Biomedical subjects

R K Washino

Publications and source records attributed to R K Washino.

At least 19 recordsLinked to original sources

PubMed1998

Gonotrophic cycle and survivorship of Anopheles vestitipennis (Diptera: Culicidae) in two different ecological areas of southern Mexico.

The duration of the gonotrophic cycle and survivorship of Anopheles vestitipennis Dyar & Knab was estimated in 2 malarious areas of Chiapas, Mexico: the Lacandon Forest and the Pacific Ocean Coastal Plain. Blood-engorged females held in an outdoor cage required 2.75 d for egg maturation, and 3.75 d for the duration of the gonotrophic cycle. Duration of the gonotrophic cycle also was estimated by parous-nulliparous dynamics for 20 consecutive days and autocorrelation time-series analysis, and by mark-recapture techniques. These methods depicted differences between the Lacandon Forest (3-d cycle) and the Coastal Plain (2-3 d cycles). Daily survival rates were estimated vertically and were generally higher in the Lacandon Forest (0.68) than in the Coastal Plain (0.45-0.58). The probability of mosquitoes surviving the sporogonic cycle was 10-100 times greater in the Lacandon Forest. The pregravid rate was 8.2%, and 29.3% of females with primary follicles beyond Christophers' stage III had traces of red blood in the gut. The 1st statistic indicated that 8.2% of females required > 1 blood meal for initial egg development, the 2nd statistic indicated that 29.3% of females take > 1 blood meal during a gonotrophic cycle. In summary, the enhanced vectorial role of this species is explained partially by high longevity and multiple blood-feeding habits.

Animals↗

PubMed1998

Lake Vera revisited: parity and survival rates of Anopheles punctipennis at the site of a malaria outbreak in the Sierra Nevada foothills of California.

Parity and survival rates of Anopheles punctipennis were studied at the site of a 1952 outbreak of malaria in the Sierra Nevada foothills of California with the purpose of estimating blood feeding frequency and survivorship of such populations. Anopheles punctipennis was the dominant species in landing collections conducted for 20 consecutive nights in August and September 1990. The mean parity rate of An. punctipennis was 0.82. The gonotrophic cycle was estimated to last three days based on time series analysis of the number of nulliparous and parous mosquitoes collected each day. Survivorship was estimated to be 0.79 per gonotrophic cycle and 0.92 per day. Ovarian dilatation data indicated that some females had completed eight gonotrophic cycles prior to being collected and 45% of the females completed two or more cycles. The high prevalence of multiparous individuals, high parity rate, long survivorship and a short three-day gonotrophic cycle estimate indicates that this population is long lived and has a capacity to be an efficient vector of malaria.

Animals↗

PubMed1997

Multiple blood feeding by Anopheles freeborni and Culex tarsalis (Diptera:Culicidae): spatial and temporal variation.

Multiple blood feeding in field populations of Anopheles freeborni Aitken and Culex tarsalis Coquillet was detected using a histologic technique. Examination of 333 blood engorged An. freeborni and 41 Cx. tarsalis females revealed that 13 and 10% of these females imbibed multiple blood meals, respectively. Spatial and temporal distribution of multiple blood feeding events was evaluated against the percentage of blood fed females and the abundance of female mosquitoes. The percentage of blood fed An. freeborni females was higher among those collected in pasture and riparian habitats than those collected in rice field and mixed habitats. Conversely, spatial variation of multiple blood feeding in An. freeborni was not significantly associated with rice field, pasture, riparian, or mixed habitats. The decrease of multiple blood feeding for An. freeborni through the season was correlated inversely with the increase of the abundance of adult females; but not with the percentage of blood fed females. These results confirmed that multiple blood meals in An. freeborni, and perhaps in Cx. tarsalis, are a frequent phenomenon, and that the histologic procedure is an appropriate tool for longitudinal and region-wide detection of multiple blood feeding necessary in epidemiologic studies.

Animals↗

PubMed1997

Assessment of a remote sensing-based model for predicting malaria transmission risk in villages of Chiapas, Mexico.

A blind test of two remote sensing-based models for predicting adult populations of Anopheles albimanus in villages, an indicator of malaria transmission risk, was conducted in southern Chiapas, Mexico. One model was developed using a discriminant analysis approach, while the other was based on regression analysis. The models were developed in 1992 for an area around Tapachula, Chiapas, using Landsat Thematic Mapper (TM) satellite data and geographic information system functions. Using two remotely sensed landscape elements, the discriminant model was able to successfully distinguish between villages with high and low An. albimanus abundance with an overall accuracy of 90%. To test the predictive capability of the models, multitemporal TM data were used to generate a landscape map of the Huixtla area, northwest of Tapachula, where the models were used to predict risk for 40 villages. The resulting predictions were not disclosed until the end of the test. Independently, An. albimanus abundance data were collected in the 40 randomly selected villages for which the predictions had been made. These data were subsequently used to assess the models' accuracies. The discriminant model accurately predicted 79% of the high-abundance villages and 50% of the low-abundance villages, for an overall accuracy of 70%. The regression model correctly identified seven of the 10 villages with the highest mosquito abundance. This test demonstrated that remote sensing-based models generated for one area can be used successfully in another, comparable area.

Animals↗

PubMed1997

Energetics and sugar-feeding of field-collected anopheline females.

We studied the relationship between nutritional reserves and blood-feeding and sugar-feeding of Anopheles freeborni (Diptera: Culicidae) females in the field. In particular we determined whether (1) females feed on nectar before maturing eggs and initiating host-seeking and (2) the energy reserves of host-seeking females differ from those of non-fed resting females. Twenty-three percent of host-seeking females and 94 percent of gravid females were positive for nectar sugars (containing > 20 micrograms of fructose) versus 55 percent of empty (no blood or eggs) females collected in the morning and 36 percent of empty females collected in the evening. In addition, gravid females contained significantly more calories of nectar than empty, blood-fed, or partially blood-fed females collected in the morning. When the energy reserves of host-seeking and resting females were compared, no differences were found in lipid, trehalose, or glycogen. However, empty females collected in the evening contained more glycogen than empty females collected in the morning. We conclude that gravid females frequently feed on nectar and that fructose is metabolized into glycogen during the day.

Animals↗

PubMed1996

Spatial distribution of adult mosquitoes (Diptera:Culicidae) in habitats associated with the rice agroecosystem of northern California.

The objective of this study was to determine whether abundance, blood feeding rates, and sex ratios of adult Anopheles freeborni Aitken and Culex tarsalis Coquillett were associated significantly with either rice field, pasture, riparian, or mixed habitats found within the rice culture agroecosystem of northern California. Significantly higher numbers of adult An. freeborni occurred in riparian and mixed habitats compared with rice and pasture habitats. Such a pattern was not evident for Cx. tarsalis. Riparian and pasture habitats contained significantly higher proportions of blood fed An. freeborni females than did rice and mixed habitats; however, the proportions of blood fed Cx. tarsalis females did not vary significantly among habitat types. The proportions of blood fed An. freeborni and Cx. tarsalis females in riparian habitats decreased with increasing abundance. There was no correlation between blood feeding rates and abundance for An. freeborni and Cx. tarsalis females in the other habitat types. The sex ratio of An. freeborni in pasture and riparian habitats was significantly female biased, unlike the other habitats which did not differ significantly from unity (1:1). Overall, riparian and mixed habitats contained greater numbers of adults mosquitoes; therefore, surveillance and control efforts of these mosquito species should be focused on such habitats.

Agriculture↗

PubMed1996

Genetic differences among Anopheles vestitipennis subpopulations collected using different methods in Chiapas state, southern México.

Biting activity and population genetic studies of the malaria vector Anopheles vestitipennis were conducted in southern México. Three subpopulations were collected from 2 villages; 2 subpopulations were from the same village, one on human bait and one with an animal-baited trap; the third was collected from a cattle corral in the 2nd village (280 km away SSE). The anthropophilic subpopulation had steady activity with 61% of bites occurring before midnight, significantly different from those of the 2 zoophilic subpopulations, which had 78-82% of bites before midnight and 2 biting peaks, one at 1900-2100 h and the other at 0400-0500 h. Isozyme analysis (13 enzymes) of these subpopulations indicated that differences between the 2 sympatric subpopulations (D = 0.07), collected using 2 different methods, were greater than that between the 2 allopatric ones (D = 0.03). These studies suggest the existence of 2 genetically different subpopulations of An. vestitipennis with specific host preferences.

Alleles↗

PubMed1995

Multiple blood feeding in Anopheles freeborni (Diptera: Culicidae).

The frequency of multiple blood feeding in field populations of Anopheles freeborni was determined. Fifty-six laboratory-reared mosquitoes, all known to have taken two blood meals, were used to define the limits of the histologic procedure we used. Seventy-eight percent of known double meals were detected when the interval between meals was from 1 to 24 hr, and the time from the second meal until fixation ranged from 0 to 24 hr. At intervals outside this range, 50% of multiple meals were detected. In field-collected An. freeborni, the most important histologic parameters for determination of multiple feeding were the amount of heme that developed around each meal, the peritrophic membrane, partially digested blood meals, and physical blood meal separation. Examination of 134 blood-engorged An. freeborni collected in the field showed that 9.7% had imbibed multiple blood meals. These results suggest that multiple blood meals in An. freeborni are more frequent than previously thought, perhaps with significant epidemiologic implications.

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PubMed1994

Spatial patterns of Anopheles freeborni and Culex tarsalis (Diptera: Culicidae) larvae in California rice fields.

Spatial patterns of Anopheles freeborni Aitken and Culex tarsalis Coquillett larvae were studied during summer by sampling with a standard mosquito dipper in 104 rice fields in northern California. Culex tarsalis larval abundance was highest initially, then decreased and remained low through late summer. An. freeborni larval abundance was low initially, increased steadily, and peaked in mid-August. The degree of aggregation for both species as measured using Taylor's power law and Iwao's Patchiness Regression was highest among the first instars and then decreased as the larvae aged. Seasonal peaks in the degree of aggregation were observed. Analysis of covariance showed that for Taylor's model both instar and time effects were statistically significant, with instar showing the largest effect. In comparison, all slopes resulting from Iwao's model were significantly different, indicating that this model was affected by specific combinations of instar, week, and location and, thus, was less useful in developing an area-wide sampling plan. Optimal sample size was estimated using two methods. One method calculated the number of dips needed to estimate population abundance at three fixed-precision levels. The second calculated the minimum number of dips needed to collect at least one larva. The latter requires a substantially smaller sample size and may provide an effective method for monitoring larval mosquito abundance for control purposes.

Animals↗

PubMed1994

Comparison of recapture patterns of marked and released Aedes vexans and Ae. melanimon (Diptera: Culicidae) in the Sacramento Valley of California.

Recapture patterns of Aedes vexans (Meigen) and Aedes melanimon Dyar were compared in a mark-release-recapture study conducted on the Colusa National Wildlife Refuge, Colusa County, California, from 15 August to 2 September 1988. The 2.0% recapture rate for Ae. vexans females was significantly greater than the 0.9% rate for Ae. melanimon females. Daily survivorship of 0.70 for Ae. vexans females was significantly lower than the 0.84 estimate for Ae. melanimon. The two species had different patterns of dispersal. On day 1, when the majority of marked females of both species were recaptured, the mean dispersal distance for Ae. vexans females was significantly greater than that for Ae. melanimon. The cumulative dispersal distance for Ae. vexans females decreased over the study period. In contrast, Ae. melanimon dispersal distances increased gradually over time.

Aedes↗

PubMed1994

Application of remote sensing to arthropod vector surveillance and control.

A need exists to further develop new technologies, such as remote sensing and geographic information systems analysis, for estimating arthropod vector abundance in aquatic habitats and predicting adult vector population outbreaks. A brief overview of remote sensing technology in vector surveillance and control is presented, and suggestions are made on future research opportunities in light of current and proposed remote sensing systems.

Animals↗

PubMed1994

Pilot scale production and application in wildlife ponds of Lagenidium giganteum (Oomycetes: Lagenidiales).

Lagenidium giganteum, a facultative parasite of mosquito larvae, has recently been registered by the U.S. Environmental Protection Agency for operational mosquito control. We report here the first pilot scale production of the mycelium formulation. Scale-up from 10 to 650 liters was accomplished by a proportionate increase of medium components and volume of water. Foaming of the culture medium had not been encountered previously, but was a serious problem in pilot scale production due to the very rapid growth of a large volume of L. giganteum. Addition of an antifoaming agent did not adversely affect growth, but reduced the ability of the fungus to sporulate. Despite what was effectively a 100-fold reduction in the desired application rate due to reduced sporulation, L. giganteum infected sentinel mosquito larvae and reduced field populations for more than 2 months following application.

Animals↗

PubMed1993

Short-term population dynamics of adult Aedes dorsalis (Diptera: Culicidae) in a northern California tidal marsh.

Short-term changes in the age structure and abundance of the host-seeking population of Aedes dorsalis (Meigen) females were studied in a Northern California tidal marsh by daily sampling from 25 July through 17 August 1990. The calculated numbers of nulliparous and parous females per day were used to estimate parity rates and duration of the gonotrophic cycle. The numbers of females collected per day ranged from 261 to 74,443, and daily parity rates ranged from 0 to 91%. The overall parity rate was 14%. Two peaks in nulliparous female abundance on days 7 and 12 were followed 5 d later by increases in the number of parous females, indicating that two cohorts had emerged with gonotrophic cycle lengths of approximately 5 d. This is consistent with the 5-d gonotrophic cycle length estimated using time series analysis of the same data sets. Peak host-seeking activity of nulliparous females in the two cohorts occurred 16 d after two marsh systems were flooded by monthly high tides. Survivorship was estimated to be 14% per gonotrophic cycle and 67% per day, although emigration may have caused the substantial underestimation of actual survivorship.

Aedes↗

PubMed1993

Anopheles hermsi, probable vector of malaria in New Mexico.

Samples of Anopheles freeborni s.1. were collected from areas of New Mexico where malaria had once been common and sporozoites had been isolated from this species. Specimens were identified by analysis of polytene chromosome banding patterns and by specific rDNA fragments generated through the polymerase chain reaction. All samples collected in New Mexico were identified as An. hermsi, which was the probable vector of malaria in this region during the early 20th century.

Animals↗

PubMed1992

Evidence of seasonal eggs in Anopheles punctipennis (Diptera: Culicidae).

Anopheles punctipennis (Say), collected in October from resting sites in Illinois, deposited two morphologically distinct types of egg batches. One type was similar to the seasonal "winter" egg of Anopheles walkeri Theobald, with an extensive exochorion that covered all except the tip of the egg. Laboratory rearing of isofemale lines, under two different light-dark and temperature cycles, demonstrated that both types of eggs were intraspecific variants. F1 females from all "winter" egg batches deposited only normal eggs when reared under a 12:12 (L:D) cycle and at 25 degrees C. Most An. punctipennis reared under a 8:16 (L:D) cycle with variable temperature exhibited gonotrophic dissociation or accumulated fat body.

Animals↗

PubMed1991

Effects of exogenous phospholipids on lipid composition and sporulation by three strains of Lagenidium giganteum.

The California (LGCA) and Butte Sink (LGBS) strains of the sterol auxotrophic fungus Lagenidium giganteum (Oomycetes: Lagenidiales) enter the sexual cycle on media supplemented with sterols. A third isolate of this mosquito pathogen, the North Carolina strain (LGNC), requires sterols plus phospholipids to produce oospores in vitro. Enrichment of the polar and neutral lipid fractions of the LGCA and LGBS strains with unsaturated fatty acids promoted oospore induction, and increased oospore viability. With the exception of the LGCA strain, there was no consistent relationship between phospholipid supplementation in growth media and mycelial phospholipid content.

Animals↗

PubMed1991

An assessment of the biological capacity of a Sacramento Valley population of Aedes melanimon to vector arboviruses.

Daily survivorship, duration of the gonotrophic cycle, absolute abundance and season-long relative abundance were estimated for Aedes melanimon in the Sacramento Valley of California in 1987 and 1988 using mark-release-recapture (MRR) techniques and by monitoring changes in the abundance and parity rate of the native population. One objective of these studies was to determine the extent to which A. melanimon was biologically capable of serving as a horizontal arbovirus vector. Daily survivorship was estimated to be 0.90 and 0.84 in MRR studies conducted in September 1987 and August 1988, 0.89 based on changes in the parity state and abundance of the native population in August 1988 and 0.82 using summer-long parity data in 1988. Gonotrophic cycle length (GCL) was estimated to be five days in three studies. Aedes melanimon densities were estimated to be approximately 1,000,000 and 15,000 females per hectare in September 1987 and August 1988 respectively. Parous A. melanimon females were collected on each sampling occasion from April to November 1988, suggesting that A. melanimon maintained a continuous presence in the study area throughout the summer. The results of these studies suggest that A. melanimon has the potential to be an efficient horizontal vector of western equine encephalomyelitis (WEE), based on high adult survivorship, short GCL, high abundance and a continuous presence across the summer. This supports the concept of a WEE transmission cycle in the Sacramento Valley involving Ae. melanimon as an important vector. Aedes melanimon also can be an efficient horizontal vector of California encephalitis virus (CE), though the importance of horizontal transmission to the maintenance of CE virus is unclear.

Aedes↗

PubMed1991

Diagnostic characterization of Anopheles freeborni and An. hermsi by hybrid crosses, frequencies of polytene X chromosomes and rDNA restriction enzyme fragments.

A polytene chromosome analysis was prepared from Anopheles freeborni collected from 25 locations in north and central California, and parts of Washington and Oregon. The X chromosome banding pattern, thought previously to be specific to An. hermsi, was common in mosquitoes collected from foothill regions in California, and in all samples from Washington and Oregon. At some of these locations, many mosquitoes had heterokaryotypes for the inversion that distinguishes the X chromosome of An. freeborni from that of An. hermsi. Use of rDNA restriction site analysis, and the results from crossing of different strains bearing either type of X chromosome, showed that An. hermsi does not have a unique or diagnostic X chromosome. Anopheles hermsi was collected in San Mateo County, CA, which is now the northernmost known limit of this species. Crossing studies, or the examination of rDNA restriction enzyme profiles, are presently the only means of identifying An. hermsi.

Animals↗