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