The existence of variation in the ability to withstand a given pathogen burden is also of more than academic interest.
As plant scientists have argued [2], artificial increases in tolerance by selective breeding may be more evolution-proof than manipulations in resistance, because tolerance does not impose selection for pathogen countermeasures.
By analogy, public or animal health interventions that increase tolerance may be less likely to fail in the face of pathogen evolution than are interventions that increase resistance.
In agricultural animals, attempts to select for increased yield in the face of parasite challenge may come to nothing (or even make things worse) if there is a trade-off between resistance and tolerance.
Thus, explicit analyses of the tolerance component of host defense are bound to be useful – and interesting. Not least, we should soon know whether tolerance is as important as resistance in determining the fate of infected animals.