[First detections of Aedes albopictus (tiger mosquito) in the region of Extremadura, west of Spain]

Aedes albopictus diversity and relationships in south-western Europe and Brazil by rDNA/mtDNA and phenotypic analyses: ITS-2, a useful marker for spread studies

BACKGROUND

Aedes albopictus is a very invasive mosquito, which has recently colonized tropical and temperate regions worldwide. Of concern is its role in the spread of emerging or re-emerging mosquito-borne diseases. Ae. albopictus from south-western Europe and Brazil were studied to infer genetic and phenetic diversity at intra-individual, intra-population and inter-population levels, and to analyse its spread.

METHODS

Genotyping was made by rDNA 5.8S-ITS-2 and mtDNA cox1 sequencing to assess haplotype and nucleotide diversity, genetic distances and phylogenetic networks. Male and female phenotyping included combined landmark-and outlined-based geometric morphometrics of wing size and shape.

RESULTS

Specimens from seven populations from Spain, France and Brazil provided 12 cox1 and 162 5.8S-ITS-2 haplotypes, with great genetic variability difference between both markers (0.9% vs 31.2%). Five cox1 haplotypes were shared with other countries, mainly Italy, USA and China, but none was shared between Europe and Brazil. The 5.8S-ITS-2 showed 2-7 intra-individual (mean 4.7) and 16-34 intra-/inter-population haplotypes (24.7), including haplotypes shared between Spain, France and Brazil. A 4.3% of ITS-2 haplotypes were shared, mainly with Italy, USA and Thailand, evidencing worldwide spread and introductions from areas where recent outbreaks of Ae. albopictus-transmitted pathogens occurred. Wing size showed sex differences. Wing shape distinguished between Brazilian and European specimens. Both genetic and morphometric markers showed differences between insular Spain and continental Spain, France and Brazil.

CONCLUSIONS

ITS-2 proves to be a useful marker to assess Ae. albopictus spread, providing pronouncedly more information than cox1, including intra-individual, intra-population and inter-population levels, furnishing a complete overview of the evolutionary exchanges followed by this mosquito. Wing morphometry proves to be a useful phenotyping marker, allowing to distinguish different populations at the level of both male and female specimens. Results indicate the need for periodic surveillance monitorings to verify that no Ae. albopictus with high virus transmission capacity is introduced into Europe.

Evidence of Wing Shape Sexual Dimorphism in Aedes (Stegomyia) albopictus in Mallorca, Spain

The Asian tiger mosquito Aedes albopictus (Skuse, 1894) is a highly invasive species widely distributed on the Spanish Mediterranean coast and the Balearic archipelago. Most studies involving this species in Spain have been focused on surveillance and control methods. However, micro-evolutionary studies for Ae. albopictus in Spain have been traditionally neglected. Morphological diversity could be the result of long-term evolutionary diversification in responses to selective pressures such as temperature, precipitation, food availability, predation, or competition that may influence flight activity, host-seeking, and blood-feeding behavior. Wing geometric morphometric have been used not only to study micro- and macro-evolution in mosquitoes but also in studies of population structuring and sexual dimorphism. Therefore, the main goal of this study was to investigate the wing shape patterns of Ae. albopictus populations to unveil sexual dimorphism that could provide information about their ecology and behavior. Mosquito eggs were collected using oviposition traps at the main campus of the University of the Balearic Islands (Palma de Mallorca, Spain) and reared under laboratory conditions. In order to study wing shape variation patterns in Ae. albopictus males and females, the left wing of each adult mosquito was removed and analyzed based on 18 landmarks. Our results indicated strong levels of sexual dimorphism between Ae. albopictus males and females. Furthermore, according to the cross-validated reclassification test, males were correctly distinguished from females with an accuracy of 84% and females from males 75%. We observed a significant sexual dimorphism in the wing shape patterns of Ae. albopictus when considering different seasonal patterns (spring vs. autumn). Our results suggested that selective pressures may affect males differently to females. Host-seeking, blood-feeding, and oviposition behavior of females may act as a major driver for wing shape sexual dimorphism. These results should be considered for the development of more effective and targeted mosquito control strategies.

Mosquito fauna in Extremadura (western Spain): Updated catalog with new records, distribution maps, and medical relevance

An important element of vector control and surveillance of mosquito-borne diseases is updated information on vector species distribution. The aim of this study was to collect available information about mosquito species reported in Extremadura between 1920 and 2020 and create a catalog that would combine both published data and our recent field identifications. An exhaustive list is hereby presented, including species status and detailed distribution maps at a municipal level as well as their importance for public health. A total of 33 species, classified into five genera: Anopheles (five species), Aedes (14), Culex (nine), Culiseta (four), and Orthopodomyia (one) has been recorded, including 31 autochthonous, one invasive, Aedes (Stegomyia) albopictus, and one disappeared since 1953, Aedes (Stegomyia) aegypti. For the first time in Extremadura, we report the presence of important vectors such as Aedes (Aedimorphus) vexans vexans and Culex (Culex) perexiguus, and the new record of six species in the province of Badajoz, namely: Aedes (Dahliana) echinus, Aedes (Fredwardsius) vittatus, Aedes (Ochlerotatus) berlandi, Aedes (Ochlerotatus) pulcritarsis, Culex (Culex) mimeticus, and Culiseta (Culiseta) subochrea. Nineteen of these species are potential vectors of medical and veterinary relevance.

Importation of dengue, Zika and chikungunya infections in Europe: the current situation in Greece

Although several arboviruses-such as dengue (DENV), Zika (ZIKV) and chikungunya (CHIKV) viruses-are not endemic in Europe, they have the potential to emerge following importation of the virus, taking advantage of the favourable climate and ecosystem. DENV, ZIKV and CHIKV are transmitted by Aedes species mosquitoes and are amongst the most common travel-associated arboviruses. Furthermore, they are linked to sporadic, local outbreaks, especially in the southern parts of Europe. In this review we present in brief the DENV, ZIKV and CHIKV cases imported to Greece during the last 6 years (2013-2018), and we describe the recent laboratory data obtained from the Hellenic Pasteur Institute and the National Reference Centre for Arboviruses. We report 21 imported cases of DENV, ZIKV and CHIKV infections in travellers arriving in Greece. The probable origins were south-eastern Asian (71%) and north-central American (29%) countries. Furthermore, we stress the importance of early and accurate diagnosis in spite of a plethora of diagnostic challenges that clinicians and virologists have to face. Altogether, with the authorities' awareness and the preventive measures to be applied, local transmission events can be successfully avoided, especially in summer when the temperature is favourable for mosquito-borne infections.

Primeras actuaciones de vigilancia y control del mosquito tigre, Aedes (Stegomyia) albopictus (Skuse, 1894) (Diptera: Culicidae), tras su detección en el municipio de Velilla de San Antonio de la Comunidad de Madrid en 2018

El mosquito tigre es una especie invasora originaria del sudeste asiático que puede actuar como vector potencial de diversas arbovirosis como el dengue, el chikunguña y el zika. Desde el año 2004 en que se detectó por primera vez en España, se ha extendido por el litoral mediterráneo y otras áreas del interior peninsular, siguiendo una progresión que también se da en otras regiones de Europa y del mundo. En el mes de septiembre de 2018 se detectó su presencia en el municipio de Velilla de San Antonio (Comunidad de Madrid). Se estableció un grupo de trabajo entre salud pública, la Facultad de Ciencias Biológicas de la Universidad Complutense de Madrid y el ayuntamiento para definir y coordinar las actuaciones. Se establecieron dos áreas de trabajo, una de vigilancia, de 400-500 metros desde el punto en el que fue detectado y otra de actuación prioritaria, de 150-200 metros, con el objetivo de evaluar el área afectada, reducir su población e intentar su eliminación si ello fuera posible.

Primeras actuaciones de vigilancia y control del mosquito tigre, Aedes (Stegomyia) albopictus (Skuse, 1894) (Diptera: Culicidae), tras su detección en el municipio de Velilla de San Antonio de la Comunidad de Madrid en 2018

El mosquito tigre es una especie invasora originaria del sudeste asiático que puede actuar como vector potencial de diversas arbovirosis como el dengue, el chikunguña y el zika. Desde el año 2004 en que se detectó por primera vez en España, se ha extendido por el litoral mediterráneo y otras áreas del interior peninsular, siguiendo una progresión que también se da en otras regiones de Europa y del mundo. En el mes de septiembre de 2018 se detectó su presencia en el municipio de Velilla de San Antonio (Comunidad de Madrid). Se estableció un grupo de trabajo entre salud pública, la Facultad de Ciencias Biológicas de la Universidad Complutense de Madrid y el ayuntamiento para definir y coordinar las actuaciones. Se establecieron dos áreas de trabajo, una de vigilancia, de 400-500 metros desde el punto en el que fue detectado y otra de actuación prioritaria, de 150-200 metros, con el objetivo de evaluar el área afectada, reducir su población e intentar su eliminación si ello fuera posible.

Imported dengue in Spain: a nationwide analysis with predictive time series analyses

BACKGROUND

Of febrile illnesses in Europe, dengue is second only to malaria as a cause of travellers being hospitalized. Local transmission has been reported in several European countries, including Spain. This study assesses the evolution of dengue-related admissions in Spain in terms of time, geographical distribution and individuals' common characteristics; it also creates a predictive model to evaluate the risk of local transmission.

METHODS

This is a retrospective study using the Hospital Discharge Records Database from 1997 to 2016. We calculated hospitalization rates and described clinical characteristics. Spatial distribution and temporal behaviour were also assessed, and a predictive time series model was created to estimate expected cases in the near future. Figures for resident foreign population, Spanish residents' trips to endemic regions and the expansion of Aedes albopictus were also evaluated.

RESULTS

A total of 588 dengue-related admissions were recorded: 49.6% were women, and the mean age was 34.3 years. One person died (0.2%), 82% presented with mild-to-moderate dengue and 7-8% with severe dengue. We observed a trend of steady and consistent increase in incidence (P < 0.05), in parallel with the increase in trips to dengue-endemic regions. Most admissions occurred during the summer, showing significant seasonality with 3-year peaks. We also found important regional differences. According to the predictive time series analysis, a continuing increase in imported dengue incidence can be expected in the near future, which, in the worst case scenario (upper 95% confidence interval), would mean an increase of 65% by 2025.

CONCLUSION

We present a nationwide study based on hospital, immigration, travel and entomological data. The constant increase in dengue-related hospitalizations, in combination with wider vector distribution, could imply a higher risk of autochthonous dengue transmission in the years to come. Strengthening the human and vector surveillance systems is a necessity, as are improvements in control measures, in the education of the general public and in fostering their collaboration in order to reduce the impact of imported dengue and to prevent the occurrence of autochthonous cases.