New research results obtained during the course of recent scientific programme, enable us to establish genetic structure and antigenic characteristics of different pathogenic viruses which cause economic losses in the farming systems. There is a possibility to develop new diagnostic tests kits for fast and accurate diagnosis of viral diseases. New finding in the field of viral evolution and geographical dispersion of different viral pathogens shall help to improve better actions in control and prevention of outbreaks of diseases. Contemporary molecular diagnostic methods were used in the study of epidemiology of pesti-viruses. Important progress has been made in diagnostics methods of viruses in poultry, pigs and fishes. Research in the field of honeybee biology and pathology contributed in the understanding of the action of different infective and un-infective agents on the cell and tissue level in the development forms of bee. The effects of some acaricides and antibiotic OTC were studied on the midgut of the honeybee larvae. Cytological methods were found to be useful in the studies of the environmental effects on honeybee colony development. Special emphasis has been given the methods in the field of the eco-toxicological studies. Honeybee has been found to be research model useful in further investigations. Results of the research programme present contribution in the knowledge of the action of organic acids on the parasitic Varroa destructor in honeybee colony. The action of oxalic acid, rotenone and thymol were evaluated after applications in honeybee colony and on bee organism. Morphological studies of the tracheal openings in bee body in two bee races have been performed. Characteristics were evaluated in relation of different sensitiveness to honeybee parasites. The research of TSE in native sheep contributed in the knowledge of the sensitiveness to infections. The genes for prionic proteins (PrP) were studied. PCR method was found useful in the determination of different types of Salmonela in pathological material (liver and gut content) and in animal food. Immunological status was established in animals and tics after infection with bacteria Borrelia burgdorferi s.l.