Impact of DDT spraying on malaria transmission in Bareilly District, Uttar Pradesh, India

Background & objectives: Impact of indoor residual spraying of DDT on malaria transmission andvector density was evaluated in six villages of Shergarh PHC, Bareilly district, Uttar Pradesh under theoperational condition of National Vector Borne Disease Control Programme (NVBDCP) from July 2001to March 2002 (one transmission season only).Methods: Two rounds of DDT (50% WDP) spraying @ 1 g/m2 were done both in the experimental andcontrol villages by the state health authorities. The spraying in experimental villages was supervisedby Malaria Research Centre (MRC) whereas the district health authorities supervised the operation incontrol villages. Mass blood surveys were made three times— before the first round, in between thefirst and second rounds and after the second round of spraying. The blood smears were examined bythe trained microscopists of MRC, Haldwani. From the above examinations epidemiological indicatorssuch as slide positivity rate (SPR), slide falciparum rate (SFR) and infant parasite rate (IPR) werecalculated. All malaria positive cases were given radical treatment as per NVBDCP schedule.Entomological parameters such as per man hour mosquito density, parity rate, gonotrophic conditionand adult susceptibility status of Anopheles culicifacies to diagnostic dosages of DDT (4%) weremonitored as per the standard techniques.Results: A total of 988.5 kg of DDT was consumed during two rounds of spray. The house coveragevaried from 87 to 95.3%. Parasitological evaluation revealed significant reduction in malaria cases (p <0.0005) and infant parasite rate declined from 2.9 to 0%. Entomological observations revealedconsiderable reduction in the density of malaria vector An. culicifacies despite of its 21.4% mortalityagainst DDT test papers.Interpretation & conclusion: The overall results of the study revealed that DDT is still a viableinsecticide in indoor residual spraying owing to its effectivity in well supervised spray operation andhigh excitorepellencyfactor

Assessment of therapeutic efficacy of chloroquine and sulphadoxine-pyrimethamine in uncomplicated falciparum malaria

A standardised protocol has been developed by World Health Organization (CDS/RBM/2002) toassess the efficacy of common antimalarials in the treatment of clinically manifested infection withuncomplicated P. falciparum malaria for areas with low to moderate transmission. The therapeuticefficacy protocol is based on clinical and parasitological responses of the patients and it has thepurpose of determining the practical efficacy of the drug regimen in study areas with the ultimateobjective of ascertaining its continued usefulness or the necessity for replacing it in the routinetreatment. Present study has been conducted at seven sites—Kathiatali and Simonabasti of DistrictNowgaon, Assam; Sonapur and Boko of District Kamrup, Assam; Keonjhar Town, Padampur andBasudebpur of District Keonjhar, Orissa. In order to reduce the patient recruitment time, health centreclose to well-defined community was identified to conduct the activities at peak malaria seasonby selecting local pockets and organising mobile clinics. Microscopically confirmed cases of P. falciparumwere enrolled according to the criteria for inclusion and exclusion. Treatment with recommendeddrug was given under supervision and a follow-up schedule at various intervals for 28days was maintained. In chloroquine (CQ) study areas, wherever patients showed treatment failure,they were treated with second line drug—sulphadoxine-pyrimethamine (SP) combination and thenfollowed-up as per study protocol. It was observed that 30% cases showed treatment failure to CQin District Nowgaon, where revised drug policy has already been introduced. In Kamrup district,treatment failure with CQ was found to be less than 25%, which denotes the said regimen is still effective.Almost all the patients from Padampur and Basudebpur of District Keonjhar responded toCQ, treatment failure was noticed only in two patients (3%). The antifolate combination found to befully effective as second line and also as first line wherever revised drug policy has been introduced

PCR-based methods for the detection of L1014 kdr mutation in Anopheles culicifacies sensu lato

<p>Abstract</p> <p>Background</p> <p><it>Anopheles culicifacies s.l</it>., a major malaria vector in India, has developed widespread resistance to DDT and is becoming resistant to pyrethroids–the only insecticide class recommended for the impregnation of bed nets. Knock-down resistance due to a point mutation in the voltage gated sodium channel at L1014 residue (<it>kdr</it>) is a common mechanism of resistance to DDT and pyrethroids. The selection of this resistance may pose a serious threat to the success of the pyrethroid-impregnated bed net programme. This study reports the presence of <it>kdr </it>mutation (L1014F) in a field population of <it>An. culicifacies s.l</it>. and three new PCR-based methods for <it>kdr </it>genotyping.</p> <p>Methods</p> <p>The IIS4-IIS5 linker to IIS6 segments of the para type voltage gated sodium channel gene of DDT and pyrethroid resistant <it>An. culicifacies s.l</it>. population from the Surat district of India was sequenced. This revealed the presence of an A-to-T substitution at position 1014 leading to a leucine-phenylalanine mutation (L1014F) in a few individuals. Three molecular methods viz. Allele Specific PCR (AS-PCR), an Amplification Refractory Mutation System (ARMS) and Primer Introduced Restriction Analysis-PCR (PIRA-PCR) were developed and tested for <it>kdr </it>genotyping. The specificity of the three assays was validated following DNA sequencing of the samples genotyped.</p> <p>Results</p> <p>The genotyping of this <it>An. culicifacies s.l</it>. population by the three PCR based assays provided consistent result and were in agreement with DNA sequencing result. A low frequency of the <it>kdr </it>allele mostly in heterozygous condition was observed in the resistant population. Frequencies of the different genotypes were in Hardy-Weinberg equilibrium.</p> <p>Conclusion</p> <p>The Leu-Phe mutation, which generates the <it>kdr </it>phenotype in many insects, was detected in a pyrethroid and DDT resistant <it>An. culicifacies s.l</it>. population. Three PCR-based methods were developed for <it>kdr </it>genotyping. All the three assays were specific. The ARMS method was refractory to non-specific amplification in non-stringent amplification conditions. The PIRA-PCR assay is able to detect both the codons for the phenylalanine mutation at <it>kdr </it>locus, i.e., TTT and TTC, in a single assay, although the latter codon was not found in the population genotyped.</p

Genetic structure of Plasmodium falciparum field isolates in eastern and north-eastern India

<p>Abstract</p> <p>Background</p> <p>Molecular techniques have facilitated the studies on genetic diversity of <it>Plasmodium </it>species particularly from field isolates collected directly from patients. The <it>msp-1 </it>and <it>msp-2 </it>are highly polymorphic markers and the large allelic polymorphism has been reported in the block 2 of the <it>msp-1 </it>gene and the central repetitive domain (block3) of the <it>msp-2 </it>gene. Families differing in nucleotide sequences and in number of repetitive sequences (length variation) were used for genotyping purposes. As limited reports are available on the genetic diversity existing among <it>Plasmodium falciparum </it>population of India, this report evaluates the extent of genetic diversity in the field isolates of <it>P. falciparum </it>in eastern and north-eastern regions of India.</p> <p>Methods</p> <p>A study was designed to assess the diversity of <it>msp-1 </it>and <it>msp-2 </it>among the field isolates from India using allele specific nested PCR assays and sequence analysis. Field isolates were collected from five sites distributed in three states namely, Assam, West Bengal and Orissa.</p> <p>Results</p> <p><it>P. falciparum </it>isolates of the study sites are highly diverse in respect of length as well as sequence motifs with prevalence of all the reported allelic families of <it>msp-1 </it>and <it>msp-2</it>. Prevalence of identical allelic composition as well as high level of sequence identity of alleles suggest a considerable amount of gene flow between the <it>P. falciparum </it>populations of different states. A comparatively higher proportion of multiclonal isolates as well as multiplicity of infection (MOI) was observed among isolates of highly malarious districts Karbi Anglong (Assam) and Sundergarh (Orissa). In all the five sites, R033 family of <it>msp-1 </it>was observed to be monomorphic with an allele size of 150/160 bp. The observed 80–90% sequence identity of Indian isolates with data of other regions suggests that Indian <it>P. falciparum </it>population is a mixture of different strains.</p> <p>Conclusion</p> <p>The present study shows that the field isolates of eastern and north-eastern regions of India are highly diverse in respect of <it>msp-1 </it>(block 2) and <it>msp-2 </it>(central repeat region, block 3). As expected Indian isolates present a picture of diversity closer to southeast Asia, Papua New Guinea and Latin American countries, regions with low to meso-endemicity of malaria in comparison to African regions of hyper- to holo-endemicity.</p

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

Genetics of isocitrate dehydrogenase in Anopheles stephensi

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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

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

Biochemical mechanisms of malathion resistance in Indian Anopheles culicifacies (Diptera: Culicidae) sibling species A, B, and C: microplate assays and synergistic studies

Anopheles culicifacies Giles is a complex of 4 sibling species, A, B, C, and D. In view of the differences among sympatric sibling species in the levels of susceptibility to malathion, a study was carried out to determine the resistance mechanism(s). The study was carried out in Andhra Pradesh and Gujarat states where species B and C are sympatric and in Uttar Pradesh and Haryana states where species A and B are sympatric. Microplate biochemical assays on field-collected malathion-resistant species A, B, and C indicated the noninvolvement of elevated levels of nonspecific esterases and insensitive acetylcholinesterase. Bioassays with the synergist triphenyl phosphate (a specific carboxylesterase inhibitor) have indicated the involvement of carboxylesterase as the major mechanism of malathion resistance in these species