Quantifying Seasonal and Diel Variation in Anopheline and Culex Human Biting Rates in Southern Ecuador

Ryan, Sadie J.; Lippi, Catherine A.; Boersch‐Supan, Philipp H.; Heydari, Naveed; Silva, Mercy; Adrian, Jefferson; Noblecilla, Leonardo F.; Ayala, Efraín Beltrán; Encalada, Mayling D.; Larsen, David A.; Krisher, Jesse T; Krisher, Lyndsay; Fregosi, Lauren; Stewart-Ibarra, Anna M.

doi:10.1101/192773

Cited by 4 publications

(6 citation statements)

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“…A second plausible explanation for possible dry-season malaria transmission might include human behavioural factors ensuring continued exposure to malaria vectors such that a Plasmodium reservoir is maintained within the communities [29]. However, the detection of Plasmodium in collected mosquitoes was not conducted in this investigation because in low transmission settings, sporozoite detection in even large samples of Anopheles may be an inefficient use of limited resources as it is highly unlikely to detect, if any, a statistically representative sample of Plasmodium-positive specimens [50].…”

Section: Discussionmentioning

confidence: 99%

“…Furthermore, sporozoite detection is not required from an operational perspective; MINSA does not require vector infection rates or vector incrimination data to inform vector control strategies when endemic Anopheles species are already known and characterized vectors. Instead, in low transmission settings such as Guna Yala, quantifying location-specific Anopheles landing rates is a more resource-effective and accurate way of estimating disease risk [50]. Thus, the higher landing rates observed in Permé suggest that this community has the potential to be more vulnerable to Plasmodium infections, which may inform intervention strategies and prioritization for this area.…”

Section: Discussionmentioning

confidence: 99%

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

Ávila¹,

Vajda

Gutiérrez

et al. 2021

Malar J

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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.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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

Ávila¹,

Vajda

Gutiérrez

et al. 2021

Malar J

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“…calderoni. Nyssorhynchus albimanus, a primary vector of malaria in Central and South America (including Ecuador) [17,36,[52][53][54][55][56][57], has location-specific bionomic traits [58]. Similar to behaviours seen here, Ny.…”

Section: Discussionmentioning

confidence: 73%

“…Data generated in Southern Ecuador indicate variation in seasonal vector species composition and temporal biting behaviour [17]. Nyssorhynchus albimanus (formerly Anopheles albimanus) demonstrated exophilic and exophagic behaviour with variation in these behaviours based on geography [17]. Data on vector species composition, human biting rate (HBR) and interventionrelevant behaviour of vectors from other endemic areas remain limited.…”

mentioning

confidence: 99%

Anopheline and human drivers of malaria risk in northern coastal, Ecuador: a pilot study

Martin

Hendershot

Portilla

et al. 2020

Malar J

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Background Understanding local anopheline vector species and their bionomic traits, as well as related human factors, can help combat gaps in protection. Methods In San José de Chamanga, Esmeraldas, at the Ecuadorian Pacific coast, anopheline mosquitoes were sampled by both human landing collections (HLCs) and indoor-resting aspirations (IAs) and identified using both morphological and molecular methods. Human behaviour observations (HBOs) (including temporal location and bed net use) were documented during HLCs as well as through community surveys to determine exposure to mosquito bites. A cross-sectional evaluation of Plasmodium falciparum and Plasmodium vivax infections was conducted alongside a malaria questionnaire. Results Among 222 anopheline specimens captured, based on molecular analysis, 218 were Nyssorhynchus albimanus, 3 Anopheles calderoni (n = 3), and one remains unidentified. Anopheline mean human-biting rate (HBR) outdoors was (13.69), and indoors (3.38) (p = 0.006). No anophelines were documented resting on walls during IAs. HBO-adjusted human landing rates suggested that the highest risk of being bitten was outdoors between 18.00 and 20.00 h. Human behaviour-adjusted biting rates suggest that overall, long-lasting insecticidal bed nets (LLINs) only protected against 13.2% of exposure to bites, with 86.8% of exposure during the night spent outside of bed net protection. The malaria survey found 2/398 individuals positive for asymptomatic P. falciparum infections. The questionnaire reported high (73.4%) bed net use, with low knowledge of malaria. Conclusion The exophagic feeding of anopheline vectors in San Jose de Chamanga, when analysed in conjunction with human behaviour, indicates a clear gap in protection even with high LLIN coverage. The lack of indoor-resting anophelines suggests that indoor residual spraying (IRS) may have limited effect. The presence of asymptomatic infections implies the presence of a human reservoir that may maintain transmission.

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“…Mosquitoes are a major public health concern because they vector agents that cause important diseases such as Zika, dengue, chikungunya, yellow fever, West Nile, and malaria. The activity patterns of mosquitoes play a large role in the transmission of mosquito‐borne diseases (Leming et al , Ryan et al , Jayakrishnan et al ). Due to ethical and biosafety concerns for the protection of personnel involved in the sampling of mosquito vectors in disease‐endemic zones, alternative methods are being developed to replace the technique that uses humans as bait during field entomological surveillance (Veronesi et al , Casas‐Martinez et al ).…”

Section: Introductionmentioning

confidence: 99%

Diel activity patterns of adult female mosquitoes (Diptera: Culicidae) determined by a novel rotated trap in northeastern Florida, U.S.A.

Chao¹,

Zhu²,

Dixon

et al. 2019

Journal of Vector Ecology

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A novel rotator trap was evaluated to determine the diel activity patterns and physiological state of adult female mosquitoes in St. Augustine, FL, U.S.A. Culex nigripalpus were most active from 19:00‐21:00, followed by 1:00‐3:00, based on collections from the novel rotator trap. Furthermore, analysis of the physiological state of female mosquitoes collected by the novel rotator trap suggested that non‐parous (nulliparous) host‐seeking mosquitoes were more frequently active in the 21:00‐23:00 and 09:00‐19:00 time frames. Parous host‐seeking mosquitoes were more frequently collected from 19:00‐21:00 and 1:00‐3:00. A low abundance of gravid females was collected by the rotator trap, so analysis of their activity periods was inconclusive. These results indicate that the novel rotated trap could be used to detect the diel activity patterns of adult mosquitoes in mosquito control programs and more testing should be conducted in the future.

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Quantifying Seasonal and Diel Variation in Anopheline and Culex Human Biting Rates in Southern Ecuador

Abstract: Background

Cited by 4 publications

References 44 publications

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

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

Anopheline and human drivers of malaria risk in northern coastal, Ecuador: a pilot study

Diel activity patterns of adult female mosquitoes (Diptera: Culicidae) determined by a novel rotated trap in northeastern Florida, U.S.A.

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