Potential of Aedes albopictus to cause the emergence of arboviruses in Morocco

Entomological risk assessment for transmission of arboviral diseases by Aedes mosquitoes in a domestic and forest site in Accra, Ghana

Dengue, Zika and chikungunya are Aedes-borne viral diseases that have become great global health concerns in the past years. Several countries in Africa have reported outbreaks of these diseases and despite Ghana sharing borders with some of these countries, such outbreaks are yet to be detected. Viral RNA and antibodies against dengue serotype-2 have recently been reported among individuals in some localities in the regional capital of Ghana. This is an indication of a possible silent transmission ongoing in the population. This study, therefore, investigated the entomological transmission risk of dengue, Zika and chikungunya viruses in a forest and domestic population in the Greater Accra Region, Ghana. All stages of the Aedes mosquito (egg, larvae, pupae and adults) were collected around homes and in the forest area for estimation of risk indices. All eggs were hatched and reared to larvae or adults for morphological identification together with larvae and adults collected from the field. The forest population had higher species richness with 7 Aedes species. The predominant species of Aedes mosquitoes identified from both sites was Aedes aegypti (98%). Aedes albopictus, an important arbovirus vector, was identified only in the peri-domestic population at a prevalence of 1.5%, significantly higher than previously reported. All risk indices were above the WHO threshold except the House Index for the domestic site which was moderate (19.8). The forest population recorded higher Positive Ovitrap (34.2% vs 26.6%) and Container (67.9% vs 36.8%) Indices than the peri-domestic population. Although none of the mosquito pools showed the presence of dengue, chikungunya or Zika viruses, all entomological risk indicators showed that both sites had a high potential arboviral disease transmission risk should any of these viruses be introduced. Continuous surveillance is recommended in these and other sites in the Metropolis to properly map transmission risk areas to inform outbreak preparedness strategies.

Aedes albopictus invasion across Africa: the time is now for cross-country collaboration and control

The distribution of Aedes albopictus across west Africa is well documented. However, little has been done to synthesise data and establish the current distribution of this invasive vector in central and east Africa. In this Viewpoint, we show that A albopictus is establishing across Africa, how this is potentially related to urbanisation, and how establishment poses risks of near-term increases in arbovirus transmission. We then use existing species distribution maps for A albopictus and Aedes aegypti to produce consensus estimates of suitability and make these estimates accessible. Although urban development and increased trade have economic and other societal gains, the resulting potential changes in Aedes-borne virus epidemiology require a discussion of how cross-country collaboration and mitigation could be facilitated. Failure to respond to species invasion could result in increased transmission of Aedes-associated pathogens, including dengue, chikungunya, and Rift Valley fever viruses.

Arboviral disease outbreaks, Aedes mosquitoes, and vector control efforts in the Pacific

Recurring outbreaks of mosquito-borne diseases, like dengue, in the Pacific region represent a major biosecurity risk to neighboring continents through potential introductions of disease-causing pathogens. Aedes mosquitoes, highly prevalent in this region, are extremely invasive and the predominant vectors of multiple viruses including causing dengue, chikungunya, and Zika. Due to the absence of vaccines for most of these diseases, Aedes control remains a high priority for public health. Currently, international organizations put their efforts into improving mosquito surveillance programs in the Pacific region. Also, a novel biocontrol method using Wolbachia has been tried in the Pacific region to control Aedes mosquito populations. A comprehensive understanding of mosquito biology is needed to assess the risk that mosquitoes might be introduced to neighboring islands in the region and how this might impact arboviral virus transmission. As such, we present a comprehensive review of arboviral disease outbreak records as well as Aedes mosquito biology research findings relevant to the Pacific region collected from both non-scientific and scientific sources.

Is Asian tiger mosquito (Aedes albopictus) going to become homodynamic in Southern Europe in the next decades due to climate change?

The Asian tiger mosquito, Aedes albopictus, competent vector of several arboviruses, poses significant impact on human health worldwide. Although global warming is a driver of A . albopictus range expansion, few studies focused on its effects on homodynamicity (i.e. the ability to breed all-year-round), a key factor of vectorial capacity and a primary condition for an Aedes-borne disease to become endemic in temperate areas. Data from a 4-year monitoring network set in Central Italy and records from weather stations were used to assess winter adult activity and weekly minimum temperatures. Winter oviposition occurred in 38 localities with a seasonal mean photoperiod of 9.7 : 14.3 (L : D) h. Positive collections (87) occurred with an average minimum temperature of the two and three weeks before sampling of approximately 4°C. According to these evidences and considering the climate projections of three global climate models and three shared socio-economic pathways for the next three 20-year periods (from 2021 to 2080), the minimum temperature of January will increase enough to allow an all-year-round oviposition of A . albopictus in several areas of the Mediterranean Basin. Due to vector homodynamicity, Aedes-borne diseases could become endemic in Southern Europe by the end of the twenty-first century, worsening the burden on human health.

Mosquito Vectors (Diptera: Culicidae) and Mosquito-Borne Diseases in North Africa

Mosquitoes (Diptera: Culicidae) are of significant public health importance because of their ability to transmit major diseases to humans and animals, and are considered as the world's most deadly arthropods. In recent decades, climate change and globalization have promoted mosquito-borne diseases' (MBDs) geographic expansion to new areas, such as North African countries, where some of these MBDs were unusual or even unknown. In this review, we summarize the latest data on mosquito vector species distribution and MBDs affecting both human and animals in North Africa, in order to better understand the risks associated with the introduction of new invasive mosquito species such as Aedes albopictus. Currently, 26 mosquito species confirmed as pathogen vectors occur in North Africa, including Aedes (five species), Culex (eight species), Culiseta (one species) and Anopheles (12 species). These 26 species are involved in the circulation of seven MBDs in North Africa, including two parasitic infections (malaria and filariasis) and five viral infections (WNV, RVF, DENV, SINV and USUV). No bacterial diseases have been reported so far in this area. This review may guide research studies to fill the data gaps, as well as helping with developing effective vector surveillance and controlling strategies by concerned institutions in different involved countries, leading to cooperative and coordinate vector control measures.

Comodulation of Dengue and Chikungunya Virus Infection During a Coinfection Scenario in Human Cell Lines

The Dengue virus (DENV) and Chikungunya virus (CHIKV) are the arboviruses that pose a threat to global public health. Coinfection and antibody-dependent enhancement are major areas of concern during DENV and CHIKV infections, which can alter the clinical severity. Acute hepatic illness is a common manifestation and major sign of disease severity upon infection with either dengue or chikungunya. Hence, in this study, we characterized the coexistence and interaction between both the viruses in human hepatic (Huh7) cells during the coinfection/superinfection scenario. We observed that prior presence of or subsequent superinfection with DENV enhanced CHIKV replication. However, prior CHIKV infection negatively affected DENV. In comparison to monoinfection, coinfection with both DENV and CHIKV resulted in lower infectivity as compared to monoinfections with modest suppression of CHIKV but dramatic suppression of DENV replication. Subsequent investigations revealed that subneutralizing levels of DENV or CHIKV anti-sera can respectively promote the ADE of CHIKV or DENV infection in FcγRII bearing human myelogenous leukemia cell line K562. Our observations suggest that CHIKV has a fitness advantage over DENV in hepatic cells and prior DENV infection may enhance CHIKV disease severity if the patient subsequently contracts CHIKV. This study highlights the natural possibility of dengue-chikungunya coinfection and their subsequent modulation in human hepatic cells. These observations have important implications in regions where both viruses are prevalent and calls for proper management of DENV-CHIKV coinfected patients.

Catalogue of the Diptera (Insecta) of Morocco— an annotated checklist, with distributions and a bibliography

The faunistic knowledge of the Diptera of Morocco recorded from 1787 to 2021 is summarized and updated in this first catalogue of Moroccan Diptera species. A total of 3057 species, classified into 948 genera and 93 families (21 Nematocera and 72 Brachycera), are listed. Taxa (superfamily, family, genus and species) have been updated according to current interpretations, based on reviews in the literature, the expertise of authors and contributors, and recently conducted fieldwork. Data to compile this catalogue were primarily gathered from the literature. In total, 1225 references were consulted and some information was also obtained from online databases. Each family was reviewed and the checklist updated by the respective taxon expert(s), including the number of species that can be expected for that family in Morocco. For each valid species, synonyms known to have been used for published records from Morocco are listed under the currently accepted name. Where available, distribution within Morocco is also included. One new combination is proposed: Assuaniamelanoleuca (Séguy, 1941), comb. nov. (Chloropidae).

Aedes albopictus abundance and phenology along an altitudinal gradient in Lazio region (central Italy)

Background

The Asian tiger mosquito Aedes albopictus (Skuse 1894), which is native to Southeast Asia, is among the top 100 invasive species worldwide and one of the most troubling vector species. It has become established in more than 20 European countries. Since its arrival in Italy in the 1990s, the species has colonized all the regions of the country, up to an altitude of 600 m. Nevertheless, no thorough investigation has ever been performed to confirm or extend its elevation limit (EL) in Italy.

Methods

To define the EL of Ae. albopictus and analyse its phenology along an altitudinal gradient, we carried out an investigation by means of ovitraps placed in Lazio region, central Italy. Sampling was performed on a weekly basis in 13 villages within five 200-m altitudinal ranges [0–1000 m above sea level (asl)], with the addition of higher localities to the species range whenever the species was recorded in the highest range.

Results

Aedes albopictus has colonized sites well beyond its known EL, with established populations at 900 m asl and positive ovitraps recorded at 1193 m asl. The relationship between egg abundance and elevation was described by an exponential decay regression, which predicted an EL for oviposition at 1015 m asl. In the active season, egg-laying started earlier at low altitude and ended earlier within the highest altitudinal range. Aedes albopictus abundance and activity period (number of days active) decreased, respectively, by 95% and 34% from the lowest to the highest altitudinal range.

Conclusions

Using data from the present study, the altitudinal limit of Ae. albopictus in central Italy was updated from 600 to 900 m asl. In addition, established populations were predicted to exist up to 1015 m asl. Considering that up to 99.5% of Lazio region’s inhabitants could potentially be affected by Aedes-borne virus outbreaks, the surveillance area for Ae. albopictus should be expanded accordingly. However, our results also indicate that Ae. albopictus surveillance programs need to be revised in order to harmonize the resources earmarked for these with the altitudinal changes in the phenology of this species.

Graphical abstract

The tiger mosquito in Lebanon two decades after its introduction: A growing health concern

The tiger mosquito was introduced to the Eastern region of the Mediterranean basin more than twenty years ago. In Lebanon, it was first observed in 2002 in a limited number of locations mainly from the coastal area of the country. In the absence of national entomological control program, this invasive mosquito became an established species and is now considered in many localities, a source of nuisance because of its human biting behavior. Several entomological surveys were conducted to monitor the geographic spread and the seasonal dynamics of Aedes albopictus by collecting adult stages and by monitoring oviposition activity. Moreover, its susceptibility to the common groups of insecticides was assessed using WHO standard bioassays. Previous vector competence studies revealed that local strains were able to transmit Chikungunya and Dengue viruses. Due to the increased risk of Zika virus introduction in the country, we determined the competence of local populations to transmit this virus. Mapping results showed that Ae. albopictus is mainly spread in the relatively humid western versant of the Mount Lebanon chain reaching 1000m altitude, while it is absent from arid and semi-arid inland areas. Besides, this mosquito is active during 32 weeks from spring till the end of autumn. Local strains of the tiger mosquito are susceptible to pyrethroids and carbamates but resistant to organophosphates and organochlorines. They showed ability to transmit Zika virus; however, only 9% of females were capable to excrete the virus in their saliva at day 28 post infection. Current and previous observations highlight the need to establish a surveillance system in order to control this mosquito and monitor the potential introduction of related diseases.

Aedes albopictus, also called the tiger mosquito, is one the most invasive mosquito species worldwide. It is originated from South-East Asia and islands of the Pacific and Indian oceans and is known to be able to transmit to humans many viral diseases. During the last four decades it succeeded to invade many countries in all continents through an increasing international trade and travel. This mosquito was first observed in Lebanon, in the Middle East region, in 2002. Previous studies revealed that the introduced mosquito was able to transmit Chikungunya and Dengue viruses under experimental conditions. Therefore, it represents a health threat for the Lebanese population. In this study, the authors assessed the status of the tiger mosquito in the country two decades after its first record. They showed that it is widespread in the humid and sub-humid regions of Mount Lebanon chain and is active from spring through late autumn. The authors experimentally demonstrated the ability of this mosquito to transmit Zika virus, a virus that is highly likely to get introduced to Lebanon due to important population flow from South America to the country during the summer season. Finally, the authors found that local populations of tiger mosquito were susceptible to insecticides of the pyrethroids and carbamates groups but resistant to those of the organochlorines and organophosphates groups. The generated information should help national health authorities to establish a targeted surveillance and control strategies for this mosquito.

First Record of Natural Transovarial Transmission of Dengue Virus in Aedes albopictus from Cuba

Transovarial transmission (TOT) of dengue virus (DENV) in Aedes spp. is an important mechanism for DENV maintenance in nature and may be important in initiating outbreaks. The objective of this study was to explore the occurrence of TOT in wild Aedes albopictus populations in Cuba. Mosquito larvae were collected in Cotorro municipality, Havana, Cuba, and identified to species. Fifteen pools of Ae. albopictus each containing 30 larvae were processed for DENV detection by using conventional reverse transcription polymerase chain reaction (RT-PCR) and nested PCR. Four out of 15 pools processed were positive for DENV-3, but no other DENV serotype was detected. This is the first time TOT of DENV detected in Cuban field populations of Ae. albopictus, and this suggests that this species may be an important vector of DENV in Cuba.

Minireview: Epidemiological impact of arboviral diseases in Latin American countries, arbovirus-vector interactions and control strategies

Mosquitoes are the most crucial insects in public health due to their vector capacity and competence to transmit pathogens, including arboviruses, bacterias and parasites. Re-emerging and emerging arboviral diseases, such as yellow fever virus (YFV), dengue virus (DENV), zika virus (ZIKV), and chikungunya virus (CHIKV), constitute one of the most critical health public concerns in Latin America. These diseases present a significant incidence within the human settlements increasing morbidity and mortality events. Likewise, among the different genus of mosquito vectors of arboviruses, those of the most significant medical importance corresponds to Aedes and Culex. In Latin America, the mosquito vector species of YFV, DENV, ZIKV, and CHIKV are mainly Aedes aegypti and Ae. Albopictus. Ae. aegypti is recognized as the primary vector in urban environments, whereas Ae. albopictus, recently introduced in the Americas, is more prone to rural settings. This minireview focuses on what is known about the epidemiological impact of mosquito-borne diseases in Latin American countries, with particular emphasis on YFV, DENV, ZIKV and CHIKV, vector mosquitoes, geographic distribution, and vector-arbovirus interactions. Besides, it was analyzed how climate change and social factors have influenced the spread of arboviruses and the control strategies developed against mosquitoes in this continent.

Modeling and mapping the habitat suitability and the potential distribution of Arboviruses vectors in Morocco

Mosquitoes transmit several agents of diseases and the presence of different species represents a threat to animal and public health. Aedes and Culex mosquitoes are of particular concern giving their potential vector competence for Arbovirus transmission. In Morocco, the lack of detailed information related to their spatial distribution raises major concerns and hampers effective vector surveillance and control. Using maximum entropy (Maxent) modeling, we generated prediction models for the potential distribution of Arboviruses vectors (Aedes aegypti, Ae. vexans, Ae. caspius, Ae. detritus, and Culex pipiens) in Morocco, under current climatic conditions. Also, we investigated the habitat suitability for the potential occurrence and establishment of Ae. albopictus and Ae. vittatus recorded only once in the country. Prediction models for these last two species were generated considering occurrence datasets from close countries of the Mediterranean Basin, where Ae. albopictus is well established, and from a worldwide database for the case of Ae. vittatus (model transferability). With the exception of Ae. vittatus, the results identify potential habitat suitability in Morocco for all mosquitos considered. Existing areas with maximum risk of establishment and high potential distribution were mainly located in the northwestern and central parts of Morocco. Our results essentially underline the assumption that Ae. albopictus, if not quickly controlled, might find suitable habitats and has the potential to become established, especially in the northwest of the country. These findings may help to better understand the potential distribution of each species and enhance surveillance efforts in areas identified as high risk.

Vector Competence for DENV-2 Among Aedes albopictus (Diptera: Culicidae) Populations in China

Aedes albopictus is a vector of over 20 arboviruses that has spread throughout the world, mainly in the second half of the twentieth century. Approximately 50–100 million people are infected with dengue virus (DENV) transmitted by Aedes mosquitoes each year, leading to heavy economic burdens for both governments and individuals, among countless other negative consequences. Understanding the vector competence of vector species is critical for effectively preventing and controlling vector-borne diseases. Accordingly, in this study, vector competence was evaluated by quantitative analysis of DENV-2 loads in mosquito tissues (midguts, heads, and salivary glands) and whole mosquitoes through real-time quantitative polymerase chain reaction (RT-qPCR) analysis. Wolbachia and the expression of immune-associated genes (Rel1, Rel2, Dicer2, and STAT) in mosquitoes were also detected by RT-qPCR to explore their impact on vector competence. The amount of DENV-2 in the mosquito midguts, heads, and salivary glands from southern-western China were found to be lower than those from eastern-central-northern China. The DENV-2 loads in whole mosquitoes showed a negative correlation with Rel1 gene (r = -0.285, P = 0.011) and STAT gene expression levels (r = -0.289, P = 0.009). In terms of Wolbachia strains, the density of the wAlbB strain was found to be significantly higher than that of the wAlbA strain in the eight Ae. albopictus populations, and the relative density of the wAlbB strain in mosquitoes from southern-western China was higher than those from eastern-central-northern China. The relative density of the wAlbB strain showed a negative correlation with the mean loads of DENV-2 in the heads (r = -0.729, P = 0.040), salivary glands (r = -0.785, P = 0.021), and whole mosquitoes (r = -0.909, P = 0.002). Thus, there are lower DENV-2 loads in the mosquitoes from southern-western China, which may be related to the innate immunity of mosquitoes as affected by Rel1 in the Toll pathway, STAT in the JAK-STAT pathway, and the relative density of the wAlbB strain.

Vector Competence of Aedes albopictus Populations from the Northeastern United States for Chikungunya, Dengue, and Zika Viruses

The Asian tiger mosquito (Aedes albopictus) is an important vector of a number of arboviruses, including Zika (ZIKV), dengue (DENV), and chikungunya (CHIKV) viruses, and has recently expanded its range in the eastern United States to southern New England and New York. Given the recent establishment and proliferation of Ae. albopictus in this region and the increasing amount of international travel between the United States and endemic countries, there is a need to elucidate the public health risk posed by this mosquito species in the Northeast. Accordingly, we evaluated the competence of four Ae. albopictus populations from Connecticut and New York, for two strains each of ZIKV, DENV serotype 2 (DENV-2), and CHIKV, currently circulating in the Americas, to evaluate the local transmission risk by this vector. We found that local Ae. albopictus populations are susceptible to infection by all three viruses but are most capable of transmitting CHIKV. Variation in competence was observed for ZIKV and CHIKV, driven by the virus strains and mosquito population, whereas competence was more homogeneous for the DENV-2 strains under evaluation. These results suggest that under optimal circumstances, Ae. albopictus could support localized transmission of these viruses and emphasize the importance of maintaining mosquito surveillance and control programs to suppress Ae. albopictus populations and limit further range expansion of this species.

Microgeographic Wing-Shape Variation in Aedes albopictus and Aedes scapularis (Diptera: Culicidae) Populations

Aedes albopictus and Aedes scapularis are vectors of several arboviruses, including the dengue, chikungunya, and Rocio virus infection. While Ae. albopictus is a highly invasive species native to Asia and has been dispersed by humans to most parts of the world, Ae. scapularis is native to Brazil and is widely distributed in the southeast of the country. Both species are highly anthropophilic and are often abundant in places with high human population densities. Because of the great epidemiological importance of these two mosquitoes and the paucity of knowledge on how they have adapted to different urban built environments, we investigated the microgeographic population structure of these vector species in the city of São Paulo, Brazil, using wing geometric morphometrics. Females of Ae. albopictus and Ae. scapularis were collected in seven urban parks in the city. The right wings of the specimens were removed and digitized, and eighteen landmarks based on vein intersections in the wing venation patterns were used to assess cross-sectional variation in wing shape and size. The analyses revealed distinct results for Ae. albopictus and Ae. scapularis populations. While the former had less wing shape variation, the latter had more heterogeneity, indicating a higher degree of intraspecific variation. Our results indicate that microgeographic selective pressures exerted by different urban built environments have a distinct effect on wing shape patterns in the populations of these two mosquito species studied here.

The recently introduced Aedes albopictus in Tunisia has the potential to transmit chikungunya, dengue and Zika viruses

The mosquito Aedes albopictus was detected for the first time in Tunisia in 2018. With its establishment in the capital city of Tunis, local health authorities fear the introduction of new human arboviral diseases, like what happened in Europe with unexpected local cases of chikungunya, dengue and Zika. Even though this mosquito is competent to transmit the arboviruses mentioned above, the transmission level will vary depending on the couple, mosquito population and virus genotype. Here, we assessed the vector competence of Ae. albopictus Tunisia by experimental infections with chikungunya (CHIKV), dengue (DENV), and Zika (ZIKV) viruses. We found that Ae. albopictus Tunisia was highly competent for CHIKV (transmission efficiency of 25% at 21 post-infection) and to a lesser extent, for ZIKV (8.7%) and DENV (8.3%). Virus was detected in mosquito saliva at day 3 (CHIKV), day 10 (ZIKV) and day 21 (DENV) post-infection. These results suggest that the risk of emergence of chikungunya is the highest imposing a more sustained surveillance to limit Ae. albopictus populations in densely populated urban dwellings and at the entry points of travelers returning from CHIKV-endemic regions.

Contrasted transmission efficiency of Zika virus strains by mosquito species Aedes aegypti, Aedes albopictus and Culex quinquefasciatus from Reunion Island

BACKGROUND

Zika virus (ZIKV) is a mosquito-borne flavivirus that recently emerged in the South Pacific islands and Americas where unprecedented outbreaks were reported. Although Aedes aegypti is considered to be the main vector for ZIKV, other mosquito species have been shown to be potential vectors and differences in vector competence with respect to mosquito strain and ZIKV strain have been demonstrated. In this study we compared the vector competence of three mosquito species Aedes albopictus, Ae. aegypti and Culex quinquefasciatus from Reunion Island for three ZIKV strains.

METHODS

Five mosquito strains (2 strains of Ae. albopictus, 1 of Ae. aegypti and 2 of Cx. quinquefasciatus) were exposed to three ZIKV strains: one African strain (Dak84) and two Asian strains (PaRi_2015 and MAS66). The vector competence parameters (infection rate, dissemination efficiency and transmission efficiency) and viral loads were examined at 14 and 21 days post-infection.

RESULTS

The two Cx. quinquefasciatus strains did not become infected and were therefore unable to either disseminate or transmit any of the three ZIKV strains. Aedes albopictus and Ae. aegypti strains were poorly competent for the two Asian ZIKV strains, while both mosquito species displayed higher infection rates, dissemination and transmission efficiencies for the African ZIKV Dak84 strain. However, this African ZIKV strain was better transmitted by Ae. aegypti as compared to Ae. albopictus.

CONCLUSIONS

Our results show that both Ae. albopictus and Ae. aegypti, from Reunion Island, are more likely to be competent for ZIKV in contrast to Cx. quinquefasciatus which appeared refractory to all tested ZIKV strains. This improves our understanding of the role of mosquito species in the risk of the ZIKV emergence on Reunion Island.

Optimization of convolutional neural network hyperparameters for automatic classification of adult mosquitoes

The economic and social impacts due to diseases transmitted by mosquitoes in the latest years have been significant. Currently, no specific treatment or commercial vaccine exists for the control and prevention of arboviruses, thereby making entomological characterization fundamental in combating diseases such as dengue, chikungunya, and Zika. The morphological identification of mosquitos includes a visual exam of the samples. It is time consuming and requires adequately trained professionals. Accordingly, the development of a new automated method for realizing mosquito-perception and -classification is becoming increasingly essential. Therefore, in this study, a computational model based on a convolutional neural network (CNN) was developed to extract features from the images of mosquitoes and then classify the species Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus. In addition, the model was trained to detect the mosquitoes of the genus Aedes. To train CNNs to perform the automatic morphological classification of mosquitoes, a dataset, which included 7,561 images of the target mosquitoes and 1,187 images of other insects, was acquired. Various neural networks, such as Xception and DenseNet, were used for developing the automatic-classification model based on images. A structured optimization process of random search and grid search was developed to select the hyperparameters set and increase the accuracy of the model. In addition, strategies to eliminate overfitting were implemented to increase the generalization of the model. The optimized model, during the test phase, obtained the balanced accuracy (BA) of 93.5% in classifying the target mosquitoes and other insects and the BA of 97.3% in detecting the mosquitoes of the genus Aedes in comparison to Culex. The results provide fundamental information for performing the automatic morphological classification of mosquito species. Using a CNN-embedded entomological tool is a valuable and accessible resource for health workers and non-taxonomists for identifying insects that can transmit infectious diseases.

The Asian tiger mosquito in Brazil: Observations on biology and ecological interactions since its first detection in 1986

Aedes (Stegomyia) albopictus is a mosquito originating from the Asian continent, which was detected in the Americas in 1985 and Brazil in 1986. Due to its rapid expansion throughout Brazil, this species has already been reported in 26 of the 27 federative units of Brazil. In this review, we evaluate some of the biological, epidemiological and ecological characteristics of Ae. albopictus through critical analysis of their importance in the pathogen transmission dynamics, since its first record in the country. We show that immature forms of this species are frequently found in artificial breeding sites whereas females exhibit anthropophilic behavior despite its eclecticism on blood feeding. In addition, Ae. albopictus shows advantages in interspecific competition with Ae. aegypti for both immature and adult stages. Taking together, these aspects as well as its vector competence indicate that Ae. albopictus could act as a bridge vector between sylvatic and urban pathogen transmission cycles. We conclude by pointing to the need of continuous surveillance of Ae. albopictus in Brazil and raise several questions that still need to be answered.

Evidence of circulation of West Nile virus in Culex pipiens mosquitoes and horses in Morocco

West Nile virus (WNV) is one of the most widely distributed mosquito-borne viruses in the world. In North Africa, it causes human cases of meningoencephalitis with fatalities in Algeria and in Tunisia, whereas only horses were affected in Morocco. The aims of this study were to detect WNV in mosquitoes and to determine seroprevalence of WNV in Moroccan horses by the detection of IgG antibodies. A total of 1455 mosquitoes belonging to four different species were grouped by collection site, date, and sex with 10 specimens per pool and tested for 38 arboviruses using a high-throughput chip based on the BioMark Dynamic array system. Out of 146 mosquito pools tested, one pool was positive for WNV. This positive pool was confirmed by real time RT-PCR. The serosurvey showed that 33.7% (31/92) of horses were positive for competitive enzyme-linked immunosorbent assay (cELISA) test. The flavivirus-sphere microsphere immnoassay (MIA) test, targeting three flaviviruses (WNV, Usutu virus (USUV) and Tick borne encephalitic virus (TBEV)) showed that 23 sera out of 31 were positive for WNV, two for USUV, two for USUV or WNV, and four for an undetermined flavivirus. Virus neutralization tests with USUV and WNV showed that 28 of 31 sera were positive for WNV and all sera were negative for USUV. This study reports, for the first time, the detection of WNV from Culex pipiens mosquitoes in Morocco and its circulation among horses. This highlights that the detection of arboviruses in mosquitoes could serve as an early warning signal of a viral activity to prevent future outbreaks in animals and humans.

A Systematic Review: Is Aedes albopictus an Efficient Bridge Vector for Zoonotic Arboviruses?

Mosquito-borne arboviruses are increasing due to human disturbances of natural ecosystems and globalization of trade and travel. These anthropic changes may affect mosquito communities by modulating ecological traits that influence the “spill-over” dynamics of zoonotic pathogens, especially at the interface between natural and human environments. Particularly, the global invasion of Aedes albopictus is observed not only across urban and peri-urban settings, but also in newly invaded areas in natural settings. This could foster the interaction of Ae. albopictus with wildlife, including local reservoirs of enzootic arboviruses, with implications for the potential zoonotic transfer of pathogens. To evaluate the potential of Ae. albopictus as a bridge vector of arboviruses between wildlife and humans, we performed a bibliographic search and analysis focusing on three components: (1) The capacity of Ae. albopictus to exploit natural larval breeding sites, (2) the blood-feeding behaviour of Ae. albopictus, and (3) Ae. albopictus’ vector competence for arboviruses. Our analysis confirms the potential of Ae. albopictus as a bridge vector based on its colonization of natural breeding sites in newly invaded areas, its opportunistic feeding behaviour together with the preference for human blood, and the competence to transmit 14 arboviruses.

Potential of Aedes albopictus and Aedes aegypti (Diptera: Culicidae) to transmit yellow fever virus in urban areas in Central Africa

Yellow Fever (YF) remains a major public health issue in Sub-Saharan Africa and South America, despite the availability of an effective vaccine. In Africa, most YF outbreaks are reported in West Africa. However, urban outbreaks occurred in 2016 in both Angola and the Democratic Republic of Congo (DRC), and imported cases were reported in Chinese workers coming back from Africa. In Central Africa, Cameroon and the Republic of Congo host a high proportion of non-vaccinated populations increasing the risk of urban outbreaks. The main vector is Aedes aegypti and possibly, Aedes albopictus, both being anthropophilic and domestic mosquitoes. Here, we provide evidence that both Ae. aegypti and Ae. albopictus in Cameroon and the Republic of Congo are able to transmit Yellow fever virus (YFV) with higher rates of infection, dissemination, and transmission for Ae. aegypti. We conclude that the potential of both Aedes species to transmit YFV could increase the risk of urban YF transmission and urge public health authorities to intensify their efforts to control domestic vectors, and extend vaccine coverage to prevent major YFV outbreak.

Zika virus-spread, epidemiology, genome, transmission cycle, clinical manifestation, associated challenges, vaccine and antiviral drug development

Zika Virus (ZIKV) is a Flavivirus transmitted primarily via the bite of infected Aedes aegypti mosquitoes. Globally, 87 countries and territories have recorded autochthonous mosquito-borne transmission of ZIKV as at July 2019 and distributed across four of the six WHO Regions. Outbreaks of ZIKV infection peaked in 2016 and declined substantially throughout 2017 and 2018 in the Americas region. There is the likely risk for ZIKV to spread to more countries. There is also the potential for the re-emergence of ZIKV in all places with prior reports of the virus transmission. The current status of ZIKV transmission and spread is, however, a global health threat, and from the aforementioned, has the potential to re-emerge as an epidemic. This review summarizes the past and present spread of ZIKV outbreak-2007-2019, the genome, transmission cycle, clinical manifestations, vaccine and antiviral drug advancement.

Evolution and biological significance of flaviviral elements in the genome of the arboviral vector Aedes albopictus

Since its genome details are publically available, the mosquito Aedes albopictus has become the central stage of attention for deciphering multiple biological and evolutionary aspects at the root of its success as an invasive species. Its genome of 1,967 Mb harbours an unusual high number of non-retroviral integrated RNA virus sequences (NIRVS). NIRVS are enriched in piRNA clusters and produce piRNAs, suggesting an antiviral effect. Here, we investigated the evolutionary history of NIRVS in geographically distant Ae. albopictus populations by comparing genetic variation as derived by neutral microsatellite loci and seven selected NIRVS. We found that the evolution of NIRVS was far to be neutral with variations both in their distribution and sequence polymorphism among Ae. albopictus populations. The Flaviviral elements AlbFlavi2 and AlbFlavi36 were more deeply investigated in their association with dissemination rates of dengue virus (DENV) and chikungunya virus (CHIKV) in Ae. albopictus at both population and individual levels. Our results show a complex association between NIRVS and DENV/CHIKV opening a new avenue for investigating the functional role of NIRVS as antiviral elements shaping vector competence of mosquitoes to arboviruses.

Low vector competence in sylvatic mosquitoes limits Zika virus to initiate an enzootic cycle in South America

Zika virus (ZIKV) has spread in the Americas since 2015 and the potential establishment of a sylvatic transmission cycle in the continent has been hypothesized. We evaluated vector competence of five sylvatic Neotropical mosquito species to two ZIKV isolates. Distinct batches of Haemagogus leucoceleanus, Sabethes albiprivus, Sabethes identicus, Aedes terrens and Aedes scapularis females were respectively orally challenged and inoculated intrathoracically with ZIKV. Orally challenged mosquitoes were refractory or exhibited low infection rates. Viral dissemination was detected only in Hg. leucocelaenus, but with very low rates. Virus was not detected in saliva of any mosquito orally challenged with ZIKV, regardless of viral isolate and incubation time. When intrathoracically injected, ZIKV disseminated in high rates in Hg. leucocelaenus, Sa. identicus and Sa. albpiprivus, but low transmission was detected in these species; very low dissemination and no transmission was detected in Ae. terrens and Ae. scapularis. Together these results suggest that genetically determined tissue barriers, especially in the midgut, play a vital role in inhibiting ZIKV for transmission in the tested sylvatic mosquito species. Thus, an independent enzootic transmission cycle for ZIKV in South America is very unlikely.

A Survey of Aedes (Diptera: Culicidae) Mosquitoes in Tunisia and the Potential Role of Aedes detritus and Aedes caspius in the Transmission of Zika Virus

The present study aimed to update the list of Aedes mosquito species occurring in Tunisia and to test the vector competence of Aedes (Ochlerotatus) caspius (Pallas) and Ae. (Ochlerotatus) detritus (Haliday), the locally most abundant and widespread species, to transmit Zika virus (ZIKV). In 2017-2018, mosquito larvae were collected from 39 different larval habitats in seven bioclimatic zones of Tunisia. The salinity and pH of each breeding site were measured. The survey revealed the presence of 10 Aedes species in Tunisia: Ae. (Stegomyia) albopictus (Skuse), Ae. (Ochlerotatus) berlandi (Séguy), Ae. caspius, Ae. detritus, Ae. (Finlaya) echinus (Edwards), Ae. (Finlaya) geniculatus (Olivier), Ae. (Acartomyia) mariae (Sergent and Sergent), Ae. (Ochlerotatus) pulcritarsis (Rondani), Ae. (Aedimorphus) vexans (Meigen), and Ae. (Fredwardsius) vittatus (Bigot). Of these 10 species, Ae. caspius and Ae. detritus were the most abundant in Tunisia. Aedes detritus and Ae. caspius larvae were reared until the imago stage under insectary conditions to test autogeny. The study showed that Ae. detritus is autogenous and stenogamous and Ae. caspius, anautogenous and eurygamous. Finally, the collected strains of these two species were experimentally infected with the Asian genotype of ZIKV, originally isolated from a patient in April 2014 in New Caledonia, to test their vector competence. Neither of these species was able to transmit ZIKV at 7 and 14 d postexposure. Further investigations are needed to test the competence of other Tunisian mosquito species that may be associated with ZIKV transmission.