Biomedical subjects

Patricia L Davis

Publications and source records attributed to Patricia L Davis.

3 recordsLinked to original sources

PubMed2006

The evolutionary history and dynamics of bat rabies virus.

Rabies virus (RABV) is endemic in terrestrial mammals throughout the world and in bats on the American continent. We performed the most extensive phylogenetic analyses of bat RABV sequences undertaken to date using a variety of genes. Our study supported previous suggestions that viral sequences are grouped according to the behaviour of the host species. However, there was more genetic and geographical diversity within each phylogenetic group than previously recognised, including evidence for new groups. Furthermore, three clades of Latin American bat RABV that were distinct from the previously identified "group IV" bat RABV clade and more closely related to North American bat RABV clades, were identified. Strikingly, phylogenetic trees for the G (glycoprotein) gene had a significantly different evolutionary history to those inferred for the N (nucleoprotein) and P (phosphoprotein) genes, and an analysis of these competing topologies revealed that it is not possible on current data to resolve whether bat RABV arose from terrestrial mammal RABV, or vice-versa. Finally, using coalescent approaches, we estimated that RABV had similar rates of population growth and nucleotide substitution (approximately 2.5-4x10(-4) substitutions per site, per year) in both bats and terrestrial mammals, despite underlying differences in epidemiology.

Animals↗

PubMed2005

Phylogeography, population dynamics, and molecular evolution of European bat lyssaviruses.

European bat lyssaviruses types 1 and 2 (EBLV-1 and EBLV-2) are widespread in Europe, although little is known of their evolutionary history. We undertook a comprehensive sequence analysis to infer the selection pressures, rates of nucleotide substitution, age of genetic diversity, geographical origin, and population growth rates of EBLV-1. Our study encompassed data from 12 countries collected over a time span of 35 years and focused on the glycoprotein (G) and nucleoprotein (N) genes. We show that although the two subtypes of EBLV-1--EBLV-1a and EBLV-1b--have both grown at a low exponential rate since their introduction into Europe, they have differing population structures and dispersal patterns. Furthermore, there were strong constraints against amino acid change in both EBLV-1 and EBLV-2, as reflected in a low ratio of nonsynonymous to synonymous substitutions per site, particularly in EBLV-1b. Our inferred rate of nucleotide substitution in EBLV-1, approximately 5 x 10(-5) substitutions per site per year, was also one of the lowest recorded for RNA viruses and implied that the current genetic diversity in the virus arose 500 to 750 years ago. We propose that the slow evolution of EBLVs reflects their distinctive epidemiology in bats, where they occupy a relatively stable fitness peak.

Animals↗

PubMed2003

Optic nerve head drusen.

Optic disc drusen are congenital and developmental anomalies of the optic nerve head seen commonly in clinical practice, often as an incidental ophthalmologic finding during routine exams. Optic disc drusen are a form of calcific degeneration in some of the axons of the optic nerve. Visual acuity is often not affected but the visual fields of these patients can be abnormal and deteriorate over time. Optic disc drusen are familial and are not uncommon. They are thought to be the result of pathology at the level of the optic nerve head itself. The diagnosis can be made with clinical findings combined with B scan ultrasound and computed tomography. In addition, newer modalities using optic nerve head tomography are proving to be very useful. Since children as well as adults are affected, it is important to consider optic nerve head drusen in the differential diagnosis of papilledema or optic nerve swelling.

Diagnosis, Differential↗