Animal models of Francisella tularensis infection.

The increased incidence of emerging infections has caused a resurgence in the development of animal models in order to study their pathophysiology and develop therapeutics against them. Optimizing these models and improving our ability to extrapolate information from animals to humans is critical because in many cases the animal model will represent the only modality for efficacy testing. Francisella tularensis (F. tularensis) is an emerging pathogen that fits this category. While there is a significant body of literature that has examined infections with F. tularensis in a variety of species, the optimal small animal model has yet to be defined. A vast majority of studies have used two strains of F. tularensis, the more virulent type A strain commonly found in North America and the less virulent type B strain common to Europe. None of the small animal models described in the literature thus far behave in a fashion identical to humans with respect to their sensitivity to SCHU S4 (type A) or live vaccine strains (LVS) (attenuated type B) and an ability of LVS vaccination to consistently protect against a SCHU S4 aerosol challenge, suggesting that significant work on animal model development still remains. This report briefly describes the parameters important for animal model development and reviews the literature related to animal models of F. tularensis, including the human model, and the characterization performed for those models.