Spatiotemporal analysis of sandfly fauna (Diptera: Psychodidae) in an endemic area of visceral leishmaniasis at Pantanal, central South America

Abstract

BackgroundEnvironmental changes caused by urbanization can cause alterations in the ecology and behavior of sandflies and in the epidemiology of leishmaniasis. Geotechnological tools allow the analysis and recognition of spatiotemporal patterns by monitoring and mapping risk areas of this vector-borne disease. This study aims to describe the sandfly fauna in the municipality of Corumbá and to compare it with the data described in a three-year period from 1984 to 1986 by Galati. A further aim was to analyze the influence of environmental changes on the composition of the fauna.MethodsCaptures were conducted weekly from April 2012 to March 2013, in intra and peridomicile areas with automatic light traps, from 6:00 pm to 6:00 am. The following indices were calculated for both periods analyzed: Standardized Index of Species Abundance (SISA), Shannon’s diversity index (H) and Pielou’s index (J). The Normalized Difference Vegetation Index (NDVI) was extracted from a remote sensing LANDSAT-5 image.ResultsIn total, 7,370 specimens (6,169 males and 1,201 females) were collected, distributed among 12 species. Lutzomyia cruzi was the most frequent species (93,79%) and the first in the ranking of standardized species abundance index in both studies. The dominance of the species Lu. cruzi in the neighborhoods of Maria Leite and Centro was demonstrated by the low equitability index. The neighborhood of Cristo Redentor had the greatest diversity of sandflies in the present study and the second greatest in the study performed by Galati et al. (Rev Saúde Pública 31:378–390, 1997). Analyzing the satellite images and the NDVI from 1984 and 2010, the largest amount of dense vegetation was found in the neighborhood of Cristo Redentor.ConclusionsIt was, therefore, possible to show how changes caused due to urbanization have affected the density and distribution of Lu. cruzi and other species over time. Moreover, the data suggest that different populations of sandflies adapt in different ways according to environmental conditions and the adaptation does not necessarily depends on the presence of high vegetation cover.

Uso e cobertura do solo e prevalência de leishmaniose visceral canina em Teresina, Piauí, Brasil: uma abordagem utilizando sensoriamento remoto orbital

“…Six studies on human VL found a direct association between vegetation cover and risk of VL 16,18,19,29,39,40 , while only one found an inverse association 41 . In the studies on vectors, two found higher vector density in areas with little vegetation cover 34,35 and one found a direct relationship between vegetation cover and presence of vectors 36 .…”

“…Only two of these studies addressed the association between environmental features extracted from satellite images and canine VL 34,38 . An ecological study in 33 municipalities in Bahia State, by Bavia et al 38 , found an inverse association between vegetation cover and cases of canine VL.…”

“…However, their use in the study of VL is much more recent and relatively infrequent, particularly in Brazil, where VL transmission is zoonotic 33 . Consulting the MEDLINE (PubMed) and LILACS databases on 31/Dec/2015, only 12 studies were identified that used RS to assess the relationship between land use and land cover characteristics and spatial distribution of VL in the Brazilian context 16,18,19,29,34,35,36,37,38,39,40,41 .…”

“…Nine of the ten studies used Landsat satellite images with resolution of 15 to 30 meters 16,18,19,29,34,35,39,40,41 and only one used IKONOS images with resolution of 1 to 4 meters 36 . As for environmental aspects, seven studies evaluated vegetation cover, mainly using NDVI, and three evaluated land use and land cover characteristics.…”

Canine visceral leishmaniasis in an urban setting of Southeastern Brazil: an ecological study involving spatial analysis

“…The technique has been widely employed in the study of leishmaniasis and has permitted detailed analyses of the spatial dependency between canine and human VL, the distribution of the vector, and the characterization of areas with high incidence and high risk of morbidity [7,[18][19][20][21][22][23][24][25][26][27].…”