Thirty Years of Aedes albopictus (Diptera: Culicidae) in America: An Introduction to Current Perspectives and Future Challenges

Larval competition between the invasive Aedes aegypti (Diptera: Culicidae) and the Caribbean endemic Aedes mediovittatus (Diptera: Culicidae) from Puerto Rico, USA

Competition between mosquito species during the larval phase is a well-established mechanism structuring container mosquito communities, with invasive species often outperforming natives. We assessed the competitive outcome between 2 species that occur on the island of Puerto Rico, the historic invasive Aedes aegypti (L.) and the endemic Aedes mediovittatus (Coquillett) (Diptera: Culicidae). Trials were conducted under intra- and interspecific densities crossed with 2 amounts of 4 different leaf types serving as detrital resources for developing larvae; leaf types were representative of either urban or rural locations. Response variables included survival, male and female mass and development time, and a composite index of population growth (λ'). We also measured tannin levels in detrital environments, a secondary metabolite that can negatively influence mosquito development and survival. The co-occurrence of Ae. aegypti and Ae. mediovittatus generally did not affect survival or population growth of Ae. mediovittatus, however the converse was not true. Specifically, Ae. aegypti suffered lower survival and lower population growth in the presence of Ae. mediovittatus compared to when it was alone. Tannin concentrations did not correspond to competitive outcomes, as the highest tannin levels occurred under the detrital conditions where mosquitoes had highest growth and survival, with no evidence of differences between urban or rural leaf types. This is the first study to quantify the competitive outcomes between these species, both of which are part of the dengue transmission cycle on the island, and our findings suggest that Ae. mediovittatus is capable of outcompeting Ae. aegypti under some resource environments.

Role of Non-Residential Larval Habitats in Aedes Spatiotemporal Egg Production

Aedes mosquitoes play a pivotal role as vectors of several arboviral diseases, presenting significant public health challenges worldwide. Their invasive success in tropical regions has raised substantial medical concerns. In Guatemala, Aedes mosquitoes are widely distributed and are the primary vectors of the dengue virus. Efforts to control and monitor Aedes populations have evolved over time, incorporating strategies such as spatial repellents, larvicides, genetic modifications, and targeted interventions. Previous research has shown the heterogeneous spatial-temporal distribution of these mosquitoes within each season, influenced by temperature variations and favorable environmental conditions for breeding. This study analyzed hot-spot patterns of spatiotemporal egg density in Santa Elena de la Cruz, Petén, Guatemala, from March to September 2022. The aim was to determine whether these patterns were influenced by non-residential larval habitats with plant cover that are not treated by healthcare entities, as well as the proximity between such habitats. Our findings include the collection and registration of over 16,000 Aedes eggs during the study period. Local analyses revealed hot-spot patterns in egg densities associated with non-residential larval habitats and their proximity. These insights highlight critical focal points where targeted interventions could be implemented more effectively, resulting in cost-efficient mosquito vector control.

Surveillance and genetic data support the introduction and establishment of Aedes albopictus in Iowa, USA

Aedes albopictus is a competent vector of several arboviruses that has spread throughout the United States over the last three decades. With the emergence of Zika virus in the Americas in 2015-2016 and an increased need to understand the current distributions of Ae. albopictus in the US, we initiated surveillance efforts to determine the abundance of invasive Aedes species in Iowa. Here, we describe surveillance efforts from 2016 to 2020 in which we detect stable and persistent populations of Aedes albopictus in three Iowa counties. Based on temporal patterns in abundance and genetic analysis of mitochondrial DNA haplotypes between years, our data support that Ae. albopictus are overwintering and have likely become established in the state. The localization of Ae. albopictus predominantly in areas of urbanization, and noticeable absence in rural areas, suggests that these ecological factors may contribute to overwintering success. Together, these data document the establishment of Ae. albopictus in Iowa and their expansion into the Upper Midwest, where freezing winter temperatures were previously believed to limit their spread. With impending climate change, our study provides evidence for the further expansion of Ae. albopictus into temperate regions of the United States resulting in increased risks for vector-borne disease transmission.

Cannibalism and Necrophagy Promote a Resource Loop and Benefit Larval Development in Insects of Temporary Waters

Temporary aquatic habitats are contingent on the allochthonous inputs of plant and animal detritus, whose quality and availability can significantly affect the species developing in these habitats. Although animal detritus (i.e., invertebrate carcasses) is a high-quality food, it is an unpredictable and variable resource. On the contrary, conspecific individuals (dead or alive) are a nutritionally high-quality food source that is always available. In this context, conspecifics consumption, by cannibalism or necrophagy, can be a good strategy to overcome nutrient limitation and allow individual maintenance and development. Here, we tested this hypothesis by using the tiger mosquito Aedes albopictus. By carrying out laboratory and semi-field experiments, we first estimated the relative rate of cannibalism and necrophagy, under different larval densities. Then, we analyzed the effects of cannibalism and necrophagy on larval survival and adult yield. Consistent with our hypothesis, we found that cannibalism and necrophagy occurred under all experimental conditions, and that conspecific consumption had positive effects on individual development, as it significantly increased the rate of adult emergence and larval survival. Interestingly, about 50% of the initial cohort was consumed by conspecifics, suggesting that cannibalism and necrophagy can drive an important resources loop in temporary aquatic habitats.

A Lack of “Environmental Earth Data” at the Microhabitat Scale Impacts Efforts to Control Invasive Arthropods That Vector Pathogens

We currently live in an era of major global change that has led to the introduction and range expansion of numerous invasive species worldwide. In addition to the ecological and economic consequences associated with most invasive species, invasive arthropods that vector pathogens (IAVPs) to humans and animals pose substantial health risks. Species distribution models that are informed using environmental Earth data are frequently employed to predict the distribution of invasive species, and to advise targeted mitigation strategies. However, there are currently substantial mismatches in the temporal and spatial resolution of these data and the environmental contexts which affect IAVPs. Consequently, targeted actions to control invasive species or to prepare the population for possible disease outbreaks may lack efficacy. Here, we identify and discuss how the currently available environmental Earth data are lacking with respect to their applications in species distribution modeling, particularly when predicting the potential distribution of IAVPs at meaningful space-time scales. For example, we examine the issues related to interpolation of weather station data and the lack of microclimatic data relevant to the environment experienced by IAVPs. In addition, we suggest how these data gaps can be filled, including through the possible development of a dedicated open access database, where data from both remotely- and proximally-sensed sources can be stored, shared, and accessed.

What Can Larval Ecology Tell Us About the Success of Aedes albopictus (Diptera: Culicidae) Within the United States?

Aedes albopictus (Skuse) was introduced in the United States approximately 30 years ago, and since has become an important pest and vector of disease. This species uses small water-holding containers as sites for oviposition and larval development. Larvae can consume a wide range of detritus-based energy sources, including microorganisms, and as such the type and quantity of detritus that enters these systems have been studied for the effects on adult populations. This review examines the documented responses of Ae. albopictus to different larval environments within the United States, and some of its unique ecology that may lead to a better understanding of its spread and success. Field surveys generally find larvae in shaded containers with high amounts of organic detritus. Larvae have higher survival and population growth under high amounts of detritus and microorganisms, but they also can outcompete other species when nutrients are limiting. Allocation of time to feeding by larvae is greater and more focused compared with resident species. These latter two points also may explain differences in carbon and nitrogen composition (nutrient stoichiometry), which point to a lower need for nitrogen. Combined, these facts suggest that the Ae. albopictus is a species with a relatively wide niche that had been able to exploit container habitats in the United States better than resident species. After 30 yr of research, only a narrow range of detritus types and environmental conditions have been examined. Data on factors affecting the production of adults and its spread and apparent success are still needed.

Aedes albopictus (Diptera: Culicidae) and Mosquito-Borne Viruses in the United States

The Asian tiger mosquito Aedes albopictus (Skuse), is a highly invasive species that continues to expand its geographic distribution both in the United States and in countries on other continents. Studies have demonstrated its susceptibility to infection with at least 32 viruses, including 13 that are present in the United States. Despite this susceptibility, its role as a significant competent vector in natural transmission cycles of arboviruses, has been limited. However, with the recent introductions of chikungunya and Zika viruses into the Americas, for which Ae. albopictus is a recognized vector, it is possible that the species may contribute to the transmission of these viruses to humans and perhaps other susceptible vertebrates.