Perceived needs of disease vector control programs: A review and synthesis of (sub)national assessments from South Asia and the Middle East

Systems for disease vector control should be effective, efficient, and flexible to be able to tackle contemporary challenges and threats in the control and elimination of vector-borne diseases. As a priority activity towards the strengthening of vector control systems, it has been advocated that countries conduct a vector-control needs assessment. A review was carried out of the perceived needs for disease vector control programs among eleven countries and subnational states in South Asia and the Middle East. In each country or state, independent teams conducted vector control needs assessment with engagement of stakeholders. Important weaknesses were described for malaria, dengue and leishmaniases regarding vector surveillance, insecticide susceptibility testing, monitoring and evaluation of operations, entomological capacity and laboratory infrastructure. In addition, community mobilization and intersectoral collaboration showed important gaps. Countries and states expressed concern about insecticide resistance that could reduce the continued effectiveness of interventions, which demands improved monitoring. Moreover, attainment of disease elimination necessitates enhanced vector surveillance. Vector control needs assessment provided a useful planning tool for systematic strengthening of vector control systems. A limitation in conducting the vector control needs assessment was that it is time- and resource-intensive. To increase the feasibility and utility of national assessments, an abridged version of the guidance should focus on operationally relevant topics of the assessment. Similar reviews are needed in other regions with different contextual conditions.

Implications of insecticide resistance for malaria vector control with long-lasting insecticidal nets: a WHO-coordinated, prospective, international, observational cohort study

BACKGROUND

Scale-up of insecticide-based interventions has averted more than 500 million malaria cases since 2000. Increasing insecticide resistance could herald a rebound in disease and mortality. We aimed to investigate whether insecticide resistance was associated with loss of effectiveness of long-lasting insecticidal nets and increased malaria disease burden.

METHODS

This WHO-coordinated, prospective, observational cohort study was done at 279 clusters (villages or groups of villages in which phenotypic resistance was measurable) in Benin, Cameroon, India, Kenya, and Sudan. Pyrethroid long-lasting insecticidal nets were the principal form of malaria vector control in all study areas; in Sudan this approach was supplemented by indoor residual spraying. Cohorts of children from randomly selected households in each cluster were recruited and followed up by community health workers to measure incidence of clinical malaria and prevalence of infection. Mosquitoes were assessed for susceptibility to pyrethroids using the standard WHO bioassay test. Country-specific results were combined using meta-analysis.

FINDINGS

Between June 2, 2012, and Nov 4, 2016, 40 000 children were enrolled and assessed for clinical incidence during 1·4 million follow-up visits. 80 000 mosquitoes were assessed for insecticide resistance. Long-lasting insecticidal net users had lower infection prevalence (adjusted odds ratio [OR] 0·63, 95% CI 0·51-0·78) and disease incidence (adjusted rate ratio [RR] 0·62, 0·41-0·94) than did non-users across a range of resistance levels. We found no evidence of an association between insecticide resistance and infection prevalence (adjusted OR 0·86, 0·70-1·06) or incidence (adjusted RR 0·89, 0·72-1·10). Users of nets, although significantly better protected than non-users, were nevertheless subject to high malaria infection risk (ranging from an average incidence in net users of 0·023, [95% CI 0·016-0·033] per person-year in India, to 0·80 [0·65-0·97] per person year in Kenya; and an average infection prevalence in net users of 0·8% [0·5-1·3] in India to an average infection prevalence of 50·8% [43·4-58·2] in Benin).

INTERPRETATION

Irrespective of resistance, populations in malaria endemic areas should continue to use long-lasting insecticidal nets to reduce their risk of infection. As nets provide only partial protection, the development of additional vector control tools should be prioritised to reduce the unacceptably high malaria burden.

FUNDING

Bill & Melinda Gates Foundation, UK Medical Research Council, and UK Department for International Development.

Monitoring of long-lasting insecticidal nets (LLINs) coverage versus utilization: a community-based survey in malaria endemic villages of Central India

Background

Despite the known effectiveness of long-lasting insecticidal nets (LLINs) in providing protection against malaria, high level of ownership and use are very difficult to achieve and maintain. Nearly 40,000 LLINs were distributed in 2014 as an intervention tool against malaria transmission in 80 villages of Keshkal sub-district in Chhattisgarh, India. This study assessed LLIN coverage, access, utilization pattern, and key determinants for the net use 1 year after mass distribution.

Methods

In 2015, a cross-sectional household survey was carried out in 80 study clusters (whole village or part of village). From each cluster, 40 households were randomly selected and interviewed using a structured questionnaire adapted from the malaria indicator survey of Roll Back Malaria guidelines. Information on demographic characteristics, LLIN ownership, and its use on the night before the survey, and physical condition of LLINs were recorded.

Results

2970 households were interviewed with a total of 15,003 individuals present in the households during the night before the survey. Nearly 98% of households had at least one LLIN and 59.4% of the surveyed population reportedly used an LLIN the previous night. LLIN use varied from 41 to 94% between the study clusters. Nearly 89% of the LLINs were found in good physical condition (without holes). However, proportion of household with at least one LLIN per two persons was only 39%.

Conclusion

Universal coverage of LLINs was inadequate in the study clusters making it difficult for all household members to use an LLIN. LLIN use varied between clusters and was highest in children under 5 years of age. Health education campaigns and creating awareness about the benefit of sleeping under the LLINs in providing protection against malaria is required not only to high risk groups of pregnant women and children below 5 years of age but all the members of the family to have an epidemiological impact of this intervention at the community level. Relatively high net use despite poor access to LLINs indicates an overall desire to use nets when they are available. The main barrier to increased use of nets is the low coverage at household level.

Additional burden of asymptomatic and sub-patent malaria infections during low transmission season in forested tribal villages in Chhattisgarh, India

Background

The burden of sub-patent malaria is difficult to recognize in low endemic areas due to limitation of diagnostic tools, and techniques. Polymerase chain reaction (PCR), a molecular based technique, is one of the key methods for detection of low parasite density infections. The study objective was to assess the additional burden of asymptomatic and sub-patent malaria infection among tribal populations inhabiting three endemic villages in Keshkal sub-district, Chhattisgarh, India. A cross-sectional survey was conducted in March–June 2016, during the low transmission season, to measure and compare prevalence of malaria infection using three diagnostics: rapid diagnostic test, microscopy and nested-PCR.

Results

Out of 437 individuals enrolled in the study, 103 (23.6%) were malaria positive by PCR and/or microscopy of whom 89.3% were Plasmodium falciparum cases, 77.7% were afebrile and 35.9% had sub-patent infections.

Conclusions

A substantial number of asymptomatic and sub-patent malaria infections were identified in the survey. Hence, strategies for identifying and reducing the hidden burden of asymptomatic and sub-patent infections should focus on forest rural tribal areas using more sensitive molecular diagnostic methods to curtail malaria transmission.

Burden of asymptomatic malaria among a tribal population in a forested village of central India: a hidden challenge for malaria control in India

Objective

Chhattisgarh in India is a malaria-endemic state with seven southern districts that contributes approximately 50–60% of the reported malaria cases in the state every year. The problem is further complicated due to asymptomatic malaria cases which are largely responsible for persistent transmission. This study was undertaken in one of the forested villages of the Keshkal subdistrict in Kondagaon district to ascertain the proportion of the population harbouring subclinical malarial infections.

Study design

Community-based cross-sectional study.

Methods

Mass blood surveys were undertaken of the entire population of the village in the post-monsoon seasons of 2013 and 2014. Fingerprick blood smears were prepared from individuals of all ages to detect malaria infections in their blood. Individuals with fever at the time of the survey were tested with rapid diagnostic tests, and parasitaemia in thick blood smears was confirmed by microscopy. Malaria-positive cases were treated with anti-malarials in accordance with the national drug policy.

Results

Peripheral blood smears of 134 and 159 individuals, including children, were screened for malaria infection in 2013 and 2014, respectively. Overall, the malaria slide positivity rates were 27.6% and 27.7% in 2013 and 2014, respectively, and the prevalence rates of asymptomatic malaria were 20% and 22.8%. This study showed that, for two consecutive years, the prevalence of asymptomatic malaria infection was significantly higher among children aged ≤14 years (34.4% and 34.1% for 2013 and 2014, respectively) compared with adults (15.2% and 18.2% for 2013 and 2014, respectively; P = 0.023 and 0.04, respectively).

Conclusion

The number of asymptomatic malaria cases, especially Plasmodium falciparum, is significant, reinforcing the underlying challenge facing the malaria elimination programme in India.

•

The study was carried out in a difficult-to-reach forested village with minimal access to healthcare facilities.

•

There exists a large proportion of asymptomatic cases in the community.

•

Children aged under 14 years comprised higher number of asymptomatic cases than adults.

•

This underlines one of the potential challenges of public health in malaria control and elimination programs.

Impact of long-lasting insecticidal nets on prevalence of subclinical malaria among children in the presence of pyrethroid resistance in Anopheles culicifacies in Central India

BACKGROUND

Subclinical (asymptomatic) cases of malaria could be a major barrier to the success of malaria elimination programs. This study has evaluated the impact of long-lasting insecticidal nets (LLINs) on the prevalence of subclinical malaria in the presence of pyrethroid resistance in the main malaria vector Anopheles culicifacies on malaria transmission among a cohort of children in villages of the Keshkal sub-district in Chhattisgarh state.

METHODS

A cohort of 6582 children ages less than 14 years was enrolled from 80 study clusters. Post monsoon survey was carried out at baseline before LLIN distribution, and 5862 children were followed up in the subsequent year. Study outcomes included assessment of subclinical malarial infections and use of LLINs among the study cohort in the presence of varied levels of pyrethroid resistance.

FINDINGS

In the baseline survey, the proportion of subclinical malaria was 6·1%. LLIN use during the previous night was 94·8%. Overall, prevalence of subclinical malaria was significantly reduced to 1% (p<0·001) in the second survey. LLIN users were protected from malaria (OR: 0·25, 95% CI=0·12-0·52, p<0.001) and subclinical malaria (OR: 0·25, 95% CI=0·11-0·58, p=0·001) despite the presence of pyrethroid resistance in the study area.

INTERPRETATION

In this low transmission area, sleeping under LLINs significantly reduced the burden of malaria among children. In the presence of pyrethroid resistant malaria vector, a high LLIN use of 94·5% was observed to have significantly brought down the proportion of subclinical malaria among the cohort children.

Evaluation of SYBR green I based visual loop-mediated isothermal amplification (LAMP) assay for genus and species-specific diagnosis of malaria in P. vivax and P. falciparum endemic regions

BACKGROUND & OBJECTIVES

Loop-mediated isothermal amplification (LAMP) is an emerging nucleic acid based diag- nostic approach that is easily adaptable to the field settings with limited technical resources. This study was aimed to evaluate the LAMP assay for the detection and identification of Plasmodium falciparum and P. vivax infection in malaria suspected cases using genus and species-specific assay.

METHODS

The 18S rRNA-based LAMP assay was evaluated for diagnosis of genus Plasmodium, and species- specific diagnosis of P. falciparum and P. vivax, infection employing 317 malaria suspected cases, and the results were compared with those obtained by 18S nested PCR (n-PCR). All the samples were confirmed by microscopy for the presence of Plasmodium parasite.

RESULTS

The n-PCR was positive in all Plasmodium-infected cases (n=257; P. falciparum=133; P. vivax=124) and negative in microscopy negative cases (n=58) except for two cases which were positive for P. vivax, giving a sen- sitivity of 100% (95% CI: 97.04-100%) and a specificity of 100% (95% CI: 88.45-99.5%). Genus-specific LAMP assay missed 11 (3.2%) microscopy and n-PCR confirmed vivax malaria cases. Considering PCR results as a refer- ence, LAMP was 100% sensitive and specific for P. falciparum, whereas it exhibited 95.16% sensitivity and 96.7% specificity for P. vivax. The n-PCR assay detected 10 mixed infection cases while species-specific LAMP detected five mixed infection cases of P. vivax and P. falciparum, which were not detected by microscopy.

INTERPRETATION & CONCLUSION

Genus-specific LAMP assay displayed low sensitivity. Falciparum specific LAMP assay displayed high sensitivity whereas vivax specific LAMP assay displayed low sensitivity. Failed detection of vivax cases otherwise confirmed by the n-PCR assay indicates exploitation of new targets and improved detection methods to attain 100% results for P. vivax detection.

Monitoring the efficacy of antimalarial medicines in India via sentinel sites: Outcomes and risk factors for treatment failure

BACKGROUND & OBJECTIVES

To combat the problem of antimalarial drug resistance, monitoring the changes in drug efficacy over time through periodic surveillance is essential. Since 2009, systematic and continuous monitoring is being done through nationwide sentinel site system. Potential early warning signs like partner drug resistance markers were also monitored in the clinical samples from the study areas.

METHODS

A total of 1864 patients with acute uncomplicated malaria were enrolled in therapeutic efficacy studies of artesunate plus sulphadoxine-pyrimethamine (AS+SP) for Plasmodium falciparum; those infected with P. vivax were given chloroquine (CQ). Polymerase chain reaction (PCR) was used to distinguish post-treatment reinfection from treatment failures. Isolates of P. falciparum were also analysed for dihydropteroate synthase (dhps) and dihydrofolate reductase (dhfr) gene mutations.

RESULTS

Overall, 1687 (91.7%) patients completed the follow-up. In most of the falciparum patients the parasitaemia was cleared within 24 h of treatment, except 12 patients who remained parasite positive after 72 h. Presence of dhfr and dhps quintuple mutation was observed predominantly in treatment failure samples. A daily dose of artesunate of < 3 mg/kg of body weight, age of <5 yr, and fever at enrolment were associated with an increased risk of treatment failure. The AS+SP in P. falciparum was effective in > 95% cases in all the sentinel sites except in Northeastern region (NE). Chloroquine remained 100% efficacious in case of P. vivax infections.

INTERPRETATION & CONCLUSION

Till 2012, India's national antimalarial drug resistance monitoring system proved highly efficacious and safe towards first-line antimalarials used in the country, except in Northeastern region where a decline in efficacy of AS+SP has been observed. This led to change in first-line treatment for P. falciparum to artemether-lumefantrine in Northeastern region.

Knockdown resistance (kdr) mutations in Indian Anopheles culicifacies populations

Background

Anopheles culicifacies s.l. is one of the primary vectors of malaria in India responsible for the highest number of malaria cases. This vector is resistant to DDT in most parts of the country with indication of emerging resistance to pyrethroids. Since knockdown resistance (kdr) is known to confer cross-resistance between DDT and pyrethroids owing to a common target site of action, knowledge of prevalence of knockdown resistance (kdr) alleles is important from insecticide resistance management point of view.

Methods

Nine populations of An. culicifacies belonging to five states of India, representing northern, western and central-east India, were screened for the presence of two alternative kdr mutations L1014F and L1014S using PCR-based assays. Dead and alive mosquitoes, following WHO standard insecticide susceptibility test against deltamethrin and DDT, were tested for allelic association.

Results

L1014F mutation was recorded in all populations studied except from Haryana and Rajasthan states in northern India, with low frequencies ranging between 0.012 and 0.076; whereas presence of L1014S mutation was recorded in five populations only belonging to central-east India, with allelic frequencies ranging between 0.010 and 0.046. Both the kdr mutant alleles were found mostly in heterozygous condition without deviating from Hardy-Weinberg equilibrium. Both mutations showed protection against deltamethrin whereas only L1014S mutation showed protection against DDT when tested using additive model.

Conclusions

The two L1014-kdr mutations, L1014F and L1014S, co-occurred in five populations belonging to Chhattisgarh and Odisha states of India whereas L1014F was present in all populations studied except populations from northern states. Both kdr mutations were found with very low allelic frequencies mostly in heterozygous condition and exhibited protection against deltamethrin.

Standardization of a bottle assay--an indigenous method for laboratory and field monitoring of insecticide resistance and comparison with WHO adult susceptibility test

The WHO adult susceptibility test is in use for insecticide resistance monitoring. Presently, materials are being imported from the Universiti Sains Malaysia, Malaysia and sometimes it is cost prohibitive. As an alternative, we present here a method of bottle bioassay using indigenous material. Different aspects related to the assay were studied and validated in the field. Bottle assay was standardized in the laboratory by using locally sourced material and laboratory-maintained insecticide-susceptible Anopheles stephensi and Aedes aegypti strains against technical grade deltamethrin and cyfluthrin insecticides dissolved in ethanol in a range of different concentrations. The frequency of use of the deltamethrin-coated bottles and shelf-life were determined. Discriminating dose for deltamethrin and cyfluthrin was 10 μg against An. stephensi and 2 μg against Ae. aegypti females. Insecticide-coated bottles stored at 25 to 35 °C can be used for three exposures within 7 days of coating. The study carried out in the laboratory was validated on wild caught An. culicifacies in the states of Odisha and Chhattisgarh against deltamethrin-coated bottles in comparison to WHO adult susceptibility test. Results of the study indicated that deltamethrin-coated bottles were effective up to three exposures within 7 days of coating for field population and 100% mortality was recorded within 35 min as observed in laboratory studies for field collected susceptible population. Also in the WHO adult susceptibility test, 100% knock-down within 35 min and 100% mortality after 24 h holding period were observed in susceptible population, while in it was 50% knock-down in 1 h and 64% mortality after 24 h holding period for resistant population (50% mortality in bottle assay in 60 min). The bottle assay can be used as an alternative to the WHO adult susceptibility test both in the laboratory and field for monitoring insecticide resistance in mosquito vectors using locally sourced material.

Genetic deletion of HRP2 and HRP3 in Indian Plasmodium falciparum population and false negative malaria rapid diagnostic test

Genetic polymorphisms in diagnostic antigens are important factors responsible for variable performance of rapid diagnostic tests. Additionally, the failure of antigen expression due to gene deletion may also contribute to variable performance. We report Indian Plasmodium falciparum field isolates lacking both Pfhrp2 and Pfhrp3 genes leading to false negative results of rapid diagnostic tests. The study highlights need to determine the prevalence of P. falciparum isolates lacking these genes in larger field populations in India.

Monitoring antimalarial drug resistance in India via sentinel sites: outcomes and risk factors for treatment failure, 2009-2010

OBJECTIVE

To describe India's National Antimalarial Drug Resistance Monitoring System, measure the efficacy of first-line malaria treatments, and determine risk factors for treatment failure.

METHODS

In 2009-2010, prospective studies with 28 days of follow-up were conducted at 25 sentinel sites. Patients infected with Plasmodium falciparum were given artesunate plus sulfadoxine-pyrimethamine (AS+SP); those infected with P. vivax were given chloroquine. Polymerase chain reaction was used to distinguish post-treatment reinfection from treatment failure. Isolates of P. falciparum were checked for dhfr and dhps mutations.

FINDINGS

Overall, 1664 patients were enrolled. Kaplan-Meier survival analysis showed an efficacy of 98.8% for AS+SP. Most patients with P. falciparum parasitaemia cleared their parasitaemias within 24 hours of treatment initiation, but six, including four with treatment failure, remained parasitaemic after 72 hours. Double mutants in dhfr were found in 68.4% of the genotyped isolates. Triple or quadruple mutants in dhfr and mutations in dhps were rare. A daily dose of artesunate of < 3 mg per kg of body weight, age of less than 5 years, and fever at enrolment were associated with an increased risk of treatment failure. Chloroquine remained 100% efficacious and generally cleared P. vivax parasitaemias within 48 hours. Vomiting (seen in 47 patients) was the most common adverse event.

CONCLUSION

India's National Antimalarial Drug Resistance Monitoring System provides wide coverage. The first-line antimalarials used in the country remain safe and efficacious. The treatment of malaria in young children and the relative benefits of age- and weight-based dosing need further exploration.

Prevalence and incrimination of Anopheles fluviatilis species S (Diptera: Culicidae) in a malaria endemic forest area of Chhattisgarh state, central India

Background

Chhattisgarh state in central India is highly endemic for malaria and contributes about 13% of annually reported malaria cases in the country with predominance of P. falciparum. Entomological investigations were carried out in a tribal forested area of district Bastar located in the southern part of Chhattisgarh state to record the prevalence of sibling species of Anopheles fluviatilis and An. culicifacies complexes. The vector species complexes were investigated at sibling species level for their biology in terms of resting and feeding behavior and malaria transmission potential.

Methods

Indoor resting vector mosquitoes collected during 2010–2011 were identified to sibling species by cytotaxonomy and polymerase chain reaction (PCR) assay. The blood meal source analysis and incrimination studies were done at sibling species level by counter current immunoelectrophoresis and enzyme linked immunosorbent assay (ELISA) respectively.

Results

Analysis of sibling species composition revealed predominance of An. fluviatilis species S in the study area, which was found to be highly anthropophagic and rested in human dwellings whereas the sympatric species T was primarily zoophagic. Incrimination studies showed high sporozoite rate in species S, thereby confirming its vectorial efficiency. An. culicifacies was encountered in low numbers and comprised species B and C in almost equal proportion. Both these species were found to be exclusively zoophagic.

Conclusion

The observations made strongly suggest that species S of Fluviatilis Complex is the principal vector of malaria in certain forest areas of district Bastar, Chhattisgarh state and should be the target species for vector control operation. Vector control strategies based on biological characteristics of Fluviatilis S will lead to substantial decline in malaria incidence in such areas.

Effectiveness and durability of Interceptor® long-lasting insecticidal nets in a malaria endemic area of central India

BACKGROUND

In the present study, Interceptor®, long-lasting polyester net, 75 denier and bursting strength of minimum 250 kPa coated with alpha-cypermethrin @ 200 mg/m² was evaluated for its efficacy in reducing the mosquito density, blood feeding inhibition and malaria incidence in a tribal dominated malaria endemic area in Chhattisgarh state, central India. Its durability, washing practices and usage pattern by the community was also assessed up to a period of three years.

METHODS

The study was carried out in two phases. In the first phase (September 2006 to August 2007), 16 malaria endemic villages in district Kanker were randomized into three groups, viz. Interceptor net (LN), untreated polyester net (100 denier) and without net. Malaria cases were detected by undertaking fortnightly surveillance by home visits and treated as per the national drug policy. Mosquito collections were made by hand catch and pyrethrum space spray methods from human dwellings once every month. Slide positivity rate (SPR) and malaria incidence per 1000 population (PI) were compared between the three study arms to assess the impact of use of Interceptor nets. Simultaneously, wash resistance studies were carried out in the laboratory by doing cone bioassays on Interceptor LNs washed up to 20 times. Activities undertaken in second Phase (April 2008 to October 2009) after an interval of about 18 months post-net distribution included questionnaire based surveys at every six months, i.e. 18, 24, 30 and 36 months to observe durability, usage pattern of LNs and washing practices by the community. After 36 months of field use, 30 nets were retrieved and sampled destructively for chemical analysis.

RESULTS

Interceptor nets were found effective in reducing the density, parity rate and blood feeding success rate of main malaria vector Anopheles culicifacies as compared to that in untreated net and no net villages. SPR in LN villages was 3.7% as compared to 6.5% in untreated and 11% in no net villages. PI in LN villages was 16.4 in comparison to 24.8 and 44.2 in untreated polyester net and no net villages respectively. In surveys carried out after three years of initial distribution, 78.7% (737/936) nets were still in possession with the households, of which 68% were used every night. An. culicifacies mortality was >80% in cone bioassays done on LNs washed up to 20 times in laboratory. Mean alpha-cypermethrin content was 43.5 ± 31.7 mg/m² on Interceptor LNs withdrawn after three years of household use against the baseline specification of 200 mg/m². A gradual increase in the proportion of holed nets was observed with the increased period of usage.

CONCLUSION

Interceptor nets were highly effective in reducing vector densities as well as malaria incidence in the study villages. Availability of 78% nets with the households in usable condition clearly indicated durability of Interceptor LNs up to three years in the rural setting of India. The nets were found to contain an effective concentration of alpha-cypermethrin against malaria vector after three years of household use.

Mutant pfcrt "SVMNT" haplotype and wild type pfmdr1 "N86" are endemic in Plasmodium vivax dominated areas of India under high chloroquine exposure

Background

Chloroquine resistance (CQR) phenotype in Plasmodium falciparum is associated with mutations in pfcrt and pfmdr-1 genes. Mutations at amino acid position 72-76 of pfcrt gene, here defined as pfcrt haplotype are associated with the geographic origin of chloroquine resistant parasite. Here, mutations at 72-76 and codon 220 of pfcrt gene and N86Y pfmdr-1 mutation were studied in blood samples collected across 11 field sites, inclusive of high and low P. falciparum prevalent areas in India. Any probable correlation between these mutations and clinical outcome of CQ treatment was also investigated.

Methods

Finger pricked blood spotted on Whatman No.3 papers were collected from falciparum malaria patients of high and low P. falciparum prevalent areas. For pfcrt haplotype investigation, the parasite DNA was extracted from blood samples and used for PCR amplification, followed by partial sequencing of the pfcrt gene. For pfmdr-1 N86Y mutation, the PCR product was subjected to restriction digestion with AflIII endonuclease enzyme.

Results

In 240 P. falciparum isolates with reported in vivo CQ therapeutic efficacy, the analysis of mutations in pfcrt gene shows that mutant SVMNT-S (67.50%) and CVIET-S (23.75%) occurred irrespective of clinical outcome and wild type CVMNK-A (7.91%) occurred only in adequate clinical and parasitological response samples. Of 287 P. falciparum isolates, SVMNTS 192 (66.89%) prevailed in all study sites and showed almost monomorphic existence (98.42% isolates) in low P. falciparum prevalent areas. However, CVIETS-S (19.51%) and CVMNK-A (11.84%) occurrence was limited to high P. falciparum prevalent areas. Investigation of pfmdr-1 N86Y mutation shows no correlation with clinical outcomes. The wild type N86 was prevalent in all the low P. falciparum prevalent areas (94.48%). However, mutant N86Y was comparably higher in numbers at the high P. falciparum prevalent areas (42.76%).

Conclusions

The wild type pfcrt gene is linked to chloroquine sensitivity; however, presence of mutation cannot explain the therapeutic efficacy of CQ in the current scenario of chloroquine resistance. The monomorphic existence of mutant SVMNT haplotype, infer inbreeding and faster spread of CQR parasite in areas with higher P. vivax prevalance and chloroquine exposure, whereas, diversity is maintained in pfcrt gene at high P. falciparum prevalent areas.

Plasmodium vivax lineages: geographical distribution, tandem repeat polymorphism, and phylogenetic relationship

Background

Multi-drug resistance and severe/complicated cases are the emerging phenotypes of vivax malaria, which may deteriorate current anti-malarial control measures. The emergence of these phenotypes could be associated with either of the two Plasmodium vivax lineages. The two lineages had been categorized as Old World and New World, based on geographical sub-division and genetic and phenotypical markers. This study revisited the lineage hypothesis of P. vivax by typing the distribution of lineages among global isolates and evaluated their genetic relatedness using a panel of new mini-satellite markers.

Methods

18S SSU rRNA S-type gene was amplified from 420 Plasmodium vivax field isolates collected from different geographical regions of India, Thailand and Colombia as well as four strains each of P. vivax originating from Nicaragua, Panama, Thailand (Pak Chang), and Vietnam (ONG). A mini-satellite marker panel was then developed to understand the population genetic parameters and tested on a sample subset of both lineages.

Results

18S SSU rRNA S-type gene typing revealed the distribution of both lineages (Old World and New World) in all geographical regions. However, distribution of Plasmodium vivax lineages was highly variable in every geographical region. The lack of geographical sub-division between lineages suggests that both lineages are globally distributed. Ten mini-satellites were scanned from the P. vivax genome sequence; these tandem repeats were located in eight of the chromosomes. Mini-satellites revealed substantial allelic diversity (7-21, AE = 14.6 ± 2.0) and heterozygosity (He = 0.697-0.924, AE = 0.857 ± 0.033) per locus. Mini-satellite comparison between the two lineages revealed high but similar pattern of genetic diversity, allele frequency, and high degree of allele sharing. A Neighbour-Joining phylogenetic tree derived from genetic distance data obtained from ten mini-satellites also placed both lineages together in every cluster.

Conclusions

The global lineage distribution, lack of genetic distance, similar pattern of genetic diversity, and allele sharing strongly suggested that both lineages are a single species and thus new emerging phenotypes associated with vivax malaria could not be clearly classified as belonging to a particular lineage on basis of their geographical origin.

Chlorfenapyr: a new insecticide with novel mode of action can control pyrethroid resistant malaria vectors

BACKGROUND

Malaria vectors have acquired widespread resistance to many of the currently used insecticides, including synthetic pyrethroids. Hence, there is an urgent need to develop alternative insecticides for effective management of insecticide resistance in malaria vectors. In the present study, chlorfenapyr was evaluated against Anopheles culicifacies and Anopheles stephensi for its possible use in vector control.

METHODS

Efficacy of chlorfenapyr against An. culicifacies and An. stephensi was assessed using adult bioassay tests. In the laboratory, determination of diagnostic dose, assessment of residual activity on different substrates, cross-resistance pattern with different insecticides and potentiation studies using piperonyl butoxide were undertaken by following standard procedures. Potential cross-resistance patterns were assessed on field populations of An. culicifacies.

RESULTS

A dose of 5.0% chlorfenapyr was determined as the diagnostic concentration for assessing susceptibility applying the WHO tube test method in anopheline mosquitoes with 2 h exposure and 48 h holding period. The DDT-resistant/malathion-deltamethrin-susceptible strain of An. culicifacies species C showed higher LD50 and LD99 (0.67 and 2.39% respectively) values than the DDT-malathion-deltamethrin susceptible An. culicifacies species A (0.41 and 2.0% respectively) and An. stephensi strains (0.43 and 2.13% respectively) and there was no statistically significant difference in mortalities among the three mosquito species tested (p > 0.05). Residual activity of chlorfenapyr a.i. of 400 mg/m2 on five fabricated substrates, namely wood, mud, mud+lime, cement and cement + distemper was found to be effective up to 24 weeks against An. culicifacies and up to 34 weeks against An. stephensi. No cross-resistance to DDT, malathion, bendiocarb and deltamethrin was observed with chlorfenapyr in laboratory-reared strains of An. stephensi and field-caught An. culicifacies. Potentiation studies demonstrated the antagonistic effect of PBO.

CONCLUSION

Laboratory studies with susceptible and resistant strains of An. culicifacies and An. stephensi, coupled with limited field studies with multiple insecticide-resistant An. culicifacies have shown that chlorfenapyr can be a suitable insecticide for malaria vector control, in multiple-insecticide-resistant mosquitoes especially in areas with pyrethroid resistant mosquitoes.

Presence of two alternative kdr-like mutations, L1014F and L1014S, and a novel mutation, V1010L, in the voltage gated Na+ channel of Anopheles culicifacies from Orissa, India

Background

Knockdown resistance in insects resulting from mutation(s) in the voltage gated Na⁺ channel (VGSC) is one of the mechanisms of resistance against DDT and pyrethroids. Recently a point mutation leading to Leu-to-Phe substitution in the VGSC at residue 1014, a most common kdr mutation in insects, was reported in Anopheles culicifacies-a major malaria vector in the Indian subcontinent. This study reports the presence of two additional amino acid substitutions in the VGSC of an An. culicifacies population from Malkangiri district of Orissa, India.

Methods

Anopheles culicifacies sensu lato (s.l.) samples, collected from a population of Malkangiri district of Orissa (India), were sequenced for part of the second transmembrane segment of VGSC and analyzed for the presence of non-synonymous mutations. A new primer introduced restriction analysis-PCR (PIRA-PCR) was developed for the detection of the new mutation L1014S. The An. culicifacies population was genotyped for the presence of L1014F substitution by an amplification refractory mutation system (ARMS) and for L1014S substitutions by using a new PIRA-PCR developed in this study. The results were validated through DNA sequencing.

Results

DNA sequencing of An. culicifacies individuals collected from district Malkangiri revealed the presence of three amino acid substitutions in the IIS6 transmembrane segments of VGSC, each one resulting from a single point mutation. Two alternative point mutations, 3042A>T transversion or 3041T>C transition, were found at residue L1014 leading to Leu (TTA)-to-Phe (TTT) or -Ser (TCA) changes, respectively. A third and novel substitution, Val (GTG)-to-Leu (TTG or CTG), was identified at residue V1010 resulting from either of the two transversions–3028G>T or 3028G>C. The L1014S substitution co-existed with V1010L in all the samples analyzed irrespective of the type of point mutation associated with the latter. The PIRA-PCR strategy developed for the identification of the new mutation L1014S was found specific as evident from DNA sequencing results of respective samples. Since L1014S was found tightly linked to V1010L, no separate assay was developed for the latter mutation. Screening of population using PIRA-PCR assays for 1014S and ARMS for 1014F alleles revealed the presence of all the three amino acid substitutions in low frequency.

Conclusions

This is the first report of the presence of L1014S (homologous to the kdr-e in An. gambiae) and a novel mutation V1010L (resulting from G-to-T or -C transversions) in the VGSC of An. culicifacies in addition to the previously described mutation L1014F. The V1010L substitution was tightly linked to L1014S substitution. A new PIRA-PCR strategy was developed for the detection of L1014S mutation and the linked V1010L mutation.

Polymorphisms of TNF-enhancer and gene for FcgammaRIIa correlate with the severity of falciparum malaria in the ethnically diverse Indian population

BACKGROUND

Susceptibility/resistance to Plasmodium falciparum malaria has been correlated with polymorphisms in more than 30 human genes with most association analyses having been carried out on patients from Africa and south-east Asia. The aim of this study was to examine the possible contribution of genetic variants in the TNF and FCGR2A genes in determining severity/resistance to P. falciparum malaria in Indian subjects.

METHODS

Allelic frequency distribution in populations across India was first determined by typing genetic variants of the TNF enhancer and the FCGR2A G/A SNP in 1871 individuals from 55 populations. Genotyping was carried out by DNA sequencing, single base extension (SNaPshot), and DNA mass array (Sequenom). Plasma TNF was determined by ELISA. Comparison of datasets was carried out by Kruskal-Wallis and Mann-Whitney tests. Haplotypes and LD plots were generated by PHASE and Haploview, respectively. Odds ratio (OR) for risk assessment was calculated using EpiInfotrade mark version 3.4.

RESULTS

A novel single nucleotide polymorphism (SNP) at position -76 was identified in the TNF enhancer along with other reported variants. Five TNF enhancer SNPs and the FCGR2A R131H (G/A) SNP were analyzed for association with severity of P. falciparum malaria in a malaria-endemic and a non-endemic region of India in a case-control study with ethnically-matched controls enrolled from both regions. TNF -1031C and -863A alleles as well as homozygotes for the TNF enhancer haplotype CACGG (-1031T>C, -863C>A, -857C>T, -308G>A, -238G>A) correlated with enhanced plasma TNF levels in both patients and controls. Significantly higher TNF levels were observed in patients with severe malaria. Minor alleles of -1031 and -863 SNPs were associated with increased susceptibility to severe malaria. The high-affinity IgG2 binding FcgammaRIIa AA (131H) genotype was significantly associated with protection from disease manifestation, with stronger association observed in the malaria non-endemic region. These results represent the first genetic analysis of the two immune regulatory molecules in the context of P. falciparum severity/resistance in the Indian population.

CONCLUSION

Association of specific TNF and FCGR2A SNPs with cytokine levels and disease severity/resistance was indicated in patients from areas with differential disease endemicity. The data emphasizes the need for addressing the contribution of human genetic factors in malaria in the context of disease epidemiology and population genetic substructure within India.

Persistence and wash-resistance of insecticidal efficacy of nettings treated with deltamethrin tablet formulation (K-O TAB) against malaria vectors

Persistence, wash-resistance, and shelf life of mosquito nets treated with a water-dispersible tablet formulation of synthetic pyrethroid insecticide deltamethrin (K-O TAB) at 25 mg/m2 was evaluated against malaria vectors in India. During June 2001, treated and untreated polyester, nylon, and cotton nets were separately distributed in 3 villages and cone bioassays were performed on Anopheles culicifacies and An. stephensi 1 day after treatment and thereafter every month for 12 months. The mosquitoes were exposed for 3 min on the nettings (treated and unwashed, or treated and washed once or twice in 3 months, and untreated) and knock-down (1 h) and 24 h postexposure mortality were recorded. Unwashed polyester nets, and those washed once 1 month after treatment, gave 100% mortality in An. culicifacies for 6 months. A 2nd wash at 3 months after treatment marginally reduced the insecticidal action. Anopheles stephensi was fully susceptible up to 4 months when exposed to unwashed nets but washing considerably reduced insecticidal action (65-78% after 2 washes). Treated nylon and cotton nets were effective for 4 months on both vectors. Treated nets kept on shelf retained 100% efficacy for 10 months. Overall, the treated nets gave a considerably long persistence of insecticidal action even after a single wash. Treated polyester nets were found most effective. Compared with our earlier experiences of using liquid formulations, the tablet formulation is likely to have a better community acceptance in treating nets.

Field evaluation of biolarvicides in Surat city, India

BACKGROUND & OBJECTIVES

Two bacterial larvicide (bio-larvicide) formulations--Bacticide and VectoBac containing viable endospores and delta endotoxin of Bacillus thuringiensis var israelensis H-14 were evaluated in 2001 for their mosquito larvicidal efficacy under the operational conditions of urban malaria control programme in Surat city, India.

METHODS

Larvicides were applied at the recommended dose in selected breeding habitats of Anopheles (An. stephensi), Aedes (Ae. aegypti) and Culex (Cx. quinquefasciatus) and reductions in the densities of III and IV instars were compared with that of untreated matched controls.

RESULTS

At the construction sites in cemented tanks/chambers VectoBac produced reduction in the density of III and IV instar larvae of An. stephensi (98-100%) and Ae. aegypti (100%) in the first week of application whereas Bacticide produced 71-100% reduction in An. stephensi and 100% in Ae. aegypti. Re-application of VectoBac on Day 10 caused better control up to Day 20 when compared with Bacticide. In stagnant water pools, VectoBac produced 27.6-85.3% reduction in the larvae of An. subpictus and 18.5-83.8% in those of Cx. quinquefasciatus whereas Bacticide produced 23.3-30.3% and 39-97.2% reduction in An. subpictus and Cx. quinquefasciatus larval densities in the first week post application, respectively. Bacticide application gave better impact on Cx. quinquefasciatus larvae in the second week after re-application as compared to VectoBac. In storm water drains, VectoBac caused respectively 6.2-100% and 6.4-97.6% reduction in An. subpictus and Cx. quinquefasciatus larvae in the first week of application whereas Bacticide produced 100% and 13.3-98.8% reduction in An. subpictus and Cx. quinquefasciatus larval densities, respectively.

INTERPRETATION & CONCLUSION

Both the formulations were equally effective on An. subpictus and Cx. quinquefasciatus larvae after a second application. The results showed that application of these biolarvicides would be required at 7-10 day intervals. The health workers engaged in the application of biolarvicides reported a better ease of handling and application of the liquid formulation (VectoBac) than the wettable powder formulation (Bacticide).

The burden of malaria in Ahmedabad city, India: a retrospective analysis of reported cases and deaths

Owing to the paucity of accurate information on the burden of malaria in urban India, a retrospective, epidemiological study was carried out in Ahmedabad city, which has a population of about 3 million. Surveillance data for the years 1965-1998 showed a gradual resurgence of malaria between 1967 to 1976, followed by waves of low and high incidences. Plasmodium vivax always predominated but the proportion of cases attributed to P. falciparum increased markedly from 1983. When the surveillance data and health records of the major public and private health facilities in the city were analysed, for the period between 1991 and 1998, P. vivax was found to account for 69% of all malaria cases and P. falciparum for the other 31%. The incidence of infection with each Plasmodium species showed seasonal variation, with that of P. vivax increasing from January to September but then declining as the incidence of P. falciparum increased. The age-specific differences seen in incidence were not statistically significant (P=0.7). The annual numbers of malaria-attributable deaths were strongly correlated with the incidence of P. falciparum (r=0.88). The malaria incidence detected (37431 cases, representing a mean annual incidence of 12.2 cases/1000) was nine times greater than that officially reported (4119 cases, or 1.3 cases/1000 each year). Similarly, the annual malaria-attributable mortality detected (22 deaths/million) was far higher than that officially notified (0.3 death/million). The results of the retrospective analysis not only provide a more accurate, baseline estimate of the burden of malaria in an urban area of India but also clearly indicate the need for a much more efficient health-information system, for recording and managing malaria in such a setting.

Biting rhythms of some anophelines in central Gujarat

A total of 41,552 anophelines comprising 16 species were collected during 70 all-night bovine-bait collection carried out in six villages of Kheda district, Gujarat. Anopheles subpictus, An. varuna, An. culicifacies, An. stephensi and An. vagus had unimodal biting rhythms. Most feeding occurred during the early night with occasional increase during pre-dawn/dawn hours. An. pallidus exhibited bimodal biting rhythm with two well-defined peaks. An. turkhudi, An. tessellatus, An. fluviatilis, An. aconitus, An. annularis; An. barbirostris and An. nigerrimus had multimodal biting rhythms or were arthymic. An. culicifacies, An. varuna, An. aconitus and An. tessellatus exhibited a marked seasonal shift in feeding activities with most biting occurring at dusk in colder months and late at night during warmer months.

Studies on Plasmodium vivax relapse pattern in Kheda district, Gujarat

Relapse pattern in P. vivax malaria was studied in five villages of Nadiad taluka, Kheda district, Gujarat. P. vivax cases treated with 600 mg chloroquine and in combination with 50 mg pyrimethamine (adult dose) yielded 28.31 and 27.73% relapse rate respectively. While relapse rate of 5.78% was observed with five day course of 75 mg primaquine (15 mg/day) administered as radical treatment. Relapse rate in 5-10 yr of age group was comparatively more than other age groups. There was no noticeable difference in relapse rates among male and female. The short-term relapse with a lag period of 2-3 months was significantly higher in this area. The longest relapse with an interval of 17 months was found in one case treated with chloroquine along with pyrimethamine. However, primaquine regimen prevented consecutive relapses. Primaquine has been found adequate to prevent relapse in more than 90% vivax cases, while efficacy of chloroquine-pyrimethamine and chloroquine alone was almost comparable. A high proportion of relapse may be minimized, if 5-days radical treatment is given at appropriate time.

Activity of a crude extract formulation in experimental hepatic amoebiasis and in immunomodulation studies

The activity of a crude extract formulation was evaluated in experimental amoebic liver abscess in golden hamsters and in immunomodulation studies. The formulation comprises the following five plants-Boerhavia diffusa, Tinospora cordifolia, Berberis aristata, Terminalia chebula and Zingiber officinale. The formulation had a maximum cure rate of 73% at a dose of 800 mg/kg/day in hepatic amoebiasis reducing the average degree of infection (ADI) to 1.3 as compared to 4.2 for sham-treated controls. In immunomodulation studies humoral immunity was enhanced as evidenced by the haemagglutination titre. The T-cell counts remained unaffected in the animals treated with the formulation but cell-mediated immune response was stimulated as observed in the leukocyte migration inhibition (LMI) tests.

Epidemiological observations on malaria in villages of Buhari PHC, Surat, Gujarat

Investigations were carried out in the villages of Buhari PHC, Surat district, Gujarat to determine factors responsible for high prevalence of P. falciparum. The area is well-known for sugarcane cultivation, industrialization and frequent movement of labourers. The slide positivity rate (44.24%) and P. falciparum infections (95.37%) were significantly high. The children of 5-9 yrs of age group suffered maximum from malaria. The infection in children was found associated with splenomegaly also. High falciparum infection (82.35%) was found in labourers camping near villages out of which 90% afebrile cases were reported which were silent carriers and source of transmission. Chloroquine was effective in 75% cases despite of existence of resistant falciparum strain. Among seven anopheline species encountered, An. culicifacies was predominant and found breeding in most of the breeding sites. The status of the insecticide spray and its receptivity among the community were poor. The investigation led to the conclusion that adequate measures are required to deal with migratory labourers, improper insecticide coverage, poor surveillance and mass ignorance.

Prophylactic therapy of Salmonella typhi septicemia in mice with a traditionally prescribed crude drug formulation

A crude drug formulation comprised of eight medicinal herb extracts was studied for in vitro and in vivo effect against Salmonella typhi. The formulation displayed inhibitory action against the test organism in vitro. Subsequently mice were challenged with a virulent strain of Salmonella typhi (Ty2) and the protective effect of the formulation was evaluated with post-infective, pre-infective, single and multiple dose schedules, administered either orally or subcutaneously. A schedule that included multiple divided doses prophylactically administered had a significant therapeutic effect.

The antiamoebic effect of a crude drug formulation of herbal extracts against Entamoeba histolytica in vitro and in vivo

The antiamoebic effect of a crude drug formulation against Entamoeba histolytica was studied. In the traditional system of medicine in India, the formulation has been prescribed for intestinal disorders. It comprises of five medicinal herbs, namely, Boerhavia diffusa, Berberis aristata, Tinospora cordifolia, Terminalia chebula and Zingiber officinale. The dried and pulverized plants were extracted in ethanol together and individually. In vitro amoebicidal activity was studied to determine the minimal inhibitory concentration (MIC) values of all the constituent extracts as well as the whole formulation. The formulation had a MIC of 1000 micrograms/ml as compared with 10 micrograms/ml for metronidazole. In experimental caecal amoebiasis in rats the formulation had a curative rate of 89% with the average degree of infection (ADI) reduced to 0.4 in a group dosed with 500 mg/kg per day as compared with ADI of 3.8 for the sham-treated control group of rats. Metronidazole had a cure rate of 89% (ADI = 0.4) at a dose of 100 mg/kg per day and cured the infection completely (ADI = 0) when the dosage was doubled to 200 mg/kg per day. There were varying degrees of inhibition of the following enzyme activities of crude extracts of axenically cultured amoebae: DNase, RNase, aldolase, alkaline phosphatase, acid phosphatase, alpha-amylase and protease.

Biology of malaria vectors in central Gujarat

Biology of malaria vectors were studied in Kheda district of central Gujarat in order to understand the vector behaviour in the wake of ecological changes. Anopheles culicifacies and An. stephensi were mainly endophilic whereas An. fluviatilis exhibited marked exophily. All the three vectors were predominantly zoophilic. Peak biting activity period of An. culicifacies varied with season though biting continued in varying magnitudes throughout the night. An. stephensi and An. fluviatilis were arhythmic in their biting activity. Survival of all the three vectors was maximum during cold season owing to longer gonotrophic cycle which also yielded higher estimates for expected infective life. Instability of malaria in this area was probably due to low estimates of expected infective life for the three vectors. A wide range of breeding habitat preferences by An. culicifacies was observed whereas An. fluviatilis and An. stephensi showed restricted distribution.

Observations on mosquito breeding in wells and its control

Studies on mosquito breeding in wells revealed the dominance of An. stephensi among the malaria vectors, whereas Cx. quinquefasciatus was most abundant in disused wells and was present in wells of all depths. None of the anopheline species was encountered when well depth up to water level exceeded 12 m. Larval breeding was effectively controlled through the introduction of larvivorous fish Poecilia reticulata and expanded polystyrene (EPS) beads in comparison to untreated control wells.

Primary benign vesical teratoma. A case report

Primary benign vesical teratomas are rare. Most of the cases reported are paravesical teratomas rupturing into the bladder. A case of primary benign vesical teratoma suspected preoperatively and later confirmed at histopathology is reported.

An epidemiological study of G-6-PD deficiency, sickle cell haemoglobin, and ABO blood groups in relation to malaria incidence in Muslim and Christian communities of Kheda, Gujarat, (India)

783 blood samples for the study of distribution of ABO blood groups and sickle cell haemoglobin in relation to malaria, from both the sexes of Muslim and Christian populations of Kheda district were screened. 414 blood samples from male individuals were screened for G-6-PD deficiency. High frequency of G-6-PD deficiency was observed in Christians (5.9%) and low in Muslim (1.8%) population, whereas sickle cell haemoglobin in Muslim population was 1.5% and absent in Christians. Blood group B was dominant in both the communities. Significant association of ABO polymorphs with P. falciparum and total malaria cases was observed.

Frequency of ABO blood groups, sickle-cell haemoglobin, G-6-PD deficiency and their relation with malaria in scheduled castes and scheduled tribes of Kheda District, Gujarat

Frequency of sickle cell in Scheduled Caste and Scheduled Tribe populations was found to be 1.5 and 14.9% respectively, whereas G-6-PD deficiency was 5.9 and 4.2% respectively. Blood group B was dominant in both the communities. A significantly lower frequency of P. falciparum malaria was observed among sicklers.

Sensitivity of mosquito-pathogenic bacterial strains to various antibodies

Four strains of Bacillus sphaericus, 1593, 2362, 9001 and 9002, B. thuringiensis H-14 and B. thuringiensis neoleonensis were tested for sensitivity against 18 antibiotics. The results revealed that all the four strains of B. sphaericus are resistant to colistin, nalidixic acid, polymyxin B and streptomycin. However, B. thuringiensis H-14 was resistant to 9 antibiotics, viz. ampicillin, cephalexin, carbenicillin, co-trimoxazole, colistin, cloxacillin, penicillin, nitrofurantoin and polymyxin B whereas B. thuringiensis neoleonensis was found to be resistant to 8 antibiotics. These results may help in isolation of potential and resistant mosquito pathogenic bacteria.

Microscopic diagnosis of malaria in Kheda district of Gujarat

A study conducted in 1990 revealed that 2% (range 0.6-4.8) of negative blood smears were mislabelled as positive, and 6.7% of positive blood smears were mislabelled as negative. A result of such mislabelling would be inadequate treatment of a large number of patients. Hence the need to look into the training aspect and system of supervision of laboratory technicians. The present system of cross-checking of blood smears at different levels also needs to be reviewed. A study which could address itself to these needs is indicated.

Intradomestic mosquito breeding sources and their management

Seven mosquito species were found to breed in intradomestic breeding sources. An. stephensi and An. subpictus bred in almost all types of containers. Among the culicines, Cx. quinquefasciatus and Ae. aegypti were predominant. Larval breeding was controlled through source reduction or introduction of larvivorous fish Poecilia reticulata. Health education helped in acceptance of the programme by the community. Intradomestic breeding positivity was 2-6% and 16-31% in experimental and control areas respectively.

Gujarat model of health management information system with reference to malaria

The Gujarat model of health management and information system has been developed with the objective of reducing the work load of health workers at all levels pertaining to record keeping and report preparation for enhancing the quality of health services, as well as for better implementation and timely monitoring of health programmes. Pro formas currently in use under various health programmes have been reorganized and updated. For monitoring malaria, the total number of registers has been reduced from seven to one, reporting forms from 23 to six and the number of columns in reporting forms from 493 to 59. The model is expected to save the working time of laboratory technicians (15%) and multi-purpose health supervisors (5%) at PHC level and of all workers (100%) engaged in report preparation at district, state and national levels. The data generated by using this model are expected to be of high quality and accuracy and should lead to more rational planning.

Isolation and laboratory evaluation of an indigenous strain of Bacillus sphaericus (9001)

An indigenous strain of Bacillus sphaericus H5a (9001), possessing high insecticidal properties, was isolated from diseased larvae of Culex species. This strain in comparison with the known strains of B. sphaericus, i.e., 1593 and 2362, was found to be promising against the fourth instar larvae of Anopheles culicifacies, An. stephensi, An. subpictus, Aedes aegypti and Culex quinquefasciatus. B. sphaericus 9001 is highly stable and virulent through 25 successive transfers and thus can be effectively used as a biocontrol agent against immature stages of mosquitoes.

Biting rhythms of malaria vector Anopheles culicifacies in Kheda district, Gujarat

All night collections on bovine baits were made in 6 villages of Kheda district, Gujarat. During 70 all night bait collections from January to December 1989, a total of 2290 An. culicifacies were collected. An. culicifacies mostly exhibited bimodal rhythms with a seasonal shift in peak biting activities. During the cold season most biting occurred just after dusk and during the warm season late at night. An. culicifacies was more active during moonless hours and its activity showed no correlation with temperature and humidity during most part of the year.

A quantitative survey of anophelines in six villages of Kheda District, Gujarat

Sampling of anophelines from six villages of Kheda district, Gujarat was done using four different methods viz. indoor resting, outdoor resting, bovine bait trap and immature collections. A total of 113,487 specimens representing 17 species were collected. An. subpictus (66.51 per cent) was most abundant species followed by An. culicifacies (14.12 per cent) and An. tessellatus (5.24 per cent). Bovine bait collections were found most productive yielding maximum species and highest number of anophelines per unit of collection efforts. Indoor resting collections yielded poorest diversity and greater number of specimens per unit of collection effort than outdoor resting collections. Maximum diversity was observed in outdoor collections. Most of the species exhibited unimodal prevalence.

Seasonal prevalence of anophelines in Kheda district, Gujarat

Seasonal changes in the population structure of anophelines were studied in Kheda district, Gujarat. Mosquito collections were made from the villages of Nadiad taluka, representing 3 different physiographic zones. Maximum number of anopheline species (13) were recorded from canal irrigated area followed by 11 species from non-canal irrigated and 8 species from riverine areas. Four anophelines namely An. subpictus, An. culicifacies, An. annularis and An. stephensi were predominant. High densities of An. culicifacies and An. subpictus were recorded in March and August. Results of a four year study (1985 to 1988) on the population of anophelines from 3 different physiographic entities showed marked differences in the seasonal abundance of different species.

Interspecific associations among anophelines in different breeding habitats of Kheda district, Gujarat. Part I: Canal irrigated area

In a study covering two years, 1306 samples of immatures were collected from 7 different breeding habitats of canal irrigated villages of Kheda district in Gujarat. Out of the samples belonging to 8 anopheline species, 14396 adults emerged. Breeding of An. culicifacies was associated with An. annularis in ponds, paddy fields, small pools and with An. stephensi in paddy fields. Maximum association was observed between An. barbirostris and An. nigerrimus in irrigation canals and An. culicifacies and An. subpictus in intradomestic containers. An. annularis, An. stephensi and An. subpictus were strongly associated in paddy fields. Strong interspecific repulsion was observed between An. subpictus and An. stephensi in intradomestic containers and An. barbirostris and An. subpictus in ponds.