Resurgence risk for malaria, and the characterization of a recent outbreak in an Amazonian border area between French Guiana and Brazil

Abstract

Background: In 2017, inhabitants along the border between French Guiana and Brazil were affected by a malaria outbreak primarily due to Plasmodium vivax (Pv). While malaria cases have steadily declined between 2005 and 2016 in this Amazonian region, a resurgence was observed in 2017. Methods: Two investigations were performed according to different spatial scales and information details: (1) a local study on the French Guiana border, which enabled a thorough investigation of malaria cases treated at a local village health center and the entomological circumstances in the most affected neighborhood, and (2) a regional and cross-border study, which enabled exploration of the regional spatiotemporal epidemic dynamic. Number and location of malaria cases were estimated using French and Brazilian surveillance systems. Results: On the French Guianese side of the border in Saint-Georges de l'Oyapock, the attack rate was 5.5% (n = 4000), reaching 51.4% (n = 175) in one Indigenous neighborhood. Entomological findings suggest a peak of Anopheles darlingi density in August and September. Two female An. darlingi (n = 1104, 0.18%) were found to be Pvpositive during this peak. During the same period, aggregated data from passive surveillance conducted by Brazilian and French Guianese border health centers identified 1566 cases of Pv infection. Temporal distribution during the 2007-2018 period displayed seasonal patterns with a peak in November 2017. Four clusters were identified among epidemic profiles of cross-border area localities. All localities of the first two clusters were Brazilian. The localization of the first cluster suggests an onset of the outbreak in an Indigenous reservation, subsequently expanding to French Indigenous neighborhoods and non-Native communities.

Contributing to Elimination of Cross-Border Malaria Through a Standardized Solution for Case Surveillance, Data Sharing, and Data Interpretation: Development of a Cross-Border Monitoring System

“…The Amapá state, meanwhile, has seen the number of cases increase by 23%. French Guiana experienced a significant increase of malaria case numbers for the same period, especially in the municipalities at the border with Brazil [ 33 ].…”

“…On the other hand, in French Guiana, the health system does not benefit from the action of community health workers. Moreover, Brazil systematically gives primaquine to patients with P vivax —except for specific cases including pregnancy—which significantly reduces the risk of relapses, whereas prior glucose-6-phosphate dehydrogenase testing is required in French Guiana, which tends to restrict and delay the use of primaquine [ 33 , 35 ]. This situation makes French Guiana more likely to observe P vivax relapses than Brazil.…”

Vector-Focused Approaches to Curb Malaria Transmission in the Brazilian Amazon: An Overview of Current and Future Challenges and Strategies

“…Transmission of malaria among miners (garimpeiros) is greatly affected by their constant mobility and a work regime that coincides with the peak of biting activity of vector mosquitoes. Populations of border towns are generally more vulnerable, especially those living in remote areas, as recently observed along the border between French Guiana and Brazil where local inhabitants were affected by a malaria outbreak [38]. Recent events in Venezuela, causing mass migrations, have been responsible for an increase in malaria transmission across the frontier between Brazil and Venezuela [31,32].…”

Vector-focused Approaches to Curb Malaria Transmission in the Brazilian Amazon: An Overview of Current and Future Challenges and Strategies

“…Transmission of malaria among miners (garimpeiros) is greatly affected by their constant mobility, and a work regime that coincides with the peak of biting activity of vector mosquitoes. Populations of border towns are generally more vulnerable, especially those living in remote areas, as recently observed along the border between French Guiana and Brazil where local inhabitants were affected by a malaria outbreak [37]. Recent events in Venezuela, causing mass migrations, has been responsible for an increase in malaria transmission across the frontier between Brazil and Venezuela [30,31].…”