Auto-dissemination of commercially available fungal pathogens in a laboratory assay for management of the brown dog tick Rhipicephalus sanguineus.

Rhipicephalus sanguineus is a canine tick that infests dogs throughout the world and is frequently found in homes and dog kennels. Management of this tick species is complicated by the presence of resistance to commonly utilized acaricides. Fungal formulations could provide a valuable alternative tool for management and are especially relevant indoors where detrimental environmental effects on fungal spores are of less concern. Two commercially available fungal formulations, one containing Metarhizium anisopliae and the other containing Beauveria bassiana, were compared for time to death and sporulation in nymphal ticks exposed for 60 min in treated filter paper packets. Beauveria bassiana exposure killed ticks faster than M. anisopliae exposure and B. bassiana was more likely to sporulate on tick cadavers than M. anisopliae. To determine whether infected ticks could disseminate fungus to their conspecifics, ticks were marked and treated with fungus before being placed with untreated ticks. Fungus was successfully transmitted from treated to untreated ticks. Mortality of ticks exposed to B. bassiana-exposed conspecifics occurred sooner than for those exposed to M. anisopliae-exposed conspecifics, indicating faster dissemination in the former. Therefore, although both formulations resulted in decreased longevity of ticks compared with the controls, the B. bassiana formulation holds the most promise for direct or indirect application with respect to brown dog tick management.

Wingbeat Frequency-Sweep and Visual Stimuli for Trapping Male Aedes aegypti (Diptera: Culicidae).

Combinations of female wingbeat acoustic cues and visual cues were evaluated to determine their potential for use in male Aedes aegypti (L.) traps in peridomestic environments. A modified Centers for Disease control (CDC) light trap using a 350-500 Hz frequency-sweep broadcast from a speaker as an acoustic stimulus, combined with a black poster-board half-cylinder behind the trap as a visual stimulus, captured a significantly greater proportion of males in a laboratory arena during daylight than a CDC trap with the visual stimulus alone or a CDC trap alone without stimuli. Traps of each treatment type captured relatively more males when they were placed at darker positions in the arena. Potential applications are discussed for the incorporation of these findings into trapping programs to reduce transmission of human pathogens vectored by Ae. aegypti.

Vision in the common bed bug Cimex lectularius L. (Hemiptera: Cimicidae): eye morphology and spectral sensitivity.

Bed bugs as pests of public health importance recently experienced a resurgence in populations throughout the U.S. and other countries. Consequently, recent research efforts have focused on improving understanding of bed bug physiology and behaviour to improve management. While few studies have investigated the visual capabilities of bed bugs, the present study focused specifically on eye morphology and spectral sensitivity. A 3-D imaging technique was used to document bed bug eye morphology from the first instar through adult and revealed morphological characteristics that differentiate the common bed bug from the tropical bed bug as well as sex-specific differences. Electrophysiological measurements were used to evaluate the spectral sensitivity of adult bed bugs. Male bed bugs were more responsive than females at some wavelengths. Electrophysiological studies provided evidence for at least one photoreceptor with a spectral sensitivity curve peak in the green (λmax 520 nm) region of the spectrum. The broadened long wavelength portion of the spectral sensitivity curve may potentially indicate another photoreceptor in the yellow-green (λmax 550 nm) portion of the spectrum or screening pigments. Understanding more about bed bug visual biology is vital for designing traps, which are an important component of integrated bed bug management.

Insecticidal sugar baits for adult biting midges.

The mixing of an insecticide with sugar solution creates an oral toxin or insecticidal sugar bait (ISB) useful for reducing adult insect populations. The ability of ISBs to kill the biting midge Culicoides sonorensis Wirth and Jones (Diptera: Ceratopogonidae), a vector of bluetongue virus, epizootic hemorrhagic disease and vesicular stomatitis viruses, was tested. The commercial insecticide formulations (percentage active ingredient) tested included bifenthrin, cyfluthrin, deltamethrin, permethrin, dinotefuran, imidacloprid, thiamethoxam and spinosad. Mortality rates were determined for various concentrations of commercial formulations (0.01, 0.05, 0.1, 1, 2 and 3%) and observed at 1, 4, 10 and 24 h post-exposure to the ISB. In the first set of assays, laboratory-reared midges were fed sugar ad libitum and then exposed to insecticide-treated sugar solutions to measure mortality. The second assay assessed competitive feeding: midges were provided with a control sugar solution (10% sucrose) in one vial, and a sugar and insecticide solution in another. Pyrethroid treatments resulted in the greatest mortality in the first hour at the lowest concentrations and spinosad consumption resulted in the least mortality. Biting midges were not deterred from feeding on the 1% ISB solutions despite the presence of an insecticide-free alternative source of sugar.

Experience- and age-mediated oviposition behaviour in the yellow fever mosquito Stegomyia aegypti (=Aedes aegypti).

In repeated behaviours such as those of feeding and reproduction, past experiences can inform future behaviour. By altering their behaviour in response to environmental stimuli, insects in highly variable landscapes can tailor their behaviour to their particular environment. In particular, female mosquitoes may benefit from plasticity in their choice of egg-laying site as these sites are often temporally variable and clustered. The opportunity to adapt egg-laying behaviour to past experience also exists for mosquito populations as females typically lay eggs multiple times throughout their lives. Whether experience and age affect egg-laying (or oviposition) behaviour in the mosquito Stegomyia aegypti (=Aedes aegypti) (Diptera: Culicidae) was assessed using a wind tunnel. Initially, gravid mosquitoes were provided with a cup containing either repellent or well water. After ovipositing in these cups, the mosquitoes were blood-fed and introduced into a wind tunnel. In this wind tunnel, an oviposition cup containing repellent was placed in the immediate vicinity of the gravid mosquitoes. A cup containing well water was placed at the opposite end of the tunnel so that if the females flew across the chamber, they encountered the well water cup, in which they readily laid eggs. Mosquitoes previously exposed to repellent cups became significantly more likely to later lay eggs in repellent cups, suggesting that previous experience with suboptimal oviposition sites informs mosquitoes of the characteristics of nearby oviposition sites. These results provide further evidence that mosquitoes modify behaviour in response to environmental information and are demonstrated in a vector species in which behavioural plasticity may be ecologically and epidemiologically meaningful.

Behavioral and physiological response of Musca domestica to colored visual targets.

A better understanding of the visual attraction of house flies to colors and patterns is needed to improve fly trap performance. This study combined physiological responses measured with electroretinogram studies of the house fly's compound eyes and ocelli with behavioral attraction of flies to reflective colors and patterns in light tunnel assays. Compound eye and ocellar electroretinogram responses to reflected light were similar, with the largest responses to white and blue followed by yellow, red, green, and black. However, data from light tunnel behavioral assays showed that flies were attracted to white and blue light but were repelled by yellow. The addition of a black line pattern enhanced the attractiveness of blue visual targets, whereas yellow lines decreased attractiveness. Sensory input from the compound eye and the ocellus seems to be integrated to direct fly behavior. There is a direct correlation of house fly attractiveness to visual targets and the intensity of electrophysiological response, except for the yellow targets, which repel flies despite of intense electrophysiological response.

Aedes albopictus (Diptera: Culicidae) oviposition response to organic infusions from common flora of suburban Florida.

We evaluated the oviposition response of gravid Aedes albopictus (Skuse) to six organic infusions. Laboratory and field-placed oviposition cups baited with water oak (Quercus nigra L.), longleaf pine (Pinus palustris P. Mill), or St. Augustine grass (Stenotaphrum secundatum (Walt.) Kuntze), as well as binary infusion mixtures of each, were used. In addition, a triple-cage, dual port olfactometer was used to measure upwind response of gravid individuals to these infusions. We found that Ae. albopictus deposited more eggs in infusion-baited cups compared with water alone. Moreover, significantly more eggs were laid in the water oak and a water oak-pine mixture as compared with the St. Augustine grass infusion in laboratory bioassays. However, a negative upwind response was observed with longleaf pine infusion in the olfactometer. In field cages, significantly more eggs were deposited in infusion-baited cups as compared with water alone and a greater percentage of eggs were deposited in cups containing a water oak and the water oak-longleaf pine mixture as compared with cups containing single infusions or their mixtures.

Amino acids in nectar enhance longevity of female Culex quinquefasciatus mosquitoes.

Culex mosquitoes feed on a wide range of nectars consisting of mostly carbohydrates and amino acids, however, little is known about the utilization and effects of these different carbohydrates and their accompanying amino acids on longevity. Culex quinquefasciatus larvae were reared on low- and high-quantity food diets to produce adults that were nutritionally representative of wild-caught and laboratory-reared mosquitoes. Emerging adults reared on low- or high-quantity food diets as larvae were then provided Lantana camara nectar mimics containing mixtures of carbohydrates and amino acids to evaluate effects of nectar amino acids on longevity. Carbohydrates (with or without amino acids) were a critical component of the adult diet, and in their absence, adult mosquitoes died within 3-5 days. The nectar mimic that contained both carbohydrates and amino acids did not increase adult longevity of males originating from either poorly or well-fed larvae. However, females receiving adult diets containing both carbohydrates and amino acids lived 5% longer than females fed adult diets with only sugar.

Detection of and monitoring for Aedes albopictus (Diptera: Culicidae) in suburban and sylvatic habitats in north central Florida using four sampling techniques.

A sampling study using a BG-Sentinel trap baited with CO(2), a gravid trap baited with an oak-pine infusion, a human subject, and a vegetative aspirator was conducted to compare their reliability at detecting Aedes albopictus Skuse in suburban and sylvatic habitats. We collected 73,849 mosquitoes, representing 29 species from 11 genera over a 20-wk period. The BG-Sentinel trap accounted for over 85% of all Ae. albopictus captured and was significantly more effective at detecting the presence of Ae. albopictus compared with the other three techniques. Landing counts provided the fewest mosquito species (n = 10), yet provided a quick and effective weekly assessment of the major biting species and were the most effective method for sampling Ae. albopictus within a 10-min period. Fewer Ae. albopictus were sampled from sylvatic habitats compared with suburban ones. Sampling criteria advantageous for surveying Ae. albopictus and other mosquito species are discussed.

Infusion-baited ovitraps to survey ovipositional height preferences of container-inhabiting mosquitoes in two Florida habitats.

To ascertain mosquito species-specific oviposition height preferences, a study was conducted evaluating the response of field populations of container-inhabiting mosquitoes to water, oak (Quercus spp.),or oak-pine (Pinus spp.) infusion-baited ovitraps in four suburban and four sylvatic habitats in north central Florida. In total, 48 ovitraps, 24 suspended at each height of 1 or 6 m (near the ground or tree canopy, respectively), were monitored weekly for 5 mo. Throughout our study, we collected 13,276 mosquito eggs, representing five species from four genera, the most common being Aedes triseriatus (Say), Aedes albopictus Skuse, and Orthopodomyia signifera (Coquillett). Significantly more Ae. triseriatus and Ae. albopictus eggs were oviposited in containers with oak and oak-pine infusions compared with water alone. Significantly more Ae. albopictus eggs were recovered from traps at 1 m in suburban habitats, whereas more Ae. triseriatus eggs were recovered at 6 m in sylvatic habitats.

Host-seeking height preferences of Aedes albopictus (Diptera: Culicidae) in north central Florida suburban and sylvatic locales.

The response of Aedes albopictus to the BG-Sentinel, Omni-directional-Fay-Prince, and Mosquito MagnetX traps was evaluated in four suburban and four sylvatic habitats in north-central Florida to ascertain potential height preference of this species. These traps, which are primarily designed to attract diurnal mosquitoes, were set at 1 and 6 m and were evaluated during 40 trapping periods over 4 mo. We collected 45,640 mosquitoes, representing 26 species from 10 genera, the most common being Aedes albopictus, Ae. vexans, Coquilletidia perturbans, Culex nigripalpus, Aedes infirmatus, Ae. triseriatus, and Psorophora ferox. Although significantly more Ae. albopictus were captured at 1 m above ground than at 6 m, fewer were captured in sylvatic habitats than suburban habitats. Although not statistically different, the BG-Sentinel caught more Ae. albopictus compared with the other two traps regardless of locale. These results suggest that, although Ae. albopictus was captured as high as 6 m, the majority seek hosts at or below 1-m heights. This further supports prior research that, although Ae. albopictus has been shown to disseminate West Nile virus, it has not been implicated as a major vector for the virus, which is likely because of its propensity to feed on ground-dwelling hosts. The study also shows how trap type, trap heights, and environments influence sampling estimates when determining species abundance.

Evaluation of six mosquito traps for collection of Aedes albopictus and associated mosquito species in a suburban setting in north central Florida.

We compared 6 adult mosquito traps for effectiveness in collecting Aedes albopictus from suburban backyards with the goal of finding a more suitable surveillance replacement for the Centers for Disease Control and Prevention (CDC) light trap. Trap selection included 2 commercial propane traps (Mosquito Magnet Professional trap and Mosquito Magnet Liberty trap), 2 Aedes-specific traps (Fay-Prince Omnidirectional trap and Wilton trap), 1 experimental trap (Mosquito Magnet-X trap), and a standard surveillance CDC light trap that served as a control. Traps that did not generate carbon dioxide were provided with bottled CO2 at a flow rate of 500 ml/min. Those traps designed for use with chemical attractants (Mosquito Magnet traps) were baited with Lurex (L-lactic acid) and octenol (1-octen-3-ol) commercial baits, known attractants to Ae. albopictus. Three repetitions of a 6 x 6 Latin square test yielded a total of 37,237 mosquitoes, of which 5,280 (14.2%) were Ae. albopictus. Significantly more (P < 0.05) Ae. albopictus were collected from the experimental and commercial traps (4,244/5,280; 80.3%) than from the CDC light trap and Aedes-specific traps. The Mosquito Magnet Liberty collected the most Ae. albopictus (1,591), accounting for 30.1% of the total take, followed closely by the Mosquito Magnet-X (1,468) and the Mosquito Magnet Pro (1,185). The omnidirectional Fay-Prince trap performed better than the CDC or Wilton trap. Twenty-seven mosquito species were collected during these trials, 9 species in large enough numbers for meaningful analysis. Aedes albopictus was the second most common mosquito trapped. The results of these trials indicate that propane-powered commercial traps would serve as useful substitutes in lieu of CDC traps in Ae. albopictus surveillance efforts. Trap features advantageous for collecting Ae. albopictus and other mosquito species are discussed.

Evaluation of two commercial traps for the collection of Culicoides (Diptera: Ceratopogonidae).

Two types of commercial propane-powered traps, mosquito magnet (MM) (American Biophysics Corporation) MM-Freedom (Freedom) and MM-Liberty Plus (Liberty Plus), were evaluated for the collection of Culicoides. Trap preference and seasonal characteristics for the 3 major species, Culicoides furens, Culicoides barbosai, and Culicoides mississippiensis, were recorded from July 7, 2005, to July 24, 2006. Over 35 million Culicoides were captured during our study. When species were evaluated separately, analysis of overall mean trap collections yielded 5 months (February, March, June, September, and October) with significant trap effects. The Freedom trap captured more C. furens in June and October; the Liberty Plus trap captured more C. mississippiensis in February, March, and April, and more C. barbosai in September. The high numbers of Culicoides captured during our study suggest that the number of host-seeking Culicoides could potentially be reduced by continuous trapping during times when they are prevalent. Results of these investigations will be used to guide future control efforts.

Evaluation of the enantiomers of 1-octen-3-ol and 1-octyn-3-ol as attractants for mosquitoes associated with a freshwater swamp in Florida, U.S.A.

Field studies were conducted at wooded wetlands in Gainesville, FL, U.S.A., to assess responses of natural populations of adult mosquitoes (Diptera: Culicidae) to American Biophysics MM-X and Coleman MD-2500 traps baited with enantiomers of 1-octen-3-ol, a naturally occurring compound, and 1-octyn-3-ol, a closely related synthetic compound. Overall, the same species of mosquitoes were attracted by all enantiomers, although the (R)-(+) isomer of octenol generally attracted more species, and it is the isomer produced in greatest proportion in nature. Traps baited with the R-enantiomer caught greater numbers of mosquitoes than those baited with the S-enantiomer of each compound, whereas traps baited with S-enantiomers were equally or slightly less attractive than those baited with carbon dioxide only.

Evaluation of carbon dioxide, 1-octen-3-ol, and lactic acid as baits in Mosquito Magnet Pro traps for Aedes albopictus in north central Florida.

The impact of the attractants l-octen-3-ol (octenol) and L-lactic acid (LurexTM) on collection of Aedes albopictus in suburban backyards was assessed in Mosquito Magnet Pro traps. These carbon dioxide-producing traps were additionally baited with commercial formulated lures with octenol, lactic acid, octenol + lactic acid, or no attractant (control) and evaluated in 4 residential sites. Three repetitions of the study resulted in the total collection of 1,321 Ae. albopictus. Significantly more Ae. albopictus were captured in traps baited with octenol + lactic acid than in traps baited only with octenol. Lactic acid-baited and control trap captures were not significantly different from octenol + lactic acid- or octenol-baited trap totals. Octenol- + lactic acid-baited traps collected 36.2% and 52.0% more Ae. albopictus than lactic acid-baited and control traps, respectively. Male Ae. albopictus accounted for 26.7% of the total capture. Other mosquito species collected in sufficient numbers for analysis included Cx. nigripalpus, Ochlerotatus infirmatus, Psorophoraferox, and Cx. erraticus. Larger numbers of these species were collected in traps that were unbaited or baited with only octenol than in traps baited with lactic acid or octenol + lactic acid.

Attraction of mosquitoes to volatiles associated with blood.

Responses of the mosquitoes Aedes aegypti, Culex quinquefasciatus, and Culex nigripalpus to volatiles and compounds associated with bovine and avian blood that were presented in collagen membranes were evaluated in olfactometer and landing assays. The presence of attractants produced by blood was supported by more attraction of all species to blood than water controls in the olfactometer. Females of Ae. aegypti and Cx. quinquefasciatus were more attracted to bovine blood than to avian blood, but there was no difference in Cx. nigripalpus responses. In landing assays, significantly more females of all species landed on casings with blood than on water controls. There was no difference in landing of Ae. aegypti on bovine or avian blood. However, significantly more females of Cx. quinquefasciatus and Cx. nigripalpus landed on avian blood compared to bovine blood. Blood presented in collagen casings was an effective method for evaluating in-flight attraction and landing in all three species. In the olfactometer, several individual compounds elicited attraction in all species, but none were as attractive as blood for all species. In landing assays, several organic acids and sulfides elicited landing, with Ae. aegypti responding to the greatest number of compounds. These assay methods are effective for evaluation of volatile compounds from blood, and although responses were obtained to several compounds, none were as effective as blood in the olfactometer and landing assays.

Laboratory evaluation of avian odors for mosquito (Diptera: Culicidae) attraction.

Attraction of Culex quinquefasciatus Say, Culex tarsalis Coquillett, Culex nigripalpus Theobald, and Aedes aegypti (L.) to avian and other host odors was investigated in a dual-port olfactometer. Although attraction to a human arm was high for Ae. aegypti (>80%) and low for all Culex spp. (<25%), all species responded similarly to a chicken (55.3-73.6%). Responses of Ae. aegypti, Cx. quinquefasciatus, and Cx. nigripalpus to feathers were low (<20%) but greater than to controls. There was no difference in attraction of Cx. tarsalis to feathers or controls. Responses to CO2 (5 ml/min) were low for all species (<15%) except Cx. tarsalis, which were moderate (24.5%). When feathers were combined with CO2, the resulting attraction was additive or lower than responses to feather and CO2 alone for all species except for Cx. tarsalis, which had responses that were three-fold greater than expected if responses were additive. The CO2-feather treatments were less attractive than a chicken for all species. When olfactometer assays were extended from 3 to 20 min, responses by Ae. aegypti significantly increased to a chicken and CO2 and attraction of Cx. quinquefasciatus significantly greater to chickens, CO2, and feathers. None of the volatile compounds previously identified from feathers or uropygial glands tested were attractive. Both feather-rubbed cotton balls and hexane extracts of feathers were attractive and as attractive as feathers; however, ether extracts were not attractive. Feathers clearly contribute to the attraction of host-seeking Culex spp., and future studies will focus on identification of the attractant compounds.

Laboratory evaluation of a dyed food marking technique for Culex quinquefasciatus (Diptera: Culicidae).

A method of marking adult Culex quinquefasciatus by feeding the larvae commercial hog chow dyed with methylene blue, Giemsa, and crystal violet was evaluated under laboratory conditions. Of 243 mosquitoes fed the dyed food, 230 had visible marks (94.6%). The dyed food increased the egg-adult development time from 11.4 to 12.1 d. After 9 d, 82.5% of adult mosquitoes dyed as larvae could be identified, and remained detectable for up to 15 d, their maximum laboratory life.

Ixodid ticks on white-tailed deer and feral swine in Florida.

A state-wide survey was conducted in Florida during the 1997-99 hunting seasons to examine white-tailed deer (Odocoileus virginianus) and feral swine (Sus scrofa) for potential indigenous vectors of the rickettsial agent of heartwater, Cowdria ruminantium. A total of 504 white-tailed deer and 166 feral swine was examined from 30 wildlife management areas across the state. Amblyomma maculatum, an experimental vector of C. ruminantium, was common on both deer and feral swine throughout the state. Of the collection of 3,169 ticks, 34.5% were Ixodes scapularis Say, 34.0% Amblyomma americanum (L.), 25.5% Amblyomma maculatum Koch, 5.8% Dermacentor variabilis (Say), 0.4% Ixodes affinis Neumann, 0.03% Rhipicephalus sanguineus (Latreille) and 0.01% Amblyomma auricularium (Conil). The only exotic tick collected was A. auricularium, which is found on armadillos in Central and South America and is not known to be associated with any disease. Overall, the most prevalent species on deer were I. scapularis (51.1%) and A. maculatum (35.8%), with A. americanum less prevalent (16.0%) and D. variabilis (3.0%) and I. affinis (1.9%) rare. On feral swine, the most prevalent species were I. scapularis (69.7%) and D. variabilis (56.9%), with A. maculatum (16.2%) and A. americanum (4.6%) less common. The geographic distribution of ticks differed significantly throughout the state. Both A. maculatum and Dermacentor variabilis were more prevalent on deer from southern Florida compared to northern and central Florida. In contrast, A. americanum were more prevalent in northern and central Florida but rare in southern Florida, and I. scapularis were more common in southern compared to northern Florida. These geographic differences may reflect differences in the risk of tick-borne diseases to domestic animals, wildlife and humans within Florida.

Does geographic range affect the attractant-aggregation-attachment pheromone of the tropical bont tick, amblyomma variegatum?

The tropical bont tick, Amblyomma variegatum, transmits heartwater in sub-Saharan Africa and in the Caribbean. This species has a broad geographic distribution, ranging from Madagascar and other islands in the Indian Ocean through most of sub-Saharan Africa, to several islands in the eastern Caribbean Sea. Blood fed male A. variegatum secrete an attraction-aggregation-attachment (AAA) pheromone which, combined with CO2, excites host finding and formation of feeding clusters of these ticks. However, it is not known whether the composition of the pheromone varies throughout A. variegatum's geographic range. Extracts of fed male ticks were examined for phenols and volatile organic acids by gas chromatography and mass spectrometry to determine whether differences occur in the pheromone components of populations of this species across the geographic range (Guadeloupe, Zimbabwe, Zambia and Rwanda). No significant difference in the chemical composition of the pheromone in relation to geographic range was found. No significant differences in rates of attachment in response to native versus foreign extracts were found in on-host attachment tests comparing ticks from two countries. Guadeloupe (Caribbean) and Zimbabwe (African). This finding was confirmed in more detailed studies with ticks from Guadeloupe and four African countries (Kenya, Rwanda, Zambia and Zimbabwe). On-host attachment assays from these countries did not detect consistent differences in response to extracts from different locations. In an olfactometer bioassay, females were not consistently more attracted to extracts from their native locality than from any of the foreign localities. We conclude that despite the widespread distribution of A. variegatum over both hemispheres, no significant differences in pheromone composition or biological responses to male tick pheromone secretions occur.