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Biomedical subjects

D R Barnard

Publications and source records attributed to D R Barnard.

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

Human blood-feeding rates among sympatric sibling species of Anopheles quadrimaculatus mosquitoes in northern Florida.

We compared rates of feeding on human hosts for blood-engorged female Anopheles quadrimaculatus species A, B and C1 collected from daytime resting sites in Manatee Springs State Park, Levy County, Florida during 1992-1993. Quick-blot DNA probes were used to identify mosquito taxa and also the presence of human blood in the mosquito gut. In collections from a campground area, human blood-feeding rates differed significantly among mosquito species (10.7% [19 of 177], 0%, [0 of 62], and 1.2%, [4 of 327]), respectively for species A, B and C1). In collections from a woodland site (1 km from the campground), 1.5% (2 of 129) of the species B females had fed on humans, whereas none of 19 species A or 159 species C1 females had done so. Of the three species in this study area, species A appears the most likely to be a biting pest of humans and a vector of human malaria.

Animals↗
PubMed1996

Morphologic, immunologic, and cytogenetic classification of acute myeloid leukemia and myelodysplastic syndrome in childhood: a report from the Childrens Cancer Group.

The purposes of this report are to reaffirm concordance difficulties with the acute myeloid leukemia (AML) French-American-British (FAB) classification, to present the frequency of previously delineated AML syndromes in pediatric patients and to describe additional characteristic AML profiles utilizing composite morphologic, cytogenetic and immunophenotypic data. Profiles of 124 children with acute myeloid leukemia (AML) and 13 children with myelodysplastic syndrome entered on the Childrens Cancer Group (CCG) pilot study CCG-2861 were examined. Concordance between institutions and reviewers for FAB designation was 65%. Discordance was found principally between M1 and M2, M2 and M4, and M4 and M5. In 49% of marrow specimens, leukemic blasts expressed at least one T lineage-related antigen; 24% expressed the B lineage-related antigen CD19. CDw14 correlated with FAB M4 or M5 morphology and was the only surface antigen associated with a specific FAB subtype. Normal karyotypes were found for 15% of the 75 children with satisfactory karyotype preparations. Recurring aberrations, found in 76% of children, included t(15;17)(q22;q11), t(8;21)(q22;q22), inv(16)(p13q22), rearrangements of band 11q23, t(6;9) (p23;q34), trisomy 8 and monosomy 7. Results from this pilot study and from the current CCG randomized trial correlating morphology, immunophenotyping and cytogenetics, will help to classify AML into unique subgroups with differing clinical consequences or therapy requirements.

Adolescent↗
PubMed1996

Human host avidity in Aedes albopictus: influence of mosquito body size, age, parity, and time of day.

Diel patterns of human host attack by Aedes albopictus in the laboratory were studied in relation to mosquito body size, age, parity, and time of day. Analysis of responses in 10-, 15-, and 20-day-old females indicated a significant main effect due to time of observation in the diel period, as well as significant time x parity and time x age interactions. The distribution of mean host attack responses during the diel period was bimodal with approximately 70% of all activity during photophase (0800-2000 h); attack rates were highest in the morning (0800 h) and evening (1400-2000 h) and lowest between 0200 and 0600 h. The diel pattern of attack responses was bimodal for nulliparous and parous females, but parous females were more active than nulliparous females between 1400 and 2000 h. This pattern became increasingly bimodal during photophase, as mosquitoes aged, regardless of mosquito body size or parity. Variations in host avidity patterns between young and old females suggest that mosquito repellent bioassays initiated early in the day, that last > or = 6 h, or that use young females (approximately 5 days old) overestimate the protection period of deet against mosquitoes > 10 days old.

Aedes↗
PubMed1995

Anopheles perplexens from artificial containers and intermittently flooded swamps in northern Florida.

Anopheles perplexens was collected from habitats previously unreported for this species in northern Florida. These habitats included intermittently flooded swamps, water-filled tires, and plastic oviposition cups. First-instar An. perplexens larvae were recovered from soil samples collected in an intermittently flooded swamp that were flooded in the laboratory, suggesting that An. perplexens eggs may survive in the soil during dry periods. Anopheles perplexens larvae were collected from water-filled tires and plastic oviposition cups at sites near Gainesville, FL. Of 30 dissected An. perplexens females collected in updraft CDC traps, all had ovarioles in Christophers's stage II and blood was absent in the midgut. The physiological state of these females indicates that updraft CDC traps collect predominately host-seeking females and that females take one blood meal per gonotrophic cycle.

Animals↗
PubMed1995

Influence of body size and age of Aedes albopictus on human host attack rates and the repellency of deet.

Human host attack rates and the repellency of deet (25% in ethanol) to nulliparous Aedes albopictus in the laboratory were significantly influenced (P = 0.05) by mosquito age and body size and by the interaction of age and body size. Host attack rates were higher for 20-day- (24.5%) and 15-day-old females (22.9%) than for 10- (15.1%) and 5-day-old females (11.0%), regardless of body size, and for large females (22.2%) compared with small females (16.6%), regardless of mosquito age. Deet on human skin repelled small-bodied females longer (3.87 h) than large females (2.31 h); 15-day-old females were repelled longer (3.75 h) than 5- (2.33 h), 10- (3.08 h), or 20-day-old females (3.07 h), regardless of body size. Host attack rates and deet repellency among 15-day-old parous and 15-day-old nulliparous large- and small-bodied female Ae. albopictus were similar but deet repellency was less (by approximately 2 h) against large females compared with small-bodied females.

Aedes↗
PubMed1994

Integrated management strategies for Amblyomma americanum (Acari: Ixodidae) on pastured beef cattle.

Data on tick control and knowledge of the damage caused to beef cattle by tick feeding were incorporated into a computerized dynamic life table model (LSTSIM) for Amblyomma americanum (L.). Simulations were made to determine economically feasible, 5-yr integrated pest management (IPM) strategies for A. americanum in forage areas utilized by Bos taurus, Bos indicus, and crossbred cattle (B. taurus x B. indicus). The effects of host resistance, pasture rotation, habitat conversion, topical acaricides, systemic acaricides, and the area-wide application of acaricides to pastures on populations of parasitic female ticks were simulated as individual control technologies and as components of multiple-factor IPM strategies. The most effective, single-factor control strategy for A. americanum in beef cattle forage areas is the use of tick-resistant B. indicus cattle. Pasture rotation combined with area-wide acaricide applications was the only economically feasible IPM strategy for B. indicus cattle and reduced tick densities by 89% after 5 yr. Thirteen economically feasible IPM strategies were identified for use with B. taurus cattle. Of these, the most efficacious was pasture rotation in May combined with systemic or topical acaricide applications. Other strategies included systemic acaricides with area-wide acaricide applications to pastures, topical acaricides with area-wide acaricide applications, pasture rotation with habitat conversion and topical acaricides, and pasture rotation with habitat conversion, topical acaricides, and area-wide acaricide applications. Each technology reduced tick densities on B. taurus cattle by > 80% over a 5-yr period. Nine IPM strategies were economically feasible for use with crossbred cattle. Of these, pasture rotation combined with systemic or topical acaricide applications reduced the number of female ticks on cattle by > 84%; pasture rotation combined with habitat conversion reduced tick numbers by 77%. The most effective nonacaricide-based IPM strategy for B. taurus and crossbred cattle was pasture rotation combined with habitat conversion. No acaricide-free IPM strategy was economically feasible for use with B. indicus cattle.

Animals↗
PubMed1994

Comparison of bi-directional Fay, omni-directional, CDC, and duplex cone traps for sampling adult Aedes albopictus and Aedes aegypti in north Florida.

We compared the number of Aedes albopictus and Aedes aegypti females collected in CDC, duplex cone, bi-directional Fay, and new omni-directional traps in a series of trials in northern Florida during 1992 and 1993. Bi-directional Fay and omni-directional traps collected significantly more Ae. albopictus females than did the other traps tested. The bi-directional Fay trap collected significantly more Ae. aegypti females than did any other trap. The results of these studies indicate that these traps may be useful tools for sampling Ae. albopictus and Ae. aegypti adults.

Aedes↗
PubMed1993

New version of LSTSIM for computer simulation of Amblyomma americanum (Acari: Ixodidae) population dynamics.

A previous version of Lone Star Tick Simulation Model (LSTSIM) for a wildlife ecosystem was revised and expanded to include a beef cattle forage area and improved handling of tick-host-habitat interactions. Relationships between environmental and biological variables were also refined in the new version. General validity of the revised model was established by comparing simulated and observed host-seeking populations of Amblyomma americanum (L.) at five geographic locations, three in Oklahoma and two in Kentucky-Tennessee. Additional validity was indicated from comparisons of simulated and observed seasonality of lone star ticks at one location in Kentucky. The model produced acceptable values for initial population growth rate, generation time, and 15-yr population density when historical weather files for 14 locations in the United States were used. The model of A. americanum population dynamics was used to study the relationship between tick density and density of white-tailed deer, Odocoileus virginianus (Zimmerman), and cattle. The revised model can be used for additional simulation studies on effects of tick control technologies and integrated management strategies.

Animals↗
PubMed1993

Short-term changes in the abundance and parity rate of Anopheles quadrimaculatus species C (Diptera: Culicidae) in a central Florida swamp.

Updraft CDC traps baited with dry ice were used to monitor changes in the abundance and parity rate of Anopheles quadrimaculatus Say complex mosquitoes in an intermittently flooded swamp in Central Florida during an 18-d period. Mosquitoes collected each day were identified to species using DNA hybridization and isozyme electrophoretic techniques and were dissected to determine follicular maturation and parity. Of 1,178 An. quadrimaculatus mosquitoes identified to species, 4% were species A and 96% were species C. Dissections of females of both species indicated that 98% were nonblood fed and nongravid with ovariole development at Christophers' stage II. Overall parity rates were 0.19 and 0.51 for populations of species A and species C, respectively. The duration of the gonotrophic cycle for species C females was estimated to be 5 d based on the interval between peaks in the number of nulliparous females collected on days 1 and 6 and peaks in the number of parous females collected 5 d later. Significant trends were observed in the number of parous species C females collected each day, indicating that the parity rate could not be used as an unbiased estimator of survivorship.

Animals↗
PubMed1991

Mechanisms of host-tick contact with special reference to Amblyomma americanum (Acari: Ixodidae) in beef cattle forage areas.

At least five groups of parameters regulate contact between ticks and host animals. Group 1 (seasonal effects) and group 2 (daily effects) comprise abiotic parameters and include daylength, temperature, relative humidity, and interactions thereof. Groups 3, 4, and 5 consist of biotic parameters. These pertain to biological processes in ticks (group 3), such as hunger responses and spatial patterns in aphagous tick populations; biological processes in host animals (group 4), such as patterns of habitat use by host animals; and interactions between host animals and ticks (group 5). Host-tick contact is possible when ticks are hungry, when ticks exhibit a positive appetence response, and when ticks and host animals are together in time and space. A descriptive model is proposed to correlate these processes and interactions with the observed behavior of the host-tick contact system in nature. Emphasis in the model is placed on host activity and differences among host types.

Animals↗
PubMed1990

Plasma therapy for severe hemolytic-uremic syndrome in children in Atlantic Canada.

Clinical reports have suggested that therapy with fresh frozen plasma is a useful adjunct in the management of the hemolytic-uremic syndrome (HUS). We reviewed the charts of 36 children with severe HUS who were treated at the Izaac Walton Killam Hospital for Children, Halifax, over 10 years to assess the effectiveness of plasma therapy. All children who required specific supportive therapy for renal dysfunction, hemolysis or serious extrarenal complications were included. We compared the outcome of 18 children who received plasma therapy from 1982 to 1987 with that of 18 children who did not. The two groups were similar with regard to the severity of HUS, the length of hospital stay, the duration of renal dysfunction and the incidence of disease-related complications, such as seizures, enterocolitis and cardiomyopathy. At discharge the prevalence of hypertension was higher in the plasma therapy group than in the control group. Plasma therapy did not demonstrate any benefit that would outweigh the risk of fluid overload, hyperproteinemia and transmission of viral infection.

Acute Disease↗
PubMed1990

Population growth rates for Amblyomma americanum (Acari: Ixodidae) on Bos indicus, B. taurus and B. indicus x B. taurus cattle.

Densities of Amblyomma americanum (L.) on Bos indicus, B. taurus and B. indicus X B. taurus cattle are compared over a 3-year period, and the growth rate (rate of increase or decrease) of parasitic tick populations on each cattle genotype is estimated. Average log10 densities of parasitic A. americanum larvae are significantly (P = 0.05) lower on B. indicus cattle than on B. taurus and B. indicus XB. taurus cattle. Average log densities of nymphal and adult ticks on B. taurus cattle are significantly higher than on B. indicus cattle but neither cattle genotype differs in this regard from B. indicus X B. taurus cattle. Estimated annual tick population growth rates (log10) for parasitic A. americanum are positive on B. taurus cattle (+0.84 larvae, +0.09 nymphs, +0.22 adults calf-1 year-1), but are negative on B. indicus (-0.18 nymphs, -0.14 adults calf-1 year-1) and B. indicus X B. taurus cattle (-0.45 larvae, -0.24 nymphs, -0.14 adults calf-1 year-1). Populations of parasitic larvae were not detected on B. indicus cattle.

Animals↗
PubMed1990

Cattle breed alters reproduction in Amblyomma americanum (Acari: Ixodidae).

Female Amblyomma americanum [L.] that feed on Bos taurus cattle weigh significantly (P = 0.05) more (mean = 505.4 mg) than females that feed on B. indicus x B. taurus cattle (mean = 450.7 mg) but not females that feed on B. indicus cattle (mean = 489.7 mg). Females that feed on B. taurus cattle lay more eggs (mean = 3492) and produce more larvae (mean = 3243) than females that feed on B. indicus cattle (mean = 3103 eggs; 2925 larvae) or B. indicus x B. taurus cattle (mean = 2961 eggs; 2759 larvae). The number of eggs produced per unit engorged female weight is not significantly different in ticks that feed on B. taurus and B. indicus x B. taurus cattle.

Animals↗
PubMed1990

Management of lone star ticks (Acari: Ixodidae) in recreational areas with acaricide applications, vegetative management, and exclusion of white-tailed deer.

A project on management of lone star ticks, Amblyomma americanum (L.), at Land Between the Lakes, a Tennessee Valley Authority recreational area in Kentucky-Tennessee, during 1984-1988, demonstrated the effectiveness and economics of three control technologies. Acaricide applications (chlorpyrifos at 0.28 kg [AI]/ha), vegetative management (mowing and removal of 40% overstory and 90-100% of midstory, understory, and leaf litter), and host management (white-tailed deer exclusion from a 71-ha campground with a single-line fence) provided 75, 70, and 64% mean controls of all life stages of the lone star tick, respectively. Combinations of acaricide applications + vegetative management, acaricide applications + host management, and acaricide applications + vegetative management + host management produced 94, 89, and 96% mean control of all life stages, respectively. The costs of acaricide applications (two per year), vegetative management (two mowings per year), and white-tailed deer exclusion (single-line fence) were $45, $150, and $30/ha/yr, respectively. Results of this project are used to design management strategies that could be considered for use against lone star ticks in recreational areas.

Analysis of Variance↗
PubMed1989

Sites of attachment and density assessment in Amblyomma americanum (Acari: Ixodidae) on nursing beef calves.

Primary attachment sites of male, female, and nymphal Amblyomma americanum (L.) on nursing beef calves were the axillary, inguinal and perianal areas of the body. About 50% of all larvae fed on the ears. A density assessment method which uses the number of A. americanum on less than or equal to 5 body areas to predict the total number of ticks (tick burden) on the left side of a calf is presented. Estimates of tick burden for male, female, nymphal and larval A. americanum each require examination of the axillary, inguinal, and perianal body areas. In addition, to estimate larval and male A. americanum, the neck, dewlap and brisket require examination as do the ears for estimates of nymphs and larvae. Mean tick burden in a herd of calves can be estimated by an examination of from 14 to 100% of all calves depending on the level of precision required for the estimate.

Animals↗
PubMed1989

Habitat use by cattle affects host contact with lone star ticks (Acari: Ixodidae).

The location of Zebu, British, and Zebu x British cattle in tick-infested plots from March through September 1986 was compared with the location of Amblyomma americanum L. in the same plots. In April, May, and June, Zebu cattle spent less time (9.3-19.4%) in tick-infested quadrats than British (44.4-63.9%) or Zebu-British (49.0-69.3%) cattle. In the same months, the probability that A. americanum would contact Zebu cattle (1.5-19.6%) was significantly lower than for British (34.7-41.7%) or Zebu-British (30.2-56.9%) cattle. In April, May, June, and September, the probability that A. americanum detaching from cattle would drop into a quadrat presumed to be habitable for ticks was significantly lower for Zebu cattle (4.0-29.9%) than for British (64.9-72.6%) or Zebu-British (48.1-78.7%) cattle.

Animals↗
PubMed1989

Female mediation of feeding time on cattle in adult lone star ticks (Acari: Ixodidae).

The extended feeding time response on cattle of adult lone star ticks, Amblyomma americanum (L.), during November through December is facultative and is mediated by the female. Mean feeding time (11.8 d) in female ticks taken from the field and held at 14:10 (L:D) photoperiod and 25 degrees C for greater than or equal to 15 d was significantly shorter (P = 0.05) than for females taken directly from the field and fed on cattle (14.6 d). Mean feeding times of females from the field paired to males from the field, males from the field held for 30 d at 14:10 (L:D) and 10 degrees C, or males from the field held for 30 d at 14:10 (L:D) and 25 degrees C were not significantly different (15.7, 16.3, and 16.2 d, respectively). When males from the field were paired with females from the field that had been held at 14:10 (L:D) and 10 degrees C or 14:10 (L:D) and 25 degrees C for 30 d, mean feeding time of the females was significantly longer (17.2 d) or shorter (14.0 d), respectively, than for all other groups.

Animals↗