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Biomedical subjects

P Reiter

Publications and source records attributed to P Reiter.

At least 55 records · Page 3Linked to original sources
PubMed1994

Dengue severity throughout seasonal changes in incidence in Puerto Rico, 1989-1992. The Puerto Rico Association of Epidemiologists.

To determine whether the proportion of severe dengue cases increased with the yearly seasonal increase in dengue incidence, we examined reports of disease symptoms in case surveillance data and laboratory testing results in Puerto Rico from January 1989 to July 1992. A computer algorithm was designed to identify severe cases, i.e., those that fulfilled three or all four of the World Health Organization criteria for dengue hemorrhagic fever (DHF). A monthly severity index (SI) was defined as the ratio of severe cases to laboratory-positive and indeterminate (all non-negative) cases for each month, while a more restrictive severity rate (SR) was defined as the ratio of severe laboratory-positive cases to the total number of laboratory-positive cases for each month. Monthly SI and SR were compared in two ways: within an epidemic cycle, and month-by-month. Linear regression analysis was performed over the monthly averages of the SI and SR. For a month-by-month examination of SI and SR, we examined the 43-month sequence by means of a linear model with autocorrelated disturbances. We found no statistically significant or cyclical change in the proportion of severe cases from month to month in this period. Our conclusions differ from the observations during the Cuban DHF epidemic of 1981, in which case severity was shown to increase markedly as the epidemic progressed; they agree with the conclusions of most previous studies in that dengue severity does not change significantly throughout a period of increased incidence.

Algorithms↗
PubMed1993

Detection of multiple blood feeding in Aedes aegypti (Diptera: Culicidae) during a single gonotrophic cycle using a histologic technique.

We evaluated a histologic technique for its usefulness in detecting multiple blood feeding by Aedes aegypti (L.) in a single gonotrophic cycle. To standardize the procedure, we carried out a laboratory study in which 166 mosquitoes imbibed two blood meals at known intervals. Eighty percent (78/98) of the multiple meals were detected when the interval between meals was from 1 to < to = 24 h and the time from the second meal to fixation ranged from 0 to 12 hr. At intervals outside this range, only 34% (23/68) of the multiple meals were detected. Overall, 61% (101/166) of the double meals were detected. Examination of 96 engorged Ae. aegypti collected by aspiration from inside houses in San Juan, Puerto Rico, indicated that 50% had imbibed multiple meals. Most wild-caught mosquitoes took their last meal the day before capture, and most multiple feeders fed twice on consecutive days. A dark line of digested blood, or heme, around the first meal and a physical separation between meals were the most useful histologic parameters for detecting multiple feeding in wild Ae. aegypti. An association of multiple feeding with advanced stages of oocyte development suggests that, at the time of collection, most Ae. aegypti from the study site had fed twice in each gonotrophic cycle. We conclude that, although it is labor intensive, histologic examination is an appropriate technique for a longitudinal, community-wide survey of multiple feeding by Ae. aegypti.

Aedes↗
PubMed1992

A model of the transmission of dengue fever with an evaluation of the impact of ultra-low volume (ULV) insecticide applications on dengue epidemics.

We have developed a deterministic susceptible, exposed, infectious, resistant or removed (SEIR) model of dengue fever transmission that enables us to explore the behavior of an epidemic, and to experiment with vector control practices. Populations of both host and vector are divided into compartments representing disease status (susceptible, exposed, infectious, and, for humans, resistant), and the flow between compartments is described by differential equations. Examination of the equilibrium points leads to a formulation of the basic reproduction rate (Z0) of the disease. With a base set of parameters, Z0 = 1.9 and the model realistically reproduces epidemic transmission in an immunologically naive population. Control of adult mosquitoes by ultra-low volume (ULV) aerosols is simulated by an abrupt decrease in vector densities, followed by gradual recovery of the vector population. The model indicates that ULV has little impact on disease incidence, even when multiple applications are made, although the peak of the epidemic may be delayed. Decreasing the carrying capacity of the environment for mosquitoes, and thus the basic reproduction rate of the disease, by source reduction or other means, is more effective in reducing transmission.

Animals↗
PubMed1991

Enhancement of the CDC ovitrap with hay infusions for daily monitoring of Aedes aegypti populations.

An ovitrap containing hay infusion and a second ovitrap adjacent to it containing a 10% dilution of the infusion in tap water together yielded 8 times more Aedes aegypti eggs than single CDC ovitraps containing tap water. These "enhanced pairs" were significantly more attractive than pairs with other combinations of infusion, water or methyl propionate, and have proven useful for daily monitoring of Ae. aegypti populations. Our results shed light on the oviposition behavior of Ae. aegypti in the field.

Aedes↗
PubMed1990

Apparent influence of the stage of blood meal digestion on the efficacy of ground applied ULV aerosols for the control of urban Culex mosquitoes. I. Field evidence.

The impact of ULV resmethrin on urban Culex mosquitoes was evaluated in 4 field trials by monitoring daily oviposition rate. A well-defined oscillation of effect, with a period corresponding to the duration of the gonotrophic cycle, was observed. We postulate that this oscillation arises from changes in susceptibility following blood feeding and/or behavioral factors. The data indicate that a single treatment with ULV may be inadequate for the effective control of vector mosquitoes.

Aerosols↗
PubMed1990

Apparent influence of the stage of blood meal digestion on the efficacy of ground applied ULV aerosols for the control of urban Culex mosquitoes. II. Laboratory evidence.

The susceptibility of adult Culex pipiens s.l., Culiseta melanura and Aedes aegypti to insecticide aerosols in wind tunnel exposures varied with time, depending on the stage of blood meal digestion. Greater than 2-fold differences were observed in the concentrations of malathion and synergized resmethrin required to kill test mosquitoes, depending on whether they had been given a blood meal and, if they had, the length of time following the blood meal. The period of lowest susceptibility varied from 24 h after feeding in Ae. aegypti to 72 h in Cs. melanura. The greatest variability occurred during the period when undigested blood was present. Data from tests with a malathion-tolerant strain of Cx. pipiens s.l. suggested little change in susceptibility regardless of blood feeding and the associated weight changes that occur from ingestion of blood.

Aedes↗
PubMed1990

Apparent influence of the stage of blood meal digestion on the efficacy of ground applied ULV aerosols for the control of urban Culex mosquitoes. III. Results of a computer simulation.

When posttreatment response to ultra low volume (ULV) application of insecticide has been followed for periods approaching a week, a damped oscillation in oviposition rates is observed, probably because females who have been recently blood-fed are more resistant to insecticides than their unfed siblings. We describe a simple model (ULVSIM) that incorporates physiologic changes in insecticide susceptibility and accounts for much of our field data. The model follows 30 cohorts over 30 days following insecticidal treatment. Multiple treatments or short-term residual activity can be evaluated. The model predicts that oviposition will follow a pattern of damped oscillations after an adulticidal treatment. The model gave a good fit to oviposition data obtained in 2 field trials of resmethrin for 7 to 9 days after treatment. It can be used to evaluate the effect of single and multiple treatments on the total female Culex population and on numbers of infected females surviving for different periods following an infective blood meal.

Aerosols↗
PubMed1988

Importation of Aedes albopictus and other exotic mosquito species into the United States in used tires from Asia.

Between May 18 and December 4, 1986, 79 seagoing containers and their contents of 22,051 used tires were inspected for adult mosquitoes as well as eggs and larvae. Of the total inspected, 5,507 tires (25%) contained significant amounts of water. No adults or eggs were found. Fifteen tires contained mosquito larvae that were identified as Ae. albopictus, Ae. togoi, Culex pipiens complex, Tripteroides bambusa and Uranotaenia bimaculata. The infestation rate for all species was 6.8 infested tires per 10,000 tires (wet and dry) inspected. Aedes albopictus larvae were most frequently collected, occurring at a rate of 20 infested wet tires per 10,000 inspected.

Aedes↗
PubMed1987

Aedes albopictus in North America: probable introduction in used tires from northern Asia.

North American strains of Aedes albopictus, an Asian mosquito recently introduced into the Western Hemisphere, exhibit photoperiodic sensitivity and cold-hardiness characteristics similar to strains originating from temperate zone Asia. Trade statistics for used tire imports, the most likely mode of introduction, also indicate a north Asian origin. Aedes albopictus, an important vector of dengue and a potential vector of many other arboviral diseases, may therefore have the capability of infesting much of temperate North America.

Aedes↗
PubMed1987

The used tire trade: a mechanism for the worldwide dispersal of container breeding mosquitoes.

Modern transportation methods have facilitated an extensive trade in used tires at the national and international level. The history and reasons for this trade are described. Comprehensive data on United States imports and United States, Japanese, and Korean exports of used tires for the period 1978-85 reveal an unprecedented potential for the worldwide dispersal of important vector mosquitoes such as Aedes albopictus and Ae. aegypti. Other articles of commerce with similar potential may await recognition.

Animals↗
PubMed1986

Determination of chronological age in Culex pipiens s.l.

Daily survival rate is a major determinant of the vectorial capacity of mosquitoes, but current methods are difficult or lack the accuracy needed for epidemiologic models. We used daily growth bands on the thoracic apodemes to estimate age and survival of Culex pipiens s.l. from Memphis, Tennessee. Coded specimens of known age were used to evaluate the procedure's accuracy. Field-collected specimens of unknown age were also examined. We were unable to consistently determine the age of the coded, cage-reared specimens. Growth bands in cage-reared specimens were less well-defined than those in field-collected material. In its present form, the method is impractical for ecological or epidemiologic studies.

Age Factors↗
PubMed1986

Evaluation of the CDC gravid trap for the surveillance of St. Louis encephalitis vectors in Memphis, Tennessee.

Collections with CDC Gravid Mosquito Traps on 954 trap-nights from May through September 1983 are compared to 2,608 concurrent resting site collections made in the same area of Memphis, Tennessee. Gravid Traps yielded 88 times more Culex per collection and 96 times more Culex per man hour. The total Gravid Trap catch was 135,724 mosquitoes, 99% of which were either Culex pipiens or Cx. restuans, whereas these species comprised only 63% of the 6,613 mosquitoes collected from resting sites. Gravid Traps also collected significant numbers of Aedes aegypti and Ae. triseriatus. On most nights, more than 95% of mosquitoes in the Gravid Trap catch were gravid females. These results demonstrate that the trap is an effective and efficient device for collecting several important vector species. The preponderance of gravid mosquitoes should enhance the probability of encountering pathogens acquired by blood-feeding.

Animals↗
PubMed1983

Phospholipid and fatty acid composition of tetrodotoxin receptor-rich membrane fragments from Electrophorus electricus.

To study the interaction of voltage-sensitive Na+-channels with membrane lipids, the phospholipid and fatty acid composition of highly purified membrane fragments from the remarkably differentiated plasma membrane of Electrophorus electricus has been analyzed. After density gradient fractionation and carrier free electrophoresis, fractions with up to 30 pmol tetrodotoxin binding/mg protein can be obtained, which may correspond to a 50% pure preparation of the extrasynaptic part of the excitable face. Phospholipid classes and cholesterol are separated by one-dimensional thin-layer chromatography in acidic and alkaline solvent systems. The following mean molar contents are found: 40% phosphatidylcholine, 23% phosphatidylserine, 30% phosphatidylethanolamine and 7% sphingomyelin. In a series of 11 animals, significant deviations from these mean values have been observed. The fatty acid composition of the phospholipids has been determined by gas chromatography. Phosphatidylcholine contains more than 50% 16:0, and about 20% unsaturated fatty acids in the C-18 group. Compared to other plasma membrane fractions, this phospholipid is the least differentiated. By contrast, phosphatidylethanolamine and phosphatidylserine show many characteristics in different membrane fractions, especially in their unsaturated components representing more than 50%. 22:6, as the major constituent in these fractions, accounts for a quarter to a third of all fatty acids in these fractions. 18:0 is the main saturated component in these two phospholipids with abundances of typically a quarter or less of all fatty acids. Knowledge of the lipid composition of these excitable membranes may help to conserve binding and structural properties when analyzing lipid-sensitive Na+-channels in vitro. It is also useful as a guideline for systematic reconstitution studies.

Animals↗