Histopathological changes in the intestine of sharptooth catfish, Clarias gariepinus naturallyinfected with the cestode, Tetracampos ciliotheca

The aim of this study was to describe the histopathology of the intestine of the sharptooth catfish, Clarias gariepinus (Burchell, 1822) naturally infected with the bothriocephalidean cestode, Tetracampos ciliotheca Wedl, 1861. A total of 45 fish (10-54 cm) were collected from the Vaal Dam, (Gauteng Province, 26°52.249'S, 28°10.249'E), South Africa. A total of 39 (86.7%) of the catfish examined were infected with the cestode. Heavily infected fish (gt; 20 worms per individual host) were chosen for this study. Intestinal tissue with parasites in situ were fixed and processed for routine histological investigation. The worms penetrated deep into the mucous membrane with their scolex, leaving the proglottids nestled between villi and extending into the lumen. This attachment resulted in acute mechanical effacement of the epithelium, disruption of the lamina propria and desquamated cells mixed with mucus. In addition, mild fibrosis was occasionally evident in the lamina propria, in regions adjacent to the scolex. In some cases, the scolex fully penetrated the mucosal layer and extended to the level of the submucosal layer resulting in ulceration and oedema in the lamina propria. Coagulation necrosis was evident on the ulcer, which presented a granular substance that had a characteristic amorphous material. Furthermore, the nuclei of epithelial cells adjacent to the parasite displayed chromatin clumping and clearing. Several conspicuous granulomas of unknown etiology were observed in the muscularis of the intestine. There was no evidence for the presence of secondary microbial infections in this study. The histopathological changes caused by this parasite on these wild fish were mild and did not seem to cause any serious threat to infected hosts. In addition, no dead tapeworms were encountered during dissection.