Coral Resistance to Disease

Understanding the dynamics of resistance is particularly important for understanding the impacts of disease and predicting evolutionary outcomes for diseases. Predictive epidemiological models include not only terms for transmission of infectious microorganisms, but also terms for host resistance. In susceptible-infected-resistant (SIR) epidemiological models, timing and degree of resistance can determine the spread rate and impact of disease (Anderson and May 1979, 1991). Resistance is defined as “the natural or acquired ability of an organism to maintain its immunity to or to resist the effects of an antagonistic agent, e.g., pathogenic microorganism, toxin, drug (Stedman 1995).” An organism that is immune to an infectious disease will not acquire it because it has a particular suite of complex structural and functional features. These features prevent the pathogenic microorganism from entering, surviving in, or multiplying within its body and causing disease by disrupting key cellular metabolic processes through the release of toxins or enzymes or by altering its structure (e.g., tissue damage through scarring), or causing cell death. Many factors can affect the condition of this system and the response to a pathogen that an individual host is capable of generating at a particular time. The interaction of host and pathogen, and how they are affected by changing environmental conditions, can affect the populations of both organisms (Garnett and Holmes 1996).