Complete ideas about the relationship between helminths and their habitat have both theoretical and applied significance. The aim of the research was a systematic analysis based on data from the epizootologycal monitoring of certain helminthiases of ruminant animals. The results of the studies confirmed the existence of complex adaptations in nematodes of the families Strongyloididae, Trichostrongylidae. Evolutionarily formed adaptations allow helminths to preserve genetic potential, balance in the environment of I and II order, to maintain the optimal variety of populations. On the basis of the revealed features, systematic regulation of the level of the epizootic process is possible.