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Biomedical subjects

W C Reeves

Publications and source records attributed to W C Reeves.

At least 235 records · Page 13Linked to original sources
PubMed1976

Relation of mosquito density to bird: mammal feeding ratios of Culex tarsalis in stable traps.

Stable traps, each baited with a jackrabbit and either a chicken or a pheasant, collected more than 21,000 mosquitoes in the Sacramento Valley, California, in 1972 and 1973. The focus of interest was the feeding behavior of Culex tarsalis, a primary vector of encephalitis viruses. Generally, feeding success was less and feeding rates on the jackrabbit were greater when larger numbers of mosquitoes were collected, or when a bird was exposed that was less receptive to mosquito feeding. Greater feeding rates on the jackrabbit apparently resulted from decreased feeding on the avian host and from diversion of mosquitoes to the jackrabbit. Figures are given that show how changes in feeding rates on birds affect the probabilities that a mosquito that feeds twice would feel both times on a bird, or on a bird and then on a mammal. Relatively small collections of nine mosquito species other than C. tarsalis revealed distinct species differences in feeding behavior. Aedes malanimon showed a preference for jackrabbit, which is relevant to its role as a vector of western equine encephalitis and California encephalitis viruses.

Aedes↗
PubMed1976

Species identification of blood meals from Culex tarsalis that had fed on passeriform birds.

Blood-engorged Culex tarsalis (4,209) collected during 1960 to 1965 in Kern County, California and previously shown to have fed on passeriform birds by the precipitin test were further tested by the more sensitive passive hemagglutination inhibition test (PHI). It was shown that these mosquitoes fed principally on House Finches and House Sparrows, the most common passeriform birds found in the collection areas. These data demonstrate the usefulness of the PHI test for the identification of arthropod blood meals from closely related species.

Animals↗
PubMed1976

A field trial of competitive displacement of Aedes polynesiensis by Aedes albopictus on a Pacific atoll.

Prior laboratory studies and field observations suggested that it might be possible to reduce the size of the population of, or eliminate, Aedes polynesiensis by the introduction of Aedes albopictus. The former mosquito is the principal vector of nonperiodic filariasis caused by Wuchereria bancrofti and the latter is a closely related species refractory to the development of human filariae. The practicability of such competitive displacement was studied by a field trial on a remote coral atoll where there was an established population of A. polynesiensis. Three strains of Al albopictus were liberated at separate localities on the atoll and their fate was followed for 4 years. One strain disappeared within 12 months after release and the other two disappeared within 48 months. It was not clear whether A. albopicuts failed to become established because the strains were unsuitable, the general environment was inappropriate, or A. polynesiensis was present in such numbers that A. albopictus rarely succeded in mating with its own species.

Aedes↗
PubMed1975

Familial clustering of hepatitis B surface antigen among Panamanian Indians.

Several authors have suggested that the host genome determines the occurrence of chronic HBS Ag (hepatitis B surface antigen). In attempts to evaluate this possibility, total infection rate and the combined frequencies of HBS Ag and antibody to HBS Ag and radioimmunoprecipitation to measure antibody to HBS Ag, we tested sera from 255 Panamanian Guaymi Indians. They represented 48 families and 32 living units. Clusters of chronically antigenemic individuals were found in families. Clusters of infection were not found in families or living units. Differences in family composition (age and sex) did not explain the increased occurrence of HGS Ag. These findings support the hypothesis that some humans have an inherited susceptibility to chronic infection with hepatitis B virus after exposure.

Adolescent↗
PubMed1975

The epidemiology of hepatitis B antigen and antibody among Panamanian Cuna Indians.

Previous studies of hepatitis B antigen (HBsAg) and antibody to it (anti-HBs) showed widely differing exposures between Panamanian Indian tribes. Cuna Indians living on islands appeared infrequently exposed to HBsAg; we found no one antigenemic and low age specific anti-HBs rates. In contrast, mainland dwelling Guaymi and Chocó Indians had a high prevalence of anti-HBs. We have now measured HBsAg by counterelectrophoresis and anti-HBs by radioimmunoassay in two Cuna Indian groups who live in the Darien forest. The prevalence of HBsAg among Darien Cuna was low, 3 positive of 239 tested, but 106 (44%) had anti-HBs. Darien Cuna thus evidenced greater exposure to HBsAg than island Cuna (8% had anti-HBs) and had an anti-HBs prevalence similar to the neighboring Chocó Indians (42%). The Guaymi Indians of western Panama had a lower frequency of anti-HBs (29%) than either Chocó or mainland Cuna but their frequency of chronic antigenemia was significantly greater. These data suggest that while exposure may be a function of village habitat, chronic antigenemia may reflect differences in host responses.

Adolescent↗
PubMed1974

Experimental infection with western equine encephalomyelitis virus in wild rodents indigenous to Kern County, California.

Six species of rodents from Kern County, California, were inoculated subcutaneously with western equine encephalomyelitis (WEE) virus to determine their susceptibility to infection and their potential as natural hosts. Ammospermophilus nelsoni, Citellus beecheyi, Dipodomys heermanni, Dipodomys nitratoides, Peromyscus maniculatus, and Sciurus griseus were readily infected. Infection was usually fatal in Dipodomys species, C. beecheyi, and S. griseus, but was clinically inapparent in other species. Viremic responses varied greatly in magnitude and duration in different species and with different viral strains. Viremic animals that survived developed high titers of hemagglutination-inhibiting antibody. Hemagglutination-inhibiting and neutralizing antibodies persisted at high titers for at least 8 to 58 weeks after infection, except in P. maniculatus. If animals died during or shortly after the viremic phase of infection, the virus usually was recoverable from numerous organs. Long-term survival of virus could not be demonstrated in A. nelsoni and Dipodomys species. It is concluded that A. nelsoni and P. maniculatus are not important natural hosts of WEE virus; they are susceptible to infection and develop antibodies, but serological surveys of the same species rarely reveal evidence of infection. S. griseus, D. heermanni, D. nitratoides, and possibly C. beecheyi are aberrant hosts of WEE virus since most of them died when infected. Two species of ticks that are ectoparasitic on rodents in Kern County were evaluated as vectors of WEE virus. Dermacentor parumapertus failed to become infected after feeding on viremic hosts, and Ornithodorus parkeri became infected but failed to transmit virus.

Animals↗
PubMed1974

Modoc viral infections in the deer mouse Peromyscus maniculatus.

The pathogenesis of Modoc virus and its mechanism of transmission were investigated in Peromyscus maniculatus gambeli (deer mouse) as a model to understand the natural history of this virus. Animals were readily infected by the intranasal or subcutaneous route of inoculation. Virus could be detected by direct isolation techniques in many organs and body fluids during the first 7 to 9 days after intranasal inoculation. Increases in viral titers were detectable first in lungs and then the spleen, salivary-submaxillary glands, and lymph nodes. Viremias were low titered and ephemeral. Virus was recovered from urine and throat swabs 4 to 6 days and 4 to 7 days after inoculation, respectively. Serum dilution neutralization, hemagglutination inhibition, or complement fixation antibodies were detected in sera of some animals 13 days after infection and in all animals after 20 days. Antibodies persisted for the 168-day period of observation. Persistent viral infection was demonstrable by in vitro culturing of lungs or pooled lungs, salivary glands, and kidneys from 14 of 69 mice that were sacrificed from 1 to 6 months after intranasal inoculation. Attempts to demonstrate horizontal or vertical transmission of Modoc virus among mice were generally unsuccessful. Female deer mice infected with virus before mating passed maternal antibodies to their young.

Animals↗
PubMed1972

Field studies of an attenuated Venezuelan equine encephalomyelitis vaccine (strain TC-83).

A series of field studies using strain TC-83 attenuated Venezuelan equine encephalomyelitis vaccine in horses was made to determine the rate of seroconversions, the postvaccination viremia, and the possibility of adverse reactions to the vaccine. The rate of seroconversions varied from 50% in one study to 91 and 100% in two others. The highest level of viremia measured was 7 x 10(3) to 8 x 10(3) plaqueforming units per ml. No adverse reactions to the vaccine were observed in any horses, including 42 pregnant mares and their resulting foals.

Animals↗