Mosquito Bites Research Articles

Lectin Microarray Analysis of Salivary Gland Glycoproteins from the Arboviral Vector Aedes aegypti and the Malaria Vector Anopheles stephensi.

Salivary glands proteins but not glycoconjugates have been previously studied in mosquito vectors of human diseases. Glycoconjugates from salivary gland-derived proteins from human-feeding tick vectors can elicit hypersensitivity reactions which may also occur with mosquito bites. Protein glycoconjugate in salivary glands of the principal arboviral vector Aedes aegypti and the rapidly spreading malaria vector Anopheles stephensi were therefore investigated. Forty different lectins in a microarray were used to analyse glycoconjugates in salivary gland proteins from both mosquito species. Salivary gland glycoproteins of both mosquitoes possessed similar lectin-binding specificities. Lectin-binding profiles in both mosquitoes showed the significant presence of oligomannose N-linked glycans, O-linked glycans, a limited presence of glycan structures capped with terminal GalNAc, GlcNAc, β linked Gal, α1-6 linked fucose, and no detectable sialic acids or terminal α-linked Gal in salivary gland glycoproteins. Aedes aegypti and An. stephensi possess similar salivary gland protein glycoconjugates to mosquito larval tissues. They differ from arachnid ticks in lacking detectable α-gal epitopes that are responsible for red meat allergy caused by tick bites.

R21 in Matrix-M adjuvant in UK malaria-naive adult men and non-pregnant women aged 18-45years: anopen-label, partially blinded, phase 1-2a controlled human malaria infection study.

R21 is a novel malaria vaccine, composed of a fusion protein of the malaria circumsporozoite protein and hepatitis Bsurface antigen. Following favourable safety and immunogenicity in a phase 1study, we aimed to assess the efficacy of R21 administered with Matrix-M (R21/MM) against clinical malaria in adults from the UK who were malaria naive in a controlled human malaria infection study. In this open-label, partially blinded, phase 1-2A controlled human malaria infection study undertaken inOxford, Southampton, and London, UK, we tested five novel vaccination regimens of R21/MM. Astandard three-dose regimen (groups 1and 6) was compared with a reduced (fractional) third dose (groups 2and 5) of R21/MM, concomitant administration with viral vectors ChAd63-MVA expressing ME-TRAP (group 3), and a two-dose R21/MM regimen (group 7). Controlled Human Malaria Infection (CHMI) was delivered by mosquito bite at Imperial College London, London, UK, 3-4 weeks after final vaccination (or 18months after final vaccination for group 6) alongside unvaccinated controls (groups 4A and 4B). The primary outcome measures were to assess safety of the vaccines in healthy malaria-naive volunteers and the efficacy (occurrence of blood-stage malaria infection) of the different vaccine regimens compared with non-vaccinated controls after CHMI. The trial was registered with ClinicalTrials.gov (NCT02905019). 66volunteers were enrolled with 59undergoing subsequent CHMI. All vaccination schedules were well tolerated. The highest level of protection against CHMI was observed in participants receiving the standard three-dose regimen of R21/MM (group 1, nine of 11volunteers protected) with protection maintained in three of five volunteers re-challenged by CHMI 7·5months later. Protection against malaria was also seen in group 2, group 3, and group 5compared with unvaccinated control participants. Total IgG antibody responses to the NANP repeat region of circumsporozoite protein peaked after the third dose of R21/MM in all volunteers and were well maintained to 90days after challenge. Reducing the third dose did not affect protection or antibody concentrations. Our study shows that R21/MM elicits high-level efficacy against clinical malaria in a controlled human infection model of malaria in adults who are malaria naive. These data supported the evaluation of R21/MM in field efficacy trials in the target population of young children in malaria-endemic areas. EU Horizon 2020, the UK Medical Research Council, the European Commission, the UK National Institute of Health Research, the Imperial NIHR Clinical Research Facility, the Oxford NIHR Biomedical Research Centre, and the Wellcome Trust.

Report of two severe cases of Japanese encephalitis virus in travelers returning to France, 2023-2024: clinical, diagnostic, and public health implications

ABSTRACT Background Japanese encephalitis virus (JEV) is a mosquito-borne pathogen responsible for Japanese encephalitis (JE) clinical cases in Asia and the Western Pacific. Non-JE-vaccinated patients can develop potentially life-threatening neurologic forms. Case Summary Here, we present two severe, non-fatal JEV cases in returning travelers from Cambodia (Case 1) and Cambodia and Vietnam (Case 2), imported to France in 2023–2024. Neither patient was vaccinated, and both presented neurologic symptoms requiring hospitalization. Cases were confirmed by RT-qPCR, IgM, and IgG rise and seroneutralization. Interestingly, this is the second report to describe the detection of the JEV genome in urine by RT-qPCR. Conclusion This study highlights the critical importance of JE vaccination and the implementation of other personal protective measures to avoid mosquito bites when traveling to a JEV-endemic region.

THE SPREAD OF CHIKUNGUNYA: A COMPREHENSIVE SURVEY AMONG PEOPLE OF KARACHI, PAKISTAN WITH AWARENESS, IMPACTS AND PREVENTION STRATEGIES

ABSTRACT: Objective: The basic aim of the study to evaluate and create awareness of people of Karachi regarding the spread of Chikungunya among people of Karachi, Pakistan. Methodology: Inoder to conduct this survey based study Google form were generated and several questions were asked to the people link of the Google form was shared through different social media platforms. Results: Study was conducted from August to October 2024. Total 101 people were respondent of the study. Data were collected and analyzed through SPSS software. It was found that out of 101 people 82 people had knowledge that it’s a mosquito borne alpha virus causes Chikungunya and it can’t be spread through casual contact 38 people out of 101 participants physician diagnosed their Chikungunya. Majority of the respondent suffered from all symptoms such as fever, headache, joint pain and skin rashes which last within 5 days. Conclusion: This study basic aim is to provide awareness to the people that Chikungunya is not spread through casual contact as it spread through mosquito bite alpha virus, diagnosis through proper lab result is important to start treatment as well as cleaning and maintaining the sanitary and surrounding clean will help in preventing the spread of Chikungunya.

ANALYSES AND DETERMINATION OF THE CHEMICAL COMPOSITIONS OF MOSQUITO REPELLANTS SOLD IN IMO STATE, NIGERIA – INDICATING THEIR LEVELS OF ECO-FRIENDLINESS AND TOXICITY

A lot of persons make use of mosquito repellants in order to be free of mosquito bites irrespective of the aftereffects of these repellants. More serious illnesses other than those infected by mosquitoes seem to arise from some of these repellants. In this research, the chemical composition and safety profile of various chemically synthesized mosquito repellants commonly used in Imo State, Nigeria were carried out. X-ray fluorescence was done to find out the elements present in each. GC-MS analyses were carried out to identify the organic compounds while the ADMET (toxicity) test was followed to evaluate the level of toxicity in each repellant. From the GC-MS analyses, it was deduced that six of the ten types of repellants analyzed contain a non-friendly compound generally known as DEET (Diethyltoluamide). These are medi soft cream with 3.567% of DEET, gardia cream = 22.544%, fly killing bait powder = 7.602%, Rambo coil = 2.822%, reptogel cream = 7.972% and super kill coil = 0.094% all by mass. X-ray done indicated the presence of lead, a harmful element though found at a low concentration in medi soft cream, super kill coil, Swan Green coil, Rambo paper, Rambo coil, odomos cream and fly killing bait powder. Sulphur too detected in Rambo powder, Rambo coil and reptogel cream seems not threatening. Considering the ADMET test, it reveals that most of these repellant are not safe especially when applied for long as each of their prediction toxicity does not correspond to a manageable extent to the DrugBank% database. Odomos cream with no DEET and no elemental sulphur may be less toxic as its toxicity prediction tallies more with the DrugBank% data base. This research therefore recommends that the use of chemical mosquito repellants be discouraged till the producers get back to the drawing board. Natural repellants could be resorted to.

Expert System for Diagnosing Dengue Fever with Comparison of Naïve Bayes and Dempster Shafer Methods

An expert system for diagnosing dengue fever (DF) using a comparison of the Naive Bayes and Dempster Shafer methods aims to provide a solution to assist medical personnel in diagnosing this disease. Dengue fever is a disease caused by the dengue virus infection through the bite of Aedes mosquitoes. It has symptoms similar to other diseases and requires rapid and accurate diagnosis. The Naive Bayes and Dempster Shafer methods were chosen because both have different approaches to handling uncertainty and imprecise information. The Naive Bayes method is a probability-based classification that assumes independence between features. Meanwhile, Dempster Shafer is an approach to handling uncertainty. Therefore, comparing Naive Bayes and Dempster Shafer allows for classification with structured and fairly straightforward data, offering accuracy and flexibility in dealing with uncertainty. Applying this expert system with these methods can help in the faster and more accurate diagnosis of DF and provide better recommendations in situations where the available data is incomplete or ambiguous. From the test data calculations, the two methods show that the Naive Bayes method has a higher percentage value of 93%, while Dempster Shafer has 86%.

Comparison of EfficientNetB0 and EfficientNetB7 Models in Classifying Malaria Based on Blood Cells

Malaria is a disease caused by the bite of malaria mosquitoes, which spreads through blood. Malaria mosquitoes will spread the Plasmodium parasite through their bites. Early malaria identification is essential so the disease can be prevented immediately. Through data science, which utilizes the CNN model, the classification of blood infected with parasites can be predicted accurately. This research uses data obtained from Kaggle website with 27,558 image samples. The data is divided into two classes, parasite-infected and uninfected, which are then divided again into two types. The first class is training data divided into 80% of the total data and the other 20% as validation data. This research used two test scenarios to obtain a more effective classification model. The first scenario uses Hyperparameter Tuning and the EfficientNetB0 model with classification results of 95%. Meanwhile, the classification achievement for scenario two was 99% by utilizing EfficientNetB7.

Molecular Xenomonitoring (MX) allows real-time surveillance of West Nile and Usutu virus in mosquito populations.

West Nile Virus (WNV) and Usutu virus (USUV) circulate through complex cryptic transmission cycles involving mosquitoes as vectors, birds as amplifying hosts and several mammal species as dead-end hosts. Both viruses can be transmitted to humans through mosquito bites, which can lead to neuroinvasive and potentially fatal disease. Notably, WNV can also be transmitted through blood donations and organ transplants. The high proportion of asymptomatic infections caused by these viruses and their cryptic enzootic circulation make their early detection in the environment challenging. Viral surveillance in France still heavily relies on human and animal surveillance, i.e. late indicators of viral circulation. Entomological surveillance is a method of choice for identifying virus circulation ahead of the first human and animal cases and to reveal their genetic identity, but performing molecular screening of vectors is expensive, and time-consuming. Here we show substantial WNV and USUV co-circulation in Atlantic seaboard of France between July and August 2023 using a non-invasive MX (Molecular Xenomonitoring) method that use trapped mosquito excreta. MX offers significant advantages over traditional entomological surveillance: it is cost-effective and efficient, enabling viral RNA screening from a community of trapped mosquitoes via their excreta, which can be transported at room temperature. Additionally, MX extends the longevity of trapped mosquitoes, enhancing virus detection and simplifying logistics, and is easy to implement without requiring specialized skills. At the crossroads between entomological and environmental surveillance, MX can detect the circulation of zoonotic pathogens in the environment before cases are observed in humans and horses, enabling the timely alerts to health policy makers, allowing them to take suitable control measures.

Phase I/IIa study to assess the safety, immunogenicity and efficacy of ChAdOx1-MVA vectored vaccines expressing a novel liver-stage malaria dual antigen LS2 by sporozoite challenge in malaria-naïve adults

Background Induction of CD8+ T-cells using viral vectors is a promising strategy in developing effective vaccines against pre-erythrocytic malaria. A recent comparative assessment of candidate antigens using this approach in a mouse model had identified Liver Stage Antigen 1 (LSA1) and Liver Stage Associated Protein 2 (LSAP2) as more protective than TRAP and CSP antigens, which have been the dominant focus of clinical testing. We proposed that combining these within a novel dual antigenic insert (LS2), encoded alongside an orthologous immunogenic domain from invariant chain in ChAdOx1, and the F11 promoter in MVA, could translate to protective clinical efficacy against malaria. Methods We conducted a non-randomised, open-label, dose escalation phase I/IIa study in UK adults, vaccinating a small lead-in group with ChAdOx1 LS2 5x109 vp (group 1; n = 3) and subsequently a heterologous prime–boost group with ChAdOx1 LS2 2.5x1010 vp and MVA LS2 2x108 pfu (group 2; n =10). Group 2 volunteers and 6 unvaccinated controls underwent Controlled Human Malaria Infection (CHMI) delivered by mosquito bite and standardized follow-up. Results Vaccination with ChAdOx1 LS2 (both low and full doses) and MVA LS2 were generally well tolerated with solicited symptoms observed similar to previous vectored vaccines and no Severe Adverse Events (SAEs). Immunogenicity of the prime-boost schedule as measured by IFN-γ ELISpot was high showing median response of 4473 SFC/10^6 PBMC at the pertinent pre-challenge timepoint, covering a broad range of potential determinants. All vaccinated volunteers became infected with malaria during CHMI with a median time to diagnosis of 13 days compared to 13.25 days in controls. Conclusions Though this study further indicates ChAd/MVA as a safe, highly effective platform for driving CD8+ responses specific to liver-stage malaria antigens, the promise of LSA1 and LSAP2 as potential candidates shown preclinically has not translated to protection from infection in humans. Clinical Trial Registration ClinicalTrials.gov (Ref: NCT03203421), date of registration, 3rd July 2017.

The evaluation of awareness, attitude, and performance of the residents of Bandar Abbas in relation to preventive behaviors and methods for controlling dengue fever

ObjectiveDengue fever is a rapidly spreading viral disease transmitted by mosquitoes, and it is becoming a global concern. This study aimed to assess the awareness, attitude, and performance of the people in Hormozgan province in carrying out preventive behaviors and dengue fever control methods.MethodThis descriptive-analytical study was conducted in 1401 in Bandar Abbas, Iran. A total of 642 men and women participated in the study, and a researcher-made questionnaire was used to collect data on demographic information, awareness, attitude, and performance. The data were analyzed using descriptive statistics.FindingsThe study included 642 citizens of Bandar Abbas, with the majority being male. The average scores for awareness, attitude, and performance were relatively low, indicating insufficient knowledge and weak preventive behaviors regarding dengue fever.ConclusionThe findings suggest a need for educational programs to increase awareness and preventive behaviors among the citizens, especially in essential areas such as protected coverage against mosquito bites and inspection of water accumulation sites in homes. It is also important for health centers and mass media to provide more information and education about dengue fever and its prevention.

Willingness to pay for a mosquito bite prevention ‘forest pack’ in Cambodia: results of a discrete choice experiment

BackgroundProgress towards malaria elimination in the Greater Mekong Subregion has left much of the residual malaria transmission concentrated among forest-exposed populations for whom traditional domicile focused malaria vector control is unlikely to be effective. New tools to protect these populations from vector biting outdoors are needed.MethodsAlongside implementation research on the deployment of a “forest pack” consisting of a volatile pyrethroid (transfluthrin)-based spatial repellent (VPSR), a picaridin-based topical repellent and etofenprox treatment of clothing, an assessment was made of participant willingness to pay for the forest packs and variants of the packs using a discrete choice experiment.ResultsParticipants showed willingness to pay for forest packs consistent with full-cost recovery for VPSR devices. The inclusion of a full malaria season’s worth of VPSR devices increased the willingness to pay for a forest pack by 15% (p = 0.061). At a price of approximately 10 USD, approximately 50% of participants were willing to pay for a forest pack which included a full season’s worth of VPSR.ConclusionForest packs which include VPSR are likely to be acceptable to the target forest-exposed populations, and those which include VPSR products may even have potential for commercial sales or some cost-recovery.

The effectiveness of putative wearable repellent technologies to protect against mosquito biting and Aedes-borne diseases, and their economic impact.

Viruses transmitted by mosquitoes threaten the health of millions of people worldwide. There is an urgent need for new tools for personal protection to ensure that vulnerable individuals are protected from infectious bites when outdoors. Here, we test the efficacy of wash-in and spray-on repellents against Aedes aegypti. When applied as a treatment on clothing as well as skin, the novel repellent compound delta-undecalactone provided up to 100% protection initially, and over 50% bite prevention for more than 7 hours. Mathematical modelling indicated that if such a repellent, with 100% initial efficacy, were to be applied twice daily by 80% of the population, more than 30% of Zika virus infections could be averted in an outbreak scenario with a basic reproduction number R0 = 2.2. In a less severe outbreak (R0 = 1.6), the same repellent regimen could avert 96% of infections. If there was much lower uptake, with only 40% of people using the repellent twice per day, just 4% of Zika cases would be averted (outbreak R0 = 2.2). Similar results were found in other scenarios tested for dengue and chikungunya outbreaks. Our model can be extrapolated to other repellents and guide future product development, and provides support to the concept that effective repellents that are used regularly and appropriately could be cost-effective interventions to prevent ill health from arboviral diseases.

The effect of novel mosquito bite prevention tools on Anopheles minimus landing and key secondary endpoints: semi-field evaluations in Thailand

BackgroundThe Greater Mekong Subregion (GMS) aims to eliminate all human malaria by 2030 and is making substantial progress toward this goal, with malaria increasingly confined to forest foci. These transmission foci are predominantly inhabited by ethnic minorities, local populations, and rural mobile and migrant populations working in mining and agriculture. The recommendations of the World Health Organization (WHO) on malaria elimination states that small population groups which constitute a large proportion of the malaria transmission reservoir should benefit from targeted strategies to reduce transmission overall. These population groups are exposed to malaria vector bites during the day due to Anopheles daytime biting, and during the night, due to low bed net use and open sleeping structures. Such characteristics limit the effectiveness of the WHO core vector control strategies [indoor residual spraying (IRS), insecticide-treated nets (ITNs)], which target indoor resting and indoor feeding mosquitoes. Interventions that target daytime and outdoor resting or biting mosquitoes, and which complement IRS and ITNs and drug strategies, may hasten a decline in the malaria burden.MethodsThis study evaluated two transfluthrin- and one metofluthrin-based volatile pyrethroid spatial repellents (VPSRs), and etofenprox insecticide-treated clothing (ITC) with and without a topical repellent in a semi-field system (SFS) at two research sites in Thailand, across two trial rounds. The study estimated the protective efficacies of the vector control tools against two pyrethroid-susceptible Anopheles minimus strains in the form of 15 interventions, including a combined VPSR and ITC intervention. The interventions’ modes of action were studied by measuring their impact on mosquito landing, and on key life history traits known to affect vectoral capacity (knockdown, post-exposure blood feeding, and 24-h mortality) using a block-randomized crossover design. The odds ratio (OR) for each intervention compared to the control on each outcome was estimated.ResultsAll interventions substantially reduced An. minimus landings and prevented more than 50% mosquito landings when new (VPSRs) or unwashed (treated clothing). In addition to landing reduction, all interventions decreased post-exposure blood feeding, induced knockdown and increased mortality at 24 h. The VPSR interventions were generally more protective against landing than the treated clothing intervention. The combined intervention (VPSR + ITC) provided the greatest protection overall.ConclusionThis SFS evaluation indicates an effect of these VPSR and ITC interventions in reducing An. minimus landing for the user, and indicates their potential for community protection by secondary modes of action. This study demonstrates the utility of SFS trials in the evaluation of bite prevention tools and emphasizes the need for multiple evaluations at different sites. It also highlights possible sources of biases observed, including the measuring of mosquito landing rather than biting, weather parameters, and low mosquito recapture.

Impact of nighttime human behavior on exposure to malaria vectors and effectiveness of using long-lasting insecticidal nets in the Ethiopian lowlands and highlands

BackgroundEthiopia continues to grapple with a persistent malaria burden, characterized by ongoing transmission and recurrent outbreaks. Human behavior influences both malaria exposure and the effectiveness of vector interventions, complicating malaria control efforts. Implementing tailored strategies that account for the complex interplay between human activities and vector behavior remains a challenge in both high- and low-transmission areas in Ethiopia, particularly for vulnerable highland populations and temporary labor migrants, due to lack of data. The aim of this study was to examine the spatiotemporal patterns of human—mosquito interactions and evaluate the effectiveness and suitability of long-lasting insecticidal nets (LLINs) in settings involving lowland resident populations, seasonal migrant workers and highland communities.MethodsConcurrent human and vector behavior data were collected from high-transmission lowlands (residents and temporary migrant workers) and vulnerable highlands populations. Hourly human behavior observations (HBOs), which examined LLIN use, indoor versus outdoor human presence and sleeping patterns, were paired in a crossover design with mosquito sampling using US Centers for Disease Control light traps (CDC LT) as a proxy for mosquito biting behavior. The study was conducted during the peak (October–December 2022) and minor (March–May 2023) malaria transmission seasons (‘peak’ and ‘minor’) for a total of 368 nights. In the highlands, four villages consisting of eight households per village were selected for surveillance; in the lowlands, four villages consisting of two resident villages and two farm sites with migrant workers, with eight households/structures per village or farm, were used for data collection. CDC LT and HBO data were integrated to evaluate HBO-adjusted human biting rates (HBO-adjusted HBR) of Anopheles mosquitoes.ResultsIn the highland villages, residents predominantly engaged in indoor activities, with their peak activity overlapping with the peak biting hours (1800-2200 hours). A substantial proportion of inhabitants slept indoors without LLINs in the peak and minor seasons (42.8% and 39.2%, respectively). Highland residents were significantly more exposed to malaria vectors indoors (88.4% peak, 88.6% minor) than outdoors during both transmission seasons. In lowland villages, both resident and seasonal migrant worker populations exhibited predominantly outdoor activity, particularly during peak biting hours (1800-2300 hours). Both residents and temporary migrants were significantly more exposed to Anopheles mosquitoes outdoors (resident: 65.0% peak, 67.1% minor; migrant: 70.5% peak, 80.0% minor) than indoors during both transmission seasons. LLIN usage was minimal and offered limited protection, with < 16.63% of person-time spent under nets by resident populations and 10.7% by migrant workers.ConclusionsMalaria control in Ethiopia requires context-specific strategies tailored to diverse ecological settings that consider the impact of human behavior on exposure to Anopheles mosquitoes. Limited LLIN effectiveness, human activities coinciding with peak biting times and minimal LLIN usage create significant protection gaps. Comprehensive control necessitates supplemental tools addressing exposure in all locations and times. In the Ethiopian highlands, where indoor activities predominate, increased LLIN usage combined with targeted indoor residual spraying could reduce transmission. In lowland areas, both residents and seasonal migrant workers face relatively higher outdoor exposure risks, requiring additional measures, such as topical and spatial repellents. We recommend implementing data-driven, hyperlocal approaches based on specific human—vector interactions to enhance malaria control effectiveness across the Ethiopian highlands and lowlands.Graphical

Risk of Aedes-borne diseases in and around the Tanzanian seaport of Tanga despite community members being more concerned about malaria

BackgroundIncreased global trade, while beneficial economically, can also increase the spread of vector-borne diseases, particularly those transmitted by Aedes mosquitoes spreading via trade routes. Given the heightened trade-induced activity at ports of entry, it is particularly crucial to assess the risk of mosquito-borne diseases in these settings. This study compared the risks of Aedes-borne disease in and around the eastern Tanzanian seaport of Tanga.MethodsA 200 m × 200 m grid-based system was used to sample mosquitoes within the port area, and in surrounding areas at 2 km, 2.5 km, and 5 km away, between June and December 2023. We characterized mosquito breeding habitats, collected mosquito larvae using standard dippers and tested susceptibility of raised adult Aedes aegypti populations to different insecticides. Adult mosquitoes were collected using BG sentinel traps (daytime) and Centers for Disease Control (CDC) light traps (night-time). Additionally, more than 200 port users and neighboring residents were surveyed to assess their experiences with and perceptions of mosquito biting and disease risks.ResultsThere were 2931 breeding sites, with (60.8%, n = 1782) positive for Aedes larvae. The percentage of water-holding containers infested with Aedes immatures, i.e., the container index (CI), was highest in the port area (66.2%), and lowest 5 km away (44.6%). The port area also had a greater proportion of temporary breeding sites (64.9%) than did the surrounding areas. The adult mosquito surveys revealed 20,449 mosquito species including: Culex quinquefasciatus (56.2%), Mansonia uniformis (38.6%), Ae. aegypti (5.1%), Anopheles gambiae (0.1%), and Anopheles funestus. Ae. aegypti were more abundant in the port area than in the surrounding areas (P < 0.001), whereas Culex sp., and Mansonia sp., were significantly outside (P < 0.001). Adult Anopheles sp., were found only in the port area, but Anopheles larvae were found both within and outside the port areas. Tests on Ae. aegypti sp., revealed susceptibility to bendiocarb and DDT, and resistance to permethrin. Awareness of mosquito-borne diseases among respondents was high for malaria (64.8%), but low for dengue (26.3%) and Chikungunya (1.7%). Most respondents reported being bothered by mosquitoes mostly at night (53.4%) or in the evening (40.7%). In addition to insecticidal bednets, which are used primarily against malaria, preventive measures for Aedes-borne diseases are limited.ConclusionsThis study identified significant potential risk of Aedes species, specifically Ae. aegypti sp., and associated diseases, but low perception of risk and inadequate personal protection measures in the study area. This low perception of risk highlights the need to improve public knowledge of the transmission and control of Aedes-borne diseases.Graphical

Identifying populations at high risk of malaria: a mixed-methods case–control study to inform targeted interventions in Senegal

BackgroundSenegal has made significant progress in reducing the burden of malaria, but transmission remains highly heterogeneous, with specific population subgroups likely at higher risk. Consultations with the National Malaria Control Programme (NMCP) and a review of available data identified nomadic pastoralists, gold miners, and Koranic school students as potential high-risk populations (HRPs). This study aimed to evaluate whether these populations are at higher risk of malaria and better characterize their exposure patterns to inform the design of targeted intervention strategies.MethodsA mixed-methods study was conducted in the districts of Ranérou, Kaolack, and Saraya between November 2020 and December 2021. A formative assessment including key informant interviews (KII) and focus group discussions (FGD) was conducted with non-HRP and HRP members (nomadic pastoralists, gold miners, Koranic school students). A health facility-based case–control study was then conducted in nine health facilities across the three districts. 501 confirmed malaria cases and 1002 non-malaria controls were frequency matched by age and sex with a ratio of 1:2. A standardized questionnaire was administered to collect sociodemographic information, including occupation, use of malaria prevention measures, mosquito exposure, and travel history. Multivariable logistic regression was used to identify malaria risk factors.ResultsKIIs and FGDs indicated that nomadic pastoralists, gold miners and Koranic school students have high exposure to mosquito bites through outdoor sleeping, spending time outside at night and sleeping in informal structures, with important gaps in the coverage of indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs) and limited access to health services. Compared to controls, cases had higher odds of being a nomadic pastoralist (odds ratio (OR) 4.67 95% CI 1.96–11.11) or gold miner (OR 1.92 95% CI 1.20–3.07). No evidence was found of an association with being a Koranic school student (OR 1.39 95% CI 0.80–2.39).ConclusionsNomadic pastoralists and gold miners in the study areas are at higher risk of malaria. Targeted interventions are needed to cover gaps in malaria prevention coverage and access to health services.

Inhibition of sulfated glycans on the binding of dengue virus envelope protein to heparin.

Dengue viruses (DENV) are transmitted to humans through mosquito bites and infect millions globally. DENV uses heparan sulfate (HS) for attachment and cell entry by binding the envelope protein to highly sulfated HS on target cells. Therefore, inhibiting the binding between DENV and HS could be a promising strategy for preventing DENV infection. In the current study, the interactions between DENV envelope protein (from Type 2 DENV) and heparin (a surrogate for HS) were analyzed using competition solution SPR. Results demonstrate that heparin binds to DENV envelope protein with high affinity (KD = 8.83 nM). Competitive Solution SPR assays using surface-immobilized heparin and a series of naturally-sourced and semi-synthetic sulfated glycans demonstrated significant inhibitory activity against the binding of DENV envelope proteins to heparin. This study of molecular interactions could provide insights into the development of therapeutics for DENV infection.

Anopheles mosquito exposure is associated with age, gender and bed net use in areas in Uganda experiencing varying malaria transmission intensity.

The number of Anopheles mosquito bites a person receives determines the risk of acquiring malaria and the likelihood of transmitting infections to mosquitoes. We assessed heterogeneity in Anopheles biting and associated factors in two settings in Uganda with different endemicity. Plasmodium falciparum parasites in blood-fed indoor caught Anopheles mosquitoes were quantified using qPCR targeting the Pf18S rRNA gene. Human DNA in dried blood spots from household occupants and mosquito blood meals was profiled using 15 short-tandem repeats (STRs) and analysed using a log-likelihood approach for matching of both single and multi-sourced blood meals and incomplete DNA profiles. The distribution of mosquito bites was non-random; school-age children (5-15 years) and adults (≥16 years) had a mosquito biting rate ratio (BRR) 1.76 (95%CI 1.27-2.44, P < 0.001) and 1.96 (95%CI 1.41-2.73, P < 0.0001) times that of children under 5 years, respectively. Biting rates were lower in bed net users (BRR: 0.80, 95%CI 0.65-0.99, P = 0.042), and higher in males (BRR: 1.30, 95%CI 1.01-1.66, P = 0.043) and individuals infected with P. falciparum (BRR: 1.42, 95%CI 1.03-1.96, P = 0.030), though the latter effect lost statistical significance in sensitivity analyses. Adults and school-age children are at higher risk for receiving mosquito bites and this has implications for the relative importance of demographic populations to onward malaria transmission to mosquitoes. A novel statistical approach allowed us to match multi-sourced mosquito bloodmeals and partially digested mosquito bloodmeals to human individualsParticipant age consistently related to mosquito biting: adults and school-age children had a mosquito biting rate ratio that was ∼2 and ∼1.8 times that of children below 5 years, respectivelyMen received more mosquito bites than women and self-reported bed net use was associated with lower mosquito exposure. Higher mosquito biting rates were observed in individuals infected with Plasmodium falciparum.

Modeling the within-host dynamics of Plasmodium vivax hypnozoite activation: An analysis of the SPf66 vaccine trial

Plasmodium vivax parasites can lie dormant in the liver as hypnozoites, activating weeks to months after sporozoite inoculation to cause relapsing malarial illness. It is not known what biological processes govern hypnozoite activation. We use longitudinal data from the most detailed cohort study ever conducted in an area where both Plasmodium falciparum and P. vivax were endemic to fit a simple within-host mathematical model of P. vivax hypnozoite activation. 1,344 children living on the Thailand-Myanmar border were followed daily for 21 mo. There were 2,504 vivax and 1,164 falciparum malaria symptomatic episodes recorded over 1988 person-years. The model assumes that hypnozoites activate independently at a constant rate ("exponential clock model"). When this model was embedded in a stochastic framework for repeated infectious mosquito bites, with seasonality inferred from the incidence of clinical falciparum malaria episodes, it explained the observed temporal patterns of multiple (up to 13) recurrent vivax malaria episodes. Under this model, we estimate the mean dormancy period for a single hypnozoite to be 6 mo (i.e., a half-life of 4 mo). We use the calibrated within-host model to characterize population-level overdispersion in the risk of relapse, and assess the potential utility of a serological test for radical cure in low transmission settings. We show that mefloquine treatment of falciparum malaria eliminates early vivax relapses; and that there are substantially more P. vivax recurrences than expected under the model following artesunate monotherapy treatment for falciparum malaria. These results suggest that hypnozoites can be activated by symptomatic malarial illness.

Socioeconomic, Demographic, and Behavioral Factors Associated with Dengue Outbreak: An Observational Study from Eastern Uttar Pradesh, India.

Background: Clinical and epidemiological aspects of dengue have extensively been studied in India. However, limited data are available on social and behavioral aspects of dengue outbreak. We aimed to fill this gap and wish to study socioeconomic, demographic, and behavioral factors associated with dengue outbreak in the Gorakhpur region of eastern Uttar Pradesh, India. Methods: This retrospective observational study was conducted among dengue patients discharged from hospital. Data on sociodemographic, economic, and behavioral factors of dengue were collected telephonically using a structured questionnaire. Continuous and categorical variables were reported as mean ± SD and numbers (%), respectively. Logistic regression analysis was done to establish association between patient's characteristics, awareness, and preventive behavior. Results: Age group 19-45 years 156/232, males 159/232, urban residents 142/232, residing in pucca house 187/232, and from lower-income families 149/232 were mostly affected in this outbreak. Patients spent a median of Indian national rupees 20,000 on treatment. Only 10.8% of patients had Ayushman health insurance cards. Awareness about dengue infection was found in∼43% patients. Literates, middle income group, and professionals/semiprofessionals were significantly more aware about dengue disease, mosquito bite, and treatment than their counterparts. Travel history was significantly associated with dengue infection in the males of 19-45 years age group belonging to rural areas. Use of mosquito repellent, nets, wearing full sleeve clothes were significantly less in rural residents while barefoot walking was more frequently observed in this population. Use of mosquito repellent was significantly associated with income, and these were observed more in the middle-income group. Conclusion: People with low education level, residing in urban areas, residing in pucca houses, who travel frequently, and who belong to lower-income groups were majorly affected by this dengue outbreak. Less dengue awareness and not following preventive practices were found in them. Targeted health education campaigns in urban setting could prevent dengue and economic burden on these vulnerable groups.