Modelling Lymphatic Filariasis Transmission and Control: Modelling Frameworks, Lessons Learned and Future Directions

Stolk, Wilma A.; Stone, Chris; Vlas, Sake J. de

doi:10.1016/bs.apar.2014.12.005

Cited by 31 publications

(25 citation statements)

References 58 publications

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“…This measure was taken to represent the time that could guarantee elimination with a reasonable level of certainty, but does not preclude that shorter durations may be sufficient in many areas. However, the discrepancy between predicted MDA durations and those advocated by GPELF was also evident in previous estimates with both deterministic and stochastic LF transmission models [ 41 ]. While aggressive goals for disease elimination and eradication potentially propel campaigns forward, overly optimistic projections could stifle innovations and further investment, ultimately hindering the initiative.…”

Section: Discussionmentioning

confidence: 85%

What Is Needed to Eradicate Lymphatic Filariasis? A Model-Based Assessment on the Impact of Scaling Up Mass Drug Administration Programs

et al. 2015

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BackgroundLymphatic filariasis (LF) is a neglected tropical disease for which more than a billion people in 73 countries are thought to be at-risk. At a global level, the efforts against LF are designed as an elimination program. However, current efforts appear to aim for elimination in some but not all endemic areas. With the 2020 goal of elimination looming, we set out to develop plausible scale-up scenarios to reach global elimination and eradication. We predict the duration of mass drug administration (MDA) necessary to reach local elimination for a variety of transmission archetypes using an existing model of LF transmission, estimate the number of treatments required for each scenario, and consider implications of rapid scale-up.MethodologyWe have defined four scenarios that differ in their geographic coverage and rate of scale-up. For each scenario, country-specific simulations and calculations were performed that took into account the pre-intervention transmission intensity, the different vector genera, drug regimen, achieved level of population coverage, previous progress toward elimination, and potential programmatic delays due to mapping, operations, and administration.Principal FindingsOur results indicate that eliminating LF by 2020 is unlikely. If MDA programs are drastically scaled up and expanded, the final round of MDA for LF eradication could be delivered in 2028 after 4,159 million treatments. However, if the current rate of scale-up is maintained, the final round of MDA to eradicate LF may not occur until 2050.Conclusions/SignificanceRapid scale-up of MDA will decrease the amount of time and treatments required to reach LF eradication. It may also propel the program towards success, as the risk of failure is likely to increase with extended program duration.

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Section: Discussionmentioning

confidence: 85%

What Is Needed to Eradicate Lymphatic Filariasis? A Model-Based Assessment on the Impact of Scaling Up Mass Drug Administration Programs

et al. 2015

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“…Mathematical modelling has played a part in understanding the transmission dynamics of lymphatic filariasis for many decades (see review by Stolk et al [ 4 ]). These models have shown that both reductions in mosquito biting rates and MDA have the potential to reduce and even break transmission of LF, but have also highlighted the importance of ensuring transmission has truly been broken and maintaining vector control to prevent bounce-back of infection.…”

Section: Introductionmentioning

confidence: 99%

Modelling strategies to break transmission of lymphatic filariasis - aggregation, adherence and vector competence greatly alter elimination

et al. 2015

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BackgroundWith ambitious targets to eliminate lymphatic filariasis over the coming years, there is a need to identify optimal strategies to achieve them in areas with different baseline prevalence and stages of control. Modelling can assist in identifying what data should be collected and what strategies are best for which scenarios.MethodsWe develop a new individual-based, stochastic mathematical model of the transmission of lymphatic filariasis. We validate the model by fitting to a first time point and predicting future timepoints from surveillance data in Kenya and Sri Lanka, which have different vectors and different stages of the control programme. We then simulate different treatment scenarios in low, medium and high transmission settings, comparing once yearly mass drug administration (MDA) with more frequent MDA and higher coverage. We investigate the potential impact that vector control, systematic non-compliance and different levels of aggregation have on the dynamics of transmission and control.ResultsIn all settings, increasing coverage from 65 to 80 % has a similar impact on control to treating twice a year at 65 % coverage, for fewer drug treatments being distributed. Vector control has a large impact, even at moderate levels. The extent of aggregation of parasite loads amongst a small portion of the population, which has been estimated to be highly variable in different settings, can undermine the success of a programme, particularly if high risk sub-communities are not accessing interventions.ConclusionEven moderate levels of vector control have a large impact both on the reduction in prevalence and the maintenance of gains made during MDA, even when parasite loads are highly aggregated, and use of vector control is at moderate levels. For the same prevalence, differences in aggregation and adherence can result in very different dynamics. The novel analysis of a small amount of surveillance data and resulting simulations highlight the need for more individual level data to be analysed to effectively tailor programmes in the drive for elimination.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-015-1152-3) contains supplementary material, which is available to authorized users.

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“…Insecticide treated-bed nets (ITNs) and sleeping in indoor residual sprayed houses (IRS) could reduce contact between humans (especially microfilariae carriers) and mosquito vectors [8]. Treatment still remains the first line of defense to combat the disease, despite uncertainty about the microfilarial prevalence threshold level below which transmission cannot be sustained even in the absence of any treatments [3, 9]. …”

Section: Introductionmentioning

confidence: 99%

“…Compartmental mathematical models of lymphatic filariasis abound in the literature [6, 9–11]. Two general simulation models of lymphatic filariasis transmission and control used to support decision-making are - the population-based deterministic model (EPIFIL) [12, 13] and - the individual-based stochastic model (LYMFASIM) [14].…”

Section: Introductionmentioning

confidence: 99%

Mathematical analysis of a lymphatic filariasis model with quarantine and treatment

et al. 2017

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BackgroundLymphatic filariasis is a globally neglected tropical parasitic disease which affects individuals of all ages and leads to an altered lymphatic system and abnormal enlargement of body parts.MethodsA mathematical model of lymphatic filariaris with intervention strategies is developed and analyzed. Control of infections is analyzed within the model through medical treatment of infected-acute individuals and quarantine of infected-chronic individuals.ResultsWe derive the effective reproduction number, and its interpretation/investigation suggests that treatment contributes to a reduction in lymphatic filariasis cases faster than quarantine. However, this reduction is greater when the two intervention approaches are applied concurrently.ConclusionsNumerical simulations are carried out to monitor the dynamics of the filariasis model sub-populations for various parameter values of the associated reproduction threshold. Lastly, sensitivity analysis on key parameters that drive the disease dynamics is performed in order to identify their relative importance on the disease transmission.

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Modelling Lymphatic Filariasis Transmission and Control: Modelling Frameworks, Lessons Learned and Future Directions

Cited by 31 publications

References 58 publications

What Is Needed to Eradicate Lymphatic Filariasis? A Model-Based Assessment on the Impact of Scaling Up Mass Drug Administration Programs

What Is Needed to Eradicate Lymphatic Filariasis? A Model-Based Assessment on the Impact of Scaling Up Mass Drug Administration Programs

Modelling strategies to break transmission of lymphatic filariasis - aggregation, adherence and vector competence greatly alter elimination

Mathematical analysis of a lymphatic filariasis model with quarantine and treatment

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