Emerging pathogens potentially undergo rapid evolution while expanding in population size and geographic range during the course of invasion, yet it is generally difficult to demonstrate how these processes interact. Our analysis of a 30-yr data set covering a large-scale rabies virus outbreak among North American raccoons reveals the long lasting effect of the initial infection wave in determining how viral populations are genetically structured in space. We further find that coalescent-based estimates derived from the genetic data yielded an amazingly accurate reconstruction of the known spatial and demographic dynamics of the virus over time. Our study demonstrates the combined evolutionary and population dynamic processes characterizing the spread of pathogen after its introduction into a fully susceptible host population. Furthermore, the results provide important insights regarding the spatial scale of rabies persistence and validate the use of coalescent approaches for uncovering even relatively complex population histories. Such approaches will be of increasing relevance for understanding the epidemiology of emerging zoonotic diseases in a landscape context. invasion ͉ phylogeography ͉ Procyon lotor ͉ wildlife disease ͉ zoonoses
Liver and spleen size were measured in 11 normal subjects and 12 patients with cirrhosis. Volume was calculated by adding together the area measurements obtained from successive transverse abdominal scans. The normal mean volume of the liver (+/- S.D.) was 1,493 +/- 230 cm3 and that of the spleen was 219 +/- 76 cm3; interobserver variability was 4-8% and the day-to-day coefficient of variation was 6-10%. In cirrhotic patients studied prior to and 7-10 days after a distal splenorenal shunt, the mean liver volume fell from 1,642 to 1,529 cm3 (p less than 0.06) and the mean spleen volume from 660 to 507 cm3 (p less than 0.006), supporting the use of such a shunt in selective decompression of varices and maintenance of portal hypertension. This is a clinically useful method of measuring organ volume with the required sensitivity.
Infectious disease emergence is under the simultaneous influence of both genetic and ecological factors. Yet, we lack a general framework for linking ecological dynamics of infectious disease with underlying molecular and evolutionary change. As a model, we illustrate the linkage between ecological and evolutionary dynamics in rabies virus during its epidemic expansion into eastern and southern Ontario. We characterized the phylogeographic relationships among 83 isolates of fox rabies virus variant using nucleotide sequences from the glycoprotein-encoding glycoprotein gene. The fox rabies virus variant descended as an irregular wave with two arms invading from northern Ontario into southern Ontario over the 1980s and 1990s. Correlations between genetic and geographic distance suggest an isolation by distance population structure for the virus. The divergence among viral lineages since the most recent common ancestor correlates with position along the advancing wave front with more divergent lineages near the origin of the epidemic. Based on divergence from the most recent common ancestor, the regional population can be partitioned into two subpopulations, each corresponding to an arm of the advancing wave. Subpopulation A (southern Ontario) showed reduced isolation by distance relative to subpopulation B (eastern Ontario). The temporal dynamics of subpopulation A suggests that the subregional viral population may have undergone several smaller waves that reduced isolation by distance. The use of integrated approaches, such as the geographical analysis of sequence variants, coupled with information on spatial dynamics will become indispensable aids in understanding patterns of disease emergence.infectious disease ͉ isolation by distance ͉ landscape genetics
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