. These findings suggest that the two nominal species, An. fluviatilis S and An. minimus C, do not merit synonymy. The study also confirms that the reported species An. fluviatilis X is synonym with species S.

Efficacy of Agnique MMF monomolecular surface film against Anopheles stephensi breeding in urban habitats in India

Efficacy of Agnique MMF, a monomolecular film formulation, was tested against immatures of Anopheles stephensi, an urban malaria vector in India, in simulated and natural habitats. Simulated field trials carried out in cement tanks showed 100% inhibition of adult emergence for up to 1 wk at 0.4 ml/m2 and up to 3 wk at 1 ml/m2. A small-scale field trial in tanks and wells at 1 and 2 ml/m2 produced more than 75% reduction of late instars and 100% reduction of pupae on day 1. The reduction in pupae at 1 and 2 ml/m2 lasted up to 2 wk in tanks and 5 wk in wells. These results suggest that Agnique MMF could be used as one of the choices in an urban malaria control program.

Village-scale evaluation of mosquito nets treated with a tablet formulation of deltamethrin against malaria vectors

A field trial was carried out in the Sundargarh district of Orissa, India on the efficacy of mosquito nets treated with a tablet formulation of deltamethrin (K-O TAB) against malaria vectors. Treated nets were used in one village, and in the two control villages, one used untreated nets and the other used indoor spraying with DDT, without nets. In this area the primary malaria vectors are Anopheles culicifacies Giles sensu lato (Diptera: Culicidae) and An. fluviatilis James s.l., which are both endophagic and endophilic, and fully susceptible to deltamethrin. Treatment of a 10-m(2) mosquito net with one of the tablets gave a deltamethrin deposit of 25 mg/m(2). Bioassays repeated on domestically used nets over 7 months showed persistence of almost 100% mortality of An. fluviatilis, whereas An. culicifacies showed a decline from 100% to 71% mortality over this period, after which the nets were re-treated and bioassays were not continued. The sum of collections of mosquitoes resting in village houses and those in exit traps and dead on floor sheets showed a reduction in the numbers of the two vector species due to the treated nets, compared with untreated or no nets, but no reduction in other anophelines or Culex species. Large proportions of the collections of the vector and non-vector anophelines were dead on the floor sheets, but among Culex, mortality was delayed. Treated and untreated nets reduced the proportion of anophelines that had blood-fed; the treated nets did so more effectively than the untreated in the case of An. culicifacies and of Culex mosquitoes. In rooms with treated nets a larger proportion of the total collections [dead + live] were in the exit traps, which can be attributed to the excito-repellent effect of deltamethrin. It is easier to pack and handle tablets of insecticide than liquid concentrate and the use of one tablet per net may be preferable to making up a large volume of diluted insecticide and dipping many nets at a time.

Larvivorous fish in wells target the malaria vector sibling species of the Anopheles culicifacies complex in villages in Karnataka, India

Malaria was a major problem in a sericulture area of Karnataka, south India, where Anopheles culicifacies s.l. and A. fluviatilis s.l. were considered to be the main vectors. Sibling species complexes of these two species were analysed in three ecologically different villages. Among A. culicifacies, only sibling species A and B were found. In Puram, a village with 22 wells, species A predominated; species B predominated in a village with four wells and a stream, and in a village with a stream and no wells. Poecilia reticulata fish were introduced into all wells and streams in the villages, and after one year no vectors were found in Puram, and all, or nearly all, A. culicifacies were species B in the other two villages. All A. fluviatilis belonged to the sibling species T. Blood meal analysis indicated that a few of the A. culicifacies collected had fed on humans while all the A. fluviatilis had fed on bovines. Before the introduction of fish, the annual parasite incidence for malaria was high in Puram, but much lower in the other two villages. From 1998 (over one year after release of fish) until 2003, no malaria cases were detected in the three villages.

An allele-specific polymerase chain reaction assay for the differentiation of members of the Anopheles culicifacies complex

Anopheles culicifacies, the principal vector of malaria in India, is a complex of five cryptic species which are morphologically indistinguishable at any stage of life. In view of the practical difficulties associated with classical cytotaxonomic method for the identification of members of the complex, an allele-specific polymerase chain reaction (ASPCR) assay targeted to the D3 domain of 28S ribosomal DNA was developed. The assay discriminates An. culicifacies species A and D from species B, C and E. The assay was validated using chromosomally identified specimens of An. culicifacies from different geographical regions of India representing different sympatric associations. The assay correctly differentiates species A and D from species B, C and E. The possible use of this diagnostic assay in disease vector control programmes is discussed.

Evaluation of bifenthrin treated mosquito nets against anopheline and culicine mosquitoes

BACKGROUND AND OBJECTIVES

The main rural malaria vector Anopheles culicifacies has developed resistance to dichloro diphenyl trichloroethane (DDT), hexachloro cyclo hexane (HCH) and malathion in the state of Haryana in northern India. An alternative synthetic pyrethroid insecticide bifenthrin was therefore evaluated on mosquito nets against anopheline and culicine mosquitoes, in two villages Jagdishpur and Garh Mirakpur of Community Health Center (CHC) Badhkhalsa in district Sonipat, Haryana state.

METHODS

Two formulations of bifenthrin, suspension concentrate (SC) and micro-emulsion (ME) were compared with micro-capsule suspension (CS) of lambdacyhalothrin. The impact of three doses of bifenthrin (10, 25 and 50 mg/m(2)) impregnated on mosquito nets was compared with lambdacyhalothrin (25 mg/m(2)) and untreated control. Quality assessment of treatment on treated nets was carried out by residue analysis and the persistence of the insecticide on nets was determined by contact bioassays. Efficacy of treated nets on mosquito density was assessed by calculating mosquito entry rate, immediate mortality, delayed mortality and excito-repellency to the insecticides.

RESULTS

In susceptibility tests An. culicifacies was susceptible to bifenthrin (0.1% test papers) and to lambdacyhalothrin (0.05% test papers). Bioassays on treated nets against A. culicifacies recorded 100 per cent mortality up to tenth fortnight for all the doses of impregnation with bifenthrin (SC and ME) and lambdacyhalothrin (CS). Ring-net bioassays against An. culicifacies showed median knock-down time between 3.1 to 11.4 min. Behavioural indices were also studied for anopheline and culicine mosquitoes. The reduction in entry rates of anopheline and culicine mosquitoes into the rooms with treated nets compared to control indicated good efficacy with all the formulations and doses of the insecticides. INTERPRETAION AND CONCLUSION: Indoor (immediate) mortality of mosquitoes with bifenthrin ME formulation was relatively lower compared to SC fomulation of bifenthrin and based on delayed mortility and continued susceptibility in bioassays, bifenthrin ME at the rate of 10 mg/m(2) dose was found suitable for the impregnation of mosquito nets for phase III trial.

Anti-malarial activity of some xanthones isolated from the roots of Andrographis paniculata

Four xanthones were isolated from the roots of Andrographis paniculata using a combination of column and thin-layer chromatographic methods. They were characterized as (i) 1,8-di-hydroxy-3,7-dimethoxy-xanthone, (ii) 4,8-dihydroxy-2,7-dimethoxy-xanthone, (iii) 1,2-dihydroxy-6,8-dimethoxy-xanthone and (iv) 3,7,8-trimethoxy-1-hydroxy xanthone by IR, MS and NMR spectroscopic methods. In vitro study revealed that compound 1,2-dihydroxy-6,8-dimethoxy-xanthone possessed substantial anti-plasmodial activity against Plasmodium falciparum with its IC(50) value of 4 microg ml(-1). Xanthones bearing hydroxyl group at 2 position demonstrated most potent activity while xanthones with hydroxyl group at 1,4 or 8 position possessed very low activity. In vivo anti-malarial sensitivity test of this compound on Swiss Albino mice with Plasmodium berghei infection using Peters' 4-day test gave substantial reduction (62%) in parasitaemia after treating the mice with 30 mg kg(-1) dose. In vitro cytotoxicity against mammalian cells revealed that 1,2-dihydroxy-6,8-dimethoxy-xanthone is non-cytotoxic with its IC(50) > 32 microg ml(-1).

Malarial morbidity in tribal communities living in the forest and plain ecotypes of Orissa, India

A detailed epidemiological study of malarial morbidity was carried out in 13 'tribal' villages in the forest or plain ecotypes of Sundargarh district, Orissa, India. Longitudinal and cross-sectional, parasitological surveys were conducted in all the villages, to determine the incidence of malaria and the prevalence of malarial infection. The annual numbers of malaria cases/1000 were much higher in the forest (347.9) than on the plain (61.0). In the forest clinical malaria occurred more frequently in children than in adults but on the plain all age-groups were equally affected. In cross-sectional surveys, 14.1% of the subjects from the forest but only 2.8% of those from the plain were found smear-positive for malarial infection. The prevalences of infection in the forest area were highest in the young children (aged 1-5 years) and gradually declined with increasing age. The highest incidence of Plasmodium falciparum malaria (0.90 episode/person-year) was also recorded in the subjects from the forest who were aged 1-5 years. In the forest and plain communities surveyed, 78.5%-81.5% and 36.0%-52.0% of the children aged 2-9 years had detectable splenomegaly, respectively, indicating that the forest was hyper-endemic and the plain meso-endemic for malaria. Malaria is clearly a major problem among the tribal communities of Sundargarh, causing great morbidity and, consequently, considerable economic losses.

Liquid chromatographic determination of amodiaquine in human plasma

A normal-phase high-performance liquid chromatographic method using dichloromethane- methanol-1M perchloric acid (100:10:0.9, v/v/v) at a flow rate of 1.0 ml min(-1) on a LiChrospher Si column with UV (254 nm) detection has been developed for the determination of amodiaquine and its metabolites desethyl amodiaquine and bisdesethyl amodiaquine in plasma. The limit of quantification was 5 ng ml(-1). Mean within-day and day-to-day coefficients of variation (CV) were 4.10 and 6.27% for amodiaquine, 3.43 and 4.80% for desethyl amodiaquine and 3.53 and 5.23% for bisdesethyl amodiaquine, respectively. Mean extraction recovery of amodiaquine, desethyl amodiaquine and bisdesethyl amodiaquine from plasma were 82.48, 74.50 and 69.65%, respectively. Chloroquine and its metabolite desethyl chloroquine, quinine, sulfadoxine and primaquine do not interfere in the detection of amodiaquine, desethyl amodiaquine and bisdesethyl amodiaquine in plasma.

Widespread occurrence of the Plasmodium falciparum chloroquine resistance transporter (Pfcrt) gene haplotype SVMNT in P. falciparum malaria in India

The Plasmodium falciparum chloroquine resistance transporter (Pfcrt) K76T mutation and haplotype (amino acids 72-76) and the P. falciparum multidrug resistance 1 (Pfmdr1) mutation (N86Y) were analyzed as markers of chloroquine resistance in the DNAs of 73 blood samples from patients with P. falciparum malaria in India. Seventy of the 73 DNAs had the Pfcrt K76T mutation. Of these, 66 had the SVMNT haplotype and four had CVIET, the African/Southeast Asian haplotype. Only 20 of 69 DNAs had the Pfmdr1 N86Y mutation. It is surprising that the Pfcrt haplotype in India is predominantly SVMNT, rather than that seen in Southeast Asia. The widespread prevalence of the Pfcrt K76T mutation is a cause for concern.

Multi-drug resistant Plasmodium falciparum malaria in Assam, India: timing of recurrence and anti-malarial drug concentrations in whole blood

The susceptibility of 23 cases of Plasmodium falciparum malaria from the Sonapur primary health center in the Kamrup district of Assam, India to different antimalarials was investigated using the 28-day World Health Organization in vivo test. Whole blood concentrations of chloroquine, sulfadoxine, and quinine were determined at different intervals and at the time of parasites recrudescence after completion of treatment with the respective drugs to confirm the status of drug sensitivity. A case of multi-drug resistant P. falciparum malaria was found where recrudescence occurred, despite standard oral treatment with chloroquine, sulfadoxine/pyrimethamine, and quinine sequentially. Whole blood concentrations of chloroquine, sulfadoxine, and quinine at the time of recrudescence were 0.35 microg/ml (day 7), 18 microg/ml (day 14), and 0.009 microg/ml (day 14), respectively. Therefore, monitoring of drug-resistant P. falciparum malaria and its proper treatment should be intensified to check the spread of multi-drug resistant strains in other parts of the country.

Spiracular indices in Anopheles stephensi: a taxonomic tool to identify ecological variants

Thoracic spiracle length and its index was examined for their ability to discriminate two ecological variants, type form and mysorensis, of Anopheles stephensi in the adult stage. The type form is exclusively domestic in all seasons, whereas the mysorensis variant occupies the outdoor niche during monsoon and postmonsoon seasons, with spillover into domestic sites during summer ecological stress periods. A statistically significant co-relation was established between the ridge count of the egg and two adult measurements, the thoracic spiracle length, and the spiracular index. In An. stephensi type form, average spiracle length was 0.11-0.12 mm and average spiracular index was 8.09-9.23, whereas in mysorensis, the corresponding figures were 0.09-0.10 mm and 6.82-7.60. These parameters showed consistent variations in population of mosquitoes that emerged during monsoon and summer season. The thoracic lengths in both variants remained constant, and only spiracular lengths showed fluctuations in three seasonal populations. These measures provide discrimination of adult variants--identifications that are essential in malaria control programs.

GIS based malaria information management system for urban malaria scheme in India

A GIS based information management system has been developed to help Urban Malaria Control in India. The basic objective is to develop a model to assist planning and implementation of a suitable control measure. The system can help in: (i) identifying high receptive areas in time and space domain; (ii) identifying risk factors for high receptivity; (iii) monitoring and evaluating control measures. To demonstrate this system, information on 33 parameters and malaria cases has been attached to a digitised map of Dindigul, an urban town in Tamil Nadu. Functionalities of the system and its utility are described in this paper. A GIS based information management system ensures that if a localised spurt of the disease occurs, it can be associated rapidly with a likely cause, a specific vector, and a probable human source, so that appropriate preventive action can be taken to arrest any rising trend.

The hospital- and field-based performances of the OptiMAL test, for malaria diagnosis and treatment monitoring in central India

The performance of the OptiMAL test, to detect and differentiate Plasmodium falciparum and P. vivax, was evaluated in central India. The subjects were either symptomatic patients, who presented at a referral hospital in urban Jabalpur, or the inhabitants of remote, tribal, forested villages where malaria is a major public-health problem. In each setting, the results of conventional microscopy were used as the 'gold standard'. Under hospital conditions, the test had excellent sensitivity (100%), good specificity (97%), a high positive predictive value (98%) and a high negative predictive value (100%). The corresponding values in the field-based study in the tribal villages (100%, 67%, 84% and 100%, respectively) were almost as good. The results of OptiMAL testing reveal the decline in parasitaemias (of P. falciparum or P. vivax) after drug administration. For monitoring the effectiveness of treatment, the test could therefore be a useful alternative to microscopy, particularly (1) in places where the facilities for microscopy are poor or non-existent and (2) among hospitalized patients with severe, complicated malaria (in whom parasitaemia and drug response need to be followed very carefully). Follow-up (within 28 days of diagnosis) of the 58 malaria cases detected in the field revealed that the OptiMAL test can be used to detect re-infection with a different Plasmodium sp. (sensitivity = 100%; specificity = 100%; J-index = 1) or recrudescence/re-infection with the same Plasmodium sp. (sensitivity = 83%; specificity = 100%; J-index = 0.83) accurately. The ability to use the test to distinguish P. falciparum from P. vivax, and to identify mixed infections of these two species, is of great significance in areas where the preferred and effective therapy for P. falciparum malaria differs from that for P. vivax.

Ahaptoglobinemia (HpO) and malaria in India

Haptoglobin (Hp) polymorphism analysed among P. vivax and P. falciparum patients and malaria negative subjects from areas with different epidemiological situations had shown high incidence of ahaptoglobinemia (HpO) among malaria patients. A definite association of HpO with P. vivax as well as P. falciparum malaria in Indian subjects had been observed. However, low sensitivity and reliability of HpO index indicates that it can not be a good indicator for determination of malaria endemicity. About 75 per cent of HpO subjects with P. vivax infection when treated with chloroquine showed typable Hp polymorphs by 8-9 days of post-treatment.

Dynamics of malaria transmission under changing ecological scenario in and around Nanak Matta Dam, Uttaranchal, India

To understand the transmission dynamics of malaria in three different ecotypes, namely watershed (forest), seepage (Nanak Matta Dam) and plain (non-forest, non-dam) areas of Nainital and Udham Singh Nagar districts of Uttaranchal, entomological and parasitological investigations were carried out from July 1996 to June 1997. In the three ecotypes, average per man hour densities of adult vector species in human dwellings and cattlesheds recorded were high for Anopheles culicifacies from April to September and October to March for An. fluviatilis. Prevalence of both An. culicifacies and An. fluviatilis was higher in the forest area as compared to other two areas. Observations on gonotrophic condition revealed endophilic tendency of both vector species. Higher number of both vector species were found in outdoor than indoor during night human bait collections. Out of 864 specimens of An. fluviatilis dissected, one showed natural infection of sporozoites in salivary glands in the month of November from the forest area only. Sibling species study of An. fluviatilis revealed the presence of species S for the first time in the forest area. Parasitological investigations also depicted high incidence of malaria in the forest area as compared to other two areas. Overall results from the study indicated active malaria transmission in the forest area.

Investigation of malaria outbreak in Bahraich district, Uttar Pradesh

BACKGROUND & OBJECTIVES

Based on the reports of 139 fever related deaths in Jarwal primary health centre (PHC) of Bahraich district, Uttar Pradesh (UP) during April to September 1999, a study was undertaken to explore the possibility of outbreak of Plasmodium falciparum malaria in the area and reasons of outbreak.

METHODS

The study was undertaken during September-October 1999 in Bahraich district, UP. The study included a parasitological and an entomological survey. Blood slides from fever cases were collected and examined following standard procedures for detection of species and stage of parasite. The resting adult mosquitoes were collected from human dwellings and cattle sheds from selected villages. Susceptibility status of Anopheles culicifacies to 4 per cent DDT and 0.05 per cent deltamethrin was determined under laboratory conditions following the WHO procedure. In vitro drug sensitivity of P. falciparum to chloroquine was also estimated.

RESULTS

Overall slide positivity rate (SPR) was found to be 33.8 with a preponderance of P. falciparum (88.4%). There was an outbreak of Pf malaria in Jarwal and surrounding areas as well. Foci of P. falciparum malaria were found in Jarwal, Fakharpur and Hazoorpur PHCs around Kaisarganj PHC. In addition, P. falciparum cases, were also reported from Motipur and Tejwapur.

INTERPRETATION & CONCLUSION

Poor surveillance of affected areas resulting in low annual parasite incidence (API), lack of insecticidal spray in the currently affected PHCs as the API was less than 2 and development of resistance in P. falciparum to chloroquine were found as the possible reasons for the outbreak. It is recommended that surveillance be strengthened in all PHCs of Bahraich district to contain further extension of malaria in northeastern UP.

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.

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.

Chloroquine and desethylchloroquine concentrations in blood cells and plasma from Indian patients infected with sensitive or resistant Plasmodium falciparum

The sensitivities of 61 Indian cases of Plasmodium falciparum malaria to chloroquine (CQ) were investigated using in-vitro and in-vivo methods. Concentrations of CQ and desethylchloroquine (DCQ) in blood cells and plasma from CQ-sensitive and -resistant cases were determined 2 and 7 days after initiation of treatment, by HPLC. On day 2, the mean CQ concentrations in the samples collected from the sensitive cases were higher than those in the samples from the resistant patients, in plasma (0.47 v. 0.32 microgram/ml; P < 0.02) and particularly in the blood cells (1.51 v. 0.46 micrograms/ml; P < 0.001). By day 7, however, the CQ concentrations in the two groups were similar. Although, on day 2, the mean ratio of the CQ to DCQ concentrations was significantly higher in the blood cells from the sensitive group than in those from the resistant cases (P < 0.01), the CQ/DCQ ratios for the plasma were similar for the two groups. Similarly, the mean ratio between the blood-cell concentration of CQ on day 2 and the concurrent plasma concentration (BPr) was also relatively high in the sensitive group (P < 0.001).

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.

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.

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.

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.

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.

Genetic structure of Plasmodium vivax isolates in India

Variations in the allelic composition of glucose phosphate isomerase (GPI), NADP-dependent glutamate dehydrogenase (GDH) and adenosine deaminase (ADA) enzyme systems of Plasmodium vivax were observed in isolates of Indian origin in 1985-1993. No significant difference was observed in allelic frequencies in different years. The data indicated random distribution of GPI, GDH and ADA alleles among the isolates, suggesting that loci for these enzymes were not linked. A high proportion of the isolates comprised at least 2 genetically distinct clones, the mean number of clones per isolate being 1.4. There was no significant difference in the number of oocysts in Anopheles stephensi fed on uniclonal and multiclonal isolates. No difference was observed in the proportions of uniclonal and multiclonal isolates during low and high transmission periods.

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.

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.

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.

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%.

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.

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.

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.

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).

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.

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.

Plasmodium vivax: enzyme polymorphism in isolates of Indian origin

185 isolates of Plasmodium vivax were collected from patients visiting the malaria clinic run by the National Malaria Eradication Programme, Delhi, India. Percoll gradient centrifugation was used to concentrate P. vivax parasites from 0.4 to 0.5 ml of blood collected by finger prick. The parasite concentrate from each isolate was electrophoretically analysed for lactate dehydrogenase (LDH), NADP-dependent glutamate dehydrogenase (GDH), glucose phosphate isomerase (GPI) and adenosine deaminase (ADA). Variations were observed in GPI, GDH and ADA systems. Four electrophoretic forms of GPI and 5 each of GDH and ADA were observed. Electrophoretic mobilities of the different isoenzymic forms in P. vivax were identical to those reported for P. falciparum, indicating that the 2 species cannot be differentiated on the basis of electrophoretic patterns of the 4 enzyme systems studied.

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.

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.

X-linkage of malic enzyme in Anopheles culicifacies species B

A survey for malic enzyme (Me) in laboratory strains of species A and species B of Anopheles culicifacies had uncovered two electrophoretic variants, slow and fast, in two strains of species B. Genetic analysis revealed the two variants to be codominant alleles segregating at a locus, Me, which is sex linked. Because of the XX-XY sex determining mechanism, in F1 females, two electromorphs, viz., slow and fast, were observed, whereas in males only one electromorph of maternal origin was seen. Linkage experiments with another X-linked mutant, white eye (w), indicated the map distance between the two loci to be 9.52 +/- 0.86.