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The history of the scientific name of the yellow fever mosquito, the vector of yellow fever virus, ranges from 1757 to the early twenty-first century. In his 1757 work Iter Palæstinum, Frederic Hasselquist gave the name Culex aegypti to a mosquito species responsible for fierce attacks on humans in Egypt. That name was never later ascribed to Hasselquist as author, but to Linnaeus, although the name never appeared in any of Linnaeus' publications. In Cuba, at the end of the nineteenth century, the vector of the unknown infectious agent of yellow fever was first identified as Culex mosquito and later more validly named Stegomyia fasciata. Mosquito taxonomists differed strongly about the name of the mosquito through much of the twentieth century. Interventions by the International Commission on Zoological Nomenclature imposed a biologically invalid specific name, and in the early twenty-first century a phylogenetic analysis of the culicid tribe Aedini restored the genus Stegomyia from a century earlier. That action was short-lived. A phylogenetic reassessment resulted in the return of Stegomyia to subgeneric rank in Aedes; thus, the name of the yellow fever mosquito survives in the traditional classification of convenience as the trinomial Aedes (Stegomyia) aegypti (Linnaeus).
Host identity, habitat type, season, and interspecific interactions were investigated as determinants of the community structure of fleas on wild carnivores in northwestern Mexico. A total of 540 fleas belonging to seven species was collected from 64 wild carnivores belonging to eight species. We found that the abundances of some flea species are explained by season and host identity. Pulex irritans and Echidnophaga gallinacea abundances were significantly higher in spring than in fall season. Flea communities on carnivore hosts revealed three clusters with a high degree of similarity within each group that was explained by the flea dominance of E. gallinacea, P. simulans, and P. irritans across host identity. Flea abundances did not differ statistically among habitat types. Finally, we found a negative correlation between the abundances of three flea species within wild carnivore hosts. Individual hosts with high loads of P. simulans males usually had significantly lower loads of P. irritans males or tend to have lower loads of E. gallinacea fleas and vice-versa. Additionally, the logistic regression model showed that the presence of P. simulans males is more likely to occur in wild carnivore hosts in which P. irritans males are absent and vice-versa. These results suggest that there is an apparent competitive exclusion among fleas on wild carnivores. The study of flea community structure on wild carnivores is important to identify the potential flea vectors for infectious diseases and provide information needed to design programs for human health and wildlife conservation.
Species vulnerability to pesticides depends on physiological sensitivity, the potential to recover, and the ecological context. We assessed the vulnerability of the mosquito Culex pipiens to a repeated treatment with thiacloprid in outdoor microcosms with and without antagonists (competitive and predatory invertebrates). Microcosms were treated repeatedly (three times) with thiacloprid at a concentration of 0.1, 1, or 10 µg/liter. In microcosms without antagonists, the abundance of Cx. pipiens larvae decreased moderately after the second and the third exposures to 10 µg/liter thiacloprid. In microcosms with antagonists, the abundance of Cx. pipiens larvae declined to approximately zero in the control group and the low concentration treatments during the five weeks of observation. By contrast, the abundance of Cx. pipiens larvae temporarily increased at 10 µg/liter thiacloprid after the second and third contamination. We explained this positive effect on the development of Cx. pipiens because of the decrease in competition due to the elimination of sensitive antagonists combined with the high recovery potential of Cx. pipiens. Based on these results, natural antagonists must be supported for the sustainable control of mosquitoes.
Major nuisance species are found among the floodwater mosquitoes and snow-pool mosquitoes, with the former being the main reason for mosquito control in most areas. Nuisance species vary with the area, and previous reports from northern areas conclude that the nuisance is most often caused by snow-pool mosquitoes. We investigated the mosquito fauna and abundances of host-seeking females using CDC traps baited with carbon dioxide, in Övertorneå city near the Arctic Circle in northern Sweden, after earlier complaints about massive mosquito nuisance. The abundance of host-seeking female mosquitoes was high in 2014, with a maximum of ~15,400 individuals per CDC trap night, of which 89% was the floodwater mosquito Aedes rossicus. Surprisingly, the main nuisance species was a floodwater mosquito, occurring at the northernmost location it has ever been recorded in Sweden. Our report is probably the first documentation of such large numbers of Aedes rossicus in any locality and probably the first documentation of a severe floodwater mosquito nuisance near the Arctic Circle. Given the historical data on river discharge in the area, the nuisance is recurrent. We conclude that in northern localities, as well as in more southern localities, production of floodwater mosquitoes is a natural component of the floodplain fauna of rivers with a fluctuating water flow regime. Also, the floodwater mosquitoes Aedes sticticus and Aedes vexans were found north of their formerly known distribution in Sweden.
Establishing reliable risk projection information about the distribution pattern of members of the Culex pipiens complex is of particular interest, as these mosquitoes are competent vectors for certain disease-causing pathogens. Wolbachia, a maternally inherited bacterial symbiont, are distributed in various arthropod species and can induce cytoplasmic incompatibility, i.e., reduced egg hatch, in certain crosses. It is being considered as a tool for population control of mosquito disease vectors. The Aegean region is characterized by highly populated, rural, and agricultural areas and is also on the route of the migratory birds. In this study, a fragment of the 658 bp of the mitochondrial cytochrome c oxidase subunit 1 (COI) gene, which includes the barcode region, was employed to differentiate Cx. pipiens complex species found in this region. Moreover, for the first time, the prevalence of Wolbachia endobacteria in these natural populations was examined using PCR amplification of a specific wsp gene. Our results revealed a widespread (more than 90%, n=121) presence of the highly efficient West Nile virus vector Cx. quinquefasciatus in the region. We also found that Wolbachia infection is widespread; the average prevalence was 62% in populations throughout the region. This study provided valuable information about the composition of Cx. pipiens complex mosquitoes and the prevalence of Wolbachia infection in these populations in the Aegean region. This information will be helpful in tracking mosquito-borne diseases and designing and implementing Wolbachia-based control strategies in the region.
We investigated the nocturnal activity of cave-dwelling sand flies at different time intervals and determined their species composition and seasonal variation. Sand flies were captured on one night each month using CDC light traps from 18:00-06:00 with the collecting bag being changed every two h between February, 2010 and January, 2011. A total of 18,709 individuals, including 10,740 males and 7,969 females, was collected. The overall ratio between male and female specimens was 1:0.74. The collected specimens included 14 species from four genera, Chinius, Idiophlebotomus, Phlebotomus, and Sergentomyia. Sergentomyia phadangensis was the most abundant species (comprising 31.9% of the collected individuals), followed by Se. anodontis (22.8%) and Ph. mascomai (18.2%). The highest number of specimens was collected in July (15.6%), followed by May (15.5%) with the peak of collection recorded at the time interval of 00:01–02:00, followed by 22:01–00:00. However, there were no significant differences observed among time intervals of sand fly collections (p=0.154). Observations of the nocturnal activity of male and female sand flies throughout the night suggest that phlebotomine sand flies show the greatest activity level after midnight.
Increasing winter temperatures are expected to cause seasonal activity of Ixodes ricinus ticks to extend further into the winter. We caught birds during winter months (November to February) at a site in the west of Scotland over a period of 24 years (1993–1994 to 2016–2017) to quantify numbers of attached I. ricinus and to relate these to monthly mean temperature. No adult ticks were found on any of the 21,731 bird captures, but 946 larvae and nymphs were found, with ticks present in all winter months, on 16 different species of bird hosts. All ticks identified to species were I. ricinus. I. ricinus are now active throughout the year in this area providing temperature permits. No I. ricinus were present in seven out of eight months when the mean temperature was below 3.5º C. Numbers of I. ricinus attached to birds increased rapidly with mean monthly temperatures above 7º C. Winter temperatures in Scotland have been above the long-term average in most years in the last two decades, and this is likely to increase risk of tick-borne disease.
Despite the veterinary and medical importance of horse flies, deer flies, and yellow flies, only a few trap types have been evaluated to monitor adult population dynamics. Currently, three trap types are being utilized (H-trap, Horse Pal® (HP), and Nzi trap), but no head-to-head comparisons have been reported. Thus, we conducted comparative trapping studies in Florida and North Carolina. At two study sites in Florida, the efficacy of all three trap types was compared, but only the H-trap and HP were compared in North Carolina. Although trap type was significant at all sites, the trap type which caught the most specimens was not the same. In Florida at the Lower Suwannee Wildlife Refuge (LSWR) site, the H-trap caught the most specimens (2,006), followed in decreasing order by Nzi (938) and HP (541). At the Cedar Ridge Ranch site, the Nzi caught significantly more specimens (1,439) than the H-trap (215) and HP (161), which were not significantly different from each other. In North Carolina, the H-trap caught approximately twice as many specimens as the HP (1,458 vs 720). These trap comparison studies were followed up by a study on the efficacy of various bait combinations: (No Bait (NB), dry ice only (DI), Trap Tech Lure (TTL) only, and DI TTL), which was conducted only at the two Florida sites with H-traps. At both sites, bait combinations significantly affected trap collections. One pattern (DI TTL > DI > TTL > NB) was recorded at the LSWR, while at the Cedar River Ranch the pattern was DI > DI TTL > TTL > NB. Our data showed that trap type and bait combination significantly influence overall adult tabanid abundance as well as individual species composition.
Information about mosquito ecology in the high mountain ecosystems of the Neotropical region is sparse. In general, few genera and species have been reported in these ecosystems and there is no information available on habitats and the mosquitoes occupying them. In the present study, specimens collected from NW Colombia in HME were grouped using larval habitat data via an Operational Taxonomic Unit (OTU) determination. A total of 719 mosquitoes was analyzed belonging to 44 OTUs. The analysis considered habitat features and clustered the specimens into six groups from A-F. Five of these included species from different genera, suggesting common habitat requirements. Group E with four genera, seven subgenera, and six species occupied the highest areas (above 3,000 m), whereas three groups (B, D, F) were detected at lower altitudes (1,960–2,002 m). Bromeliads were the most common larval habitat, with 47% (335/719) of the specimens; five genera, six subgenera, and eight species were identified and classified into 66% (29/44) of the OTUs. This work showed some similarities to the habitat requirements and provides a grouping system that constitutes an important baseline for the classification of mosquito fauna from high mountain ecosystems according to altitude and larval habitat.
Due to their large diversity of potential blood hosts, breeding habitats, and resting sites, zoological gardens represent highly interesting places to study mosquito ecology. In order to better assess the risk of mosquito-borne disease-agent transmission in zoos, potential vector species must be known, as well as the communities in which they occur. For this reason, species composition and dynamics were examined in 2016 in two zoological gardens in Germany. Using different methods for mosquito sampling, a total of 2,257 specimens belonging to 20 taxa were collected. Species spectra depended on the collection method but generally differed between the two zoos, while species compositions and relative abundances varied seasonally in both of them. As both sampled zoos were located in the same climatic region and potential breeding sites within the zoos were similar, the differences in mosquito compositions are attributed to immigration of specimens from surrounding landscapes, although the different sizes of the zoos and the different blood host populations available probably also have an impact. Based on the differences in species composition and the various biological characteristics of the species, the risk of certain pathogens to be transmitted must also be expected to differ between the zoos.
There has been a rapid global expansion of Aedes albopictus, with varying biological characters and vector competence according to geographic and evolutionary origins of the invading populations. Based on mitochondrial gene cytochrome c oxidase I (COI) sequences from both native and invasive regions, genetic characters of Ae. albopictus were examined. Phylogenetic analyses indicate lineage differentiation in the original areas, and only one of the lineages was involved in the worldwide expansion. Multiple invasions were detected in populations in Africa and the Americas, whereas no obvious genetic structure was found in European populations. Asian populations showed high genetic diversity, with 42 private haplotypes being detected in this region. In addition, other genetic divergence has occurred, as in Japan and Pakistan, where populations showed significant differences from all other Asian populations. Altogether, populations in China displayed the highest genetic diversity (Hd=0.946, π=1.609%) and significantly negative Tajima's D (-1.88475) and Fu's FS (-24.43873). This result may be attributable to the insecticide interventions used to control dengue epidemics.
Mosquito-borne diseases are a pervasive public health problem on a global scale, and effective management of them requires well-designed surveillance programs for both vectors and pathogens. Mosquito traps are a common component of such programs, and their reach can be expanded by engaging citizen scientists. In this study in a southern Australian city, we compared the mosquito collection efficacy of two types of traps and assessed their suitability for use in citizen science programs. BG Sentinels and BG Gravid Aedes Trap (BG-GAT) traps both collected Aedes and Culex species in similar proportions, albeit with the former collecting approximately nine times as many mosquitoes. However, BG Sentinels have a greater per unit cost than BG-GATs and are restricted to deployment near power outlets. Importantly, despite being devised for collection of Aedes (Stegomyia) dengue vectors (such as Aedes aegypti), both traps can be effectively used in temperate climates for collection of a range of mosquito species. These traps could conceivably be used in citizen science programs to enhance the reach of surveillance at reduced cost.
We focused on the analysis of biological parameters of two different abundant populations of Dipetalogaster maximus (Uhler) (Hemiptera: Reduviidae: Triatominae) from northwestern Mexico. The biological parameters were related to hatching of eggs, life cycle, and meal needed for molting by each instar of two populations from environmentally similar areas (El Fandango and San Dionisio) with a similar number of available hosts as blood meal sources. The D. maximus populations from the two locations were evaluated and compared. No significant differences (P>0.05) were recorded for the average hatching time of the two cohorts. The median egg-to-adult development time and the number of blood meals at each nymphal group were significantly shorter (P<0.05) for the El Fandango cohort. The number of obtained females at the end of the cycles, number of eggs laid, and rate of egg hatching were significantly higher (P<0.05) for the El Fandango cohort. These results contribute to the estimation of abundances of the studied populations of D. maximus in areas where many tourists go for camping and have an increased risk of being bitten and infected by this species.
Culex pipiens, the endemic mosquito vector of West Nile virus in eastern North America, is responsible for maintenance of the virus in avian reservoir hosts, the most important of which appears to be the American robin. One reason for the greater involvement of robins is believed to be the feeding preference of Cx. pipiens, however, the basis of this preference is not understood. We tested the hypothesis that the species-specific chemical profile of avian uropygial gland secretions are used by Cx. pipiens as cues to locate birds and, therefore, may contribute to the observed feeding preferences. We used gas chromatography-mass spectrometry to identify the semi-volatile components of the uropygial gland secretions of American robins and two other common reservoir host species, the house sparrow and European starling. We found that the chemical composition of the robin secretions was different from those of the sparrows and starlings. Through behavioral choice trials conducted in a dual-port olfactometer, we also found that Cx. pipiens did not prefer the secretions of robins over the other two species. Surprisingly, however, we found that Cx pipiens were more often attracted to live starlings over robins and to the secretions of starlings over those of robins.
Few studies have assessed the effects of food scarcity or excess on the life history traits of Aedes aegypti (L.) (Diptera: Culicidae) independently from larval density. We assessed immature survival, development time, and adult size in relation to food availability. We reared cohorts of 30 Ae. aegypti larvae from newly hatched to adult emergence with different food availability. Food conditions were kept constant by transferring larvae each day to a new food solution. Immature development was completed by some individuals in all treatments. The shortest development time, the largest adults, and the highest survival were observed at intermediate food levels. The most important effects of food scarcity were an extension in development time, a decrease in the size of adults, and a slight decrease in survival, while the most important effects of food excess were an important decrease in survival and a slight decrease in the size of adults. The variability in development time and adult size within sex and treatment increased at decreasing food availability. The results suggest that although the studied population has adapted to a wide range of food availabilities, both scarcity and excess of food have important negative impacts on fitness.
We sampled mosquitoes across 18 sites established at different elevations and stretching from the north to the south of Isla Santa Cruz, Galápagos. Two commonly occurring species, Ae. taeniorhynchus and Cx. quinquefasciatus, were collected along with environmental variables characteristic of the trapping sites to assess their influence on mosquito abundance and occurrence in the dry season of 2015. We captured Ae. taeniorhynchus at 14 out of 18 sites and Cx. quinquefasciatus at low and high elevation sites on Santa Cruz. We utilized two generalized linear models; the first assessed the influence of environmental variables on abundances of Ae. taeniorhynchus and the second assessed the influence of these variables on the presence of Cx. quinquefasciatus. Populations of both mosquito species declined with elevation. Rainfall data were limited, as we sampled during the dry season of 2015. Distance to mangroves and maximum humidity were significant in influencing the abundance of Ae. taeniorhynchus, while maximum humidity was found to significantly influence the presence of Cx. quinquefasciatus. Both species occurred in sites where temperature, precipitation, and humidity should allow for mosquito development as well as parasitic development of the protozoan parasites that cause avian malaria. Further research involving year-round sampling of mosquitoes and accompanying meteorological data as well as experimental studies on vector competence are required to understand disease dynamics of parasites such as avian malaria in Galápagos.
In the southern Appalachia of the U.S., Aedes mosquitoes maintain and transmit La Crosse virus (LACV) which causes La Crosse encephalitis, a neuroinvasive disease of children. In response to mosquito outbreaks, communities organize prevention, detection, and response measures that are dependent on local characteristics of the mosquito population and the community. Knowing Ae. albopictus is an accessory vector of LACV and a nuisance biter, our objective was to build a system of ordinary differential equations to model dynamics in a single season using our data and readily available environmental variables that can reflect the abundance and activity of Ae. albopictus. Consequently, we built an Ae. albopictus single-season mathematical model for eastern Tennessee to fit our 2013 mosquito collection data in order to understand the population fluctuations. We included precipitation, temperature, and rate of change of temperature in the model because Aedes mosquitoes oviposit desiccant tolerant eggs with peak activity occurring over 26° C and those data are readily available and used frequently as forecast predictors. Our ordinary differential equation model accurately fits the data and facilitates predictions and better understanding of Ae. albopictus populations in southern Appalachia.
Nesotriatoma confusa sp. nov. (Hemiptera, Reduviidae, Triatominae) is described based on specimens from Cuba. From one male, one female, and eleven nymphs of a then-undescribed species of Nesotriatoma collected in Cuba, a colony was formed and its specimens were used to describe N. confusa sp. nov. Characters were observed on the head, thorax, abdomen, female external genitalia, and male genitalia with optical microscopy and scanning electron microscopy. We concluded that N. bruneri (Usinger, 1944) was indeed a synonym of N. flavida (Neiva, 1911) as previously proposed.
Bird-biting mosquitoes act as bridge vectors of diverse pathogens of emerging infectious diseases. In this study, we report for the first time the abundance, diversity, distribution, and feeding pattern of bird-biting mosquitoes on an island where avifaunal diversity is rich. Monthly mosquito collections were done at six different habitats in three different climatic zones using bird-baited traps over a year. Collected mosquitoes were identified using morphological and molecular tools. A total of 2,655 bird-biting mosquitoes of eight genera and 25 species were identified. Of these, 52% were Culex species, which represents 35% of the Culex species in the country. The most abundant species were Culex sitiens, Cx. pseudovishnui, Cx. nigropunctatus and Cx. quinquefasciatus, whereas the latter two were common to all habitats. The highest abundance was reported in lowland forests (49.6%), while it was lowest in highland forests (22.3%). Highest species similarity was reported from highland forests. Seasonal variations of the most abundant species were significantly different in selected habitats (p< 0.05). Two distinct biting peaks were identified, from 06:00 to 21:00 and 22:00 to 02:00. The biting nature of identified ornithophilic mosquitoes suggests the potential vector status of these mosquitoes.
Bruno M. Carvalho, Thiago Vasconcelos dos Santos, Iorlando da R. Barata, José Aprígio N. Lima, Fernando T. Silveira, Mariana M. Vale, Paul D. Ready, Elizabeth F. Rangel
In southeast Amazon, Lutzomyia (Nyssomyia) flaviscutellata is the incriminated vector of Leishmania (Leishmania) amazonensis, a causative agent of zoonotic cutaneous leishmaniasis (CL). The optimal methods for surveying Lu. flaviscutellata were investigated in the Bragança region, northeast Pará State, Brazil, selected for the presence of Le. amazonensis. The performances of modified Disney traps and CDC light traps were compared in four ecotopes within and around four village transects during the wet and dry seasons. The physiological age of female sand flies was estimated and natural infection by flagellates was evaluated by dissection. Disney traps were better for detecting the presence of Lu. flaviscutellata, while CDC traps performed well for detecting Lutzomyia (Nyssomyia) antunesi, suspected vector of Leishmania lindenbergi. The former was more abundant during the wet season, when female flies were naturally infected with Le. amazonensis. These findings identified the environments of local transmission. In order to improve surveys of Lu. flaviscutellata as part of integrated epidemiological surveillance of CL, our recommendations include focusing vector surveys with Disney traps on forest fragments where people work, during the seasonal peak of the vector. Further field studies are required to make model-based predictions of seasonal variations in the vectorial capacity of vector populations.
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