Would the control of invasive alien plants reduce malaria transmission? A review

Morphological characterization of antennal sensilla in Toxorhynchites theobaldi, Toxorhynchites violaceus, and Lutzia bigoti adults: a comparative study using scanning electron microscopy

Some mosquitoes, including species of the genus Toxorhynchites, are known for actively preying on other mosquito larvae, making these predators valuable allies in the fight against vector-borne diseases. A comprehensive understanding of the anatomy and physiology of these potential biological control agents is helpful for the development of effective strategies for controlling vector populations. This includes the antennae, a crucial component in the search for hosts, mating, and selection of oviposition sites. This study utilized scanning electron microscopy to characterize the sensilla on the antennae of adult mosquitoes from two species that are exclusively phytophagous, including Toxorhynchites theobaldi and Toxorhynchites violaceus, as well as Lutzia bigoti, which females are allegedly hematophagous. The types of sensilla in each species were compared, and five basic types of antennal sensilla were identified: trichoid, chaetic, coeloconic, basiconic, and ampullacea. The analysis also found that they were morphologically similar across the three species, regardless of feeding habits or sex. The identification and characterization of basic types of antennal sensilla in T. theobaldi, T. violaceus, and L. bigoti suggest that these structures, which play a crucial role in the behavior and ecology, have common functions across different mosquito species, despite differences in feeding habits or sex.

The economic costs of invasive aquatic plants: A global perspective on ecology and management gaps

Safeguarding aquatic ecosystems from invasive species requires a comprehensive understanding and quantification of their impacts, as this information is crucial for developing effective management strategies. In particular, aquatic invasive plants cause profound alterations to aquatic ecosystem composition, structure and productivity. Monetary cost assessments have, however, lacked at large scales for this group. Here, we synthesize the global economic impacts of aquatic and semi-aquatic invasive plants to describe the distributions of these costs across taxa, habitat types, environments, impacted sectors, cost typologies, and geographic regions. We also examine the development of recorded costs over time using linear and non-linear models and infer the geographical gaps of recorded costs by superimposing cost and species distribution data. Between 1975 and 2020, the total cost of aquatic and semi-aquatic invasive plants to the global economy exceeded US$ 32 billion, of which the majority of recorded costs (57 %) was attributable to multiple or unspecified taxa. Submerged plants had $8.4 billion (25.5 %) followed by floating plants $4.7 billion (14.5 %), emergent $684 million (2.1 %) and semi-aquatic $306 million (0.9 %). Recorded costs were disproportionately high towards freshwater ecosystems, which have received the greatest cost research effort compared to marine and brackish systems. Public and social welfare and fisheries were the sectors most affected, while agriculture and health were most underreported. Cost attributed to management (4.8 %; $1.6 billion) represented only a fraction of damages (85.8 %; $28.2 billion). While recorded costs are rising over time, reporting issues e.g., robustness of data, lack of higher taxonomic resolution and geographical gaps likely have led to a dampening of trajectories. In particular, invasive taxa currently occupy regions where monetary cost reports are lacking despite well-known impacts. More robust and timely cost estimates will enhance interpretation of current and future impacts of aquatic invasive plants, assisting the long-term sustainability of our aquatic ecosystems and associated economic activities.

Public Health Implications of Invasive Plants: A Scientometric Study

Movements of organisms through distinct places can change the dynamics of ecological interactions and make the habitat conducive to the spread of diseases. Faced with a cyclical scenario of invasions and threats in a One Health context, we conducted a scientometric study to understand how disturbances in environments with invaded vegetation affect the incidence of parasites and disease prevalence rates. The search was carried out in Web of Science and Scopus databases, with keywords delimited by Boolean operators and based on the PRISMA protocol. Thirty-sixarticles were full-read to clarify the interaction between diseases and invaded areas. The analysis covered publications from 2005 to 2022, with a considerable increase in the last ten years and a significant participation of the USA on the world stage. Trends were found in scientific activities, and we explored how invasive species can indirectly damage health, as higher concentrations of pathogens, vectors, and hosts were related to structurally altered communities. This paper reveals invaded plants threats that enhance disease transmission risks. It is likely that, with frequent growth in the number of introduced species worldwide due to environmental disturbances and human interventions, the negative implications will be intensified in the coming years.

Natural plant diet impacts phenotypic expression of pyrethroid resistance in Anopheles mosquitoes

Success in reducing malaria transmission through vector control is threatened by insecticide resistance in mosquitoes. Although the proximal molecular mechanisms and genetic determinants involved are well documented, little is known about the influence of the environment on mosquito resistance to insecticides. The aim of this study was to assess the effect of plant sugar feeding on the response of Anopheles gambiae sensu lato to insecticides. Adults were fed with one of four treatments, namely a 5% glucose control solution, nectariferous flowers of Barleria lupulina, of Cascabela thevetia and a combination of both B. lupulina + C. thevetia. WHO tube tests were performed with 0.05% and 0.5% deltamethrin, and knockdown rate (KD) and the 24 h mosquito mortality were measured. Plant diet significantly influenced mosquito KD rate at both concentrations of deltamethrin. Following exposure to 0.05% deltamethrin, the B. lupulina diet induced a 2.5 fold-increase in mosquito mortality compared to 5% glucose. Species molecular identification confirmed the predominance of An. gambiae (60% of the samples) over An. coluzzii and An. arabiensis in our study area. The kdr mutation L1014F displayed an allelic frequency of 0.75 and was positively associated with increased phenotypic resistance to deltamethrin. Plant diet, particularly B. lupulina, increased the susceptibility of mosquitoes to insecticides. The finding that B. lupulina-fed control individuals (i.e. not exposed to deltamethrin) also displayed increased 24 h mortality suggests that plant-mediated effects may be driven by a direct effect of plant diet on mosquito survival rather than indirect effects through interference with insecticide-resistance mechanisms. Thus, some plant species may weaken mosquitoes, making them less vigorous and more vulnerable to the insecticide. There is a need for further investigation, using a wider range of plant species and insecticides, in combination with other relevant environmental factors, to better understand the expression and evolution of insecticide resistance.

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.

Crop protection practices and risks associated with infectious tropical parasitic diseases

Two recent literature reviews have shown that: i) agroecological crop protection (ACP) practices generally reduce risks of viral zoonoses, unlike conventional (agrochemical-based) practices which tend to increase them; ii) substitution-based crop protection (CP) practices (mainly biocontrol-based) could result in fewer health risks from bacterial infectious diseases. Here, we present an analysis of the scientific literature to determine to what extent the conclusions regarding viruses or bacteria can be extended to infectious diseases caused by protozoan or helminthic parasites. This analysis of cases of both vector-transmitted and water- or food-borne parasitic diseases, shows, in terms of reduction of health risks: i) an overall negative effect arising from the use of synthetic plant protection products; ii) the relevance of substitution CP practices not strictly under the ACP banner. On the other hand, the public and veterinary health issue of antiparasitic resistance is not affected by CP practices. The positive effects at the large spatio-temporal scales of ACP approaches remain valid, although to a slightly lesser extent than for bacterial diseases and viral zoonoses, in particular through biodiversity conservation which fosters natural regulations and control, preventing the undesirable effects of synthetic pesticides.

The Prediction of Distribution of the Invasive Fallopia Taxa in Slovakia

Invasive species are now considered the second biggest threat for biodiversity and have adverse environmental, economic and social impacts. Understanding its spatial distribution and dynamics is crucial for the development of tools for large-scale mapping, monitoring and management. The aim of this study was to predict the distribution of invasive Fallopia taxa in Slovakia and to identify the most important predictors of spreading of these species. We designed models of species distribution for invasive species of Fallopia—Fallopia japonica—Japanese knotweed, Fallopia sachalinensis—Sakhalin knotweed and their hybrid Fallopia × bohemica—Czech knotweed. We designed 12 models—generalized linear model (GLM), generalized additive model (GAM), classification and regression trees (CART), boosted regression trees (BRT), multivariate adaptive regression spline (MARS), random forests (RF), support vector machine (SVM), artificial neural networks (ANN), maximum entropy (Maxent), penalized maximum likelihood GLM (GLMNET), domain, and radial basis function network (RBF). The accuracy of the models was evaluated using occurrence data for the presence and absence of species. The final simplified logistic regression model showed the three most important prediction variables lead by distances from roads and rails, then type of soil and distances from water bodies. The probability of invasive Fallopia species occurrence was evaluated using Pearson’s chi-squared test (χ21). It significantly decreases with increasing distance from transport lines (χ21 = 118.85, p < 0.001) and depends on soil type (χ21 = 49.56, p < 0.001) and the distance from the water, where increasing the distance decrease the probability (χ21 = 8.95, p = 0.003).

Can Co-Grazing Waterfowl Reduce Brainworm Risk for Goats Browsing in Natural Areas?

Goats browsing in woodlands, whether for livestock production goals or vegetation management (e.g., targeted grazing to control invasive plants), are at risk of meningeal worm (Parelaphostrongylus tenuis) infection. Indeed, up to 25% incidence has been observed in goats employed in vegetation management. Infection, which occurs via the consumption of an infected gastropod intermediate host, is potentially deadly in goats. We experimentally tested whether co-grazing with waterfowl could reduce goats' exposure via waterfowl consumption of gastropods. Gastropods were sampled in a deciduous woodland before and after the addition of goats alone, goats and waterfowl, or a control with no animal addition. We found that goats browsing on their own increased the abundance of P. tenuis intermediate hosts; however, when goats co-grazed with waterfowl, these increases were not observed. Importantly, waterfowl did not significantly affect overall gastropod abundance, richness, or diversity. Thus, waterfowl co-grazing may effectively reduce goat contact with infectious gastropods without detrimentally affecting the gastropod community. While co-grazing goats with waterfowl may decrease their P. tenuis exposure risk, additional research is needed to confirm whether waterfowl can actually lower P. tenuis incidence.

Assessing the Dynamics of Plant Species Invasion in Eastern-Mediterranean Coastal Dunes Using Cellular Automata Modeling and Satellite Time-Series Analyses

Biological invasion is a major contributor to local and global biodiversity loss, in particular in dune ecosystems. In this study we evaluated current and future cover expansion of the invasive plant species, Heterotheca subaxillaris, and Acacia saligna, in the Mediterranean coastal plain of Israel. This is the first effort to quantify current surface cover of the focal species in this area. We reconstructed plant cover for 1990–2020 using Landsat time series and modeled future potential expansion using cellular automata (CA) modeling. The overall accuracy of the results varied in the range 85–95% and the simulated plant growth using CA varied between 74% and 84%, for A. saligna and H. subaxillaris, respectively. The surface area covered by H. subaxillaris in 2020, 45 years since its introduction, was approximately 81 km2. Acacia saligna covered an area of 74.6 km2, while the vacant area available for potential spread of these two species was 630 km2. Heterotheca subaxillaris showed a mean expansion rate of 107% per decade from 2000 to 2020, while the mean expansion rate of A. saligna was lower, ranging between 48% and 54% within the same time period. Furthermore, based on the plant expansion model simulation we estimated that A. saligna and H. subaxillaris will continue to spread by 60% per decade, on average, from 2020 to 2070, with a maximum growth rate of 80% per decade during 2040–2050. According to future expansion projections, the species will cover all open vacant areas by 2070 (95% of the total vacant area) and most areas will be shared by both species.

Crop protection practices and viral zoonotic risks within a One Health framework

Recent viral zoonotic epidemics have been attributed partially to the negative impact of human activities on ecosystem biodiversity. Agricultural activities, particularly conventional crop protection (CP) practices, are a major threat to global biodiversity, ecosystem health and human health. Here we review interactions between CP practices and viral zoonoses (VZs), the first time this has been done. It should be noted that a) VZs stand at the interface between human, animal and ecosystem health; b) some VZs involve arthropod vectors that are affected by CP practices; and c) some crop pests, or their natural enemies are vertebrate reservoirs/carriers of certain VZs, and their contact with humans or domestic animals is affected by CP practices. Our review encompasses examples highlighting interactions between VZs and CP practices, both efficiency improvement-based (i.e. conventional with agrochemical insecticides and rodenticides), substitution-based (i.e. mainly with physical/mechanical or biopesticidal pest control), and redesign-based (i.e. mainly with conservation biological pest control, including some forms of crop-livestock integration). These CP practices mainly target arthropod and vertebrate pests. They also target, to a lesser extent, weeds and plant pathogens. Conventional and some physical/mechanical control methods and some forms of biopesticidal and crop-livestock integration practices were found to have mixed outcomes in terms of VZ risk management. Conversely, practices based on biological control by habitat conservation of arthropod or vertebrate natural enemies, falling within the Agroecological Crop Protection (ACP) framework, result in VZ prevention at various scales (local to global, and short-term to long-term). ACP addresses major global challenges including climate resilience, biodiversity conservation and animal welfare, and helps integrate plant health within the extended "One Health" concept.

Ecological Countermeasures for Preventing Zoonotic Disease Outbreaks: When Ecological Restoration is a Human Health Imperative

Ecological restoration should be regarded as a public health service. Unfortunately, the lack of quantitative linkages between environmental and human health has limited recognition of this principle. The advent of COVID-19 pandemic provides the impetus for the further discussion. We propose ecological countermeasures as highly targeted, landscape-based interventions to arrest the drivers of land use-induced zoonotic spillover. We provide examples of ecological restoration activities that reduce zoonotic disease risk and a five-point action plan at the human-ecosystem health nexus. In conclusion, we make the case that ecological countermeasures are a tenant of restoration ecology with human health goals. This article is protected by copyright. All rights reserved.

Invasive Alien Plants in Africa and the Potential Emergence of Mosquito-Borne Arboviral Diseases-A Review and Research Outlook

The emergence of arthropod-borne viruses (arboviruses) as linked to land-use changes, especially the growing agricultural intensification and expansion efforts in rural parts of Africa, is of growing health concern. This places an additional burden on health systems as drugs, vaccines, and effective vector-control measures against arboviruses and their vectors remain lacking. An integrated One Health approach holds potential in the control and prevention of arboviruses. Land-use changes favour invasion by invasive alien plants (IAPs) and investigating their impact on mosquito populations may offer a new dimension to our understanding of arbovirus emergence. Of prime importance to understand is how IAPs influence mosquito life-history traits and how this may affect transmission of arboviruses to mammalian hosts, questions that we are exploring in this review. Potential effects of IAPs may be significant, including supporting the proliferation of immature and adult stages of mosquito vectors, providing additional nutrition and suitable microhabitats, and a possible interaction between ingested secondary plant metabolites and arboviruses. We conclude that aspects of vector biology are differentially affected by individual IAPs and that while some plants may have the potential to indirectly increase the risk of transmission of certain arboviruses by their direct interaction with the vectors, the reverse holds for other IAPs. In addition, we highlight priority research areas to improve our understanding of the potential health impacts of IAPs.

Invasive alien plant species: Their impact on environment, ecosystem services and human health

Ecological perturbations caused by biotic invasion have been identified as a growing threat to global sustainability. Invasive alien plants species (IAPS) are considered to be one of the major drivers of biodiversity loss and thereby altering the ecosystem services and socio-economic conditions through different mechanisms. Although the ecological impacts of IAPS are well documented, there is a dearth of studies regarding their economic quantification, livelihood considerations, biotechnological prospects (phytoremediation, bioenergy, phyto-synthesis of nanoparticles, biomedical, industrial applications etc.) and human health risk assessments of IAPS. In this context, the current panoramic review aimed to investigate the environmental, socio-ecological and health risks posed by IAPS as well as the compounded impact of IAPS with habitat fragmentation, climate and land use changes. To this end, the need of an integrated trans-disciplinary research is emphasized for the sustainable management of IAPS. The management prospects can be further strengthened through their linkage with geo-spatial technologies (remote sensing and GIS) by mapping and monitoring the IAPS spread. Further, the horizon of IAPS management is expanded to ecological indicator perspectives of IAPS, biosecurity, and risk assessment protocols with critical discussion. Moreover, positive as well as negative implications of the IAPS on environment, health, ecosystem services and socio-economy (livelihood) are listed so that a judicious policy framework could be developed for the IAPS management in order to mitigate the human health implications.

Sink trap: duckweed and dye attractant reduce mosquito populations

Duckweeds, such as Lemna minor Linnaeus (Alismatales: Lemnaceae), are common in aquatic habitats and have been suggested to reduce larval mosquito survivorship via mechanical and chemical effects. Furthermore, pond dyes are used increasingly in aquatic habitats to enhance their aesthetics, although they have been shown to attract mosquito oviposition. The present study examined the coupled effects of L. minor and black pond dye on the oviposition selectivity of Culex pipiens Linnaeus (Diptera: Culicidae) mosquitoes in a series of laboratory choice tests. Subsequently, using outdoor mesocosms, the combined influence of duckweed and pond dye on mosquito abundances in aquatic habitats was quantified. Mosquitoes were strongly attracted to duckweed, and oviposited significantly greater numbers of egg rafts in duckweed-treated water compared with untreated controls, even when the duckweed was ground. The presence of pond dye interacted with the duckweed and further enhanced positive selectivity towards duckweed-treated water. The presence of duckweed caused significant and sustained reductions in larval mosquito numbers, whereas the relative effects of dye were not evident. The use of floating aquatic plants such as duckweed, combined with dye, may help reduce mosquito populations via the establishment of population sinks, characterized by high rates of oviposition coupled with high levels of larval mortality.

Comprehensive and Durable Modulation of Growth, Development, Lifespan and Fecundity in Anopheles stephensi Following Larval Treatment With the Stress Signaling Molecule and Novel Antimalarial Abscisic Acid

The larval environment of holometabolous insects determines many adult life history traits including, but not limited to, rate and success of development and adult lifespan and fecundity. The ancient stress signaling hormone abscisic acid (ABA), released by plants inundated with water and by leaf and root fragments in water, is likely ubiquitous in the mosquito larval environment and is well known for its wide ranging effects on invertebrate biology. Accordingly, ABA is a relevant stimulus and signal for mosquito development. In our studies, the addition of ABA at biologically relevant levels to larval rearing containers accelerated the time to pupation and increased death of A. stephensi pupae. We could not attribute these effects, however, to ABA-dependent changes in JH biosynthesis-associated gene expression, 20E titers or transcript patterns of insulin-like peptide genes. Adult females derived from ABA-treated larvae had reduced total protein content and significantly reduced post blood meal transcript expression of vitellogenin, effects that were consistent with variably reduced egg clutch sizes and oviposition success from the first through the third gonotrophic cycles. Adult female A. stephensi derived from ABA-treated larvae also exhibited reduced lifespans relative to controls. Collectively, these effects of ABA on A. stephensi life history traits are robust, durable and predictive of multiple impacts of an important malaria vector spreading to new malaria endemic regions.

Leaf inputs from invasive and native plants drive differential mosquito abundances

Ecological impacts of invasive alien species can be unpredictable and simultaneously span multiple habitat types and taxonomic groups. Invasive alien plants can have particularly severe impacts, and plant inputs into aquatic environments can profoundly alter community composition of invertebrates, such as mosquitoes. Here, we examine larval mosquito colonisation of aquatic containers treated with leaves from four different terrestrial plants: the invasive tickberry Lantana camara, invasive guava Psidium guajava, native sycamore fig Ficus sycomorus and native silver cluster-leaf Terminalia sericea. Larval mosquito abundances differed significantly accordingly to leaf treatment, whilst no mosquitoes colonised leaf-free controls. Leaf litter from the invasive L. camara, invasive P. guajava and native F. sycomorus drove significant increases in mosquito abundances relative to native T. sericea. We demonstrate the importance of plant identity for larval mosquito proliferations in aquatic habitats, with changes in plant community composition following terrestrial plant invasions potentially resulting in increased mosquito abundances. In turn, this may have implications for the vectoring of mosquito-borne disease.

Exploring the Relevance of Green Space and Epidemic Diseases Based on Panel Data in China from 2007 to 2016

Urban green space has been proven effective in improving public health in the contemporary background of planetary urbanization. There is a growing body of literature investigating the relationship between non-communicable diseases (NCDs) and green space, whereas seldom has the correlation been explored between green space and epidemics, such as dysentery, tuberculosis, and malaria, which still threaten the worldwide situation of public health. Meanwhile, most studies explored healthy issues with the general green space, public green space, and green space coverage, respectively, among which the different relevance has been rarely explored. This study aimed to examine and compare the relevance between these three kinds of green space and incidences of the three types of epidemic diseases based on the Panel Data Model (PDM) with the time series data of 31 Chinese provinces from 2007 to 2016. The results indicated that there exists different, or even opposite, relevance between various kinds of green space and epidemic diseases, which might be associated with the process of urban sprawl in rapid urbanization in China. This paper provides a reference for re-thinking the indices of green space in building healthier and greener cities.

Attraction of Female Aedes aegypti (L.) to Aphid Honeydew

Plant sugar is an essential dietary constituent for mosquitoes, and hemipteran honeydew is one of the many forms of plant sugar that is important to mosquitoes. Many insects rely on volatile honeydew semiochemicals to locate aphids or honeydew itself. Mosquitoes exploit volatile semiochemicals to locate sources of plant sugar but their attraction to honeydew has not previously been investigated. Here, we report the attraction of female yellow fever mosquitoes, Aedes aegypti, to honeydew odorants from the green peach aphid, Myzus persicae, and the pea aphid, Acyrthosiphon pisum, feeding on fava bean, Vicia faba. We used solid phase micro-extraction and gas chromatography-mass spectrometry to collect and analyze headspace odorants from the honeydew of A. pisum feeding on V. faba. An eight-component synthetic blend of these odorants and synthetic odorant blends of crude and sterile honeydew that we prepared according to literature data all attracted female A. aegypti. The synthetic blend containing microbial odor constituents proved more effective than the blend without these constituents. Our study provides the first evidence for anemotactic attraction of mosquitoes to honeydew and demonstrates a role for microbe-derived odorants in the attraction of mosquitoes to essential plant sugar resources.

Managing mosquitoes and ticks in a rapidly changing world - Facts and trends

Vector-borne diseases transmitted by mosquitoes and ticks are on the rise. The effective and sustainable control of these arthropod vectors is a puzzling challenge for public health worldwide. In the present review, I attempted to provide a concise and updated overview of the current mosquito and tick research scenario. The wide array of control tools recently developed has been considered, with special reference to those approved by the World Health Organization Vector Control Advisory Group (WHO VCAG), as well as novel ones with an extremely promising potential to be exploited in vector control programs. Concerning mosquitoes, a major focus has been given on genetically modified vectors, eave tubes, attractive toxic sugar baits (ATSB) and biocontrol agents. Regarding ticks, the recent development of highly effective repellents and acaricides (including nanoformulated ones) as well as behavior-based control tools, has been highlighted. In the second part of the review, key research questions about biology and control of mosquitoes and ticks have been critically formulated. A timely research agenda outlining hot issues to be addressed in mosquito and tick research is provided. Overall, it is expected that the present review will contribute to boost research and applications on successful mosquito and tick control strategies, along with an improved knowledge of their biology and ecology.