Pathogen transmission in age- or stage-structured populations will be complicated by which stages can become infected, and which stages become infectious and transmit the pathogen to other hosts. Here we examine pathogen spread in naive populations via stage-structured models, to look how life history differences can affect initial spread of disease into naive populations. We look for evidence of transience, that early spread may deviate from equilibrium dynamics either by fading out quickly or amplifying to large numbers of infected individuals before settling down to endemic persistence. Further, we describe methods for testing sensitivity of the model to parameters.
Results/Conclusions We consider two cases: the spread of pine blister rust into populations of high elevation five-needle pines and the spread of chronic wasting disease into deer populations. We find that the relatively higher fecundity of trees leads to greater transience in the rate of spread of pathogens for pines than deer. Further, in the absence of density dependent population growth of hosts, especially for early infective stages, pathogens have a higher probability of causing extinction of their hosts. With density dependent regulation of host populations, endemic persistence is more likely.
