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Container-breeding Aedes spp. (Diptera: Culicidae) mosquitoes can be surveilled at low cost using ovitraps. Hence, this method is a preferred monitoring approach of dengue vectors in low-resource settings. The ovitraps consist of a cup filled with water and an oviposition substrate for female mosquitoes. The attractiveness of the substrates for female mosquitoes can greatly differ due to differences in texture, color, and smell of the materials used. We compare four oviposition substrates, which are all low priced, easy to transport, and easy to purchase, to maximize the success of Aedes egg sampling. Sampled egg material is often reared to adulthood for further taxonomic identification and transported to (international) laboratories for specialized vector research. Here we introduce a transport technique for sampled eggs. In addition, we explored the impact of international transport by means of a bilateral hatching experiment in Nepal, the country of origin, and in Germany, in a laboratory specialized in ecophysiological research. The best low-cost oviposition substrate for the dengue vectors Aedes albopictus (Skuse) and Aedes aegypti (L.) was found to be a white cotton sheet. The introduced transport technique of sampled eggs is easy to build from laboratory and household materials and ensures good transport conditions (i.e., temperature and relative humidity). Even under good temperature (17.4–31.0 °C) and humidity conditions (58.9–94.2%), hatching success of eggs was found to be reduced after international transport to Germany when compared to the hatching success of eggs in Nepal. We postulate that air pressure during international transport may have reduced the hatching success and strongly recommend pressure-regulated transport boxes for egg transport via airplane. As the proposed operation procedure is useful in assisting the monitoring of Ae. albopictus and Ae. aegypti in low-resource settings, Aedes researchers are encouraged to follow it for the sampling and transport of Aedes eggs.
The risk of increasing dengue (DEN) and chikungunya (CHIK) epidemics impacts 240 million people, health systems, and the economy in the Hindu Kush Himalayan (HKH) region. The aim of this systematic review is to monitor trends in the distribution and spread of DEN/CHIK over time and geographically for future reliable vector and disease control in the HKH region. We conducted a systematic review of the literature on the spatiotemporal distribution of DEN/CHIK in HKH published up to 23 January 2020, following Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. In total, we found 61 articles that focused on the spatial and temporal distribution of 72,715 DEN and 2334 CHIK cases in the HKH region from 1951 to 2020. DEN incidence occurs in seven HKH countries, i.e., India, Nepal, Bhutan, Pakistan, Bangladesh, Afghanistan, and Myanmar, and CHIK occurs in four HKH countries, i.e., India, Nepal, Bhutan, and Myanmar, out of eight HKH countries. DEN is highly seasonal and starts with the onset of the monsoon (July in India and June in Nepal) and with the onset of spring (May in Bhutan) and peaks in the postmonsoon season (September to November). This current trend of increasing numbers of both diseases in many countries of the HKH region requires coordination of response efforts to prevent and control the future expansion of those vector-borne diseases to nonendemic areas, across national borders.
Since the 1980s, advances in wastewater treatment technology have led to considerably improved surface water quality in the urban areas of many high income countries. However, trace concentrations of organic wastewater-associated contaminants may still pose a key environmental hazard impairing the ecological quality of surface waters. To identify key impact factors, we analyzed the effects of a wide range of anthropogenic and environmental variables on the aquatic macroinvertebrate community. We assessed ecological water quality at 26 sampling sites in four urban German lowland river systems with a 0–100% load of state-of-the-art biological activated sludge treated wastewater. The chemical analysis suite comprised 12 organic contaminants (five phosphor organic flame retardants, two musk fragrances, bisphenol A, nonylphenol, octylphenol, diethyltoluamide, terbutryn), 16 polycyclic aromatic hydrocarbons, and 12 heavy metals. Non-metric multidimensional scaling identified organic contaminants that are mainly wastewater-associated (i.e., phosphor organic flame retardants, musk fragrances, and diethyltoluamide) as a major impact variable on macroinvertebrate species composition. The structural degradation of streams was also identified as a significant factor. Multiple linear regression models revealed a significant impact of organic contaminants on invertebrate populations, in particular on Ephemeroptera, Plecoptera, and Trichoptera species. Spearman rank correlation analyses confirmed wastewater-associated organic contaminants as the most significant variable negatively impacting the biodiversity of sensitive macroinvertebrate species. In addition to increased aquatic pollution with organic contaminants, a greater wastewater fraction was accompanied by a slight decrease in oxygen concentration and an increase in salinity. This study highlights the importance of reducing the wastewater-associated impact on surface waters. For aquatic ecosystems in urban areas this would lead to: (i) improvement of the ecological integrity, (ii) reduction of biodiversity loss, and (iii) faster achievement of objectives of legislative requirements, e.g., the European Water Framework Directive.
Background. There is growing public and scientific concern about the occurrence of anthropogenic chemicals in the aquatic environment. Surface and groundwater serve as main drinking water resource. Especially in metropolitan areas these water reservoirs are impacted by organic pollutants predominantly originating from wastewater treatment plant (WWTP) effluents. The impact of wastewater derived anthropogenic chemicals is therefore related to environmental and human health concerns. In order to lower the potential environmental and human health risk from wastewater associated pollutants, strategies for enhanced pollutant removal are applicable in a medium-term perspective. Ozonation and powdered activated carbon treatment are the two advanced wastewater treatment technologies, which are technically mature as well as economically feasible for the application in large-scale wastewater treatment plants. While powdered activated carbon removes substances by adsorption, ozonation degrades a parent compound into oxidation products. Most of the available research has been done at lab-scale while onsite ecotoxicity tests and chemical analyses are rare.
Objectives. For a comparative evaluation of advanced wastewater treatments' potential to alter toxicity, a broad spectrum of ecotoxicological data need to be collected. The focus has been set on three major objectives: A) Evaluation of the endocrine activity; B) Evaluation of the unspecific toxicity; C) Evaluation of genotoxicity and mutagenicity.
Methods. The advanced treatment methods, ozonation and powdered activated carbon treatment of secondary wastewater effluents, – each equipped with subsequent sand filtration as additional post treatment step – were ecotoxico-logically characterized at a pilot-scale WWTP. For process control the elimination of 35 selected pharmaceuticals was identified by chemical analyses using HPLC-MS/MS.
The endocrine activity ((anti-)estrogenic, (anti-)androgenic, dioxin-like activity)) was characterized by yeast-based in vitro bioassays and cytotoxicity by cell based assays. Genotoxicity and mutagenicity was assessed using umuC'assay and Ames assay, respectively. All in vitro assays were performed using extracts of the wastewater samples. In vivo toxicity was assessed with the fish early life stage test with rainbow trout (Oncorhynchus mykiss). Ozonation was additionally assessed at a full-scale WWTP with in-vitro tests on endocrine activity and cytotoxicity and in vivo toxicity tests using five aquatic model organisms: Lemna minor, Daphnia magna, Chironomus riparius, Lumbriculus variegatus, Potamopyrgus antipodarum.
Results. In conventional activated sludge treated effluents the residual estrogenicity, antiandrogenicity, aryl hydrocarbon receptor agonistic activity and cytotoxicity were considerably reduced while antiestrogenicity was increased by both advanced treatment technologies. Ozonation led to an increase in genotoxic effects detected with Ames assay and with single cell gel electrophoresis of rainbow trout erythrocytes. Furthermore, mortality of rainbow trout was increased and reproduction of L. variegatus was decreased. Sand filtration lessened the genotoxic effects and adjusted reproduction of L. variegatus and mortality of rainbow trout to a similar level as conventional treatment.
Conclusions. This work demonstrates that conventional activated sludge treatment induces in vitro and in vivo toxicity. Advanced wastewater treatment combined with subsequent sand filtration can reduce in vitro and in vivo toxicity. An observed increase of endocrine activity after advanced wastewater treatment is an indication for different removal efficiencies of chemicals causing agonistic or antagonistic activity, respectively. Ozonation of wastewater generates ecotoxicity, which is largely removed by subsequent sand filtration. After a comprehensive investigation and after assurance of the removal of adverse effects, advanced treatment technologies could have beneficial effects on the ecological quality of the receiving water.
Driven by globalization, urbanization and climate change, the distribution range of invasive vector species has expanded to previously colder ecoregions. To reduce health-threatening impacts on humans, insect vectors are extensively studied. Population genomics can reveal the genomic basis of adaptation and help to identify emerging trends of vector expansion. By applying whole genome analyses and genotype-environment associations to populations of the main dengue vector Aedes aegypti, sampled along an altitudinal gradient in Nepal (200–1300 m), we identify putatively adaptive traits and describe the species' genomic footprint of climate adaptation to colder ecoregions. We found two differentiated clusters with significantly different allele frequencies in genes associated to climate adaptation between the highland population (1300 m) and all other lowland populations (≤800 m). We revealed nonsynonymous mutations in 13 of the candidate genes associated to either altitude, precipitation or cold tolerance and identified an isolation-by-environment differentiation pattern. Other than the expected gradual differentiation along the altitudinal gradient, our results reveal a distinct genomic differentiation of the highland population. Local high-altitude adaptation could be one explanation of the population's phenotypic cold tolerance. Carrying alleles relevant for survival under colder climate increases the likelihood of this highland population to a worldwide expansion into other colder ecoregions.
Background: Driven by globalization, urbanization and climate change, the distribution range of invasive vector species has expanded to previously colder ecoregions. To reduce health-threatening impacts on humans, insect vectors are extensively studied. Population genomics can reveal the genomic basis of adaptation and help to identify emerging trends of vector expansion.
Results: By applying whole genome analyses and genotype-environment associations to populations of the main dengue vector Ae. aegypti, sampled along an altitudinal temperature gradient in Nepal (200- 1300m), we identify adaptive traits and describe the species’ genomic footprint of climate adaptation to colder ecoregions. We found two clusters of differentiation with significantly different allele frequencies in genes associated to climate adaptation between the highland population (1300m) and all other lowland populations (≤ 800 m). We revealed non-synonymous mutations in 13 of the candidate genes associated to either altitude, precipitation or cold tolerance and identified an isolation-by-environment differentiation pattern.
Conclusion: Other than the expected gradual differentiation along the altitudinal gradient, our results reveal a distinct genomic differentiation of the highland population. This finding either indicates a differential invasion history to Nepal or local high-altitude adaptation explaining the population’s phenotypic cold tolerance. In any case, this highland population can be assumed to carry pre-adapted alleles relevant for the species’ invasion into colder ecoregions worldwide that way expanding their climate niche.