EN
The aim of the study was to compare the course and dynamics of strongyles invasion in treated and untreated primitive Polish horses. Grovermina paste (ivermectin) was used in September for treating horses from a group of stables. One month following the treatment the extensiveness of strongyles invasion in the mares decreased to 19% and the following month it had increased to 71%. From December the eggs of the nematodes were observed in the faeces of all the mares. The lowest intensity of invasion was in October, following which it slowly increased. In March it was similar to its state prior treatment. In stallions from the same group, the eggs of strongyles were not found in all months except October. In horses from forest breeding, the eggs of the nematodes were found during the whole period of the study. In September, October and November their number in mares' faeces was considerably higher than in mares from alcove breeding, while in stallions it was elevated only in November. Based on the data obtained it was ascertained that the strongyles invasion reappeared after 2-3 months in horses during their period when they were kept in stables