Mathematical models of the population biology of Ostertagia ostertagi and Teladorsagia circumcincta, and the economic evaluation of disease control strategies.

The construction and use of mathematical models of the population biology of Ostertagia ostertagi and Teladorsagia circumcincta is discussed. Simulated field trials implemented by deterministic mathematical models currently share with actual field trials the disadvantage that they convey no information concerning the risk associated with the net return demonstrated by the trial. This has important implications when it is necessary to rank disease control strategies in order of usefulness.