Investigations were carried out on 993 cows in 14 breeding farms in 1998-19
99. In 871 cows feces from rectum were collected and examined in the labora
tory; eggs of Fasciola hepatica were detected in 36, that is 4.13%. The mos
t extensive invasion of fasciolosis was observed in dairy cows from the Mys
zyniec area (20%) and in farms in the north-east Olsztyn area (8.7-16.7%);
the lowest prevalence was observed in the west of the Olsztyn area (2.2-3.3
%), In 6 (42.8%) out of 14 investigated farms liver fluke was not observed.
The research showed that the significantly decreased extensive invasion of
Fasciola hepatica in dairy cows in North-East Poland was not caused by syst
ematic treatment, but was influenced by environmental indicators, mostly fr
om acidity of water, where miracidiums die and snails - intermediate hosts
of Fasciola hepatica - do not develop.