Passive immunization with pathogen-specific egg yolk antibodies (IgY) is emerging as a potential alternative to antibiotics for the treatment and prevention of various human and animal diseases. Laying hens are an excellent source of high-quality polyclonal antibodies, which can be collected noninvasively from egg yolks. The use of IgY offers several advantages in that it is environmentally friendly, nontoxic, and reduces the numbers of animals required for antibody production. This paper reviews the use of IgY antibodies in the treatment and prevention of enteric pathogen infections in poultry. Brief descriptions of the production, structure, and properties of IgY are also presented. Some limitations of the technology and future perspectives are discussed.

The ban of sub-therapeutic antibiotic use in the European Union countries and elsewhere, and recent moves toward removal or reduced use of these compounds in other countries has put pressure on the poultry industry to look for viable alternatives. Available data suggest that specific egg yolk antibodies (EYA) have beneficial effects in prevention or treatment of bacterial and viral infections in humans and different animal species. The number of studies conducted in chickens, however, is quite low compared to other species and this may be a limiting factor in the current use of this technology in the poultry industry. The objectives of this review paper are to discuss how EYA are produced and work, to present examples of their applications in different pathological conditions in chickens, and to address challenges that this technology is currently facing.