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
Because the profit margin in the livestock industry is narrowing year by year, the importance of subclinical disease ever increases. Of major importance in the realm of subclinical disease is parasitism. Although parasites are capable of causing severe morbidity and morality, the usual situation seen from day to day is the insidious, nonspectacular stress placed on animals by subclinical infections by various parasites.
Greve, J. H.
"Parasites in Domestic Animals in Iowa,"
Iowa State University Veterinarian: Vol. 29
, Article 5.
Available at: http://lib.dr.iastate.edu/iowastate_veterinarian/vol29/iss2/5