Figure 3

Time in years for resistant parasites to reach a frequency of 50% as a function of the level of treatment, f, and the basic reproductive number of untreated-sensitive infections, R _o . Equations (6) and (7) were integrated with only sensitive parasites until an equilibrium was reached. Then a resistant parasites were introduced at a frequency of 10^-4 and the equations were integrated until the frequency of resistance reached 50%. The parameters used to integrate the equations were: δ = 0.01 year^-1, μ = 36.5 year^-1 (ca. 0.1 day^-1), τ = 0.03 years (ca. 10 days), a = 100 year^-1 (ca. 1/3 day^-1), ω = 2 years, r _SU = 1 year^-1, r _ST = 10 year^-1 (ca. 1 month^-1) and r _R = 5 year^-1. The mosquito density m was calculated from equation (5) and the given parameters. For these parameters the cost of resistance Γ is 5 and the threshold frequency f _o is 0.89.