Animal Models: No Model Is Perfect, but Many Are Useful

Full evaluation of the interactions between a virus and host during infection and clearance requires a living organism. A live animal is also necessary for development of vaccines requiring evaluation of immunogenicity and an immune response that protects from challenge. Study of the natural host for the virus is ideal, but often not possible. Mice have emerged over the last 60 years as the most popular animal model for studying viral pathogenesis due to extensive genetic and immunologic characterization, wide availability of reagents, inbred and transgenic strains, and small size. However, responses in mice are not always predictive of those in the natural host. Other species commonly used include guinea pigs, ferrets, chickens, and nonhuman primates. When choosing an animal model for a study, factors to be considered include host susceptibility to the infection, animal size, cost, availability of housing and reagents, potential confounding coinfections, and ethical restrictions.