Feasibility of controlling hookworm infection through preventive chemotherapy: a simulation study using the individual-based WORMSIM modelling framework

Abstract

BackgroundGlobally, hookworms infect 440 million people in developing countries. Especially children and women of childbearing age are at risk of developing anaemia as a result of infection. To control hookworm infection and disease (i.e. reduce the prevalence of medium and heavy infection to <1 %), the World Health Organization has set the target to provide annual or semi-annual preventive chemotherapy (PC) with albendazole (ALB) or mebendazole (MEB) to at least 75 % of all children and women of childbearing age in endemic areas by 2020. Here, we predict the feasibility of achieving <1 % prevalence of medium and heavy infection, based on simulations with an individual-based model.MethodsWe developed WORMSIM, a new generalized individual-based modelling framework for transmission and control of helminths, and quantified it for hookworm transmission based on published data. We simulated the impact of standard and more intense PC strategies on trends in hookworm infection, and explored the potential additional impact of interventions that improve access to water, sanitation, and hygiene (WASH). The individual-based framework allowed us to take account of inter-individual heterogeneities in exposure and contribution to transmission of infection, as well as in participation in successive PC rounds.ResultsWe predict that in low and medium endemic areas, current PC strategies (including targeting of WCBA) will achieve control of hookworm infection (i.e. the parasitological target) within 2 years. In highly endemic areas, control can be achieved with semi-annual PC with ALB at 90 % coverage, combined with interventions that reduce host contributions to the environmental reservoir of infection by 50 %. More intense PC strategies (high frequency and coverage) can help speed up control of hookworm infection, and may be necessary in some extremely highly endemic settings, but are not a panacea against systematic non-participation to PC.ConclusionsControl of hookworm infection by 2020 is feasible with current PC strategies (including targeting of WCBA). In highly endemic areas, PC should be combined with health education and/or WASH interventions.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-1151-4) contains supplementary material, which is available to authorized users.

Impact of Different Sampling Schemes for Decision Making in Soil-Transmitted Helminthiasis Control Programs

“…The second approach is to use transmission models to predict the distribution of infection intensities over time during PC and combine these with a statistical model for the distribution of egg counts in stool samples and slides [15]. This is the subject of ongoing work for both STH and schistosomiasis within the NTD Modelling Consortium, which focuses on the development of transmission models that realistically account for heterogeneity in exposure to transmission and uptake of PC in populations to make policy-relevant predictions of the impact of control efforts [18][19][20][21][22][23][24].…”

Deworming Women of Reproductive Age During Adolescence and Pregnancy: What is the Impact on Morbidity From Soil-transmitted Helminths Infection?

“…The reason is that the FoI cannot be inferred from the cohort model itself because the reservoir of infection for STH transmission is contributed to by the entire community, and not just the cohort of interest. The FoIs have been extracted from two different individual-based stochastic transmission dynamics models of STH infection developed at Imperial College London (ICL) [7] and Erasmus MC (EMC), Rotterdam [8]. The cohort model itself does not take into account reductions in the FoI due to treating WRA.…”

“…Details of the two transmission dynamics models have been published previously [7,8,11]. Unlike the cohort model, the fully stochastic individual-based STH transmission models represent age-structured human populations.…”

The Case for Maternal Postpartum Deworming

“…Specific targets include at least 75% coverage of PC in SAC and pre-SAC living in endemic areas. However, recent predictive modelling suggests that current PC efforts targeting children may not be sufficient to meet the 2020 goal of controlling STHs without improving coverage and including WRA, particularly in regions where hookworm infection predominates [6]. …”