Abstract
Malaria burden on Bioko Island has decreased significantly over the past 15 years. The impact of interventions on malaria prevalence, however, has recently stalled. Here, we use data from island-wide, annual malaria indicator surveys to investigate human movement patterns and their relationship to Plasmodium falciparum prevalence. Using geostatistical and mathematical modelling, we find that off-island travel is more prevalent in and around the capital, Malabo. The odds of malaria infection among off-island travelers are significantly higher than the rest of the population. We estimate that malaria importation rates are high enough to explain malaria prevalence in much of Malabo and its surroundings, and that local transmission is highest along the West Coast of the island. Despite uncertainty, these estimates of residual transmission and importation serve as a basis for evaluating progress towards elimination and for efficiently allocating resources as Bioko makes the transition from control to elimination.
Highlights
Malaria burden on Bioko Island has decreased significantly over the past 15 years
Our findings showed that P. falciparum parasite rate (PfPR) was significantly higher in those who had traveled to mainland Equatorial Guinea (EG) than PfPR in all individuals, yet in individuals with history of within-island travel it was lower
In its fourth phase beginning in 2019, the Bioko Island Malaria Control Project (BIMCP) has redefined itself into the Bioko Island Malaria Elimination Project (BIMEP) to integrate new intervention strategies aiming to rid the island of malaria[22]
Summary
Malaria burden on Bioko Island has decreased significantly over the past 15 years. The impact of interventions on malaria prevalence, has recently stalled. We estimate that malaria importation rates are high enough to explain malaria prevalence in much of Malabo and its surroundings, and that local transmission is highest along the West Coast of the island. International travel accounts for much of the importation of parasites by humans returning from malaria endemic areas to non-endemic countries[12], but a very significant proportion of the human-related parasite movement takes place between regions of differing receptivity within an endemic country[6] Understanding these movements is fundamental for local control and elimination efforts[2,3,9]. We analyze infection prevalence and travel data assembled by the BIMCP as part of their annual malaria indicator surveys (MIS) to identify the patterns of human movement that can most significantly determine Plasmodium falciparum parasite importation. We find that the contribution of malaria infections acquired while travelling to local malaria prevalence on Bioko Island is significant and discuss its implications for the adoption of adequate and cost-effective malaria control strategies
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