Iowa State University Veterinarian Records, RS 22/6/0/9, University Archives, Special Collections Department, Iowa State University, http://www.add.lib.iastate.edu/spcl/arch/rgrp/22-6-0-9.html
To the silver fox industry, encephalitis is a disease of great importance. It seems to occur only in foxes raised in captivity and is epizootic in character. In the fall and winter months the foxes which will be pelted in the near future are put in one pen, and it is this grouping together which seems to bring on this dreaded disease.
Kjar, Harold A.
"Encephalitis in the Silver Fox,"
Iowa State University Veterinarian: Vol. 5
, Article 11.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol5/iss3/11