The effectiveness of probiotics, defined as live microorganisms that benefit the host when used in sufficient amounts, on the host has been proven by studies on the treatment of many infections, especially gastrointestinal diseases. A good probiotic should be non-pathogenic and non-toxic, as well as have a beneficial effect on the host. Probiotics have been shown to promote growth, increase feed conversion ratio, protect the host from intestinal infection, and stimulate immune responses in livestock. Although the effectiveness of probiotics is limited to bacterial and viral diseases, their use for the control of parasitic infections has increased in recent years. They have been shown to be beneficial against digestive system protozoa, especially in studies using animal models and in vitro culture experiments. However, the molecular mechanisms that mediate the beneficial effects of probiotics have not been fully elucidated, and it has been shown that they can provide protection against parasites through more than one mechanism.