Cerebral Toxoplasmosis in Striped Dolphins (Stenella coeruleoalba) Stranded Along the Ligurian Sea Coast of Italy

Abstract

This article reports the results of necropsy, parasitologic, microbiologic, histopathologic, immunohistochemical, indirect immunofluorescence, biomolecular, and serologic investigations on 8 striped dolphins ( Stenella coeruleoalba) found stranded from August to December 2007 on the Ligurian Sea coast of Italy. Severe, nonsuppurative meningoencephalitis was found in 4 animals, as characterized by prominent perivascular mononuclear cell cuffing and macrophage accumulations in neuropil. These lesions were associated with mild lymphocytic–plasmacytic infiltration of choroid plexuses in 1 dolphin. Toxoplasma gondii cysts and zoites, confirmed by immunohistochemical labeling, were scattered throughout the brain parenchyma of 2 of the 4 dolphins. No viral inclusions were seen in the brain of any animal. Other findings included severe bronchointerstitial pneumonia and pulmonary atelectasis, consolidation, and emphysema. Parasites were identified in a variety of organs, including lung ( Halocerchus lagenorhynchi). Microbiologic and serologic examinations for Brucella spp were negative on all 8 dolphins. The 4 animals with meningoencephalitis had serum antibodies against T gondii (titers ranging from 1:80 to 1:320) but not against morbillivirus. In contrast, the other 4 dolphins were seropositive for morbillivirus (with titers ranging from 1:10 to 1:40) but seronegative for T gondii. No morbillivirus antigen or nucleic acid was detected in the tissues of any dolphin. It is concluded that the severe lung and brain lesions were the cause of death and that T gondii was the likely etiologic agent of the cerebral lesions. Morbillivirus infection was not considered to have contributed to death of these animals.