Climate-based risk models for Fasciola hepatica in Colombia

Abstract

A predictive Fasciola hepatica model, based on the growing degree day-water budget (GDD-WB) concept and the known biological requirements of the parasite, was developed within a geographical information system (GIS) in Colombia. Climate-based forecast index (CFI) values were calculated and represented in a national-scale, climate grid (18 x 18 km) using ArcGIS 9.3. A mask overlay was used to exclude unsuitable areas where mean annual temperature exceeded 25 °C, the upper threshold for development and propagation of the F. hepatica life cycle. The model was then validated and further developed by studies limited to one department in northwest Colombia. F. hepatica prevalence data was obtained from a 2008-2010 survey in 10 municipalities of 6,016 dairy cattle at 673 herd study sites, for which global positioning system coordinates were recorded. The CFI map results were compared to F. hepatica environmental risk models for the survey data points that had over 5% prevalence (231 of the 673 sites) at the 1 km2 scale using two independent approaches: (i) a GIS map query based on satellite data parameters including elevation, enhanced vegetation index and land surface temperature day-night difference; and (ii) an ecological niche model (MaxEnt), for which geographic point coordinates of F. hepatica survey farms were used with BioClim data as environmental variables to develop a probability map. The predicted risk pattern of both approaches was similar to that seen in the forecast index grid. The temporal risk, evaluated by the monthly CFIs and a daily GDD-WB forecast software for 2007 and 2008, revealed a major July-August to January transmission period with considerable inter-annual differences.

Modelling spatial distribution of snails transmitting parasitic worms with importance to human and animal health and analysis of distributional changes in relation to climate

“…Other factors that are known to affect snail distribution, such as land use and snail control were not included as no such period-specific data could be identified. Comparatively few environmental variables were explored in comparison to other studies (Moffett et al, 2007;Stensgaard, 2011;Valencia-Lopez et al, 2012;Stensgaard et al, 2013) because few environmental variables were available for the earlier period at the desired resolution. Only variables shown to have been of importance in earlier research were included, though a dataset of the mean daily temperature from the CRU dataset (Harris et al, 2013) was left out due to its high correlation to other datasets.…”

Mapping and modelling neglected tropical diseases and poverty in Latin America and the Caribbean

“…Foley et al (2012) and del Corral et al (2012) As pointed out by Mas-Coma et al (1999), the epidemiological picture of fascioliasis has changed, and human infections caused by Fasciola can no longer be considered merely a secondary zoonotic aberration but must be considered an important human parasitic disease. Interestingly, a large number of papers in the presentations at the meetings mentioned above were focused on this disease, which is also reflected in this special issue (Martins et al, 2012;Rinaldi et al, 2012;Valencia-López et al, 2012). In addition, Fasciola infections figure prominently with regard to the role of landscape ecology in the acceleration of environmental and climate changes (Valencia-López et al, 2012), something also discussed with respect to malaria incidence in Venezuela by Delgado-Petrocelli et al (2012), Chagas in Colombia and hookworm in Brazil (Mudenda et al, 2012).…”

“…Interestingly, a large number of papers in the presentations at the meetings mentioned above were focused on this disease, which is also reflected in this special issue (Martins et al, 2012;Rinaldi et al, 2012;Valencia-López et al, 2012). In addition, Fasciola infections figure prominently with regard to the role of landscape ecology in the acceleration of environmental and climate changes (Valencia-López et al, 2012), something also discussed with respect to malaria incidence in Venezuela by Delgado-Petrocelli et al (2012), Chagas in Colombia and hookworm in Brazil (Mudenda et al, 2012).…”

Socio-environmental variables and transmission risk of lymphatic filariasis in central and northern Mozambique

“…The Wb-bsI is an index based on the monthly rainfall, the monthly PET as well as the T max and T min . This index was originally used for the prediction of fascioliasis transmission in the United States of America (USA) (Malone et al, 1987), in Africa (Malone et al, 1998), in the Andean mountain range (Fuentes, 2006) and in Colombia (Valencia-López et al, 2012). It has also been used for the assessment of malaria transmission in Eritrea (Malone et al, 2003) and to model the ecological niche of hookworm in Brazil (Mudenda et al, 2012).…”