Infections with Mycoplasma pulmonis are highly contagious and
among the most common causes of respiratory disease in mice and
rats. Mycoplasma pulmonis may be the sole organism causing
disease, or more often, there may be a mixed infection with
certain viruses (especially Sendai virus) or other bacteria.
Mycoplasma are different from many other bacteria in that they
have no cell wall and are therefore very sensitive to drying,
heat, and disinfectants, and cannot survive for long outside the
body. An infection with Mycoplasma is termed "mycoplasmosis."
How is Mycoplasma pulmonis transmitted? Mycoplasma pulmonis
bacteria are present in the upper respiratory tract and
reproductive tract in many apparently healthy rats and mice.
These animals act as carriers of the organism, spreading the
bacteria during close contact (during mating or nursing young)
or as aerosols through the air. Baby mice and rats may also
become infected during the birth process in which they come in
contact with the bacteria in the mother's