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Biomedical subjects

J F Day

Publications and source records attributed to J F Day.

At least 19 recordsLinked to original sources
PubMed1995

Antibodies to St. Louis encephalitis virus in armadillos from southern Florida.

From January 1990 through March 1991, 189 armadillos (Dasypus novemcinctus) were collected from Brevard and Glades Counties in southern Florida (USA). The sera were analyzed for hemagglutination-inhibition (HAI) antibodies against St. Louis encephalitis (SLE) and eastern equine encephalomyelitis (EEE) viruses. None of the armadillos had detectable HAI antibody to EEE virus, but 59 (31%) had antibodies against SLE virus. Sera from 31 of the HAI-positive armadillos contained significant levels of neutralizing (NT) antibody to SLE virus. Armadillos captured during the 1990 SLE human epidemic in south Florida had a greater prevalence of HAI and NT antibody to SLE virus than did animals captured before the start of the epidemic. This is evidence that armadillos were fed on by mosquitoes infected with SLE virus. We propose that armadillos may be involved in the SLE amplification and transmission cycles in Florida.

Animals↗
PubMed1995

Effect of wind velocity on suction trap catches of some Florida mosquitoes.

The correlations between wind velocity and suction trap catches of mosquitoes when taken at 15-min intervals during the night were studied at 2 locations. Although normal mosquito flight speeds are approximately 1 m/sec, trap catches were reduced about 50% by winds of 0.5 m/sec and 75% at 1.0 m/sec. Trap catches were inversely related to winds of all velocities and even the lightest winds reduced trap catches. No evidence was found for a threshold below which wind velocity had no effect.

Animals↗
PubMed1994

Reproductive fitness and survivorship of Aedes aegypti (Diptera: Culicidae) maintained on blood, with field observations from Thailand.

Daily survivorship and fecundity of Aedes aegypti mosquitoes were monitored for cohorts provided with five nutritional treatments: water, 2% sucrose, blood from a live chicken plus water, blood plus 2% sucrose, and blood alone. The median mortality time (LT50) for these females was 6, 54, 16, 12, and 29 d, respectively. There was no significant difference in the number of eggs laid by females in any of the treatments containing a host. Females maintained on blood alone laid as many or more eggs during their lifetime as females with access to sugar who had a greater life expectancy. Males maintained on sugar alone survived significantly longer than those in any of the other treatments. Large- and small-bodied, sugar-starved Ae. aegypti females that were marked, released, and recaptured in a Thai village survived as well as the replicate cohorts that received sugar or sugar plus blood during the 36 +/- 12 h period from emergence until their release. These results indicate that Ae. aegypti females live longer in the laboratory if they are provided a source of carbohydrate, but the increased survival associated with sugar feeding does not increase reproductive success.

Aedes↗
PubMed1994

Ultrastructure of the eggs of seven flea species (Siphonaptera).

Eggs of seven flea species representing five families, Ctenocephalides felis (Bouché) (Pulicidae), Orchopeas leucopus (Baker) and Aetheca wagneri (Baker) (Ceratophyllidae), Conorhinopsylla stanfordi Stewart and Epitedia faceta (Rothschild) (Hystrichopsyllidae), Sternopsylla distincta texana (C. Fox) (Ischnopsyllidae), and Craneopsylla minerva (Rothschild) (Stephanocircidae), were examined with a scanning electron microscope and are described from the resulting micrographs. In the Pulicidae and Ceratophyllidae the individual outer chorionic cells are not visible; the egg surfaces are covered uniformly with small, nodular tubercles. In contrast, the Hystrichopsyllidae and Ischnopsyllidae have a prominent, raised reticulum, very heavily constructed in the latter, delineating the chorionic cells. The single representative of the Stephanocircidae has only a faintly embossed chorionic reticulum. All of the species examined except E. faceta and C. minerva (both with a single micropylar opening) have multiple micropyles at the posterior end. C. felis, O. leucopus, A. wagneri, and C. stanfordi also have multiple aeropyles at the anterior end (these are lacking in S. d. texana). Lateral aeropyles, consisting of small groups of pores often associated with small mounds in the chorion, are present (maximum of two seen on any one egg) in all species except E. faceta, C. stanfordi, and C. minerva.

Animals↗
PubMed1994

Vector control by removal trapping.

The classic approach to vector control where large tracts of land are treated with an insecticide has many shortcomings. These include high cost, chemical resistance of target species to many of the widely used insecticides, a lack of public acceptance, and the detrimental effect of sprays on nontarget species. Removal trapping, the use of visual, auditory, and olfactory attractants to lure target species into small areas where they are killed, has recently received well-deserved attention as a possible alternative to the broadcast application of chemicals for vector control. We briefly review the histories of four successful removal trapping programs; Hippelates eye gnats in the United States, tsetse flies in Africa, Stomoxys calcitrans flies in Australia, and tabanids in the United States. We then review the future prospects of removal trapping and evaluate its potential as a viable method for vector control.

Africa↗
PubMed1993

A rapid diagnostic assay for eastern equine encephalomyelitis viral RNA.

Eastern equine encephalomyelitis virus (EEEV) has been a low-frequency, but serious human and veterinary health problem. Increased frequency of this mosquito-borne virus is anticipated as wetlands are maintained and re-established. Control of EEEV has depended on mosquito abatement in response to increasing frequency of EEEV in the environment. A coupled reverse transcription/polymerase chain reaction assay was designed to rapidly, sensitively, and specifically detect EEEV RNA. The assay successfully detected the viral RNA in a single-blind study of a set of field samples composed of either pooled mosquitoes or bird tissue. These results suggest that it would be practical to use this assay for deciding when and where to implement mosquito abatement.

Animals↗
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↗
PubMed1991

Distribution of St. Louis encephalitis viral antibody in sentinel chickens maintained in Sarasota County, Florida: 1978-1988.

Sentinel chicken flocks monitored arboviral transmission at 12 sites in Sarasota County, Fla., from 1978 through 1988. During this time, 3,452 serum samples were analyzed for hemagglutination inhibition antibody to St. Louis encephalitis virus (SLE) and eastern equine encephalomyelitis virus (EEE). Overall, 91 chickens seroconverted to SLE and three to EEE. The intensity of SLE transmission showed considerable year-to-year variation. Chickens from south-county flocks were more likely to seroconvert to SLE virus than chickens maintained at the north-county sites. The SLE seroconversion rate for midcounty sentinels was intermediate between north- and south-county sites. Chickens were caged in four habitat types: oak hammocks, slash pine-saw palmetto areas, pastures, and urban-residential areas. There was no significant difference in SLE seroconversion rates between habitats.

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

Nectar-feeding habits of Aedes taeniorhynchus.

Aedes taeniorhynchus were collected on the wing at several times during the day and night, in Indian River and Brevard County, Florida. Nonblooded females were individually analyzed for fructose and glycogen. Fructose content of mosquitoes collected early in the morning and held without food during the day diminished to approximately the same level as in mosquitoes collected late in the afternoon. However, fructose content of mosquitoes collected before sunset and held without food overnight diminished greatly, whereas that of mosquitoes collected in the morning always exceeded that of evening collections. Maximum fructose content occurred within one or 2 hours after sunset. Apparently, these mosquitoes take little or no nectar during the day, and feed soon after the onset of darkness.

Aedes↗
PubMed1989

Correlation between wing length and protein content of mosquitoes.

Wing length and protein content were compared in individual specimens of male and nonbloodfed, nongravid female mosquitoes. The following groups were tested: field-collected and colonized Aedes aegypti, field-collected Culex nigripalpus and Aedes vexans, and colonized Culex quinquefasciatus and Psorophora columbiae. The correlation coefficient varied from 0.91 in Ae. aegypti males to 0.98 in Ae. vexans females, and in each group the P value was less than 0.001. This close correlation suggests that both wing length and protein measurement are reliable expressions of size in adult mosquitoes.

Animals↗
PubMed1987

Visual ecology of biting flies.

Many of the similarities in visual ecology between the Nematocera and Brachycera and within the Cyclorrhapha may reflect the evolution of blood-feeding in these groups. In Nematocera and Brachycera, blood-feeding is thought to have evolved from predatory or nectar-feeding behavior (138). Only females feed on hosts, and association with hosts generally occurs when hosts are close to the aquatic or semiaquatic habitats of the immatures. Flies feed on nectar, make appetitive flights, disperse, or migrate prior to blood-feeding, and then oviposit in water. Many species are nocturnal or crepuscular. In Cyclorrhapha, flies are closely associated with hosts. They may have arisen from compost-feeding flies that developed a larval dependence on vertebrate-produced microhabitats. Both sexes blood-feed, and mating occurs on or near hosts. Flies generally emerge in the proximity of hosts and maintain close contact with them. These species are diurnal, and their visual systems are well developed. Comparisons between closely related blood-feeding and non-blood-feeding species may provide insight into the visual ecology of blood-feeding species. Despite the different origins of hematophagy, there appears to be a convergence of morphology and behavior that is related to ecology rather than to phylogenetic relationships. This is clearly seen in host-location strategies by tsetse and tabanids. Even within groups such as mosquitoes, species that are active at the same time of day and in the same habitat have more in common than closely related species in different habitats. For this reason, an ecological review would be more cohesive than this phylogenetic discussion. However, because of the disproportionate amount of literature on a small number of groups, the phylogenetic approach is the most practical for this subject. However, this review does point out the great need for research on the less well-studied groups and behaviors.

Animals↗
PubMed1986

Differences between the nutritional reserves of laboratory-maintained and field-collected adult mosquitoes.

Individual female mosquitoes from field populations of Aedes aegypti, Culex nigripalpus and Coquillettidia perturbans were analyzed for sugar, glycogen and lipids. Controls were maintained in the laboratory for 7 to 10 days on 2% and either 10 or 20% sucrose. Mosquitoes held in the laboratory had significantly more glycogen and lipid than field-collected mosquitoes of the same species. Laboratory mosquitoes maintained on 10 or 20% sucrose contained more sugar than did field mosquitoes. Mosquitoes of the above species were collected at field sites in January, April, July and October and nutritional reserves were determined. Seasonal differences in reserves were documented in females of all species. However, even when reserves were at their highest in field-collected mosquitoes they rarely approached the reserves in mosquitoes of the same species maintained in the laboratory on 10 or 20% sucrose. Since laboratory-maintained mosquitoes are nutritionally different from those in the field, results of laboratory studies on flight performance, host attractancy, biting, disease transmission and oviposition behavior may be biased.

Animals↗
PubMed1985

The importance of autumn rainfall and sentinel flock location to understanding the epidemiology of St. Louis encephalitis virus in Indian River County, Florida.

Culex nigripalpus adults were collected from sentinel chickens at 4 sites in Indian River Co. (IRC), Florida. Chickens located in well drained, open habitats attracted fewer Cx. nigripalpus than did those located in a moist, forested area, but the number of mosquitoes collected in the open habitats increased significantly with heavy autumn rainfall. All St. Louis encephalitis virus (SLE) seroconversions (11/674) during a 7-year period were from chickens located in open, well drained habitats. A comparison of monthly rainfall during years of known SLE activity in IRC with the 22-year average showed that virus activity was significantly associated with years in which rainfall was unusually low in either September or October. Sentinel chickens in areas with large vector populations may not be the most reliable indicators of local SLE activity and autumn rainfall in September and October may influence yearly SLE patterns in southern Florida.

Animals↗