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Biomedical subjects

E D Walker

Publications and source records attributed to E D Walker.

54 records · Page 3Linked to original sources
PubMed1989

Sampling, seasonal abundance, and mermithid parasitism of larval Coquillettidia perturbans in south-central Michigan.

Seasonal abundance of immature Coquillettidia perturbans was studied at 3 sites in south-central Michigan in 1987 and 1988. A modified boat bilge pump and funnel separators proved to be good sampling and sorting devices. Pupae were found in late May to early July, first and second instars were most abundant in July and August, while third and fourth instars were present year-round. Overall, larvae were most numerous in August and September, indicating that Cq. perturbans has a single generation per year in Michigan, with midsummer to fall as the main period of larval development, and with third and fourth larval instars as overwintering stages. Parasitism of Cq. perturbans larvae by a previously undiscovered mermithid nematode was documented at 2 sites in late summer.

Animals↗
PubMed1989

A broad evaluation of B.t.i. for black fly (Diptera: Simuliidae) control in a Michigan river: efficacy, carry and nontarget effects on invertebrates and fish.

Efficacy for black fly control, carry and nontarget effects of B.t.i. (Teknar HP-D), applied in the Betsie River, Michigan, were studied in June 1988. Black fly mortality was high (approximately 100%) for a 2,200 m stretch downstream from the application site, declined to 30% at 3,200 m, and was nil at 4,500 m. Drift of black flies greatly increased after application at a downstream site, but did not change at an upstream site. There were no detectable nontarget effects of B.t.i. application on: 1) invertebrate macro- or micro-drift; 2) numbers of invertebrates in benthic Surber samples; 3) mortality or feeding of drifting and nondrifting insects; 4) growth or mortality of caged Stenomena sp. larvae; 5) invertebrate functional group composition; 6) mortality or weight change of caged rock bass; or 7) fish numbers, species composition, length-weight (rock bass only) relationships or rock bass diet. Sampling of Rheotanytarsus sp. midges on natural substrates indicated low (27%) mortality owing to B.t.i. at only 100 m downstream from the application site, with negligible mortality at all other downstream and upstream sites. This information, combined with no pronounced changes in numbers of midges in macro-drift after application, indicated that midge populations were not adversely affected by B.t.i. in the study.

Analysis of Variance↗
PubMed1989

Population size and survivorship of adult Aedes triseriatus in a scrap tireyard in northern Indiana.

Population size and probability of daily survival of adult Aedes triseriatus were measured in a 0.03 ha section of scrap tireyard in South Bend, Indiana, using single-release, multiple-recapture methods. Average population size estimates ranged from 1,349 to 4,492 females (999 males in one experiment), demonstrating that population densities of Ae. triseriatus can reach levels in tireyards far exceeding densities in woodlots. The probability of daily survival was equivalent between males and females (0.78-0.82). When laboratory-reared small and large mosquitoes were released, small mosquitoes of both sexes were recaptured at lower rates than large mosquitoes, suggesting that experimental populations of small and large mosquitoes behave differently once released into the field, but that mark-recapture methods may not be sensitive enough to detect differences in survivorship.

Aedes↗
PubMedDate not supplied

Highland malaria in Uganda: prospective analysis of an epidemic associated with El Niño.

Malaria epidemics in African highlands cause serious morbidity and mortality and are being reported more frequently. Weather is likely to play an important role in initiating epidemics but limited analysis of the association between weather conditions and epidemic transmission parameters has been undertaken. We measured entomological variables before and during an epidemic of malaria (which began in February 1998) in a highland region of south-western Uganda and analysed temporal variation in weather data against malaria incidence (estimated from clinic records), mosquito density and entomological inoculation rates (EIR). Indoor resting density of Anopheles gambiae s.l. was positively correlated with malaria incidence (r = 0.68, P < 0.05) despite extremely low vector densities. EIR totalled only 0.41 infectious bites per person during the entire 8-month study period. Rainfall during and following the El Niño event in 1997 was much higher than normal, and rainfall anomaly (difference from the mean) was positively correlated with vector density 1 month later (r = 0.55, P < 0.05). Heavier than normal rainfall associated with El Niño may have initiated the epidemic; the relationship between temperature and transmission parameters remains to be defined. The results from this study indicate that, in this highland population, epidemic malaria may occur at extremely low inoculation rates.

Adolescent↗
PubMedDate not supplied

Toxicity of ozonated animal manure to the house fly, Musca domestica.

Swine manure slurries were ozonated at a dosage of 1 g/L and tested for their toxicity to the house fly (Musca domestica). The observed toxicity of ozonated swine manure was consistent and independent of origin of the swine manure. A dose (dilution) response curve was performed. A 50% dilution in the ozonated swine manure slurry resulted in 90% reduction in toxicity. Neither the synthetic nor ozonated synthetic swine manure, both of which contained higher concentrations of formaldehyde and three other unidentified carbonyl compounds than the ozonated swine manure, were toxic to the flies. Ozonated swine manure slurry was centrifuged and passed through a 0.45-microm filter. The liquid phase was as toxic as the unfiltered slurry; as such, the toxicant appears to be present in liquid phase. Neither ammonia, hydrogen sulfide, formaldehyde, nor other simple aldehydes appeared to be the toxic agent. The toxic agent appears to be a polar chemical compound and is concentrated in the urine. Several possible compounds have been identified. The toxicity of untreated and ozonated manure slurries from different livestock was compared. Six animal manure slurries (beef and dairy cattle, horse, poultry, sheep, and swine) were ozonated (dosage of 1 g/L) and tested for toxicity to the house fly. Ozonated dairy cattle manure slurry showed 78% mortality after 72 h, whereas ozonated swine manure slurry achieved a 100% mortality rate in 48 h. Neither the unozonated dairy nor swine manure slurries, nor any of the other raw or ozonated manure slurries, were toxic to the flies.

Animals↗
PubMedDate not supplied

Minority workers and communities.

Environmental and occupational hazards do not affect all communities equally. Members of ethnic and racial minorities, whether as working people or as community residents, sustain disproportionate risks from chemical, physical, and biological hazards. This paper reviews the nature of these disproportionate risks, focusing primarily on the workplace, but considering general environmental exposures as well. It discusses three principal mechanisms of increased risk: excessive hazardous exposures in both the workplace and the general environment, increased susceptibility, and inferior healthcare. It presents evidence that, as the result of these factors, members of minority groups display elevated rates of work-related illness, injury, fatality, and disability. Finally, it offers recommendations with regard to research, primary prevention, minority recruitment into the occupational health professions, and treatment and compensation for injured and ill minority workers.

Career Choice↗