PARENT SESSION
Oral Session # 94: Pathogens, Toxins, and Disease III.
Presiding: C Duffie
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 200.
The importance of a complex life history in the long-term persistence of a lethal virus in seasonally abundant salamander populations.
Brunner, Jesse, Collins, James,
ABSTRACT- The transmission of most infectious diseases is a density dependent process. Below a critical host population size or density, the contact rate between infected and susceptible hosts is too low to sustain the chain of transmission and the parasite dies out in the host population. Sustained transmission is least likely for virulent parasites in slowly increasing host populations (high transmission rates and short infectious periods, coupled with low rates of birth or introduction of susceptible hosts). Thus, virulent parasites are not expected to persist in the small, slowly growing populations typical of endangered species unless the parasite has an abundant, widespread reservoir host. Such reservoirs can maintain virulent parasites endemically; reintroducing disease into smaller, vulnerable populations when they come into contact. The ranavirus-tiger salamanders system is an exception to this paradigm. This lethal, directly transmitted virus causes recurrent epidemics in the dense larval segment of salamander populations. However, salamander larvae metamorphose and disperse to burrows to overwinter, precluding much transmission. This virus degrades quickly in the environment and has no reservoir host. Rather persistence between epidemics is achieved by infrequent, long-lived, chronic infections in the metamorphosed salamanders, which are normally highly susceptible. Both life history stages are apparently essential for the persistence of these lethal viruses: larvae amplify the prevalence of virus infection; metamorphs maintain infections between epidemics and reintroduce the virus when they return to ponds to breed. I will present the results of a mathematical model examining how the complex life history of tiger salamanders helps maintain this dynamic host-pathogen system.
Key words: persistence, mathematical model, Infectious disease, Ambystoma tigrinum