Geology topics

V. Shankar

Publications and source records attributed to V. Shankar.

4 recordsLinked to original sources

USGS2008

An analysis of correspondence between unique rabies virus variants and divergent big brown bat (Eptesicus fuscus) mitochondrial DNA lineages

The literature supports that unique rabies virus (RABV) variants are often compartmentalized in different species of bats. In Colorado, two divergent mtDNA lineages of big brown bats (Eptesicus fuscus) co-occur. RABV associated with this species also segregates into two clades. We hypothesized that unique RABV variants might be associated with mtDNA lineages of Colorado big brown bats. DNA was extracted from brain tissue of rabid big brown bats, the ND2 gene was amplified to determine mtDNA lineage, and the lineage was compared to a previously derived phylogenetic analysis of the RABV N gene. No correspondence was found between host bat lineage and RABV variant. ?? 2008 Springer-Verlag.

Archives of Virology↗

USGS2007

Lack of association between ectoparasite intensities and rabies virus neutralizing antibody seroprevalence in wild big brown bats (Eptesicus fuscus), Fort Collins, Colorado

Recently, bat ectoparasites have been demonstrated to harbor pathogens of potential importance to humans. We evaluated antirabies antibody seroprevalence and the presence of ectoparasites in big brown bats (Eptesicus fuscus) sampled in 2002 and 2003 in Colorado to investigate if an association existed between ectoparasite intensity and exposure to rabies virus (RV). We used logistic regression and Akaike's Information Criteria adjusted for sample size (AICc) in a post-hoc analysis to investigate the relative importance of three ectoparasite species, as well as bat colony size, year sampled, age class, colony size, and year interaction on the presence of rabies virus neutralizing antibodies (VNA) in serum of wild E. fuscus. We obtained serum samples and ectoparasite counts from big brown bats simultaneously in 2002 and 2003. Although the presence of ectoparasites (Steatonyssus occidentalis and Spinturnix bakeri) were important in elucidating VNA seroprevalence, their intensities were higher in seronegative bats than in seropositive bats, and the presence of a third ectoparasite (Cimex pilosellus) was inconsequential. Colony size and year sampled were the most important variables in these AICc models. These findings suggest that these ectoparasites do not enhance exposure of big brown bats to RV. ?? 2007 Mary Ann Liebert, Inc.

Vector-Borne and Zoonotic Diseases↗

USGS2006

Texture analysis for automated classification of geologic structures

Texture present in aeromagnetic anomaly images offers an abundance of useful geological information for discriminating between rock types, but current analysis of such images still relies on tedious, human interpretation. This study is believed to be the first effort to quantitatively assess the performance of texture-based digital image analysis for this geophysical exploration application. We computed several texture measures and determined the best subset using automated feature selection techniques. Pattern classification experiments measured the ability of various texture measures to automatically predict rock types. The classification accuracy was significantly better than a priori probability and prior weights-of-evidence results. The accuracy rates and choice of texture measures that minimize the error rate are reported. ?? 2006 IEEE.

Conference Paper↗

USGS2004

Rabies in a captive colony of big brown bats (Eptesicus fuscus)

Our research has focused on the ecology of commensal populations of big brown bats ( Eptesicus fuscus ) in Fort Collins, Colorado (USA), in relation to rabies virus (RV) transmission. We captured 35 big brown bats ( Eptesicus fuscus ) in late summer 2001 and held them captive for 4.8 mo. The bats were initially placed in an indoor cage for 1 mo then segregated into groups of two to six per cage. Two of the bats succumbed to rabies virus (RV) within the first month of capture. Despite group housing, all of the remaining bats were healthy over the course of the investigation; none developed rabies, although one of the rabid bats was observed to bite her cage mates. Reverse transcription–polymerase chain reaction (RT-PCR) and Taqman ® real-time PCR analysis of the RNA derived from the brain tissue, salivary glands, and oral swab samples confirmed RV infection in the dead bats. Rabies virus was also isolated from the brain tissue upon passage in mouse neuroblastoma cells. Nucleotide sequence analysis of the RV nucleoprotein (N) gene showed 100% identity with the N gene sequence of a 1985 E. fuscus isolate from El Paso County, Colorado. Bat sera obtained six times throughout the study were assayed for RV neutralizing antibodies using the rapid fluorescent focus inhibition test. The RV neutralizing activity in the serum was associated with the IgG component, which was purified by binding to protein G Sepharose. Five bats were RV seropositive prior to their capture and maintained titers throughout captivity. Two adult bats seroconverted during captivity. Two volant juvenile bats had detectable RV antibody titers at the first serum collection but were negative thereafter. Four seronegative bats responded to a RV vaccine administration with high titers of RV antibodies. A serologic survey of big brown bats in the roost from which one of the captive rabid bats had originated showed a significant rise in seroprevalence during 2002.

Journal of Wildlife Diseases↗