it is unlikely that viability selection among parasites of the large sample inoculated could explain the variability among animals (at agiven temperature) in the exponential rate of infection progress after the third day.
Result of Your Query
viability selectionViabilitätsselektion (ger.)

Selection due to differential survival and death of individuals, in contrast to differential reproduction.
 1947

Thompson, P.E. & Winder, C.V. (1947). Analysis of saurian malarial infections as influenced by temperature. The Journal of Infectious Diseases 81, 8495: 91.
 1949

Linkage under differentialviabilityselection as well as polysomic inheritance are not easy problems.
Geiringer, H. (1949). On some mathematical problems arising in the development of Mendelian genetics. J. Amer. Stat. Assoc. 44, 526547: 544.
 1968

The cases involving viability selection treated here are new.
Karlin, S. (1968). Equilibrium behaviour of population genetic models with nonrandom mating. Part I: Preliminaries and special mating systems. J. appl. Probab. 5, 231313: 256.