Leptospira spp. Infection

Leptospirosis in humans is the most widespread zoo­notic disease throughout the world, and wild rats and mice play an important role as maintenance hosts for pathogenic Leptospira.

Mycoplasma haemomuris Infection

Formerly known as Hemobartonella muris, Mycoplasma haemomuris is now classified as a member of the genus Mycoplasma. It is a hemotropic Mycoplasma that infects wild rats and other rodents and at one time was common in laboratory rats. It is transmitted primarily by Polyplax

FIG. 2.40. Colonization of a renal tubular lumen with Leptospira sp. in an infected rat (Warthin-Starry stain). (Source: Tucunduva de Faria et al. 2007. Reproduced with permission from Elsevier.)

spinulosa and can also be transmitted in utero, but apparently inefficiently, since cesarean section is usually successful at eliminating the organism. Mycoplasma hae- momuris can contaminate biological products derived from infected rodents and is infectious in both rats and mice. Natural infections are invariably inapparent, with mild transient bacteremia, splenomegaly, and erythrocytic reticulocytosis. The reticuloendothelial sys­tem, especially the spleen, is critical for clearing the bacteremia. Splenectomy of carrier rats may result in hemolytic anemia with hemoglobinuria and death. Immunosuppression with corticosteroids is ineffective in activating a subclinical infection. Diagnosis can now be achieved by PCR of blood from infected rodents.