Genetic diversity of Plasmodium vivax in Kolkata, India

BACKGROUND: Plasmodium vivax malaria accounts for approximately 60% of malaria cases in Kolkata, India. There has been limited information on the genotypic polymorphism of P. vivax in this malaria endemic area. Three highly polymorphic and single copy genes were selected for a study of genetic diversity in Kolkata strains. METHODS: Blood from 151 patients with P. vivax infection diagnosed in Kolkata between April 2003 and September 2004 was genotyped at three polymorphic loci: the P. vivax circumsporozoite protein (pvcs), the merozoite surface protein 1 (pvmsp1) and the merozoite surface protein 3-alpha (pvmsp3-alpha). RESULTS: Analysis of these three genetic markers revealed that P. vivax populations in Kolkata are highly diverse. A large number of distinguishable alleles were found from three genetic markers: 11 for pvcs, 35 for pvmsp1 and 37 for pvmsp3-alpha. These were, in general, randomly distributed amongst the isolates. Among the 151 isolates, 142 unique genotypes were detected the commonest genotype at a frequency of less than 2% (3/151). The overall rate of mixed genotype infections was 10.6%. CONCLUSION: These results indicate that the P. vivax parasite population is highly diverse in Kolkata, despite the low level of transmission. The genotyping protocols used in this study may be useful for differentiating re-infection from relapse and recrudescence in studies assessing of malarial drug efficacy in vivax malaria

Prevalence of kdr mutations and insecticide susceptibility among natural population of Aedes aegypti in West Bengal.

BackgroundAedes albopictus and Aedes aegypti are the major vectors of arboviral diseases. As effective vaccines are not available for most of the arboviral diseases, vector control by using insecticides play the key role to reduce the disease transmission. The emergence and spread of resistance to different classes of insecticides by the vectors is a major obstacle to control the disease transmission. Information about vector susceptibility to different insecticides and their mechanisms are very important for formulating proper vector control measures. The present study was designed to assess the susceptibility of Ae. aegypti against three different classes of adulticides, one larvicidal agent available and polymorphisms in the voltage-gated sodium channel (VGSC) gene related to insecticide resistance.MethodsImmature stages of Ae. aegypti were collected from three dengue endemic municipal areas of West Bengal and reared in the laboratory. Larvae and adults (F1 progeny) were used for insecticide bioassay as per WHO protocols. Knock down resistance gene (kdr) mutations were assessed by direct sequencing of PCR products.ResultsThe Ae. aegypti population was found to be susceptible to type II pyrethroids and malathion but highly resistant to DDT. A high rate of polymorphisms in the VGSC gene was observed among the collected mosquitoes. A double mutant V1016G + F1534C was found to be associated with DDT resistance but neither V1016G nor F1534C alone showed the same association. Association between the kdr mutations and the susceptibility status of pyrethroids could not be established due to very small sample size. A low to moderate level of resistance was noticed against temephos among the larval population based on WHO criteria.ConclusionThe replacement of DDT by type II pyrethroids for the management of dengue vectors is an appropriate decision taken by the national program which is supported by the findings of a higher level of resistance to DDT. Persistence of polymorphisms in the VGSC gene might be an indication of emergence of resistance against pyrethroid insecticides that should be monitored at a regular interval. Attempts should be made to determine the effectiveness of other larvicides for replacement of temephos if needed in future. Along with the chemical insecticides different biological vector control methods as well as biopesticides should also be used in vector control programmes

Challenges for maintaining post elimination phase of visceral leishmaniasis control programme in India: A field-based study.

BackgroundIndia is going through the maintenance phase of VL elimination programme which may be threatened by the persistence of hidden parasite pools among asymptomatic leishmanial infection (ALI) and PKDL. The present work was designed to determine the burden of VL, PKDL, and ALI and to assess the role of treatment of ALI in maintaining post-elimination phase.Methods and findingThe study was undertaken in Malda district, West Bengal, India during October 2016 to September 2021. Study areas were divided into 'Study' and 'Control' arms. VL and PKDL cases of both the arms were diagnosed by three active mass surveys with an interval of one year and treated as per National guideline. ALI of 'Study' arm was treated like VL. ALI of 'Control' arm was followed up to determine their fate. Fed sand-fly pools were analysed for parasitic DNA. No significant difference was noted between the incidence of VL and PKDL in both the arms. Incidence of ALI declined sharply in 'Study' arm but an increasing trend was observed in 'Control' arm. Significantly higher rate of sero-conversion was noted in 'Control' arm and was found to be associated with untreated ALI burden. Parasitic DNA was detected in 22.8% ALI cases and 2.2% sand-fly pools.ConclusionPersistence of a significant number of PKDL and ALI and ongoing transmission, as evidenced by new infection and detection of leishmanial DNA in vector sand-flies, may threaten the maintenance of post-elimination phase. Emphasis should be given for elimination of pathogen to prevent resurgence of VL epidemics

Japanese encephalitis virus infection among wild caught vectors mosquitoes and domestic pigs in Northern West Bengal, India

Background: Japanese encephalitis (JE) is an emerging zoonotic disease caused by JE virus (JEV) and transmitted to humans from pigs or aquatic birds by vector mosquitoes in southeast Asian countries. In this study, JEV infection rate among vector mosquitoes and domestic pigs was determined by detecting viral RNA and anti-JEV antibody (immunoglobulin G), respectively. Materials and Methods: A total of 146 pool mosquitoes of Culex vishnui subgroup and 278 pig blood samples were analyzed by reverse transcriptase polymerase chain reaction and enzyme-linked immunosorbent assay methods, respectively. E and premembrane (PrM) gene of JEV detected among vectors were sequenced and a phylogenetic tree was constructed. Results: Five (5.81%) pools of Culex tritaeniorhynchus were positive for JEV with pooled infection rate 1.70/1000 mosquitoes. A total of 108 (38.84%) blood samples were positive for anti-JEV antibody. Phylogenetic analysis revealed that our own E and PrM gene sequence of JEV belonging to Genotype III and showed 96.95% sequence similarities with the vaccine strain SA14-14-2. Conclusion: It was observed that domestic pigs of northern West Bengal were highly infected with JEV. Hence, the transmission should be blocked by pig vaccination. A pilot study may be undertaken for mass vaccination of the prevailing pig population to observe any reduced rate of JEV transmission from both pig to pig and pig to human

Polymorphisms in voltage-gated sodium channel gene and susceptibility of <i>Aedes albopictus</i> to insecticides in three districts of northern West Bengal, India - Fig 2

<p>Survival rate of <i>Aedes albopictus</i> against 4% DDT (A), 0.05% deltamethrin (B), 5% malathion (C) in West Bengal.</p

No Polymorphism in Plasmodium falciparum K13 Propeller Gene in Clinical Isolates from Kolkata, India

Molecular markers associated with artemisinin resistance in Plasmodium falciparum are yet to be well defined. Recent studies showed that polymorphisms in K13 gene are associated with artemisinin resistance. The present study was designed to know the pattern of polymorphisms in propeller region of K13 gene among the clinical isolates collected from urban Kolkata after five years of ACT implementation. We collected 59 clinical isolates from urban Kolkata and sequenced propeller region of K13 gene in 51 isolates successfully. We did not find any mutation in any isolate. All patients responded to the ACT, a combination of artesunate + sulphadoxine-pyrimethamine. The drug regimen is still effective in the study area and there is no sign of emergence of resistance against artemisinin as evidenced by wild genotype of K13 gene in all isolates studied

Primer and PCR conditions used for amplification and sequencing of <i>VGCS</i> gene of <i>Aedes albopictus</i> (Kasai <i>et al</i>., 2011).

<p>Primer and PCR conditions used for amplification and sequencing of <i>VGCS</i> gene of <i>Aedes albopictus</i> (Kasai <i>et al</i>., 2011).</p

Map showing the study sites.

<p>Map showing the study sites.</p

Insecticide susceptibility status of <i>Aedes albopictus</i> against 4% DDT, 0.05% deltamethrin, and 5% malathion in West Bengal.

<p>Insecticide susceptibility status of <i>Aedes albopictus</i> against 4% DDT, 0.05% deltamethrin, and 5% malathion in West Bengal.</p

PKDL--A Silent Parasite Pool for Transmission of Leishmaniasis in Kala-azar Endemic Areas of Malda District, West Bengal, India.

Post Kala-azar Dermal Leishmaniasis (PKDL) is a chronic but not life-threatening disease; patients generally do not demand treatment, deserve much more attention because PKDL is highly relevant in the context of Visceral Leishmaniasis (VL) elimination. There is no standard guideline for diagnosis and treatment for PKDL. A species-specific PCR on slit skin smear demonstrated a sensitivity of 93.8%, but it has not been applied for routine diagnostic purpose. The study was conducted to determine the actual disease burden in an endemic area of Malda district, West Bengal, comparison of the three diagnostic tools for PKDL case detection and pattern of lesion regression after treatment. The prevalence of PKDL was determined by active surveillance and confirmed by PCR based diagnosis. Patients were treated with either sodium stibogluconate (SSG) or oral miltefosine and followed up for two years to observe lesion regression period. Twenty six PKDL cases were detected with a prevalence rate of 27.5% among the antileishmanial antibody positive cases. Among three diagnostic methods used, PCR is highly sensitive (88.46%) for case confirmation. In majority of the cases skin lesions persisted after treatment completion which gradually disappeared during 6-12 months post treatment period. Reappearance of lesions noted in two cases after 1.5 years of miltefosine treatment. A significant number of PKDL patients would remain undiagnosed without active mass surveys. Such surveys are required in other endemic areas to attain the ultimate goal of eliminating Kala-azar. PCR-based method is helpful in confirming diagnosis of PKDL, referral laboratory at district or state level can achieve it. So a well-designed study with higher number of samples is essential to establish when/whether PKDL patients are free from parasite after treatment and to determine which PKDL patients need treatment for longer period