Pathology of naturally occurring chlamydiosis in African clawed frogs (Xenopus laevis).

Chlamydiosis was diagnosed in six African clawed frogs (Xenopus laevis) from a tank of laboratory-bred frogs experiencing sudden deaths. Gross findings were hepatomegaly, distention of the gall bladder, and splenomegaly. Hepatic lesions were present in each frog and were characterized by mononuclear cell infiltrates, necrosis of hepatocytes, Kupffer's cell proliferation, and sinusoidal fibrin thrombi. Cholestasis, hemosiderin-laden Kupffer's cells, parenchymal infarction, and multinucleated hepatocytes were less common findings. Other lesions included degenerative and inflammatory changes in the kidneys, epicarditis and myocarditis, and reticuloendothelial cell proliferation, lymphoid depletion, and necrosis in the spleens. Intracytoplasmic inclusions typical of chlamydiae were seen by light microscopy in hepatocytes and reticuloendothelial cells of the spleen. Electron microscopy demonstrated that these inclusions were composed of three distinct types of particles consistent with the life stages described for chlamydiae.