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PubMed2004

Field evaluation of CDC gravid trap attractants to primary West Nile virus vectors, Culex mosquitoes in New York State.

A field study was conducted to evaluate two CDC gravid trap attractants available for the West Nile virus surveillance program in New York State (NYS). According to potential attractiveness, a common lawn sod in NYS, Kentucky bluegrass (Poa pratensis) infusion and a rabbit chow infusion were compared for attractiveness to primary West Nile virus vectors, Culex mosquitoes. Attractiveness of each infusion was measured by the number of adult mosquitoes caught in CDC gravid traps and the number of egg rafts laid in ovitraps. Both gravid trap and ovitrap studies demonstrated that lawn sod infusion with a 7-day incubation period had better attractiveness to Culex restuans/Culex pipiens than rabbit chow infusion with the same incubation period. Attractiveness of lawn sod infusions was increased as they became aged within a week's period. Lawn sod infusion also attracted more Ochlerotatus japonicus, a potentially important West Nile virus vector in New York.

Animals↗
PubMed2004

Methods for studying the vector competence of Culex tarsalis for western equine encephalomyelitis virus.

Female Culex tarsalis fed heparinized chicken blood-western equine encephalomyelitis virus (WEEV) mixtures through a biomembrane feeder were compared with females fed sweetened blood-virus mixtures presented in pledgets or as hanging drops or to restrained chickens with natural or artificial viremias. Results indicated that sodium heparin did not adversely affect the infection of Culex tarsalis with WEEV. Overall advantages of the biomembrane system included 1) increased blood feeding frequency, 2) control of the infectious virus dose, and 3) greater or similar infection rates and body titers to females taking blood meals from viremic chickens. Anesthetizing females with triethylamine for in vitro transmission assessment using the capillary tube method produced results similar to immobilization using cold or CO2 + cold. Our research provided insight into tools useful to investigate the infection and transmission of WEEV by Cx. tarsalis.

Animals↗
PubMed2004

[Genetic diversity of isoenzyme in Culex pipiens complex field populations sampling from distinct area of China].

Eight field populations of Culex pipiens complex collected from five provinces (Guangdong, Henan, Shandong, Beijing and Yunnan) in 2001 were used to study genetic diversity by starch gel electrophoresis. Data from seven loci (ME,MDH-1,MDH-2,MDH-3,GPD,EST-2,EST-3) of four isozymes were analyzed by software Biosys2.0 and FSTAT(Version 2.9.3). The results were as follows: (1) The values of He (from 0.098 to 0.41) indicated genetic variabilities of different degree in populations.(2)The low level of gene flow (Nm=0.64) could not prevent genetic drift to cause the gene differentiation between populations. The genetic diversity between populations attributed to the genetic diversity of total populations is small (Gst =0.303), and the great part is accumulated within populations (Hs/Dst=2). (3) The genetic structure of Culex pipiens complex population was the isolation-by-distance model. (4) The genetic identity (or genetic distance) revealed the scale of genetic differentiation between populations which related to the collection sites.

Alleles↗
PubMed2005

Short report: observations on the multiple feeding behavior of Culex tritaeniorhynchus (Diptera: culicidae), the vector of Japanese encephalitis in Kerala in southern India.

A study was undertaken in villages endemic for Japanese encephalitis (JE) in Kerala in southern India during the period 1998-2001 to determine the host-feeding pattern of Culex tritaeniorhynchus, the major vector of JE in southeast Asia. A total of 3,067 blood-engorged Cx. tritaeniorhynchus were tested and 2,553 (82.2%) of the samples could be identified. Culex tritaeniorhynchus had fed mainly (56.6%) on cattle. Pig feeding accounted 6.3% of the total samples. Some samples (n = 980, 38.3%) were of serologic mixed origin. Of 980 mixed blood-fed mosquitoes, 975 (99.5%) had imbibed blood from two distinct hosts and 5 (0.5%) imbibed blood from three distinct hosts. Mixed blood meals were mostly (96.7%) from cattle and goats. The epidemiologic implications of multiple feeding of Cx. tritaeniorhynchus on dampening (dead-end) hosts such as cattle and goats in the transmission of JE virus is discussed.

Animals↗
PubMedDate not supplied

[Determination of glutathione-S-transferase activity in Culex quinquefaciatus strains in Cuba and other Latin American countries].

In the present paper, we standardized a microtitration assay for the determination of specific activity of glutathione-S-transferase using a Culex quinquefasciatus strain selected in lab with pyrethroid insecticide lambdacyhalothrin for 6 generations (SP6). The saturation values for reduced glutathione and 1-chlorine 2,4-dinitrobenzene were 15 mM and 40 mM, respectively; we also estimated that 3 minutes was the optimal time in order to differentiate resistant strain SP6 from the susceptible reference strain S-Lab (p>0.05). Additionally, the optimized microtitration method allowed testing 4 Culex strains from Cuba (SANTIAGO DE CUBA, SD4, QUIBU AND SP6), one from Venezuela (MIRANDA), one from Colombia (MEDELLIN) and the other from Brazil (RIO DE JANEIRO) for glutathione-S-transferase activity. MIRANDA showed the highest activity for this detoxifying enzyme. However, the mechanism of detoxyfication in all the strains was very unfrequent, which indicates that its role in resistance to insecticide for all the studied strains is not so important. Glutathione-S-transferase values were compared with non-specific esterase and altered acetylcholinesterase frequencies for each of the studied strains.

Animals↗
PubMedDate not supplied

[Pathogenic effect of the parasite nematode Strelkovimermmis spiculatus (Nematoda Mermithidae) in larvae of mosquito Culex quinquesfasciatus (Diptera Culicidae) under laboratory conditions in Cuba].

The infective capacity of Strelkovimermis spiculatus Poinar and Camino, 1986, was evaluated under laboratory conditions for the first time in Cuba in order to introduce it as a new agent of biological control of mosquitoes of medical and epidemiological importance. The second stage larvae of Culex quinquefasciatus Say, 1823, were used and exposed to the infective juvenile parasites at different doses. It was observed a rise in the mean values of infestation and in the mortality percentage with the dose increase. Culex quinquefasciatus Say proved to be a good host and a dose of 7:1 will be optimum to attain high percentages of mortality and to obtain this parasite massively for its further evaluation under field conditions.

Animals↗
PubMed2004

Rotational application of bioinsecticide with deltamethrin-An antilarval measure for the control of filarial vector, Culex quinquefasciatus (Culicidae: Diptera).

A laboratory investigation was undertaken to study the cyclic usage of field recommended doses of Bacillus thuringiensis israelensis (Bti), Bacillus sphaericus (Bsp) and combination of Bti and Bsp (half the recommended dose of each) with deltamethrin 2.8 EC to attain better control of mosquito larvae. To understand the susceptibility status of the Culex quinquefasciatus larvae in the field, early fourth instar field collected larvae were exposed to the above treatments of biopesticides and were monitored for their persistency till 50% mortality was obtained. The larvae those survived in each treatment were transferred to the concentration of deltamethrin that gave 50% mortality. Observations on larval mortality after the treatment with deltamethrin were recorded after 24 h. The results revealed that Bti excels Bsp, as it recorded 54% mortality only on 17th day after application. The other salient finding of this study is LC50 of deltamethrin is sufficient to follow the biopesticides application for an effective control of Culex larvae.

Animals↗
PubMed2005

Susceptibility of Ochlerotatus taeniorhynchus and Culex nigripalpus for Eeverglades virus.

Everglades virus (EVEV), an alphavirus in the Venezuelan equine encephalitis (VEE) complex, is a mosquito-borne human pathogen endemic to South Florida. Field isolations of EVEV from Culex (Melanoconion) cedecei and laboratory susceptibility experiments established this species as its primary vector. However, isolates of EVEV from Ochlerotatus taeniorhynchus and Culex nigripalpus, more abundant and widespread species in South Florida, suggested that they also transmit EVEV and could infect many people. We performed susceptibility experiments with F(1) generation Oc. taeniorhynchus and Cx. nigripalpus to evaluate their permissiveness to EVEV infection. In contrast to the high degree of susceptibility of Cx. (Mel.) cedecei, Oc. taeniorhynchus and Cx. nigripalpus were relatively refractory to oral EVEV infection, indicating that they are probably not important vectors. Identification of vectors involved in enzootic EVEV transmission will assist in understanding potential changes in vector use that could accompany the emergence of epizootic or epidemic EVEV.

Alphavirus Infections↗
PubMed2005

[Study on the biological characteristics of permethrin-resistant and susceptible strains of Culex pipiens pallens].

OBJECTIVE: To compare the biological characteristics of Culex pipiens pallens between permethrin-resistant strain and the susceptible strain. METHODS: In laboratory, the biological characteristics about bloodsucking, reproduction and development of permethrin-resistant and susceptible strains were observed and recorded. Life table of the experimental populations was constituted. RESULTS: The bloodsucking rate of resistant strain was lower than susceptible strain and the difference was significant. The life-span of adults of resistant strain and the developmental duration of eggs, larvae and pupae were longer than susceptible strain and the difference was significant. The death rate of eggs of resistant strain was higher than that of susceptible strain and the difference was significant. The permethrin-resistant strain showed a fitness value of 0.58 relative to the susceptible strain. CONCLUSION: The permethrin resistance of Culex pipiens pallens may result in a disadvantage to its reproduction and development.

Animals↗
PubMed2004

Role of some factors on the breeding of JE vector Culex vishnui group.

Vector of JE, Culex vishnui group, prefer to breed in rice field. During the present study, roles of some factors like irrigation, manuring, pesticide application, rainfall, temperature and pH of the breeding water, depth of breeding water and height of paddy plants on breeding of Culex vishnui group larvae have been studied. It is evident from the study that besides striking role of the factors like manuring and pesticide application, other factors have also some role on the breeding of JE vectors at their breeding sites.

Agriculture↗
PubMed2005

Chemical detection of the predator Notonecta irrorata by ovipositing Culex mosquitoes.

We tested the oviposition response of Culex mosquitoes to the predator Notonecta irrorata in an outdoor artificial pool experiment employing equal numbers of control and predator pools. There was a strong oviposition avoidance by Culex of Notonecta pools; 83% of egg rafts were found in control pools during the period in which Notonecta were present. After removing Notonecta, mosquitoes continued to avoid ovipositing in the former Notonecta pools for two additional days suggesting a predator-released kairomone as the cue used by the mosquitoes to detect the presence of this predator.

Animals↗
PubMed1990

Evaluation of 1-octen-3-ol as an attractant for Coquillettidia perturbans, Mansonia spp. and Culex spp. associated with phosphate mining operations.

Field studies were conducted in phosphate mined areas of Polk County, FL, to determine the responses of mosquitoes produced as a result of mining operations to octenol and carbon dioxide. There was a highly significant response of all species except Culex erraticus and Anopheles quadrimaculatus to CO2. Also, a significant negative octenol response was shown for An. quadrimaculatus. Coquillettidia perturbans, Mansonia titillans and Cx. salinarius had an increased response to octenol relative to no attractant. There was a slightly negative interactive effect between octenol and 500 cc/min CO2 for Anopheles spp. and Culex (Melanoconion) spp. Both Cq. perturbans and Ma. titillans showed a significant synergistic enhancement in catch with octenol supplemented CO2 when compared with CO2 alone. However, their response to CO2 was not significantly different at 2 release rates (200 and 500 cc/min). There was a slightly greater than additive effect for the combination of octenol and CO2 for Cx. nigripalpus.

Animals↗
PubMed1990

Mosquitoes of the genus Culex in the Suez Canal Governorates.

Mosquitoes are among the most annoying and important vectors of human and animal diseases as malaria, filariasis, yellow fever, rift valley fever...etc. In this paper, it was aimed to study the present status of species of genus Culex in the Suez Canal Governorates after the reconstruction and developmental projects. Five species of Culex were identified: C. pipiens, C. univittatus, C. antennatus, C. poicilipes and C. pusillus. The latter species was represented by two specimens. C. pipiens was the commonest species both indoors and outdoors. C. antennatus and C. poicilipes were found only outdoors. C. pipiens was found all the year round particularly in Spring. Other species were found in Spring and Autumn, except C. antennatus which was found in Summer as well. The results were discussed on the light of work done before.

Animals↗
PubMed1989

Simplified staining in situ of neurosecretory cells of the supraoesophageal ganglion of the female Culex pipiens molestus (Forskal) (Diptera: Culicidae).

The author describes the morphology and distribution of the neurosecretory cells in the supraoesophageal ganglion of the adult female Culex pipiens molestus, using paraldehyde fuchsin and paraldehyde thionine-paraldehyde fuchsin as vital staining techniques. The brain of Culex pipiens molestus has three regions (the proto-, deuto- and tritocerebrum) in which principally two types of neurosecretory cells (A and B) can be detected. Both A (dark) and B (light) cells are to be found in the protocerebrum, where they are termed medial neurosecretory cells, as they are distributed in the pars intercerebralis and only a few occur more laterally. A small group of type A and B neurosecretory cells is to be found in the posterior part of the brain (the tritocerebrum). These cells display characteristics differences in their tinctorial affinity.

Animals↗
PubMed1989

Insect growth regulators: I. Biological activity of some IGR's against the susceptible and resistant strains of Culex pipiens larvae. II. Pattern of cross resistance to IGR's in carbaryl-resistant strain.

The biological activity and cross-resistance of some IGR's, Dimilin, BAY SIR 8514 and Chlorofluzuron against susceptible and carbaryl-resistant strains of Culex pipiens were determined. The results indicated that these compounds are highly effective against the larvae of C. pipiens but more potent larvicides against the susceptible larvae than against the resistant ones. The pattern of cross-resistance to the used IGR's in the carbaryl-resistant strain were obtained. The data revealed no three IGR's as larvicides against the susceptible and resistant Culex pipiens. The pattern of cross resistance to other potent IGR's was also studies.

Animals↗
PubMedDate not supplied

[Sensitivity to dimilin (diflubenzuron) in a strain of Aedes (S) aegypti Linnneaus, 1762 and of Culex (C) quinquefasciatus Say, 1823 bred in the laboratory].

This paper studies the degree of sensitivity of larval Aedes (S) aegypti Linneaus, 1762 and Culex quinquefasciatus, Say, 1823, to dimilin (diflubenzuron-urea) with strains from Güines, in Havana province, which were bred in the laboratory. Tests were carried out in the period ranging from March, 1982 to March, 1983. The method used was the one standardized by the World Health Organization in 1980. The authors found susceptibility of A. aegypti to the product used with values of CL50 and CL95 of 0.045 mg/L and 0.255 mg/L respectively as well as physiologic resistance in Culex quinquefasciatus.

Aedes↗
PubMed1989

[Study on inhibiting effect of 14 insecticides on esterase of Culex tritaeniorhynchus from five geographic populations].

Isoelectrofocusing technique was used to study the inhibiting effect of 14 insecticides on esterase isozymes of Culex tritaeniorhynchus from natural populations in Fuzhou, Shanghai, Qingdao, Dalian and Beijing areas. Among 14 insecticides, organophosphates were good inhibitors to all esterase isozymes, but Allethrin, Propoxur, DDT, Dieldrin had no or almost no inhibiting effect on esterase. 26 esterase isozyme bands of Culex tritaeniorhynchus were revealed by isoelectrofocusing.

Animals↗
PubMed1987

Exsheathment of microfilariae of Brugia pahangi in Anopheles quadrimaculatus and Culex quinquefasciatus.

In order to determine whether the exsheathment patterns described in our previous study occurred in other microfilaria-mosquito systems, exsheathment of microfilariae of Brugia pahangi was studied in two species of mosquitoes. The results of the quantitative observation revealed that the microfilariae of Brugia pahangi tend to carry their sheaths into the haemocoel of Anopheles quadrimaculatus and Culex quinquefasciatus within 4 hr after infected blood meals. The percentage of the sheathed microfilariae in the haemocoel progressively decreased to 0% at 24 hr post-ingestion. Microfilariae remaining in the midgut of both species of mosquitoes were recorded most frequently casting off their sheaths in the midgut 2 hr post-ingestion. The percentage of microfilariae exsheathed in the midgut progressively increased to about 100% and 40% 24 hr post-ingestion in Anopheles quadrimaculatus and Culex quinquefasciatus respectively. These results confirm that exsheathment of microfilariae of Brugia pahangi occurs both in the haemocoel and in the midgut of two species of mosquitoes.

Animals↗