Tissue changes in stomach and intestine were observed associated with nematode larvae infection. This infection causes disintegration of cellular organization of these organs. The changes like, fusion, atrophy of villi, epithelial cells and villous epithelium, sloughing of villi, lengthening of crypt gland and erosion and dislocation of gastric mucosa and shrinkage of tissue has also observed with the infection of acanthocephala, trematode, protozoan and nematode larvae. Lesion and inflammation in stomach and intestine also produced. Severe host tissue reactions resulting into degeneration of mucosal and serosal layers were also observed. The gastric mucosa was distorted and under lying tissues showed hyaline degeneration. This work is useful for teachers, students and researchers in the field of fish histopathology.