Raccoon rabies in the Northeastern United States rapidly expanded in genetic diversity and spatially from 1977 to 1999 during the Mid-Atlantic outbreak. For a portion this expansion, from 1983 to 1986, the rate of epidemic expansion slowed. This is reflected in a plateau in the effective number of infections and a decrease in the rate of invasion into new areas. I used a mathematical model of rabies dynamics to test alternative hypotheses for the observed reduction in the spread of raccoon rabies. It has been theorized that the geography of the Mid-Atlantic States, particularly the rivers and terrestrial habitat, influenced these changes. I will test ten hypotheses for the slowdown using a spatially explicit model of raccoon rabies dynamics that includes a model of the pathogen’s molecular evolution.
The ten hypotheses were to test if the reduction in rate of spread was caused by 1) a geographic bottleneck created by the Atlantic coast, 2) rivers limiting the movement of raccoons, 3) rivers halting the movement of raccoons, 4) habitat limiting the movement of raccoons 5) a combination of rivers limiting movement, habitat and mountains, 6) a combination of rivers halting movement, habitat and mountains, 7) the Susquehanna River limiting movement, 8) the Susquehanna River halting movement, 9) an unidentified barrier limiting movement and 10) an unidentified barrier halting movement.
Our model results suggest that the slowdown observed from 1983 to 1987 was caused by a combination of major rivers in the area. The effects of rivers appear to explain the slowdown in the epidemic, but the addition of habitat and mountains is important to explain the sustained high levels of demographic spread in the late stages of the epidemic. In addition, our results indicate that the currently accepted estimate of raccoon dispersal over rivers may be an overestimate.
|Commitee:||France, Scott, Neigel, Joe|
|School:||University of Louisiana at Lafayette|
|School Location:||United States -- Louisiana|
|Source:||MAI 55/03M(E), Masters Abstracts International|
|Keywords:||Bats, Rabies, Terrestrial carnivores, Zoonosis|
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