Composition, seasonal abundance, and public health importance of mosquito species in the regional unit of Thessaloniki, Northern Greece

Ecological niche modeling analysis (Cx. pipiens), potential risk and projection of Dirofilaria spp. infection in Greece

Vector-borne diseases continue to increase worldwide. Dirofilariosis is one of the most common vector-borne zoonotic diseases, mainly caused by Dirofilaria spp. (D. immitis and D. repens) and spread by culicid mosquitoes of different species. Greece is one of the countries in southern Europe where it is traditionally endemic, and its distribution is not homogeneous. The aim of this study was to develop an environmental model for Greece that reflects the suitability of the ecological niche for Dirofilaria spp. infection risk and its projection until 2080. For this purpose, we used the potential distribution of suitable habitats for Culex pipiens calculated using an ecological niche model (ENM) and the potential number of generations of Dirofilaria spp. The ecological niche model of Cx. pipiens in Greece showed good predictive power (AUC=0.897) with the parasite at a resolution of 1 km2. The variables that contributed most to the model were mean annual temperature, rivers and human footprint. The highest risk of infection was found in coastal areas and in riverside areas of the main river basins, as well as in irrigated areas of the mainland and peninsular regions and in the whole territory of island areas, and the lowest risk was found in areas of higher altitude. A positive relationship was found between the risk of dirofilariosis and the location of infected dogs, with 86.65% located in very high and high risk areas. In 2080, the percentage of territory gained by Cx. pipiens will increase by 261.52%. This model provides a high predictive value, predicted presence, and risk of Dirofilaria spp. infection and can serve as a tool for the management and control of this disease.

Applicability evaluation of mtDNA based molecular identification in mosquito species/subspecies/biotypes collected from Thessaloniki, Greece

The genus Culex, containing many described species, plays a role as a vector for diseases of medical and veterinary importance worldwide. Among these species, Culex pipiens is one of the most widespread mosquitoes and is classified into two biological forms (biotypes), named as Culex pipiens pipiens and Culex pipiens molestus. Due to similar morphological structure between these biotypes, morphological identification is inadequate. Thus, molecular methods have been developed and are considered more reliable, some of which are based on analyses of mitochondrial DNA. The aim of the present study was to evaluate the applicability and reliability of mtDNA based molecular identification methodologies. Initially, mosquito specimens (n = 100) collected from Thessaloniki, Greece were morphologically analyzed. Then, mitochondrial cox1 sequencing and PCR-RFLP methods were used to confirm the morphological identification results as well as to discriminate species and subspecies/biotype of Culex pipiens complex. According to morphological identification results, Culex pipiens complex (n = 92), Culex modestus (n = 6) and Culex theileri (n = 2) were detected. Using mtDNA sequencing, all Culex modestus and Culex theileri samples were confirmed whereas 86 of Culex pipiens complex were detected as Culex pipiens but surprisingly the remaining six of them were detected as Culex quinquefasciatus. Among Culex pipiens specimens, PCR-RFLP detected that frequency of Culex pipiens pipiens (85%; 85/100) was very high compared to Culex pipiens molestus (1%, 1/100). In conclusion, this study shows the necessity of use of molecular methods beside morphological methods for especially specimens detected as Culex pipiens. Also, it was shown that mtDNA PCR-RFLP methodology represents a well-established alternative for Culex biotypes identification.

Updated occurrence and bionomics of potential malaria vectors in Europe: a systematic review (2000-2021)

Despite the eradication of malaria across most European countries in the 1960s and 1970s, the anopheline vectors are still present. Most of the malaria cases that have been reported in Europe up to the present time have been infections acquired in endemic areas by travelers. However, the possibility of acquiring malaria by locally infected mosquitoes has been poorly investigated in Europe, despite autochthonous malaria cases having been occasionally reported in several European countries. Here we present an update on the occurrence of potential malaria vector species in Europe. Adopting a systematic review approach, we selected 288 papers published between 2000 and 2021 for inclusion in the review based on retrieval of accurate information on the following Anopheles species: An. atroparvus, An. hyrcanus sensu lato (s.l.), An. labranchiae, An. maculipennis sensu stricto (s.s.), An. messeae/daciae, An. sacharovi, An. superpictus and An. plumbeus. The distribution of these potential vector species across Europe is critically reviewed in relation to areas of major presence and principal bionomic features, including vector competence to Plasmodium. Additional information, such as geographical details, sampling approaches and species identification methods, are also reported. We compare the information on each species extracted from the most recent studies to comparable information reported from studies published in the early 2000s, with particular reference to the role of each species in malaria transmission before eradication. The picture that emerges from this review is that potential vector species are still widespread in Europe, with the largest diversity in the Mediterranean area, Italy in particular. Despite information on their vectorial capacity being fragmentary, the information retrieved suggests a re-definition of the relative importance of potential vector species, indicating An. hyrcanus s.l., An. labranchiae, An. plumbeus and An. sacharovi as potential vectors of higher importance, while An. messeae/daciae and An. maculipennis s.s. can be considered to be moderately important species. In contrast, An. atroparvus and An. superpictus should be considered as vectors of lower importance, particularly in relation to their low anthropophily. The presence of gaps in current knowledge of vectorial systems in Europe becomes evident in this review, not only in terms of vector competence but also in the definition of sampling approaches, highlighting the need for further research to adopt the appropriate surveillance system for each species.