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Determination of the Processes Driving the Acquisition of Immunity to Malaria Using a Mathematical Transmission Model

Figure 4

Observed and Predicted Patterns of Infectivity (Gametocytaemia) by Age in Tanzania and in The Gambia

(A) Predicted infectivity by age from the model with different immunity functions. If1= immunity function 1 (susceptibility to clinical disease); If2 = immunity function 2 (clearance of detectable parasites); If3 = immunity function 3 (clearance of subpatent infection), If2* denotes EIR-independent version of If2. Parasitaemia is calculated in the model as symptomatic cases plus asymptomatic infections (DH+AH). All runs assume an annual EIR = 40 ibppy and that parameters are as before (Table 1), except cD is adjusted (for If2 and If3) to make comparable the curves corresponding to different immunity function models.

(B–D) Observed gametocytaemia by age from (B) the low altitude area of region 2 in Tanzania, (C) The Gambia south of the river bank, and (D) The Gambia north of the river bank. Parameters for the model are annual EIR = 110 (B), 50 (C), 15 (D), infectivity CD = 0.3 as before (B,D), 0.4 (C), percentage treated f = 50%. All other parameters are as in Table 1.

Figure 4

doi: https://doi.org/10.1371/journal.pcbi.0030255.g004