The Effect of Host Genetic Diversity on Disease Spread

Host genetic diversity is thought to reduce the likelihood that disease will spread in natural populations. In this study, I present an epidemiological model for the intrinsic rate of spread (R-0) for an infectious disease. The results show that the average value for R-0 ((R) over bar (0)) is inversely related to the number of host genotypes in the population (G), assuming that each host genotype is susceptible to a different parasite genotype. Specifically, for large host populations, (R) over bar (0) is equal to B/G, where B is the number of infectious propagules produced by each infection that contact a different host. The results also suggest that virulent, single-strain infections, which initially spread in genetically diverse host populations, would quickly die out when the parasite depresses the frequency of susceptible hosts below 1/B. These results are consistent with empirical studies showing that genetically diverse host populations suffer less from pathogens and parasites.