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Biomedical subjects

G A Curtis

Publications and source records attributed to G A Curtis.

11 recordsLinked to original sources
PubMed1999

Blood feeding and oviposition by Culex nigripalpus (Diptera: Culicidae) before, during, and after a widespread St. Louis encephalitis virus epidemic in Florida.

A widespread epidemic of St. Louis encephalitis (SLE) virus was reported from central Florida from late July through December 1990 with 226 clinical cases and 11 deaths in humans. The abundance of blood-fed and gravid Culex nigripalpus Theobald females, the vector of SLE in Florida, was monitored at a resting site in Indian River County, FL, for the 3 yr before the epidemic, the epidemic year, and for 1 yr following the epidemic. Each study year was divided into four 3-mo periods that depict the subtropical SLE transmission cycle; a January-March maintenance phase, an April-June amplification phase, a July-September early transmission phase, and an October-December late transmission phase. The abundance of blood-fed and gravid females was significantly greater during the amplification, early transmission, and late transmission phases of the 1990 SLE epidemic when compared with the 3 pre-epidemic years. Throughout the study, Cx. nigripalpus blood feeding and oviposition was driven by epic (> 50 mm) rainfall events. The abundance of gravid females decreased, whereas the number of blood-fed females increased following heavy rainfalls. Epizootic and epidemic transmission of SLE to sentinel chickens and humans in Indian River County was greatest immediately following heavy rainfalls that synchronized Cx. nigripalpus oviposition and blood feeding.

Animals↗
PubMed1996

Influence of ground ULV droplet spectra on adulticide efficacy for Aedes taeniorhynchus.

A series of 76 field trials in a vegetated habitat with caged adult Aedes taeniorhyncus mosquitoes determined that ground ultra-low volume treatment efficiency was significantly influenced by droplet size. Small droplets (7-microns volume median diameter [VMD]) produced the lowest mosquito mortality at all test distances (100-500 ft.). A VMD of 26 microns was effective at 100-300 ft., but was not effectual at 400-500 ft. Droplets in the 15-microns range were the most effective overall, at the distances evaluated.

Aedes↗
PubMed1993

Annual emergence patterns of Culex nigripalpus females before, during and after a widespread St. Louis encephalitis epidemic in south Florida.

Resting Culex nigripalpus females were collected from the same site at least 3 times a week from January 1986 through December 1991. Newly emerged mosquitoes were used to monitor annual emergence patterns that were rainfall driven. Four of the years, 1986-89, preceded the 1990 St. Louis encephalitis (SLE) epidemic in south Florida. The pre-epidemic period averaged 4 emergences per year, with most occurring during July and August. The emergence patterns observed during the epidemic year were unusual in their early start in May and June and in the total number (11) observed. Adult mosquito emergences in 1991 were similar to those in 1990, with an early start and a total of 14 observed, yet no SLE transmission was recorded in Indian River County during 1991. A time series analysis of the 6-year data set showed a significant cross-correlation between the emergence of Cx. nigripalpus females and heavy (> 50 mm) rains. A significant adult emergence occurred 5-8 days and 12-15 days following a heavy rainfall event.

Animals↗
PubMed1990

Rainfall-directed oviposition behavior of Culex nigripalpus (Diptera: Culicidae) and its influence on St. Louis encephalitis virus transmission in Indian River County, Florida.

Resting Culex nigripalpus Theobald were collected with a ground aspirator three times a week in Indian River County, Fla., from January 1985 through December 1987. The number of green (newly emerged), empty, blood-fed, and gravid females in each collection was counted; up to 100 empty females were dissected to estimate the abundance of empty, parous females in the population. In general, this species was uncommon during the dry season from January through June but increased during the wet season in July and remained abundant through early winter. During the wet season, green, parous, and gravid females were periodically abundant. Time series analysis demonstrated that green and parous mosquitoes were positively associated through time and that gravid females were associated negatively with daily rainfall. The strongest correlations were recorded in 1985, a year during which St. Louis encephalitis virus was detected with increased frequency in Indian River County. Laboratory experiments in a large outdoor wind tunnel confirmed that high relative humidity was important for the initiation and successful completion of oviposition by gravid, field-collected Cx. nigripalpus mosquitoes. Thus, intermittent rainfall during autumn may serve to delay oviposition, increase longevity, synchronize blood feeding, and enhance transmission of St. Louis encephalitis virus by infected mosquitoes in the field.

Animals↗
PubMed1990

Evaluation of hand applied naled thermal fog for Wyeomyia control.

Tests on the effect of hand applied naled thermal fog, both as a single treatment on one day/week and a single treatment on 3 successive days, did not control Wyeomyia vanduzeei and Wy. mitchellii. Five-min landing/biting counts in a native oak/palm woodland demonstrated that single applications produced an average landing rate decrease of 13%. Treatments 3 days in succession did not suppress the landing rate.

Animals↗
PubMed1990

Elf for electronic linear flow control of variable speed ground ULV applications.

The Elf device delivered the appropriate ground ULV rate at variable road speeds ranging from 4 to 21 mph (6 to 32 kph), and shut off automatically at higher and lower speeds. The system is designed to be compatible with vehicles equipped with digital as well as standard speedometers and can be calibrated at any speed within its operating range. Although not used in these studies, Elf has a distance calibration feature designed to enhance the accuracy of the transducer and thus to yield greater flow precision than could be achieved with the transducer alone.

Automobiles↗
PubMed1988

Evaluation of equipment modifications and dosage rates of ground ULV applications of naled against Aedes taeniorhynchus in a Florida citrus grove.

Efficiency of ground-applied naled (Dibrom 14), based on caged mosquito bioassays in a moderately vegetated coastal southeastern Florida citrus grove, proved to be significantly associated with downwind distance. However, association analysis between wind speed, temperature or relative humidity revealed no correlation between these meteorological factors and mosquito mortality. Tests conducted with 3 of the commonly used ULV machines demonstrated no significant differences in efficiency. Equipment modifications to simulate aerial application by elevating the spray release point proved ineffective. Increasing the dosage of naled to 3 times the labeled rate for ground treatment resulted in greater than 95% mortality.

Aedes↗
PubMed1985

Habitat selection strategies of mosquitoes inhabiting citrus irrigation furrows.

The mosquitoes Aedes vexans, Psorophora columbiae and Psorophora howardii have recently extended their habitat distribution into citrus irrigation furrows in coastal southeastern Florida. Oviposition site selection was examined by correlating species abundances with water depths due to rainfall or flood irrigation. Psorophora columbiae and Ps. howardii oviposited low in furrows, shared similar distributional relationships to water depths and were hatched by rainfall or irrigation. Aedes vexans oviposted higher in the citrus furrow, showed a different relationship to water depth and were hatched only by flood irrigation.

Agriculture↗
PubMed1983

Roles of stress and adaptation in the elicitation of face-immersion bradycardia.

Thirteen young healthy human volunteers immersed their faces in warm or cold water on one day while breathing through a snorkel and on another day while breath holding. The magnitude of the elicited bradycardia was most prominently due to water temperature, with apnea playing a less important role. Perceived stress could affect the magnitude of the response, but it was less important than the other variables. Thus statistically significant nonparametric correlations were found for the group but not for most individuals between a scoring technique that assessed perceived stress and heart rate. In contrast to animals, these data indicate that bradycardia may be reliably elicited in humans by face immersion in cold water and that stress is neither necessary nor sufficient to produce this phenomenon. Adaptation did not seem to play a role in the development of this physiological response.

Adaptation, Physiological↗
PubMed1977

The influence of bladder fullness on upper urinary tract dimensions and renal excretory function.

Nearly full bladders (375 ml.) produced significantly greater dimensions of the renal calices, pelves and ureters on excretory urograms compared to nearly empty bladders. These dimensions were frequently to the point of being considered pathological dilatations. On planimetry the urographic areas of the pelviocaliceal systems decreased by 43 per cent on the right side and 38 per cent on the left side when the nearly full bladder was compared to the nearly empty bladder in 10 patients. Renal excretory function also was affected by nearly full bladders. Urea clearances after 1 hour were 24 per cent lower and creatinine clearances were 9 per cent lower when starting with a nearly full bladder as compared to starting with an empty bladder. The implications of these findings are of potential significance with respect to 1) interpretation of excretory urograms and 2) chronic urine holding in patients with recurrent urinary tract infections, impaired renal function and/or urolithiasis.

Adolescent↗