A mathematical model for tilapia lake virus transmission with waning immunity

Abstract

The goal of this paper is to investigate the influence of the waning immunity on the dynamics of Tilapia Lake Virus (TiLV) transmission in wild and farmed tilapia within freshwater. We formulate a model for which susceptible individuals can contract the disease in two ways: (i) direct mode caused by contact with infected individuals; (ii) indirect mode due to the presence of pathogenic agents in the water. We obtain an age-structured model which combines both age since infection and age since recovery. We derive an explicit formula for the reproductive number ${\mathcal{R}}_0$ and show that the disease-free equilibrium is locally asymptotically stable when, ${\mathcal{R}}_0<1$. We discuss on the form of the waning immunity parameter and show numerically that a Hopf bifurcation may occur for suitable immunity parameter values, which means that there is a periodic solution around the endemic equilibrium when, ${\mathcal{R}}_0>1$.

Keywords:

• Age-structured model
• tilapia lake virus (TiLV)
• basic reproduction number
• stability
• waning immunity

Mathematics Subject Classifications:

• 45K05
• 45M10
• 92D25
• 92D30

Acknowledgments

The authors are very grateful to the editors and the anonymous referees for their valuable comments and suggestions, which helped us to improve significantly the presentation of this work.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was funded by a grant from the African Institute for Mathematical Sciences, www.nexteinstein.org, with financial support from the Government of Canada, provided through Global Affairs Canada, www.international.gc.ca, and the International Development Research Centre, www.idrc.ca.