Dengue virus infection modifies mosquito blood-feeding behavior to increase transmission to the host

DENV2 and ZIKV modulate the feeding behavior of Aedes aegypti by altering the tyrosine-dopamine pathway

Flaviviruses are known for their neurotropic properties and their long-lasting neurological effects. As mosquito-borne viruses, they can persistently infect the central nervous system of mosquitoes without causing symptoms, yet they can alter the physiology and behavior of these insects. However, the molecular mechanisms by which flaviviruses directly influence mosquito feeding behavior remain largely unexplored. Here, we show that dengue virus serotype 2 (DENV2) and Zika virus (ZIKV) elevate mosquito locomotor activity and blood-feeding propensity throughout the day. Untargeted metabolomics identified increased N-acetyl-L-tyrosine levels in virus-infected mosquito heads, which enhanced locomotor activity and blood-feeding efficiency when injected into Aedes aegypti. Virus infection disrupted the circadian rhythm of tyrosine hydroxylase (Aath), a key dopamine synthesis gene, maintaining its consistent elevation of expression throughout the day. Furthermore, DENV2 and ZIKV perturbed the molecular circadian core oscillator in Ae. aegypti. Additionally, mosquitoes injected with L-3,4-dihydroxyphenylalanine exhibited higher locomotor activity and blood-sucking rates. In contrast, knockdown of Aath reduced blood feeding and decreased infection rates in mice bitten by virus-infected mosquitoes. Collectively, our findings elucidate the molecular mechanisms by which DENV2 and ZIKV modulate the physiology and feeding behavior of Ae. aegypti vectors, thereby facilitating the transmission of these viruses.

IMPORTANCE

This study sheds light on how DENV2 and ZIKV affect the feeding behavior of mosquitoes. We discovered the molecular mechanisms that lead to increased movement and blood feeding in mosquitoes by altering neurotransmitter levels and disrupting their internal biological clocks. These findings reveal how these viruses enhance their own transmission by making mosquitoes more active. This research could help in developing strategies to target these processes, ultimately aiding efforts to control the spread of dengue and Zika viruses and reducing the risk of outbreaks.

The impact of blood on vector-borne diseases with emphasis on mosquitoes and sand flies

The impact of blood and its factors on vector-borne diseases is significant and multifaceted yet understudied. While blood is expected to play a central role in transmission, pathogen development, vector behavior, and vector competence, in experimental settings, most studies are developed in the frame of a single, infected blood meal. To effectively combat vector-borne diseases, we need to determine what is the influence of insect blood-feeding behavior on transmission and development of pathogens, toward translation to natural field settings. This review summarizes current findings, highlights key gaps, and outlines future research directions to enhance our understanding of the role of blood in vector-borne disease transmission.

Dengue-mediated changes in the vectorial capacity of Aedes aegypti (Diptera: Culicidae): manipulation of transmission or infection by-product?

An arthropod's vectorial capacity summarizes its disease transmission potential. Life-history traits, such as fecundity or survival, and behavioral traits, such as locomotor activity, host-seeking and feeding behavior, are important components of vectorial capacity. Studies have shown that mosquito-borne pathogens may alter important vectorial capacity traits of their mosquito vectors, thus directly impacting their transmission and epidemic potential. Here, we compile and discuss the evidence supporting dengue-mediated changes in the yellow fever mosquito Aedes aegypti (L.), its primary vector, and evaluate whether the observed effects represent an evolved trait manipulation with epidemiological implications. Dengue infection appears to manipulate essential traits that facilitate vector-host contact, such as locomotor activity, host-seeking, and feeding behavior, but the underlying mechanisms are still not understood. Conversely, life-history traits relevant to vector population dynamics, such as survival, oviposition, and fecundity, appear to be negatively impacted by dengue virus. Overall, any detrimental effects on life-history traits may be a negligible cost derived from the virulence that dengue has evolved to facilitate its transmission by manipulating Ae. aegypti behavior and feeding performance. However, methodological disparities among studies render comparisons difficult and limit the ability to reach well-supported conclusions. This highlights the need for more standardized methods for the research into changes in virus-mediated traits. Eventually, we argue that the effects on life-history traits and behavior outlined here must be considered when assessing the epidemiological impact of dengue or other arbovirus-vector-host interactions.

Gaussian Process Emulation for Modeling Dengue Outbreak Dynamics

Epidemiological models that aim for a high degree of biological realism by simulating every individual in a population are unavoidably complex, with many free parameters, which makes systematic explorations of their dynamics computationally challenging. This study investigates the potential of Gaussian Process emulation to overcome this obstacle. To simulate disease dynamics, we developed an individual-based model of dengue transmission that includes factors such as social structure, seasonality, and variation in human movement. We trained three Gaussian Process surrogate models on three outcomes: outbreak probability, maximum incidence, and epidemic duration. These models enable the rapid prediction of outcomes at any point in the eight-dimensional parameter space of the original model. Our analysis revealed that average infectivity and average human mobility are key drivers of these epidemiological metrics, while the seasonal timing of the first infection can influence the course of the epidemic outbreak. We use a dataset comprising more than 1,000 dengue epidemics observed over 12 years in Colombia to calibrate our Gaussian Process model and evaluate its predictive power. The calibrated Gaussian Process model identifies a subset of municipalities with consistently higher average infectivity estimates, highlighting them as promising areas for targeted public health interventions. Overall, this work underscores the potential of Gaussian Process emulation to enable the use of more complex individual-based models in epidemiology, allowing a higher degree of realism and accuracy that should increase our ability to control important diseases such as dengue.

Aedes albopictus is not an arbovirus aficionado when feeding on cynomolgus macaques or squirrel monkeys

Viruses transmitted by Aedes mosquitoes (e.g., dengue [DENV], Zika [ZIKV]) have demonstrated high potential to spill over from their ancestral, sylvatic cycles in non-human primates to establish transmission in humans. Epidemiological models require accurate knowledge of the contact structure between hosts and vectors, which is highly sensitive to any impacts of virus infection in mosquitoes or hosts on mosquito feeding behavior. Current evidence for whether these viruses affect vector behavior is mixed. Here we leveraged a study on sylvatic DENV-2 and ZIKV transmission between two species of monkey and Aedes albopictus to determine whether virus infection of either host or vector alters vector feeding behavior. Engorgement rates varied from 0% to 100%, but this was not driven by vector nor host infection, but rather by the individual host, host species, and host body temperature. This study highlights the importance of incorporating individual-level heterogeneity of vector biting in arbovirus transmission models.

Activation of innate immunity selectively compromises mitochondrial complex I, proline oxidation, and flight activity in the major arbovirus vector Aedes aegypti

Aedes aegypti females are natural vectors of important arboviruses such as dengue, zika, and yellow fever. Mosquitoes activate innate immune response signaling pathways upon infection, as a resistance mechanism to fight pathogens and limit their propagation. Despite the beneficial effects of immune activation for insect vectors, phenotypic costs ultimately affect their fitness. However, the underlying mechanisms that mediate these fitness costs remain poorly understood. Given the high energy required to mount a proper immune response, we hypothesized that systemic activation of innate immunity would impair flight muscle mitochondrial function, compromising tissue energy demand and flight activity. Here, we investigated the dynamic effects of activation of innate immunity by intra-thoracic zymosan injection on A. aegypti flight muscle mitochondrial metabolism. Zymosan injection significantly increased defensin A expression in fat bodies in a time-dependent manner that compromised flight activity. Although oxidant levels in flight muscle were hardly altered, ATP-linked respiratory rates driven by mitochondrial pyruvate+proline oxidation were significantly reduced at 24 h upon zymosan injection. Oxidative phosphorylation coupling was preserved regardless of innate immune response activation along 24 h. Importantly, rotenone-sensitive respiration and complex I-III activity were specifically reduced 24 h upon zymosan injection. Also, loss of complex I activity compromised ATP-linked and maximal respiratory rates mediated by mitochondrial proline oxidation. Finally, the magnitude of innate immune response activation negatively correlated with respiratory rates, regardless of the metabolic states. Collectively, we demonstrate that activation of innate immunity is strongly associated with reduced flight muscle complex I activity with direct consequences to mitochondrial proline oxidation and flight activity. Remarkably, our results indicate a trade-off between dispersal and immunity exists in an insect vector, underscoring the potential consequences of disrupted flight muscle mitochondrial energy metabolism to arbovirus transmission.

Extrinsic and intrinsic regulation of blood feeding in mosquitoes

Mosquitoes obtain large amounts of blood from hosts in a short period of time. To efficiently obtain high-quality blood without being noticed by the host, mosquitoes sense external factors such as the taste of the host blood and the surrounding environment, and integrate these signals with their own internal information to determine whether to initiate blood feeding and how long to continue feeding. With the development of gene editing and behavior monitoring techniques, the factors that control blood feeding are being identified. Elucidating the factors that contribute to blood feeding is expected to provide new ideas for artificially controlling blood feeding, which has often been overlooked behind host attraction mechanisms. Furthermore, understanding salivary components, mechanisms controlling satiety in feeding, and differences between sugar feeding and blood feeding would help us understand how some mosquitoes have adopted and developed blood feeding over the course of evolution.

Host location by arthropod vectors: are microorganisms in control?

Vector-borne microorganisms are dependent on their arthropod vector for their transmission to and from vertebrates. The 'parasite manipulation hypothesis' states that microorganisms are likely to evolve manipulations of such interactions for their own selective benefit. Recent breakthroughs uncovered novel ecological interactions initiated by vector-borne microorganisms, which are linked to different stages of the host location by their arthropod vectors. Therefore, we give an actualised overview of the various means through which vector-borne microorganisms impact their vertebrate and arthropod hosts to ultimately benefit their own transmission. Harnessing the directionality and underlying mechanisms of these interactions driven by vector-borne microorganisms may provide tools to reduce the spread of pathogenic vector-borne microorganisms.

The Impact of Climate on Human Dengue Infections in the Caribbean

Climate change is no longer a hypothetical problem in the Caribbean but a new reality to which regional public health systems must adapt. One of its significant impacts is the increased transmission of infectious diseases, such as dengue fever, which is endemic in the region, and the presence of the Aedes aegypti mosquito vector responsible for transmitting the disease. (1) Methods: To assess the association between climatic factors and human dengue virus infections in the Caribbean, we conducted a systematic review of published studies on MEDLINE and Web of Science databases according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria. (2) Results: In total, 153 papers were identified, with 27 studies selected that met the inclusion criteria ranging from the northern and southern Caribbean. Rainfall/precipitation and vapor pressure had a strong positive association with dengue incidence, whereas the evidence for the impact of temperatures was mixed. (3) Conclusions: The interaction between climate and human dengue disease in the Caribbean is complex and influenced by multiple factors, including waste management, infrastructure risks, land use changes, and challenged public health systems. Thus, more detailed research is necessary to understand the complexity of dengue within the wider Caribbean and achieve better dengue disease management.

Internal and external drivers interact to create highly dynamic mosquito blood-feeding behaviour

Blood-feeding, which is necessary for most female mosquitoes to reproduce, provides an opportunity for pathogen transmission. Blood-feeding is influenced by external factors such as light, temperature, humidity and intra- and inter-specific interactions. Physiologically, blood-feeding cycles are linked to nutritional conditions and governed by conserved hormonal signalling pathways that prepare mosquito sensory systems to locate and evaluate hosts. Human activities also alter mosquito blood-feeding behaviour through selection pressures such as insecticide usage, habitat and ecosystem alterations, and climate change. Notably, blood-feeding behaviour changes within a mosquito's lifespan, an underexplored phenomenon from an epidemiological standpoint. A review of the literature indicates that our understanding of mosquito biology and blood-feeding behaviour is predominantly based on studies of a handful of primarily tropical species. This focus likely skews our comprehension of the diversity of critical drivers of blood-feeding behaviour, especially under constraints imposed by harsh conditions. We found evidence of remarkable adaptability in blood-feeding and significant knowledge gaps regarding the determinants of host use. Specifically, epidemiological analyses assume host use is modified by external factors, while neglecting internal physiology. Integrating all significant factors is essential for developing effective models of mosquito-borne disease transmission in a rapidly changing world.

An electropenetrography waveform library for the probing and ingestion behaviors of Culex tarsalis on human hands

Culex tarsalis Coquillett (Diptera: Culicidae) mosquitoes are capable of vectoring numerous pathogens affecting public and animal health. Unfortunately, the probing behaviors of mosquitoes are poorly understood because they occur in opaque tissues. Electropenetrography (EPG) has the potential to elucidate these behaviors by recording the electrical signals generated during probing. We used an AC-DC EPG with variable input resistors (Ri levels) to construct a waveform library for Cx. tarsalis feeding on human hands. Biological events associated with mosquito probing were used to characterize waveforms at four Ri levels and with two electrical current types. The optimal settings for EPG recordings of Cx. tarsalis probing on human hands was an Ri level of 107 Ohms using an applied signal of 150 millivolts alternating current. Waveforms for Cx. tarsalis included those previously observed and associated with probing behaviors in Aedes aegypti L. (Diptera: Culicidae): waveform families J (surface salivation), K (stylet penetration through the skin), L (types 1 and 2, search for a blood vessel/ingestion site), M (types 1 and 2, ingestion), N (type 1, an unknown behavior which may be a resting and digestion phase), and W (withdrawal). However, we also observed variations in the waveforms not described in Ae. aegypti, which we named types L3, M3, M4, and N2. This investigation enhances our understanding of mosquito probing behaviors. It also provides a new tool for the automated calculation of peak frequency. This work will facilitate future pathogen acquisition and transmission studies and help identify new pest and disease management targets.

Electropenetrography with Alternating Current Reveals In Situ Changes of Aedes aegypti Probing Behaviors Associated with Dengue Virus Infection

Human infection with dengue virus (DENV) results in significant morbidity and mortality around the world. Current methods to investigate virus-associated changes in insect feeding behaviors are largely restricted to video analysis of feeding events outside of the host or intravital microscopy. Electropenetrography, a method originally developed for plant-feeding insects, offers a promising alternative by allowing high-resolution recording of voltage changes across the insect bite interface. We compared recordings from DENV-infected Aedes aegypti mosquitoes feeding on uninfected mice and uninfected A. aegypti feeding on DENV-infected mice to controls of uninfected A. aegypti feeding on uninfected mice. We found significant mosquito behavioral changes in both DENV-infected groups compared with controls including longer feeding times and longer preingestion probing events for A. aegypti feeding on DENV-infected mice and a higher number of sequential probing events in DENV-infected A. aegypti feeding on uninfected mice. By recording mosquito feeding and probing events beneath the surface of the skin, we have been able to both confirm and add new dimensions to previous findings regarding DENV-associated behavior changes in A. aegypti. This provides a foundation for increasingly in-depth studies focusing on the transmission of the DENV between vectors and hosts.

Dengue Virus Infects Human Skin Langerhans Cells through Langerin for Dissemination to Dendritic Cells

Dengue virus (DENV) is the most disease-causative flavivirus worldwide. DENV as a mosquito-borne virus infects human hosts through the skin; however, the initial target cells in the skin remain unclear. In this study, we have investigated whether epidermal Langerhans cells (LCs) play a role in DENV acquisition and dissemination. We have used a human epidermal ex vivo infection model as well as isolated LCs to investigate infection by DENV. Notably, both immature and mature LCs were permissive to DENV infection in vitro and ex vivo, and infection was dependent on C-type lectin receptor langerin because blocking antibodies against langerin significantly reduced DENV infection in vitro and ex vivo. DENV-infected LCs efficiently transmitted DENV to target cells such as dendritic cells. Moreover, DENV exposure increased the migration of LCs from epidermal explants. These results strongly suggest that DENV targets epidermal LCs for infection and dissemination in the human host. These findings could provide potential drug targets to combat the early stage of DENV infection.

Mosquito immune cells enhance dengue and Zika virus dissemination in Aedes aegypti

Mosquito-borne viruses cause more than 400 million annual infections and place over half of the world's population at risk. Despite this importance, the mechanisms by which arboviruses infect the mosquito host and disseminate to tissues required for transmission are not well understood. Here, we provide evidence that mosquito immune cells, known as hemocytes, play an integral role in the dissemination of dengue virus (DENV) and Zika virus (ZIKV) in the mosquito Aedes aegypti. We establish that phagocytic hemocytes are a focal point for virus infection and demonstrate that these immune cell populations facilitate virus dissemination to the ovaries and salivary glands. Additional transfer experiments confirm that virus-infected hemocytes confer a virus infection to non-infected mosquitoes more efficiently than free virus in acellular hemolymph, revealing that hemocytes are an important tropism to enhance virus dissemination in the mosquito host. These data support a "trojan horse" model of virus dissemination where infected hemocytes transport virus through the hemolymph to deliver virus to mosquito tissues required for transmission and parallels vertebrate systems where immune cell populations promote virus dissemination to secondary sites of infection. In summary, this study significantly advances our understanding of virus infection dynamics in mosquitoes and highlights conserved roles of immune cells in virus dissemination across vertebrate and invertebrate systems.

Arbovirus impact on mosquito behavior: the jury is still out

Parasites can manipulate host behavior to enhance transmission, but our understanding of arbovirus-induced changes in mosquito behavior is limited. Here, we explore current knowledge on such behavioral alterations in mosquito vectors, focusing on host-seeking and blood-feeding behaviors. Reviewing studies on dengue, Zika, La Crosse, Sindbis, and West Nile viruses in Aedes or Culex mosquitoes reveals subtle yet potentially significant effects. However, assay heterogeneity and limited sample sizes challenge definitive conclusions. To enhance robustness, we propose using deep-learning tools for automated behavior quantification and stress the need for standardized assays. Additionally, conducting longitudinal studies across the extrinsic incubation period and integrating diverse traits into modeling frameworks are crucial for understanding the nuanced implications of arbovirus-induced behavioral changes for virus transmission dynamics.

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.

Aedes albopictus is not an arbovirus aficionado - Impacts of sylvatic flavivirus infection in vectors and hosts on mosquito engorgement on non-human primates

The contact structure between vertebrate hosts and arthropod vectors plays a key role in the spread of arthropod-borne viruses (arboviruses); thus, it is important to determine whether arbovirus infection of either host or vector alters vector feeding behavior. Here we leveraged a study of the replication dynamics of two arboviruses isolated from their ancestral cycles in paleotropical forests, sylvatic dengue-2 (DENV-2) and Zika (ZIKV), in one non-human primate (NHP) species from the paleotropics (cynomolgus macaques, Macaca fascicularis) and one from the neotropics (squirrel monkeys, Saimiri boliviensis) to test the effect of both vector and host infection with each virus on completion of blood feeding (engorgement) of the mosquito Aedes albopictus. Although mosquitoes were starved and given no choice of hosts, engorgement rates varied dramatically, from 0% to 100%. While neither vector nor host infection systematically affected engorgement, NHP species and body temperature at the time of feeding did. We also interrogated the effect of repeated mosquito bites on cytokine expression and found that epidermal growth factor (EGF) and macrophage migration inhibitory factor (MIF) concentrations were dynamically associated with exposure to mosquito bites. This study highlights the importance of incorporating individual-level heterogeneity of vector biting in arbovirus transmission models.

Evaluation of ultra-low volume treatments on Culex quinquefasciatus (Diptera: Culicidae) abundance and relative age by parity dissection

St. Tammany Parish Mosquito Abatement District relies on ultra-low volume (ULV) insecticides to manage adult Culex quinquefasciatus (Say 1823), the primary vector of West Nile virus in Louisiana, but abundance rarely declines post-treatment. Three field ULV applications each of adulticides containing deltamethrin, naled, or resmethrin were conducted from May through October 2022 to measure efficacy against free-flying Cx. quinquefasciatus. Female mosquitoes trapped before and after treatment were identified, counted, and age-graded by parity dissection. No insecticide applications reduced Cx. quinquefasciatus abundance, but trials with deltamethrin and naled significantly lowered average mosquito age in the area post-treatment. No trials with resmethrin reduced mosquito age, which corroborates laboratory susceptibility data indicating local resistance toward the pyrethroid. These trials establish parity dissections and relative age gradation as a means of measuring treatment success against Cx. quinquefasciatus.

No detectable fitness cost of infection by cell-fusing agent virus in Aedes aegypti mosquitoes

Aedes mosquitoes are well-known vectors of arthropod-borne viruses (arboviruses). Mosquitoes are more frequently infected with insect-specific viruses (ISVs) that cannot infect vertebrates. Some ISVs interfere with arbovirus replication in mosquito vectors, which has gained attention for potential use against arbovirus transmission. Cell-fusing agent virus (CFAV), a widespread ISV, can reduce arbovirus dissemination in Ae. aegypti. However, vectorial capacity is largely governed by other parameters than pathogen load, including mosquito survival and biting behaviour. Understanding how ISVs impact these mosquito fitness-related traits is critical to assess the potential risk of using ISVs as biological agents. Here, we examined the effects of CFAV infection on Ae. aegypti mosquito fitness. We found no significant reduction in mosquito survival, blood-feeding behaviour and reproduction, suggesting that Ae. aegypti is tolerant to CFAV. The only detectable effect was a slight increase in human attraction of CFAV-infected females in one out of eight trials. Viral tolerance is beneficial for introducing CFAV into natural mosquito populations, whereas the potential increase in biting activity must be further investigated. Our results provide the first insight into the link between ISVs and Aedes mosquito fitness and highlight the importance of considering all aspects of vectorial capacity for arbovirus control using ISVs.

AC-DC Electropenetrography as a Tool to Quantify Probing and Ingestion Behaviors of the Yellow Fever Mosquito (Aedes aegypti) on Mice in Biocontainment

A detailed understanding of mosquito probing and ingestion behaviors is crucial in developing novel interventions to interrupt the transmission of important human and veterinary pathogens, but these behaviors are difficult to observe as the mouthparts are inserted into the skin of the host. Electropenetrography (EPG) allows indirect observation, recording, and quantification of probing and ingestion behaviors of arthropods by visualizing the electrical waveform associated with these behaviors. The study of mosquito probing and ingestion behaviors has been limited to the use of human hands as host, which is not suitable for pathogen transmission studies. Mouse models of mosquito-borne diseases are a widely used and indispensable tool in this research, but previous attempts to use direct current EPG to study mosquito probing behaviors on mice have been unsuccessful. Accordingly, the present study used alternating or direct current (AC-DC) EPG to observe the ingestion behaviors of adult Aedes aegypti mosquitoes on a mouse host in real time under BSL-2 containment conditions with enhanced BSL-3 practices. Our results show that waveform families previously identified during Ae. aegypti probing and ingestion on human hands were observed using 100 mV of AC at an input resistance (Ri) of 107 Ohms (Ω) on CD1 mice. This work is a proof of concept for using mouse models for studying mosquito probing and ingestion behaviors with AC-DC EPG. In addition, these data show that the experimental setup used in these experiments is sufficient for conducting studies on mosquito probing and ingestion behaviors under BSL-2 containment conditions enhanced with BSL-3 practices. This work will serve as a foundation for using EPG to investigate the effects of pathogen infection on mosquito probing behaviors and to understand the real-time dynamics of pathogen transmission.

Automated analysis of feeding behaviors of females of the mosquito Aedes aegypti using a modified flyPAD system

Mosquitoes present a global health challenge due to their ability to transmit human and animal pathogens upon biting and blood feeding. The investigation of tastants detected by mosquitoes and their associated feeding behaviors is needed to answer physiological and ecological questions that could lead to novel control methods. A high-throughput system originally developed for research in fruit flies feeding behavior, the flyPAD, was adapted and tested for behaviors associated with the interaction or consumption of liquid diets offered to females of the mosquito Aedes aegypti Liverpool strain. Females were given water, sucrose solution and sheep blood in choice and non-choice assays. The volume ingested was evaluated with fluorescein. The placement of the system on a heated surface allowed blood consumption, and without females puncturing a membrane. The flyPAD system recorded nine feeding behavioral variables, of which the number of sips and number of activity bouts correlated with meal volume ingested for both sucrose solution and blood. The adaptation to mosquitoes of the flyPAD system differentiated feeding behavior variables between two feeding deterrents, capsaicin, and caffeine. The flyPAD has potential to quickly assess diverse tastants in both sucrose and blood and may contribute to characterizing more precisely their mode of action.

Prevalence of dengue virus in Haripur district, Khyber Pakhtunkhwa, Pakistan

Dengue virus (DENV) has caused about 12 large outbreaks in Pakistan, resulting in 286,262 morbidities and 1108 deaths. The most affected province is Khyber Pakhtunkhwa (KP). This study was conducted to determine the average DENV prevalence in different areas of the Haripur endemic district of KP and the causing factors of DENV.

METHODS

This work was a cross-sectional study that was performed in the DENV endemic district Haripur. A total of 761 individuals were included in this study. The data were categorized according to sex, age and symptoms (like fever, body aches, bleeding, and skin rash). For data analysis, SPSS 23 version was applied. ArcGIS version 10.8 was used to map the study area.

RESULTS

In this study, there were 716 confirmed cases of DENV fever, including 421 males (58.8%) and 295 females (41.2%). The most affected age range, 16-30 years, reported by 301 (42.0%), was followed by 31-45 years, 184 (25.7%), above 46 years, 132 (18.4%), and 0-15 years, 99 (13.8%). The positive IgG cases were 581(81.0%). Those whose age ranges from 1 to 15 years 82 (8.7%) cases, 16-30 years 244 (34.1%), 31-45 years 156 (21.8%), above 46-year age 99 (13.8%) cases. In addition, this suggests that those between the ages of 16 and 30 are at the highest risk for DENV infection. However, this might be the fact that individuals in this age range are more likely to be out in the environment, making them more vulnerable to the virus.

CONCLUSION

Over the past ten years, DENV fever has become increasingly prevalent in Pakistan. The risk is substantially higher for males. Dengue outbreaks hit those between the ages of 16 and 30 the hardest. The proper monitoring and assessment of DENV are necessary for prevention and controlling the disease. Disease surveillance includes identification and molecular characterization of infected persons and monitoring mosquito populations in high-risk locations for the purpose of vector surveillance. In order to assess the community's willingness to participate in DENV preventive efforts, behavioral impact surveillance is also necessary.

Contemporary exploitation of natural products for arthropod-borne pathogen transmission-blocking interventions

An integrated approach to innovatively counter the transmission of various arthropod-borne diseases to humans would benefit from strategies that sustainably limit onward passage of infective life cycle stages of pathogens and parasites to the insect vectors and vice versa. Aiming to accelerate the impetus towards a disease-free world amid the challenges posed by climate change, discovery, mindful exploitation and integration of active natural products in design of pathogen transmission-blocking interventions is of high priority. Herein, we provide a review of natural compounds endowed with blockade potential against transmissible forms of human pathogens reported in the last 2 decades from 2000 to 2021. Finally, we propose various translational strategies that can exploit these pathogen transmission-blocking natural products into design of novel and sustainable disease control interventions. In summary, tapping these compounds will potentially aid in integrated combat mission to reduce disease transmission trends.

Flaviviruses hijack the host microbiota to facilitate their transmission

Flaviviruses, such as Dengue and Zika viruses, infect millions of people worldwide using mosquitos as vectors. In this issue of Cell, Zhang et al. reveal how these viruses manipulate the skin microbiome of infected hosts in a way that increases vector recruitment and viral spread. They propose vitamin A as a way to counteract the virus and decrease transmission.

Vector-Borne Viral Diseases as a Current Threat for Human and Animal Health—One Health Perspective

Over the last decades, an increase in the emergence or re-emergence of arthropod-borne viruses has been observed in many regions. Viruses such as dengue, yellow fever, or zika are a threat for millions of people on different continents. On the other hand, some arboviruses are still described as endemic, however, they could become more important in the near future. Additionally, there is a group of arboviruses that, although important for animal breeding, are not a direct threat for human health. Those include, e.g., Schmallenberg, bluetongue, or African swine fever viruses. This review focuses on arboviruses and their major vectors: mosquitoes, ticks, biting midges, and sandflies. We discuss the current knowledge on arbovirus transmission, ecology, and methods of prevention. As arboviruses are a challenge to both human and animal health, successful prevention and control are therefore only possible through a One Health perspective.