A mathematical model of the dynamics of lymphatic filariasis in Caraga Region, the Philippines

Abstract

Despite being one of the first countries to implement mass drug administration (MDA) for elimination of lymphatic filariasis (LF) in 2001 after a pilot study in 2000, the Philippines is yet to eliminate the disease as a public health problem with 6 out of the 46 endemic provinces still implementing MDA for LF as of 2018. In this work, we propose a mathematical model of the transmission dynamics of LF in the Philippines and a control strategy for its elimination using MDA. Sensitivity analysis using the Latin hypercube sampling and partial rank correlation coefficient methods suggests that the infected human population is most sensitive to the treatment parameters. Using the available LF data in Caraga Region from the Philippine Department of Health, we estimate the treatment rates r 1 and r 2 using the least-squares parameter estimation technique. Parameter bootstrapping showed small variability in the parameter estimates. Finally, we apply optimal control theory with the objective of minimizing the infected human population and the corresponding implementation cost of MDA, using the treatment coverage γ as the control parameter. Simulation results highlight the importance of maintaining a high MDA coverage per year to effectively minimize the infected population by the year 2030.

A game-theoretic model of lymphatic filariasis prevention

“…We consider the situation at the hypothetical termination of the MDA treatments. We adapt an ODE compartmental model for LF transmission that was introduced in [ 27 ]. Their compartmental model simplified by the absence of MDA but extended by the presence of exposed vectors is shown and described in Fig 2 .…”

“…Image courtesy of Public Health Image Library, Centers for Disease Control and Prevention ( https://phil.cdc.gov/Details.aspx?pid=3425 ). (b) Scheme of the ODE compartmental model for LF transmission from [ 27 ] with no treatment (after the termination of MDA). The human population is divided into uninfected U h , latent L h , and infectious I h ; the total population is N h = U h + L h + I h .…”

“…We adopt most parameter values from [ 27 ] and references therein. All rates are expressed per capita per week.…”

“…As in [ 39 ], we set the mosquito death rate as δ v = 0.1. In line with [ 27 ], to keep the mosquito population to be a constant multiple of N h , we set b v = δ v + b h − δ h . The number of mosquitoes per humans was estimated as n v = 3.…”

“…In our paper, we adapt a SEI-SI compartmental model by [ 27 ] which investigated the effect of MDA on LF transmission in the Philippines. Unlike previous LF modeling papers, we focus our attention on what happens when MDA is terminated and no longer in place.…”