Fasciolosis incidence forecasts in Belgium by means of climatic data

Forecast models based on daily temperatures and the Stormont << wet day >> fluke forecasting system were applied to assess the risk of Fasciola hepati ca over Belgium. The development times of the parasite both in the egg stag e and within the snail were assessed under annual climatic conditions by co llecting data from different meteorological stations. The fluke larval deve lopment is possible only from late april to october, with regional variatio ns. In the North of Belgium, 170 days are available to complete this develo pment whereas in the South/East this period is reduced to 130 days. In this case, parasite life cycle can not be completed in one grazing season. In m ost of the regions, cercariae sheds occur two or three times a year: the fi rst one, in spring, is moderate and the second one, at the end of the summe r, is more important. A last one may be present some years in late septembe r. In the area closed to Elsenborn only one cercariae shed occurs in summer . Efficiency and effects of several flukicides were compared from estimatio ns of cercariae sheds. Preventive therapeutic procedures were suggested acc ording to the liver fluke prediction incidence which tends to fluctuate ove r areas and years. When the predicted incidence is low, one treatment effic ient against late immature and adult stages is adviced 70 days after housin g. When this incidence is high, a first treatment is adviced at housing and a second one 70 days later. Climatic conditions of 1998 are discussed in o rder to predict the current incidence of fasciolosis.