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

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

Factors responsible for Ixodes ricinus presence and abundance across a natural-urban gradient.

To better understand the spatial distribution of the common tick Ixodes ricinus, we investigated how local site factors and landscape characteristics influence tick presence and abundance in different greenspaces along the natural-urban gradient in Stockholm County, Sweden. Ticks and field data were collected in 2017 and 2019 and analyzed in relation to habitat type distributions estimated from land cover maps using geographical information system (GIS). A total of 1378 (992 larvae, 370 nymphs, 13 females, and 3 males) questing ticks were collected from 295 sampling plots in 47 different greenspaces. Ticks were present in 41 of the 47 greenspaces and our results show that both local site features such as vegetation height, and landscape characteristics like the amount of mixed coniferous forest, significantly affect tick abundance. Tick abundance was highest in rural areas with large natural and seminatural habitats, but ticks were also present in parks and gardens in highly urbanized areas. Greenspaces along the natural-urban gradient should be included in surveillance for ticks and tick-borne diseases, including highly urbanized sites that may be perceived by the public as areas with low risk for tick encounters

Equine Granulocytic Anaplasmosis in Southern Sweden : Associations with coniferous forest, water bodies and landscape heterogeneity

Landscape characteristics influence both vector and host habitats affecting the spatial and temporal distribution of vector-borne diseases. Anaplasma phagocytophilum is one of the most widespread tick-borne diseases in Europe causing tick-borne fever (TBF) in domestic ruminants, and granulocytic anaplasmosis in humans, horses and companion animals. The aim of this study was to identify landscape factors associated with Equine Granulocytic Anaplasmosis (EGA) cases in a refined temporal and spatial analysis by combining land cover data and presence/absence disease data, using a geographical information system (GIS). This study is a retrospective analysis utilizing 1030 EGA diagnostic test results extracted from the National Veterinary Institute (SVA, Sweden). The association between EGA and different land cover types was analyzed with generalized linear models. To analyze the relation between landscape heterogeneity and EGA, we calculated the Gini-Simpson index. Our results showed a significant increase in the proportion positive EGA cases from 2002 to 2015 and marked differences in the seasonal within year distribution of EGA cases. The association with landscape configuration is shown by the positive relationship between A. phagocytophilum and coniferous forest, water bodies, and landscape heterogeneity, respectively. The information on the eco-epidemiological drivers for EGA can be central for disease control and prevention. Our method of linking land cover to disease risk may be applied to other vector-borne diseases and to other study regions

The effects of exposure to environmentally relevant PFAS concentrations for aquatic organisms at different consumer trophic levels : Systematic review and meta-analyses

Per-and polyfluoroalkyl substances (PFAS) is a collective name for approximately 4700 synthetic chemicals ubiquitous in the aquatic environment worldwide. They are used in a wide array of products and are found in living organisms around the world. Some PFAS have been associated with cancer, developmental toxicity, endocrine disruption, and other health effects. Only a fraction of PFAS are currently monitored and regulated and the presence and effects on aquatic organisms of many PFAS are largely unknown. The aim of this study is to investigate the health effects of environmentally relevant concentrations of PFAS on aquatic organisms at different consumer trophic levels through a systematic review and meta-analysis. The main result shows that PFAS in concentrations up to 13.5 μg/L have adverse effects on body size variables for secondary consumers. However, no significant effects on liver or gonad somatic indices and neither on fecundity were found. In addition, the results show that there are large research gaps for PFAS effects on different organisms in aquatic environments at environmentally relevant concentrations. Most studies have been performed on secondary consumers and there is a substantial lack of studies on other consumers in aquatic ecosystems

The effect of local scale and landscape scale variables on <i>Ixodes ricinus</i> nymphs measured in buffer zones consisting of 100m increments within a 100m–1000m radius.

Presence and abundance of I. ricinus nymphs were analyzed in generalized linear mixed zero-inflated models. Estimated coefficients and significance levels for the explanatory variables from both the conditional model part (abundance) and the zero-inflated model part (presence/absence) is reported for each buffer zone size. For easier interpretation we have changed the sign of the estimates for the zero-inflated models meaning that a positive coefficient should be interpreted as a higher likelihood for tick presence.</p

Swedish land cover nomenclature including grid code, land cover type and definition.

Swedish land cover nomenclature including grid code, land cover type and definition.</p

The effect of local scale factors and landscape variables on <i>Ixodes ricinus</i> larvae measured in buffer zones consisting of 100m increments within a 100m–1000m radius.

Presence and abundance of I. ricinus larvae were analyzed in generalized linear mixed zero-inflated models. Estimated coefficients and significance levels for the explanatory variables from both the conditional model part (abundance) and the zero-inflated model part (presence/absence) is reported for each buffer zone size. For easier interpretation we have changed the sign of the estimates for the zero-inflated model part meaning that a positive coefficient should be interpreted as a higher likelihood for tick presence.</p

The effect of urbanization and landscape configuration on questing <i>Ixodes ricinus</i> presence and abundance measured in 1000m radius buffer zones analyzed in generalized linear mixed zero-inflated models.

Estimated coefficients and significance levels for the explanatory variables from both the conditional (abundance) and zero-inflated (presence/absence) model components are reported for I. ricinus larvae and nymphs. Parameter estimates and significance levels for landscape factors are estimated based on a 1000m radius buffer zone and for local site factors from individual sampling plots. For easier interpretation we have changed the sign of the estimates for the zero-inflated models meaning that a positive coefficient should be interpreted as a higher likelihood for tick presence and vice versa.</p

The degree of urbanization and <i>Ixodes ricinus</i> abundance at each sampling site in Stockholm County.

The degree of urbanization and Ixodes ricinus abundance at each sampling site in Stockholm County.</p

Effect of vegetation height on number of <i>Ixodes ricinus</i> larvae (A) and nymphs (B).

The results from the glmmTMB show significant negative effects of field layer vegetation height with more questing I. ricinus in lower vegetation. Grey area indicates 95% confidence band.</p