EN
A survey to determine current prevalence and intensity of bot fly (Gasterophilus spp). infection in horses at necropsy was conducted on material taken from a slaughterhouse in S³omniki near Krakow from January to April 2005. 83 untreated horses: one-year old foals (n=22) and adult horses (n=61) from small farms from southern Poland were examined. Third level instars of Gasterophilus intestinalis were found in the stomachs of 7 horses (8.4%), and the intensity of infection was from 1 to 180 larvae (a mean of 69.7). Parasites were found in 6 of the 58 mares (10.3%) and 1 of the 25 stallions (and geldings) (4.0%). Foals were not infected. Gasterophilosis in horses from small farms kept mainly under houses system or limited pasture occurs quite rarely.