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Biomedical subjects

E D Walker

Publications and source records attributed to E D Walker.

At least 37 records · Page 2Linked to original sources
PubMed1996

Borrelia burgdorferi-infected Ixodes scapularis (Acari: Ixodidae) and Peromyscus leucopus in northeastern Wisconsin.

Populations of the blacklegged tick, Ixodes scapularis Say, are established in western and central Wisconsin in the upper midwestern United States, but appear to be expanding geographically there. Here, we report a previously unknown population in northeastern Wisconsin. Questing I. scapularis nymphs and adults were collected by flagging vegetation from a riverine site in Marinette County, Wisconsin, in spring of 1993 and 1994. Dissection and culture of tick guts in modified Barbour-Stoenner-Kelley II medium showed that some of the ticks were infected with Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwald & Brenner, causative agent of Lyme disease. Fifteen of 30 white-footed mice, Peromyscus leucopus (Rafinesque), live-trapped at the site on 23-24 August 1994 were infested with immature I. scapularis, and ear-punch biopsies yielded B. burgdorferi cultures from 2 of the mice. However, none of 50 white-tailed deer, Odocoileus virginianus (Zimmermann), shot by hunters in Marinette County in November 1994 had I. scapularis on them, probably because no deer were shot at the same site where the tick population is located. These findings document existence of an established population of I. scapularis and a focus of Lyme disease in northeastern Wisconsin.

Animals↗
PubMed1996

Experimental evidence against replication or dissemination of hepatitis C virus in mosquitoes (Diptera:Culicidae) using detection by reverse transcriptase polymerase chain reaction.

In 3 laboratory experiments, mosquitoes were fed hepatitis C virus (HCV)-RNA positive blood by using membrane feeders, separated into head, thorax, and abdomen, and tested by a reverse transcriptase polymerase chain reaction for HCV-RNA. HCV did not replicate or disseminate in mosquitoes that had ingested blood from patients that were HCV-viremic positive. When yellow fever mosquitoes, Aedes aegypti (L.), were held for 1, 3, 7, 14, and 21 d after feeding, HCV-RNA was detected in the abdomens of 5/5 mosquitoes at 1 d after feeding; remaining tissues were negative with the exception of a single positive head at 7 d. In agreement, HCV-RNA was detected in Asian tiger mosquito, Aedes albopictus Skuse, and Anopheles stephensi Liston abdomens at 1 d, but not 3 d after feeding no HCV-RNA was detected in heads or thoraces. In addition, HCV-RNA was detected in heads of Ae. aegypti at 10 and 20 min, but not at 30 min, after feeding. The latter results raise the possibility of HCV contamination of mouthparts and, theoretically, mechanical transmission of this virus.

Aedes↗
PubMed1996

Deposition of malathion and permethrin on sod grass after single, ultra-low volume applications in a suburban neighborhood in Michigan.

Deposition of malathion and permethrin onto grass surfaces, after ultra-low volume (ULV) application, was studied in a suburban neighborhood in Saginaw County, Michigan. Commercial concentrates of malathion (Cythion ULV) and permethrin (Biomist 4 + 12) were sprayed using a truck-mounted ULV aerosol generator. Sod-grass blocks (0.18 m2) were placed in the frontyard and backyard of homes in the neighborhood at 4 distances to 91.4 m from the road where applications were made. Grass samples were taken from the sod blocks before application and at 15 min, 12 h, 24 h, and 36 h after application. Samples were extracted with solvent, and extractions were subjected to gas-liquid chromatography for detection of malathion and permethrin. Ranges of detection for malathion were 0.0-16.6 mg/0.18 m2 and for permethrin were 0.0-25.9 mg/0.18 m2. Most detections were from samples taken nearest the road at 15 min after application. Detections declined as a logarithmic function of time after application and as an exponential function of distance from the road.

Malathion↗
PubMed1995

Effect of low temperature on feeding rate of Aedes stimulans larvae and efficacy of Bacillus thuringiensis var. israelensis (H-14).

Experiments were conducted to determine the effects of low temperature (0 and 4 degrees C), vs. a high temperature (22 degrees C), on the feeding rate of Aedes stimulans larvae, and their susceptibility to Bacillus thuringiensis var. israelensis (H-14) (B.t.i.). Third-instar Ae. stimulans slowed but did not halt feeding at 0 and 4 degrees C compared to 22 degrees C. Susceptibility of larvae, as measured by LC50 values, to B.t.i. was highest at 22 degrees C (LC50 = 0.1 ppm), and lower at 4 degrees C (LC50 = 0.2 ppm) and 0 degree C (LC50 = 0.9 ppm). The data from the feeding and susceptibility experiments suggest that decreased efficacy of B.t.i. at low temperatures may occur because the rate of larval feeding decreases. Low water temperature should be a consideration during operational applications of B.t.i. for control of larvae in cold-water habitats, such as the spring Aedes species.

Aedes↗
PubMed1994

Prevalence of Borrelia burgdorferi in host-seeking ticks (Acari: Ixodidae) from a Lyme disease endemic area in northern Michigan.

The Lyme disease spirochete, Borrelia burgdorferi Johnson, Schmid, Hyde, Steigerwalt & Brenner, was recovered from the guts of questing Ixodes scapularis Say adults and nymphs and adult Dermacentor variabilis (Say), collected in Menominee County, Michigan, in 1992. Spirochetes were cultured successfully from guts placed in modified Barbour-Stoenner-Kelly II medium held in 5-ml cultures tubes or in 0.3-ml wells of microtiter plates. Most isolates were recovered within 2 wk of culturing at an incubation temperature of 34 degrees C. Spirochetes were recovered more rapidly in culture tubes than in microtiter plates. For determination of tick infection with B. burgdorferi, culturing was equivalent to examination of gut smears by immunofluorescence. We found the following infection rates: 57/179 I. scapularis females (31.8%), 62/204 I. scapularis males (30.4%), 9/54 I. scapularis nymphs (16.7%), and 5/383 D. variabilis adults (1.3%).

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PubMed1993

Bacterial enrichment in the surface microlayer of an Anopheles quadrimaculatus (diptera: culicidae) larval habitat.

Sampling of the surface microlayer of water in a marsh habitat of Anopheles quadrimaculatus Say in Michigan revealed it to be enriched with bacteria compared with subsurface water samples. Concentrations of total numbers of bacteria ranged from 18.8 x 10(6)/ml to 65.4 x 10(6)/ml (mean, 35.9 x 10(6)/ml; n = 13) in surface microlayer samples, and from 3.8 x 10(6)/ml to 14.3 x 10(6)/ml, (mean, 7.8 x 10(6)/ml; n = 13) in subsurface samples. Specifically, the surface microlayer had higher concentrations of three morphotypes of bacteria (cocci, rods, and rods attached to detritus particles). Given that bacteria are an important food of mosquito larvae, we suggest that the interfacial feeding behavior of An. quadrimaculatus larvae allows them to exploit the surface microlayer, a food-rich zone.

Animals↗
PubMed1993

Records of mosquito-parasitic mermithid nematodes in the northcentral United States.

Mermithid parasites (Nematoda: Mermithidae) were observed in 11 mosquito species in 22 counties of Indiana, Michigan, Minnesota, Ohio and Wisconsin. Natural hosts included adult Aedes vexans, Ae. canadensis, Ae. cinereus, Ae. diantaeus, Ae. punctor, Anopheles punctipennis and Coquillettidia perturbans and larvae of Ae. abserratus, Ae. canadensis, Ae. cinereus, Ae. communis, Ae. diantaeus, Ae. provocans, Ae. punctor, Ae. stimulans and Cq. perturbans. These are the first records of such parasites in Indiana, Minnesota, Ohio and Wisconsin.

Aedes↗
PubMed1993

Isolation of Jamestown Canyon and snowshoe hare viruses (California serogroup) from Aedes mosquitoes in western Massachusetts.

Three isolates of Jamestown Canyon virus and one isolate of snowshoe hare virus (California serogroup) were obtained from adult Aedes females collected in western Massachusetts in 1982. Jamestown Canyon virus was isolated from Aedes abserratus/punctor once, and from Aedes intrudens twice. Snowshoe hare virus was isolated from Aedes stimulans group mosquitoes. La Crosse encephalitis (LAC) virus was not isolated from 1,552 adult Aedes triseriatus, nor from 22,557 Aedes triseriatus larvae. However, sera from 1/178 eastern chipmunks, 5/31 gray squirrels, and 8/144 white-tailed deer had neutralizing antibody to LAC virus. No sentinel rabbits placed at sites yielding virus isolates seroconverted to CAL viruses in either year.

Aedes↗
PubMed1992

Evaluation of methoprene (Altosid XR) sustained-release briquets for control of culex mosquitoes in urban catch basins.

A sustained-release, briquet formulation of methoprene (Altosid XR), applied at a rate of one briquet per catch basin in Saginaw, Michigan, provided ca. 70% reduction in emergence of Culex pipiens and Cx. restuans adults, compared with nontreated catch basins, during a period of 15 wk in the summer of 1990. In a parallel study using one briquet per 10.5 liter bucket, there was 99% reduction in adult emergence of these species for a period of 12 weeks. The difference between catch basins and buckets may be attributable to water movement through the catch basins with each rainfall, causing a dilution of methoprene through time. However, both studies indicated that the briquets released methoprene for 12-15 wk, suggesting that this formulation may offer season-long control of Culex mosquitoes from urban catch basins in Michigan, with a single treatment of insecticide.

Animals↗
PubMed1991

Aedes triseriatus (Diptera: Culicidae) and La Crosse virus. IV. Nutritional deprivation of larvae affects the adult barriers to infection and transmission.

Groups of Aedes triseriatus (Say) were reared either as nutritionally deprived (two regimens) or well fed (one regimen) throughout larval development, and the vector competence of resulting small, normal, and large females was assessed for La Crosse virus. When fed a high dose of virus (4.6 log10/0.025 ml in Vero cell culture), 90% of small Ae. triseriatus females transmitted La Crosse virus to suckling mice compared with 70% of normal and 42% of large females. Among small females, 100% had disseminated infections as did 86% of normal females, whereas only 69% of large females had disseminated infections. All females had infected mesenterons (midguts). When fed a low dose of virus (2.2 log10/0.025 ml in Vero cell culture) in a second experiment, 15% of small females transmitted compared with 0% of large females; 50% of small females developed disseminated infections compared with 16% of large females. mesenteronal infection occurred in 70% of small but only 32% of large females. Electron microscopy of mesenteronal tissues from large and small females revealed physical differences in the basement membranes (basal laminae). The mesenterons of small females had 3-6 laminae (mean thickness of the basement membrane = 0.14 microns) compared with 9-16 laminae (mean thickness of the basement membrane = 0.24 microns) in large females. These morphological differences indicated that the mesenteronal escape barrier, which accounted for the difference in the percentage of small and large females with disseminated infections, may be, in part, a physical barrier that was modified by nutritional deprivation in the larval instars.

Aedes↗
PubMed1991

Behavior of larval Aedes triseriatus (Diptera: Culicidae).

The behavior of Aedes triseriatus (Say) fourth instars was studied in laboratory microcosms. A list of 14 larval behaviors was developed from observations of 108 larvae performing 1,836 different acts, and a time budget was developed from 88 larvae by recording the proportion of time each larva spent in the different behavioral states. Larval behavior was organized into clusters of surface and subsurface activities, linked by "dive" and "rise" behaviors. Eight behaviors formed the major activity pattern for larvae and dominated the time budget. Feeding behavior consisted of suspension feeding, feeding at the air-water interface, brushing container and leaf surfaces, and chewing leaf veins. Most (90.8%) of the time budget was devoted to feeding, and larvae spent 52.5% of their time feeding at or near the surface of the water and 37.5% brushing while submerged. When feeding at the air-water interface, larvae rotated about the axis formed by the respiratory siphon in alternating clockwise and counterclockwise directions, possibly to rest the muscles used to twist the larval body into the U-shaped posture characterizing this feeding behavior. Our studies showed that Ae. triseriatus larvae were not exclusively brushers nor bottom feeders as has been assumed for many Aedes larvae but showed great flexibility in feeding, where nearly the entire habitat was the "feeding zone."

Aedes↗
PubMed1991

Aerially applied, liquid Bacillus thuringiensis var. Israelensis (H-14) for control of spring Aedes mosquitoes in Michigan.

Liquid B.t.i. (Vectobac 12AS), when mixed with water at a 1:3 ratio and applied by helicopter at a rate of 1.17 liters B.t.i. (4.68 liters mix) per ha, was 99% effective in a small (mass median diameter on dye cards: 178 microns) droplet size but ineffective (65%) in a large (553 microns) droplet against spring Aedes larvae in snowmelt pools. There were about 6 times as many smaller droplets as larger ones impacting the treated pools, which probably explained the difference in effectiveness for the 2 treatment regimes. Results indicate that liquid formulations of B.t.i. could be aerially applied for spring Aedes control at a considerable cost savings and efficiency over aerially applied, granular formulations.

Aedes↗
PubMed1990

Evaluation of fenoxycarb against spring Aedes mosquitoes in Massachusetts.

The insect growth regulator, fenoxycarb, when applied at 0.06 kg AI/ha (0.05 lb AI/acre) as 1% sand granules was highly effective (97.5% corrected mortality) against Aedes communis, Ae. stimulans and Ae. canadensis in snowmelt pools in Massachusetts, and 100% effective against Ae. abserratus in an insectary study. No larval mortality owing to fenoxycarb treatment was observed, and most mortality occurred in the pupal stage as opposed to aborted adult emergence.

Aedes↗
PubMed1990

Natural food and feeding behavior of Coquillettidia perturbans larvae.

The natural particulate food of larval Coquillettidia perturbans was studied through gut analysis using staining with 4'6-diamidino-2-phenylindole and epifluorescence microscopy. Bacteria (cocci, rods, spirochetes, purple bacteria and cyanobacteria), detritus, euglenoid protozoans and algae (desmids and diatoms) comprised the majority of particulate food, in order of abundance; other protozoans were rare, and hyphal forms (actinomycetes and fungi) were not observed. Abundance of food items in guts did not vary greatly among sampling months (June-December, 1987) or sampling sites. Fourth instars had a greater proportion of euglenoids and algae in their food than did younger instars. Observation of larval feeding behavior showed that fourth instars oriented upside down and fed mainly by suspension feeding, with occasional brushing from sediments and root surfaces. Microtrichia on filaments of the lateral palatal brushes of fourth instars indicated that the larvae were adapted to collect fine particles.

Animals↗