A 3 year-old Aberdeen-Angus cow, from Northeast Oklahoma was submitted for necropsy examination to the Oklahoma Animal Disease Diagnostic Laboratory during the late month of May. The cow was found lying down with a body temperature of 104°F and was not able to recover. At necropsy marked acute, multifocal myositis was observed as well as the following structures (Images 1 and 2).
Image 1: Histologic muscle preparation.
Image 2: Histologic muscle preparation (40x objective).
Cattle become infected when they ingest infective sporocysts discharged in dog feces. Two generations of schizogony occur in the vascular endothelium of cattle, with the first one happening in the mesenteric arteries and the second one in the endothelium of capillaries throughout the body. The merozoites released from second generation schizonts enter striated muscle cells and in certain cases, nerve cells to from sarcocysts. Sarcocyst formation is a slow process requiring several months. Dogs become infected when they ingest uncooked beef containing sarcocysts of S. cruzi.
Even though bovine sarcocystosis is mainly subclinical, if high number of sporocysts are ingested over a short time a clinical disease can occur. In this case the finding of S. cruzi was incidental and not related to the cause of death.
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