Anopheles drivers of persisting malaria transmission in Guna Yala, Panamá: an operational investigation

Abstract

Background Though most of Panamá is free from malaria, localized foci of transmission persist, including in the Guna Yala region. Government-led entomological surveillance using an entomological surveillance planning tool (ESPT) sought to answer programmatically-relevant questions that would enhance the understanding of both local entomological drivers of transmission and gaps in protection that result in persisting malaria transmission to guide local vector control decision-making. Methods The ESPT was used to design a sampling plan centered around the collection of minimum essential indicators to investigate the relevance of LLINs and IRS in the communities of Permé and Puerto Obaldía, Guna Yala, as well as to pinpoint any remaining spaces and times where humans are exposed to Anopheles bites (gaps in protection). Adult Anopheles were collected at three time points via human landing catches (HLCs), CDC Light Traps (LT), and pyrethrum spray catches (PSCs) during the rainy and dry seasons. Mosquitoes were identified to species via molecular methods. Insecticide susceptibility testing of the main vector species to fenitrothion was conducted. Results In total, 7537 adult Anopheles were collected from both sites. Of the 493 specimens molecularly confirmed to species, two thirds (n = 340) were identified as Nyssorhynchus albimanus, followed by Anopheles aquasalis. Overall Anopheles human biting rates (HBRs) were higher outdoors than indoors, and were higher in Permé than in Puerto Obaldía: nightly outdoor HBR ranged from 2.71 bites per person per night (bpn) (Puerto Obaldía), to 221.00 bpn (Permé), whereas indoor nightly HBR ranged from 0.70 bpn (Puerto Obaldía) to 81.90 bpn (Permé). Generally, peak biting occurred during the early evening. The CDC LT trap yields were significantly lower than that of HLCs and this collection method was dropped after the first collection. Pyrethrum spray catches resulted in only three indoor resting Anopheles collected. Insecticide resistance (IR) of Ny. albimanus to fenitrothion was confirmed, with only 65.5% mortality at the diagnostic time. Conclusion The early evening exophagic behaviour of Anopheles vectors, the absence of indoor resting behaviours, and the presence of resistance to the primary intervention insecticide demonstrate limitations of the current malaria strategy, including indoor residual spraying (IRS) and long-lasting insecticidal nets (LLINs), and point to both gaps in protection and to the drivers of persisting malaria transmission in Guna Yala. These findings highlight the need for continued and directed entomological surveillance, based on programmatic questions, that generates entomological evidence to inform an adaptive malaria elimination strategy.

Comparison of PvLAP5 and Pvs25 qRT-PCR assays for the detection of Plasmodium vivax gametocytes in field samples preserved at ambient temperature from remote malaria endemic regions of Panama

“…For instance, hurricanes, and other extreme weather events such as the “El Niño Southern Oscillation (ENSO)”, which was particularly strong during 2018-2019 in the region [ 66 ], have been associated with changes in malaria transmission in Panama and the Caribbean [ 5 ]. However, we cannot rule out that other factors, such as increased case detection due to the introduction of Malaria RDTs by the Panamanian Ministry of Health in 2017 [ 1 ], changes in vectorial behaviour [ 67 ] and transmission efficiency [ 68 , 69 ], reintroduction of parasites [ 4 , 6 ], waning immunity due to lack of exposure [ 70 ], socioeconomic factors [ 8 ], or prolonged confinement experienced by the population for the control of COVID-19 during 2020, might have all or in part, contributed to its development.…”

Entomological Surveillance Planning Tool (ESPT)-generated actionable evidence on human and vector behaviours optimizes present interventions and reduces exposure to Anopheles vectors in two communities of Guna Yala, Panamá

“…Adult mosquito collections from two communities of Guna Yala confirmed the predominance of Ny. albimanus in the area [ 14 ].…”

“…The Entomological Surveillance Planning Tool (ESPT) [ 14 , 22 ] is a decision-support tool for designing question-based entomological surveillance activities utilizing minimum essential indicators to facilitate cost effective, locally tailored, and evidence-based vector control. The ESPT enables NMCPs to quantify gaps in protection [ 23 ].…”

“…The ESPT enables NMCPs to quantify gaps in protection [ 23 ]. In Panama, the ESPT was used to guide the formulation of programmatic questions and to design an entomological surveillance plan that addresses these questions [ 14 ]. This paper describes the methods and results of an ESPT-based plan to investigate whether LLINs are an appropriate intervention in Guna Yala and to pinpoint the remaining gaps in protection, based on the integration of adult Anopheles bionomics data with HBO data.…”

A Follow-Up to the Geographical Distribution of Anopheles Species in Malaria-Endemic and Non-Endemic Areas of Honduras

“…Each anopheline species displays different bionomic traits that are relevant to malaria epidemiology, such as feeding preference, endophagic/exophagic behaviour, resting behaviour, larval habitat preference, etc. [ 9 , 10 , 11 , 12 , 13 ]. For instance, An.…”