Histopathologic and Molecular Characterization of Sarcocystis calchasi Encephalitis in White-winged Doves ( Zenaida asiatica ) and Eurasian Collared Doves ( Streptopelia decaocto ), East-central Texas, USA, 2010-13

Abstract

Sarcocystis calchasi is a recently described apicomplexan parasite that causes encephalitis in avian hosts. We diagnosed one White-winged Dove ( Zenaida asiatica ) and two Eurasian Collared Doves ( Streptopelia decaocto ) in Texas, US, with a history of neurologic signs with protozoal encephalitis. On histologic examination, all three doves had moderate to severe meningoencephalitis characterized by large numbers of plasma cells, lymphocytes, and macrophages with gliosis and astrocytosis. Brain sections from two doves also contained numerous Mott cells. Protozoal schizonts with rosettes or clusters of individual merozoites consistent with Sarcocystis spp. were seen within areas of inflammation. Sarcocysts were also identified in the skeletal muscle of one dove. The PCR and sequencing of brain and skeletal muscle from two doves revealed 99% identity with S. calchasi. The presence of S. calchasi in fatal cases of encephalitis in doves in Texas suggests that the geographic and host ranges of S. calchasi are broader than previously reported.

Keywords: Avian; Sarcocystis; Sarcocystis calchasi; dove; encephalitis; protozoa.

Figure 1

Histologic changes in Sarcocystis calchasi–affected doves from east-central Texas, USA, 2010–13. H&E stain. (A) Cerebrum of a Eurasian Collared Dove (Streptopelia decaocto; dove 3). Inflammatory infiltrate composed of macrophages, lymphocytes, and plasma cells, with perivascular cuffing and gliosis. Bar=25 μm. (B) Brainstem of a White-winged Dove (Zenaida asiatica; dove 1). Gitter cells (arrowheads) and Mott cells (arrow) are common in the areas of inflammation. Bar=25 μm. (C) Cerebrum of a Eurasian Collared Dove (dove 3). A protozoal schizont consistent with Sarcocystis sp. (arrowhead). Bar=20 μm. (D) Skeletal muscle of a Eurasian Collared Dove (dove 2). An intramyocytic thin-walled sarcocyst filled with numerous bradyzoites. Bar=15 μm.

Figure 2

Phylogenetic tree based on a 323–base-pair region of the D2 region of the 28s rRNA gene of Sarcocystis spp. isolates, rooted on Neospora caninum. Sequences generated in this case series are in bold. The tree was generated using the neighbor-joining method, with bootstrap consensus trees inferred from 1,000 replicates.