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Introduction: Sarcocystis calchasi is an intracellular protozoan parasite belonging to the phylum Apicomplexa. It was identified as the causative agent of pigeon protozoal encephalitis (PPE) during an outbreak in Berlin in 2008. PPE is an ongoing threat as new cases are diagnosed continuously in pigeons in the Berlin area. Birds and mammals usually serve as intermediate hosts of other Sarcocystis spp., thus a retrospective study was conducted to determine whether S. calchasi may be involved in cases of meningoencephalitis of unknown origin (MUO) in mammals.
Materials and Methods: Formalin-fixed and paraffin wax-embedded (FFPE) samples of 142 brains with MUO from different mammalian species (i.e. dog, cat, pig, cattle, sheep, guinea pig, horse, goat, mouse, raccoon, ferret, hamster, mink and mane wolf) collected between 1989 and 2012 were re-examined histologically using HE-stained sections. DNA was isolated from FFPE material and screened by PCR with primers specific for the 18S rRNA and the ITS-1 genes to detect S. calchasi or other apicomplexan parasites, respectively.
Results: In all samples the diagnosis of non-suppurative (lymphoplasmacytic and/or granulomatous) meningoencephalitis was confirmed, but no parasitic structures were found. DNA of S. calchasi or other apicomplexan parasites could not be detected in any of the samples.
Conclusions: Despite the seemingly high prevalence of PPE and persistent threat of S. calchasi in pigeons in the Berlin area, no evidence was found for a role of this parasite in MUO in mammalian species.