From time immemorial people began to domesticate wild animals and throughout many generations, they are kept by people genetically isolated from external pathogens. In the prevailing era, every pet owner is trying to breed and protect his animal from contagious and noncontagious diseases. Having said that, lack and inadequacy of knowledge and mass media on simple preventive measures results in the widespread occurrence of infectious and invasive diseases, including flea, Ctenocephalides felis infestation among dogs as well as cats. The present paper primarily attempts to present the results of therapeutic efficiency of Komfortis, Foresto, and Fitoelita medical agents used during flea infestation among domestic cats. In order to meet the purpose of the study, research was carried out within the framework of study and analysis of the epizootic state of invasive diseases of agricultural and unproductive animals, bees, and birds. Studies of changes in the species composition, and bioecological patterns of the development cycle of parasites under shifting boundaries of their ranges were also done. For the study, the animals were divided into three groups of 10 animals each. Standard clinical and hematological research methods were used during the study. Blood sampling included three stages: before insecticide treatment, the intermediate interval of 15 days, and the final stage. Based on the results obtained, it was found that Komfortis and Foresto have 100% therapeutic efficacy at all stages of flea development and possess a long-lasting action duringa flea infestation. The morphological blood analysisshowed that the proposed medical agents have no toxic orsideeffects.