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Table 2 Notation, definition and values of model parameters

From: Modelling Neglected Tropical Diseases diagnostics: the sensitivity of skin snips for Onchocerca volvulus in near elimination and surveillance settings

Symbol Definition Value and units References
x ij Number of microfilariae in the ith skin snip biopsy from body site j (shoulder, hip or calf) Data from each participant [24, 3034]
d ij Weight of the i th skin snip biopsy from body site j (shoulder, hip or calf) See Table 1, in mg [24, 3033]
ε* Rate of production of microfilariae per (mated) fertile worm per mg of skin 1.1538 year-1 [41]
m * ij Mean number of microfilariae per skin snip at baseline For the mean number of mf/mg for each site and setting see Table 1  
k m Aggregation (overdispersion) parameter of skin microfilariae Estimated by fitting the model, see Table 3  
μ m Per capita rate of microfilarial mortality 0.8 year-1 [38, 39]
w Number of adult (mated) fertile female worms harboured by the host Unobserved, assumed to be linearly related to microfilarial load [39]
θ W Mean number of adult (mated) fertile female worms per host Unobserved, estimated by fitting the model, see Table 3  
k W Aggregation (overdispersion) parameter of adult female worms Estimated by fitting the model, see Table 3  
α = ε *1 /ε *2 Ratio of the rate of microfilarial arrival in a shoulder or calf skin snip to the rate in a snip from the iliac crest Estimated by fitting the model, see Table 3  
ρ Rate of resumption of microfilarial production 0.29 year-1 [40, 42]
t Time since last ivermectin treatment 1, 3, 5 years  
ζ The per dose reduction in female worm fertility caused by ivermectin treatment 0 [43]
0.07 [54]
0.35 [55]
n No. of (annual) ivermectin rounds to which a surviving (mated) female worm has been exposed 10  
x + The event that any of the skin snips taken from a host are positive