Probiotics as Potential Enhancers of Veterinary Vaccines

Viral, bacterial, and parasitic diseases in food-producing and companion animals are permanent problems for humankind. Research to solve this concern includes those based on modulation of the immune system, such as probiotic supplementation and vaccination. Vaccines are a cheap alternative to prevent and control diseases, while probiotics provide several health benefits to the host, including immunostimulation. Research on unified strategies has been scarcely explored, but the current results evidence that probiotics can serve as potentiators of vaccines. Yeast and bacterial probiotic supplementation, mono- or multi-species and before or after vaccination, among other assessments, in ruminants, equines, swine, poultry, fish, and dogs, against bacterial, viral and/or parasitic infections has revealed increased immune responses and, in a few studies, protective outcomes. Therefore, this review aimed to describe those scientific findings and discuss their limitations and implications for the use of probiotics as vaccine enhancers in veterinary species. Through the modulation of innate and adaptive immune responses, probiotic usage may also expand opportunities for the development of potential vaccine enhancers in veterinary medicine.