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Robert D Bradley

Publications and source records attributed to Robert D Bradley.

8 recordsLinked to original sources
PubMed2006

Neotomine-peromyscine rodent systematics based on combined analyses of nuclear and mitochondrial DNA sequences.

Recently, sequences from two nuclear genes (exon 6 of the dentin matrix protein 1 gene and intron 7 of the beta-fibrinogen gene) and one mitochondrial gene (cytochrome b gene) were used independently in an attempt to resolve phylogenetic relationships within the neotomine-peromyscine complex. Although these studies provided testable hypotheses regarding this group of rodents, the affinities of certain tribes and genera remain uncertain. To elucidate these relationships, the three data partitions were tested for heterogeneity and then concatenated according to conditional data combination and total evidence approaches. Support was found for five clades, four of which correspond to well recognized tribes (the Neotomini, Peromyscini=Reithrodontomyini, Baiomyini, and Tylomyini). Recommendations are made regarding the recognition of Ochrotomys as a tribe of its own, the Ochrotomyini, paralleling other recent findings. The Peromyscini, Baiomyini, and Ochrotomyini are unresolved in relation to each other, but as a whole are sister to the Neotomini. The Tylomyini is basal to all clades. It appears that combined data from the nuclear and mitochondrial genes (analyzing all three partitions simultaneously) resulted in the best phylogenetic hypothesis regarding the complex.

Animals↗
PubMed2006

Catacamas virus, a hantaviral species naturally associated with Oryzomys couesi (Coues' oryzomys) in Honduras.

The primary objective of this study was to extend our knowledge of the geographical distribution, genetic diversity, and natural host associations of the hantaviruses indigenous to North America. Antibody to a hantavirus was found in 5 (20.8%) of 24 Coues' oryzomys (Oryzomys couesi) and none of 41 other rodents captured near the town of Catacamas in eastern Honduras, and a hantavirus was isolated from one of the antibody-positive Coues' oryzomys. Analyses of nucleotide and amino acid sequence data indicated that the viral isolate is a strain of a novel hantaviral species (proposed species name "Catacamas virus") that is phylogenetically most closely related to Bayou virus, a hantaviral species that is principally associated with Oryzomys palustris (marsh oryzomys) in the southeastern United States. Catacamas virus is the first evidence for the occurrence of a hantaviral species in Honduras and the first evidence that a hantaviral species is naturally associated with an Oryzomys species other than O. palustris.

Animals↗
PubMed2004

Experimental Everglades virus infection of cotton rats (Sigmodon hispidus).

Everglades virus (EVEV), an alphavirus in the Venezuelan equine encephalitis (VEE) serocomplex, circulates among rodents and vector mosquitoes and infects humans, causing a febrile disease sometimes accompanied by neurologic manifestations. EVEV circulates near metropolitan Miami, which indicates the potential for substantial human disease, should outbreaks arise. We characterized EVEV infection of cotton rats in South Florida, USA, to validate their role in enzootic transmission. To evaluate whether the viremia induced in cotton rat populations regulates EVEV distribution, we also infected rats from a non-EVEV-endemic area. Viremia levels developed in rats from both localities that exceeded the threshold for infection of the vector. Most animals survived infection with no signs of illness, despite virus invasion of the brain and the development of mild encephalitis. Understanding the mechanisms by which EVEV-infected cotton rats resist clinical disease may be useful in developing VEE therapeutics for equines and humans.

Alphavirus↗
PubMed2004

Epizootiology of arenaviral infections in the white-throated woodrat (Muridae: Sigmodontinae) and other woodrats in Arizona.

The purpose of this study was to extend and refine our knowledge of the geographical distribution and natural host relationships of the arenaviruses associated with woodrats indigenous to Arizona. Antibody to a Tacaribe serocomplex virus was found in 112 of 1,250 white-throated woodrats, five of 208 Mexican woodrats, one of 114 Stephen's woodrats, and none of 862 other rodents captured at 51 sites in 10 counties in Arizona. Of the 112 antibody-positive white-throated woodrats, 109 (97.3%) were captured within extensive, dense patches of prickly pear cactus and cane cholla in three counties in mid-central Arizona. Analysis of the serological and zoographical data suggested that white-throated woodrats usually become infected early in life and that the distribution of antibody-positive white-throated woodrats in Arizona is not linked to a specific biome.

Animals↗
PubMed2002

Molecular systematics of the genus Neotoma.

DNA sequences from the mitochondrial DNA cytochrome-b gene were used to infer the systematic relationships of 13 species of wood rats (genus Neotoma). Parsimony, likelihood, and neighbor-joining analyses produced similar topologies in most cases and produced six systematic conclusions. First, results of previous studies were supported in the recognition of N. floridana magister as distinct species (N. magister). Second, evidence was provided for the recognition of cryptic species within N. albigula (N. albigula and N. leucodon) and N. mexicana (N. mexicana, N. isthmica, and N. picta). Third, the subgenus Neotoma is composed of four species groups (floridana, lepida, mexicana, and micropus). Fourth, support was provided for placement of N. stephensi within the lepida species group. Fifth, support was provided for the recognition of Hodomys as a separate genus, sister to Xenomys. Sixth, support for the elevation of the subgenus Teonoma to generic status is discussed.

Animals↗
PubMed2002

Bear Canyon virus: an arenavirus naturally associated with the California mouse (Peromyscus californicus).

Thirty-four rodents captured in southern California were studied to increase our knowledge of the arenaviruses indigenous to the western United States. An infectious arenavirus was isolated from 5 of 27 California mice but none of the 7 other rodents. Analyses of viral nucleocapsid protein gene sequence data indicated that the isolates from the California mice are strains of a novel Tacaribe serocomplex virus (proposed name "Bear Canyon") that is phylogenetically most closely related to Whitewater Arroyo and Tamiami viruses, the only other Tacaribe serocomplex viruses known to occur in North America. The discovery of Bear Canyon virus is the first unequivocal evidence that the virus family Arenaviridae is naturally associated with the rodent genus Peromyscus and that a Tacaribe serocomplex virus occurs in California.

Animals↗
PubMed2002

Natural host relationships and genetic diversity of Whitewater Arroyo virus in southern Texas.

The purpose of this study was to refine our knowledge of the natural host relationships of Whitewater Arroyo (WWA) virus. Two hundred eight rodents, representing nine species, were captured in July 1999 on the Chaparral Wildlife Management Area in southern Texas and tested for evidence of arenavirus infection. Antibody to an arenavirus was found in seven (21.9%) of 32 southern plains woodrats (Neotoma micropus) and none of 168 other rodents. Infectious WWA virus was isolated from four antibody-positive southern plains woodrats, one of 25 antibody-negative southern plains woodrats, and none of 176 other rodents. Collectively, the results indicate that the southern plains woodrat is a principal host of WWA virus in southern Texas. Analyses of viral gene sequence data revealed substantial genetic diversity among WWA virus strains isolated from the woodrats, suggesting that multiple variants of the virus can coexist in a single woodrat species in a small geographic area.

Animals↗