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Biomedical subjects

S A Ritchie

Publications and source records attributed to S A Ritchie.

At least 55 records · Page 3Linked to original sources
PubMed1997

Acute and sublethal effects of (S)-methoprene on some Australian mosquitoes.

Laboratory bioassays were used to determine the efficacy of (S)-methoprene against 7 species of Australian mosquitoes. The 90% lethal concentration (LC90) ranged from 0.17 ppb for Aedes vigilax to 6.54 ppb for Culex sitiens. The survival of adults exposed as larvae to 2 sublethal dosages of (S)-methoprene was compared to a control group. Little effect was noted for Cx. sitiens and Culex annulirostris. However, survival of male and female Ae. vigilax was significantly reduced and appeared to be dose related. Bloodfeeding success of female Ae. vigilax was also significantly reduced.

Aedes↗
PubMed1997

Efficacy of ALTOSID pellets and granules against Aedes aegypti in ornamental bromeliads.

The tank bromeliad Billbergia pyramidalis was treated with 2 doses (0.5 and 2 g) of ALTOSID Granules or Pellets for the control of Aedes aegypti L. Emergence inhibition (EI) for all mosquito pupae (including natural populations) in the center wells and leaf axils was > 90% for at least 6 and 12 months for both doses of granules and pellets, respectively. No significant difference in %EI was found between center wells and leaf axils.

Aedes↗
PubMed1996

An outbreak of Japanese encephalitis in the Torres Strait, Australia, 1995.

OBJECTIVES: To determine the distribution of virus infection during an outbreak of Japanese encephalitis (JE) in the Torres Strait, and to describe the environmental factors facilitating the outbreak. DESIGN: Human and porcine serological surveys for JE virus activity throughout the Torres Strait, and mosquito and household surveys on the island of Badu. SETTING: The island of Badu (where the clinical cases occurred) and the other islands of the Torres Strait, Australia, during April-May 1995. RESULTS: The serological surveys identified recent JE virus infection among residents or domestic pigs on at least nine outer Torres Strait islands. A JE virus, confirmed by nucleotide sequencing, was isolated from two asymptomatic Badu residents. Virus isolations and mosquito surveys implicated Culex annulirostris as the major vector involved in the outbreak. There was prolific Cx. annulirostris breeding in a variety of water bodies close to and within the Badu community. Over half (53%) of the households kept pigs in pens, and many (63%) of the pigpens were situated near standing water; in 56% of these "wet" pigpens Cx. annulirostris was breeding. CONCLUSIONS: There was evidence of widespread JE virus activity throughout the outer islands of the Torres Strait. We suggest that migratory birds and/or wind-blown mosquitoes could have imported the virus into the Torres Strait from a focus of viral activity, possibly in Papua New Guinea, thereby initiating the outbreak. A combination of environmental factors, with large numbers of domestic pigs in close proximity to human dwellings and mosquito breeding sites, undoubtedly facilitated the outbreak on Badu.

Adult↗
PubMed1994

Response of biting midges (Diptera: Ceratopogonidae) to carbon dioxide, octenol, and light in southeastern Queensland, Australia.

The effect of 1-octen-3-ol (octenol) on catches of estuarine biting midges in encephalitis vector surveillance (EVS) traps was examined in southeastern Queensland. Octenol by itself was not attractive but appeared to act as a synergist with CO2 to increase catches of most species. For four of six species tested, a medium (about 6 mg/h) release rate of octenol captured the most individuals. Addition of light also increased the catch size of most species. Octenol in combination with CO2 could be used to enhance biting midge catch size, improving the sensitivity of surveillance for midges and the pathogens they vector.

Animals↗
PubMed1994

Spatial stability of Aedes vigilax (Diptera: Culicidae) eggshells in southeastern Queensland salt marshes.

Sampling was done to examine whether eggshells of the saltmarsh mosquito, Aedes vigilax (Skuse), remained near the oviposition site or were dispersed by tidal flow. Few eggshells were found in the water column during tidal floodings or accumulated in the basins of small ponds when compared with pond banks, which is the oviposition site of A. vigilax. These data indicated that relatively few eggshells were flushed by rain or tides and that eggshell sampling can be used to pinpoint oviposition sites and, potentially, to focus larval control efforts within a salt marsh.

Aedes↗
PubMed1994

Differential responses of Aedes and Culex mosquitoes to octenol or light in combination with carbon dioxide in Queensland, Australia.

Field studies were conducted with EVS (encephalitis vector surveillance) traps in south-eastern Queensland, Australia, to determine the relative response rates of mosquitoes to three levels (0.1, 4.5 and 30 mg/h) of 1-octen-3-ol (octenol) in combination with a standard bait of 2200 g carbon dioxide (CO2), compared with CO2 alone or CO2 with light from a 6V incandescent bulb. Compared to CO2 alone, Aedes vigilax collections increased significantly when CO2 was supplemented by all three octenol emission levels, but not by the addition of light. Furthermore, the 4.5 and 30 mg/h release rate of octenol gave a significant increase in numbers of Ae.vigilax relative to that from CO2+light. In contrast, collections of Culex annulirostris and Culex sitiens were not enhanced significantly by either the addition of light or octenol at all three levels. Fewer Cx sitiens were collected with octenol released at 4.5 mg/h in comparison to CO2 alone. These differential sampling rates should be taken into account when using EVS traps.

Aedes↗
PubMed1994

Do fish repel oviposition by Aedes taeniorhynchus?

We tested the hypothesis that fish indirectly control mosquitoes by repelling oviposition. Aedes taeniorhynchus oviposition in mangrove forests, natural pools, and excavated pools with different concentrations of fish was compared. Oviposition in adjacent mangrove forests was concentrated in the site with the lowest fish density. In 3 mangrove forests, egg populations from pool banks were significantly (P < 0.001) lower for pools with fish than for fishless pools, with an overall mean +/- SD of 1.6 +/- 5.7 and 20.0 +/- 34.8 eggs/sample, respectively. At one pool, egg densities increased significantly (P < 0.001) from 0.36 to 5.00 eggs/sample after drying killed fish. In excavated pools, oviposition was significantly (P < 0.001) affected by fish. These data indicate that Ae. taeniorhynchus avoids ovipositing in sites with high concentrations of fish and suggest that the response is fish-mediated. This behavior may help to explain the migratory habits and population dynamics of Ae. taeniorhynchus.

Aedes↗
PubMed1993

Response of mosquitoes to carbon dioxide and 1-octen-3-ol in southeast Queensland, Australia.

Encephalitis vector surveillance (EVS) traps were used to study the attractant effect of CO2 and 1-octen-3-ol (octenol) on mosquitoes at 2 different locations in southeast Queensland. Octenol alone was only slightly attractive for Aedes vigilax. There was a significant increase in the numbers of Ae. vigilax and Aedes funereus caught when octenol was added to CO2, although catches of Culex annulirostris and Culex sitiens did not change significantly. The size and age compositions of Ae. vigilax attracted by CO2 and by octenol were comparable. These data suggest that octenol should be considered as a supplement to CO2-baited EVS traps for mosquito-based arbovirus surveillance in southeast Queensland.

Aedes↗
PubMed1993

Application of radar rainfall estimates for surveillance of Aedes taeniorhynchus larvae.

A preliminary investigation of land-based radar rainfall estimates for surveillance of Aedes taeniorhynchus larvae was conducted from January 1 to May 21, 1991 in Collier County, FL. Rainfall estimates from the National Weather Service RADAP II radar system, supplemented with tide gauge data, served as criteria for larval inspection. Rain, rain+tide and tide, respectively, triggered 48, 26 and 26% of the 14 proposed inspection trips. This system detected 7/8 larval broods found by Collier Mosquito Control District surveillance; the only brood not detected consisted of stragglers from an earlier brood exposed to cool weather and methoprene. A QUICKBASIC program that extracts Cartesian coordinates and rainfall estimates from RADAP II B-SCAN data was developed.

Aedes↗
PubMed1992

Eggshells as an index of aedine mosquito production. 1: Distribution, movement and sampling of Aedes taeniorhynchus eggshells.

The distribution of Aedes taeniorhynchus eggshells in Florida mangrove basin forests was determined and used to design a sampling plan. Eggshells were found in 10/11 sites (91%), with a mean +/- SE density of 1.45 +/- 0.75/cc; density did not change significantly year to year. Highest densities were located on the sloping banks of hummocks, ponds and potholes. Eggshells were less clumped in distribution than eggs and larvae and thus required a smaller sample size for a given precision level. While eggshells were flushed from compact soil that was subject to runoff during heavy rain, mangrove peat, the dominant soil of eggshell-bearing sites, was less dense and had little runoff or eggshell flushing. We suggest that eggshell surveys could be used to identify Ae. taeniorhynchus oviposition sites and oviposition patterns.

Aedes↗
PubMed1992

Eggshells as an index of aedine mosquito production. 2: Relationship of Aedes taeniorhynchus eggshell density to larval production.

To test if eggshell density could be used as an index of aedine mosquito production, we compared eggshell density with the larval production of Aedes taeniorhynchus in Florida mangrove basin forests. Quantitative (n = 7) and categorical (n = 34) estimates of annual larval production were regressed against the number of eggshells per cc of soil. Significant regressions were obtained in both instances. Larval production was concentrated in zones with the highest eggshell density. We suggest that eggshell density and distribution can be used to identify oviposition sites and the sequence of larval appearance.

Aedes↗
PubMed1992

The killifish Rivulus marmoratus: a potential biocontrol agent for Aedes taeniorhynchus and brackish water Culex.

In the laboratory, newly hatched fry of Rivulus marmoratus were effective predators on 1st-instar Aedes taeniorhynchus. Adult fish consumed 4th-instar Ae. taeniorhynchus and egg rafts of Culex quinquefasciatus at a rate increasing with standard length of the fish. Predation of Rivulus marmoratus on Ae. taeniorhynchus larvae in the field was documented by observing the passage of larval/pupal remains through the gut. Laboratory reared fish released at known Ae. taeniorhynchus breeding sites survived over 1.5 years, but did not reproduce.

Aedes↗
PubMed1991

Distribution and sampling of Aedes taeniorhynchus (Diptera: Culicidae) eggs in a Florida mangrove forest.

The distribution of Aedes taeniorhynchus (Wiedemann) eggs in a Florida mangrove basin forest was quantified and used to design a sampling plan. Eggs were found in detritus-rich soil with the highest densities in a band at elevations 0.1-0.2 m above the water line. Dispersion indices (k and Taylor's b) indicated that the eggs were aggregated; 14 of 16 populations tested fit the negative binomial distribution. A fixed-size sampling plan using systematic sampling was designed from these data.

Aedes↗
PubMed1991

Aedes taeniorhynchus (Diptera: Culicidae) oviposition patterns in a Florida mangrove forest.

The association of Aedes taeniorhynchus eggs and several variables was studied in a Florida mangrove forest. Eggs were limited to stands of red mangrove (Rhizophora mangle L.) that were embedded within a black mangrove (Avicennia germinans L.) forest. The occurrence of eggs was related significantly to elevation and the amount of detritus. Field and laboratory studies indicated that grazing on black mangrove detritus by the snail Melampus coffeus L. may have limited detritus accumulation and soil organic content, thus restricting mosquito oviposition to the red mangrove stands. Eggshells were concentrated in the same habitat as eggs, suggesting that eggshells may be used to identify oviposition patterns.

Aedes↗
PubMed1991

Collection and separation of Aedes taeniorhynchus eggshells from mangrove soil.

Two methods to separate eggshells of Aedes taeniorhynchus from mangrove soil were compared. Selective sieving, using nested sieves with 0.185 and 0.170-mm screen openings, and water flotation both removed over 99% of the soil. However, water flotation recovered a significantly greater percentage of eggshells (62% vs. 34%). There was no significant difference in the recovery rate of viable eggs and new and old eggshells using water flotation.

Aedes↗
PubMed1990

The acute effects of alcohol on the blood pressure of young, normotensive men.

Alcohol's acute effects on arterial blood pressure (BP) were examined. To separate the effects of alcohol on BP from those of fluid volume and expectancy, normotensive men were divided into three groups. The alcohol group received 1.0 ml of absolute alcohol/kg of body weight. The expectancy group expected alcohol but received only tonic. The control group expected and received only tonic. With age as a covariate, significant changes in systolic BP were found only in the alcohol group, indicating that the changes in systolic BP were not attributable to subject expectancy or volume of fluid consumed. The expectancy control groups did not differ from each other. A significant quadratic trend was found for systolic BP in the alcohol group, suggesting that alcohol may have an acute biphasic effect on systolic BP, with an initial decrease as the alcohol is ingested followed by an increase toward the basal level during detoxication. No significant effects were found for diastolic BP.

Adolescent↗
PubMed1990

A simulation model of water depth in mangrove basin forests.

The construction and validation of a model simulating the water depth within mangrove basin forests is described. Rainfall, water table, water depth and tide data collected from a red mangrove basin forest on Marco Island, FL, was used to estimate model parameters. These included the basin spillover height, evapotranspiration-infiltration rate and the functional relationship of water depth change to rainfall, tide and basin spillover. The model was constructed with LOTUS 123 and calibrated from staff gauge water depth records. The model proved accurate and adaptable. Water depths from the model and staff gauge were correlated highly (r = 0.98). Data from an adjacent black mangrove forest featuring complex wet-dry cycling were used to modify the model. After calibration, the model provided an accurate record of water depths at the site (r = 0.89). This model will provide water depths used in a model of Aedes taeniorhynchus population dynamics.

Aedes↗