We considered sand flies in the susceptible (SF), latent (EF, not infectious), or infectious (IF) stages. Flies can become infected by blood meals taken on infectious humans (IHP, IHD, IHS, IHT1, IHT2, IHL). The infection rate λF of flies is determined by the following: 1) the biting rate β, 2) the infection probabilities of flies dependent on the infection status of the hosts (pF1 to pF4, see Table 2 ) and 3) the numbers of infectious hosts.
We assumed that each blood meal of a susceptible sand fly leads to a sand fly infection if taken from a symptomatically infected human (pF3 = 100% for KA patients IHS, IHT1, IHT2 and pF4 = 100% for PKDL patients IHL). For a sensitivity analysis, seeResults .
The probability that a fly becomes infected when feeding on asymptomatically infected hosts of type IHP or IHD was estimated with the model as follows. The infection probability pF2 of late asymptomatically infected humans (IHD) was estimated, whereby we assumed that the infectivity of hosts increases monotonically from the time of infection until the late asymptomatic state IHD. We defined an intermediate infection probability for flies originating from hosts in the early asymptomatic state IHP as pF1 = pF2/2.
We assumed that each blood meal of a susceptible sand fly leads to a sand fly infection if taken from a symptomatically infected human (pF3 = 100% for KA patients IHS, IHT1, IHT2 and pF4 = 100% for PKDL patients IHL). For a sensitivity analysis, see
The probability that a fly becomes infected when feeding on asymptomatically infected hosts of type IHP or IHD was estimated with the model as follows. The infection probability pF2 of late asymptomatically infected humans (IHD) was estimated, whereby we assumed that the infectivity of hosts increases monotonically from the time of infection until the late asymptomatic state IHD. We defined an intermediate infection probability for flies originating from hosts in the early asymptomatic state IHP as pF1 = pF2/2.
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