The Science

A genital form of Mycoplasma pulmonis, which generally only affects female rats - male rat occurrence has not been well documented.

Stress or other illnesses can weaken your rat's immune system and cause your rat to break with an active mycoplasmal infection. Over-crowding, bad ventilation, dirty cages and unsafe bedding (especially cedar and pine), which can cause build-ups of ammonia with the cages, can all damage the respiratory system's own protective capacity. Vitamin A or E deficiencies may also be predisposing factors.

The organism is transmitted by direct contact between mother and babies (i.e. placental), by sexual transfer, other animal carriers and can even be passed on to baby rats while travel through the birth canal, but only if the mother is infected with myco. It is also airborne over short distances.


Infertility, embryonic re-absorptions, and small litters may all be a sign of MGM.


Probably best diagnosed by a Vet, who will listen to your rats breathing to see if the lungs are infected and may take a tissue sample from the nasal pharynx, trachea, uterus, or lungs.


Although there is no actual cure for Mycoplasma pulmonis, there are several antibiotic treatments that have shown good success rates in keeping the symptoms at bay. The disease will eventually run its course, and death will occur, but by giving strong courses of antibiotics this can be delayed for long periods of time.


Strict husbandry standards, exclusion of wild rodents, serologic and postmortem monitoring, good ventilation, and low population densities in cage and room contribute to the maintenance of a Mycoplasma-free colony.
Hysterectomy in female rats is the only really guaranteed way of having a myco free colony, however this is not always advisable as it is an extremely major operation.