Taking a bite out of vector-transmitted infectious diseases

Artificial Feeding Systems for Vector-Borne Disease Studies

This review examines the advancements and methodologies of artificial feeding systems for the study of vector-borne diseases, offering a critical assessment of their development, advantages, and limitations relative to traditional live host models. It underscores the ethical considerations and practical benefits of such systems, including minimizing the use of live animals and enhancing experimental consistency. Various artificial feeding techniques are detailed, including membrane feeding, capillary feeding, and the utilization of engineered biocompatible materials, with their respective applications, efficacy, and the challenges encountered with their use also being outlined. This review also forecasts the integration of cutting-edge technologies like biomimicry, microfluidics, nanotechnology, and artificial intelligence to refine and expand the capabilities of artificial feeding systems. These innovations aim to more accurately simulate natural feeding conditions, thereby improving the reliability of studies on the transmission dynamics of vector-borne diseases. This comprehensive review serves as a foundational reference for researchers in the field, proposing a forward-looking perspective on the potential of artificial feeding systems to revolutionize vector-borne disease research.

Novel Essential Oils Blend as a Repellent and Toxic Agent against Disease-Transmitting Mosquitoes

Bio-insecticidal research has focused on long-term vector control using essential oils (EOs). This study examined the larvicidal, oviposition-deterrent, and repellent properties of five medicinal herb-based EO formulations (EOFs) on mosquitoes that are vectors of dengue, filariasis, and malaria. EOFs were significantly more toxic to the larvae and pupae of Culex quinquefasciatus, Anopheles stephensi, and Aedes aegypti with LC₅₀ = 9.23, 12.85, and 14.46 ppm, as well with 10.22, 11.39, and 12.81 ppm, with oviposition active indexes of -0.84, -0.95, and -0.92, respectively. Oviposition-deterrent repellence was found in 91.39%, 94.83%, and 96.09%. EOs and N, N-Diethyl-3-methylbenzamide (DEET) were prepared at various concentrations for time duration repellent bioassays (6.25-100 ppm). Ae. aegypti, An. stephensi, and Cx. quinquefasciatus were monitored for 300, 270, and 180 min, respectively. At 100 ppm, EOs and DEET had comparable repellence in terms of test durations. EOF's primary components d-limonene (12.9%), 2,6-octadienal, 3,7-dimethyl, (Z) (12.2%), acetic acid, phenylmethyl ester (19.6%), verbenol (7.6%), and benzyl benzoate (17.4%) may be combined to make a mosquito larvicidal and repellant equivalent to synthetic repellent lotions. In the molecular dynamics simulations, limonene (-6.1 kcal/mol) and benzyl benzoate (-7.5 kcal/mol) had a positive chemical association with DEET (-6.3 kcal/mol) and interacted with the OBP binding pocket with high affinity and stability. This research will help local herbal product manufacturers and the cosmetics industry in developing 100% herbal insect repellent products to combat mosquito-borne diseases, including dengue, malaria, and filariasis.

Seaweed Sargassum wightii mediated preparation of TiO2 nanoparticles, larvicidal activity against malaria and filariasis vectors, and its effect on non-target organisms

Malaria and Lymphatic filariasis are considered significant public health concerns in several countries. As a researcher, controlling those mosquitos using safe and eco-friendly insecticides is essential. Thus, we aimed to explore the potential use of seaweed Sargassum wightii for the biosynthesis of TiO2 NPs and evaluate its efficiency in controlling disease-transmitting mosquito larvae (using Anopheles subpictus and Culex quinquefasciatus larvae as model systems (in vivo)) as well as its potential effect on non-target organisms (using Poecilia reticulata fish as an experimental model). XRD, FT-IR, SEM-EDAX, and TEM carried out the characterization of TiO2 NPs. It evaluated the larvicidal activity against the fourth instar larvae of A. subpictus and C. quinquefasciatus. The larvicidal mortality was observed after 24 h of exposure to S. wightii extract and TiO2 NPs. S. wightii synthesized TiO2 NPs show excellent activity against A. subpictus and C. quinquefasciatus (LC50 = 4.37 and 4.68; LC90 = 8.33 and 8.97; χ2 = 5.741 and 4.531) mg/L respectively. The GC-MS results indicate the presence of some important long-chain phytoconstituents like linoleic acid, palmitic acid, oleic acid methyl ester, and stearic acid, among others. Furthermore, when testing the possible toxicity of biosynthesized NPs in a non-target organism, no adverse effects were observed in Poecilia reticulata fish exposed for 24 h, considering the evaluated biomarkers. Thus, overall, our study results reveal that biosynthesized TiO2 NPs are an effective and exciting eco-friendly approach to controlling the A. subpictus and C. quinquefasciatus.

Biocidal action, characterization, and molecular docking of Mentha piperita (Lamiaceae) leaves extract against Culex quinquefasciatus (Diptera: Culicidae) larvae

Mosquitoes are found in tropical and subtropical areas and are the carriers of a variety of diseases that are harmful to people’s health. e.g., malaria, filariasis, chikungunya, dengue fever, etc. Although several insecticides are available, however, due to insect resistance and environmental hazards, more eco-friendly chemicals are needed for insect control. So, the current research was planned to explore the prospective of Mentha piperita to be used for the formulation of larvicides against mosquito Culex quinquefasciatus. The ethanolic and water extracts of M. piperita leaves were prepared using the soxhlet apparatus. The extracts were dried and subjected to prepare five concentrations multiple of 80 ppm. Each concentration was applied for its larvicidal efficacy setting an experiment (in triplicate) in plastic containers of 1000 ml with extracts, 30 larvae of all four instars separately, and fed with dog biscuits along with controls. Observations were taken after each 12 hrs. till 72 hrs. The antioxidant perspective of M. piperita was determined by DPPH radical scavenging, total antioxidant capacity, and ferric reducing power assays. Using brine shrimp lethality bioactivity, the cytotoxic study was perceived. Standard techniques were used to classify the M. piperita extract using preliminary qualitative and quantitative phytochemicals, UV-Vis spectroscopy, FT-IR, and GC-MS analysis. M. piperita ethanolic leaves extract after 24 hrs. of exposure in 400 ppm showed 93% (LC₅₀ = 208.976 ppm) mortality in ethanolic extract and 80% (LC₉₀ = 246.900 ppm) in the water extract. In treated larvae, biochemical examination revealed a substantial (P<0.05) decrease in proteins, carbohydrates, and fat contents. The ethanol extract of M. piperita was the most efficient, killing brine shrimp nauplii in 50% to 90% of cases. TAC (125.4 3.5gAAE/mg DW) and FRP (378.1 1.0gAAE/mg DW) were highest in the ethanolic extract of M. piperita. The presence of medicinally active components such as alkaloids, carbohydrates, flavonoids, and others in M. piperita leaves extract in ethanol was discovered. The UV-Vis spectrum showed two peaks at 209.509 and 282.814 nm with the absorption of 2.338 and 0.796 respectively. The FT-IR consequences exhibited the occurrence of alcohols, alkanes, aldehyde, aromatic rings, ether linkage, ester, and halo- compounds. The GC-MS analysis according to peak (%) area and retention time showed ten phytochemicals consisting of six major and four minor compounds. Among all the compounds, 1, 2-benzene dicarboxylic acid, and 3-ethyl-5, 5-dimethyl -6-phenyl bound well to the NS3 protease domain with PDB ID: 2FOM. Hence, for the prevention of health hazards and mosquito control, M. Piperita is a potential source of chemicals for insecticide formulation.

Identification of Algerian field-caught mosquito vectors by MALDI-TOF MS

Vector-borne diseases represent a real threats worldwide, in reason of the lack of vaccine and cure for some diseases. Among arthropod vectors, mosquitoes are described to be the most dangerous animal on earth, resulting in an estimated 725,000 deaths per year due to their borne diseases. Geographical position of Algeria makes this country a high risk area for emerging and re-emerging diseases, such as dengue coming from north (Europe) and malaria from south (Africa). To prevent these threats, rapid and continuous surveillance of mosquito vectors is essential. For this purpose we aimed in this study to create a mosquito vectors locale database using MALDI-TOF mass spectrometry technology for rapid identification of these arthropods. This methodology was validated by testing 211 mosquitoes, including four species (Aedes albopictus, Culex pipiens, Culex quinquefasciatus, and Culiseta longiareolata), in two northern wilayahs of Algeria (Algiers and Bejaia). Species determination by MALDI TOF MS was highly concordant with reference phenotypic and genetic methods. Using this MALDI-TOF MS tool will allow better surveillance of mosquito species able to transmit mosquito borne diseases in Algeria.

Soft X-ray Microscopy Techniques for Medical and Biological Imaging at TwinMic—Elettra

Progress in nanotechnology calls for material probing techniques of high sensitivity and resolution. Such techniques are also used for high-impact studies of nanoscale materials in medicine and biology. Soft X-ray microscopy has been successfully used for investigating complex biological processes occurring at micrometric and sub-micrometric length scales and is one of the most powerful tools in medicine and the life sciences. Here, we present the capabilities of the TwinMic soft X-ray microscopy end-station at the Elettra synchrotron in the context of medical and biological imaging, while we also describe novel uses and developments.

Green fabrication of Co and Co3O4 nanoparticles and their biomedical applications: A review

Nanotechnology is the fabrication, characterization, and potential application of various materials at the nanoscale. Over the past few decades, nanomaterials have attracted researchers from different fields because of their high surface-to-volume ratio and other unique and remarkable properties. Cobalt and cobalt oxide nanoparticles (NPs) have various biomedical applications because of their distinctive antioxidant, antimicrobial, antifungal, anticancer, larvicidal, antileishmanial, anticholinergic, wound healing, and antidiabetic properties. In addition to biomedical applications, cobalt and cobalt oxide NPs have been widely used in lithium-ion batteries, pigments and dyes, electronic thin film, capacitors, gas sensors, heterogeneous catalysis, and for environmental remediation purposes. Different chemical and physical approaches have been used to synthesize cobalt and cobalt oxide NPs; however, these methods could be associated with eco-toxicity, cost-effectiveness, high energy, and time consumption. Recently, an eco-friendly, safe, easy, and simple method has been developed by researchers, which uses biotic resources such as plant extract, microorganisms, algae, and other biomolecules such as starch and gelatin. Such biogenic cobalt and cobalt oxide NPs offer more advantages over other physicochemically synthesized methods. In this review, we have summarized the recent literature for the understanding of green synthesis of cobalt and cobalt oxide NPs, their characterization, and various biomedical applications.

Annona muricata: An alternate mosquito control agent with special reference to inhibition of detoxifying enzymes in Aedes aegypti

This study was aimed to investigate an effectual level of Annona muricata (soursop) extracts on mosquito vectors namely, Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. The toxicity study on non-target organism and other important biochemical marker enzymes to find and illustrate the exact mechanism of specific enzymes responsible for detoxifying allelochemicals. Among the various soursop seed kernel extracts tested for larvicidal activity, the 0.9% saline extract exhibited maximum mortality (100%) against three vectors at the lowest concentration for 24 h exposure. Based on these findings, the saline extract was opted for further studies including toxicity on non-target organism and systemic effects on important biochemical constituents in the larvae A. aegypti at the lethal threshold time (18 h) with LC₅₀ concentration (0.009 mg/mL). The tested extract against non-target aquatic fourth instar larvae Chironomus costatus was safe up to 0.0028 mg/mL for 24 h exposure and the mortality was observed only above the concentration 0.0028 mg/mL used in the study. The systemic effects on main neuron transmitter Acetylcholinesterase (p ≤ 0.01), xenobiotics detoxifying enzyme of α-and β-carboxylesterase (p ≤ 0.05; p ≤ 0.01) and antioxidant enzyme glutathione S-transferase (p ≤ 0.05) were reduced significantly in quantitative analysis. Analysis of such biochemical constituents of proteins and enzymes α-and β-carboxylesterase were considerably down regulated in the resolving native-PAGE. In contrast, acid and alkaline phosphatase were upregulated in both quantitative and qualitative analysis. This investigation clearly demonstrates the soursop extract has potent larvicidal agent with alterations in biochemical constituents of exposed larvae of A. aegypti.

Linking Water Quality to Aedes aegypti and Zika in Flood-Prone Neighborhoods

The ability of ecosystems to regulate water quality and flood events has been linked to health outcomes, including mosquito-borne illnesses. In the San Juan Bay Estuary watershed of Puerto Rico, habitat alterations and land-use development have disrupted watershed hydrology, exacerbating wastewater discharges and subjecting some neighborhoods to frequent flooding events. In 2016, the mosquito-borne illness Zika became a new cause for concern. We hypothesized that nutrient-enriched flood water could provide pulses of supplemental nutrients to local mosquito populations. We conducted a field study in six neighborhoods adjacent to the estuary to assess whether environmental variability of nutrient inputs could be linked to breeding habitat containers, Aedes aegypti larvae and adults, and the acquisition of Zika virus by adult mosquitoes. The most frequently flooded neighborhood had consistently higher levels of nitrogen in estuary water, leaf detritus, containers, and adult mosquitoes compared to other neighborhoods. Adult body nitrogen was significantly related to both nitrogen content of containers and leaf detritus from the local trapping area. Disseminated Zika concentration in adult Ae. aegypti tended to decrease as body carbon and nitrogen increased. Our study provides preliminary evidence that environmental variability in nutrient inputs can influence viral acquisition by mosquito vectors. This suggests that management actions to reduce flooding and improve water quality should go hand-in-hand with more traditional vector control methods, such as aerial spraying, to help control spread of vector-borne diseases.

Phytochemical Profiling and Larval Control of Erythrina variegata Methanol Fraction against Malarial and Filarial Vector

Erythrina variegata (E. variegata) bioactive chemical has been the potential to be utilized as a good, eco-friendly approach for the control of mosquito population. In the present investigation, methanol extract using insecticidal compounds isolated against mosquito larvae kill assay was carried out. Secondary metabolism was characterized by thin layer chromatography, column chromatography, Fourier transform-infrared spectroscopy, gas chromatography-mass spectral, and identification of compound. Mosquito immature third instar larval, Anopheles stephensi, and Culex quinquefasciatus have been exposed to different concentrations of 50-250 µg/ml. Totally, larvae were death rate 98.2% (significant value 0.001b) from methanol extract and it is significant toxicity against larvae of An. stephensi and Cx. quinquefasciatus with LC50/LC99 values were 157.69/339.55 µg/ml and 137.67/297.33 µg/ml, respectively. FT-IR analysis in the functional groups such as alcohol, amines, amides, alkenes, 1⁎ amines, aromatic amines, aliphatic amines, 1⁎,2⁎ amines, and alkyl halides searched the identity of secondary metabolites, which may act as 12-Octadecenoic acid, methyl ester compound and clearly indicates being phytochemical. Chemical constituents of twenty-five compounds were identified in the methanol extract. The major components were 12-Octadecenoic acid and methyl ester (37.31%). Compound molecules consist of carbon 19 atoms (gray), hydrogen 36 atoms (greenish blue), and oxygen 2 atoms (red), indicated by the different colors. The results were obtained suggesting that, in addition to their pharmaceutical and medicine sources, 12-Octadecenoic acid, methyl ester compound can also serve as a natural mosquito control.

Rapid identification of medically important mosquitoes by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Background

Accurate and rapid identification of dipteran vectors is integral for entomological surveys and is a vital component of control programs for mosquito-borne diseases. Conventionally, morphological features are used for mosquito identification, which suffer from biological and geographical variations and lack of standardization. We used matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for protein profiling of mosquito species from North India with the aim of creating a MALDI-TOF MS database and evaluating it.

Methods

Mosquito larvae were collected from different rural and urban areas and reared to adult stages. The adult mosquitoes of four medically important genera, Anopheles, Aedes, Culex and Armigerus, were morphologically identified to the species level and confirmed by ITS2-specific PCR sequencing. The cephalothoraces of the adult specimens were subjected to MALDI-TOF analysis and the signature peak spectra were selected for creation of database, which was then evaluated to identify 60 blinded mosquito specimens.

Results

Reproducible MALDI-TOF MS spectra spanning over 2–14 kDa m/z range were produced for nine mosquito species: Anopheles (An. stephensi, An. culicifacies and An. annularis); Aedes (Ae. aegypti and Ae. albopictus); Culex (Cx. quinquefasciatus, Cx. vishnui and Cx. tritaenorhynchus); and Armigerus (Ar. subalbatus). Genus- and species-specific peaks were identified to create the database and a score of > 1.8 was used to denote reliable identification. The average numbers of peaks obtained were 55–60 for Anopheles, 80–100 for Aedes, 30–60 for Culex and 45–50 peaks for Armigeres species. Of the 60 coded samples, 58 (96.67%) were correctly identified by MALDI-TOF MS with a score > 1.8, while there were two unreliable identifications (both Cx. quinquefasciatus with scores < 1.8).

Conclusions

MALDI-TOF MS appears to be a pragmatic technique for accurate and rapid identification of mosquito species. The database needs to be expanded to include species from different geographical regions and also different life-cycle stages to fully harness the technique for entomological surveillance programs.

Electronic supplementary material

The online version of this article (10.1186/s13071-018-2854-0) contains supplementary material, which is available to authorized users.

Can You Judge a Disease Host by the Company It Keeps? Predicting Disease Hosts and Their Relative Importance: A Case Study for Leishmaniasis

Zoonoses are an important class of infectious diseases. An important element determining the impact of a zoonosis on domestic animal and human health is host range. Although for particular zoonoses some host species have been identified, until recently there have been no methods to predict those species most likely to be hosts or their relative importance. Complex inference networks infer potential biotic interactions between species using their degree of geographic co-occurrence, and have been posited as a potential tool for predicting disease hosts. Here we present the results of an interdisciplinary, empirical study to validate a model based on such networks for predicting hosts of Leishmania (L.) mexicana in Mexico. Using systematic sampling to validate the model predictions we identified 22 new species of host (34% of all species collected) with the probability to be a host strongly dependent on the probability of co-occurrence of vector and host. The results confirm that Leishmania (L.) mexicana is a generalist parasite but with a much wider host range than was previously thought. These results substantially change the geographic risk profile for Leishmaniasis and provide insights for the design of more efficient surveillance measures and a better understanding of potential dispersal scenarios.

Emerging and neglected zoonoses are an important global threat to public health. Host range, in particular, is a crucial factor in determining disease risk and the potential for adequate interventions. Here we show that Leishmania has a very wide host range and that Complex Inference Networks can be used to infer ecological relationships in the context of zoonoses, identifying both the potential hosts and their relative importance. These results substantially change the risk profile and potential control measures that can be used to combat the disease, allowing for the design of more efficient surveillance measures and a better understanding of potential dispersal scenarios.

Use of MALDI-TOF MS and culturomics to identify mosquitoes and their midgut microbiota

BACKGROUND

Mosquitoes transmit a wide range of human parasitic and viral diseases. In recent years, new techniques such as MALDI-TOF MS have been developed to identify mosquitoes at the species level, which is key for entomological surveys. Additionally, there is increasing interest in the mosquito microbiota and its role in vector capacity.

METHODS

The culturomics approach previously used in our laboratory to study human gut microbiota was applied to evaluate the midgut bacterial diversity of Anopheles gambiae (wild and laboratory strains), Aedes albopictus (wild and laboratory strains) and Culex quinquefasciatus (wild strains) in order to determine the influence of the environmental status on the midgut microbiota of the mosquitoes.

RESULTS

Mosquitoes collected in the field were accurately identified by MALDI-TOF MS analysis of their legs. Adult mosquito midgut microbiota was composed of four phyla, including Proteobacteria, Bacteroidetes, Actinobacteria and Firmicutes. The majority of the bacteria detected in the microbiota of mosquitoes were gram-negative and belong to the phylum Proteobacteria. MALDI-TOF MS identified for the first time a new bacterial species from An. gambiae midgut microbiota.

CONCLUSION

In this study, the culturomics approach was found to be a reliable technique for exploring the diversity of the mosquito microbiota. MALDI-TOF MS was confirmed as a promising technique to identify mosquitoes collected in the field. Culturomics allowed the isolation of a new bacterial species not previously associated with mosquito vectors. The environment plays a role in the bacterial diversity of the microbiota, which could enable the development of new control strategies for mosquito-borne disease.

Larvicidal efficacy and chemical constituents of O. gratissimum L. (Lamiaceae) essential oil against Aedes albopictus Skuse (Diptera: Culicidae)

The current study accentuates the use of botanicals as an alternative to the chemical compounds in vector control by estimating the mosquito larvicidal potential of Ocimum gratissimum L. leaf essential oil against the fourth instar larvae of Aedes albopictus Skuse (Diptera: Culicidae). The chemical composition of essential oil from leaves was evaluated using gas chromatography-mass spectrometry (GC/MS) analysis. GC/MS revealed that the essential oil of O. gratissimum contained 51 compounds. The major chemical constituents identified were 3-allyl-6-methoxyphenol (19.30%), 4-(5-ethenyl-1-azabicyclo (2, 2, 2) octan-2) (16.82%), 1-(2, 5-dimethoxyphenyl)-propanol (12.23%) and 1-(1-hydroxybutyl)-2, 5-dimethoxybenzene (5.53%). The essential oil showed pertinent larvicidal effect, and the LC50 value in 24 h was 26.10 ppm (LC90 = 82.83 ppm). Aromatic plants and their essential oils are very important sources of many compounds that are used for different applications, and they are more promising pesticides or insecticides for control of mosquito populations than synthetic ones. The results of the present investigation justify the larvicidal potential of leaf essential oil of O. gratissimum as a safer and more effective larvicide against A. albopictus.

One-pot green synthesis of silver nanocrystals using Hymenodictyon orixense: a cheap and effective tool against malaria, chikungunya and Japanese encephalitis mosquito vectors?

Mosquitoes are important vectors of malaria, dengue, Zika virus and many other parasites and pathogens of public health relevance.

Molecular descriptors calculation as a tool in the analysis of the antileishmanial activity achieved by two series of diselenide derivatives. An insight into its potential action mechanism

A molecular modeling study has been carried out on two previously reported series of symmetric diselenide derivatives that show remarkable antileishmanial in vitro activity against Leishmania infantum intracellular amastigotes and in infected macrophages (THP-1 cells), in addition to showing favorable selectivity indices. Series 1 consists of compounds that can be considered as central scaffold constructed with a diaryl/dialkylaryl diselenide central nucleus, decorated with different substituents located on the aryl rings. Series 2 consists of compounds constructed over a diaryl diselenide central nucleus, decorated in 4 and 4' positions with an aryl or heteroaryl sulfonamide fragment, thus forming the diselenosulfonamide derivatives. With regard to the diselenosulfonamide derivatives (2 series), the activity can be related, as a first approximation, with (a) the ability to release bis(4-aminophenyl) diselenide, the common fragment which can be ultimately responsible for the activity of the compounds. (b) the anti-parasitic activity achieved by the sulfonamide pharmacophore present in the analyzed derivatives. The data that support this connection include the topography of the molecules, the conformational behavior of the compounds, which influences the bond order, as well as the accessibility of the hydrolysis point, and possibly the hydrophobicity and polarizability of the compounds.

Colonization of Cimex lectularius with methicillin-resistant Staphylococcus aureus

A recent paper published by Lowe and Romney in Emerging Infectious Diseases titled, Bed bugs as Vectors for Drug-Resistant Bacteria has sparked a renewed interest in bed bug vector potential. We followed a pyrethroid resistant strain of the human bed bug (Cimex lectularius, L.) fed either human blood or human blood with added methicillin resistant Staphylococcus aureus (MRSA) for 9 days post-feeding. Results indicated that while the bed bug midgut is a hospitable environment for MRSA, the bacteria does not survive longer than 9 days within the midgut. Additionally, MRSA is not amplified within the midgut of the bug as the infection was cleared within 9 days. Due to the weekly feeding behaviours of bed bugs, these results suggest that bed bug transmission of MRSA is highly unlikely.

Survey of Bartonella spp. in U.S. bed bugs detects Burkholderia multivorans but not Bartonella

Bed bugs (Cimex lectularius L.) have resurged in the United States and globally. Bed bugs are hematophagous ectoparasites of humans and other animals, including domestic pets, chickens, and bats, and their blood feeding habits contribute to their potential as disease vectors. Several species of Bartonella are re-emergent bacterial pathogens that also affect humans, domestic pets, bats and a number of other wildlife species. Because reports of both bed bugs and Bartonella have been increasing in the U.S., and because their host ranges can overlap, we investigated whether the resurgences of these medically important pathogens and their potential vector might be linked, by screening for Bartonella spp. in bed bugs collected from geographic areas where these pathogens are prevalent and from bed bugs that have been in culture in the laboratory for several years. We screened a total of 331 bed bugs: 316 bed bugs from 36 unique collections in 29 geographic locations in 13 states, 10 bed bugs from two colonies maintained in the laboratory for 3 yr, and 5 bed bugs from a colony that has been in culture since before the recent resurgence of bed bugs. Bartonella spp. DNA was screened using a polymerase chain reaction assay targeting the 16S–23S rRNA intergenic transcribed spacer region. Bartonella DNA was not amplified from any bed bug, but five bed bugs from four different apartments of an elderly housing building in North Carolina contained DNA sequences that corresponded to Burkholderia multivorans, an important pathogen in nosocomial infections that was not previously linked to an arthropod vector.

Matrix-assisted laser desorption ionization--time of flight mass spectrometry: an emerging tool for the rapid identification of mosquito vectors

Background

The identification of mosquito vectors is typically based on morphological characteristics using morphological keys of determination, which requires entomological expertise and training. The use of protein profiling by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS), which is increasingly being used for the routine identification of bacteria, has recently emerged for arthropod identification.

Methods

To investigate the usefulness of MALDI-TOF-MS as a mosquito identification tool, we tested protein extracts made from mosquito legs to create a database of reference spectra. The database included a total of 129 laboratory-reared and field-caught mosquito specimens consisting of 20 species, including 4 Aedes spp., 9 Anopheles spp., 4 Culex spp., Lutzia tigripes, Orthopodomyia reunionensis and Mansonia uniformis. For the validation study, blind tests were performed with 76 specimens consisting of 1 to 4 individuals per species. A cluster analysis was carried out using the MALDI-Biotyper and some spectra from all mosquito species tested.

Results

Biomarker mass sets containing 22 and 43 masses have been detected from 100 specimens of the Anopheles, Aedes and Culex species. By carrying out 3 blind tests, we achieved the identification of mosquito vectors at the species level, including the differentiation of An. gambiae complex, which is possible using MALDI-TOF-MS with 1.8 as the cut-off identification score. A cluster analysis performed with all available mosquito species showed that MALDI-Biotyper can distinguish between specimens at the subspecies level, as demonstrated for An gambiae M and S, but this method cannot yet be considered a reliable tool for the phylogenetic study of mosquito species.

Conclusions

We confirmed that even without any specific expertise, MALDI-TOF-MS profiling of mosquito leg protein extracts can be used for the rapid identification of mosquito vectors. Therefore, MALDI-TOF-MS is an alternative, efficient and inexpensive tool that can accurately identify mosquitoes collected in the field during entomological surveys.

Immuno-suppressive effects of aqueous extract of soapnut Sapindus emarginatus on the larvae and pupae of vector mosquito, Aedes aegypti

We recently reported the presence of potent anti-mosquito activity in aqueous kernel extract of the soapnut, Sapindus emarginatus, and demonstrated its impact on marker enzymes in larvae and pupae of the vector mosquito, Aedes aegypti. As a sequel to these findings, the present study elucidates immunotoxicity of this extract with respect to hemocyte-mediated cellular immune responses in fourth instar larvae and pupae as well as cuticular melanization reaction in the larvae of A. aegypti. The exposure of these two developmental stages of the mosquito to the soapnut extract at a lethal threshold concentration neither affected hemocyte viability tested up to 3h in vitro nor did it influence the hemocyte count. By contrast, exposure of the mosquito larvae and pupae to this extract significantly reduced the ability of their hemocytes to bind yeast cells, an important early event in the process of non-self recognition by immune cells. Consequently, the phagocytic activity of these hemocytes against yeast cells was also found to be adversely affected upon exposure of larvae and pupae to the extract. Besides, a perceptible initial delay in melanization reaction at the injured site of the cuticle in the extract-exposed larvae was observed. All these findings demonstrate, for the first time, the immuno-suppressive potential of a botanical biocide in the vector mosquito.

The biological control of disease vectors

Vector-borne diseases are common in nature and can have a large impact on humans, livestock and crops. Biological control of vectors using natural enemies or competitors can reduce vector density and hence disease transmission. However, the indirect interactions inherent in host-vector disease systems make it difficult to use traditional pest control theory to guide biological control of disease vectors. This necessitates a conceptual framework that explicitly considers a range of indirect interactions between the host-vector disease system and the vector's biological control agent. Here we conduct a comparative analysis of the efficacy of different types of biological control agents in controlling vector-borne diseases. We report three key findings. First, highly efficient predators and parasitoids of the vector prove to be effective biological control agents, but highly virulent pathogens of the vector also require a high transmission rate to be effective. Second, biocontrol agents can successfully reduce long-term host disease incidence even though they may fail to reduce long-term vector densities. Third, inundating a host-vector disease system with a natural enemy of the vector has little or no effect on reducing disease incidence, but inundating the system with a competitor of the vector has a large effect on reducing disease incidence. The comparative framework yields predictions that are useful in developing biological control strategies for vector-borne diseases. We discuss how these predictions can inform ongoing biological control efforts for host-vector disease systems.

Effects of sublethal pyrethroid exposure on the host-seeking behavior of female mosquitoes

A common method of adult mosquito control consists of residual application on surfaces and aerial spraying often using pyrethroids. However, not all insects that contact insecticides are killed. Sublethal exposure to neurotoxic compounds can negatively affect sensory organs and reduce efficiency of host location. Flight tracks of host-seeking female Culex quinquefasciatus, Anopheles albimanus, and Aedes aegypti in a wind tunnel were video-recorded to compare activation of host-seeking and patterns of flight orientation to host odors. During host-seeking flights, all three mosquito species differed significantly in flight duration, velocity, turn angle, and angular velocity. Mosquitoes were then exposed to sublethal levels (LD(25) ) of pyrethroid insecticides to evaluate the effects of the neurotoxicants 24 hours post-exposure. Significant reductions in time of activation to flight and flight direction were observed in mosquitoes exposed to deltamethrin and permethrin. Additionally, pesticide-treated Cx. quinquefasciatus mosquitoes flew significantly slower, spent more time in flight, and turned more frequently than untreated controls.

Bedbugs and infectious diseases

Bedbugs are brown and flat hematophagous insects. The 2 cosmopolite species, Cimex lectularius and Cimex hemipterus, feed on humans and/or domestic animals, and recent outbreaks have been reported in occidental countries. Site assessment for bedbug eradication is complex but can be assured, despite emerging insecticide resistance, by hiring a pest-control manager. The common dermatological presentation of bites is an itchy maculopapular wheal. Urticarial reactions and anaphylaxis can also occur. Bedbugs are suspected of transmitting infectious agents, but no report has yet demonstrated that they are infectious disease vectors. We describe 45 candidate pathogens potentially transmitted by bedbugs, according to their vectorial capacity, in the wild, and vectorial competence, in the laboratory. Because of increasing demands for information about effective control tactics and public health risks of bedbugs, continued research is needed to identify new pathogens in wild Cimex species (spp) and insecticide resistance.

Effects of extract of soapnut Sapindus emarginatus on esterases and phosphatases of the vector mosquito, Aedes aegypti (Diptera: Culicidae)

Our earlier investigations with kernels from the soapnut Sapindus emarginatus revealed it as a new source of botanical biocide with potent antimosquito activity, as evident from the proven unique ability of the aqueous kernel extract to kill all the developmental stages of three important vector mosquito species, Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. This extract was also found to be safe for two non-target aquatic insects. As a sequel to these findings, we have further examined quantitative and qualitative changes in total proteins, esterases, and phosphatases in whole body homogenates of fourth instar larvae and pupae of A. aegypti exposed to this extract at an appropriate threshold time for its lethal effect to gain insights into the impact of the botanical biocide on biochemical characteristics of the target vector mosquito at two distinct developmental stages. The profiles of proteins, esterases (acetylcholinesterse, α- and β-carboxylesterases), and phosphatases (acid and alkaline) exhibited distinct patterns of variation during normal development of fourth instar larvae and pupae, indicating intrinsic difference in biochemical features between these two developmental stages of A. aegypti. Upon exposure of the larvae to the extract, significant reduction in the activities of acetylcholinesterse, β-carboxylesterase, and acid phosphatases were recorded, whereas the total proteins, α-carboxylesterase and alkaline phosphatase activities were unaffected. By contrast, only alkaline phosphatase activity was significantly affected in pupae exposed to the extract. Analysis of these enzymes in native PAGE revealed that they exist in isoforms in both the larvae and pupae. The alterations in the levels of enzymatic activities observed from the quantitative assays of various enzymes were reflected by the respective zymograms with perceptible differences in the intensity and the number of bands detected especially with β-carboxylesterase, acid and alkaline phosphatase activity between the control and exposed test organisms. Despite the fact that the soapnut kernel extract causes mortality of both the larvae and pupae of A. aegypti, the findings of this study demonstrate that the impact of this extract is most pronounced in various enzyme profiles of the larvae rather than the pupae. Such discrepancy implicates the presence of unique biochemical mechanisms in the pupae of mosquito for detoxification of botanical biocides.

Development of a vaccinia virus based reservoir-targeted vaccine against Yersinia pestis

Yersinia pestis, the causative organism of plague, is a zoonotic organism with a worldwide distribution. Although the last plague epidemic occurred in early 1900s, human cases continue to occur due to contact with infected wild animals. In this study, we have developed a reservoir-targeted vaccine against Y. pestis, to interrupt transmission of disease in wild animals as a potential strategy for decreasing human disease. A vaccinia virus delivery system was used to express the F1 capsular protein and the LcrV type III secretion component of Y. pestis as a fusion protein. Here we show that a single dose of this vaccine administered orally, generates a dose-dependent antibody response in mice. Antibody titers peak by 3 weeks after administration and remain elevated for a minimum of 45 weeks. Vaccination provided up to 100% protection against challenge with Y. pestis administered by intranasal challenge at 10 times the lethal dose with protection lasting a minimum of 45 weeks. An orally available, vaccinia virus expressed vaccine against Y. pestis may be a suitable vaccine for a reservoir targeted strategy for the prevention of enzootic plague.

Trypanothione reductase high-throughput screening campaign identifies novel classes of inhibitors with antiparasitic activity

High-throughput screening of 100,000 lead-like compounds led to the identification of nine novel chemical classes of trypanothione reductase (TR) inhibitors worthy of further investigation. Hits from five of these chemical classes have been developed further through different combinations of preliminary structure-activity relationship rate probing and assessment of antiparasitic activity, cytotoxicity, and chemical and in vitro metabolic properties. This has led to the identification of novel TR inhibitor chemotypes that are drug-like and display antiparasitic activity. For one class, a series of analogues have displayed a correlation between TR inhibition and antiparasitic activity. This paper explores the process of identifying, investigating, and evaluating a series of hits from a high-throughput screening campaign.

Mosquito-borne diseases

Despite centuries of control efforts, mosquito-borne diseases are flourishing worldwide. With a disproportionate effect on children and adolescents, these conditions are responsible for substantial global morbidity and mortality. Malaria kills more than 1 million children annually, chiefly in sub-Saharan Africa. Dengue virus has expanded its range over the past several decades, following its principal vector, Aedes aegypti, back into regions from which it was eliminated in the mid-20th century and causing widespread epidemics of hemorrhagic fever. West Nile virus has become endemic throughout the Americas in the past 10 years, while chikungunya virus has emerged in the Indian Ocean basin and mainland Asia to affect millions. Japanese encephalitis virus, too, has expanded its range in the Indian subcontinent and Australasia, mainly affecting young children. Filariasis, on the other hand, is on the retreat, the subject of a global eradication campaign. Efforts to limit the effect of mosquito-borne diseases in endemic areas face the twin challenges of controlling mosquito populations and delivering effective public health interventions. Travelers to areas endemic for mosquito-borne diseases require special advice on mosquito avoidance, immunizations, and malaria prophylaxis.

Warmer weather linked to tick attack and emergence of severe rickettsioses

The impact of climate on the vector behaviour of the worldwide dog tick Rhipicephalus sanguineus is a cause of concern. This tick is a vector for life-threatening organisms including Rickettsia rickettsii, the agent of Rocky Mountain spotted fever, R. conorii, the agent of Mediterranean spotted fever, and the ubiquitous emerging pathogen R. massiliae. A focus of spotted fever was investigated in France in May 2007. Blood and tissue samples from two patients were tested. An entomological survey was organised with the study of climatic conditions. An experimental model was designed to test the affinity of Rh. sanguineus for biting humans in variable temperature conditions. Serological and/or molecular tools confirmed that one patient was infected by R. conorii, whereas the other was infected by R. massiliae. Dense populations of Rh. sanguineus were found. They were infected with new genotypes of clonal populations of either R. conorii (24/133; 18%) or R. massiliae (13/133; 10%). April 2007 was the warmest since 1950, with summer-like temperatures. We show herein that the human affinity of Rh. sanguineus was increased in warmer temperatures. In addition to the originality of theses cases (ophthalmic involvements, the second reported case of R. massiliae infection), we provide evidence that this cluster of cases was related to a warming-mediated increase in the aggressiveness of Rh. sanguineus, leading to increased human attacks. From a global perspective, we predict that as a result of globalisation and warming, more pathogens transmitted by the brown dog tick may emerge in the future.

The impact of climate on the behaviour of the worldwide dog tick Rhipicephalus sanguineus is a cause of concern. This tick is a vector for life-threatening organisms including Rickettsia rickettsii, the agent of Rocky Mountain spotted fever, R. conorii, the agent of Mediterranean spotted fever, and the ubiquitous emerging pathogen R. massiliae. A focus of spotted fever was investigated in France in May 2007. One patient was found to be infected by R. conorii, whereas the other was infected by R. massiliae. Theses cases were original because of ophthalmic involvements, and the report of the second case of R. massiliae infection in the scientific literature. During an entomological survey, dense populations of Rh. sanguineus were found in the house where the patient had been bitten by ticks. Ticks were infected with either R. conorii or R. massiliae. Interestingly, April 2007 was the warmest since 1950, with summer-like temperatures. In this work, we show that the human affinity of Rh. sanguineus is increased in warmer temperatures, and provide evidence that this cluster of cases was related to a warming-mediated increase in the aggressiveness of Rh. sanguineus, leading to increased human attacks. From a global perspective, we predict that as a result of globalisation and warming, more pathogens transmitted by the brown dog tick may emerge in the future.