Search PubMed⌕ Search

Biomedical subjects

B F Eldridge

Publications and source records attributed to B F Eldridge.

At least 37 records · Page 2Linked to original sources
PubMed1991

Occurrence and evolutionary significance of a California encephalitis-like virus in Aedes squamiger (Diptera: Culicidae).

More than 12,000 Aedes increpitus Dyar and 4,600 Aedes squamiger (Coquillett) were tested for the presence of arboviruses to test the hypothesis that there is a coevolutionary relationship between Aedes (Ochlerotatus) mosquitoes and California serogroup viruses. Five strains of a California encephalitis-like virus were isolated from adults reared from larvae of Ae. squamiger collected in January 1989 from a coastal salt marsh at Morro Bay, San Luis Obispo County, California. Viruses were isolated in Vero cell cultures and serotyped by cross-neutralization tests. These isolates represent the first arboviruses isolated from this species. On the basis of morphology, Aedes squamiger has been included in the Aedes stimulans group of the subgenus Ochlerotatus. Other species within the Ae. stimulans group are vectors of California (CAL) serogroup viruses elsewhere in North America. Analysis of isozyme variability supports the inclusion of Ae. squamiger in the Ae. stimulans group and suggests that coastal populations of Ae. increpitus are the closest California relatives of Ae. squamiger. Recovery of virus from Ae. squamiger reinforces the relationship between CAL serogroup viruses and Aedes (Ocherlotatus) mosquitoes. However, the failure to isolate virus from large samples of Ae. increpitus from coastal and low elevation inland habitats suggests a complex evolutionary history involving both vertical and horizontal transmission mechanisms.

Aedes↗
PubMed1991

Isolation of Jamestown Canyon virus from boreal Aedes mosquitoes from the Sierra Nevada of California.

More than 28,000 mosquitoes in four genera were collected from high elevation (greater than or equal to 1,000 m) areas of California during 1988-89 and tested for virus by plaque assay in Vero cells. Viruses were serogrouped by enzyme immunoassay and serotyped by cross-neutralization. Six strains of Jamestown Canyon virus in the California serogroup were isolated from three species of boreal Aedes in the Aedes communis group of the subgenus Ochlerotatus. All isolates were from mosquitoes collected in Alpine County at approximately 2,300 m elevation in the Sierra Nevada. These included one virus from a pool of male Aedes cataphylla collected in immature stages, which is evidence for vertical transmission; four viruses from adult female Ae. communis (sens. lat.); and one virus from adult female Aedes hexodontus. These are the first isolations of viruses from boreal Aedes mosquitoes in California and the first reported isolations of Jamestown Canyon virus from Ae. cataphylla or Ae. hexodontus.

Aedes↗
PubMed1991

Isolation of Northway serotype and other Bunyamwera serogroup bunyaviruses from California and Oregon mosquitoes, 1969-1985.

Eight previously untyped Bunyamwera serogroup bunyaviruses that had been isolated from mosquitoes collected in California and Oregon between 1969 and 1985, were identified by cross-neutralization tests. Four viruses from Anopheles freeborni and a virus from Aedes sierrensis collected in Butte County in the Central Valley of California in 1970-71 were shown to belong to the Northway serotype. The existence of a Northway serotype virus in California had been inferred from previous serologic surveys of deer and horses, but these are the first Northway serotype viruses to be identified from the contiguous United States or from An. freeborni. This is also the first isolation of any virus from Ae. sierrensis. Two viruses from Culiseta inornata collected in Umatilla County, Oregon in 1969 may represent a new serotype in the Bunyamwera serocomplex of the Bunyamwera serogroup. The name "Stanfield" is proposed for this serotype, which is closely related to the Cache Valley and Northway bunyavirus serotypes. A virus from Ae. taeniorhynchus collected in San Diego County, California in 1985 was confirmed to belong to the Main Drain serotype. Previously, Main Drain serotype viruses in California have been associated principally with Culicoides variipennis.

Aedes↗
PubMed1990

Evolutionary relationships among California serogroup viruses (Bunyaviridae) and Aedes mosquitoes (Diptera: Culicidae)

More than 100 published and four unpublished papers recording virus isolations of California (CAL) serogroup viruses from mosquitoes and other arthropods were analyzed, followed by a comparison of a contemporary classification of mosquitoes of the genus Aedes with a contemporary classification of CAL serogroup viruses. Using criteria of five or more total isolations of a given virus from a given species of mosquito, and a minimum infection rate of 1:10,000 or greater (more frequent), Aedes, and to a lesser extent Culiseta, species were found to be the arthropods most frequently involved as vectors. Such a comparison could not explain all virus-vector associations on the basis of coevolution of viruses in Aedes mosquito species, probably because of the crossing over of viruses to other mosquito species through horizontal transmission and because of deficiencies in currently available classifications. Coevolution of host-parasite systems is discussed, as are the inadequacies of contemporary taxonomic treatments of viruses and Aedes mosquitoes. The paper ends with hypothetical reconstructions of virus-mosquito relationships over time and possible routes of dispersal of California serogroup viruses to their present geographical distributions.

Aedes↗
PubMed1990

Distribution of neutralizing antibodies to California and Bunyamwera serogroup viruses in horses and rodents in California.

Neutralization tests were done on sera from 141 horses from high elevation regions of California. Antibody prevalences to Jamestown Canyon, snowshoe hare, and California encephalitis viruses in the California serogroup and Northway virus in the Bunyamwera serogroup were 55%, 43%, 18%, and 46%, respectively. In 51 horses from rural low elevation regions, seroprevalences were 31%, 35%, 35%, and 37%, respectively. Twenty-four horses from a suburban lowland area were seronegative, except for a single horse with a low titer to snowshoe hare virus. Seroprevalence to Jamestown Canyon and snowshoe hare viruses was associated with increasing age. Only 2 of 177 rodents from the Sierra Nevada had antibodies to Northway virus; none had antibodies to Jamestown Canyon or snowshoe hare viruses.

Animals↗
PubMed1990

Daily survivorship of adult Aedes communis in a high mountain environment in California.

Using mark-release-recapture methods and linear regression analysis, daily survivorship for 3 groups of Aedes communis in a high mountain environment in the Sierra Nevada of California were estimated to be 0.90, 0.91 and 0.88, respectively. Multiple recaptures of marked females were made for up to 33 days after release. Precise estimates were not made of gonotrophic cycle lengths. However, parity data, based on dissections of samples of marked and unmarked females, suggest the length of gonotrophic cycles was between 1 and 2 weeks.

Aedes↗
PubMed1989

Prevalence of neutralizing antibodies against California and Bunyamwera serogroup viruses in deer from mountainous areas of California.

Plaque reduction-serum dilution neutralization was used to evaluate the status of bunyavirus activity in deer in mountainous areas of California. Antibodies against 9 bunyaviruses were measured in 337 mule deer (Odocoileus hemionus hemionus, O. hemionus californicus, and O. hemionus inyoensis) and black-tailed deer (O. hemionus columbianus). More deer from high mountainous areas had neutralizing antibodies against Jamestown Canyon virus than did deer from low mountainous areas (23% vs. 9%; P less than 0.01). This finding is consistent with transmission by snow pool Aedes mosquitoes. Results for Jerry Slough virus were nearly identical to those for Jamestown Canyon virus, which is further evidence that these are strains of the same virus. Neutralizing antibodies against Northway virus were present in 26% of deer from high mountainous areas and 23% of deer from low mountainous areas, suggesting the involvement of a widespread vector, such as Culiseta inornata. Northway virus is not known to occur outside of Alaska and northwestern Canada. Low prevalences of antibodies were detected in deer to California encephalitis, La Crosse, and snowshoe hare viruses of the California serogroup; and Cache Valley, Lokern, and Main Drain viruses of the Bunyamwera serogroup.

Animals↗
PubMed1987

Strategies for surveillance, prevention, and control of arbovirus diseases in western North America.

Present strategies for surveillance, prevention, and control of arbovirus diseases in western North America have been developed from more than 4 decades of epidemiological research and development of mosquito control technology. Methods of prediction of outbreaks remain imprecise, although our understanding of sources of variation associated with indicators used for prediction is improving. Well organized and funded systematic mosquito abatement remains the most effective method of prevention of human cases of mosquito-borne virus disease, although emergency methods must be employed when outbreaks are imminent. The development of information management systems technology, use of recent developments of sampling theory, and research on vector competency and related areas should permit much better precision in estimates of impending outbreaks.

Animals↗
PubMed1987

Serological evidence of California serogroup virus activity in Oregon.

We wished to demonstrate evidence of the presence of California serogroup viruses in Oregon and to test for the presence of certain other arboviruses in large ungulates. Blood samples from black-tailed deer (Odocoileus hemionus columbianus), mule deer (O. hemionus hemionus), and Roosevelt elk (Cervus elaphus roosevelti) from nine counties in Oregon were tested by serum-dilution plaque reduction neutralization for antibody to California serogroup viruses, including snowshoe hare, California encephalitis, and Jamestown Canyon, as well as to Cache Valley (Bunyamwera serogroup) and Klamath, an ungrouped rhabdovirus. Of 132 samples tested, 60 (46%) were found to be seropositive at a dilution of greater than or equal to 1:10 for at least one of the five different arboviruses. Forty (30%) samples contained antibody to more than one arbovirus, and 15 samples (11%) contained antibody to all five. Of these 15, 14 were from 75 black-tailed deer sera collected in Lincoln County, Oregon. Seropositivity rates for black-tailed deer ranged from 23% to 35%, with all five arboviruses represented. Positive reactions for all five arboviruses were represented among mule deer sera at rates from 5% to 29%. Elk sera were found to be positive for four of the viruses (none for Klamath virus). Although Cache Valley and Klamath viruses have been reported from Oregon, these data represent the first evidence of a California serogroup virus in the state.

Animals↗
PubMed1985

Control of snow pool mosquitoes with Bacillus thuringiensis serotype H-14 in mountain environments in California and Oregon.

Studies were conducted in mountainous areas of California and Oregon to test the effectiveness of Bacillus thuringiensis serotype H-14 in controlling larvae of snow pool Aedes mosquitoes, and also the effect of such larval control on the density of adult mosquitoes. California and Oregon studies showed that a wettable powder formulation of B.t.i. was effective in controlling mosquito larvae. In Oregon, treatment was effective even at water temperatures as low as 5 degrees C. Sampling of adult mosquitoes at campgrounds where intensive larval control was done failed to demonstrate a lowering of adult mosquito density in comparison with untreated control areas. Flight range studies showed that snow pool Aedes species can fly distances of up to 2 km, suggesting that infiltration from outside the treated area was one cause of failure. Inadequate seasonal timing appeared to be an additional factor. Using a simple computer model, we estimated that larval mosquito control with B.t.i. could be done for about $5,000 per season for a 500 ha area similar to our test area, a cost of $10 per ha ($4 per acre).

Aedes↗
PubMed1979

Experimental infection of vertebrates of the Pocomoke Cypress Swamp, Maryland with Keystone and Jamestown Canyon viruses.

Experimental studies were conducted to assess the susceptibility of white-tailed deer (Odocoileus virginianus), gray squirrels (Sciurus carolinensis), and cottontail rabbits (Sylvilagus floridanus) to Jamestown Canyon (JC) and/or Keystone (KEY) virus infection. Viremia occurred in 5 of 6 deer inoculated with JC virus; however, all deer developed KEY virus neutralizing antibody. Based on the observation that antibody elicited by primary infection of deer with either KEY or JC virus exhibited partial heterologous neutralization in vitro, cross-challenge experiments were performed in these animals. Keystone virus failed to infect deer 30 days post primary JC virus infection; however, deer became infected when challenged with KEY virus 80 days after the initial JC virus infection as indicated by a substantial increase in antibody titer. Similarly, JC virus failed to produce viremia in immune animals infected with KEY virus 80 days previously, although 2 of the 3 animals challenged had serological evidence of infection. Three field-collected cottontail rabbits with no evidence of KEY antibody were readily susceptible to KEY virus infection and developed viremias of 1-4 days' duration; rabbits with KEY virus antibody did not develop viremia upon KEY virus challenge. Eight antibody-negative field-collected gray squirrels became viremic following injection with KEY virus; however, a comparable group of squirrels did not become viremic when injected with JC virus.

Animals↗