Updates on malaria epidemiology and profile in Cabo Verde from 2010 to 2019: the goal of elimination

Abstract

Background: Located in West Africa, Cabo Verde is an archipelago consisting of nine inhabited islands. Malaria has been endemic since the settlement of the islands during the sixteenth century and is poised to achieve malaria elimination in January 2021. The aim of this research is to characterize the trends in malaria cases from 2010 to 2019 in Cabo Verde as the country transitions from endemic transmission to elimination and prevention of reintroduction phases.

Methods: All confirmed malaria cases reported to the Ministry of Health between 2010 and 2019 were extracted from the passive malaria surveillance system. Individual-level data available included age, gender, municipality of residence, and the self-reported countries visited if travelled within the past 30 days, therby classified as imported. Trends in reported cases were visualized and multivariable logistic regression used to assess risk factors associated with a malaria case being imported and differences over time.

Results: A total of 814 incident malaria cases were reported in the country between 2010 and 2019, the majority of which were Plasmodium falciparum. Overall, prior to 2017, when the epidemic occurred, 58.1% (95% CI 53.6-64.6) of infections were classified as imported, whereas during the post-epidemic period, 93.3% (95% CI 86.9-99.7) were imported. The last locally acquired case was reported in January 2018. Imported malaria cases were more likely to be 25-40 years old (AOR: 15.1, 95% CI 5.9-39.2) compared to those under 15 years of age and more likely during the post-epidemic period (AOR: 56.1; 95% CI 13.9-225.5) and most likely to be reported on Sao Vicente Island (AOR = 4256.9, 95% CI = 260-6.9e+4) compared to Boavista.

Conclusions: Cabo Verde has made substantial gains in reducing malaria burden in the country over the past decade and are poised to achieve elimination in 2021. However, the high mobility between the islands and continental Africa, where malaria is still highly endemic, means there is a constant risk of malaria reintroduction. Characterization of imported cases provides useful insight for programme and enables better evidence-based decision-making to ensure malaria elimination can be sustained.

Keywords: Imported infections; Prevention of reintroduction; Surveillance.

Fig. 1

The location of Cabo Verde (a) shown in red off the coast of Senegal, in reference to continental Africa. Total number of locally acquired (b) and imported malaria cases (c) in Cabo Verde between 2010 and 2019 by municipality

Fig. 2

The total number of malaria cases (a), imported infections (b) and deaths (c) per year. The different colours within each bar represent the number of events reported by each island, with each bar labelled with the total number of cases per year

Fig. 3

Global map showing the likely origin of imported infections that were reported in Cabo Verde between 2010 and 2019. The size of the circle is scaled according to the number of cases likely originating in that country, with the different colours shown to differentiate the different countries. The location of Cabo Verde is shown as the black circles and connector lines shown in light grey

Fig. 4

Estimated annual R0 according to the ratio of imported to local cases resported for Cabo Verde (a) and Santiago Island only (b) where there were sufficient cases (min 10 cases required for models) per year to obtain estimates. The y-axis presents the maximum estimate of R0 that is plausible based on the data with year presented on the x-axis. The red dashed line shows where R0 equals 1 whereby above this line transmission is increasing and below, transmission is expected to die out