Parasitemia due to Sarcocystis neurona‐like infection in a clinically ill domestic cat. (11th September 2017) - Zitzer, Nina C.
Abstract: An 8‐year‐old, 6‐kg, male neutered Domestic Shorthair cat was presented to The Ohio State University Veterinary Medical Center (OSU‐VMC) for difficulty breathing. Physical examination and thoracic radiographs indicated pneumonia, a soft‐tissue mass in the left caudal lung lobe, and diffuse pleural effusion. The effusion was classified as modified transudate. Rare extracellular elongated (~5–7 μm × 1–2 μm) zoites with a central round to oval‐shaped purple to deep purple vesicular nucleus with coarsely stippled chromatin and light blue cytoplasm were seen on a peripheral blood smear. Serum IgG and IgM were positive for Sarcocystis sp. antibodies and negative for Toxoplasma gondii antibodies, suggesting that the infection was acute rather than a recrudescence of prior infection. This organism was most consistent with either Sarcocystis neurona or Sarcocystis dasypi based on DNA sequence analysis of PCR products using COC ssRNA, ITS‐1, snSAG2, and JNB25/JD396 primer sets. This is the first report to visualize by light microscopy circulating Sarcocystis sp. merozoites in the peripheral blood of a domestic cat. Therefore, Sarcocystis should be considered as a differential diagnosis in cats with suspected systemic protozoal infection.