Elsevier

Acta Tropica

Volume 222, October 2021, 106065
Acta Tropica

Improving the efficiency of the BG sentinel 2 trap to assess the activity of Aedes (Stegomyia) aegypti [Linnaeus, 1762] in Senegal

https://doi.org/10.1016/j.actatropica.2021.106065Get rights and content

Highlights

  • We boosted the efficacy of BG-Sentinel trap with mice to catch Aedes aegypti in Senegal.

  • Daily activity rhythm of Aedes aegypti populations were investigated taking into account seasons in a peri-urban area of Senegal.

  • BG-Sentinel traps baited with BG-Lure and three mice were more efficient to collect Aedes aegypti populations.

  • Daily activity of Aedes aegypti was bimodal depending on environmental parameters.

Abstract

The use of efficient mosquito sampling methods in vector surveillance programs is crucial to inform control actions and prevent outbreaks. amongst existing trapping methods, the BG sentinel trap is widely used for collecting mosquitoes from the subgenus Stegomyia. However, studies state that the BG-sentinel trap underestimates the relative abundance of mosquito vectors. In this study, we used mice to enhance the effectiveness of the BG-sentinel trap to collect Aedes aegypti (Linnaeus) and follow the species’ daily abundance under local conditions. The Latin square method was used to compare different combinations in three different seasons. Of the 35,107 mosquitoes collected, Ae. aegypti (53.82%) and Culex quinquefasciatus (46.07%) were dominant. The combination of BG-Lure + 3 mice captured more Ae. aegypti individuals (apparent density per trap/day (ADT = 187.65 ± 133.53; p < 0.001) followed by the 3 mice-baited BG-sentinel trap (ADT = 163.47 ± 117.32), the BG-sentinel trap without attractant (ADT = 74.15 ± 117.07) and the BG-sentinel trap + BG-Lure (ADT = 47.1 ± 115.91). Aedes aegypti showed two peaks of activity in the day, one following the sunrise and one before the sunset, influenced by temperature and relative humidity. Our study suggests the use of mice to enhance the efficiency of the BG-Sentinel trap to catch Ae. aegypti. However, its application in large scale entomological monitoring programs should be difficult because of ethical and operational constraints.

Introduction

Mosquito-borne diseases cause significant health and economic burdens on the countries where they are present (Aubry et al., 2019; WHO, 2014). With globalization and environmental changes, many tropical and subtropical countries are facing major public health crisis linked to the emergence / re-emergence of diseases linked to vector-borne pathogens (Aubry et al., 2019). Vector-borne diseases (VBD) are responsible for more than 17% of infectious diseases and cause more than one million deaths each year worldwide (Bhatt et al., 2013). In inter-tropical areas, VBDs are more numerous and cause the highest morbidity and mortality rates (Duvallet et al., 2017). Mosquitoes represent the main arthropod vectors that transmit pathogens of medical and veterinary interest worldwide such as malaria, lymphatic filariasis, and arboviruses. Aedes (Stegomyia) mosquitoes are involved in the transmission of viruses of global importance such as Zika, Chikungunya and Dengue fever viruses that have emerged or re-emerged in several regions (Schuffenecker et al., 2006; Weaver et al., 2016) during the last 10 years. Bhatt et al. (2013) estimated that up to 390 million DENV infections, including nearly 100 million cases of dengue disease manifestations, occur annually worldwide in over 100 endemic countries located mainly in the Asia-Pacific and Americas-Caribbean regions. The four dengue virus (DENV) serotypes are present in Africa (Amarasinghe et al., 2011) where dengue is endemic in 34 countries (Gaye et al., 2019) and could become a serious public health problem (Caron et al., 2013). In Senegal, an outbreak has been reported in 2018 in eight regions (MSAS, 2018). Aedes aegypti, L. has been identified as the vector for the Dengue virus in Senegal because of numerous isolates of DEN-3 strains (Dia et al., 2012).

Vector control remains the main option to prevent outbreaks since no vaccines or specific treatments exist against these pathogens (Basso et al., 2015; Guarner and Hale, 2019). Vector control programs have traditionally focused on reducing mosquito populations by the uncontrolled use of insecticides, leading increasingly the development of insecticide resistance in certain mosquito species, including Aedes aegypti (Dia et al., 2012; Dusfour et al., 2011). Indeed, Aedes aegypti shows moderate to severe resistance to the majority of insecticide classes tested, including organochlorines (DDT), organophosphates (temephos, malathion), synthetic pyrethroids (deltamethrin) and carbamates (Faucon et al., 2015). Significant efforts are being made currently to develop alternative methods (Auteri et al., 2018). The Sterile Insect Technique (SIT), a component of Area-Wide Integrated Pest Management (AW-IPM), is one of the most effective and environmentally respectful vector control strategies against insect pests of agricultural and medical/veterinary importance (Benelli et al., 2014; Diiro et al., 2020; Govindarajan et al., 2016). This technique is a genetic suppression strategy that involves releasing a large number of sterile male insects into a wild population of the same species to mate with females to reduce the reproduction (Dyck et al., 2005). The success of such a control program depends on the ability of sterile irradiated males to survive, disperse and compete with wild males to mate with wild females (Balestrino et al., 2017). The implementation of the sterile insect technique or similar methods requires the collection of field data on the targeted vector. This will use adequate sampling and trapping tools and standardised procedures. Furthermore, parameters such as population densities, daily and seasonal abundance, distribution, and/or survival of targeted vector species need to be assessed during the entomological monitoring phases. A good trapping tool is needed to access all this information (Kröckel et al., 2006).

Traps have been developed for the monitoring of mosquitoes, for example, the Zumba™ Mosquito Trap (Bhalala and Arias, 2009) and BG-Sentinel trap (Bhalala and Arias, 2009; Kröckel et al., 2006; Maciel-de-Freitas et al., 2006). The BG-Sentinel traps (BioGents, Regensburg, Germany) initially developed for the sampling of Aedes aegypti (Maciel-de-Freitas et al., 2006) using a combination of visual cues, convection currents, and olfactory signals (BG-Lure) (BioGents GmbH, Regensburg, Germany) (Irish et al., 2008; Kröckel et al., 2006). The BG-Lure consists of synthetic components such as lactic acid, ammonia and caproic acid (hexanoic acid) that mimic the odour of human skin and attracts Aedes vectors (Geier et al., 2006). Thereby, the BG-Sentinel traps baited with BG-Lure as attractant are considered the gold standard for collecting Aedes mosquitoes (Kröckel et al., 2006; Wilke et al., 2019). However, the effectiveness of this trapping tool involves many questions and need to be improved using natural or synthetic olfactory products since it was establish that the BG-Sentinel trap baited with BG-Lure underestimates the richness and abundance of mosquito species (Lacroix et al., 2009; Wilke et al., 2019). Many studies have been conducted to improve these weaknesses by using different baits associated with BG-Lure (Irish et al., 2008; Owino et al., 2015; Wilke et al., 2019; Williams et al., 2006). However, these baits are not always available in certain localities mainly due to constraints in manufacturing. To avoid these difficulties Lacroix et al. (2009) and Le Goff et al. (2016) improved the effectiveness of this trap using mice to collect Aedes albopictus, Skuse. To our knowledge, such studies have never conducted in Ae. aegypti.

Therefore, we hypothesised whether adding mice in the BGS trap improve its effectiveness for collecting Ae. aegypti. Thus, the objective of this study was to enhance the effectiveness of BG-Sentinel traps for collecting Aedes aegypti and to follow the daily activity rhythm of this species in the urban area of Dakar Senegal, according to environmental changes during three seasons.

Section snippets

Study area

The study was conducted at the Laboratoire National de l'Elevage et de Recherches Vétérinaires (LNERV) of the Institut Sénégalais de Recherches Agricoles (ISRA) of Dakar-Hann in Senegal (14.722969, −17.434227). The LNERV is located close to the Parc de Hann, a forested and swampy area of 0.6 km2 in the urban city of Dakar, Senegal. The study area consisted of some dwellings located on the southwest side and buildings that served as administrative offices and laboratories located on the

Results

A total of 35,107 mosquitoes belonging to three genera (Aedes, Anopheles and Culex) and four species (Aedes aegypti, Anopheles gambiae Giles, Culex quinquefasciatus, Say and Culex tritaeniorhynchus, Giles) were collected by the different combinations in 144 trap-days (Table 1). Bartlett's test of sphericity was significant (χ2=23.459, df=3, p = 3.239 e-5). Aedes aegypti was the most abundant species with 53.82% (n = 18,895 individuals of which 10,593 were males and 8302 were females)

Discussion

The BG-Sentinel trap is known to be specific for sampling mosquitoes from the subgenus Stegomyia notably Ae. aegypti and Ae. albopictus, and Culex quinquefasciatus (Kröckel et al., 2006; Li et al., 2016; Maciel-de-Freitas et al., 2006). It was confirmed by our study in which the mosquitoes collected were mainly Ae. aegypti (53.82%) and Cx. quinquefasciatus (46.07%) (Table 1). As previously shown by Lacroix et al. (2009) and Le Goff et al. (2016), species from the genus Stegomyia and Culex

Conclusions

To our knowledge, this study is the first to describe the daily activity rhythm of Ae. aegypti populations taking into account seasonality in a peri‑urban area of Senegal. The BG-Lure and three mice-baited BG-Sentinel traps show efficacy to collect Ae. Aegypti and by the way could be used to study abundance, dispersal, longevity as well as monitoring of Ae. aegypti populations. Our findings pointed out a bimodal daily activity of Ae. aegypti populations that depends on environmental parameters.

Author contributions

“Conceptualization, GD and AGF; methodology, GD; AGF software, GD; BB; and MC; validation, MTS, AGF and MC; formal analysis, GD; BB; and MC.; investigation, GD; BF; resources, GD, BF.; data curation, GD, BF; writing—original draft preparation, GD.; writing—review and editing, GD, BF, MTB, BB, MTS, MC and AGF.; visualization, GD and BB; supervision, AGF; project administration, AGF; funding acquisition, AGF. All authors have read and agreed to the published version of the manuscript.”

Declaration of Competing Interest

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Funding: Acknowledgements

The authors would like to thank Mrs. Mireille Bassène for their help in data collection and Gorgui Faye the responsible of the LNERV animal facility. Authors are grateful to International Atomic Energy Agency (IAEA) for their financial support to the implementation of this study.

References (57)

  • Bates, D., Mächler, M., Bolker, B., Walker, S., 2014. Fitting linear mixed-effects models using lme4. arXiv preprint...
  • Benelli, G., Canale, A., Conti, B., 2014. Eco-friendly contro strategies against the asian tiger mosquito, Aedes...
  • U.R. Bernier et al.

    Laboratory comparison of aedes aegypti attraction to human odors and to synthetic human odor compounds and blends1

    J. Am. Mosq. Control Assoc.

    (2007)
  • H. Bhalala et al.

    The Zumba™ mosquito trap and BG-Sentinel™ trap: novel surveillance tools for host-seeking mosquitoes

    J. Am. Mosq. Control Assoc.

    (2009)
  • S. Bhatt et al.

    The global distribution and burden of dengue

    Nature

    (2013)
  • D. Canyon et al.

    Efficacy of carbon dioxide, 1-octen-3-ol, and lactic acid in modified Fay-Prince traps as compared to man-landing catch of Aedes aegypti

    J. Am. Mosq. Control Assoc.

    (1997)
  • M. Caron et al.

    First evidence of simultaneous circulation of three different dengue virus serotypes in Africa

    PLoS ONE

    (2013)
  • M. Casas Martínez et al.

    A new tent trap for monitoring the daily activity of Aedes aegypti and Aedes albopictus

    J. Vector Ecol.

    (2013)
  • D.D. Chadee et al.

    Landing periodicity of Aedes aegypti with implications for dengue transmission in Trinidad, West Indies

    J. Vector Ecol.

    (2000)
  • M. Cornet et al.

    Données bio-écologiques sur les vecteurs potentiels du. Virus amaril au Sénégal oriental. Rôle des différentes espéces dans la transmission du virus

    Cah Orstom (Entomol méd Parasitol)

    (1978)
  • P.A. Cornillon et al.

    Statistiques Avec R. 2e édition augmentée, Presses universitaires De Rennes ed

    (2010)
  • I. Dia et al.

    Insecticide susceptibility of Aedes aegypti populations from Senegal and Cape Verde Archipelago

    Parasite Vector

    (2012)
  • N. Diagne et al.

    Les anopheles du Sénégal

    Bull. Soc. Pathol. Exot.

    (1994)
  • S. Diarrassouba et al.

    Rythme d'activité atypique chez Aedes aegypti en zone de savane sub-soudanienne de Côte d'Ivoire

    Bull. Soc. Pathol. Exot

    (1997)
  • G.M. Diiro et al.

    Are Individuals Willing to Pay for Community-Based Eco-Friendly Malaria Vector Control Strategies? A Case of Mosquito Larviciding Using Plant-Based Biopesticides in Kenya

    Sustainability

    (2020)
  • I. Dusfour et al.

    Multiple insecticide resistance in Aedes aegypti (Diptera: culicidae) populations compromises the effectiveness of dengue vector control in French Guiana

    Mem. Inst. Oswaldo Cruz

    (2011)
  • G. Duvallet et al.

    Entomologie Médicale Et vétérinaire. Editions Quae

    (2017)
  • V. Dyck et al.

    Sterile Insect technique: Principles and Practice in Area-Wide Integrated Pest Management

    (2005)
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