Replication of dengue type 2 virus in Culex quinquefasciatus (Diptera: Culicidae)

We were able to infect Culex quinquefasciatus by the parenteral route with dengue virus type 2. The percentage of mosquitoes infected was dose dependent and we obtained a rate of 45.6% infected Cx. quinquefasciatus when a 10(5.9) MID50 (mosquito infectious dose for 50% of the individuals as measured in Aedes aegypti) of dengue virus type 2 per mosquito was used. Infection was detected by an immunofluorescent assay performed on mosquito head squashes 14 days after infection. The replication of dengue virus in Cx. quinquefasciatus was either at a very low level of magnitude or generated a large number of noninfectious particles since the triturated bodies of infected Cx. quinquefasciatus did not infect Ae. aegypti mosquitoes when inoculated parenterally. We were unable to infect Cx. quinquefasciatus females orally with an artificial meal that infected 100% of Ae. aegypti females. These findings lead us to agree with the consensus that Cx. quinquefasciatus should not be considered a biological vector of dengue viruses.     

Vector competence of five common mosquito species in the People's Republic of China for Western equine encephalitis virus

Two strains of the Western equine encephalitis virus (WEEV) were first detected and isolated in China in 2001. The maintenance and transmission cycles of WEEV in China are currently not well understood, and the mosquito vectors involved in these cycles are unknown. To understand the ability of the local mosquitoes in China to transmit WEEV, the vector competence of five mosquito species, namely, Culex pipiens pallens Coquillett, Cx. p. quinquefasciatus Say, Aedes (Stegomyia) albopictus Skuse, Ae. (Stegomyia) aegypti Linnaeus, and C. tritaeniorhynchus Giles, for WEEV were evaluated. Infection rates for Cx. p. pallens, Cx. p. quinquefasciatus, Cx. tritaeniorhynchus, Ae. Albopictus, and Ae. aegypti were 46%, 60%, 80%, 37%, and 25%, respectively. Dissemination rates for the same species were 60%, 61%, 75%, 55%, and 50%, respectively. Transmission rates were 41%, 53%, 57%, and 45% for Cx. p. pallens, Cx. p. quinquefasciatus, Ae. Albopictus, and Ae. Aegypti, respectively. Infection rates were significantly different between species, but the difference between dissemination and transmission rates were nonsignificant. These results suggest that several local mosquito species in China are competent laboratory vectors for WEEV.     

A comparision of West Nile Virus transmission by Ochlerotatus trivittatus (COQ.), Culex pipiens (L.), and Aedes albopictus (Skuse)

Transmission of West Nile virus (WNV) by Ochlerotatus trivittatus, Culex pipiens, and Aedes albopictus were compared 14 days after taking blood meals from viremic chickens with titers ranging from 10(2.5) to 10(9.5) cell infective dose (50)s (CID50s)/mL serum. Transmission occurred in one of four (25%) Oc. trivittatus and one of 25 (4%) Cx. pipiens that fed on chickens with titers of 10(5.5) CID50s/mL. No transmission occurred among two of 16 (13%) Oc. trivittatus or one of 25 (4%) Cx. pipiens that became infected after blood meals with titers of 10(5.0) and 10(4.5) CID50s/mL, the next lowest blood meal titers evaluated. Seventeen of 28 (61%) Ae. albopictus transmitted WNV after blood meals with titers of 10(7.0) CID50s/mL, but no infection or transmission was observed among 21 Ae. albopictus that fed on chickens with titers of 10(5.0) CID50s/mL, the next lowest titer evaluated. Transmission by all three species increased dramatically after blood meals with WNV titers of > or = 10(5.5) CID50s/mL. No significant differences occurred in dissemination and transmission rates of the three species after taking blood meals with titers of > 10(7.0) CID50s/mL. The cumulative mean +/- SE transmission rates of Oc. trivittatus, Cx. pipiens, and Ae. albopictus after blood meals with titers of > or = 10(7.0) CID50s/mL were 45.5 +/- 4.1%, 46.8 +/- 4.5%, and 72.4 +/- 5.5%. The cumulative mean dissemination rates of the three species were 78.3 +/- 6.7%, 74.8 +/- 2.6%, and 88.6 +/- 2.1%. The rates of transmission by the three species that developed disseminated infections after blood meals with titers of > or = 10(7.0) CID50s/mL were 58.8 +/- 4.4%, 62.6 +/- 5.8%, and 81.6 +/- 5.4%, respectively. In a previous study, we found that susceptibility of the three species to WNV was essentially the same when fed on chickens with WNV titers of > 10(7.0) CID50s/mL, but Oc. trivittatus and Cx. pipiens were more susceptible than Ae. albopictus to WNV at lower virus titers. The current study strongly suggests that Ae. albopictus is a more efficient vector than Oc. trivittatus and Cx. pipiens when fed blood meals with titers of > 10(7.0) CID50s/mL. However, Oc. trivittatus and Cx. pipiens might be more efficient as vectors when infected by blood meals with titers of < 10(7.0) CID50s/mL.     

Size alters susceptibility of vectors to dengue virus infection and dissemination

The size of arthropod vectors may affect their ability to transmit pathogens. Here we test the hypothesis that body size alters the susceptibility of Aedes aegypti and Aedes albopictus mosquitoes to dengue virus (DENV) infection and subsequent dissemination throughout the body of the mosquito. After feeding on blood containing known quantities of virus, smaller-sized females were significantly more likely to become infected and to disseminate virus than larger individuals. The effects of size were stronger for Ae. aegypti and independent of rearing conditions. Ae. albopictus was more susceptible to DENV infection and had higher virus titer in the body than Ae. aegypti, yet infected Ae. aegypti disseminated DENV more readily than infected Ae. albopictus. These results are consistent with the concept that Ae. aegypti is a more competent vector of DENV and emphasize the importance of body size in determining adult infection parameters.     

Susceptibility of Ochlerotatus trivittatus (Coq.), Aedes albopictus (Skuse), and Culex pipiens (L.) to West Nile virus infection

The susceptibility of Ochlerotatus trivittatus (Coq.) to West Nile virus (WNV) was assessed by comparing it to the susceptibility of Aedes albopictus (Skuse), a likely bridge vector, and Culex pipiens (L.), a primary WNV amplifying species. The three species were infected with WNV (NY crow-1999) by feeding on 2-3-day-old chickens with serum virus titers ranging from 10(2.5) to 10(9.5) cell culture infective dose (CID) 50s/mL. The lowest infective titer for Oc. trivittatus and Cx. pipiens was 10(4.5) CID50s/mL. Thirteen percent (4/32) and 2% (1/45) of each species became infected postprandially. Infection rates of the two species increased to 43% (6/14) and 15% (6/40) after blood meals with a titer of 10(5.5) CID50s/mL. In contrast no infection was observed in nine Ae. albopictus that fed among three chickens with titers of 10(4.5) CID50s/mL nor in 41 Ae. albopictus that fed among three chickens with titers of 10(5.0) CID50s/mL. The infective dose 50s for Oc. trivittatus, Cx. pipiens and Ae. albopictus were 10(6.0), 10(6.2), and 10(6.6) CID50s/mL, respectively. Collectively these observations suggest that Oc. trivittatus and Cx. pipiens are more susceptible than Ae. albopictus to WNV when they feed on hosts with WNV titers of <10(7.5) CID50s/mL, but nearly as susceptible with blood meal titers of > or =10(7.5) CID50s/mL. Unpublished studies in our laboratory showed that cottontail rabbits fed on by WNV-infected Oc. trivittatus developed viremias as high as 10(5.5) CID50s/mL serum which exceeds 10 (4.2 (3.4-4.6)) CID50s/mL, the predicted ID10+/-95% CI of Oc. trivittatus. Consequently this mosquito, which also feeds on humans and birds has the potential to serve as a bridge vector and as a maintenance vector among mammals.     

Potential vectors of Rift Valley fever virus in the Mediterranean region

We evaluated the ability of three mosquito species (Aedes caspius, Aedes detritus, Culex pipiens), collected in southern France and Tunisia, and of different laboratory-established colonies (Aedes aegypti, Aedes albopictus, Aedes vexans, Anopheles gambiae, Culex pipiens, Culex quinquefasciatus) to disseminate two strains of Rift Valley fever virus (RVFV), the virulent ZH548 and the avirulent Clone 13. After feeding on an infectious blood meal at 10(8.5) plaque-forming units/mL, females were maintained at 30 degrees C for 14 days. Surviving females were tested for the presence of virus on head squashes. Disseminated infection rate corresponds to the number of females with disseminated infection among surviving females. Among field-collected mosquitoes, Cx. pipiens was the most susceptible species with disseminated infection rates ranging from 3.9% to 9.1% for French strains and up to 14.7% for Tunisian strains. Among laboratory-established colonies, Ae. aegypti from Tahiti exhibited the highest disseminated infection rates: 90% when infected with ZH548 and 72.6% with Clone 13. The presence of competent Cx. pipiens in southern France and Tunisia indicates the potential for RVFV epizootics to occur if the virus was introduced into countries of the Mediterranean basin.     

Control of mosquito vectors of tropical infectious diseases: (1) bioefficacy of mosquito coils containing several pyrethroids and a synergist

The bioefficacy of mosquito coils containing several pyrethroids were tested in a 25 m3 room against Culex pipiens quinquefasciatus, Aedes aegypti and Anopheles dirus. The test results were compared with tests against Culex pipiens pallens in Japan. Based on the KT50 values (the 50% knockdown time) of mosquito coils containing dl, d-T80-allethrin, d, d-T-prallethrin and methoxymethyl-tetrafluorobenzyl tetramethyl-cyclopropanecarboxylate (K-3050) at doses of 0.05-0.5% (w/w) with or without a synergist, the pyrethroid susceptibility of the four mosquito species was as follows: Cx. p. quinquefasciatus was several times more tolerant to pyrethroids than Cx. p. pallens, Ae. aegypti was a further several times more tolerant than Cx. p. quinquefasciatus, and An. dirus was more susceptible than Cx. p. pallens (KT50 value: about half of Cx. p. pallens). The order of their susceptibilities is common for pyrethroids. Mosquito coils containing d, d-T-prallethrin and K-3050 at doses of 0.05-0.2% (w/w) and N-(2-ethylhexyl)bicycle-[2,2,1]-hept-5-ene-2,3-dicarboxyimide as a synergist at a ratio of 2 times the active ingredient were highly effective against Ae. aegypti, the most important mosquito vector for dengue fever.     

Vector competence of Aedes aegypti (L.) and Culex quinquefasciatus (Say) for Dirofilaria immitis (Leidy)

This study was performed to examine the vector competence of Aedes aegypti and Culex quinquefasciatus for Dirofilaria immitis. Eleven individual experiments were conducted in this study. Nonthaburi and Udon Thani strains of Ae. aegypti were allowed to feed on infected dogs that had 5,750 and 4,600 microfilariae (mW) per ml of blood, respectively. Three groups of Bangkok-strain Cx. quinquefasciatus were allowed to feed on dogs that had 4,800, 5,200, and 5,850 mf per ml of blood. Six groups of Liverpool-strain Ae. aegypti were allowed to feed on dogs with 1,650, 1,950, 3,350, 9,000, 9,250, and 11,550 mf per ml of blood. Three to 4% of Nonthaburi-strain, and 0-6% of Udon Thani-strain Ae. aegypti became infected and had infective-stage larvae (L3) of D. immitis in their probosces. Zero to 1 and 7% of Bangkok-strain Cx. quinquefasciatus had L3 in their probosces after taking blood meals with 4,800 and 5,850 mf per ml of blood, respectively. The percent-infected Liverpool-strain Ae. aegypti with L3 in their probosces were 3-12, 0-12, 10, 16, 7-19, and 0-21 after taking blood meals with 1,650, 1,950, 3,350, 9,000, 9,250, and 11,550 mf per ml of blood, respectively, when tested at different post-blood-feeding days. This study showed both Ae. aegypti and Cx. quinquefasciatus from Thailand can become vectors for D. immitis; however, Liverpool-strain Ae. aegypti are more likely to be competent vectors for D. immitis than Ae. aegypti and Cx. quinquefasciatus from Thailand. The percent infection rates of Ae. aegypti and Cx. quinquefasciatus with D. immitis in the field in Thailand need to be investigated, to confirm the role of these mosquitoes in the life cycle of D. immitis in nature.     

Geographic variation in vector competence for West Nile virus in the Culex pipiens (Diptera: Culicidae) complex in California

We evaluated the susceptibility to infection and transmission of West Nile virus (WNV) in seven populations of Culex pipiens pipiens (L.), Cx. p. quinquefasciatus Say, and from populations containing Cx. pipiens/quinquefasciatus hybrids in a north-south transect of California. Samples were identified to species or as hybrid forms based on morphology of male terminalia. After 7 and 14 days of extrinsic incubation, few females were infected and none transmitted WNV from samples of Cx. p. pipiens from northern Shasta County and of Cx. p. quinquefasciatus from southern Los Angeles County. Seven days after infective feeding, 13%-36% of mosquitoes from the counties of Merced, Fresno, Kern, and San Bernardino were infected, and 12%-40% of infected mosquitoes expressed WNV in salivary expectorate. Fourteen days after infective feeding, 18%-43% of mosquitoes from these counties were infected, and 50%-69% of infected mosquitoes transmitted WNV in salivary expectorate. A sample of Cx. p. quinquefasciatus from Riverside County did not transmit WNV after 7 days, but 71% transmitted 14 days after infective feeding. These results reveal extensive geographic variation in vector competence for WNV in the Culex pipiens complex in California.     

Nonviremic transmission of West Nile virus: evaluation of the effects of space, time, and mosquito species

To evaluate the potential for nonviremic transmission (NVT) of West Nile virus (WNV) to occur in nature, we examined the effect of increasing spatial and temporal separation between co-feeding mosquitoes on the efficiency of nonviremic transmission and the potential of a West Nile virus bridge vector species, Aedes albopictus, to be infected via nonviremic transmission. West Nile virus-infected (donor) Culex pipiens quinquefasciatus were allowed to feed on a mouse for 5 minutes followed by non-infected (recipient) mosquitoes with increasing spatial (0, 10, 20, 30, 40, or 50 mm) or temporal (0, 15, 30, 45, or 60 min) separation from the site or time of donor feeding, respectively. Recipients became infected when feeding up to 40 mm from the donor and up to 45 minutes after donor feeding. Additionally, nonviremic transmission of West Nile virus from Cx. p. quinquefasciatus to Ae. albopictus was observed.     

A mosquito densovirus infecting Aedes aegypti and Aedes albopictus from Thailand.

A previously undescribed mosquito densovirus was detected in colonies of Aedes aegypti and Ae. albopictus from Thailand, using a polymerase chain reaction (PCR)-based assay. Phylogenetic analysis of this virus showed it to be most closely related to ADNV isolated from Russian Ae. aegypti. Both Aedes species were susceptible to oral infection with the Thai-strain virus. Larval mortality for Ae. albopictus was higher (82%) than for Ae. aegypti (51%). Aedes aegypti were able to transmit the virus vertically to a high (58%) proportion of G1 progeny, and the virus was maintained persistently for up to six generations. A PCR survey of adult Ae. aegypti and Ae. albopictus in Thailand indicated that only Ae. aegypti are infected in the field, with an overall prevalence of 44%. Densovirus infection in adult Ae. aegypti showed distinct seasonal variation. The Thai strain densovirus may play a role in structuring Ae. albopictus and Ae. aegypti populations in nature.     

Impact of extrinsic incubation temperature and virus exposure on vector competence of Culex pipiens quinquefasciatus Say (Diptera: Culicidae) for West Nile virus

Culex pipiens quinquefasciatus Say mosquitoes from a laboratory colony were exposed to artificial blood meals containing West Nile virus (WNV) and held at incubation temperatures approximating average daily temperatures that occur during Florida arboviral periods. Mosquitoes fed blood meals containing 6.2 logs plaque-forming units (pfu) WNV/mL and held at 25 degrees C, 28 degrees C, or 30 degrees C for 13 days exhibited significantly different rates of infection (30%, 52%, 93%) and dissemination (33%, 22%, 81%) across temperatures. In a separate experiment, Cx. p. quinquefasciatus mosquitoes were provided artificial blood meals with graded doses of WNV from 3.7 to 5.8 logs pfu/mL and maintained at 28 degrees C for 13 days. Rates of infection increased as a function of virus dose, but neither body titers nor dissemination rates were significantly different for mosquitoes that were infected by ingesting different amounts of WNV. Our findings indicate that efficiency of WNV infection and dissemination, and thereby transmission, in Cx. p. quinquefasciatus populations similar to our tested colony may also be diminished when fed blood meals containing less than 5.8 logs pfu WNV/mL and when environmental temperature falls below 30 degrees C. The relationship between the infection rate and dissemination rate changed at different temperatures. This relationship is likely complex and dependent on diverse interactions between factors such as incubation temperature and viremia, which should also be assessed for field populations.     

Infection of adult Aedes aegypti and Ae. albopictus mosquitoes with the entomopathogenic fungus Metarhizium anisopliae

This study describes a laboratory investigation on the use of the insect-pathogenic fungus Metarhizium anisopliae against adult Aedes aegypti and Ae. albopictus mosquitoes. At a dosage of 1.6 x 10(10)conidia/m(2), applied on material that served as a mosquito resting site, an average of 87.1+/-2.65% of Ae. aegypti and 89.3+/-2.2% of Ae. albopictus became infected with the fungus. The life span of fungus-contaminated mosquitoes of both species was significantly reduced compared to uninfected mosquitoes. LT(50)-values of fungus-contaminated mosquitoes ranged between 3.1+/-0.2 days (male Ae. aegypti) and 4.1+/-0.3 days (female Ae. aegypti). LT(50)-values of uncontaminated mosquitoes ranged from 17.7+/-0.4 days (female Ae. albopictus) to 19.7+/-0.6 days (male Ae. albopictus). These results indicate that both mosquito species are highly susceptible to infection with this entomopathogen. Requirements for developing and incorporating this biological control method into current strategies to control major diseases vectored by these species, such as dengue fever, are discussed.     

Insecticide susceptibility tests of Anopheles minimus s.l., Aedes aegypti,Aedes albopictus,and Culex quinquefasciatus in northern Thailand

The susceptibility of Anopheles minimus s.l., Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus to insecticide in northern Thailand was monitored by using the WHO standard susceptibility test. One- to two-day old female mosquitos, which were reared from wild caught females or immature stages, were exposed to discriminating dosages of insecticides for recommended exposure periods, and the 24-hour mortality recorded. The results revealed that, in general, An. minimus s.l. was still susceptible to DDT and permethrin, except in some areas where a slight increase in tolerance to DDT was observed. Ae. aegypti and Ae. albopictus were both highly resistant to DDT, but in some areas the former was also resistant to permethrin and deltamethrin. Cx. quinquefasciatus was resistant to DDT and etofenprox, with a slight increase in tolerance to permethrin, deltamethrin, malathion and fenitrothion. No resistance to lambda-cyhalothrin was detected in any of the species studied.     

Growth characteristics of ChimeriVax-DEN2 vaccine virus in Aedes aegypti and Aedes albopictus mosquitoes

The chimeric yellow fever (YF) 17D-dengue type 2 (ChimeriVax-DEN2) vaccine virus developed by Acambis, Inc. (Cambridge, MA) contains the prM and E genes of wild-type (wt) dengue 2 (DEN-2) (strain PUO-218) virus in the YF vaccine virus (strain 17D) backbone. The potential of ChimeriVax-DEN2 virus to infect and be transmitted by Aedes aegypti, the principal DEN and YF virus mosquito vector, and Aedes albopictus, a species that occurs in areas of active transmission of YF and DEN viruses, was evaluated. Mosquitoes were intrathoracically (IT) inoculated with virus or were fed a virus-laden blood meal, and the replication kinetics of ChimeriVax-DEN2 were compared with the wt DEN-2 and YF 17D vaccine viruses. Replication of YF 17D virus is attenuated in cultured Ae. albopictus C6/36 mosquito cells and in Ae. aegypti and Ae. albopictus mosquitoes. Growth of ChimeriVax-DEN2 virus similarly was restricted in C6/36 cells and in mosquitoes. ChimeriVax-DEN2 replicated in 56% of IT inoculated Ae. aegypti, and virus disseminated to head tissue in 36%, with a mean viral titer of 1.8 log10 PFU/mosquito. Of mosquitoes, 16% of Ae. aegypti and 24% of Ae. albopictus were infected 14 days after a blood meal containing ChimeriVax-DEN2, but virus did not disseminate to head tissue. In contrast, DEN-2 replicated in all IT inoculated and orally infected Ae. aegypti (mean titer 5.5 log10 PFU/mosquito), and virus disseminated to head tissue in 95%. Of Ae. albopictus, 84% were infected after a blood meal containing DEN-2 virus; dissemination occurred in 36%. Replication of ChimeriVax-DEN2 virus in mosquitoes corresponded to that of YF 17D vaccine virus, which is restricted in its ability to infect and replicate in mosquitoes. Therefore, transmission of ChimeriVax-DEN2 virus by vector mosquitoes is unlikely.     

Susceptibility of Florida mosquitoes to infection with chikungunya virus

Chikungunya virus (CHIKV) has caused recent, large epidemics on islands in the Indian Ocean, raising the possibility of more widespread CHIKV epidemics. Historically, CHIKV has been vectored by Aedes aegypti, but these outbreaks likely also involved Ae. albopictus. To examine the potential for an outbreak of CHIKV in Florida, we determined the susceptibility to CHIKV of F1 Ae. aegypti and Ae. albopictus from Florida. In addition, we also evaluated two well-characterized laboratory strains (Rockefeller and Lake Charles) of these species. We determined infection and dissemination rates as well as total body titer of mosquitoes 7 days post-exposure (pe) (Ae. albopictus) and 3, 7, and 10 days pe (Ae. aegypti). All mosquito strains were susceptible to both infection and dissemination, with some variation between strains. Our results suggest Florida would be vulnerable to transmission of CHIKV in urban and rural areas where the two vector species occur.     

Introduction of Aedes albopictus in Gabon: what consequences for dengue and chikungunya transmission?

The 2007 outbreak of chikungunya in Gabon has indicated the potential of this disease to spread beyond its usual range ensuing from the expansion of the mosquito Aedes albopictus . A few cases of dengue (DEN) infection were also detected. Because little is known about the potential for Gabonese mosquito species to transmit both chikungunya and DEN viruses (DENV), we conducted studies to determine the susceptibility of Ae. albopictus and Aedes aegypti collected in Libreville to both viruses by experimental infections. Disseminated infection rates were high for Ae. albopictus infected with chikungunya virus (CHIKV) (66.7–86%) and low with DENV (13–21.4%). Moreover, Ae. aegypti sp. formosus was a less efficient vector of CHIKV than Ae. albopictus . The recent introduction and dissemination of chikungunya associated with the invasion of Ae. albopictus in Africa illustrates the potential for CHIKV to spread to other parts of the world.     

Infectious clones of Chikungunya virus (La Réunion isolate) for vector competence studies

The recent outbreak of Chikungunya virus (CHIKV) on several islands in the Indian Ocean and in India has focused attention on this reemerging virus and highlighted the need for development of new tools to study vector-virus-host interactions. We have constructed and characterized, in cell culture, Aedes aegypti and Ae. albopictus mosquitoes, infectious cDNA clones of CHIKV using a recent isolate from La Réunion Island. Comparison of the growth kinetics and infection rates of the viral isolate CHIKV strain LR2006 OPY1 (CHIKV-LR) and a full-length infectious clone (CHIKV-LR ic) indicate that the infectious clone has retained the viral phenotypes of the original isolate. Infectious clones that express green fluorescent protein (GFP) were also produced and characterized in cell culture and in Aedes mosquitoes. The CHIKV-LR 5'GFP infected Ae. aegypti and Ae. albopictus mosquitoes at a similar rate to the original virus and to the full length infectious clone. The CHIKV-LR 3'GFP only infected Ae. albopictus mosquitoes at similar rates. The development of these authentic infectious clones will enable targeted studies of the molecular determinants of infection, pathogenesis and transmission competence by Ae. aegypti and Ae. albopictus mosquitoes.     

Evaluation of cyfluthrin and fenfluthrin for their insecticidal activity against three vector mosquitoes

The EC50/EC90 concentrations of cyfluthrin and fenfluthrin were tested for their activity against different developmental stages of three important vector mosquitoes viz., Anopheles stephensi Liston, Aedes aegypti (Linn.) and Culex quinquefasciatus Say. The EC90 concentrations of both cyfluthrin and fenfluthrin showed ovicidal effect on An. Stephensi and Ae. aegypti whereas EC90 of cyfluthrin checked the hatching of eggs completely in Cx. quinquefasciatus. Fenfluthrin at EC50 concentration reduced the percentage of hatching significantly (p < 0.05) only in An. stephensi. Both the compounds were more active against the fourth larval instars of all mosquito species and cyfluthrin in culicines (17.3% Ae. aegypti = 9.1%) and fenfluthrin in anophenlines (An. stephensi = 36.8%) brought about maximum inhibition in adult emergence. Various types/degrees of morphogenetic aberrations were induced in all mosquito species on treatment with these compounds. Cyfluthrin treated female mosquitoes showed reduced fecundity rates in An. stephensi (p < 0.05), Cx. quinquefasciatus (p < 0.001) and fenfluthrin treated in An. stephensi (p < 0.5) and Ae. aegypti (p < 0.05). The fertility rates of all the mosquito species were significantly reduced (p < 0.001) by both the compounds.