Differential Effects of Temperature and Mosquito Genetics Determine Transmissibility of Arboviruses by Aedes aegypti in Argentina

Identifying Knowledge Gaps through the Systematic Review of Temperature-Driven Variability in the Competence of Aedes aegypti and Ae. albopictus for Chikungunya Virus

Temperature is a well-known effector of several transmission factors of mosquito-borne viruses, including within mosquito dynamics. These dynamics are often characterized by vector competence and the extrinsic incubation period (EIP). Vector competence is the intrinsic ability of a mosquito population to become infected with and transmit a virus, while EIP is the time it takes for the virus to reach the salivary glands and be expectorated following an infectious bloodmeal. Temperatures outside the optimal range act on life traits, decreasing transmission potential, while increasing temperature within the optimal range correlates to increasing vector competence and a decreased EIP. These relatively well-studied effects of other Aedes borne viruses (dengue and Zika) are used to make predictions about transmission efficiency, including the challenges presented by urban heat islands and climate change. However, the knowledge of temperature and chikungunya (CHIKV) dynamics within its two primary vectors-Ae. aegypti and Ae. albopictus-remains less characterized, even though CHIKV remains a virus of public-health importance. Here, we review the literature and summarize the state of the literature on CHIKV and temperature dependence of vector competence and EIP and use these data to demonstrate how the remaining knowledge gap might confound the ability to adequately predict and, thus, prepare for future outbreaks.

The effect of temperature on dengue virus transmission by Aedes mosquitoes

Dengue is prevalent in tropical and subtropical regions. As an arbovirus disease, it is mainly transmitted by Aedes aegypti and Aedes albopictus. According to the previous studies, temperature is closely related to the survival of Aedes mosquitoes, the proliferation of dengue virus (DENV) and the vector competence of Aedes to transmit DENV. This review describes the correlations between temperature and dengue epidemics, and explores the potential reasons including the distribution and development of Aedes mosquitoes, the structure of DENV, and the vector competence of Aedes mosquitoes. In addition, the immune and metabolic mechanism are discussed on how temperature affects the vector competence of Aedes mosquitoes to transmit DENV.

Temperature and transmission of chikungunya, dengue, and Zika viruses: A systematic review of experimental studies on Aedes aegypti and Aedes albopictus

Mosquito-borne viruses are leading causes of morbidity and mortality in many parts of the world. In recent years, modelling studies have shown that climate change strongly influences vector-borne disease transmission, particularly rising temperatures. As a result, the risk of epidemics has increased, posing a significant public health risk. This review aims to summarize all published laboratory experimental studies carried out over the years to determine the impact of temperature on the transmission of arboviruses by the mosquito vector. Given their high public health importance, we focus on dengue, chikungunya, and Zika viruses, which are transmitted by the mosquitoes Aedes aegypti and Aedes albopictus. Following PRISMA guidelines, 34 papers were included in this systematic review. Most studies found that increasing temperatures result in higher rates of infection, dissemination, and transmission of these viruses in mosquitoes, although several studies had differing findings. Overall, the studies reviewed here suggest that rising temperatures due to climate change would alter the vector competence of mosquitoes to increase epidemic risk, but that some critical research gaps remain.

Novel approaches for the rapid development of rationally designed arbovirus vaccines

Vector-borne diseases, including those transmitted by mosquitoes, account for more than 17% of infectious diseases worldwide. This number is expected to rise with an increased spread of vector mosquitoes and viruses due to climate change and man-made alterations to ecosystems. Among the most common, medically relevant mosquito-borne infections are those caused by arthropod-borne viruses (arboviruses), especially members of the genera Flavivirus and Alphavirus. Arbovirus infections can cause severe disease in humans, livestock and wildlife. Severe consequences from infections include congenital malformations as well as arthritogenic, haemorrhagic or neuroinvasive disease. Inactivated or live-attenuated vaccines (LAVs) are available for a small number of arboviruses; however there are no licensed vaccines for the majority of these infections. Here we discuss recent developments in pan-arbovirus LAV approaches, from site-directed attenuation strategies targeting conserved determinants of virulence to universal strategies that utilize genome-wide re-coding of viral genomes. In addition to these approaches, we discuss novel strategies targeting mosquito saliva proteins that play an important role in virus transmission and pathogenesis in vertebrate hosts. For rapid pre-clinical evaluations of novel arbovirus vaccine candidates, representative in vitro and in vivo experimental systems are required to assess the desired specific immune responses. Here we discuss promising models to study attenuation of neuroinvasion, neurovirulence and virus transmission, as well as antibody induction and potential for cross-reactivity. Investigating broadly applicable vaccination strategies to target the direct interface of the vertebrate host, the mosquito vector and the viral pathogen is a prime example of a One Health strategy to tackle human and animal diseases.

Arbovirus Transmission Predictions Are Affected by Both Temperature Data Source and Modeling Methodologies across Cities in Colombia

Weather variables has been described as major drivers of vector proliferation and arbovirus transmission. Among them, temperature has consistently been found to be impactful in transmission dynamics, and models that incorporate temperature have been widely used to evaluate and forecast transmission or arboviruses like dengue, zika, or chikungunya virus. Further, there is growing evidence of the importance of micro-environmental temperatures in driving transmission of Aedes aegypti-borne viruses, as these mosquitoes tend to live within domiciles. Yet there is still a considerable gap in our understanding of how accounting for micro-environmental temperatures in models varies from the use of other widely-used, macro-level temperature measures. This effort combines field-collected data of both indoor and outdoor household associated temperatures and weather station temperature data from three Colombian cities to describe the relationship between the measures representing temperature at the micro- and macro-levels. These data indicate that weather station data may not accurately capture the temperature profiles of indoor micro-environments. However, using these data sources, the basic reproductive number for arboviruses was calculated by means of three modeling efforts to investigate whether temperature measure differences translated to differential transmission predictions. Across all three cities, it was determined that the modeling method was more often impactful rather than the temperature data-source, though no consistent pattern was immediately clear. This suggests that temperature data sources and modeling methods are important for precision in arbovirus transmission predictions, and more studies are needed to parse out this complex interaction.

Global Distribution of Culex tritaeniorhynchus and Impact Factors

Culex tritaeniorhynchus is the primary vector of Japanese encephalitis (JE) and has a wide global distribution. However, the current and future geographic distribution maps of Cx. tritaeniorhynchus in global are still incomplete. Our study aims to predict the potential distribution of Cx. tritaeniorhynchus in current and future conditions to provide a guideline for the formation and implementation of vector control strategies all over the world. We collected and screened the information on the occurrence of Cx. tritaeniorhynchus by searching the literature and online databases and used ten algorithms to investigate its global distribution and impact factors. Cx. tritaeniorhynchus had been detected in 41 countries from 5 continents. The final ensemble model (TSS = 0.864 and AUC = 0.982) indicated that human footprint was the most important factor for the occurrence of Cx. tritaeniorhynchus. The tropics and subtropics, including southeastern Asia, Central Africa, southeastern North America and eastern South America, showed high habitat suitability for Cx. tritaeniorhynchus. Cx. tritaeniorhynchus is predicted to have a wider distribution in all the continents, especially in Western Europe and South America in the future under two extreme emission scenarios (SSP5-8.5 and SSP1-2.6). Targeted strategies for the control and prevention of Cx. tritaeniorhynchus should be further strengthened.

Arbovirus infection in Aedes aegypti from different departments of Colombia

The lack of precise and timely knowledge about the molecular epidemiology of arboviruses of public health importance, particularly in the vector, has limited the comprehensive control of arboviruses. In Colombia and the Americas, entomovirological studies are scarce. Therefore, this study aimed to describe the frequency of natural infection and/or co-infection by Dengue (DENV), Zika (ZIKV), and Chikungunya (CHIKV) in Aedes spp. circulating in different departments of Colombia (Amazonas, Boyacá, Magdalena, and Vichada) and identifying vector species by barcoding. Aedes mosquitoes were collected in departments with reported prevalence or incidence of arbovirus cases during 2020–2021, located in different biogeographic zones of the country: Amazonas, Boyacá, Magdalena, and Vichada. The insects were processed individually for RNA extraction, cDNA synthesis, and subsequent detection of DENV (serotypes DENV1-4 by multiplex PCR), CHIKV, and ZIKV (qRT-PCR). The positive mosquitoes for arboviruses were sequenced (Sanger method) using the subunit I of the cytochrome oxidase (COI) gene for species-level identification. In total, 558 Aedes mosquitoes were captured, 28.1% (n = 157) predominantly infected by DENV in all departments. The serotypes with the highest frequency of infection were DENV-1 and DENV-2 with 10.7% (n = 58) and 14.5% (n = 81), respectively. Coinfections between serotypes represented 3.9% (n = 22). CHIKV infection was detected in one individual (0.2%), and ZIKV infections were not detected. All infected samples were identified as A. aegypti (100%). From the COI dataset (593 bp), high levels of haplotype diversity (H = 0.948 ± 0.012) and moderate nucleotide diversity (π = 0.0225 ± 0.003) were identified, suggesting recent population expansions. Constructed phylogenetic analyses showed our COI sequences’ association with lineage I, which was reported widespread and related to a West African conspecific. We conclude that natural infection in A. aegypti by arbovirus might reflect the country’s epidemiological behavior, with a higher incidence of serotypes DENV-1 and DENV-2, which may be associated with high seroprevalence and asymptomatic infections in humans. This study demonstrates the high susceptibility of this species to arbovirus infection and confirms that A. aegypti is the main vector in Colombia. The importance of including entomovirological surveillance strategy within public health systems to understand transmission dynamics and the potential risk to the population is highlighted herein.

Aedes aegypti and Ae. albopictus microbiome/virome: new strategies for controlling arboviral transmission?

Aedes aegypti and Aedes albopictus are the main vectors of highly pathogenic viruses for humans, such as dengue (DENV), chikungunya (CHIKV), and Zika (ZIKV), which cause febrile, hemorrhagic, and neurological diseases and remain a major threat to global public health. The high ecological plasticity, opportunistic feeding patterns, and versatility in the use of urban and natural breeding sites of these vectors have favored their dispersal and adaptation in tropical, subtropical, and even temperate zones. Due to the lack of available treatments and vaccines, mosquito population control is the most effective way to prevent arboviral diseases. Resident microorganisms play a crucial role in host fitness by preventing or enhancing its vectorial ability to transmit viral pathogens. High-throughput sequencing and metagenomic analyses have advanced our understanding of the composition and functionality of the microbiota of Aedes spp. Interestingly, shotgun metagenomics studies have established that mosquito vectors harbor a highly conserved virome composed of insect-specific viruses (ISV). Although ISVs are not infectious to vertebrates, they can alter different phases of the arboviral cycle, interfering with transmission to the human host. Therefore, this review focuses on the description of Ae. aegypti and Ae. albopictus as vectors susceptible to infection by viral pathogens, highlighting the role of the microbiota-virome in vectorial competence and its potential in control strategies for new emerging and re-emerging arboviruses.

Detection of Flaviviral-Like DNA Sequences in Aedes aegypti (Diptera: Culicidae) Collected From Argentina

Diseases caused by flaviviruses are a major public health burden across the world. In the past decades, South America has suffered dengue epidemics, the re-emergence of yellow fever and St. Louis encephalitis viruses, and the introduction of West Nile and Zika viruses. Many insect-specific flaviviruses (ISFs) that cannot replicate in vertebrate cells have recently been described. In this study, we analyzed field-collected mosquito samples from six different ecoregions of Argentina to detect flaviviruses. We did not find any RNA belonging to pathogenic flaviviruses or ISFs in adults or immature stages. However, flaviviral-like DNA similar to flavivirus NS5 region was detected in 83-100% of Aedes aegypti (L.). Despite being previously described as an ancient element in the Ae. aegypti genome, the flaviviral-like DNA sequence was not detected in all Ae. aegypti samples and sequences obtained did not form a monophyletic group, possibly reflecting the genetic diversity of mosquito populations in Argentina.

Chikungunya Beyond the Tropics: Where and When Do We Expect Disease Transmission in Europe?

Chikungunya virus disease (chikungunya) is a mosquito-borne infectious disease reported in at least 50 countries, mostly in the tropics. It has spread around the globe within the last two decades, with local outbreaks in Europe. The vector mosquito Aedes albopictus (Diptera, Culicidae) has already widely established itself in southern Europe and is spreading towards central parts of the continent. Public health authorities and policymakers need to be informed about where and when a chikungunya transmission is likely to take place. Here, we adapted a previously published global ecological niche model (ENM) by including only non-tropical chikungunya occurrence records and selecting bioclimatic variables that can reflect the temperate and sub-tropical conditions in Europe with greater accuracy. Additionally, we applied an epidemiological model to capture the temporal outbreak risk of chikungunya in six selected European cities. Overall, the non-tropical ENM captures all the previous outbreaks in Europe, whereas the global ENM had underestimated the risk. Highly suitable areas are more widespread than previously assumed. They are found in coastal areas of the Mediterranean Sea, in the western part of the Iberian Peninsula, and in Atlantic coastal areas of France. Under a worst-case scenario, even large areas of western Germany and the Benelux states are considered potential areas of transmission. For the six selected European cities, June–September (the 22th–38th week) is the most vulnerable time period, with the maximum continuous duration of a possible transmission period lasting up to 93 days (Ravenna, Italy).

The Stable Matching Problem in TBEV Enzootic Circulation: How Important Is the Perfect Tick-Virus Match?

Tick-borne encephalitis virus (TBEV), like other arthropod-transmitted viruses, depends on specific vectors to complete its enzootic cycle. It has been long known that Ixodes ricinus ticks constitute the main vector for TBEV in Europe. In contrast to the wide distribution of the TBEV vector, the occurrence of TBEV transmission is focal and often restricted to a small parcel of land, whereas surrounding areas with seemingly similar habitat parameters are free of TBEV. Thus, the question arises which factors shape this focal distribution of TBEV in the natural habitat. To shed light on factors driving TBEV-focus formation, we used tick populations from two TBEV-foci in Lower Saxony and two TBEV-foci from Bavaria with their respective virus isolates as a showcase to analyze the impact of specific virus isolate-tick population relationships. Using artificial blood feeding and field-collected nymphal ticks as experimental means, our investigation showed that the probability of getting infected with the synonymous TBEV isolate as compared to the nonsynonymous TBEV isolate was elevated but significantly higher only in one of the four TBEV foci. More obviously, median viral RNA copy numbers were significantly higher in the synonymous virus–tick population pairings. These findings may present a hint for a coevolutionary adaptation of virus and tick populations.

Evidence of vector borne transmission of Salmonella enterica enterica serovar Gallinarum and fowl typhoid disease mediated by the poultry red mite, Dermanyssus gallinae (De Geer, 1778)

BACKGROUND

The poultry red mite Dermanyssus gallinae (De Geer, 1778) is a major ectoparasite of poultry. Infestations are found in most laying hen farms in Europe, and breeder flocks have also been reported to be affected. Mite infestation has detrimental effects on animal welfare, it causes significant economic losses, and, additionally, D. gallinae is often considered as a vector for pathogens. Despite suspicion of a close relationship between the poultry red mite and Salmonella enterica enterica serovar Gallinarum biovar Gallinarum (serovar Gallinarum), the causative agent of fowl typhoid disease (FT), there has been no definitive proof of mite-mediated transmission. Therefore, an investigation was conducted to determine if D. gallinae-mediated transmission of serovar Gallinarum could be demonstrated among four different hen groups.

METHODS

Two groups of 8 hens (A and B) were experimentally infected with serovar Gallinarum in two isolators. After 7 days, when birds showed signs of FT, about 25,000 mites were introduced. After 3 days, mites were harvested and used to infest two other hen groups of 8 (C and D), in two separate isolators. The health status of hens was constantly monitored; detection and quantification of serovar Gallinarum were performed by PCR and qPCR from mites and organs of dead hens. The maximum likelihood estimation of the infection rate and mite vectorial capacity were calculated.

RESULTS

Clinical disease was observed in groups infected with serovar Gallinarum (A and B) and in hens of groups C and D infested with mites harvested from the isolators containing groups A and B. In all four groups, serovar Gallinarum was detected from liver, spleen, ovary, and cecum of hens, thus confirming the diagnosis of FT. Mite analysis demonstrated the presence of the pathogen, with an estimated infection rate ranging between 13.72 and 55.21 infected per thousand mites. Vectorial capacity was estimated to be 73.79.

CONCLUSIONS

Mites harvested from birds infected with serovar Gallinarum were shown to carry the mite, and then to transfer serovar Gallinarum to isolated groups of pathogen-free birds that subsequently showed signs of FT. Mite vectorial capacity was high, demonstrating that D. gallinae should be considered an effective vector of FT.

The Role of Temperature in Shaping Mosquito-Borne Viruses Transmission

Mosquito-borne diseases having the greatest impact on human health are typically prevalent in the tropical belt of the world. However, these diseases are conquering temperate regions, raising the question of the role of temperature on their dynamics and expansion. Temperature is one of the most significant abiotic factors affecting, in many ways, insect vectors and the pathogens they transmit. Here, we debate the veracity of this claim by synthesizing current knowledge on the effects of temperature on arboviruses and their vectors, as well as the outcome of their interactions.

Zika virus transmission by Brazilian Aedes aegypti and Aedes albopictus is virus dose and temperature-dependent

BACKGROUND

Zika virus (ZIKV) emerged in the Pacific Ocean and subsequently caused a dramatic Pan-American epidemic after its first appearance in the Northeast region of Brazil in 2015. The virus is transmitted by Aedes mosquitoes. We evaluated the role of temperature and infectious doses of ZIKV in vector competence of Brazilian populations of Ae. aegypti and Ae. albopictus.

METHODOLOGY/PRINCIPAL FINDINGS

Two Ae. aegypti (Rio de Janeiro and Natal) and two Ae. albopictus (Rio de Janeiro and Manaus) populations were orally challenged with five viral doses (102 to 106 PFU / ml) of a ZIKV strain (Asian genotype) isolated in Northeastern Brazil, and incubated for 14 and 21 days in temperatures mimicking the spring-summer (28°C) and winter-autumn (22°C) mean values in Brazil. Detection of viral particles in the body, head and saliva samples was done by plaque assays in cell culture for determining the infection, dissemination and transmission rates, respectively. Compared with 28°C, at 22°C, transmission rates were significantly lower for both Ae. aegypti populations, and Ae. albopictus were not able to transmit the virus. Ae. albopictus showed low transmission rates even when challenged with the highest viral dose, while both Ae. aegypti populations presented higher of infection, dissemination and transmission rates than Ae. albopictus. Ae. aegypti showed higher transmission efficiency when taking virus doses of 105 and 106 PFU/mL following incubation at 28°C; both Ae. aegypti and Ae. albopictus were unable to transmit ZIKV with virus doses of 102 and 103 PFU/mL, regardless the incubation temperature.

CONCLUSIONS/SIGNIFICANCE

The ingested viral dose and incubation temperature were significant predictors of the proportion of mosquito's biting becoming infectious. Ae. aegypti and Ae. albopictus have the ability to transmit ZIKV when incubated at 28°C. However Brazilian populations of Ae. aegypti exhibit a much higher transmission potential for ZIKV than Ae. albopictus regardless the combination of infection dose and incubation temperature.

Distinct New York City Aedes albopictus Mosquito Populations Display Differences in Salivary Gland Protein D7 Diversity and Chikungunya Virus Replication

In an increasingly interconnected world, the exposure and subsequent spread of emergent viruses has become inevitable. This is particularly true for Aedes (Ae.) mosquito-vectored viruses, whose range has increased over the past decade from tropical to temperate regions. However, it is unclear if all populations of Ae. mosquitoes in temperate New York City are able to successfully replicate and transmit arboviruses. To answer this question, we reared Ae. albopictus mosquitoes living in a temperate climate from three locations in New York City. We first sequenced the salivary antiviral protein D7 from individual mosquitoes in each population and found single nucleotide variants that are both shared and unique for each Ae. albopictus population. We then fed each population chikungunya virus (CHIKV) via an artificial blood meal. All three mosquito populations could be infected with CHIKV, yet viral titers differed between populations at 7 days post infection. Moreover, we found that these mosquitoes could transmit CHIKV to mice, and that virus RNA reached the saliva as early as two days post infection. Upon sequencing of the saliva CHIKV genomic RNA, we found mutations at sites correlated with increased transmission and virulence. These studies show that NYC Ae. albopictus populations can be infected with and transmit CHIKV, CHIKV is able to evolve in these mosquitoes, and that host salivary factors display population-specific diversity. Taken together, these studies highlight the need to study how distinct mosquito populations control viral infections, both at the virus and host level.

Increased temperatures reduce the vectorial capacity of Aedes mosquitoes for Zika virus

Rapid and significant range expansion of both Zika virus (ZIKV) and its Aedes vector species has resulted in ZIKV being declared a global health threat. Mean temperatures are projected to increase globally, likely resulting in alterations of the transmission potential of mosquito-borne pathogens. To understand the effect of diurnal temperature range on the vectorial capacity of Ae. aegypti and Ae. albopictus for ZIKV, longevity, blood-feeding and vector competence were assessed at two temperature regimes following feeding on infectious blood meals. Higher temperatures resulted in decreased longevity of Ae. aegypti [Log-rank test, χ2, df 35.66, 5, P < 0.001] and a decrease in blood-feeding rates of Ae. albopictus [Fisher's exact test, P < 0.001]. Temperature had a population and species-specific impact on ZIKV infection rates. Overall, Ae. albopictus reared at the lowest temperature regime demonstrated the highest vectorial capacity (0.53) and the highest transmission efficiency (57%). Increased temperature decreased vectorial capacity across groups yet more significant effects were measured with Ae. aegypti relative to Ae. albopictus. The results of this study suggest that future increases in temperature in the Americas could significantly impact vector competence, blood-feeding and longevity, and potentially decrease the overall vectorial capacity of Aedes mosquitoes in the Americas.

The Role of Temperature in Transmission of Zoonotic Arboviruses

We reviewed the literature on the role of temperature in transmission of zoonotic arboviruses. Vector competence is affected by both direct and indirect effects of temperature, and generally increases with increasing temperature, but results may vary by vector species, population, and viral strain. Temperature additionally has a significant influence on life history traits of vectors at both immature and adult life stages, and for important behaviors such as blood-feeding and mating. Similar to vector competence, temperature effects on life history traits can vary by species and population. Vector, host, and viral distributions are all affected by temperature, and are generally expected to change with increased temperatures predicted under climate change. Arboviruses are generally expected to shift poleward and to higher elevations under climate change, yet significant variability on fine geographic scales is likely. Temperature effects are generally unimodal, with increases in abundance up to an optimum, and then decreases at high temperatures. Improved vector distribution information could facilitate future distribution modeling. A wide variety of approaches have been used to model viral distributions, although most research has focused on the West Nile virus. Direct temperature effects are frequently observed, as are indirect effects, such as through droughts, where temperature interacts with rainfall. Thermal biology approaches hold much promise for syntheses across viruses, vectors, and hosts, yet future studies must consider the specificity of interactions and the dynamic nature of evolving biological systems.

European Aedes caspius mosquitoes are experimentally unable to transmit Zika virus

BACKGROUND

Aedes caspius (Pallas, 1771) is a floodwater mosquito species widely distributed in the Western Palaearctic. As an anthropophilic species, its role as an arbovirus vector may be the key for understanding the transmission cycle of certain diseases in Europe such as Zika virus (ZIKV). Concerning vector competence for ZIKV, studies related to Ae. caspius are still scarce. ZIKV is an arbovirus that has provoked a widespread epidemic in the Pacific region (2007-2013) and in the Americas (2015-2016). ZIKV is associated with serious neurological injuries (e.g. microcephaly) and Guillain-Barré syndrome. Due to the ZIKV epidemics in the American continent, some viraemic travellers coming from endemic countries have been reported in Europe. More knowledge is therefore required to define the susceptibility of autochthonous mosquito species such as Ae. caspius for ZIKV in order to improve arbovirus surveillance and control programmes. In the present study, the vector competence of a European population of Ae. caspius was evaluated for two ZIKV lineages, the Suriname ZIKV strain (Asian lineage) and the MR766 ZIKV strain (African I lineage). Females were tested at 7, 14 and 21 days post-exposure (dpe) to infectious blood meals. An Ae. aegypti PAEA strain was used as a positive control.

RESULTS

Aedes caspius presented low susceptibility to ZIKV infection and the virus was only detected by RT-qPCR in body samples. Low viral loads were detected for the MR766 strain at 7 dpe and for the Suriname strain at 14 and 21 dpe. Aedes caspius was unable to produce a disseminated infection and virus transmission at any of the tested time points. Using Ae. aegypti PAEA strain, infection, dissemination and transmission rates were calculated for the Suriname ZIKV strain (Asian lineage) at each time point. For the MR766 ZIKV strain (African I lineage), while only infection rates were estimated at each time point, no dissemination or transmission were detected in either species.

CONCLUSIONS

The results of the present study reveal that the tested Ae. caspius population has a strong midgut escape barrier that limits the dissemination or transmission of the virus. As such, it seems unlikely that European Ae. caspius mosquitoes could be involved in ZIKV transmission if ZIKV was introduced into Europe. This information may help in designing a better strategy to European surveillance and control programmes for ZIKV.

Vector competence of Aedes aegypti for different strains of Zika virus in Argentina

The importance of Zika virus (ZIKV) has increased noticeably since the outbreak in the Americas in 2015, when the illness was associated with congenital disorders. Although there is evidence of sexual transmission of the virus, the mosquito Aedes aegypti is believed to be the main vector for transmission to humans. This species of mosquito has not only been found naturally infected with ZIKV, but also has been the subject of study in many vector competence assays that employ different strains of ZIKV around the world. In Argentina, the first case was reported in February 2016 and a total of 278 autochthonous cases have since been confirmed, however, ZIKV virus has not been isolated from any mosquito species yet in Argentina. In order to elucidate if Argentinian Ae. aegypti populations could be a possible vector of ZIKV, we conducted vector competence studies that involved a local strain of ZIKV from Chaco province, and a Venezuelan strain obtained from an imported case. For this purpose, Ae. aegypti adults from the temperate area of Argentina (Buenos Aires province) were fed with infected blood. Body, legs and saliva were harvested and tested by plaque titration on plates of Vero cells for ZIKV at 7, 11 and 14 days post infection (DPI) in order to calculate infection, transmission, and dissemination rates, respectively. Both strains were able to infect mosquitoes at all DPIs, whereas dissemination and transmission were observed at all DPIs for the Argentinian strain but only at 14 DPI for the Venezuelan strain. This study proves the ability of Ae. aegypti mosquitoes from Argentina to become infected with two different strains of ZIKV, both belonging to the Asian lineage, and that the virus can disseminate to the legs and salivary glands.

Zika virus is a flavivirus transmitted by mosquitoes, isolated for the first time in the Ziika Forest in Uganda in 1947 from a rhesus macaque monkey. The disease is usually asymptomatic, but sometimes it causes a mild illness that comes with fever, rash, joint pain, and conjunctivitis. The World Health Organization focused the attention on this virus after the outbreak in the Americas, when the virus was linked to microcephaly and serious neurological diseases, including Guillain-Barré syndrome. Aedes aegypti was incriminated as the main vector of the virus as it was found both naturally and experimentally infected. This mosquito species was declared eradicated in Argentina by 1970 but re-emerged in 1989. Recent studies found a peculiarity in the genetics of Argentinian Ae. aegypti populations that consists in a combination between both subspecies: Ae. aegypti formosus and Ae. aegypti aegypti. Our study tries to elucidate if Ae. aegypti from Argentina are able to transmit the virus in order to add these mosquitoes to the list of possible vectors of ZIKV and, in future prospect, orient to fight the virus by controlling the vector.

Do we know how mosquito disease vectors will respond to climate change?

Mosquito-borne diseases are on the rise globally. Besides invasion processes and the increasing connectivity between distant regions through the trade of goods and human mobility, climate change is seen as an important driver for changing the likelihood of occurrence of vectors and diseases, respectively. Ectothermic insects respond directly to thermal conditions and thus we can expect them to follow climatic trends. However, a variety of species and different stages in their life cycles need to be considered. Here, we review the current literature in this field and disentangle the state of knowledge and the challenges and open questions for future research. The integration of diurnal temperature ranges in prospective experimental studies will strongly improve the knowledge of mosquitoes’ ecology and mosquito-borne disease transmission for temperate regions in particular. In addition, invasive mosquitoes are known to rapidly adapt to the climatic conditions, but the underlying processes are not yet fully understood.

Aedes-Chikungunya Virus Interaction: Key Role of Vector Midguts Microbiota and Its Saliva in the Host Infection

Aedes mosquitoes are important vectors for emerging diseases caused by arboviruses, such as chikungunya (CHIKV). These viruses’ main transmitting species are Aedes aegypti and Ae. albopictus, which are present in tropical and temperate climatic areas all over the globe. Knowledge of vector characteristics is fundamentally important to the understanding of virus transmission. Only female mosquitoes are able to transmit CHIKV to the vertebrate host since they are hematophagous. In addition, mosquito microbiota is fundamentally important to virus infection in the mosquito. Microorganisms are able to modulate viral transmission in the mosquito, such as bacteria of the Wolbachia genus, which are capable of preventing viral infection, or protozoans of the Ascogregarina species, which are capable of facilitating virus transmission between mosquitoes and larvae. The competence of the mosquito is also important in the transmission of the virus to the vertebrate host, since their saliva has several substances with biological effects, such as immunomodulators and anticoagulants, which are able to modulate the host’s response to the virus, interfering in its pathogenicity and virulence. Understanding the Aedes vector-chikungunya interaction is fundamentally important since it can enable the search for new methods of combating the virus’ transmission.