An ecohydrological model of malaria outbreaks

Abstract

Abstract. Malaria is a geographically widespread infectious disease that is well known to be affected by climate variability at both seasonal and interannual timescales. In an effort to identify climatic factors that impact malaria dynamics, there has been considerable research focused on the development of appropriate disease models for malaria transmission driven by climatic time series. These analyses have focused largely on variation in temperature and rainfall as direct climatic drivers of malaria dynamics. Here, we further these efforts by considering additionally the role that soil water content may play in driving malaria incidence. Specifically, we hypothesize that hydro-climatic variability should be an important factor in controlling the availability of mosquito habitats, thereby governing mosquito growth rates. To test this hypothesis, we reduce a nonlinear ecohydrological model to a simple linear model through a series of consecutive assumptions and apply this model to malaria incidence data from three South African provinces. Despite the assumptions made in the reduction of the model, we show that soil water content can account for a significant portion of malaria's case variability beyond its seasonal patterns, whereas neither temperature nor rainfall alone can do so. Future work should therefore consider soil water content as a simple and computable variable for incorporation into climate-driven disease models of malaria and other vector-borne infectious diseases.

Projected Impacts of Climate Change on Environmental Suitability for Malaria Transmission in West Africa

“…Shaman et al (2002) and Porphyre et al (2005) used hydrological models to link rainfall to the abundance of Culex and Aedes mosquitoes, which breed in floodwaters and serve as the primary vectors for several arboviruses. Montosi et al (2012) used an ecohydrological model as well as a simplified linear model to calculate soil water content, which was then used to model malaria incidence. The processes by which rainfall is diverted into pools suitable for Anopheles breeding are strongly dependent on the frequency, intensity, and duration of rainfall events in addition to site-specific topographical features, soil characteristics, and vegetation cover.…”

Soil Moisture for Hydrological Applications: Open Questions and New Opportunities

“…In the scientific literature, meteorological observations have been widely employed for determining spatial and temporal occurrence of epidemic risk (e.g., [131]), while only recently soil moisture data from modelling and observations have been considered in this respect [45,132,133]. For instance, Montosi et al [132] developed an ecohydrological model for identifying the factors influencing malaria dynamics and highlighted the important role played by soil moisture. By using published data of malaria incidence rates in Mpumalanga and Botswana regions (Africa), we performed a simple correlation analysis between European Remote Sensing Scatterometer (ESCAT) and ASCAT satellite soil moisture products and malaria incidence rates ( Figure 5).…”

The predictability of mosquito abundance from daily to monthly timescales

“…, Day and Shaman , Montosi et al. ). More rarely, long‐term daily abundance observations of adult mosquito populations have been used to inform modelling and address population variability over short timescales (Shaman et al.…”

“…introduction With the emergence and reemergence of mosquitoborne diseases worldwide predictive models of mosquito population dynamics are urgently needed to assist in decision making and to improve and test our understanding of the processes regulating mosquito populations (Pascual et al 2006, LaDeau et al 2007, Bomblies et al 2008, Randolph and Rogers 2010, Chuang et al 2012, Jian et al 2014a). Long-term studies of mosquito abundance have investigated the driving factors of mosquito population dynamics, usually based on onceper-week or once-per month population observations (Shaman et al 2004, Bomblies et al 2008, Day and Shaman 2009, Montosi et al 2012). More rarely, long-term daily abundance observations of adult mosquito populations have been used to inform modelling and address population variability over short timescales (Shaman et al 2002, Chuang et al 2012, Jian et al 2014b).…”