Fulminant Pneumonia Due to Reactivation of Latent Toxoplasmosis in a Cat—A Case Report

Abstract

<i>Toxoplasma (T.) gondii</i> is an obligate intracellular parasite with felids, including domestic cats, as definitive hosts. In immunocompetent individuals, <i>T. gondii</i> infection is usually asymptomatic. However, under immunosuppression, it may have severe pathological impacts, which often result from the reactivation of a chronic infection. In this case study, a 21-month-old female domestic shorthair cat—diagnosed with primary immune-mediated hemolytic anemia three months prior and treated with cyclosporine and prednisolone—presented with acute tachypnea, dyspnea, diarrhea, and anorexia. Thoracic radiography suggested severe pneumonia. Testing for <i>Mycoplasma</i> spp., <i>Anaplasma</i> spp., <i>Ehrlichia</i> spp., and lungworm infection was negative. Serology for <i>T. gondii</i> revealed seroconversion of IgG, but not of IgM, indicating previous exposure to <i>T. gondii</i>. The cat remained stable but tachypneic for three days, followed by an acute onset of dyspnea and clinical deterioration, after which euthanasia was elected. Numerous protozoa were present in a postmortem transtracheal bronchoalveolar lavage and fine-needle aspiration of the lung. Microsatellite typing classified the extracted DNA as <i>T. gondii</i> type II variant TgM-A. This case demonstrates that <i>T. gondii</i> reactivation, leading to fulminant pneumonia, can be a sequela of immunosuppressive treatment in cats and should, therefore, be considered as a differential diagnosis in immunosuppressed cats with acute-onset respiratory signs. Rapid diagnosis may prevent fatal consequences.