It is well known that the duodenum of mice or rats infected with Fibricola seoulensis shows atrophy of villi (shortening, blunting, widening, fusion) and hyperplasia of crypts. This study was performed to observe healing process of these pathological changes after deworming with anthelmintic treatment. Albino rats infected each with 1,000 metacercariae of F. seoulensis were treated with single dose of 10 mg/kg praziquantel on day 15 post-infection. On day 1, 3, 5, 7, 15, 21 and 28 after the treatment, they were sacrificed and their duodenums were histopathologically studied. Control (uninfected) rats showed their normal finger-like projections of duodenal villi and well arranged crypts. In comparison, untreated (infected) controls revealed severe mucosal changes characteristic of villous atrophy and crypt hyperplasia in their duodenum. The damaged duodenal mucosa was found to restore its normal morphology after praziquantel treatment; until day 3 post-treatment the mucosa was severely atrophied; on day 5 long and slender villi sometimes appeared among the fused and stout ones; after day 15 the villi were in their normalizing process. From this experiment, it was shown that the mucosal changes in the duodenum of rats caused by F. seoulensis infection were completely reversible in 21-28 days after anthelmintic treatment.
