Abstract
BackgroundA deeper understanding of the ecology and small-scale heterogeneity of malaria transmission is essential for the design of effective prevention, control and elimination interventions. The spatial and temporal distribution of malaria vectors was investigated in five villages in close proximity to a hydro-agricultural system in Côte d’Ivoire over the course of construction and the early phase of irrigated rice farming.MethodsThe study was carried out in five villages (Raffierkro, N’Douakro, Ahougui, Kpokahankro, Koffikro) near Bouaké, central Côte d’Ivoire, between early 2007 and late 2009. In each village, mosquitoes were collected by human landing catches and identified morphologically at genus and species level, and entomological parameters were determined. Plasmodium infection was assessed by dissection and an enzyme-linked immunosorbent assay.ResultsA total of 19,404 mosquitoes belonging to the genus Anopheles were sampled during 328 human-night catches. Before the construction of the hydro-agricultural system, comparable densities of Anopheles gambiae were observed in all villages. In subsequent years, densities in Raffierkro and Ahougui were significantly higher than the other villages [Kruskal–Wallis (KW) test = 31.13, p < 0.001]. The density of Anopheles funestus in the five villages was comparable in the early stage of the project, while a high density was reported in Koffikro at the end (KW test = 11.91, p = 0.018). Transmission of Plasmodium falciparum is perennial in the study area. Over the course of the study, high entomological inoculation rates (EIRs) were found: 219–328 infectious bites per person per year with An. gambiae. For An. funestus considerably lower EIRs were observed (5.7–39.4). Changing patterns of An. gambiae were not correlated with malaria transmission.ConclusionIn this study setting, located in the bioclimatic transition zone of Côte d’Ivoire, rice cultivation was not observed to increase malaria transmission. The entomological parameters recorded until the onset of rice-growing activities in a hydro-agricultural system presented considerable heterogeneity both in space and time; a strong increase of Anopheles mosquitoes was observed in two of the five villages located in close proximity to the dam and irrigated rice fields. Malaria still is a main public health problem in all villages that require adequate control measures.
Highlights
A deeper understanding of the ecology and small-scale heterogeneity of malaria transmission is essen‐ tial for the design of effective prevention, control and elimination interventions
Studies were conducted in five villages in close proximity to a small hydro-agricultural system in an area of high malaria transmission in central Côte d’Ivoire and the dynamics of entomological parameters were studied over a three-year period
The results shows as previously known in central Côte d’Ivoire [15, 18] that An. gambiae s.s, and An. funestus s.s. were the main malaria vectors driving the high level of transmission in this region
Summary
A deeper understanding of the ecology and small-scale heterogeneity of malaria transmission is essen‐ tial for the design of effective prevention, control and elimination interventions. The spatial and temporal distribution of malaria vectors was investigated in five villages in close proximity to a hydro-agricultural system in Côte d’Ivoire over the course of construction and the early phase of irrigated rice farming. Previous research has shown that ecological transformations consequential to rice developments considerably influenced the diversity and density of the culicidae fauna and sometimes malaria transmission. In Mali [11] and Senegal [12] higher densities of Anopheles in rice area did not influence malaria transmission. Studies in the savannah area have shown that an increased density of Anopheles did not influence malaria transmission [13]. In the western forest area of Côte d’Ivoire, the high aggressive density of Anopheles funestus resulted in an increase of malaria transmission in villages performing one rice crop per year [14]. Plasmodium falciparum is the predominant malaria species encountered (80–95 % of infections), followed by Plasmodium malariae (7–10 %) and Plasmodium ovale (1–3 %) [19]
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