Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
. 2017 Dec 29;10(1):628.
doi: 10.1186/s13071-017-2598-2.

Dengue and yellow fever virus vectors: seasonal abundance, diversity and resting preferences in three Kenyan cities

Sheila B Agha  1   2 , David P Tchouassi  3 , Armanda D S Bastos  4 , Rosemary Sang  3   5
Affiliations

Dengue and yellow fever virus vectors: seasonal abundance, diversity and resting preferences in three Kenyan cities

Sheila B Agha et al. Parasit Vectors. .

Abstract

Background: The transmission patterns of dengue (DENV) and yellow fever (YFV) viruses, especially in urban settings, are influenced by Aedes (Stegomyia) mosquito abundance and behavior. Despite recurrent dengue outbreaks on the Kenyan coast, these parameters remain poorly defined in this and other areas of contrasting dengue endemicity in Kenya. In assessing the transmission risk of DENV/YFV in three Kenyan cities, we determined adult abundance and resting habits of potential Aedes (Stegomyia) vectors in Kilifi (dengue-outbreak prone), and Nairobi and Kisumu (no dengue outbreaks reported). In addition, mosquito diversity, an important consideration for changing mosquito-borne disease dynamics, was compared.

Methods: Between October 2014 and June 2016, host-seeking adult mosquitoes were sampled using CO2-baited BG-Sentinel traps (12 traps daily) placed in vegetation around homesteads, across study sites in the three major cities. Also, indoor and outdoor resting mosquitoes were sampled using Prokopack aspirators. Three samplings, each of five consecutive days, were conducted during the long-rains, short-rains and dry season for each city. Inter-city and seasonal variation in mosquito abundance and diversity was evaluated using general linear models while mosquito-resting preference (indoors vs outdoors) was compared using Chi-square test.

Results: Aedes aegypti, which comprised 60% (n = 7772) of the total 12,937 host-seeking mosquitoes collected, had comparable numbers in Kisumu (45.2%, n = 3513) and Kilifi (37.7%, n = 2932), both being significantly higher than Nairobi (17.1%, n = 1327). Aedes aegypti abundance was significantly lower in the short-rains and dry season relative to the long-rains (P < 0.0001). Aedes bromeliae, which occurred in low numbers, did not differ significantly between seasons or cities. Mosquito diversity was highest during the long-rains and in Nairobi. Only 10% (n = 43) of the 450 houses aspirated were found positive for resting Ae. aegypti, with overall low captures in all areas. Aedes aegypti densities were comparable indoors/outdoors in Kilifi; but with higher densities outdoors than indoors in Kisumu and Nairobi.

Conclusions: The presence and abundance of Ae. aegypti near human habitations and dwellings, especially in Kilifi/Kisumu, is suggestive of increased DENV transmission risk due to higher prospects of human vector contact. Despite low abundance of Ae. bromeliae suggestive of low YFV transmission risk, its proximity to human habitation as well as the observed diversity of potential YFV vectors should be of public health concern and monitored closely for targeted control. The largely outdoor resting behavior for Ae. aegypti provides insights for targeted adult vector control especially during emergency outbreak situations.

Keywords: Aedes aegypti; Aedes bromeliae; Dengue and yellow fever risk; Kenya; Mosquito diversity; Resting preference; Urbanization; Vector abundance.

PubMed Disclaimer

Conflict of interest statement

Ethics approval and consent to participate

We sought permission from household heads through oral informed consent to allow their residences to be surveyed for resting mosquitoes. Household survey of mosquitoes was carried out with ethical approval from Kenya Medical Research Institute Scientific and Ethics Review Unit (KEMRI-SERU) (Project Number SERU 2787).

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Map showing the location of the study sites within Kilifi, Kisumu and Nairobi Counties of Kenya
Fig. 2
Fig. 2
Mean Shannon diversity index for mosquitoes collected using BG-Sentinel traps in Kilifi, Kisumu and Nairobi in Kenya. Means followed by different letters are significantly different at α = 0.05
See this image and copyright information in PMC

References

    1. Gubler DJ. Dengue and dengue hemorrhagic fever. Clin Microbiol Rev. 1998;11(3):480–496. - PMC - PubMed
    1. Kraemer MUG, Faria NR, Reiner RC, Golding N, Nikolay B, Stasse S, et al. Spread of yellow fever virus outbreak in Angola and the Democratic Republic of the Congo 2015–16: a modelling study. Lancet Infect Dis. 2017;17(3):330–338. doi: 10.1016/S1473-3099(16)30513-8. - DOI - PMC - PubMed
    1. Sang RC. Dengue in Africa. In: report of the scientific working group meeting on dengue. Geneva: WHO special programme for research and training in tropical. diseases. 2007:50–2. http://apps.who.int/iris/bitstream/10665/69787/1/TDR_SWG_08_eng.pdf
    1. Wilder-Smith A, Monath TP. Responding to the threat of urban yellow fever outbreaks. Lancet Infect Dis. 2016;17:248–250. doi: 10.1016/S1473-3099(16)30588-6. - DOI - PubMed
    1. Bhatt S, Gething PW, Brady OJ, Messina JP, Farlow AW, Moyes CL, et al. The global distribution and burden of dengue. Nature. 2013;496(7446):504–507. doi: 10.1038/nature12060. - DOI - PMC - PubMed

Publication types

LinkOut - more resources