Table 2.
Host population H = ∑n k = 0
h
k is divided into burden strata {h
k} by their worm load (w = # adult worms): k Δw ≤ w < (k + 1)Δw for h
k. The partition is determined by worm-step Δw ≥ 1, that serves as hypothetical mating threshold. So h
0 are infection-free (no mated couples), while for h
k (k ≥ 1) its mated count (expected number of couples) given by function (Eq. 1). The transitions among strata
are determined by force of infection (FOI) λ (= rate of worm accumulation/Δw), resolution rates γ k = k γ (γ - mean worm mortality), and population turnover rate μ (mortality, maturation, migration, etc.). Source terms S k represent demographic inputs from related population groups, e.g. for children S 0 = b H (birth rate), with S k ≥ 1 = 0 (as all newborns are infection-free); whereas adult sources come from maturing child strata. For the interested reader, a version of the SWB model programmed in Mathematica software is provided as Additional file 1 |