Review/Oorsig Volume 22, Issue 05 - Page 11

Volume 22 • Issue 05 • 2018 Histologically numerous large intra-histiocytic protozoal cysts noted in the dermis, subcutis and intermuscular fascia. Cysts are surrounded by a rim of cytoplasm containing multiple nuclei of the host cell histiocyte and enclosed by a hyaline wall (arrows). Images provided by Vetdiagnostix. Life cycle remains unknown but is presumed to be similar to Toxoplasma with members of the cat family as the final host and bovines and other species (which develop clinical disease), as the intermediate hosts. After ingestion of oocysts by the intermediate hosts, sporozoites enter circulation with multiplication phases in endothelial cells initiating vasculitis accounting for the anasarca stage. Histiocytes encompassing or in close association with these vessels are then invaded and the large cystozoite stages develop in these activated histiocytes and it is this phase which induces the chronic scleroderma stage. Cysts are often visible to the naked eye on the conjunctiva and nasal mucosa. Image provided by Bergbos Dierekliniek 11