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B F Eldridge

Publications and source records attributed to B F Eldridge.

At least 19 recordsLinked to original sources
PubMed1996

Geographic distribution and serologic and genomic characterization of Morro Bay virus, a newly recognized bunyavirus.

More than 75,000 immature mosquitoes in three genera were collected from coastal California, reared to the adult stage, and tested for virus by plaque assay in Vero cell cultures. Twenty-six strains of Morro Bay (MB) virus, a newly recognized member of the California (CAL) serogroup, were isolated from Aedes squamiger, a pestiferous salt marsh mosquito species restricted to intertidal salt marshes in coastal California and Baja California. The geographic distribution of the isolates was 10 from San Luis Obispo County, one each from Santa Barbara and Orange Counties, and 14 from San Diego County. No virus isolations were made from 23,157 Ae. squamiger collected north of San Luis Obispo County (midpoint in the geographic range of this species in California). Thus, MB virus infection in Ae. squamiger appears to be restricted to the southern range of this species in California. Serum dilution neutralization tests indicated that MB virus represents a novel subtype of the California encephalitis (CE) serotype within the CAL serogroup. Comparative analyses of genomic sequence data from four geographically distinct MB virus isolates indicated that the isolates are genetically similar to each other and distinct from other CE serotype bunyaviruses. Phylogenetic analysis of nucleocapsid protein gene sequence data indicated that MB virus represents a distinct lineage within the CE serotype and thus supports the serologic classification of MB virus as a distinct CAL serogroup virus.

Aedes↗
PubMed1996

Ecology of Jamestown Canyon virus (Bunyaviridae: California serogroup) in coastal California.

This paper reports the first isolation of Jamestown Canyon (JC) virus from coastal California and the results of tests for antibody to JC virus in mammals living in coastal California. The virus isolation was made from a pool of 50 Aedes dorsalis females collected as adults from Morro Bay, San Luis Obispo County, California. The virus isolate was identified by two-way plaque reduction-serum dilution neutralization tests done in Vero cell cultures. Sera from the mammals were tested for antibody to JC virus by a plaque-reduction serum dilution neutralization method. A high prevalence of JC virus-specific antibody was found in horses and cattle sampled from Morro Bay. This finding is additional evidence for the presence of a virus antigenically identical or closely related to JC virus in Morro Bay and indicates that the vectors of the virus in Morro Bay feed on large mammals. A high prevalence of virus-specific antibody was also found in horses sampled from Marin and San Diego counties. This finding suggests that viruses antigenically identical or closely related to JC virus are geographically widespread in coastal California.

Aedes↗
PubMed1994

Natural vertical transmission of western equine encephalomyelitis virus in mosquitoes.

The mechanism by which western equine encephalomyelitis (WEE) virus and other mosquito-borne alphaviruses (Togaviridae) survive during periods of vector inactivity is unknown. Recently, three strains of WEE virus were isolated from adult Aedes dorsalis collected as larvae from a salt marsh in a coastal region of California. This provides evidence of vertical transmission of WEE virus in mosquitoes in nature. Vertical transmission in Ae. dorsalis and closely related mosquito species may be an important mechanism for the maintenance of WEE virus in temperate regions in North America where horizontal transmission of the virus is seasonal.

Aedes↗
PubMed1993

Vector competence of alpine, Central Valley, and coastal mosquitoes (Diptera: Culicidae) from California for Jamestown Canyon virus.

Mosquitoes collected from alpine, Central Valley, and coastal habitats in California were evaluated for their vector competence for four strains of Jamestown Canyon (JC) virus. Three of the viral strains examined were isolated from alpine Aedes species collected in California, and one, the prototype JC virus, was isolated from Culiseta inornata (Williston) collected in Colorado. Alpine Aedes tahoensis Dyar, Ae. cataphylla Dyar, Ae. hexodontus Dyar, Ae. increpitus Dyar, Ae. clivis Lanzaro and Eldridge, and coastal Aedes washinoi Lanzaro and Eldridge were variably susceptible to alpine strains of JC virus. Infection rates ranged from 22 to 77%, and peroral transmission rates of the infected females ranged from 0 to 26%. The differences were related to both mosquito species and viral strain. Coastal populations of Cs. inornata, Ae. washinoi, and Ae. sierrensis (Ludlow) were incompetent vectors when fed an alpine strain of JC virus, whereas Ae. squamiger (Coquillet) and Ae. dorsalis (Meigen) were competent vectors. Peroral transmission rates following parenteral infection of females of most species were about twofold higher than those for perorally infected females. A population of Cs. inornata from the Central Valley was highly susceptible when fed an alpine strain of JCV and transmitted virus both horizontally and vertically. Alpine strains of JC virus also were transmitted vertically by Ae. tahoensis, Ae. washinoi, and Ae. squamiger following parenteral infection of females.

Aedes↗
PubMed1993

Vector competence of selected mosquito species (Diptera: Culicidae) for California strains of Northway virus (Bunyaviridae: Bunyavirus).

Selected mosquito species from Central Valley, coastal, and alpine habitats of California were evaluated for their vector competence for Northway (NOR) virus. Culiseta incidens Thomson, Culiseta inornata (Williston), and Anopheles freeborni Aitken were the only competent vectors when fed virus. Aedes sierrensis (Ludlow), as well as alpine snow pool Aedes (i.e., Ae. cataphylla Dyar, Ae. hexodontus Dyar, Ae. increpitus Dyar and Ae. tahoensis Dyar), Ae. melanimon Dyar, Ae. washinoi Lanzaro & Eldridge, Culex erythrothorax Dyar, and Cx. tarsalis Coquillett were highly refractory to peroral infection. Alpine snow pool species were poor vectors even following parenteral infection, but 21-35% of intrathoracically inoculated Ae. sierrensis from several lower elevation localities and 39-46% of parenterally infected Cx. tarsalis were able to transmit NOR virus per os. Perorally infected Cs. inornata transmitted NOR virus vertically to their F1 adult progeny at a low rate (minimal filial infection rate, 1:248).

Animals↗
PubMed1993

Isolations of Jamestown canyon virus (Bunyaviridae: California serogroup) from mosquitoes (Diptera: Culicidae) in the western United States, 1990-1992.

Nearly 80,000 immature and adult mosquitoes in three genera were collected in high-elevation (> 1,000 m) areas of California (68,229), Nevada (3,721), Oregon (5,918), and Washington (1,629) during 1990-1992 and tested for virus as adult males or females in 1,799 pools. Collections comprised primarily alpine Aedes in the Aedes communis (De Geer) group of the subgenus Ochlerotatus. Thirteen strains of Jamestown Canyon (JC) virus were recovered by plaque assay in Vero cell culture from three members of the Ae. communis group: 10 from Aedes tahoensis Dyar, 2 from Aedes cataphylla Dyar, and 1 from Aedes hexodontus Dyar. All isolates came from collections made in Alpine, Sierra, Tulare, or Tuolumne counties in the Sierra Nevada of California. Vertical transmission of JC virus in all three mosquito species was demonstrated by the isolation of virus from adult males or females reared from field-collected larvae or pupae. The prevalence of infected Ae. tahoensis was significantly higher in field-collected adult females than in reared adult males and females in Alpine County, which indicated that JC virus was being amplified by horizontal transmission. This study further incriminated Ae. tahoensis, Ae. cataphylla, and Ae. hexodontus as natural vectors of JC virus in California and greatly extended the known geographical range of this virus in the Sierra Nevada.

Altitude↗
PubMed1992

Seroepidemiology of California and Bunyamwera serogroup bunyavirus infections in humans in California.

Several human populations in California were surveyed cross-sectionally and longitudinally for neutralizing antibodies to selected arthropod-borne bunyaviruses in the California and Bunyamwera serogroups. Overall, the prevalence of antibodies to California serogroup viruses was 6.4% in 702 individuals sampled during 1963-1988. Comparative antibody titers in individual sera indicated that 4.1% and 1.6% of these infections were caused by viruses similar or identical to Jamestown Canyon and California encephalitis, respectively. Evidence of prior infection with the Jamestown Canyon serotype was found in 10% of 118 humans employed outdoors in high elevation areas and sampled in 1988, including 5 of 16 persons (31%) employed as rangers patrolling in remote forests and meadows. This probably reflects increased exposure to bites of boreal mosquitoes that breed in pools of melted snow. Antibodies to Bunyamwera serogroup viruses, including the Northway serotype, which was recently shown to be enzootic in California, were found in only 2 of 702 humans studied. No seroconversions were detected to selected California or Bunyamwera serogroup viruses in paired samples from 392 humans, including 349 patients with acute central nervous system disease or undifferentiated febrile illnesses who were sampled during 1963-1988, and thus these viruses are currently unconfirmed as human pathogens in California.

Adolescent↗
PubMed1992

Vector competence of California mosquitoes for California encephalitis and California encephalitis-like viruses.

Mosquitoes collected from coastal, inland valley, and alpine locations in California were evaluated for their experimental vector competence for two viruses in the California serogroup (Bunyaviridae:Bunyavirus). Aedes squamiger, a coastal salt marsh mosquito, was an efficient vector of a California encephalitis (CE)-like virus isolated from its habitat (89% of the pledget-fed females became infected and 61% transmitted virus). Aedes dorsalis, a coastal mosquito, and Ae. melanimon, an inland valley mosquito, were competent vectors of prototype CE virus (98% and 100% of the pledget-fed females became infected and 56% and 30%, respectively, transmitted virus). Aedes squamiger and Ae. dorsalis transmitted both viruses vertically to one or more of 20 of their progeny. Culiseta inornata was susceptible to infection with both viruses, but 5% or less transmitted virus perorally. Alpine mosquitoes, Ae. cataphylla, Ae. increpitus, and Ae. tahoensis, became infected with both CE and CE-like viruses, but 3% or less transmitted virus. All species of mosquitoes were more efficient vectors of both viruses following intrathoracic inoculation than following pledget feeding, suggesting the presence of mesenteronal barriers.

Animals↗
PubMed1992

Patrick Manson and the discovery age of vector biology.

There have been few scientists who have had a greater impact on the history of vector biology than Sir Patrick Manson (1844-1922). By demonstrating that mosquitoes became infected with microfilariae in the process of taking a blood meal, he became the first to prove an association between insects and pathogens causing human and animal diseases. He also contributed substantially to the discovery of mosquito transmission of malaria parasites and was a principal force behind the founding of the London School of Tropical Medicine and the Royal Society of Tropical Medicine and Hygiene. Manson's career is reviewed in historical context as well as in relation to modern concepts of vector biology.

China↗
PubMed1992

Conservation of the names Culex stigmatosoma and Culex thriambus.

As a result of action by the International Commission on Zoological Nomenclature, the name Culex peus Speiser is suppressed and never to be used as a valid name, and the names Culex stigmatosoma Dyar and Culex thriambus Dyar are conserved for the western banded foul-water mosquito and the related southwestern U.S. species, respectively.

Animals↗
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↗