An epidemiological and intervention assessment of the malaria epidemic in Bolívar, Venezuela: a modelling study
Authors: Huber John H. , Chaves Luis F. , Siraj Amir S. , Moreno Jorge E. , Guevara Maria Eugenia , Villegas Maria , Pocaterra Leonor , Villegas Leopoldo , Perkins T. Alex 
Published: May 2022

Background

Venezuela has experienced an explosive resurgence in Plasmodium falciparum and Plasmodium vivax malaria incidence over the last decade due to various social, political, and economic factors. To ensure national and regional progress towards malaria elimination, there is an urgent need to better understand the epidemiological dynamics of this malaria outbreak at its epicenter in the southern state of Bolívar and to identify the sets of interventions that may be necessary to reduce transmission and incidence.

Methods

We fitted transmission models of P. falciparum and P. vivax to weekly incidence data in Bolívar, Venezuela during 2000-2018. We estimated the magnitude of local transmission for both Plasmodium spp. and inferred the contribution of relapses and reinfections to P. vivax incidence in the region. Compared to a business-as-usual scenario, we projected the impact of different interventions on Plasmodium spp. incidence during the period 2021-2023.

Findings

We estimated that 63·7 – 73·3% of all P. vivax infections in Bolívar are relapses, leading to as many as 51,800 observed relapses misclassified per year as reinfections in the routine surveillance data. Our estimates suggest that the reproduction number remains close to one for both Plasmodium spp., pointing towards the feasibility of control. Long-lasting insecticidal nets (LLINs) were projected to cause greater proportional reductions in P. falciparum incidence than P. vivax incidence, and mass drug administration (MDA) with an 8-aminoquinoline and a blood-stage partner drug was projected to cause the greatest reduction in P. vivax incidence, provided that adherence rates were high.

Interpretation

Control of the malaria outbreak in Southeastern Venezuela is feasible, should appropriate resources to support surveillance and control be brought to bear. Coupling the distribution of LLINs and a focal MDA with an 8-aminoquinoline and a blood-stage partner drug may lead to the greatest reduction in malaria incidence.

Funding

National Science Foundation; University of Notre Dame; National Institute of General Medical Sciences (grant number 1R35GM143029-01 to TAP);

RESEARCH IN CONTEXT

Evidence before the study

We searched PubMed, bioRxiv, and medRxiv for articles in English published on or before May 25th, 2021 using the following keywords: “Venezuela”, “malaria”, AND “model*”. Previous studies have applied statistical models to characterize the relationship between malaria incidence and climate in Venezuela, concluding that the reproduction number is low and suggesting the feasibility of control. A study fitting a mechanistic transmission model to epidemiological data to allow for projecting the impact of alternative approaches to control has not been performed.

Added value of the study

We fitted Plasmodium falciparum and Plasmodium vivax transmission models to 20 years of weekly incidence data to estimate the transmission of both Plasmodium spp. and characterize the contribution of relapses and reinfections to P. vivax incidence in Bolívar, Venezuela. We also projected the likely impact of interventions in the region under alternative scenarios about control.

Implications of the available evidence

The burden of Plasmodium vivax relapses in Bolívar is underestimated from routine surveillance data, so control interventions must target the hypnozoite reservoir in the region. Mass drug administration (MDA) is projected to be impactful for both Plasmodium spp., though tradeoffs between coverage and adherence suggest that a focal MDA with an 8-aminoquinoline and a blood-stage partner drug may yield the greatest impact.