Abstract
This article uses stochastic simulations with a compartmental epidemic model to quantify the impact of genetic diversity within animal populations on the transmission of infectious disease. Genetic diversity is defined by the number of distinct genotypes in the population conferring resistance to microparasitic (e.g., viral or bacterial) infections. Scenarios include homogeneous populations and populations composed of few (finite-locus model) or many (infinitesimal model) genotypes. Genetic heterogeneity has no impact upon the expected value of the basic reproductive ratio (the primary description of the transmission of infection) but affects the variability of this parameter. Consequently, increasing genetic heterogeneity is associated with an increased probability of minor epidemics and decreased probabilities of both major (catastrophic) epidemics and no epidemics. Additionally, heterogeneity per se is associated with a breakdown in the expected relationship between the basic reproductive ratio and epidemic severity, which has been developed for homogeneous populations, with increasing heterogeneity generally resulting in fewer infected animals than expected. Furthermore, increased heterogeneity is associated with decreased disease-dependent mortality in major epidemics and a complex trend toward decreased duration of these epidemics. In summary, more heterogeneous populations are not expected to suffer fewer epidemics on average, but are less likely to suffer catastrophic epidemics.
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Selected References
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- Adler F. R. The effects of averaging on the basic reproduction ratio. Math Biosci. 1992 Sep;111(1):89–98. doi: 10.1016/0025-5564(92)90080-g. [DOI] [PubMed] [Google Scholar]
- Dushoff J., Levin S. The effects of population heterogeneity on disease invasion. Math Biosci. 1995 Jul-Aug;128(1-2):25–40. doi: 10.1016/0025-5564(94)00065-8. [DOI] [PubMed] [Google Scholar]
- Hethcote H. W. An immunization model for a heterogeneous population. Theor Popul Biol. 1978 Dec;14(3):338–349. doi: 10.1016/0040-5809(78)90011-4. [DOI] [PubMed] [Google Scholar]
- MacKenzie K., Bishop S. C. Developing stochastic epidemiological models to quantify the dynamics of infectious diseases in domestic livestock. J Anim Sci. 2001 Aug;79(8):2047–2056. doi: 10.2527/2001.7982047x. [DOI] [PubMed] [Google Scholar]
- Stear M. J., Bishop S. C., Doligalska M., Duncan J. L., Holmes P. H., Irvine J., McCririe L., McKellar Q. A., Sinski E., Murray M. Regulation of egg production, worm burden, worm length and worm fecundity by host responses in sheep infected with Ostertagia circumcincta. Parasite Immunol. 1995 Dec;17(12):643–652. doi: 10.1111/j.1365-3024.1995.tb01010.x. [DOI] [PubMed] [Google Scholar]