Scientific data on the diversity of dangerous clostridia species causing infectious diseases in farm animals are presented. Current knowledge about the pathogenicity and virulence factors of clostridia and their harmful effects on the organisms of highly productive animals. Information is provided on anaerobic bacteria that can form capsules and biofilm structures, which are important determinants of virulence that block the action of the immune systems of macroorganisms, antibacterial agents, and various disinfectants. Data on the phenotypic and molecular-genetic stability of such significant clostridia as C. perfringens and C. difficile, found in published research results, are presented in tables. Current information on the determinants of virulence identified in C. septicum, C. sordellii, C. sporogenes, and C. tetani from various biological materials from different animals is presented in the article. Mechanisms of resistance to antibiotics, altered expression of redox proteins, DNA repair, mutation genes responsible for antibiotic resistance, formation of biofilms, and the presence of a matrix that hinders the penetration of antimicrobial agents into bacteria are described, as well as their prevalence among pathogenic clostridia worldwide. Modern available therapy methods and antimicrobial agents are outlined as an alternative to therapeutic agents used to treat diseases in humans, animals, and poultry caused by clostridia.