Urbanization is a main driver for the larval ecology of Aedes mosquitoes in arbovirus-endemic settings in south-eastern Côte d'Ivoire

Abstract

BackgroundFailure in detecting naturally occurring breeding sites of Aedes mosquitoes can bias the conclusions drawn from field studies, and hence, negatively affect intervention outcomes. We characterized the habitats of immature Aedes mosquitoes and explored species dynamics along a rural-to-urban gradient in a West Africa setting where yellow fever and dengue co-exist.MethodologyBetween January 2013 and October 2014, we collected immature Aedes mosquitoes in water containers in rural, suburban, and urban areas of south-eastern Côte d’Ivoire, using standardized sampling procedures. Immature mosquitoes were reared in the laboratory and adult specimens identified at species level.Principal findingsWe collected 6,159, 14,347, and 22,974 Aedes mosquitoes belonging to 17, 8, and 3 different species in rural, suburban, and urban environments, respectively. Ae. aegypti was the predominant species throughout, with a particularly high abundance in urban areas (99.374%). Eleven Aedes larval species not previously sampled in similar settings of Côte d’Ivoire were identified: Ae. albopictus, Ae. angustus, Ae. apicoargenteus, Ae. argenteopunctatus, Ae. haworthi, Ae. lilii, Ae. longipalpis, Ae. opok, Ae. palpalis, Ae. stokesi, and Ae. unilineatus. Aedes breeding site positivity was associated with study area, container type, shade, detritus, water turbidity, geographic location, season, and the presence of predators. We found proportionally more positive breeding sites in urban (2,136/3,374, 63.3%), compared to suburban (1,428/3,069, 46.5%) and rural areas (738/2,423, 30.5%). In the urban setting, the predominant breeding sites were industrial containers (e.g., tires and discarded containers). In suburban areas, containers made of traditional materials (e.g., clay pots) were most frequently encountered. In rural areas, natural containers (e.g., tree holes and bamboos) were common and represented 22.1% (163/738) of all Aedes-positive containers, hosting 18.7% of the Aedes fauna. The predatory mosquito species Culex tigripes was commonly sampled, while Toxorhynchites and Eretmapodites were mostly collected in rural areas.Conclusions/significanceIn Côte d’Ivoire, urbanization is associated with high abundance of Aedes larvae and a predominance of artificial containers as breeding sites, mostly colonized by Ae. aegypti in urban areas. Natural containers are still common in rural areas harboring several Aedes species and, therefore, limiting the impact of systematic removal of discarded containers on the control of arbovirus diseases.

A Mapping Review on Urban Landscape Factors of Dengue Retrieved from Earth Observation Data, GIS Techniques, and Survey Questionnaires

“…This risk exists in nearly a hundred countries, with an estimated 390 million cases per year worldwide [2]. Urban areas are particularly at risk because of (i) the larval habitats of the Aedes mosquitoes [3][4][5] (ii) the high density of human populations, and (iii) the multiplicity of migration and commuting patterns, that could be catalysts for the rapid spread of infectious diseases [6].…”

Spatial Associations Between Land Use and Infectious Disease: Zika Virus in Colombia

“…are ground or natural pools, both salt and fresh water [4]. However, these mosquitoes have adapted to using containers, tires, and plant pots as breeding grounds and are now found in urban, rural, and forested areas [4][5][6]. This adaptation is believed to be the reason behind the international spread of Aedes spp.…”

“…In Cote d'Ivoire, the prominence of artificial containers was the primary contributor to the increase of Aedes larvae in urban settings [6]. These changes result in new environments that are optimal for mosquito breeding, including areas which were previously uninhabitable [16].…”

Research agenda for preventing mosquito-transmitted diseases through improving the built environment in sub-Saharan Africa

“…Malaria is transmitted by Anopheles mosquitoes, that are rural night-time biting vectors, whilst many important viral diseases like dengue, chikungunya, yellow fever and Zika are transmitted principally by Aedes aegytpi mosquitoes, which are urban day-biting vectors. Both malaria and Aedes-borne diseases are environmental diseases affected by the quality of the built environment, with the majority of mosquito biting occurring inside or around houses, and most of the aquatic habitats being man-made (Zahouli et al 2017).…”