An Analysis of the Relationship Between Stress and Parasitism

The impact of stress upon the dynamics of host and parasite populations is varied. It may be expressed physiologically or behaviorally in either the host or the parasite. The outcome of stress may be an increase or a decrease in natality and mortality which may then result in significant changes in the densities of the involved popula- tions. At the ecosystem level, stress may be manifested either directly or indirectly on individuals or populations, but the outcome is change in natality or mortality and, hence, in the density of the affected species. The varied response to stressor input at the individual, population and ecosystem levels is dictated by the capacity for adaptability present at each level; the response may be modified, however, by the unique com- bination of environmental characteristics at the time of stressor input.