A novel Sarcocystis-associated encephalitis and myositis in racing pigeons (Columba livia f. dom.)
Résumé
Sarcosporidian cysts in the skeletal muscle of domestic pigeons (Columba livia f. domestica) have previously been attributed to infections with Sarcocystis falcatula, which is shed with the feces of the opossum (Didelphis virginiana). Here, we describe fatal spontaneous encephalitis and myositis associated with Sarcocystis infections in three flocks of racing pigeons with 47 of 244 animals affected. The clinical course was characterized by depression, mild diarrhoea, torticollis, opisthotonus, paralysis and trembling. Histopathology of 13 pigeons revealed generalized severe granulomatous and necrotizing meningoencephalitis and myositis with sarcosporidian cysts. Light and transmission electron microscopy identified cysts in heart and skeletal muscle of 1 to 2 mm in length and 20 to 50 µm in width that were subdivided into small chambers by fine septae and filled with lancet-shaped cystozoites (7.5 x 1.5 µm) and dividing metrocytes, which is characteristic for Sarcocystis. The cysts had smooth walls and were devoid of protrusions typical for Sarcocystis falcatula. PCR-amplification and sequencing of the internal transcribed spacer region (ITS-1) and the complete 28S rRNA identified a novel Sarcocystis species with only 49 % ITS-1 nucleotide sequence similarity with Sarcocystis falcatula. A phylogenetic comparison of the 28S rRNA revealed close sequence homologies with Frenkelia microti, Frenkelia glareoli and Sarcocystis neurona. The clinical, histopathological, electron microscopical and genetic data are unlike previously described protozoal infections in pigeons, suggesting a novel severe disease in pigeons due to an as yet undescribed Sarcocystis species.
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