with permission from Carole Nelson of LilRatscal Rattery

Chronic murine pneumonia (CMP), or murine mycoplasmosis is the most significant and serious bacterial infection of rats. It is caused by the rather unusual bacterium, Mycoplasma Pulmonis. This organism is relatively difficult to isolate because it cannot be grown in the laboratory using ordinary culture methods. This makes diagnosis of CMP more difficult except for the fact that the disease is so very common and well recognized. For this reason, CMP is usually diagnosed by signs of illness, without attempts to isolate the causative bacterium.

Signs of CMP include sniffling, sneezing, squinting, red-brown tears, rough hair coat, and labored breathing and audible respiration. If the inner ear becomes involved, a severe, often incapacitating, head tilt usually develops. In colony situations, this disease can seriously affect the reproductive capacity of female rodents, resulting in infertility and reduced litter sizes. Because this disease tends to have a very chronic (long-lasting) course, afflicted individuals should receive antibiotic treatment as soon as the first signs are recognized. Antibiotics can be added to the drinking water for long periods. Individuals exhibiting serious, life-threatening signs must be treated aggressively with injectable antibiotics if there is any hope of helping them. Frequently, other harmful bacteria complicate CMP. This often necessitates use of multiple antibiotics. Elimination of the Mycoplasma Pulmonis organism from infected individuals is regarded by most experts as a practical impossibility. However, early treatment reduces the severity of the disease in affected rodents. It is not necessary to separate the cage mates unless very ill.

The outcome of treatment is always unpredictable because there are so many factors that can have an influence on it: individual susceptibility and resistance to the causative agent; age, physical condition and nutritional status of the individual; and the presence of complicating factors (other bacterial and/or viral infections, high levels of ammonia within the enclosure, etc).

The bacterium responsible for CMP, Mycoplasma pulmonis, is highly contagious. It may be transmitted between mother and offspring in the womb during embryonic life and by direct contact after birth. Transmission among infected and uninfected older rodents results from exchange of respiratory aerosols and sexual activity.

Rabbits, guinea pigs, and other rodents may carry the causative agent but do not manifest signs of disease. Caution must, therefore, be exercised when allowing contact between murine rodents and these potential “carriers”. Mice and rats, too, may carry the Mycoplasma pulmonis organism without showing obvious signs of illness. This is especially true of newly acquired rats. This fact underscores the importance of restricting contact between mice and rats of unknown health status and those whose health status has been proven by remaining disease-free for relatively long periods. Furthermore, all newly acquired rats and mice should be quarantined (strictly confined from other pet rodents) for at least 4-6 weeks before contact with them is permitted. Any rat exhibiting respiratory signs (no matter how mild) should never be housed with or near a healthy pet rat.

Copyright © 2020 RatChatter All rights reserved.
RatChatter v1.0 theme from