Background
Methods
Biting ecology
Response Type | Ecological equivalent | Parametric conditions | Vector behaviour |
---|---|---|---|
Type I | Holling’s Type I | α = 1 β = 1 | Indiscriminate, or vector biting that is consistent (proportionate) across relative availabilities of alternative hosts |
Type II | Holling’s Type II | α < 1 β ≥ 1 | An anthropophilic vector which takes most of its blood meals on humans even when humans are less available than other hosts, and when humans and non-humans are equally available, almost all blood meals are taken from humans |
Type III | Holling’s Type III | α ≥ 1 β > 1 | This is the pattern expected with a learned behaviour, such that female mosquitoes learn to prefer the more common Type of host |
Type IV | Inversion of Holling’s Type II | α > 1 β ≤ 1 | A zoophilic vector is disinclined to bite humans until they constitute all but the only available blood source |
Type V | Inversion of Holling’s Type III | α ≤ 1 β < 1 | HBI saturates and becomes relatively invariant when humans and non-humans are at similar availability. This is analogous to ‘negative prey switching’ whereby the ‘predator’ consumes disproportionately less of the more available ‘prey’ [45]. Eventually, when non-humans become vanishingly rare, the HBI is forced to increase sharply to unity |
Epidemiological model
Definition | Value [cited literature] | |
---|---|---|
b
H
| Transmission coefficient (vectors → hosts) = bite rate (day−1) × transmission probability | 0.1 = 1/3 × 0.3 [47] |
b
V
| Transmission coefficient (hosts → vectors) = bite rate (day−1) × transmission probability | 0.007 = 1/3 × 0.02 [48] |
m
| Ratio of vectors to humans | Varied in simulations; values in figure legends |
ε
| Clearance rate of symptomatic infection (day−1) | 1/200 [49] |
κ
| Clearance rate of asymptomatic infection (day−1) | 1/200 [49] |
θ
| Level of reduced susceptibility to secondary infection | 0.5 (assumed) |
τ
| Full susceptibility reversion rate (day−1) | 1/1000 [50] |
μ
H
| Birth and death rate of humans (day−1) (i.e., stable population) | 1/21,900 (assumed) |
μ
V
| Birth (or maturation) and death rate of vectors (day−1) (i.e., stable population) | 1/10 [51] |
σ
| Adjustment factor for asymptomatic transmissibility to vector | 0.25 [52] |
ζ
| Rate of parasite development within vector (day−1) | 1/10 [53] |