Showing papers in "Journal of The American Mosquito Control Association in 1999"

Activity and biological effects of neem products against arthropods of medical and veterinary importance

Abstract: Botanical insecticides are relatively safe and degradable, and are readily available sources of biopesticides The most prominent phytochemical pesticides in recent years are those derived from neem trees, which have been studied extensively in the fields of entomology and phytochemistry, and have uses for medicinal and cosmetic purposes The neem products have been obtained from several species of neem trees in the family Meliaceae Six species in this family have been the subject of botanical pesticide research They are Azadirachta indica A Juss, Azadirachta excelsa Jack, Azadirachta siamens Valeton, Melia azedarach L, Melia toosendan Sieb and Zucc, and Melia volkensii Gurke The Meliaceae, especially A indica (Indian neem tree), contains at least 35 biologically active principles Azadirachtin is the predominant insecticidal active ingredient in the seed, leaves, and other parts of the neem tree Azadirachtin and other compounds in neem products exhibit various modes of action against insects such as antifeedancy, growth regulation, fecundity suppression and sterilization, oviposition repellency or attractancy, changes in biological fitness, and blocking development of vector-borne pathogens Some of these bioactivity parameters of neem products have been investigated at least in some species of insects of medical and veterinary importance, such as mosquitoes, flies, triatomines, cockroaches, fleas, lice, and others Here we review, synthesize, and analyze published information on the activity, modes of action, and other biological effects of neem products against arthropods of medical and veterinary importance The amount of information on the activity, use, and application of neem products for the control of disease vectors and human and animal pests is limited Additional research is needed to determine the potential usefulness of neem products in vector control programs

Aedes (Finlaya) japonicus japonicus (Theobald), a new introduction into the United States.

Abstract: Aedes (Finlaya) japonicus japonicus is recorded for the 1st time in the United States Four adult females were collected in light traps at 2 sites in New York and one site in New Jersey during the months of August and September 1998 Notes on bionomics are provided Illustrations of the adult female, male, and larva are included

Pyrethroid cross resistance spectrum among populations of Anopheles gambiae s.s. from Côte d'Ivoire.

Abstract: Field samples of Anopheles gambiae s.s. from Cote d'Ivoire were tested with 5 pyrethroids (cyfluthrin, lambda-cyhalothrin, alpha-cypermethrin, deltamethrin, permethrin), 1 pseudo-pyrethroid (etofenprox), and an organochlorine (DDT). With the use of World Health Organization diagnostic tests, 5 out of 6 samples were found cross-resistant to these insecticides. A strong decrease in knockdown effect and mortality was also observed when testing deltamethrin-impregnated nettings. With a polymerase chain reaction amplification of specific alleles diagnostic test, resistance was found associated with the presence of a kdr mutation. The strong correlation between kdr allelic frequency and resistance to DDT or etofenprox indicated that kdr was the main resistance factor for these 2 insecticides. On the contrary, a lower correlation was observed between kdr frequency and resistance to 4 of the 5 pyrethroids tested, suggesting that another mechanism was also involved, likely a metabolic detoxification. These results point out the necessity to monitor pyrethroid resistance and the presence of kdr before implementation of any impregnated bed-net programs for malaria control.

Aedes albopictus in the United States: current status and prospects for further spread.

Abstract: Since its initial discovery in the continental USA in 1985, the Asian tiger mosquito, Aedes albopictus, has spread rapidly throughout the eastern part of the country. Infestations of Ae. albopictus now have been reported to the Centers for Disease Control and Prevention from 919 counties in 26 states in the continental USA. This species is believed to be established in 911 counties in 25 states. Single individuals or small numbers of Ae. albopictus have been intercepted and destroyed in 3 additional states (California, New Mexico, and Washington). Five states (Florida, Georgia, North Carolina, South Carolina, and Tennessee) have reported infestations in all of their counties. The current reported distribution of Ae. albopictus was compared to ecoregions of the U.S. Environmental Protection Agency's Level III ecoregion map. Several areas are identified as probable candidates for extension of this species based on ecological characteristics of the landscape. In other areas, populations seem likely to become locally abundant in urban or suburban oases that do not reflect the native ecology of the region. The ability of Ae. albopictus to transmit a variety of pathogens of human and veterinary public health importance, coupled with its ability to colonize diverse ecological settings makes continued surveillance an important issue.

Comparison of two American biophysics mosquito traps: the professional and a new counterflow geometry trap.

Abstract: Large cage and field studies were conducted to compare the efficacy of 2 American Biophysics Corporation mosquito traps, the standard professional (PRO) trap and a new counterflow geometry (CFG) trap. The PRO trap utilizes conventional downdraft technology and the CFG trap uses a patent-pending technology. In large cage studies, similarly baited CFG traps captured approximately 1.7 times as many laboratory-reared Aedes taeniorhynchus as the PRO trap. The CFG trap baited with CO2 + octenol resulted in significantly reduced landing counts compared to all other treatments; mean landing count was reduced from 233.8 (12.99/min), when no trap was present, to 24.7 (1.37/min). In field studies against natural populations of woodland species, the CFG trap captured 7.8 times more mosquitoes than the PRO trap overall, and approximately 11 times more Anopheles crucians, Anopheles quadrimaculatus, and Culex erraticus.

Selection and characterization of temephos resistance in a population of Aedes aegypti from Tortola, British Virgin Islands.

Abstract: A collection of Aedes aegypti from Tortola, British Virgin Islands, with a high level of temephos resistance (46.8-fold at the 95% lethal concentration [LC95]) was selected to higher resistance with temephos in the laboratory. After 13 generations of pressure, the temephos resistance ratio increased to 180.6 (LC95), whereas in the absence of selection pressure the resistance ratio declined to 8.5. Relatively low levels of resistance or cross-resistance to other organophosphate and carbamate insecticides, and a high level of resistance to the pyrethroid permethrin were also observed. Synergism tests implicated detoxifying esterases in temephos resistance and the presence of elevated esterase activity was confirmed by biochemical tests; however, no evidence was found of insensitive acetylcholinesterase. Mendelian crosses indicated that temephos resistance was inherited as a monofactorial trait. The presence of high levels of temephos and permethrin resistance in Ae. aegypti has important implications for Aedes control programs.

Current status of Aedes albopictus and Aedes atropalpus in Italy

Abstract: Eight years after the 1st record in Italy, scattered foci of Aedes albopictus are reported in 9 regions and 107 municipalities belonging to 22 provinces, mainly located in the northeastern part of the country (Veneto region). In almost all infested areas the species is well controlled and at low levels of density, through source reduction and antilarval treatments. Aedes atropalpus, 1st recorded in 1996, remains limited to the original focus in the province of Treviso. Surveillance and control of both species are carried out by local health agencies within a national program coordinated by Istituto Superiore di Sanita (national Institute of Public Health).

The check is in the male: male mosquitoes affect female physiology and behavior.

Abstract: The accessory glands of male mosquitoes may produce substances that are transferred to females during mating and alter female physiology and behavior. The effects of male substances include the inhibition of subsequent female mating behavior, stimulation of oviposition and preoviposition behaviors, and the inhibition of host-seeking behavior. The circadian rhythmicity of females can also be altered and their metabolic priorities restructured, making them more likely to reproduce. The specific components that affect the female have yet to be completely identified, but the published reports are summarized.

Laboratory evaluation of selected larvicides and insect growth regulators against field-collected Culex quinquefasciatus larvae from Urban Dhaka, Bangladesh

Abstract: Five organophosphates (OPs) (chlorpyrifos, chlorpyrifos methyl, fenthion, malathion, and temephos), 3 pyrethroids (bifenthrin, cypermethrin, and permethrin), 1 phenyl pyrazole (fipronil), 2 microbial pesticides (Bacillus thuringiensis serovar. israelensis [B.t.i.] and Bacillus sphaericus), and 3 insect growth regulators (IGRs) (diflubenzuron, methoprene, and pyriproxyfen) were evaluated against field-collected Culex quinquefasciatus larvae from urban Dhaka, Bangladesh. The LC90 values of all OPs, except for temephos (LC90 = 0.0096 ppm), were high, ranging from 0.13 ppm (fenthion) to 2.882 ppm (chlorpyrifos methyl). Pyrethroid LC90 values were 0.021 ppm (bifenthrin), 0.00061 (cypermethrin), and 0.017 ppm (permethrin). Fipronil exhibited a superior activity with LC90 value of 0.000896 ppm. Technical powders of B.t.i. and B. sphaericus (VectoBac TP and VectoLex TP) were considered highly effective against the Cx. quinquefasciatus larvae. The IGRs also were effective with pyriproxyfen (LC90 = 0.0011 ppm), being 3 times and 47 times more active than diflubenzuron (LC90 = 0.0034 ppm) and methoprene (LC90 = 0.052 ppm), respectively. In general, toxicity ranking of chemicals and microbials tested was phenyl pyrazole > IGRs > pyrethroids > microbials > OPs.

Laboratory evaluation of biotic and abiotic factors that may influence larvicidal activity of Bacillus thuringiensis serovar. israelensis against two Florida mosquito species.

Abstract: A technical powder of Bacillus thuringiensis serovar. israelensis (B.t.i.) (VectoBac TP, 5,000 international toxic units [ITU]/mg), an aqueous suspension (VectoBac 12AS, 1,200 ITU/mg), and a granular formulation (VectoBac CG, 200 ITU/mg) were tested in the laboratory under different biotic and abiotic, conditions for efficacy against larvae of saltwater (Aedes taeniorhynchus) and freshwater (Culex nigripalpus) mosquitoes. Second-, 3rd-, and 4th-instar larvae of Cx. nigripalpus were 1.3-3-fold more susceptible to both VectoBac TP and VectoBac 12AS than were the respective larval instars of Ae. taeniorhynchus. For each species, 2nd-instar larvae were several-fold more susceptible to these B.t.i. preparations than were the 4th instars. In test cups, larvae under lower densities exposed to B.t.i. concentrations sustained 5-9-fold higher mortalities than larvae under high-density conditions. VectoBac TP and VectoBac 12AS stayed in suspension for up to 24 h with similar larvicidal efficacy, which was greater at 32-35 degrees C than at 15-20 degrees C. At 60 degrees C maintained for 24 h, VectoBac 12AS was adversely affected 2-3-fold in terms of potency, but VectoBac TP was not affected. Significant loss of potency of both VectoBac 12AS and VectoBac TP occurred when exposed to 35-37 degrees C under high light intensity (140,000-170,000 lux) for 6 h. Increasing salinity levels from 0 (fresh water) to 50% sea water caused gradual efficacy declines of VectoBac 12AS and VectoBac TP against Ae. taeniorhynchus larvae. VectoBac CG caused insignificant initial and residual (up to 8 days) larval mortalities of both mosquito species. This formulation did not release the active ingredient of B.t.i. in any significant mosquito larvicidal concentration in surface layers of water, and the formulation was more effective in shallower water. Storage of all 3 formulations under constant laboratory and variable field conditions for up to 8 months did not produce detectable potency loss of these products.

Malaria transmission in a region of savanna-forest mosaic, Haut-Ogooué, Gabon.

Abstract: During the 2 years 1993 to 1995, an entomological survey was carried out in the savanna-forest area of Franceville, Gabon, investigating malaria transmission in one suburban district of Franceville (Akou) and in one rural village (Benguia). The biting rates of the Anopheles vectors were 10 times higher in the rural zone compared to the suburban zone. Anopheles funestus Giles was the predominant species in both zones followed by Anopheles gambiae s.l. Giles. The densities of Anopheles nili Theobald and Anopheles moucheti Evans were very low. In the suburban zone, transmission was maintained throughout the year by An. funestus and An, gambiae s.l., whereas in rural zones the secondary vectors An, nili and An, moucheti were also involved in transmission. Humans in a suburban setting received one infective bite per person every 4 days, whereas in the rural area the infective biting rate was 4 times higher. Considering each vector, the observed entomological inoculation rates (EIRs) were one infective bite per person every 6 and 17 days for An, funestus and An, gambiae s.l., respectively, at Akou. At Benguia, the EIRs were one infective bite per person every 2, 3, 6, and 19 days for the 4 An, funestus. An, gambiae s.l., An, nili, and An, moucheti, respectively. The predominance of An, funestus over An, gambiae s.l. and its high EIR make it the most important malaria vector in this region of Haut-Ogooue.

Comparative effectiveness of three adult mosquito sampling methods in habitats representative of four different biomes of California.

Abstract: The effectiveness of New Jersey (NJ) light, dry ice baited, and gravid female traps for collecting adult mosquitoes was compared at representative habitats in the Coachella, San Joaquin, and Sacramento valleys and the Los Angeles basin of California. The NJ light traps effectively sampled Anopheles freeborni, Culex tarsalis, Psorophora columbiae, and several Aedes when abundance was high in rural areas with minimal competitive illumination. Dry ice-baited encephalitis virus surveillance or CDC style traps collected significantly more females of most species at most localities than did NJ light traps, regardless of background illumination. The Cummings modification of the Reiter gravid female trap baited with a bulrush (Schoenoplectus) infusion was the best method for collecting Culex pipiens complex females in most habitats. In the Los Angeles basin, gravid traps baited with bulrush infusion collected, on average, 4.5 times more Culex quinquefasciatus females than did traps baited with the Reiter infusion. The bulrush infusion in combination with the Cummings trap design seemed to provide resting site cues and collected males as well as empty and bloodfed females. Mosquito surveillance programs in California should include the systematic operation of dry ice-baited and gravid female traps to improve surveillance sensitivity for selected species in appropriate habitats.

Field evaluation of new water-dispersible granular formulations of Bacillus thuringiensis ssp. israelensis and Bacillus sphaericus against Culex mosquitoes in microcosms.

Abstract: A variety of formulations of Bacillus thuringiensis var. israelensis de Barjac (B.t.i.) and Bacillus sphaericus Neide (B.s.) have been studied for mosquito control under laboratory and field conditions. High efficacy, specificity, low risk of development of resistance, long shelf-life, and transportability, as well as the safety to nontarget organisms of these 2 microbial agents have been well documented. Some of the currently available formulations of B.t.i. and B.s. have low potency per unit mass. Research and development efforts are focusing on commercializing formulations with high potency and low minimum effective dosage that are suitable for long-distance shipment. To achieve this goal, new water-dispersible granule (WDG) formulations of both microbial agents were prepared and made available by Abbott Laboratories for evaluation. The newly developed WDGs of B.t.i. and B.s. with high potency dispersed readily in water with gentle agitation. These WDGs were evaluated and the minimum effective dosages were determined in microcosms against natural populations of Culex mosquitoes. The minimum effective dosage for B.t.i. WDGs with 4,000 International Toxic Units (ITU)/mg was 0.27-0.53 lb/acre which yielded significant control for up to 7-12 days. The minimum effective dosage for B.s. WDGs with 350-630 ITU/mg was 0.05-0.10 lb/acre, which yielded significant control of immature mosquitoes for up to 14-20 days.

First record of Aedes albopictus (Skuse) from Argentina.

Abstract: Aedes albopictus was collected in San Antonio City, Misiones Province, Argentina, near the border with Brazil in March, 1998. Collected material included 12 pupae, 1 recently emerged adult female, and a few larvae, which were found in a dish, a plough disk, and a tin pot. From the collected pupae, 5 males and 4 females emerged in the laboratory.

Seasonal distribution and relationship to temperature and precipitation of the most abundant species of Culicoides in five provinces of Andalusia, Spain.

Abstract: A total of 177,344 Culicoides specimens were collected from 3,109 light trap collections made weekly from August 1990 to October 1991 at 62 sites in the provinces of Cadiz, Cordoba, Huelva, Seville, and Malaga, Spain. Reported for the 1st time are Culicoides agathensis, Culicoides bahrainensis, Culicoides marcleti, and Culicoides odiatus in the Iberian Peninsula, and Culicoides scoticus in Andalusia, Spain. As a group, Culicoides were active throughout the year. The 3 most common species were Culicoides imicola (56,254), Culicoides newsteadi (24,359), and Culicoides circumscriptus (16,720). Numbers of C. imicola peaked in October, C. newsteadi peaked in May, and C. circumscriptus peaked in June. Based on regression analyses, the optimal minimum and maximum air temperatures, respectively, for adult insect activity were approximately > or = 18 degrees C and > or = 38 degrees C for C. imicola, 12 degrees C for C. newsteadi, 14 degrees C for C. circumscriptus (minimum temperature only), 16 degrees C and > or = 38 degrees C for "other" Culicoides, and 14 degrees C and 32 degrees C for total Culicoides. Optimal minimum and maximum temperatures could not be determined for Culicoides pulicaris, Culicoides punctatus, subgenus Monoculicoides, and the Culicoides obsoletus group. During August and September, the months when African horse sickness outbreaks occurred, C. imicola was the predominant species in the coastal Mediterranean zone. If the "other" Culicoides spp. group was not considered, the predominant species were C. imicola in the Guadalquivir River valley zone, C. newsteadi in the Subbetica mountainous range zone, and subgenus Monoculicoides in the coastal Atlantic zone.

Effects of high temperature on the emergence and survival of adult Culex pipiens molestus and Culex quinquefasciatus in Japan.

Abstract: The emergence rate and adult survival (longevity) of Japanese strains of Culex pipiens molestus and Culex quinquefasciatus were compared at temperatures of 21, 25, and 30 degrees C. The pupation and emergence rates in both strains were higher at 21 and 25 degrees C than at 30 degrees C. The adult emergence rate, especially in females, was lower in Cx. p. molestus than in Cx. quinquefasciatus. Longevity of females and males was lower in Cx. p. molestus at 25 degrees C and above. The survival of Cx. p. molestus was adversely affected by temperatures of 28 degrees C and higher. High temperature may restrict the distribution of this species. Therefore, if Cx. p. molestus infests the Okinawa region, the likelihood that it will become established is minimal.

Effects of sampling design on the estimation of adult mosquito abundance

Abstract: During 1994-5, Culex tarsalis comprised 75% of the 902,643 adult female mosquitoes collected by 63 dry-ice-baited Centers for Disease Control (CDC)-style traps operated biweekly in a uniform sampling grid that covered the southern Coachella Valley, Riverside County, California. The ln(y + 1) transformation successfully controlled the variance and normalized the distribution of catch size among trap nights. When tested by analysis of variance, abundance varied significantly among months, years, and trap sites. Although the trap by months interaction was not significant, female distribution changed seasonally as larval habitats shifted from wetlands along the Salton Sea to agriculture to managed duck marshes. Conditional simulations utilized subsets of trap sites to compare sampling designs that required no (uniform, random, and transect designs) or prior (best-estimate and stratified random designs) knowledge of mosquito spatial distribution. All designs provided similar information on population seasonal trends, but a stratified random design provided the most accurate and precise simulation. A uniform trap grid that employed every 2nd trap site subsequently was adopted by the Coachella Valley Mosquito and Vector Control District to provide information on focal changes in abundance indicative of missed or newly created larval habitats or control failures.

Aedes albopictus in Cuba.

Abstract: This is the 1st report of the occurrence of Aedes albopictus in Cuba. It was found in late 1995 in a variety of containers in the municipalities of La Lisa and Boyeros in Havana City.

Molecular population genetics of the primary neotropical malaria vector Anopheles darlingi using mtDNA.

Abstract: Samples of the neotropical malaria vector Anopheles darlingi from Bolivia, Brazil, and Venezuela were analyzed to test for differences in mitochondrial haplotype frequencies. With the use of molecular variance components and F-statistics, significant genetic variability of An. darlingi was found apportioned primarily among populations within regions or within populations, with regions defined either as biomes (n = 5) or ecoregions (n = 2). The Mantel analysis resulted in a significant correlation [Prob (r) = 0.009] between genetic and geographic distances, evidence that these populations are genetically isolated by distance. Such isolation could reflect differences in phenotypes for factors affecting vector capacity.

A male accessory gland protein that modulates female mosquito (Diptera: Culicidae) host-seeking behavior.

Abstract: The male accessory gland product that modulates the host-seeking behavior of female Aedes aegypti (L.) mosquitoes was found to be a peptide of 7,600 mw. This peptide also prevented subsequent mating behavior and weakly stimulated oviposition. Neither whole glands nor gland fractions from Anopheles gambiae had any effect on Ae. aegypti females, but those from Aedes albopictus were active.

Towards management of mosquitoes at Homebush Bay, Sydney, Australia. I. Seasonal activity and relative abundance of adults of Aedes vigilax, Culex sitiens, and other salt-marsh species, 1993-94 through 1997-98.

Abstract: The mosquitoes associated with 2 saline wetlands at Homebush Bay, Sydney. Australia, were investigated over 5 consecutive seasons. Twenty-one species were collected in adult traps at the 2 sites but the saline wetlands supported larvac of only 4 species: Aedes alternans. Aedes camptorhynchus, Aedes vigilax. and Culex sitiens. Of these, Ae. vigilax and Cx. sitiens were the most common, and their peak abundances generally occurred during February and April, respectively. Both wetlands were influenced by tides and rainfall-runoff, and a lack of regular tidal exchange in the mangrov es and inadequate drainage of the saltmarsh provided potential habitat. Populations of Ae. vigilax and Cx. sitiens at the Newington site were greater than those at the Bicen tennial Park site, because of more extensive habitat at the former, but were diminished by irregular ground-based applications of temephos during the middle 3 years of the study. Populations at the Bicentennial Park site. not subjected to the larvicide, were typically smaller but more consistently related to influences of tide and rainfall through the 5 seasons. During the final season, populations of both species in both wetlands were enhanced by exceptional tide penetration and rainfall. Helicopter applications of Bacillus thuringiensis israelensis larvicide were employed at both sites and effectively suppressed populations of both pest species. For future management, provision of full tidal exchange and water recirculation to reduce the area o water impounded within the mangroves and retained in depressions on the marshes should significantly suppress the pest populations and relieve reliance on control agents.

Comparative efficacy of the threespine stickleback (Gasterosteus aculeatus) and the mosquitofish (Gambusia affinis) for mosquito control.

Abstract: The effectiveness of the threespine stickleback as a mosquito control agent was compared to that of the mosquitofish in 28-m' earthen ponds during 2 6-wk experiments where the 2 fish were stocked alone and together. Relative to ponds without fish, the stickleback was not effective for controlling larval mosquito populations; however, sticklebacks reduced the abundance of Culex pupae. Mosquitofish provided significant levels of control whether stocked alone or concurrently with the stickleback. As compared to mosquitofish alone, mosquito control was not significantly enhanced when both fish were stocked together. Mortality of adult stick- lebacks was related to a gradient of increasing water temperature across the ponds rather than the direct effects of other abiotic factors such as low dissolved oxygen concentrations or biotic interactions with the mosquitofish. The stickleback exhibited a lower thermal tolerance and slower population recruitment as compared to the mosquitofish populations, which reproduced successfully in water >33"C and grew rapidly. Stickleback bromass either declined or increased slightly (-5OVo of initial stocking weighQ. Mosquitofish biomass increased 33- to 38-fold at rates averaging between 0.079 and 0.095 g wet weight/g/day and total wet weight per pond at 6 wk after stocking did not differ significantly between the 2 mosquitofish treatments.

Effects of ultra-low volume pyrethrin, malathion, and permethrin on nontarget invertebrates, sentinel mosquitoes, and mosquitofish in seasonally impounded wetlands.

Abstract: Wildlife managers are concerned that insecticides used to control mosquitoes could suppress invertebrates on which wildlife feed. We assessed whether ultra-low volume (ULV) applications of pyrethrin, permethrin, and malathion for control of adult mosquitoes reduced macroinvertebrate abundance and biomass or killed mosquitofish in seasonal wetlands in California. Pyrethrin was applied over 3 seasonal wetlands on Sutter National Wildlife Refuge (NWR), and malathion or permethrin were each applied over 2 seasonal wetlands on the Colusa NWR. Three control wetlands were used per site. We measured aquatic macroinvertebrate abundance and biomass before and after insecticide application and compared the survival of mosquito larvae held in sentinel cages. At Colusa, we also used mosquitofish as sentinels, caged adult mosquitoes over the wetlands to test for pesticide efficacy and drift, and sampled night-flying insects using ultraviolet light traps. Results showed no detectable reductions in the abundance or biomass of aquatic macroinvertebrates in treated wetlands. Larval mosquitoes showed high survival in all areas. All adult mosquitoes died when caged over wetlands treated with malathion or permethrin, but all survived in controls. All mosquitofish survived. Flying insect abundance decreased after insecticide application in both treated and control wetlands but rebounded in 48 h. Results indicated that ULV applications of these insecticides to control adult mosquitoes are unlikely to have substantial effects on the aquatic insects or fish in seasonal wetlands.

Evaluation of Costa Rican copepods (Crustacea: Eudecapoda) for larval Aedes aegypti control with special reference to Mesocyclops thermocyclopoides.

Abstract: This study attempted to find organisms for the biological control of the mosquito Aedes aegypti in Costa Rica. Copepods of the genera Arctodiaptomus, Eucylops, Mesocyclops, Megacyclops, and Thermocyclops were collected in several parts of the country and cultured for laboratory evaluations. Mesocyclops thermocyclopoides was the most successful species in reducing the number of larval Ae. aegypti (7.3 larvae in 24 h at a density of 200 Aedes/liter). Arctodiaptomus dorsalis, Eucyclops cf. bondi, Eucyclops leptacanthus, Megacyclops sp., and Thermocyclops decipens were not effective predators. In cage simulation trials, M. thermocyclopoides showed 100% larval reduction after 4 wk and adult mosquitoes disappeared after 7 wk. The copepod was able to survive in Aechmea sp. bromeliads under laboratory conditions. In field trials under 3 different climatic conditions M. thermocyclopoides survived 2-5 months in bromeliad leaf axils and 3-6 months in used car tires. In tires, this species reduced the number of larval Ae. aegypti 79, 90, and 99% in tropical dry, moderate, and humid climates, respectively. An El Nino phenomenon affected the results by drought, which apparently also caused a decline in the population of the predatory mosquito Toxorhynchites haemorrhoidalis superbus. Considering these severe test conditions, M. thermocyclopoides might be a promising predator for mosquito control in Costa Rica.

Increased fecundity of Aedes aegypti fed human blood before release in a mark-recapture study in Puerto Rico.

Abstract: Laboratory experiments suggest that utilization of blood rather than natural sugar sources for energetic needs affords female Aedes aegypti a reproductive advantage over conspecifics that use sugar. To test this hypothesis under field conditions, we carried out a mark-release-recapture study in Florida, PR. Adult females (F1) reared from field-collected eggs were provided with a diet of human blood alone or human blood plus a 20% honey solution before their release. Backpack aspirators were used to collect mosquitoes from release houses for 5 consecutive days beginning the 2nd day after release. Survival was estimated from the slope of the regression line of the log-transformed daily number of recaptures for each treatment group. To compare fecundity of the treatment groups, each recaptured female was dissected, ovaries were removed, oocytes counted, and Christophers' stages of oocyte development scored. Recapture rates were 30% for the blood-only group and 23% for blood plus honey group. The daily survival rate of the blood-only group (55%) was not statistically different from that of the blood plus honey group (69%) (t = 0.32, P > 0.05). By analysis of variance, fecundity (average number of stage III-V oocytes) was significantly higher in the females fed human blood alone (n = 103, 109 oocytes/female) than in the group fed on blood and honey (n = 50, 95 oocytes/female) (P = 0.0007). The observed gonotrophic cycle length of the recaptured females ranged from 3 to 7 days. Results from our field study are consistent with laboratory life-table experiments that suggest feeding exclusively on human blood provides a reproductive advantage for female A. aegypti.

Evaluation of a polymerase chain reaction assay for detection of pyrethroid insecticide resistance in the malaria vector species of the Anopheles gambiae complex.

Abstract: A published polymerase chain reaction assay proved reliable for detecting nerve-insensitivity (kdr-type) resistant and susceptible alleles to the pyrethroid insecticide permethrin in the malaria vectors Anopheles gambiae s.s. and An, arabiensis and the nonvector species An, quadriannulatus. The assay detects pyrethroid susceptible and resistance alleles mediated by a mutation in region II of the para-type sodium channel gene, showing that resistance is conferred by pyrethroid target site insensitivity. Analysis of results of the assay suggests that more than 1 mechanism conferring pyrethroid resistance is operating in an An, gambiae s.s. strain from Cote d'Ivoire. The value of the assay as a tool for monitoring this mode of insecticide resistance in wild populations is discussed.

Afro-tropical anopheline mosquitoes. III. Description of three new species: Anopheles carnevalei sp. nov., An. hervyi sp. nov., and An. dualaensis sp. nov., and resurrection of An. rageaui Mattingly and Adam.

Abstract: Anopheles (Cellia) carnevalei sp. nov. is described as a new species morphologically similar to Anopheles nili. This aggressive human biter was collected in Ivory Coast. Anopheles (Cellia) hervyi sp. nov. was collected in southern Niger and is described as a new species morphologically similar to Anopheles salbaii. Anopheles (Cellia) dualaensis sp. nov. is a new species from Duala in southern Cameroon. The synonymy of Anopheles cavernicolus and Anopheles smithii is confirmed. Based on extensive reexamination of larval and adult morphology, the authors suggest that Anopheles (Cellia) rageaui Mattingly and Adam should no longer be considered as a synonymn of An. smithii.

Potential for Central American mosquitoes to transmit epizootic and enzootic strains of Venezuelan equine encephalitis virus.

Abstract: Experimental studies were undertaken to compare the vector competence of Culex (Melanoconion) taeniopus Dyar and Knab, Culex (Melanoconion) ocossa Dyar and Knab, and Psorophora confinnis (Lynch Arribalzalga) from Central America for epizootic (IAB) and enzootic (IE) strains of Venezuelan equine encephalitis (VEE) virus. Virus infection and dissemination rates were significantly higher in Cx. taeniopus orally exposed to IE as compared to those orally exposed to IAB virus. In contrast, both infection and dissemination rates were similar in Cx. ocossa exposed to either IAB or IE strains of VEE virus. Thus, susceptibility to epizootic and enzootic strains of VEE virus seems to be species specific within the subgenus Culex (Melanoconion). Both species transmitted each strain of VEE virus after intrathoracic inoculation, indicating that a midgut barrier affected vector competence in these species. Psorophora confinnis was equally susceptible to both IAB and IE viruses, but apparently had a salivary gland barrier, as only 1 of 16 mosquitoes with a disseminated infection transmitted VEE virus by bite.

Responses of male and female mosquitoes to repellents in the World Health Organization insecticide irritability test system.

Abstract: A study was conducted to compare responses of male and female Aedes aegypti (Linn.) and Aedes taeniorhynchus (Wiedemann) to 9 olfactory repellents in the World Health Organization insecticide irritability test system. An irritant insecticide (permethrin) and a control were included for comparison. Aedes aegypti exhibited significantly more takeoffs than Ae. taeniorhynchus, and female mosquitoes exhibited significantly more takeoffs than males. Permethrin induced significantly more takeoffs than the control, but olfactory repellents did not. Certain 2- and 3-factor interactions of test materials, species, and sexes were statistically significant. This study supports a previous conclusion that the World Health Organization test method does not measure contact repellency (irritancy) and olfactory repellency equally.

Frequency of Wolbachia infection in laboratory and field sand fly (Diptera: Psychodidae) populations

Abstract: Using a polymerase chain reaction (PCR) assay with primers designed for the Wolbachia 16S rRNA and outer surface protein (wsp) gene, we screened 11 laboratory colonies and 4 field samples of 6 sand fly species for Wolbachia infection. Infection was only detected in 3 laboratory colonies of Phlebotomus papatasi Scopoli, originally collected in Israel, Egypt, and Saudi Arabia.