Clinicopathological Investigation and PCR-Based Molecular Detection of Toxoplasma gondii Infection in a Red Kangaroo (Osphranter rufus): A Case Report

Toxoplasmosis is a zoonotic disease caused by the intracellular protozoan parasite Toxoplasma gondii, with marsupials recognized as particularly vulnerable hosts. This is a case report of the integrated investigation of fatal illness in a captive red kangaroo (Osphranter rufus). Multisystemic lesions with hemorrhages and congestion of the lungs, liver, spleen, kidneys, heart, and intestines were detected during gross necropsy. Hematological analysis demonstrated leukopenia (2.90 × 109/L), neutropenia (1.19 × 109/L), lymphopenia (1.53 × 109/L), and increased hematocrit (61.2%). The serum alanine aminotransferase level was very high (216 U/L), and urea nitrogen and creatinine were elevated, indicating involvement of the liver and kidneys. A bacteriological investigation based on the sequences of 16S rDNA revealed the presence of Neisseria weaveri from the heart and Staphylococcus arlettae from the kidney; no Salmonella spp. or Clostridium perfringens were isolated. The DNA of T. gondii was detected by PCR in various tissues, including spleen (low-level) and lung (high-level). Pathohistological examination of the spleen demonstrated lymphoid depletion and inflammatory infiltration without tissue cysts, tachyzoites, granulomatous inflammation, or multifocal necrosis. Characteristic lesions are absent, and there is no way to definitively attribute mortality to fatal toxoplasmosis, as the lung had the strongest PCR signal. Collectively, these results support PCR-based molecular detection of disseminated T. gondii DNA and emphasize the necessity of comprehensive histopathological correlation with all PCR-positive organs in future investigations.