Interventions targeting vector survival, such as insecticide spraying, increase the likelihood of immune pre-sensitisation through pre-exposure to vector saliva.

<p>Shown are the equilibrium abundances in the ODE model of (a) susceptible (<i>V<sub>S</sub></i>; blue), exposed (<i>V<sub>E</sub></i>; purple) and infectious (<i>V<sub>I</sub></i>; red) vectors, and (b) infected hosts that are not pre-exposed (<i>H<sub>I</sub></i>; red) and that are pre-exposed (; pink) to vector saliva. Here, the x-axis is the daily rate of vector mortality imposed by vector control. Pre-sensitised and naïve infected hosts are assumed to have identical recovery rates (<i>γ<sub>H</sub></i> = <i>γ<sub>H′</sub></i> = 60<sup>−1</sup> per day) and transmission probabilities (<i>T<sub>HV</sub></i> = <i>T<sub>H′V</sub></i> = <i>T<sub>VH</sub></i> = <i>T<sub>VH′</sub></i> = 0.5). Note that the force of infection from vectors, <i>rT<sub>HV</sub>V<sub>I</sub></i>, is proportional to the abundance of infectious vectors, and the rate of immune pre-sensitisation through vector saliva pre-exposure, <i>rP<sub>HV</sub></i>(<i>V<sub>S</sub></i> + <i>V<sub>E</sub></i> + (1 − <i>T<sub>HV</sub></i>)<i>V<sub>I</sub></i>), is roughly proportional to the abundance of susceptible vectors (notice that <i>V<sub>S</sub></i> is at least one order of magnitude larger than <i>V<sub>E</sub></i> or <i>V<sub>I</sub></i>).</p>