EN
The examinations were carried out on the presence of onchocercosis in villiges of the Puszcza Białowieska, Puszcza Kampinoska, Bory Dolnośląskie and in the Słupsk, Skierniewice, Włocławek, Zamość and Przemyśl provinces. The samples of the skin from the ear and umbilical regions were taken from 297 cattle killed in slaughter-houses. The skin samples were cut in 1—2 mm pieces, incubated in a physiological solutionat 25°C for 24 hours and then examined for the presence of microfilariae. Microfilariae of Onchocerca lienalis and Onchocerca gutturosa were found in animals from the Puszcza Białowieska, Puszcza Kampinoska, Bory Dolnośląskie and the Przemyśl district. Extensiveness of cattle invasion by nematode O. lienalis was from 6% to 80%, and by O. gutturosa from 3% to 30%. Nematodes of Onchocerca spp were not found in the Słupsk, Skierniewice, Włocławek and Zamość districts. Focal occurrence of onchocercosis was associated with cattle pasturage near the forest biotope with streams where there could hatch intermediate hosts of Onchocerca-blood sucking insects.