Mycoplasma bovis is one of 126 species of genus Mycoplasma. Mycoplasma bovis mainly affects cattle and has little effect on other production animals. It does not affect horses and or pet animals, but other animals can be carriers for Mycoplasma bovis. Mycoplasma bovis causes a constellation of diseases, including mastitis in dairy cows, arthritis in cows and calves, pneumonia in calves, and various other diseases likely including late-term abortion. Not all infected cows get sick – some shed the disease without becoming ill, allowing for transmission between farms if apparently healthy cows are moved.