Mice diseases Bacterial diseases MRM Mycoplasma pulmonis is

Mice diseases

Bacterial diseases

MRM ■ ■ Mycoplasma pulmonis is the cause of murine respiratory mycoplasmosis, or MRM In the respiratory tract, M. pulmonis preferentially colonizes the nasal passages and middle ears

Etiology - Mycoplasma pulmonis ■ ■ ■ Most infections are subclinical- carried in nasopharynx Disease induced by high cage ammonia or pathogens Slow onset, chronic condition Aerosol and direct contact “Proximal Airway Disease”

Mycoplasma pulmonis ■ ■ ■ Early signs: purulent nasal discharge, otitis media, sneezing, “sniffling”, porphyrin staining Progresses to labored breathing, anorexia, lethargy, hunched posture Bronchopneumonia

Gross Lesions ■ ■ In advanced disease, the lungs can have gray-purple patches that often have a "cobblestone" appearance. Pictures…

The left lobe of these lungs from a mouse with experimental MRM has a gray-purple "cobblestone" appearance due to accumulation of inflammatory cells in and around airways,

Diagnosis ■ Commercial ELISA and IFA tests are useful for health monitoring, but serologic testing can be complicated by potential cross reactions with other rodent mycoplasmas.

Treatment ■ Enrofloxacin

Tyzzer’s disease ■ Clostridium piliforme is the cause of Tyzzer’s disease. It is a gram-negative, motile, spore-forming bacillus

Epizootiology ■ C. piliforme has a worldwide distribution and a wide host range, including rats, mice, gerbils, hamsters, guinea pigs, rabbits, dogs, cats, horses, nonhuman primates, and various wild species. Mice appear to be affected more often than rats.

Clinical signs ■ Many affected rats and mice are simply found dead without prior signs being observed. If present, clinical signs include lethargy, ruffled fur, and diarrhea, as indicated by fecal soiling of the fur.

Transmission ■ ■ Transmission is presumably fecal-oral. Possibilities include vertical transmission and introduction of spores; contaminated feed; or incompletely sterilized food, bedding, or water. Morbidity and mortality are highly variable.

■ The most consistent lesions in mice are multiple, pale, slightly depressed foci of necrosis in the liver, as seen here. Thickening and hyperemia of the intestine and pale areas in the myocardium also can be seen in some cases, but are not consistently present.

Pathogenesis ■ C. piliforme becomes established in the intestine as a primary infection, usually in the ileum, cecum, or both. It spreads via the portal circulation to the liver, and from there via the blood to other organs, chiefly the heart.

Diagnosis: ■Since the organism cannot be propagated on artificial media, histopathologic diagnoses are made by demonstration of the bacillus in the enterocytes, hepatocytes or cardiac myocytes bordering necrotic foci in tissues stained with silver stains

Treatment: ■ Oxytetracycline at 0. 1 mg/ml water for 30 days was reported to abate mortality of an epizootic in mice. Treatment is usually not warranted

Salmonella ■ ■ Salmonella enteritidis is a gram-negative bacillus. Salmonellae are identified according to serotype, of which over 1500 exist. Virulence varies widely among serotypes; enteritidis and typhimurium are most commonly associated with disease in rodents

Epizootiology ■ Salmonellosis was a major epizootic and enzootic disease of laboratory mice prior to the 1950 s, but clinical salmonellosis in mice is now rare. Transmission is fecal-oral. Salmonellae in general are not very host specific, and carriers are common among exposed populations. Therefore, potential sources of infection for laboratory mice include contaminated food, water, bedding, and fomites

Clinical signs ■ ■ Most infections are subclinical. Signs in mice infected with weakly virulent serotypes vary from none to occasional losses among sucklings and weanlings

Gross lesions ■This mouse with salmonellosis has pale foci of necrotizing and suppurative hepatitis at the margins of the liver lobes (arrows). The spleen is greatly enlarged due to production of increased numbers of neutrophils, or myeloid hyperplasia.

Diagnosis ■ Diagnosis of salmonellosis is by culture and serotyping. Several sites should be cultured, including liver, spleen, mesenteric lymph nodes, blood, and intestinal contents.

Control ■ Special attention should be given to procurement and storage of bedding materials and food, which are easily contaminated by wild rodents. If salmonellosis is diagnosed in a research facility, the facility should be immediately quarantined, the affected populations culled and their environment decontaminated. ■ ZOONOTIC disease!!!