Transmission Models and Management of Lymphatic Filariasis Elimination

Modeling the Impact and Costs of Semiannual Mass Drug Administration for Accelerated Elimination of Lymphatic Filariasis

“…Many countries have made great strides, and some have stopped MDA, but no country that had ongoing transmission of LF in 2000 has been verified to have interrupted transmission of the infection using MDA [4]. Modeling is a powerful tool for decision making in infectious disease control [30], but predictions are subject to uncertainty [31]. An important uncertainty in our study concerns the efficacy of drugs.…”

Heterogeneous dynamics, robustness/fragility trade-offs, and the eradication of the macroparasitic disease, lymphatic filariasis

“…While the current WHO-led global initiative advocating the application of annual single-dose mass drug administration (MDA) for 4–6 years to eradicate the vector-borne macroparasitic disease, lymphatic filariasis (LF), from all 73 endemic countries represents one of the largest global health programs devised to reduce the burden of tropical diseases [ 1 , 2 ], a critical challenge to parasite eradication is the heterogeneous transmission of the disease across endemic regions [ 3 – 6 ]. We have previously shown that such environmental and geographic variability in parasite transmission between communities may reflect the impacts of significant site-specific variations in initial ecological conditions and transmission parameters [ 7 – 9 ]; i.e. that observed infection patterns do not merely reflect noise clouding an inherently non-spatial transmission equilibrium [ 10 ], but represent significant sensitivity to spatial and temporal variations in the key socioecological drivers of transmission across a region [ 8 , 11 ].…”

“…While impacts of heterogeneities in ecological and environmental factors on the transmission dynamics of vector-bone parasitic diseases, including malaria, filariasis, schistosomiasis and onchocerciasis, are a topic of growing study [ 5 , 6 , 8 , 11 , 22 , 24 ], their interactions with public health interventions by contrast is only now beginning to be appreciated [ 11 , 25 – 28 ]. Our previous work on LF transmission heterogeneity, for example, has highlighted the complex outcomes that such interactions may have for efforts aiming to achieve the elimination of parasitic disease [ 7 – 9 , 11 , 17 ]. An important finding in this regard is that while heterogeneous parasite transmission dynamics across a region may reflect strong system adaptations to site-specific environmental factors, this sensitivity to one set of localized conditions may also make a locally robustly adapted parasite system particularly fragile to perturbations that may significantly alter the variables that constrain and govern the local transmission dynamics [ 11 ].…”

“…In this study, our overarching goal is to examine how site-specific heterogeneity in LF transmission might affect the probability of eliminating this parasitic disease both regionally and globally using existing disease control strategies. The basis of our work is the use of a Bayesian data-model assimilation (DA) framework that facilitates both the simultaneous fitting and parameterization of vector-specific LF transmission models to parallel cross-sectional human infection and vector abundance data assembled from community field surveys [ 8 , 9 , 11 , 30 , 31 ], and the effective use of the resulting best-fitting model ensembles for undertaking numerical investigations of the effects of between-site heterogeneity on LF transmission and extinction dynamics, and the impact that this variability may have on infection outcomes in response to the mass drug and vector intervention strategies currently advocated for interrupting parasite transmission in different LF endemic settings. In addition, following recent advances in investigating the parameter structure of complex dynamical models, we also examine the parameter space and behaviour of the locally fitted models to develop new theoretical understanding regarding how such characteristics may be linked to LF transmission robustness and adaptation to the local environment, the impact that such associations may have on parasite response to perturbations, and on the ability of models to make reliable macroscopic predictions [ 32 – 34 ].…”

Continental-Scale, Data-Driven Predictive Assessment of Eliminating the Vector-Borne Disease, Lymphatic Filariasis, in Sub-Saharan Africa by 2020

“…The first result of import is the finding that simply increasing VC coverage to 80% under existing MDA coverages will not accelerate the meeting of LF elimination at the country level (Table 5). This is unsurprising, given that insecticide bed net coverages used in the baseline simulations across the majority of IUs within the present countries were already at values as high as 60% on average; as we highlighted before [12,64,65], increasing VC coverages by moderate amounts when MDA coverages are already at moderately high levels will not lead to significant impacts on timelines to elimination due to the inherently greater impact of chemotherapy versus VC in reducing LF infection. By contrast, but for the same reason, switching to MDA based either on biannual drug delivery or annual IDA regimens significantly accelerated the achievement of parasite elimination in all countries.…”