Epidemiologic findings from an outbreak of cysticercosis in feedlot cattle.

An outbreak of cysticercosis in a south-central Idaho custom feedlot reached a peak prevalence of 11% in January 1993 and extended from October 1992 through March 1993. Of 5,164 cattle slaughtered from this feedlot during the outbreak, 457 (9%) were cysticercosis infected. Total discounts on the infected cattle at slaughter cost the feedlot $154,400. Most evidence was suggestive of feed-borne transmission of Taenia saginata eggs to the cattle in the feedlot. By use of logistic regression analysis of feedlot records, significant (P = 0.004) association of cysticercosis prevalence at slaughter with days on feed was revealed. Similarly, a decline in cysticercosis prevalence was significantly (P < 0.001) related to the number of days cattle were fed a ration not containing potato byproduct. Although sources other than potato byproduct were systematically evaluated during the investigation, findings suggested that potato byproduct fed in this feedlot was contaminated with T saginata eggs.