Rat mycoplasmosis

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The mycoplasmosis the rat is the most common disease of the upper respiratory tract at home or held as a laboratory animal Norway rats . This mycoplasmosis is caused by Mycoplasma pulmonis , a bacterium from the genus Mycoplasma .

Rat mycoplasmosis is a factor disease . Rats are usually infected with the pathogen before birth in the womb ( intrauterine ) or immediately afterwards. Later transmission via aerosols and direct or indirect contact is also possible. However, the disease only breaks out much later when the immune system is disturbed . Triggering factors can be stress , poor housing conditions (drafts, high ammonia concentration ), feeding errors or other infectious diseases.

Clinical picture

Mycoplasmosis occurs mainly in rats in their second year of life. It begins with unspecific symptoms of an upper respiratory disease such as sniffing, sneezing, and watery nasal discharge. As the disease progresses, the lower airways are also affected. Then there is also shortness of breath and disorders of the general condition. The latter also restricts the rat's natural urge to clean, which is why the coat looks unkempt and the reddish secretion of the nictitating gland accumulates in the corner of the eye on the nose. This secretion can also discolour the tip of the nose reddish via the tear duct . By reducing the feed intake, there is an increasing emaciation .

As a complication of the disease, an otitis media with tilted head and ataxia can occur. A genital form with inflammation of the female genital organs ( ovaries , fallopian tubes and uterus ) and abortions can also occur.

The diagnosis is extremely difficult and must mainly be based on the clinical picture. Mycoplasmas are difficult to grow, so that bacteriological studies are largely unsuccessful.


Since usually no antibiogram can be made, therapy with one antibiotic must be tried and, if it does not work , changed to another. Doxycycline , enrofloxacin , tetracycline and erythromycin have proven effective . In any case, the triggering factors must be eliminated; antibiotic treatment alone is not sufficient.

The prognosis is cautious; even with successful treatment, the animals remain carriers of the pathogen and a relapse is possible. If there is severe shortness of breath, the prognosis is poor.


  • K. Gabrisch, P. Zwart: Diseases of pets . Schlütersche Verlagsgesellschaft Hannover, 6th edition 2005. ISBN 3-89993-010-X

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