Eco-epidemiology of Lassa fever: a mathematical modeling approach

Abstract

Lassa fever, a fatal zoonotic hemorrhagic disease caused by the Lassa virus, persists as a significant health concern in West Africa. Despite ongoing efforts to mitigate its impact, both the incidence and mortality rates remain alarmingly high, posing a potential risk of a global spread. Recent studies have focused on understanding the dynamic behaviour of Lassa fever. However, the ecological relationship between the reservoir host (rodents) and humans, involving factors such as rodent predation and migration, remains inadequately understood. In this study, we developed and analysed a non-linear mathematical compartmental model for Lassa fever, incorporating both human and rodent populations together with an infested environment. Rodent predation was modelled using the Holling type II functional response. We rigorously established key properties of the model, including the existence of solutions, boundedness, and positivity. The reproduction number (R₀) was determined using the next-generation method. Additionally, a sensitivity analysis of model parameters was conducted, utilising the Normalized Forward Sensitivity Index to identify the most influential processes affecting the disease threshold and critical factors for effective infection control. Numerical analysis of the total infected human population performed using the odeint function in Python programming revealed several insights. Notably, human-to-human transmission became predominant when the contact rate exceeded 50%. The infected human population experienced a drastic decline when the rate of rodent migration exceeded 50%. In addition, we observed that rodent predation led to an initial surge in human infections. The findings of this study underscore the importance of implementing strategies that prioritise minimising environmental transmission, human-to-human contact, mitigating rodent predation, and increasing rodent migration to effectively control and prevent the transmission of Lassa fever.