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At least 19 recordsLinked to original sources
PubMed2003

Polymerase chain reaction assay identifies Culex nigripalpus: part of an assay for molecular identification of the common Culex (Culex) mosquitoes of the eastern United States.

Nucleotide sequence information on internal transcribed spacer (ITS) 1 and ITS 2 regions of the nuclear ribosomal DNA multigene family was used to develop a polymerase chain reaction assay that identifies Culex nigripalpus Theobald. The assay uses species-specific forward and reverse primers for Cx. nigripalpus and can be used along with previously described primers to distinguish among 4 common taxa of Culex (Culex) of the eastern USA with a single thermal cycler program. The assay distinguishes among the 4 taxa Cx. nigripalpus, Cx. restuans Theobald, Cx. salinarius Coquillett, and members of the Cx. pipiens Linnaeus complex. This assay may be used to verify the morphological identification of individual specimens of Culex or to confirm the species composition of mosquito pools.

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PubMed1995

Studies on mosquitoes (Diptera: Culicidae) and anthropic environment. 10- Survey of adult behaviour of Culex nigripalpus and other species of Culex (Culex) in south-eastern Brazil.

A survey of adult behaviour of Culex (Culex) species was carried out from August 1992 through December 1993 in a human modified (anthropic) environment in the Ribeira Valley, S. Paulo State, Brazil. Culex nigripalpus dominated the catches at several sites and it's tendency to increase in the anthropic environment became quite clear. Nevertheless no high level of synanthropy was demonstrated. So it seems that the mosquito may have a restricted role in natural arbovirus cycles. Nonetheless, Cx. nigripalpus must be considered a potential vector of arboviruses, especially St. Louis encephalitis virus outside dwellings.

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PubMed2001

Description of immature stages of Culex ocossa Dyar & Knab, Culex delpontei Duret and Culex pereyrai Duret of the Melanoconion subgenus (Diptera: Culicidae).

The larva and pupa of Culex (Melanoconion) ocossa Dyar & Knab are redescribed and those of Culex (Melanoconion) delpontei Duret and Culex (Melanoconion) pereyrai Duret are described from specimens collected in the states of São Paulo and Paraná, Brazil. The pupa of Cx. ocossa differs from those of the other two species in having seta 5-IV-VI dark with strongly aciculated branches, and caudolateral angle of segment VIII produced into sharp point, and seta 1-P present; Cx. delpontei can be distinguished from Cx. pereyrai in possessing paddle lightly tanned, trumpet flared, and wing and leg cases lightly tanned, without pattern of dark spots; Cx. pereyrai can be recognized by having wing case with pattern of dark, discontinuously pigmented, longitudinal lines, and trumpet cylindrical, not flared. The larvae of the three species share the presence of seta 2-C placed medially to seta 1-C.

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PubMed2000

Vector competence of Aedes aegypti, Culex sitiens, Culex annulirostris, and Culex quinquefasciatus (Diptera: Culicidae) for Barmah Forest virus.

Aedes aegypti (L.), Culex sitiens Weidemann, Culex annulirostris Skuse, and Culex quinquefasciatus Say mosquitoes colonized at the Queensland Institute of Medical Research, Brisbane Australia, were fed on blood containing Barmah Forest virus (BF). Only Cx. annulirostris was susceptible to infection, with a median cell culture infectious dose (CCID50) of 10(3.36) per mosquito. Ae. aegypti and Cx. quinquefasciatus were infected experimentally, but at rates of < 9%. Cx. sitiens did not become infected. Infection rates for Cx. annulirostris fed 10(3.5) CCID50 of virus per mosquito, varied from 9 to 50% between 2 and 13 d after infection. Virus transmission to suckling mice by Cx. annulirostris occurred from 2 d after infection. Transmission of BF virus by Cx. annulirostris was 10% at 2 d after infection and did not exceed 8% thereafter. Although Cx. annulirostris may be infected and is able to transmit BF virus to suckling mice, it is nonetheless a relatively inefficient vector of the virus.

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PubMed2001

Antigen distribution pattern of West Nile virus in Culex tritaeniorhynchus, Culex vishnui and Culex pseudovishnui mosquitoes.

Distribution of West Nile (WN) virus antigen in different tissues of mosquitoes was studied in three species viz., Culex tritaeniorhynchus, C. vishnui and C. pseudovishnui. Overall per cent positivity was higher in the intra thoracically inoculated as compared to the orally infected mosquitoes, suggesting the existence of a midgut barrier. In a small number of mosquitoes salivary glands were found negative even though fluorescence was seen in the respective head squashes, suggesting salivary gland barrier in these mosquitoes. There was no difference in the per cent salivary gland and salivary gland area positivity between these three species. Presence of virus antigen in the ovaries of these three species on the 3rd post infection day suggests the possibility of transovarial transmission of virus even in the first gonotrophic cycle, which is of epidemiological importance.

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PubMed1999

Eryngium spp. (Umbelliferae) as phytotelmata and their Culex (Culex) inhabitants in temperate Argentina.

The host-plant fidelity, seasonality, and population dynamics of 3 species of Culex (Culex) were examined from monthly samples of mosquito immatures extracted from the leaf axils of Eryngium pandanifolium and Eryngium cabrerae growing sympatrically in the Punta Lara region of Buenos Aires Province, Argentina. Culex hepperi was collected only from E. pandanifolium, and abundance peaks of its larvae and pupae were asynchronous in forest and field habitats. However, the proportion of plants positive for Cx. hepperi, as well as larval densities and developmental success, did not differ between forest and field. Culex renatoi was collected only from E. cabrerae in the field habitat. The monthly numbers of Cx. hepperi and Cx. renatoi were not significantly correlated with the proportion of their host plants that held water. The stage-specific distributions of Cx. hepperi and C. renatoi numbers were highly skewed towards 1st instars and did not differ between species or, for Cx. hepperi, between forest and field habitats. Culex castroi was collected regularly from the axils of both species of Eryngium, but usually in lesser numbers than either Cx. hepperi or Cx. renatoi. Association analyses indicated significant positive associations between Cx. castroi and the other 2 culicine species in host plants. Culex renatoi occurred preferentially in small E. cabrerae, but Cx. castroi did not discriminate plants based on their size. These 3 species of Culex are known only from Eryngium spp. phytotelmata. We suggest that their host-plant specificity is maintained by oviposition preferences, which are more highly selective for Cx. hepperi or Cx. renatoi than for Cx. castroi.

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PubMed1976

Neutral lipid composition of Culex quinquefasciatus and Culex tritaeniorhynchus cells at two phases of growth.

The mosquito cells Culex quinquefasciatus and Culex tritaeniorhynchus were grown in spinner cultures. The fatty acid profiles of the neutral lipid classes were analyzed, and comparisons were made between the two species at logarithmic and stationary phases of growth and between the species and the medium. The results from the data suggest an increase in the average chain length of the fatty acids in the free fatty acid and sterol ester fractions of the Culex quinquefasciatus cells with aging. From the logarighmic to stationary phase, both Culex cells showed some increase in desaturation of acids in the di- and triglyceride and free fatty acid fractions. The Culex tritaeniorhynchus cells also showed some increase in desaturation of acids in the monoglyceride fraction. Differences between the two Culex species at the logarithmic phase of growth were observed in the fatty acid profiles of all the neutral lipid fractions examined and at the stationary phase of growth in the free fatty acid, triglyceride, and sterol ester fractions.

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PubMed1996

Oviposition preferences of Culex pipiens and Culex restuans for infusion-baited traps.

The number of egg rafts oviposited by Culex pipiens and Culex restuans in infusion-baited ovitraps varied with the type of infusion substrate, infusion age, method of infusion preparation, and calendar date. In one or more tests, more Culex egg rafts were collected from water infused with Kentucky bluegrass sod, mixed grass clippings, straw, or a commercial rabbit chow than from a water control. Infusions prepared with oak leaves, maple leaves, and sod soil were ineffective as Culex oviposition attractants; however, alfalfa infusions ranged from marginally effective to unattractive. Rabbit chow infusions required one or more reinfusions before becoming active oviposition lures when prepared in unconditioned (unused) ovitraps. Infusions prepared in conditioned ovitraps (those that had previously contained the same type of infusion) had shorter delay periods. Effective oviposition lures for Culex species included continuous infusions, such as sod and sod grass, and those in which the substrate was infused in the water for only a brief period (24-48 h), such as infusions of rabbit chow and mixed grass clippings. The percentage of egg rafts from Cx. restuans was usually greater in sod and grass infusions than in rabbit chow infusions, whereas Cx. pipiens showed a slight preference for rabbit chow infusions over sod and grass infusions. The temporal shift in relative oviposition activity of the 2 Culex species (cross-over) varied from year to year and between sites in one year.

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PubMed1976

Phospholipid composition of Culex quinquefasciatus and Culex tritaeniorhynchus cells in logarithmic and stationary growth phases.

Culex quinquefasciatus and Culex tritaeniorhynchus cells were grown in spinner culture and harvested in logarithmic and stationary phases of growth. The phospholipids were extracted from the cells, and the fatty acid profiles of the phospholipid classes were determined and compared. The major components were phosphatidylcholine and phosphatidylethanolamine, constituting greater than or equal to 80% of the phospholipid. The fatty acid profiles of lysophosphatidylcholine, phosphatidylinositol, and cardiolipin showed changes with aging of the Culex cells and between the species. In the lysophosphatidylcholine fraction, there was an increase in saturation of the fatty acids of the C. quinquefasciatus cells, and chain lengthening occurred in both species from the logarithmic to stationary phases of growth. In the phosphatidylinositiol fraction, both Culex species showed a decrease in monoenes and an increase in polyenes, while only the C. tritaeniorhynchus cells showed an increase in fatty acid chain length with aging. The C. quinquefasciatus cells had an increase in polyenes with aging in the cardiolipin fraction. Differences in the percentage composition of the fatty acids were shown in all the phospholipid fractions between the Culex species in the logarithmic phase of growth and all except the phosphatidylinositiol and cardiolipin fractions in the stationary phase.

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PubMed2002

Host-feeding habits of Culex and other mosquitoes (Diptera: Culicidae) in the Borough of Queens in New York City, with characters and techniques for identification of Culex mosquitoes.

The host-feeding patterns of mosquitoes (n = 247) collected in the Borough of Queens in New York City in July and August 2000 were investigated using an indirect ELISA and a polymerase chain reaction (PCR)-heteroduplex assay. Culex pipiens L. and Cx. restuans Theobald fed primarily on birds, and their feeding habits support their implication as enzootic vectors of West Nile virus. Culex salinarius Coquillett and Coquillettidia perturbans (Walker) fed mainly on mammals, with fewer blood meals taken from birds, and these two species are potential bridge vectors of West Nile virus. Culex mosquitoes took blood meals (n = 54) from 11 different avian species. Only the northern cardinal (Cardinalis cardinalis), American robin (Turdus migratorius), and Brown-headed cow bird (MolIothrus ater) were fed upon by all three Culex species. Multiple blood feedings on avian hosts were detected in Cx. pipiens and Cx. restuans. Species identifications of Culex mosquitoes made using morphological characteristics were confirmed with a PCR assay that employed species-specific primers. All Cx. pipiens (n = 20) and Cx. salinarius (n = 10) specimens were correctly identified, but three (20%) of 15 Cx. restuans were misidentified as Cx. pipiens.

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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.

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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.

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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.

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