Quarantine of newly arrived horses with evaluation of their status is an effective and mandatory measure to prevent the spread of parasitic onset. Horses of reproductive age rarely display a clinical picture of parasitoses thereby presenting a latent threat to the youngsters and contaminating the external environment. Helminth infection can provoke sudden colic attacks that occur for no apparent reason. Vital diagnosis of Gastrophilus spp. infection is difficult because it involves application of instrumental methods or diagnostic chemotherapy. Successful prophylaxis and treatment of parasitoses are based on information about parasite (spreading, biological cycle, transmission pathways, transmission factors etc.) and the correct selection of the most effective agents for this infection. In an endemic focus it is possible to control the number of parasites in organism of the definitive host and the second-order inhabitation by performance of prophylactic treatment by anthelmintics once a quarter.