Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 27, 2003
Publication Date: April 20, 2003
Citation: LAPOINTE, J.M., DUIGNAN, P.J., BARR, B.C., PETRICH, A.K., MACPHERSON, D.W., GULLAND, F.M., DUBEY, J.P. 2003.MENINGOENCEPHALITIS ASSOCIATED WITH AN UNIDENTIFIED APICOMPLEXAN PROTOZOAN IN A PACIFIC HARBOR SEAL. JOURNAL OF PARASITOLOGY 89:859-862.
Interpretive Summary: Toxoplasma gondii, Neospora caninum and Sarcocystis neurona are related single-celled parasites of domestic and wild animals. Scientists at the Beltsville Agricultural Research Center and the University of California, Davis report a new organism causing encephalitis in a Pacific harbor seal. These findings will be of interest to marine biologists, parasitologists, biologists and pathologists.
A Pacific harbor seal (Phoca vitulina richardsii) was found on the central California coast with neurologic signs and labored breathing, which were unresponsive to treatment. Necropsy revealed a non-suppurative necrotizing meningoencephalitis, a multilocular thymic cyst, and non-suppurative cystitis and renal pyelitis. Microscopic examination revealed protozoa in the brain, thymic cyst and bladder mucosa. Ultrastructurally, the protozoal tachyzoites were different from those of Neospora caninum, Toxoplasma gondii and Sarcocystis neurona; the rhoptries were small and had electron-dense contents, and the organism divided by endodyogeny. Specific antibodies were not detected in serum using agglutination (N. caninum, T. gondii) and immunoblot assays (S. neurona). Immunohistochemistry for these same organisms was negative. Polymerase chain reaction on brain tissue using specific primers did not amplify T. gondii DNA. The meningoencephalitis in this seal thus appears to be caused by a novel protozoan.