Search Results (44)

Background: Arthropod-borne diseases primarily affect tropical and subtropical regions, exhibiting seasonal patterns that peak during hot and rainy months when conditions favor mosquito vector proliferation. Factors such as high temperatures, elevated humidity, rainfall, urbanization, and the abundance of natural and artificial breeding sites influence Aedes vector dynamics. In this context, arboviruses pose significant public health challenges, likely worsened by global warming. In Brazil, Aedes (Stegomyia) aegypti (Linnaeus, 1762) is the primary vector for yellow fever, dengue, chikungunya, and Zika. Aedes (Stegomyia) albopictus (Skuse, 1894) is an important global arbovirus vector and is considered a potential vector in Brazil. Entomological surveillance of these species often uses oviposition traps targeting immature stages. Evaluating studies that use ovitraps to collect Ae. aegypti and Ae. albopictus egg is essential for improving mosquito surveillance strategies. This study systematically reviewed peer-reviewed articles on ovitrap-based surveillance of Aedes mosquitoes in Brazil, published in Portuguese and English from 2012 to 2022. The findings suggest that ovitraps are an effective method for detecting the presence or absence of Ae. aegypti and Ae. albopictus, serving as a reliable proxy for estimating mosquito abundance in Brazilian contexts. Full article

This study examines the desiccation tolerance of Aedes aegypti and Aedes albopictus eggs, two major arbovirus vectors, in a subtropical region of Argentina to understand their survival under varying relative humidity (RH) conditions (35%, 68%, and 82%). Laboratory experiments revealed that Ae. aegypti eggs exhibited significantly higher survival rates across all RH levels and exposure times compared to Ae. albopictus. After 1 month, Ae. aegypti eggs maintained 88% survival at 35% RH, while Ae. albopictus survival dropped to 38%. This disparity was more pronounced at low RH, where Ae. albopictus eggs experienced a rapid decline in survival over time. The results highlight the importance of RH as a key factor influencing the persistence of both species in the environment. The coexistence of Ae. aegypti and Ae. albopictus in Puerto Iguazú suggests that microhabitats with distinct humidity conditions may favor one species over the other. These findings provide crucial insights for predicting mosquito population dynamics under changing climate conditions and developing more effective vector control strategies to reduce arbovirus transmission in subtropical regions. Full article

Aedes albopictus is one of the most important vectors of Dengue, which poses a serious threat to public health. The bacterial microbiota has an effect on the parameters of mosquitos, such as larval development and fecundity, and it has emerged as a promising field to be explored for novel environmentally friendly control strategies. Rahnella sp. are present in many insects, including Ae. Albopictus, and play a role in bacterial–insect interactions; however, the role of the bacteria in mosquito biology has not yet been characterized. In this study, we characterized the Rahnella isolate RAeA1 obtained from Ae. albopcitus, and its colonization stability in Ae. albopictus was investigated by generating GFP-tagged bacteria. The influences of the bacteria on larval development and mosquito reproductive capacity were evaluated by inoculating RAeA1 in axenic larvae and antibiotic-treated adult mosquitoes, respectively. The results indicated that RAeA1, which is widespread in the field population of Ae. albopictus, can be transmitted directly from the parental strain to the progeny and can rescue axenic larvae developing into adults with a prolonged development time to pupation. RAeA1 inoculation can impair egg production and ovary maturation, as well as reducing the synthesis of ecdysteroids and vitellogenin in Ae. albopictus females. Overall, our results provide a thorough study of bacterium function characterization that will facilitate the development of potential strategies in relation to the design of microbiomes for vector control. Full article

The mosquito Aedes albopictus is a vector of several harmful viruses, necessitating the development of safer and more sustainable repellents than DEET. This study evaluated the potential of plant-based EOs extracted via steam distillation from Aloysia citrodora and Bursera graveolens plants harvested in Ecuador. A. citrodora EO exhibited a high sensory pleasantness with a citral-like aroma, while B. graveolens EO had lower sensory appeal due to off-flavors. At 200 µL L⁻¹, B. graveolens EO demonstrated strong ovideterrent activity, reducing egg laying by 64%, whereas A. citrodora EO displayed the highest larvicidal activity with an LC₅₀ value of 88.54 µL L⁻¹. Both EOs, applied at 0.20 µL cm⁻² on human skin, provided comparable repellency for over 45 min. The RD₅₀ values were 0.104 µL cm⁻² for A. citrodora EO and 0.136 µL cm⁻² for B. graveolens EO. When compared to DEET at 0.04 µL cm⁻², no significant differences in repellency were observed within the first 15 min post-application. These findings suggest that both EOs are effective alternatives to synthetic repellents, and A. citrodora EO emerges as a promising candidate due to its superior sensory attributes and larvicidal activity. Full article

Aedes albopictus and Aedes japonicus are invasive mosquito species that are causing great public concern. Aedes albopictus have successfully spread in Croatia, established in both the coastal and continental parts of the country, while Aedes japonicus is invading temperate climate areas. The invasive Aedes species are particularly attracted to the black plastic water containers and flower vases in cemeteries where they oviposit their eggs. Therefore, monitoring of this species was carried out in 12 cemeteries in Zagreb, using ovitraps with masonite strips as a substrate for oviposition. The monitoring was carried out from 2017 to 2020. The traps were inspected and the substrate was replaced every two weeks. This study showed that these two invasive species were present and very abundant in the cemeteries. In the case of Ae. albopictus, a higher population density and a greater number of occupied cemeteries were detected. This species was identified in all 12 cemeteries. Aedes albopictus was identified as the dominant species at all study sites. The spread of Ae. japonicus increased during 2018 in comparison to the previous year. Although this species was present in approximately 9% of the ovitraps, the observed population remained consistent throughout the course of the study. The findings indicate that cemeteries can be considered as significant public health hotspots, as the invasive Aedes mosquitoes tend to develop and reproduce in such environments. Consequently, the mosquito population of these two invasive species may only be reduced by applying integrated mosquito management measures, focused on the education of citizens. Full article

Although integrated management and control programs implement intense control measures for adult, pupal, larval, and breeding sites during outbreaks, there is a lack of studies to understand the role of the vector egg stage in disease dynamics. This study aimed to assess the dry season quiescent Aedes aegypti and Aedes albopictus egg populations in houses and backyards in Tapachula, southern Mexico. Two hundred and fifty ovitraps were placed in 125 homes in the Las Americas neighborhood. A total of 7290 eggs were collected from 211 (84.4%) ovitraps. Only 5667 (77.7%) hatched under insectary water immersion and food supply conditions, with 4031 (71.1%) identified as Ae. aegypti, and 1636 (28.8%) as Ae. albopictus, respectively. The remaining 1623 (22.3%) did not hatch due to Delayed Hatching and/or quiescence tropical stage. Eighty-three larval containers were sampled with desiccated eggs during the dry season; most of them were described as trash waste because larvicides are only used for larger containers of 5–10 L. Evolutionary characteristics for the two species including partial egg hatching, ambient-regulated quiescence, the ability of the embryo to survive for a more extended period intra-seasonally, the egg sticking to inner container walls, demands urgent operational research to achieve successful egg-proof larval container methods. Full article

The key to success in the application of the sterile insect technique (SIT) relies on the ability of released, sterile males to outcompete their fertile wild male counterparts to mate with wild females. However, many insect species exhibit multiple-mating behavior, which can be a way for females to select paternity for their progeny. This study aims to recognize the consequences of potential double-matings during an SIT program and to detect any evidence of sperm selection favoring sperm from fertile mates. This report provides a descriptive analysis of the storage and use of sperm by female Aedes albopictus. Stable isotopes were used to mark the sperm of fertile and sterile males. Mated females were allowed to oviposit before dissecting the spermathecae to link the presence of each type of sperm to the sterility of the eggs laid. It was found that sperm in females inseminated by both males was distributed in the three spermathecae with no obvious pattern, mostly mixed but also separately, and no evidence of any mechanism for sperm selection, sperm precedence, or sperm competition in Ae. albopictus females could be found. The fact that only a few double-mated females were double-inseminated and could also produce semi-sterile eggs, together with the finding that the sperm of sterile males appeared to be no less viable than that of fertile males, is an encouraging outcome for SIT approaches. Full article

Dengue is an important mosquito-borne disease in Sri Lanka. The Sterile Insect Technique (SIT) is an environment-friendly and novel method that can suppress dengue vector mosquitoes in Sri Lanka. This study aimed to evaluate the field performance of sterile males and the density of wild male Aedes albopictus (Skuse) using a Mark–Release–Recapture (MRR) assay. Laboratory-colonized male pupae were exposed to 50 Gy gamma using a Co⁶⁰ source. Sterile males (approx. 10,000) marked with fluorescent dust were released weekly for 4 consecutive weeks (January–February 2021) in a geographically isolated 30 ha site in Gampaha. Results show sterile males could disperse up to 543.8 m with a mean distance of 255.1 ± 44.6 m and survive up to 6 days with a mean life expectancy of 3.55 ± 2.32 days. A high field mating competitiveness of sterile males based on a Fried value of 0.47 ± 0.007 and significant induced sterility in the wild eggs in the second generation were found. The mean wild male mosquito population density was 163 males/ha. The data generated will be useful for designing future trials in Sri Lanka and other countries with similar situations. Full article

The emergence of insecticide resistance in arbovirus vectors is putting the focus on the development of new strategies for control. In this regard, the exploitation of Wolbachia endosymbionts is receiving increasing attention due to its demonstrated effectiveness in reducing the vectorial capacity of Aedes mosquitoes. Here, we describe the establishment of a naïve Wolbachia infection in a wild Aedes albopictus population of eastern Spain through a hybridization approach to obtain males capable of sterilizing wild females. The obtained lines were compared with the Wolbachia donor, Ae. albopictus ARwP, previously artificially infected with Wolbachia wPip, regarding immature and adult survival, female fecundity, egg fertility, and level of induced sterility. Our results did not show significant differences between lines in any of the biological parameters analyzed, indicating the full suitability of the hybrids to be used as a control tool against Ae. albopictus. In particular, hybrid males induced 99.9% sterility in the eggs of wild females without the need for any preliminary treatment. Being harmless to non-target organisms and the environment, the use of this bacterium for the control of Ae. albopictus deserves further exploration. This is especially relevant in areas such as eastern Spain, where this mosquito species has recently spread and may represent a serious threat due to its competence as a vector for dengue, chikungunya, and Zika viruses. Full article

Background: Aedes albopictus, the Asian tiger mosquito, has become a prevalent pest in Italy, causing severe nuisance and posing a threat of transmission of arboviruses introduced by infected travelers. In this study, we investigated the influence of weather parameters on the seasonal population density of Aedes albopictus. Methods: A Bayesian approach was employed to identify the best meteorological predictors of species trend, using the eggs collected monthly from 2010 to 2022 by the Emilia-Romagna regional monitoring network. Results: The findings show that the winter–spring period (January to May) plays a crucial role in the size of the first generation and seasonal development of the species. Conclusions: A temperate winter and a dry and cold March, followed by a rainy and hot spring and a rainy July, seem to favor the seasonal development of Ae. albopictus. Full article

Updated information on the distribution and abundance of Aedes aegypti and Aedes albopictus is crucial to prepare African countries, such as Benin, for possible arboviral disease outbreaks. This study aims to evaluate the geographical distribution, abundance and biting behaviour of these two vectors in Benin. Three sampling techniques were used in this study. The collection of Aedes spp. adults were made through human landing catch (HLC), immatures were captured with the use of ovitraps, and a dipping technique was used for the collection of Aedes spp. in 23 communes located along the North–South and East–West transect of Benin. Adult Aedes mosquitoes were collected indoors and outdoors using HLC. Mosquito eggs, larvae and pupae were collected from containers and ovitraps. The adult mosquitoes were morphologically identified, then confirmed using a polymerase chain reaction (PCR). Overall, 12,424 adult specimens of Aedes spp. were collected, out of which 76.53% (n = 9508) and 19.32% (n = 2400) were morphologically identified as Ae. aegypti and Ae. albopictus, respectively. Geographically, Ae. aegypti was found across the North–South transect unlike Ae. albopictus, which was only encountered in the southern part of the country, with a great preponderance in Avrankou. Furthermore, an exophagic behaviour was observed in both vectors. This updated distribution of Aedes mosquito species in Benin will help to accurately identify areas that are at risk of arboviral diseases and better plan for future vector control interventions. Full article

In recent years, Aedes albopictus (Skuse, 1984) has expanded its distribution globally due to its high ecological plasticity. This expansion has increased the population’s susceptibility to contracting diseases such as dengue, Zika, and chikungunya, among others, which are transmitted by this mosquito species. In the absence of effective control methods, the application of the sterile insect technique (SIT) is proposed as part of an integrated vector management (IVM) program. From 2007 to 2020, this strategy has been tested in a non-isolated mosquito population urban area of 45 ha, representative of the municipalities of the Valencian region (Spain). The population levels of adult females and eggs collected in the traps have been reduced by 70–80% compared to the control area, demonstrating its efficacy in reducing mosquito populations. This work analyzes the impact of the migration of the wild mosquito population from the peri-urban area to the urban core. Full article

La Crosse virus (LACV) is circulating in the midwestern and southeastern states of the United States and can cause human encephalitis. The main vector of the virus is the eastern tree-hole mosquito, Aedes triseriatus. Ae. albopictus has been also described as a natural LACV vector, while Ae. aegypti has been infected with the virus under laboratory conditions. Here, we compare the vertical transmission potential of LACV in Ae. albopictus and Ae. aegypti, with emphasis given to the ovarian infection patterns that the virus generates in both species. Both mosquito species received artificial bloodmeals containing LACV. At defined time points post-infection/bloodmeal, midguts, head tissue, and ovaries were analyzed for the presence of virus. Viral infection patterns in the ovaries were visualized via immunofluorescence confocal microscopy and immunohistopathology assays using an LACV-specific monoclonal antibody. In Ae. aegypti, LACV was confronted with midgut infection and escape barriers, which were much less pronounced in Ae. albopictus, resulting in a significantly higher prevalence of infection in the latter. Following the ingestion of a single virus-containing bloodmeal, no progeny larvae were found to be virus-infected. Regardless, females of both species showed the presence of LACV antigen in their ovariole sheaths. Furthermore, in a single Ae. albopictus female, viral antigen was associated with the nurse cells inside the primary follicles. Following the ingestion of a second non-infectious bloodmeal at 7- or 10-days post-ingestion of an LACV-containing bloodmeal, more progeny larvae of Ae. albopictus than of Ae. aegypti were virus-infected. LACV antigen was detected in the egg chambers and ovariole sheaths of both mosquito species. Traces of viral antigen were also detected in a few oocytes from Ae. albopictus. The low level of vertical transmission and the majority of the ovarian infection patterns suggested the transovum rather than transovarial transmission (TOT) of the virus in both vector species. However, based on the detection of LACV antigen in follicular tissue and oocytes, there was the potential for TOT among several Ae. albopictus females. Thus, TOT is not a general feature of LACV infection in mosquitoes. Instead, the TOT of LACV seems to be dependent on its particular interaction with the reproductive tissues of a female. Full article

Background: The mosquito microbiota impacts different parameters in host biology, such as development, metabolism, immune response and vector competence to pathogens. As the environment is an important source of acquisition of host associate microbes, we described the microbiota and the vector competence to Zika virus (ZIKV) of Aedes albopictus from three areas with distinct landscapes. Methods: Adult females were collected during two different seasons, while eggs were used to rear F1 colonies. Midgut bacterial communities were described in field and F1 mosquitoes as well as in insects from a laboratory colony (>30 generations, LAB) using 16S rRNA gene sequencing. F1 mosquitoes were infected with ZIKV to determine virus infection rates (IRs) and dissemination rates (DRs). Collection season significantly affected the bacterial microbiota diversity and composition, e.g., diversity levels decreased from the wet to the dry season. Field-collected and LAB mosquitoes’ microbiota had similar diversity levels, which were higher compared to F1 mosquitoes. However, the gut microbiota composition of field mosquitoes was distinct from that of laboratory-reared mosquitoes (LAB and F1), regardless of the collection season and location. A possible negative correlation was detected between Acetobacteraceae and Wolbachia, with the former dominating the gut microbiota of F1 Ae. albopictus, while the latter was absent/undetectable. Furthermore, we detected significant differences in infection and dissemination rates (but not in the viral load) between the mosquito populations, but it does not seem to be related to gut microbiota composition, as it was similar between F1 mosquitoes regardless of their population. Conclusions: Our results indicate that the environment and the collection season play a significant role in shaping mosquitoes’ bacterial microbiota. Full article

Culicid species, which include potential vectors of yellow fever, are diverse and abundant, with species commonly co-occurring in certain sites. Studying these species can provide important insights into their vector potential and, consequently, epizootic cycles of arboviruses carried about by these vectors. Here, we evaluated the vertical distribution and temporal segregation of mosquito oviposition with emphasis on arbovirus vectors in a fragment of the Atlantic Forest in Casimiro de Abreu, Rio de Janeiro, Brazil. Two sampling points were selected: Fazenda Três Montes and the Reserva Natural de Propriedade Privada Morro Grande. Collections were carried out at two sites using 10 ovitraps installed on the vegetation cover at different heights (0, 2, 4, 6, and 8 m above ground level) and monitored monthly from July 2018 to December 2020. The hypotheses of temporal and vertical stratification were tested through a PERMANOVA, and the relationship of each species with the vertical distribution was evaluated individually through a correlation analysis. We collected a total of 3075 eggs, including four species of medical importance: Haemagogus leucocelaenus (n = 1513), Haemagogus janthinomys (n = 16), Aedes albopictus (n = 1097), and Aedes terrens (n = 449). We found that Hg. leucocelaenus had a positive relationship with height, exhibiting behavior that appears to benefit from higher heights. The abundance of Ae. terrens seemed to follow Hg. leucocelaenus, although we did not find a relationship with height for the former species. On the other hand, Ae. albopictus exhibited a negative relationship with height, becoming absent or outnumbered at higher strata. Our study site has already presented evidence of recent transmission of the wild yellow fever virus, supporting the need to carefully monitor the emergence of febrile diseases among residents in the surrounding areas and the local population. Full article