Mathematical modelling in tuberculosis transmission and impact on early intervention (chemoprophylaxis) in Malaysia / Nurhuda Ismail ... [et al.]

Background: Tuberculosis remains as one of the highest unresolved disease burden among re-emerging diseases in Malaysia for the last twenty years. With current treatment protocol emphasizing among the infectives, we seek to find if combination treatment of these active cases with lsoniazid Preventive Therapy for high risk latent tuberculosis infection groups among non-HIV population would give greater impact on reducing incidence.

Methods: Our study aims to apply the use of infectious disease modelling to study the progression of latent tuberculosis infection among non-HIV population in Malaysia, and to assess the impact of lsoniazid as preventive therapy on reducing incidence. We present a deterministic compartmental age-structured tuberculosis model which incorporates treatment of infectives as well as the preventive therapy. The model assumes that latently infected individuals develop active disease as a result of primary infection, endogenous reactivation and exogenous reinfection. We start by formulating and analyzing the model without any intervention strategy then, we extend to incorporate the preventive therapy and treatment of infectives. The epidemic thresholds known as reproduction numbers and equilibria for the model are determined, and stabilities analyzed. The reproduction numbers for the model are compared to assess the possible community benefits achieved by treatment of infectives, preventive therapy and a holistic approach of combination of both intervention strategies. The model then further quantifies the effectiveness of preventive therapy for early latent tuberculosis infection and demonstrates how effective the therapy has to be to eliminate tuberculosis, when use in conjunction with treatment for active tuberculosis.

Results: Our analyses show that treatment of infectives is more effective in the first years of implementation of preventive therapy as treatment results in clearing active tuberculosis immediately and there after preventive therapy will do better in controlling the number of infectives due to reduced progression to infectious state.

Conclusion: Our model suggests that lsoniazid Preventive Therapy which identify and treat persons recently infected may have a substantial effect on controlling tuberculosis epidemics in Malaysia.