Seasonal relationship between normalized difference vegetation index and abundance of the Phlebotomus kala-azar vector in an endemic focus in Bihar, India

Abstract

Abstract.Remote sensing was applied for the collection of spatio-temporal data to increase our understanding of the potential distribution of the kala-azar vector Phlebotomus argentipes in endemic areas of the Vaishali district of Bihar, India. We produced monthly distribution maps of the normalized difference vegetation index (NDVI) based on data from the thematic mapper (TM) sensor onboard the Landsat-5 satellite. Minimum, maximum and mean NDVI values were computed for each month and compared with the concurrent incidence of kala-azar and the vector density. Maximum and mean NDVI values (R 2 = 0.55 and R 2 = 0.60, respectively), as well as the season likelihood ratio (X 2 = 17.51; P <0.001), were found to be strongly associated with kala-azar, while the correlation with between minimum NDVI values and kala-azar was weak (R 2 = 0.25). Additionally, a strong association was found between the mean and maximum NDVI values with seasonal vector abundance (R 2 = 0.60 and R 2 = 0.55, respectively) but there was only a marginal association between minimum NDVI value and the spatial distribution of kala-azar vis-à-vis P. argentipes density.

Environmental factors associated with the distribution of visceral leishmaniasis in endemic areas of Bangladesh: modeling the ecological niche

“…Case–control studies in India confirmed that rural households in close proximity to waterbodies were at greater risk of VL than those apart [40, 94]. Bhunia et al [39, 90] examined the effect of waterbodies/NDWI derived from satellite data on VL cases and reported a strong association, which agrees with our finding. Their study further revealed that VL cases decreased with increased distance from waterbodies.…”

“…It is, thus, reasonable to assume that moist conditions resulting from heavy rainfall lead to the occurrence of the disease and possibly support sand fly emergence and abundance, especially in the study area, because high humidity is a prerequisite for their survival [38, 89]. Humidity determines the extrinsic incubation and vector life cycle, and Bhunia et al [90], for example, observed that the abundance of P. argentipes in Bihar was associated with high humidity and heavy rainfall. Our results differ slightly from those of similar studies in Iran [91], India [39, 89], and Sudan [38] in which annual rainfall, rather than precipitation during a certain period, was reported as an influential factor affecting the distribution of the disease.…”

Global Distribution and Prediction of Transmission-Risk of Visceral Leishmaniasis

“…Adequate moisture is necessary for the developmental stages of the vector, whereas sugar resources are essential for adult sandf lies. Previous studies have shown overlapping vegetation and VL incidence and vector abundance [31]. A close relationship was found between vegetation coverage intensity and seasonal vector abundance.…”

Global distribution maps of the leishmaniases

“…The importance of considering NDVI was demonstrated with respect to the distribution of the reservoir Psammomys obesus (sand rat) and the distribution of its primary food, chenopods (Toumi et al., 2012). NDVI has been implicated as a key explanatory variable in the distribution of leishmaniasis cases in several studies (Cross et al, 1996; Thomson et al, 1999; Elnaiem et al, 2003; Gebre-Michael et al, 2004; Elnaiem, 2011; Hartemink et al, 2011; Bhunia et al, 2012; Toumi et al, 2012; de Oliveira et al, 2012). …”