An estimated 650,000 Nanophyetus salmincola were recovered from the small intestine of a wild female cougar kitten (Felis concolor). The trematodes stimulated marked mucosal thickening in the duodenum and jejunum and caused a marked enteritis. Malnutrition was listed as the cause of death due to impaired nutrient absorption resulting from the combined effects of the diarrhea and thickening of the intestine.