title: Sarcocystis calchasi has an expanded host range and induces neurological disease in cockatiels (Nymphicus hollandicus) and North American rock pigeons (Columbia livia f. dom.).
abstract: Pigeon protozoal encephalitis (PPE) is an emerging central nervous system disease of pigeons (Columba livia f. domestica) caused by the apicomplexan parasite Sarcocystis calchasi. The intermediate host specificity of S. calchasi had been considered high, as domestic chickens were resistant to experimental infection. Here, we have re-evaluated this concept and expanded the known host range of S. calchasi by experimental infection of cockatiels (Nymphicus hollandicus), a species distantly related to pigeons. In this work, a group of eight cockatiels were experimentally infected with S. calchasi, which resulted in a biphasic central nervous system disease that paralleled PPE in many aspects, albeit with a more diverse pathology. All cockatiels became lethargic and polyuric between days 7 and 13 pi and during that time schizonts of S. calchasi were found primarily in the liver and spleen accompanied by necrosis and inflammation. As with pigeons, neurological signs occurred during a chronic phase of the disease in three cockatiels between 57 and 63 dpi. However, all five cockatiels necropsied in that period, or at the end of the trial at 76 dpi, had a severe lymphohistiocytic and necrotizing encephalitis. No tissue cysts were found in the heart, and cockatiels infected with 10(5) sporocysts only had a negligible parasite load in skeletal muscles despite the presence of severe central nervous system lesions. Notably, intralesional schizonts were identified in the brain of one cockatiel. In contrast to previous results, intralesional schizonts were also identified in the brains of three of six naturally infected pigeons from Minnesota and Missouri examined as part of an epidemiological investigation. In both the cockatiel and the pigeons, tissue cysts were found concurrently with schizonts suggesting an uncommon phenomenon in the Sarcocystis life cycle. Based on the results of this study, transmission of S. calchasi to avian species other than the domestic pigeon is possible. These findings suggest a, so far, unmonitored prevalence of S. calchasi in avian populations and highlight a possible ongoing dissemination of this parasite in the Northern Hemisphere.
authors.affiliation: Institute of Veterinary Pathology, Department of Veterinary Medicine, Freie Universität Berlin, Robert-von-Ostertag Str. 15, 14163 Berlin, Germany. Electronic address: olias@borcim.wustl.edu.
authors.forename: Philipp
authors.initials: P
authors.lastname: Olias
authors.affiliation: Clinic for Birds, Reptiles, Amphibians and Fish, Department of Veterinary Medicine, Justus-Liebig-Universität Giessen, Frankfurter Str. 91-93, 35392 Giessen, Germany.
authors.forename: Kristina
authors.initials: K
authors.lastname: Maier
authors.affiliation: Department of Veterinary Population Medicine and Minnesota Veterinary Diagnostic Laboratory, University of Minnesota, 1333 Gortner Ave., St. Paul, MN 55108, USA.
authors.forename: Arno
authors.initials: A
authors.lastname: Wuenschmann
authors.affiliation: Wildlife Rehabilitation Center of Minnesota, 2530 Dale St., N. Roseville, MN 55113, USA.
authors.forename: Leslie
authors.initials: L
authors.lastname: Reed
authors.affiliation: Department of Veterinary Population Medicine and Minnesota Veterinary Diagnostic Laboratory, University of Minnesota, 1333 Gortner Ave., St. Paul, MN 55108, USA.
authors.forename: Aníbal G
authors.initials: AG
authors.lastname: Armién
authors.affiliation: Veterinary Medical Diagnostic Laboratory, University of Missouri, P.O. Box 6023, Columbia, MO 65205, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Shaw
authors.affiliation: Institute of Veterinary Pathology, Department of Veterinary Medicine, Freie Universität Berlin, Robert-von-Ostertag Str. 15, 14163 Berlin, Germany.
authors.forename: Achim D
authors.initials: AD
authors.lastname: Gruber
authors.affiliation: Clinic for Birds, Reptiles, Amphibians and Fish, Department of Veterinary Medicine, Justus-Liebig-Universität Giessen, Frankfurter Str. 91-93, 35392 Giessen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Lierz
mesh_terms: D000818:Animals; D001715:Bird Diseases / Q000469:parasitology* / Q000473:pathology; D046410:Cockatoos / Q000469:parasitology*; D010856:Columbidae / Q000469:parasitology*; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D058507:Host Specificity; D009422:Nervous System Diseases / Q000469:parasitology / Q000473:pathology / Q000662:veterinary*; D012522:Sarcocystis / Q000502:physiology*; D012523:Sarcocystosis / Q000469:parasitology / Q000473:pathology / Q000662:veterinary*
chemical_list: D021903:DNA, Ribosomal Spacer
keywords: Apicomplexa; Bird; Parrot; Protozoa; Psittaciformes; Sarcosporidiosis