Predicting risk habitats for the transmission of the small liver fluke, Dicrocoelium dendriticum to grazing ruminants

Abstract

Abstract. A multiple regression model was used to analyse if the structure of vegetation and soil patches in grazed units (pastures) can be used as explanatory variables to predict the prevalence of Dicrocoelium dendriticum, a common parasite of cattle and sheep, in grazing cattle stocks on the Baltic island of Öland in southern Sweden. The scale dependency was evaluated by comparing three levels of spatial resolution of patches. Prevalence data were obtained from slaughtered animals. Our models predict that the prevalence of D. dendriticum increases in grazed areas with woody vegetation, whereas moist and wet areas decrease parasite prevalence. The predictive power of the statistical models increased with increasing level of patch resolution. Approximately 42% of the variation in parasite prevalence (angular transformation) was explained by the areal proportion of vegetation types (4 th -root-transformed). Based on the results obtained, we believe that our model strategy provides a rational and systematic tool to identify habitats that carry risk for D. dendriticum infection of ruminants, and that it can be applied to other parasites with similar life cycles such as Fasciola hepatica.

Constraints of using historical data for modelling the spatial distribution of helminth parasites in ruminants

“…As a result, the area surrounding the CREMOPAR is overrepresented as compared to other sampled areas. This should not be confused with a clustered distribution pattern of this parasite, as reported in other studies [4,6,11,29] where clustered areas of presence were observed within larger sampled, but negative, areas. In these surveys, the clustering observed was likely due to the specific eco-climatic condition required by intermediate hosts of D. dendriticum to develop.…”

“…Dicrocoeliosis is also zoonotic [22,36]. Hence, modelling the spatial distribution of this parasite can help to improve its management in higher risk regions [11,27]. Due to global climate change, seasonal and spatial patterns of parasites can alter [7].…”

“…Clustering can be observed for D. dendriticum in the southern part of Italy mainly due to the specific environmental needs of the intermediate hosts [6,29]. Ekstam et al [11] and Musella et al [29] showed that the prevalence of D. dendriticum increases in areas with woody vegetation and decreases in wet areas. Species distribution model algorithms and the accuracy of model output are also sensitive to the sample size of species occurrence records [41], and spatial sample selection bias [3].…”

Spatial Distribution of Dicrocoelium in the Himalayan Ranges: Potential Impacts of Ecological Niches and Climatic Variables

“…The results suggest that these factors play a key role in the development, survival and transmission of Dicrocoelid flukes and their intermediate hosts. The results also found a high correlation between distance from population built-up areas and summer NDVI and the presence of Dicrocoelium infection, explained by the observation that forest areas with permanent pastures, good water availability and suitable soil type provide suitable habitats for land snails and ant intermediate hosts, and opportunities for final host infection [37].…”

Evaluation of molecular methods for the field study of the natural history of Dicrocoelium dendriticum

“…Also, the longevity of infective miracidia in the environment, (Alunda and Rojo-Vàzquez, 1983); the role of sympatric wildlife as reservoir hosts; and a broader consideration of the relationship between changing environmental and climatic conditions and parasite epidemiology (Ekstam et al, 2011).…”