Search Results (11)

The West Nile virus (WNV) has recently become more widespread, posing a threat to both human and animal health. In Western Europe, most outbreaks have been caused by WNV lineage 1, while in Eastern Europe, WNV lineage 2 has led to human and bird mortality. The ability to appropriately manage this threat is dependent on integrated surveillance and early detection. This study aimed to quantify the prevalence of WNV infection in mosquitoes and to identify the circulating viral lineage in eastern Croatia. Mosquito traps were set up in rural and urban areas during the 2021–2023 seasons, and the collected specimens were identified morphologically. Mosquito species Culex pipiens and Aedes albopictus were tested for Flaviviruses using conventional PCR in a heminested system. The positive samples were then subjected to a specific real-time PCR designed to detect WNV. A total of 385 mosquito pools were tested, and positive pools were found in samples from Osijek-Baranja and Vukovar-Srijem, both of which contained Cx. pipiens mosquitoes. Sequencing of amplicons revealed WNV lineage 2 partial NS5 gene sequences. Phylogenetic analysis suggests the Hungarian origin of strain, which complements birds’ migratory routes. These findings indicate the first detection of WNV in mosquitoes in Croatia. This suggests that human cases in this region are likely due to infections with lineage 2 transmitted by local Culex mosquitoes. Full article

The common house mosquito (Culex pipiens) is a native vector for West Nile virus (WNV). Invasive species like the tiger mosquito (Aedes albopictus) and Asian bush mosquito (Aedes japonicus) are rapidly spreading through Europe, posing a major threat as vectors for dengue, chikungunya (CHIKV), and Japanese encephalitis virus (JEV). These mosquitoes share a similar ecological niche as larvae, but the carry-over effects of aquatic larval interactions to the terrestrial adult stage remain largely unknown and their medical relevance requires further investigation. This study examines the context dependency of larval interactions among Aedes albopictus, Aedes japonicus, and Culex pipiens. The survival, development time, growth, and energetic storage were measured in different European populations within density-response (intraspecific) experiments and replacement (interspecific) experiments at 20 °C and 26 °C. Overall, Ae. japonicus was the weakest competitor, while competition between Ae. albopictus and Cx. pipiens varied with temperature. Adults emerging from this larval competition were infected as follows: Culex pipiens with WNV, Ae. albopictus with CHIKV, and Ae. japonicus with JEV. While no JEV infection was observed, mosquitoes experiencing interspecific interactions during their larval stages exhibited higher infection rates and viral RNA titers for CHIKV and WNV. This increased susceptibility to viral infection after larval competition suggests a higher risk of arbovirus transmission in co-occurring populations. Full article

Tapachula, Mexico, a tropical city, is an endemic area for dengue, in addition to several outbreaks in the last decade with chikungunya and zika. As part of the migratory corridor from Central to North America and the risks of scattered infectious diseases that this implies, the identification and distribution of potential disease vectors in and around residential areas are essential in terms of entomological surveillance for the prevention of disease outbreaks. The identification of mosquito species of medical importance coexisting in houses and cemeteries in Tapachula and two semiurban sites in southern Chiapas was investigated. Adult mosquitoes were collected from May to December 2018, resting inside and outside houses and in the tombstones and fallen tree leaves in cemeteries. A total of 10,883 mosquitoes belonging to three vector species were collected across 20 sites; 6738 were from neighborhood houses, of which 55.4% were Culex quinquefasciatus, 41.6% Aedes aegypti, and 2.9% Ae. albopictus. Aedes aegypti was the most common mosquito resting inside houses (56.7%), while Ae. albopictus and Cx. quinquefasciatus were mostly found resting outside houses (75.7%). In the cemeteries, Cx. quinquefasciatus (60.8%) and Ae. albopictus (37.3%) were the most abundant, while Ae. aegypti (1.9%) was the least abundant. This is the first report to identify adults of three major disease vector species coexisting in the domestic environment of urban and semiurban sites and Ae. albopictus adult resting inside of urban houses in Mexico. It would be opportune to consider comprehensive strategies that can be applied in this region to control the three species at the same time and avoid outbreaks of the diseases they transmit. Full article

As resistance to the limited number of insecticides available for medical and veterinary pests becomes more widespread, there is an urgent need for new insecticides and synergists on the market. To address this need, we conducted a study to assess the toxicity of three monoterpenoids—carvone, menthone, and fenchone—in comparison to permethrin and methomyl against adults of two common pests: the yellow fever mosquito (Aedes aegypti) and the house fly (Musca domestica). We also examined the potential for these monoterpenoids to enhance the effectiveness of permethrin and methomyl when used together. Finally, we evaluated the ability of each monoterpenoid to inhibit acetylcholinesterase, comparing them to methomyl. While all three monoterpenoids performed relatively poorly as topical insecticides (LD₅₀ > 4000 ng/mg on M. domestica; >6000 ng/mg on Ae. aegypti), they synergized both permethrin and methomyl as well as or better than piperonyl butoxide (PBO). Carvone and menthone yielded synergistic co-toxicity factors (23 and 29, respectively), which were each higher than PBO at 24 h. Currently, the mechanism of action is unknown. During preliminary testing, symptoms of acetylcholinesterase inhibition were identified, prompting further testing. Acetylcholinesterase inhibition did not appear to explain the toxic or synergistic effects of the three monoterpenoids, with IC₅₀ values greater than 1 mM for all, compared to the 2.5 and 1.7 µM for methomyl on Aedes aegypti and Musca domestica, respectively. This study provides valuable monoterpenoid toxicity and synergism data on two pestiferous insects and highlights the potential for these chemistries in future pest control formulations. Full article

The synthesis of nanoparticles by green approaches is gaining unique importance due to its low cost, biocompatibility, high productivity, and purity, and being environmentally friendly. Herein, biomass filtrate of Pseudomonas aeruginosa isolated from mangrove rhizosphere sediment was used for the biosynthesis of zinc oxide nanoparticles (ZnO-NPs). The bacterial isolate was identified based on morphological, physiological, and 16S rRNA. The bio-fabricated ZnO-NPs were characterized using color change, UV-visible spectroscopy, FT-IR, TEM, and XRD analyses. In the current study, spherical and crystalline nature ZnO-NPs were successfully formed at a maximum SPR (surface plasmon resonance) of 380 nm. The bioactivities of fabricated ZnO-NPs including antibacterial, anti-candida, and larvicidal efficacy were investigated. Data analysis showed that these bioactivities were concentration-dependent. The green-synthesized ZnO-NPs exhibited high efficacy against pathogenic Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and unicellular fungi (Candida albicans) with inhibition zones of (12.33 ± 0.9 and 29.3 ± 0.3 mm), (19.3 ± 0.3 and 11.7 ± 0.3 mm), and (22.3 ± 0.3 mm), respectively, at 200 ppm. The MIC value was detected as 50 ppm for E. coli, B. subtilis, and C. albicans, and 200 ppm for S. aureus and P. aeruginosa with zones of inhibition ranging between 11.7 ± 0.3–14.6 ± 0.6 mm. Moreover, the biosynthesized ZnO-NPs showed high mortality for Culex pipiens with percentages of 100 ± 0.0% at 200 ppm after 24 h as compared with zinc acetate (44.3 ± 3.3%) at the same concentration and the same time. Full article

The antifungal and insecticidal effect of the essential oil from Ocimum sanctum L. was evaluated using a model set of harmful organisms hazardous for health and the economy. Toxigenic and plant pathogenic filamentous fungi, including causal agents of human infections, were chosen as exemplary fungal groups—Fusarium verticillioides, Penicillium expansum and Aspergillus flavus. Spodoptera littoralis (African cotton leafworm), Culex quinquefasciatus (Southern house mosquito), the lymphatic filariasis vector and potential Zika virus vector, and the common housefly, Musca domestica were chosen as model insects. Major and minor active substances were detected and quantified using GC/MS analysis. Environmental safety was verified using the non-target useful organism Eisenia fetida. Significant antifungal and insecticidal activity, as well as environmental safety, were confirmed. The essential oil showed the highest efficacy against A. flavus according to MIC50/90, and against S. littoralis larvae according to LD_50/90. The monoterpenoid alcohol linalool, t-methyl cinnamate, and estragole as phenylpropanoids were detected as effective major components (85.4%). The essential oil from Ocimum sanctum L. was evaluated as universal and significantly efficient, providing a high potential for use in environmentally safe botanical pesticides. Full article

The common house mosquito, Culex pipiens s. l. is part of the morphologically hardly or non-distinguishable Culex pipiens complex. Upcoming molecular methods allowed us to identify members of mosquito populations that are characterized by differences in behavior, physiology, host and habitat preferences and thereof resulting in varying pathogen load and vector potential to deal with. In the last years, urban and surrounding periurban areas were of special interest due to the higher transmission risk of pathogens of medical and veterinary importance. Recently, surveys of underground habitats were performed to fully evaluate the spatial distribution of rare members of the Cx. pipiens complex in Europe. Subterranean environments and their contribution to mosquito-borne pathogen transmission are virtually unknown. Herein, we review the underground community structures of this species complex in Europe, add new data to Germany and provide the first reports of the Cx. pipiens complex and usually rarely found mosquito taxa in underground areas of Luxembourg. Furthermore, we report the first finding of Culiseta glaphyroptera in Luxembourg. Our results highlight the need for molecular specimen identifications to correctly and most comprehensively characterize subterranean mosquito community structures. Full article

Vector-borne diseases have appeared or re-emerged in many Southern Europe countries making the transmission of infectious diseases by mosquitoes (vectors) one of the greatest worldwide health threats. Larvicides have been used extensively for the control of Aedes (Stegomyia) albopictus (Skuse, 1895) (Diptera: Culicidae) and Culex pipiens Linnaeus, 1758 (Diptera: Culicidae) mosquitoes in urban and semi-urban environments, causing the increasing resistance of mosquitoes to commercial insecticides. In this study, 27 curcuminoids and monocarbonyl curcumin derivatives were synthesised and evaluated as potential larvicidal agents against Cx. pipiens and Ae. albopictus. Most of the compounds were more effective against larvae of both mosquito species. Four of the tested compounds, curcumin, demethoxycurcumin, curcumin-BF₂ complex and a monocarbonyl tetramethoxy curcumin derivative exhibited high activity against both species. In Cx. pipiens the recorded LC₅₀ values were 6.0, 9.4, 5.0 and 32.5 ppm, respectively, whereas in Ae. albopictus they exhibited LC₅₀ values of 9.2, 36.0, 5.5 and 23.6 ppm, respectively. No conclusive structure activity relationship was evident from the results and the variety of descriptors values generated in silico provided some insight to this end. Full article

The Culex pipiens (Diptera: Culicidae) mosquito is of high medical importance as it is considered the prime vector of West Nile virus. In Europe, this species consists of two forms, named pipiens and molestus, that exhibit substantial differences in their overwintering biology. Diflubenzuron (DFB) and Bacillus thuringiensis var. israelensis (Bti) are two of the most used larvicides in mosquito control, including that of Culex pipiens. The high dependency on these two larvicides poses major concerns for resistance development. The evolution and stability of resistance to insecticides has been associated with fitness costs that may be manifested under stressful conditions, such as the winter period. This study investigated how short-term selection of pipiens and molestus forms to both larvicides affect their overwintering success. Larvae from each form were subjected to the same selective pressure (80% mortality) for three successive generations with DFB and Bti. At the end of this process, the winter survival between the selected populations and the controls (colonies without selection) was determined for each form. Selection to both larvicides significantly reduced the winter survival rates of molestus but not of pipiens form, indicating potential differences in the persistence of the selected individuals from year to year between the two forms. Full article

Despite many studies on West Nile Virus (WNV) in the US, including the reservoir role of bird species and the summer shifts of the Culex mosquito, feeding from birds to mammals, there have been few equivalent studies in the neighboring regions of Canada where WNV is endemic. Here, a priority list of bird species likely involved in WNV transmission in the greater Montréal area is constructed by combining three sources of data: (i) from WNV surveillance in wild birds (2002–2015); (ii) blood meal analysis of Culex pipiens–restuans (CPR), the primary enzootic vectors of WNV in the region, collected from surveillance in 2008 and 2014; (iii) literature review on the sero-prevalence/host competence of resident birds. Each of these data sources yielded 18, 23 and 53 species, and overall, 67 different bird species were identified as potential WNV amplifiers/reservoirs. Of those identified from CPR blood meals, Common starlings, American robins, Song sparrows and House sparrows ranked the highest and blood meal analysis demonstrated a seasonal shift in feed preference from birds to mammals by CPR. Our study indicates that there are broad similarities in the ecology of WNV between our region and the northeastern US, although the relative importance of bird species varies somewhat between regions. Full article

Zika virus (ZIKV) is a mosquito-borne pathogen that caused a large outbreak in the Americas in 2015 and 2016. The virus is currently present in tropical areas around the globe and can cause severe disease in humans, including Guillain-Barré syndrome and congenital microcephaly. The tropical yellow fever mosquito, Aedes aegypti, is the main vector in the urban transmission cycles of ZIKV. The discovery of ZIKV in wild-caught Culex mosquitoes and the ability of Culex quinquefasciatus mosquitoes to transmit ZIKV in the laboratory raised the question of whether the common house mosquito Culex pipiens, which is abundantly present in temperate regions in North America, Asia and Europe, could also be involved in ZIKV transmission. In this study, we investigated the vector competence of Cx. pipiens (biotypes molestus and pipiens) from the Netherlands for ZIKV, using Usutu virus as a control. After an infectious blood meal containing ZIKV, none of the tested mosquitoes accumulated ZIKV in the saliva, although 2% of the Cx. pipiens pipiens mosquitoes showed ZIKV–positive bodies. To test the barrier function of the mosquito midgut on virus transmission, ZIKV was forced into Cx. pipiens mosquitoes by intrathoracic injection, resulting in 74% (molestus) and 78% (pipiens) ZIKV–positive bodies. Strikingly, 14% (molestus) and 7% (pipiens) of the tested mosquitoes accumulated ZIKV in the saliva after injection. This is the first demonstration of ZIKV accumulation in the saliva of Cx. pipiens upon forced infection. Nevertheless, a strong midgut barrier restricted virus dissemination in the mosquito after oral exposure and we, therefore, consider Cx. pipiens as a highly inefficient vector for ZIKV. Full article