**1. Introduction**

154 Current Topics in Tropical Medicine

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The transmission of the parasites that cause human malaria is influenced by myriad environmental factors, including changes in agricultural practices, deforestation, and waterresources development and management (Ijumba and Lindsay, 2001; Ijumba et al., 2002; Keiser et al., 2005; Guerra et al., 2006), climatic factors such as rainfall, humidity and temperature (Reiter, 2008), and various cultural, economic, political and social factors, including health-seeking behaviour, urbanization, armed conflict and war (Esse et al., 2008; Baragatti et al., 2009). Drug resistance in the causative parasites and insecticide resistance in the mosquito vectors are also important factors that now influence malaria transmission (Reiter, 2008). Each year, in many parts of Africa, the local populations of anopheline mosquitoes build up rapidly and peak shortly after the onset of the rainy season (Mbogo et al., 1995). In two studies on the relationships between mosquito abundance, malaria transmission and rainfall in West Africa, 70%–90% of the children investigated were found infected with *Plasmodium spp*. after the rainy season (Bonnet et al., 2002; Koudou et al., 2009). It is particularly during and at the end of the rainy season that malaria becomes one of the leading causes of mortality and health-seeking at dispensaries and hospitals in this region (Rey et al., 1987). Not only season but also changing patterns of agriculture, particularly irrigated rice farming, influence malaria transmission in Africa (Ijumba & Lindsay, 2001; Diuk-Wasser et al., 2007; Sogoba et al., 2007).

Additionally, malaria transmission, *Plasmodium* prevalence rates, the proportion of presumptive and clinically-confirmed malaria episodes have been studied in two villages of central Côte d'Ivoire: one with irrigated rice farming (Zatta) and one without (Tiémélékro) (Koudou et al., 2009). Due to a farmers' conflict over land and socio-political issues, irrigated rice farming was interrupted in Zatta in 2003. The goal of this contribution to a book chapter is to evaluate the relationship between *Plasmodium* transmission, seasonality and agriculture practices.

Effects of Irrigated Rice Fields and Seasonality on

*Plasmodium* Transmission in West Africa, Particularly in Central Côte d'Ivoire 157

examination of tracheoles (Detinova, 1962). For quality control, a random sample of 10% of the mosquitoes investigated were re-examined by a senior technician. Secondly, a proportion of *An. gambiae* female having laid eggs at least once was checked for *P. falciparum* infection, in an ELISA for detecting the parasite's circumsporozoite protein (Beier et al.,

Fig. 1. Vegetation mapping of Côte-d'Ivoire presenting both study sites (Zatta and

Tiemelekro) located in the central part of the country.
