Modelling the role of insecticide-treated bed-nets in the reduction of Lymphatic Filariasis
cases in the Gambia
Supervisors: Dr. Deirdre Hollingsworth, Dr. Mike Irvine, Prof Matt Keeling
Research objectives
The hypothesis to be investigated is that bed nets alone have big impact on the transmission of
lymphatic filariasis, and so the global elimination goals will be achieved in some areas more
quickly than current modeling suggests. The aim of the project will be to analyse data from
areas where transmission rates have fallen very quickly to try and estimate the impact of the
interventions on transmission, with a sub-aim to develop better models of the diagnostics used
to detect transmission and confirm elimination.
Research context & modelling considerations
Lymphatic filariasis (LF) is a debilitating disease caused by parasitic infection of the lymph
nodes, transmitted by mosquitoes. There are currently global efforts to eliminate the disease as
a public health problem by 2025 through the use of mass drug administration (MDA). However,
there remain open questions as to how bed-nets, which reduce both the density of mosquitoes
and the interaction between humans and mosquitoes, can impact the prevalence of LF, alone or
in conjunction with MDA.
The initial approach will be to extend an individual-based model of LF infection dynamics to
include behaviour associated with bed-net use [2]. This model will then be extended and
validated against novel data collected from the Gambia and the Solomon Islands (see below),
and informed by available data on bed net scale up in these areas [3].
This project will also involve improving the models of the diagnostic used to detect ongoing
transmission of LF. In many of these areas there is almost no detectable signal of transmission,
suggesting that not only has transmission been broken, but that the detectable antigens and
antibodies decay much more quickly than previously thought. Understanding these dynamics
will not only impact our interpretation of data in this area, but in designing detection metods for
confirming elimination elsewhere.
External collaboration and data
This project will be performed in close collaboration with Dr Pat Lammie from the Centres for
Disease Control, USA and the Task Force for Global Health, an international leader in LF
reserach. Dr Lammie collaborates with all the investigators through the NTD Modelling
Consortium. Serological data from the Gambia & Solomon Islands will be used. These regions
have vectors present, with very high prevalence. This is complimented with a vector control
dataset over the timeframe of the serological data.
Application to the real world: who will benefit?
The analyses in this MSc project will have direct implications for both control programmes (e.g.
the number of rounds of MDA required when bed net coverage is high) and surveillance
strategies for the confirmation of elimination of LF.
Avenues for PhD research
The project can be taken in a number of different directions, depending on the results of the
analysis and the interests of the student and collaborators. Potential avenues include
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Exploring the use of other forms of vector control on LF, such as indoor residual
spraying.
Modelling how the behaviour of mosquito species impacts the efficacy of vector control.
Modelling and dynamics of response to diagnostics in changing transmission.
Designing surveillance programmes for the detection of ongoing transmission and
confirming elimination.
References
[1] Bockarie, Moses J., et al. "Role of vector control in the global program to eliminate lymphatic
filariasis." Annual review of entomology 54 (2009): 469-487.
[2] Irvine, Michael A, et al. "Modelling strategies to break transmission of lymphatic filariasisaggregation, adherence and vector competence greatly alter elimination." Parasites & vectors
8.1 (2015): 1-19.
[3] Rebollo MP, Sambou SM, Thomas B, Biritwum N-K, Jaye MC, Kelly-Hope L, et al. (2015)
Elimination of Lymphatic Filariasis in The Gambia. PLoS Negl Trop Dis 9(3): e0003642.
doi:10.1371/journal.pntd.0003642