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. 2011 Jul 7:10:184.
doi: 10.1186/1475-2875-10-184.

Outdoor host seeking behaviour of Anopheles gambiae mosquitoes following initiation of malaria vector control on Bioko Island, Equatorial Guinea

Michael R Reddy  1 , Hans J Overgaard, Simon Abaga, Vamsi P Reddy, Adalgisa Caccone, Anthony E Kiszewski, Michel A Slotman
Affiliations

Outdoor host seeking behaviour of Anopheles gambiae mosquitoes following initiation of malaria vector control on Bioko Island, Equatorial Guinea

Michael R Reddy et al. Malar J. .

Abstract

Background: Indoor-based anti-vector interventions remain the preferred means of reducing risk of malaria transmission in malaria endemic areas around the world. Despite demonstrated success in reducing human-mosquito interactions, these methods are effective solely against endophilic vectors. It may be that outdoor locations serve as an important venue of host seeking by Anopheles gambiae sensu lato (s.l.) mosquitoes where indoor vector suppression measures are employed. This paper describes the host seeking activity of anopheline mosquito vectors in the Punta Europa region of Bioko Island, Equatorial Guinea. In this area, An. gambiae sensu stricto (s.s.) is the primary malaria vector. The goal of the paper is to evaluate the importance of An gambiae s.l. outdoor host seeking behaviour and discuss its implications for anti-vector interventions.

Methods: The venue and temporal characteristics of host seeking by anopheline vectors in a hyperendemic setting was evaluated using human landing collections conducted inside and outside homes in three villages during both the wet and dry seasons in 2007 and 2008. Additionally, five bi-monthly human landing collections were conducted throughout 2009. Collections were segregated hourly to provide a time distribution of host-seeking behaviour.

Results: Surprisingly high levels of outdoor biting by An. gambiae senso stricto and An. melas vectors were observed throughout the night, including during the early evening and morning hours when human hosts are often outdoors. As reported previously, An. gambiae s.s. is the primary malaria vector in the Punta Europa region, where it seeks hosts outdoors at least as much as it does indoors. Further, approximately 40% of An. gambiae s.l. are feeding at times when people are often outdoors, where they are not protected by IRS or LLINs. Repeated sampling over two consecutive dry-wet season cycles indicates that this result is independent of seasonality.

Conclusions: An. gambiae s.l. mosquitoes currently seek hosts in outdoor venues as much as indoors in the Punta Europa region of Bioko Island. This contrasts with an earlier pre-intervention observation of exclusive endophagy of An. gambiae in this region. In light of this finding, it is proposed that the long term indoor application of insecticides may have resulted in an adaptive shift toward outdoor host seeking in An. gambiae s.s. on Bioko Island.

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Figures

Figure 1
Figure 1
Map of study villages in Punta Europa, Bioko Island, Equatorial Guinea. Also indicated is Sacriba, the location of the collections made by Molina et al [5].
Figure 2
Figure 2
Time segregated human collections in Punta Europa, 2007 and 2008. Error bars represent standard error of the proportion.
Figure 3
Figure 3
Proportion of anophelines collected indoors and outdoors in Punta Europa, 2007 and 2008. Error bars represent standard error of the proportion.
Figure 4
Figure 4
Time segregated human collections in the village of Mongola, 2009. Error bars represent standard error of the proportion.
Figure 5
Figure 5
Hourly human landing collections by season and venue in Mongola, Punta Europa, Bioko Island, 2009. Error bars represent the standard error of the mean.
Figure 6
Figure 6
Mean number of anophelines collected indoors and outdoors in Mongola, Punta Europa, Bioko Island, 2009. Error bars represent the standard error of the mean.
See this image and copyright information in PMC

References

    1. Kleinschmidt I, Sharp B, Benavente L, Schwabe C, Torrez M, Kuklinski J, Morris N, Raman J, Carter J. Reduction in infection with Plasmodium falciparum one year after the introduction of malaria control interventions on Bioko Island, Equatorial Guinea. Am J Trop Med Hyg. 2006;74:972–978. - PubMed
    1. Kleinschmidt I, Schwabe C, Benavente L, Torrez M, Ridl FC, Segura JL, Ehmer P, Nchama GN. Marked increase in child survival after four years of intensive malaria control. Am J Trop Med Hyg. 2009;80:882–888. - PMC - PubMed
    1. Kleinschmidt I, Torres M, Schwabe C, Benavente L, Seocharan I, Jituboh D, Nseng G, Sharp B. Factors influencing the effectiveness of malaria control in Bioko Island, Equatorial Guinea. Am J Trop Med Hyg. 2007;76:1027–1032. - PMC - PubMed
    1. Sharp BL, Ridl FC, Govender D, Kuklinski J, Kleinschmidt I. Malaria vector control by indoor residual insecticide spraying on the tropical island of Bioko, Equatorial Guinea. Malar J. 2007;6:52. doi: 10.1186/1475-2875-6-52. - DOI - PMC - PubMed
    1. Molina R, Benito A, Blanca F, Roche J, Otunga B, Alvar J. The anophelines of Equatorial Guinea: Etholology and susceptibility studies. Res Rev Parasitol. 1996;56:105–110.

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