Using the entomological inoculation rate to assess the impact of vector control on malaria parasite transmission and elimination

Prior studies have shown that annual entomological inoculation rates (EIRs) must be reduced to less than one to substantially reduce the prevalence of malaria infection. In this study, EIR values were used to quantify the impact of insecticide-treated bed nets (ITNs), indoor residual spraying (IRS), and source reduction (SR) on malaria transmission. The analysis of EIR was extended through determining whether available vector control tools can ultimately eradicate malaria. The analysis is based primarily on a review of all controlled studies that used ITN, IRS, and/or SR and reported their effects on the EIR. To compare EIRs between studies, the percent difference in EIR between the intervention and control groups was calculated. Eight vector control intervention studies that measured EIR were found: four ITN studies, one IRS study, one SR study, and two studies with separate ITN and IRS intervention groups. In both the Tanzania study and the Solomon Islands study, one community received ITNs and one received IRS. In the second year of the Tanzania study, EIR was 90% lower in the ITN community and 93% lower in the IRS community, relative to the community without intervention; the ITN and IRS effects were not significantly different. In contrast, in the Solomon Islands study, EIR was 94% lower in the ITN community and 56% lower in the IRS community. The one SR study, in Dar es Salaam, reported a lower EIR reduction (47%) than the ITN and IRS studies. All of these vector control interventions reduced EIR, but none reduced it to zero. These studies indicate that current vector control methods alone cannot ultimately eradicate malaria because no intervention sustained an annual EIR less than one. While researchers develop new tools, integrated vector management may make the greatest impact on malaria transmission. There are many gaps in the entomological malaria literature and recommendations for future research are provided

Inhibition of Monkeypox virus replication by RNA interference

The Orthopoxvirus genus of Poxviridae family is comprised of several human pathogens, including cowpox (CPXV), Vaccinia (VACV), monkeypox (MPV) and Variola (VARV) viruses. Species of this virus genus cause human diseases with various severities and outcome ranging from mild conditions to death in fulminating cases. Currently, vaccination is the only protective measure against infection with these viruses and no licensed antiviral drug therapy is available. In this study, we investigated the potential of RNA interference pathway (RNAi) as a therapeutic approach for orthopox virus infections using MPV as a model. Based on genome-wide expression studies and bioinformatic analysis, we selected 12 viral genes and targeted them by small interference RNA (siRNA). Forty-eight siRNA constructs were developed and evaluated in vitro for their ability to inhibit viral replication. Two genes, each targeted with four different siRNA constructs in one pool, were limiting to viral replication. Seven siRNA constructs from these two pools, targeting either an essential gene for viral replication (A6R) or an important gene in viral entry (E8L), inhibited viral replication in cell culture by 65-95% with no apparent cytotoxicity. Further analysis with wild-type and recombinant MPV expressing green fluorescence protein demonstrated that one of these constructs, siA6-a, was the most potent and inhibited viral replication for up to 7 days at a concentration of 10 nM. These results emphasis the essential role of A6R gene in viral replication, and demonstrate the potential of RNAi as a therapeutic approach for developing oligonucleotide-based drug therapy for MPV and other orthopox viruses

Identification of pyrimethamine- and chloroquine-resistant Plasmodium falciparum in Africa between 1984 and 1998: genotyping of archive blood samples

<p>Abstract</p> <p>Background</p> <p>Understanding the geographical distribution of drug resistance of <it>Plasmodium falciparum </it>is important for the effective treatment of malaria. Drug resistance has previously been inferred mainly from records of clinical resistance. However, clinical resistance is not always consistent with the parasite's genetic resistance. Thus, molecular identification of the parasite's drug resistance is required. In Africa, clinical resistance to pyrimethamine (Pyr) and chloroquine (CQ) was evident before 1980 but few studies investigating the genetic resistance to these drugs were conducted before the late 1990s. In this study, genotyping of genes involved in resistance to Pyr and CQ was performed using archive blood samples from Africa between 1984 and 1998.</p> <p>Methods</p> <p>Parasite DNA was extracted from <it>P. falciparum</it>-infected blood smears collected from travellers returning to Japan from Africa between 1984 and 1998. Genotypes of the dihydrofolate reductase gene (<it>dhfr</it>) and CQ-resistance transporter gene (<it>pfcrt) </it>were determined by polymerase chain reaction amplification and sequencing.</p> <p>Results</p> <p>Genotyping of <it>dhfr </it>and <it>pfcrt </it>was successful in 59 and 80 samples, respectively. One wild-type and seven mutant <it>dhfr </it>genotypes were identified. Three <it>dhfr </it>genotypes lacking the S108N mutation (NRSI, ICSI, IRSI; amino acids at positions 51, 59, 108, and 164 with mutations underlined) were highly prevalent before 1994 but reduced after 1995, accompanied by an increase in genotypes with the S108N mutation. The <it>dhfr </it>IRNI genotype was first identified in Nigeria in 1991 in the present samples, and its frequency gradually increased. However, two double mutants (ICNI and NRNI), the latter of which was exclusively found in West Africa, were more frequent than the IRNI genotype. Only two <it>pfcrt </it>genotypes were found, the wild-type and a Southeast Asian type (CVIET; amino acids at positions 72-76 with mutations underlined). The CVIET genotype was already present as early as 1984 in Tanzania and Nigeria, and appeared throughout Africa between 1984 and 1998.</p> <p>Conclusions</p> <p>This study is the first to report the molecular identification of Pyr- and CQ-resistant genotypes of <it>P. falciparum </it>in Africa before 1990. Genotyping of <it>dhfr </it>and <it>pfcrt </it>using archive samples has revealed new aspects of the evolutionary history of Pyr- and CQ-resistant parasites in Africa.</p

Malaria vectors and transmission dynamics in Goulmoun, a rural city in south-western Chad

<p>Abstract</p> <p>Background</p> <p>Knowledge of some baseline entomological data such as Entomological Inoculation Rates (EIR) is crucially needed to assess the epidemiological impact of malaria control activities directed either against parasites or vectors. In Chad, most published surveys date back to the 1960's. In this study, anopheline species composition and their relation to malaria transmission were investigated in a dry Sudanian savannas area of Chad.</p> <p>Methods</p> <p>A 12-month longitudinal survey was conducted in the irrigated rice-fields area of Goulmoun in south western Chad. Human landing catches were performed each month from July 2006 to June 2007 in three compounds (indoors and outdoors) and pyrethrum spray collections were conducted in July, August and October 2006 in 10 randomly selected rooms. Mosquitoes belonging to the <it>Anopheles gambiae </it>complex and to the <it>An. funestus </it>group were identified by molecular diagnostic tools. <it>Plasmodium falciparum </it>infection and blood meal sources were detected by ELISA.</p> <p>Results</p> <p>Nine anopheline species were collected by the two sampling methods. The most aggressive species were <it>An. arabiensis </it>(51 bites/human/night), <it>An. pharoensis </it>(12.5 b/h/n), <it>An. funestus </it>(1.5 b/h/n) and <it>An. ziemanni </it>(1.3 b/h/n). The circumsporozoite protein rate was 1.4% for <it>An. arabiensis</it>, 1.4% for <it>An. funestus</it>, 0.8% for <it>An. pharoensis </it>and 0.5% for <it>An. ziemanni</it>. Malaria transmission is seasonal, lasting from April to December. However, more than 80% of the total EIR was concentrated in the period from August to October. The overall annual EIR was estimated at 311 bites of infected anophelines/human/year, contributed mostly by <it>An. arabiensis </it>(84.5%) and <it>An. pharoensis </it>(12.2%). <it>Anopheles funestus </it>and <it>An. ziemanni </it>played a minor role. Parasite inoculation occurred mostly after 22:00 hours but around 20% of bites of infected anophelines were distributed earlier in the evening.</p> <p>Conclusion</p> <p>The present study revealed the implication of <it>An. pharoensis </it>in malaria transmission in the irrigated rice fields of Goulmoun, complementing the major role played by <it>An. arabiensis</it>. The transmission period did not depend upon irrigation. Correct use of insecticide treated nets in this area may be effective for vector control although additional protective measures are needed to prevent pre-bedtime exposure to the bites of infected anophelines.</p

Plants used traditionally to treat malaria in Brazil: the archives of Flora Medicinal

The archives of Flora Medicinal, an ancient pharmaceutical laboratory that supported ethnomedical research in Brazil for more than 30 years, were searched for plants with antimalarial use. Forty plant species indicated to treat malaria were described by Dr. J. Monteiro da Silva (Flora Medicinal leader) and his co-workers. Eight species, Bathysa cuspidata, Cosmos sulphureus, Cecropia hololeuca, Erisma calcaratum, Gomphrena arborescens, Musa paradisiaca, Ocotea odorifera, and Pradosia lactescens, are related as antimalarial for the first time in ethnobotanical studies. Some species, including Mikania glomerata, Melampodium divaricatum, Galipea multiflora, Aspidosperma polyneuron, and Coutarea hexandra, were reported to have activity in malaria patients under clinical observation. In the information obtained, also, there were many details about the appropriate indication of each plant. For example, some plants are indicated to increase others' potency. There are also plants that are traditionally employed for specific symptoms or conditions that often accompany malaria, such as weakness, renal failure or cerebral malaria. Many plants that have been considered to lack activity against malaria due to absence of in vitro activity against Plasmodium can have other mechanisms of action. Thus researchers should observe ethnomedical information before deciding which kind of screening should be used in the search of antimalarial drugs

Likely Correlation between Sources of Information and Acceptability of A/H1N1 Swine-Origin Influenza Virus Vaccine in Marseille, France

BACKGROUND: In France, there was a reluctance to accept vaccination against the A/H1N1 pandemic influenza virus despite government recommendation and investment in the vaccine programme. METHODS AND FINDINGS: We examined the willingness of different populations to accept A/H1N1 vaccination (i) in a French hospital among 3315 employees immunized either by in-house medical personnel or mobile teams of MDs and (ii) in a shelter housing 250 homeless persons. Google was used to assess the volume of enquiries concerning incidence of influenza. We analyzed the information on vaccination provided by Google, the website of the major French newspapers, and PubMed. Two trust Surveys were used to assess public opinion on the trustworthiness of people in different professions. Paramedics were significantly more reluctant to accept immunisation than qualified medical staff. Acceptance was significantly increased when recommended directly by MDs. Anecdotal cases of directly observed severe infections were followed by enhanced acceptance of paramedical staff. Scientific literature was significantly more in favour of vaccination than Google and French newspaper websites. In the case of the newspaper websites, information correlated with their recognised political reputations, although they would presumably claim independence from political bias. The Trust Surveys showed that politicians were highly dis-trusted in contrast with doctors and pharmacists who were considered much more trustworthy. CONCLUSIONS: The low uptake of the vaccine could reflect failure to convey high quality medical information and advice relating to the benefits of being vaccinated. We believe that the media and internet contributed to this problem by raising concerns within the general population and that failure to involve GPs in the control programme may have been a mistake. GPs are highly regarded by the public and can provide face-to-face professional advice and information. The top-down strategy of vaccine programme management and information delivered by the Ministry of Health could have aggravated the problem, because the general population does not always trust politicians

Patterns of Selection in Anti-Malarial Immune Genes in Malaria Vectors: Evidence for Adaptive Evolution in LRIM1 in Anopheles arabiensis

Co-evolution between Plasmodium species and its vectors may result in adaptive changes in genes that are crucial components of the vector's defense against the pathogen. By analyzing which genes show evidence of positive selection in malaria vectors, but not in closely related non-vectors, we can identify genes that are crucial for the mosquito's resistance against Plasmodium.We investigated genetic variation of three anti-malarial genes; CEC1, GNBP-B1 and LRIM1, in both vector and non-vector species of the Anopheles gambiae complex. Whereas little protein differentiation was observed between species in CEC1 and GNBP-B1, McDonald-Kreitman and maximum likelihood tests of positive selection show that LRIM1 underwent adaptive evolution in a primary malaria vector; An. arabiensis. In particular, two adjacent codons show clear signs of adaptation by having accumulated three out of four replacement substitutions. Furthermore, our data indicate that this LRIM1 allele has introgressed from An. arabiensis into the other main malaria vector An. gambiae.Although no evidence exists to link the adaptation of LRIM1 to P. falciparum infection, an adaptive response of a known anti-malarial gene in a primary malaria vector is intriguing, and may suggest that this gene could play a role in Plasmodium resistance in An. arabiensis. If so, our data also predicts that LRIM1 alleles in An. gambiae vary in their level of resistance against P. falciparum

Gene expression profiling of monkeypox virus-infected cells reveals novel interfaces for host-virus interactions

Monkeypox virus (MPV) is a zoonotic Orthopoxvirus and a potential biothreat agent that causes human disease with varying morbidity and mortality. Members of the Orthopoxvirus genus have been shown to suppress antiviral cell defenses, exploit host cell machinery, and delay infection-induced cell death. However, a comprehensive study of all host genes and virus-targeted host networks during infection is lacking. To better understand viral strategies adopted in manipulating routine host biology on global scale, we investigated the effect of MPV infection on Macaca mulatta kidney epithelial cells (MK2) using GeneChip rhesus macaque genome microarrays. Functional analysis of genes differentially expressed at 3 and 7 hours post infection showed distinctive regulation of canonical pathways and networks. While the majority of modulated histone-encoding genes exhibited sharp copy number increases, many of its transcription regulators were substantially suppressed; suggesting involvement of unknown viral factors in host histone expression. In agreement with known viral dependence on actin in motility, egress, and infection of adjacent cells, our results showed extensive regulation of genes usually involved in controlling actin expression dynamics. Similarly, a substantial ratio of genes contributing to cell cycle checkpoints exhibited concerted regulation that favors cell cycle progression in G1, S, G2 phases, but arrest cells in G2 phase and inhibits entry into mitosis. Moreover, the data showed that large number of infection-regulated genes is involved in molecular mechanisms characteristic of cancer canonical pathways. Interestingly, ten ion channels and transporters showed progressive suppression during the course of infection. Although the outcome of this unusual channel expression on cell osmotic homeostasis remains unknown, instability of cell osmotic balance and membrane potential has been implicated in intracellular pathogens egress. Our results highlight the role of histones, actin, cell cycle regulators, and ion channels in MPV infection, and propose these host functions as attractive research focal points in identifying novel drug intervention sites

A Genetically Hard-Wired Metabolic Transcriptome in Plasmodium falciparum Fails to Mount Protective Responses to Lethal Antifolates

Genome sequences of Plasmodium falciparum allow for global analysis of drug responses to antimalarial agents. It was of interest to learn how DNA microarrays may be used to study drug action in malaria parasites. In one large, tightly controlled study involving 123 microarray hybridizations between cDNA from isogenic drug-sensitive and drug-resistant parasites, a lethal antifolate (WR99210) failed to over-produce RNA for the genetically proven principal target, dihydrofolate reductase-thymidylate synthase (DHFR-TS). This transcriptional rigidity carried over to metabolically related RNA encoding folate and pyrimidine biosynthesis, as well as to the rest of the parasite genome. No genes were reproducibly up-regulated by more than 2-fold until 24 h after initial drug exposure, even though clonal viability decreased by 50% within 6 h. We predicted and showed that while the parasites do not mount protective transcriptional responses to antifolates in real time, P. falciparum cells transfected with human DHFR gene, and adapted to long-term WR99210 exposure, adjusted the hard-wired transcriptome itself to thrive in the presence of the drug. A system-wide incapacity for changing RNA levels in response to specific metabolic perturbations may contribute to selective vulnerabilities of Plasmodium falciparum to lethal antimetabolites. In addition, such regulation affects how DNA microarrays are used to understand the mode of action of antimetabolites