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Table 3 Random egg-release

From: Refined stratified-worm-burden models that incorporate specific biological features of human and snail hosts provide better estimates of Schistosoma diagnosis, transmission, and control

Egg release by mated females and individual hosts depends on worm fecundity ρ k , and mated-couple count ϕ k (for h k -stratum). The former is given by crowding function \( {\rho}_k={\rho}_0\;{e}^{-k/{k}_0} \), with maximal value ρ 0 and threshold k 0. The latter ϕ k can be estimated by assuming binomial sex-ratio distribution in the “w-strata” (w adult worms), Eq. (1). The predicted egg-release by h k -hosts, E k  = ρ k ϕ k , gives its mean (expected) value used as measure of host infectivity. The actual release should be random (NB) with mean E k and aggregation r k  = r ϕ k .

Individual egg-counts-counts by all SWB hosts (strata {h k }) generate a mixed NB-distribution (4), illustrated in the schematic plot above. Each simulated egg-test of SWB community is then a random sample of size H (sampled pool) drawn from distribution P SW