"A mathematical model of the dynamics of lymphatic filariasis in Caraga Region, The Philippines"
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 and its elimination using MDA in the Philippines. Using the computed basic reproduction number R0, we show that the disease-free equilibrium E0 of the model system is locally asymptotically stable when R0 < 1 and unstable when R0 > 1, whereas the endemic equilibrium E* is locally asymptotically stable when R0 > 1. Sensitivity analysis using the Latin Hypercube Sampling and Partial Rank Correlation Coefficient method 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 (DOH), we estimate the treatment rates r1, r2 using the least squares parameter estimation technique. 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. This work is envisioned to be protocol-directing and policy-making. As there are still several endemic areas in the Philippines and other tropical countries in the Southeast Asia and Western Pacific regions, this study could help the DOH and other ministries of health in designing more effective implementation approaches for MDA to achieve LF elimination in the near future.