A total of 20 749 bulk tank milk (BTM) samples was collected in November 2008 from all over Germany, corresponding to 20.9% of all German dairy herds. The BTM samples were analysed for antibodies against Fasciola hepatica using the excretory-secretory (ES) ELISA. A geospatial map was drawn to show herd prevalences per postal code area. Various spatial risk factors were tested for potential statistical associations with the ELISA results in logistic regression supported by a geographical information system (GIS). The mean seroprevalence was 23.6% and prevalences in different German federal states varied between 2.6% and 38.4%. GIS analysis revealed statistically significant positive associations between the proportion of grassed area and water bodies per postal code area and positive BTM ELISA results. This can be explained by the biology of the intermediate host, the amphibious snail Galba (Lymnea) truncatula and the pasture-borne nature of fasciolosis. The full logistic regression model had a Pseudo-R 2 of 22%, while the final model obtained by controlled stepwise model building revealed a Pseudo-R 2 of 14%, indicating that additional, unrecorded factors and random effects contributed substantially to the occurrence of positive ELISA results. Considering the high seroprevalences in some areas and the economic impact of fasciolosis, farmers and veterinarians should be strongly advised to implement effective liver fluke control programmes.

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Fasciolosis, caused by the liver fluke Fasciola hepatica, is one of the most important parasitoses in cattle farming worldwide. In dairy cows, the trematode leads to economic losses due to decreased milk yield, a negative impact on reproduction parameters, and liver condemnations. In the present study, the seasonal patterns of F. hepatica antibodies in bulk-tank milk from dairy herds located in East Frisia, a region of the federal state Lower Saxony in the north of Germany, were investigated. This region was chosen since it is known as a high risk area for fluke infections due to its coastal location at the North Sea with the consequence of rather moist pastures. Between 669 and 868 bulk-tank milk samples were collected in January, September and November 2008 and 2010, respectively, and analysed for antibodies against F. hepatica with an in-house ELISA based on excretory-secretory antigens of the liver fluke. The overall East Frisian prevalence was 49.1%, 57.1% and 53.9% in January, September and November 2008 and 45.1%, 49.5% and 48.4% in 2010. From a number of 606 farms, which were sampled in all six investigated months, 34.5% of the farms continued to remain positive, whereas 30.9% continued to remain negative. A percentage of 69.1% (419 farms) were positive on at least one sampling occasion during the study period. The distributions of optical density ratio (ODR) values were skewed to the left but showed a second, lower peak in a high ODR range. Statistical analysis revealed a significant difference concerning the prevalence increase from January to September 2008. Furthermore, the prevalence decrease from September as well as November 2008 to these months in 2010 was significantly different, what might result from a more frequent use of anthelminthics or different climatic conditions.