Multisystemic infection with an Acanthamoeba sp in a dog

Case Description—A 10-month-old Boxer was evaluated for fever and signs of cervical pain. Clinical Findings—Physical examination revealed lethargy, fever, and mucopurulent ocular and preputial discharge. On neurologic examination, the gait was characterized by a short stride. The dog kept its head flexed and resisted movement of the neck, consistent with cervical pain. Clinicopathologic findings included neutrophilic leukocytosis, a left shift, and monocytosis. Cervical radiographs were unremarkable. Cerebrospinal fluid analysis revealed neutrophilic pleocytosis and high total protein content. On the basis of signalment, history, and clinicopathologic data, a diagnosis of steroid-responsive meningitis-arteritis was made. Treatment and Outcome—The dog was treated with prednisone (3.2 mg/kg [1.45 mg/lb], PO, q 24 h), for 3 weeks with limited response. Consequently, azathioprine (2 mg/kg [0.9 mg/lb], PO, q 24 h) was administered. Three weeks later, the dog was evaluated for tachypnea and lethargy. Complete blood count revealed leukopenia, neutropenia, and a left shift. Thoracic radiography revealed a diffuse bronchointerstitial pattern. The dog subsequently went into respiratory arrest and died. On histologic evaluation, amoebic organisms were observed in the lungs, kidneys, and meninges of the brain and spinal cord. A unique Acanthamoeba sp was identified by use of PCR assay. Clinical Relevance—This dog developed systemic amoebic infection presumed to be secondary to immunosuppression. The development of secondary infection should be considered in animals undergoing immunosuppression for immune-mediated disease that develop clinical signs unrelated to the primary disease. Although uncommon, amoebic infection may develop in immunosuppressed animals. Use of a PCR assay for identification of Acanthamoeba spp may provide an antemortem diagnosis.