EN
In spite of the enormous achievements of medical and biological sciences, parasites still constitute important medical and veterinary problem. One of the main obstacles in the treatment and eradication of human and animals parasitic diseases is drug resistance of parasites. This phenomenon has more and more frequently been described both in medical and veterinary practice. The application of numerous molecular biology techniques in modern parasitological laboratories have enabled the investigations of parasites at the DNA level. The results of these studies have revolutionised our knowledge and made possible the recognition of not only the reasons and extent of genetic differentiation of parasites but also the recognition of genetic and molecular mechamisms of drug resistance. The results of many studies showed interspecific, interpopulational, and even intrapopulational heterogeneity of parasites in their sensitivity to antiparasitic drugs. Moreover, it has been found that in various parasites there often exist different molecular bases of the drug resistance. The review concerns different molecular mechanisms of drug resistance in selected parasite taxa (Schistosoma spp., Haemonchus contortus, Leishmania spp., Plasmodium falciparum, Entamoeba histolytica).