What impact will the achievement of the current World Health Organisation targets for anthelmintic treatment coverage in children have on the intensity of soil transmitted helminth infections?

Table 1 Parameter values estimated using maximum likelihood methods and used in the numerical evaluations of model predictions for each parasite

Parameter	Ascaris	Trichuris	Hookworm	Source
Basic Reproductive number, R₀	2.12	1.72	2.34	Fitted
Adult worm life expectancy	1 year	1 year	2 years	[12]
Negative binomial clumping parameter, k	0.90	0.38	0.35	Fitted
Density dependence fecundity parameter, ɣ	0.07	0.0035	0.08	Fitted
Age-specific transmission parameter, β_i for age group i’s contact with infectious reservoir. Relative egg contribution by age, ρ_i, proportional to β_i.	0.22, 1.88, 1, 0.53	0.5, 2.13, 1, 0.28	0.03, 0.09, 1, 2.5	Fitted
Drug efficacy as a proportion of worms killed by Albendazole	0.99	0.50	0.95	[14]
Source of age - mean intensity profile for fitting	Elkins et al. South India [15]	Bundy et al. St Lucia [20]	Bradley et al. Zimbabwe [17]	-

The age intensity profiles from the cited sources based on worm expulsion were used to derive estimate of R₀, β_i and k. The values of ɣ were derived from egg per gram of faeces and worm expulsion counts [transmission age groups: Ascaris and hookworm: 0–2;2–5;5–15;15+; Trichuris: 0–2;2–7;7–12;12+]

ISSN: 1756-3305