Meningoencephalitis Due to a Sarcocystis Neurona-like Protozoan in Pacific Harbor Seals (Phoca vitulina richardsi)

• Published in: The Journal of parasitology 1998-12, Vol.84 (6), p.1184-1189
• Main Authors: Lapointe, Jean-Martin, Duignan, Padraig J., Marsh, Antoinette E., Gulland, Frances M., Barr, Bradd C., Naydan, Diane K., King, Don P., Farman, Cindy A., Kathy A. Burek Huntingdon, Lowenstine, Linda J.
• Format: Article
• Language: English
• Subjects: Animal protozoal diseases; Animals; Antibodies, Protozoan - blood; Biological and medical sciences; Cerebellar Cortex - parasitology; Cerebellar Cortex - pathology; Encephalitis; Female; Immunohistochemistry; Infections; Infectious diseases; Male; Marine; Medical sciences; Meningoencephalitis; Meningoencephalitis - parasitology; Meningoencephalitis - pathology; Meningoencephalitis - veterinary; Merozoites; Microscopy, Electron - veterinary; Parasitic diseases; Parasitology; Pathology; Phoca vitulina richardsi; Placenta - pathology; Pregnancy; Pregnancy Complications, Parasitic - parasitology; Pregnancy Complications, Parasitic - pathology; Pregnancy Complications, Parasitic - veterinary; Protozoa; Protozoal diseases; Sarcocystis - immunology; Sarcocystis - isolation & purification; Sarcocystis - ultrastructure; Sarcocystis neurona; Sarcocystosis - parasitology; Sarcocystosis - pathology; Sarcocystosis - veterinary; Sarcocysts; Schizonts; Seals; Seals, Earless - parasitology; USA, California; Veterinary medicine
• ISSN: 0022-3395; 1937-2345
• DOI: 10.2307/3284670

Seven Pacific harbor seals with meningoencephalitis associated with Sarcocystis neurona-like protozoa are described. Six of the 7 seals were free-ranging and were found stranded over an 80-km stretch of central California coastline; the other was captive. All had marked to severe nonsuppurative meningoencephalitis, most severe in the cerebellar cortex. Immunohistochemistry for S. neurona antigens was positive on brain tissue in all cases, revealing numerous merozoites as well as developing and mature schizonts, including rosette forms. Electron microscopy performed on 3 animals revealed merozoites and schizonts consistent with Sarcocystis sp., with the absence of rhoptries in merozoites, lack of a parasitophorous vacuole around schizonts, and division by endopolygeny. Serology using western blotting revealed the presence of anti-S. neurona immunoglobulins in the sera of 4 of 5 seals tested. Four animals also had a concurrent mild to moderate nonsuppurative myocarditis; in 1 seal, rare sarcocysts of undetermined species were present within cardiomyocytes.