SEARCH · Search PubMed

Results for “CULEX”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 37 records · Page 2Linked to original sources

PubMed2006

Seasonal abundance of Culex restuans and Culex pipiens in southwestern Virginia through ovitrapping.

Ovitrap collections were done to determine the seasonal distribution and ovipositional activity of Culex restuans and Culex pipiens in southwestern Virginia during summers 2002 and 2003. In both years, Cx. restuans was the first species collected and was the dominant species throughout the collecting period. More than 90% of the collections were comprised of Cx. restuans. Two oviposition peaks occurred in both years for Cx. restuans, the first in June and second in the middle of July. Culex pipiens made up less than 7% of the total catch and started to occur in the traps in the middle of the trapping season with a peak occurring in August. Although ovipositional activity began to decline for Cx. restuans, at the end of the trapping period, there was a slight increase in ovipositional activity for Cx. pipiens, but not enough to result in a crossover. A third species, Culex salinarius, was collected in the traps, but the total number of egg rafts accounted for less than 1% of the total collection.

Animals↗

PubMed1983

Comparative vector competence of Culex tarsalis and Culex quinquefasciatus from the coachella, imperial, and San Joaquin Valleys of California for St. Louis encephalitis virus.

St. Louis encephalitis (SLE) virus has continued to be active in the Colorado Desert region of Southern California (Coachella and Imperial Valleys) since 1973, while it has virtually disappeared from the Sacramento and San Joaquin Valleys of Central California. Consequently, comparative vector competence studies were undertaken from 1978 to 1981 to evaluate the susceptibility of populations of Culex quinquefasciatus and Culex tarsalis from the San Joaquin and Coachella/Imperial Valleys to oral infection with representative SLE viral strains from each geographical area. Culex quinquefasciatus females from both areas were equally susceptible to infection with both viral strains by the pledget and viremic chick feeding techniques. Although susceptibility profiles were similar by both feeding techniques, infection thresholds (i.e., ID50S) obtained with Cx. quinquefasciatus females were at least 10,000-fold lower when fed on viremic chicks than on virus soaked pledgets. Culex tarslis females from the two geographical areas were equally susceptible to infection with the indigenous viral strain by feeding on pledgets, and were uniformly more susceptible than sympatric populations of Cx. quinquefasciatus. Thus, differences observed in SLE viral activity in different geographical areas of California since 1973 cannot be explained by differences in the susceptibility of Cx. quinquefasciatus or Cx. tarsalis to oral infection with SLE virus.

Animals↗

PubMed2002

Seasonal abundance of Culex nigripalpus Theobald and Culex salinarius Coquillett in north Florida, USA.

North Florida is a transition zone between widespread Culex nigripalpus populations to the south and focal Culex salinarius populations to the north. Culex nigripalpus is a vector of St. Louis encephalitis (SLE) and eastern equine encephalitis (EEE) viruses in south Florida, while Cx. salinarius is a suspected New World vector of West Nile (WN) virus. Abundant vector populations are often a prerequisite for epidemic and epizootic transmission of arboviruses. Extensive SLE transmission has never been reported from north Florida, but sporadic WN transmission was reported there during the summer of 2001. The disparate flavivirus transmission patterns observed in north and south Florida may be due, in part, to the local geographical and seasonal distribution of Culex vectors. Here we report that from May 1991 to April 1994, Cx. salinarius was most commonly observed during the winter and spring in northeast Florida (Duval County), whereas Cx. nigripalpus was most abundant during the summer and autumn. An unusually mild spring in 1991 allowed Cx. nigripalpus to reproduce early in the year, resulting in a summer population that emerged more than 8 wks earlier than in 1992 and 1993. The 1991 Cx. nigripalpus population persisted through October, when SLE transmission was detected by sentinel chickens. Transmission of SLE was not detected in Duval County during 1992 or 1993. These data indicate that mild winter and spring conditions in north Florida may favor increased abundance and survival of Cx. nigripalpus in a region where this species is normally not abundant. A seasonal shift in population structure may increase the transmission risk of arboviruses for which Cx. nigripalpus is a competent vector, including SLE, WN, and EEE.

Animals↗

PubMed1996

Restriction analysis of the ribosomal DNA internal transcribed spacer region of Culex restuans and mosquitoes in the Culex pipiens complex.

Members of the Culex pipiens Linn. complex in the eastern, southern, and central United States are the primary vectors of St. Louis encephalitis virus. Although species and subspecies in the complex can be identified as 4th-instar larvae and by characters on the male genitalia, adult females cannot be identified accurately. In this study a ribosomal DNA (rDNA) segment that includes the internal transcribed spacer region (ITS) was amplified from Culex pipiens pipiens Linn., Culex quinquefasciatus Say, and Culex restuans Theobald. The DNA was amplified from single abdomens or single legs. The amplified rDNA segment from Cx. restuans is 90 base pairs smaller than those from members of the Cx. pipiens complex. Ribosomal DNA was amplified separately from 3 individuals for each population of Cx. pipiens and analyzed by restriction digestion. Intrapopulation variation is seen, because for each population, bands are present that are common to all 3 individuals within the population, but are also unique to that population. These results indicate that this method may provide a means for distinguishing among the mosquitoes in the Cx. pipiens complex.

Animals↗

PubMed1976

Comparison of the lipid composition of Culex quinquefasciatus and Culex tritaeniorhynchus cells obtained from the logarithmic and stationary phases of growth.

Culex quinquefasciatus and Culex tritaeniorhynchus cells were grown in spinner culture medium. The cells were harvested at late logarithmic and stationary phases of growth. The total lipid, total neutral lipid, and total phospholipid contents of the cells were analyzed to determine changes that occurred in the fatty acid profiles of the lipids with aging and between species. There was an increase in the amount of total neutral lipids with a corresponding decrease in amount of total phospholipid from logarithmic to stationary phases of growth of the Culex quinquefasciatus cells. Chain elongation and/or desaturation of acids occurred with aging of cells. The fatty acids of the phospholipids had a longer average chain length than the neutral lipids.

Animals↗

PubMed2005

Oviposition responses of culex pipiens to a synthetic racemic Culex quinquefasciatus oviposition aggregation pheromone.

The oviposition pheromone of Culex quinquefasciatus was synthesized in a racemic form in a simple (five steps), efficient, high yielding (45% total yield), and low cost way (use of relatively low cost reagents). Our synthetic racemic pheromone (SRP) was tested in the laboratory for its bioactivity on Culex pipiens biotype molestus, which is a member of the species complex that Culex quinquefasciatusbelongs. In the testing conditions, bioactivity at the doses of 0.01, 0.1, 1, and 10 microg per cage was found with the best bioactivity achieved at 1 mug per cage. The effectiveness of our SRP offers a capable tool for improving mosquito oviposition traps for surveillance or even control programs.

Animals↗

PubMed1996

Phylogeny of fourteen Culex mosquito species, including the Culex pipiens complex, inferred from the internal transcribed spacers of ribosomal DNA.

Ribosomal DNA sequence divergence in the internal transcribed spacer regions (ITS-1 and ITS-2) was examined for fourteen species and four subgenera (sixty-two clones) in the mosquito genus Culex (Diptera: Culicidae). A neighbour-joining tree produced with Kimura 2-parameter distances showed that each of the four subgenera was monophyletic at confidence probabilities of 70-99%. Culex (Lutzia) formed the sister group of Cx. (Culex). Two major clades, a Cx. pipiens complex-Cx. torrentium assemblage and a Cx. restuans-Cx. salinarius-Cx. erythrothorax assemblage, formed monophyletic groups. Cx. torrentium was closely related to members of the Cx. pipiens complex. Phylogenetic analysis of ITS-1 and ITS-2 sequences from members of the Cx. pipiens complex separated populations from northern latitudes and southern latitudes, but did not support the traditional taxa as monophyletic units.

Animals↗

PubMed2006

Impact of trap elevation on estimates of abundance, parity rates, and body size of Culex pipiens and Culex restuans (Diptera: Culicidae).

Trapping success, abundance, parity rate, and body size indices of Culex pipiens (L.) and Culex restuans Theobald, important vectors of West Nile virus (family Flaviviridae, genus Flavivirus, WNV), were determined for specimens captured from both ground level (approximately 1-m) and elevated (approximately 6- to 7-m) CO2-baited CDC miniature light traps. Mosquitoes were collected from six study sites in Albany County, New York, from mid-May to mid-October 2004. There was no significant difference in abundance or mean parity for either Cx. pipiens or Cx. restuans between the elevated and the ground-level traps. Mosquitoes collected in elevated traps tended to be larger than mosquitoes collected at ground level. Elevated traps captured significantly fewer mosquitoes per trap-night than did ground traps, but a greater proportion of those captured were Culex spp. Therefore, elevated traps more efficiently captured Cx. pipiens and Cx. restuans with similar reproductive status and body size and reduced the time necessary to sort and identify collections. These findings may be beneficial to researchers or surveillance programs focusing on Cx. pipiens or Cx. restuans.

Animals↗

PubMed1999

Oviposition responses of gravid Culex quinquefasciatus and Culex tarsalis to bulrush (Schoenoplectus acutus) infusions.

Laboratory bioassays demonstrated that fermented infusions of dried bulrushes (Schoenoplectus acutus) strongly attracted and stimulated oviposition by gravid female Culex quinquefasciatus and Culex tarsalis. The responses of the 2 species varied with the concentration and method of preparation of the infusions, with responses generally increasing with increasing concentration. No major differences were found in the responses of either species to infusions prepared with bulrushes alone, or with bulrushes plus lactalbumin hydrolysate and brewer's yeast. Infusions remained more attractive than distilled water controls to both species for up to 8 wk. Field tests corroborated the results from the laboratory bioassays. Culex quinquefasciatus, Cx. tarsalis, and Cx. stigmatosoma egg rafts were collected from water pan traps baited with bulrush infusions. A few Culiseta incidens eggs also were collected. In multiple-choice tests using gravid female or egg traps, Cx. quinquefasciatus preferred the most concentrated bulrush infusions, whereas Cx. tarsalis preferred intermediate concentrations. Female Cx. stigmatosoma and Culiseta incidens also were attracted. Overall, these results may provide new leads towards developing synthetic chemical baits to attract bloodfed mosquitoes.

Animals↗

PubMed2002

Positive findings of Borrelia burgdorferi in Culex (Culex) pipiens pipiens larvae in the surrounding of Brno city determined by the PCR method.

After first finding Borrelia in the midgut of imago mosquitoes, we concentrated on the presence of Borrelia in mosquito development stages--larvae of the third or fourth instar. In the summer season in the years of 2000-2001 a total of 439 Culex (Culex) pipiens pipiens larvae were collected from a barrel of rainwater in the Obrany holiday area of Brno city (East Moravia, Czech Republic). The larvae midgut was observed under dark-field microscopy. Ten DFM positive samples (2.28%) were further analysed using the single-tube nested PCR method for the presence of flagellum DNA sequence specific for Borrelia burgdorferi sensu lato, of which 5 were positive. Borrelian positivity of Culex (C.) pipiens pipiens larvae was 1.14%. One spirochete isolated strain in BSK-H medium was obtained. PCR detection for borrelian DNA of the isolated strain was negative. From these results we can conclude that a low percentage Borreliae can be also found in mosquito larvae and are likely to survive into imago stage.

Animals↗

PubMed1992

Conservation of the names Culex stigmatosoma and Culex thriambus.

As a result of action by the International Commission on Zoological Nomenclature, the name Culex peus Speiser is suppressed and never to be used as a valid name, and the names Culex stigmatosoma Dyar and Culex thriambus Dyar are conserved for the western banded foul-water mosquito and the related southwestern U.S. species, respectively.

Animals↗

PubMed2006

Modeling the impact of variable climatic factors on the crossover of Culex restauns and Culex pipiens (Diptera: culicidae), vectors of West Nile virus in Illinois.

The aim of this study was to model the impact of temperature on the timing of the seasonal shift in relative proportion of Culex restuans Theobald and Culex pipiens L. in Illinois. The temporal pattern of West Nile virus (WNV) and St. Louis encephalitis virus transmission in the midwest exhibits a late summer to early fall peak in activity, which parallels the temporal increase in the abundance of Cx. pipiens. The daily number of egg rafts oviposited by each species has been monitored at multiple surveillance sites in Urbana-Champaign in central Illinois for more than 13 years. The time when the two Culex species are in equal abundance (crossover) varies considerably from year to year. Our investigation of several thermal measures indicated that this variation was related in large part to climatic conditions with warmer (cooler) temperatures correlated to earlier (later) crossover dates. Models based on degree days and the number of days in which the daily maximum temperature exceeded an upper temperature threshold explained more than 60% of the variance in crossover dates. In contrast, models based on the number of days in which the daily minimum temperature exceeded a lower temperature threshold explained no more than 52% of the variance. An evaluation of these models demonstrated that they provide relatively simple and accurate estimates of crossover date from daily temperature data, a necessary component for developing an overall climatic index for the risk of WNV transmission in Illinois.

Animals↗

PubMed1989

[The presence of the Culex (Culex) neavei mosquito in Madagascar, its relevance in the transmission of arboviruses].

A study was made of 25 male and 43 female mosquitoes belonging to the Culex (Culex) univittatus group, from different localities in Madagascar, Indian Ocean. This showed that Culex neavei Theobald, 1906 is present on the island, at least in the Tsiroanomandidy region. As demonstrated previously, Cx. univitatus Theobald, 1901 is also present. Because of the presence of some atypical forms, firm identifications was made only in males according to the structure of the leaflet of the sub-apical lobe of the gonocoxite. The relevance of the presence of Cx. neavei to the epidemiology of West Nile and Babanki viruses in Madagascar is discussed.

Animals↗

PubMed1998

Ovicidal activity of neem products (azadirachtin) against Culex tarsalis and Culex quinquefasciatus (Diptera: Culicidae).

Bioactive compounds contained in the seed kernel and other parts of the neem tree (Azadirachta indica A. Juss) have been found to show insecticidal activities and other effects in many species of insects. These activities include antifeedancy, growth regulation, fecundity suppression, male sterility, oviposition repellency, changes in biological fitness such as loss of flying ability, immunodepression, enzyme inhibition, splitting of biological rhythms, and so forth. We investigated the ovicidal effects of various formulations of azadrirachtin (AZ) against the mosquitoes Culex tarsalis Coquillett and Culex quinquefasciatus Say. The formulations tested were wettable powder Azad WP10, emulsifiable concentrate Azad EC4.5, and technically pure AZ. The ovicidal activity of the test neem products was influenced by concentration of AZ, age of the egg rafts, and age of the neem preparations. Other factors such as formulation and mosquito species were also involved in the degree of ovicidal activity. When the egg rafts were deposited directly in fresh neem suspension and left there for 4 h before transfer to untreated water, 1 ppm of AZ produced almost 100% mortality in eggs. When egg rafts aged for 0, 4, 8, 12, and 24 h were exposed to 10 ppm neem suspensions for 36 h, the ovicidal activity was only attained in the egg rafts deposited directly (0 h old) in the neem suspension, not in those with ages of 4-24 h. On aging, depending on the formulations and mosquito species, the neem suspensions at 1 ppm completely lost ovicidal activity within 7-20 days. The egg rafts of Cx. quinquefasciatus were more susceptible to the test neem products than those of Cx. tarsalis. The formulated neem products were more persistent and effective than the technical AZ. The wettable powder (WP) formulation was slightly more persistent and effective than the emulsifiable concentrate (EC). The ovicidal activity of the neem products against mosquitoes from the current research clearly demonstrated the potential of neem products as possible ovicides against Culex mosquitoes.

Animals↗

PubMed1996

The prey consumption and prey preference of the larvae of the mosquito Culex (Lutzia) raptor on the larvae of Culex quinquefasciatus.

The maximum consumption of the larvae of the pest and vector mosquito Culex quinquefasciatus by the predatory mosquito Culex (Lutzia) raptor was studied at various instars of both the predator and the prey. The prey preferences of the predator when given lavae of different instars were also investigated. The IVth instar of the predator consumed the maximum number of Ist instar and the maximum biomass of IVth instar larvae of the prey. Instars I and II of the predator preferred the Ist of the prey; instars III and IV of the predator preferred instars II and III of the prey respectively. The predator consumed an average of 157.1 larvae during its whole larval period, when each instar of the predator was given its preferred instar of the prey.

Animals↗

PubMed1989

Environmental factors influencing oviposition by Culex (Culex) (Diptera: Culicidae) in two types of traps.

Seasonal and habitat influences on the egg-laying activity of four species of Culex were compared in south Florida using jar- and vat-type oviposition traps. Egg rafts of Culex nigripalpus Theobald, Cx. quinquefasciatus Say, and Cx. salinarius Coquillett were collected in every month of the year, but rafts of Cx. restuans Theobald were absent during spring and summer. Cx. nigripalpus was the dominant species in the summer and fall, and Cx. quinquefasciatus and Cx. salinarius peaked during the winter and spring. Cx. restuans oviposited most rafts in the fall (98.4%). Most Cx. nigripalpus egg rafts were laid in vats (88.5%), and most Cx. quinquefasciatus egg rafts were deposited in jars (58.7%). Fewer Cx. quinquefasciatus rafts were found in a wooded area (32.4%) with a dense undergrowth than in a more open area (67.6%), but Cx. nigripalpus showed no ovipositional preference between these two habitats. The number of rafts oviposited by all species was reduced during periods of rainfall.

Animals↗

PubMed1990

Oviposition behavior of natural populations of Culex tarsalis and Culex restuans (Diptera: Culicidae) in artificial pools.

Natural populations of Culex restuans Theobald and Cx. tarsalis Coquillett in Manitoba, Canada, preferred to oviposit in artificial pools (ovipools) where lawn sod used as an attractant was renewed regularly during the season. The sod medium was unattractive to most Cx. restuans after three weeks in the spring, after one week in midsummer, and after two weeks in autumn; it was unattractive to most Cx. tarsalis after three weeks. Cx. restuans was the first Culex spp. to oviposit each spring, and in 1986 overwintered females of Cx. restuans began ovipositing four weeks before those of Cx. tarsalis. Both species continued to oviposit until September between 1984 and 1987 or until the mean weekly air temperatures dropped to 12 degrees C. Cx. restuans selected shaded oviposition pools, located under a tall, dense tree canopy, while Cx. tarsalis selected open-field, unshaded pools. CO2-baited light trap collections of adults near the oviposition site showed that Cx. restuans females were underrepresented in comparison with the number of egg rafts collected.

Animals↗

PubMed1990

Establishment and characterization of a cell line from the mosquito Culex (Culex) theileri (Diptera: Culicidae) and its susceptibility to infection with arboviruses.

The mosquito Culex (Culex) theileri Theobald is probably the major vector of Rift Valley fever (RVF) virus during epizootics on the inland plateau of southern Africa. A cell line was established from the tissues of this mosquito species to facilitate laboratory studies on RVF and other arboviruses. After temperature pretreatment, egg rafts from a laboratory colony were disinfected, mechanically disrupted, and grown in preconditioned Eagles minimum essential medium supplemented with 10% fetal calf serum. The cells were characterized by their protein content, karyology, and their susceptibility to three arboviruses. Although high infectivity titers were obtained, no cytopathic effects were produced by these viruses. The cell line was shown to be free from latent viruses. These results show that this cell line may be employed fruitfully in arbovirus studies.

Animals↗