THE NATURE AND SEVERITY OF HISTOPATHOLOGICAL CHANGES IN AFRICAN CATFISH Clarias gariepinus INFECTED WITH ICHTHYOPHTHIRIASIS

Majority of cultured fishes are infected by a protozoan ectoparasite, Ichthyophthirirus multifilis. With increasing investment in aquaculture and closer examination of factors such as fish diseases that contribute to the risks faced by an aquaculturist, the concept of integrated health protection is very paramount. Clarias gariepinus, which grows fast, easily raised in captivity, is popularly cultured in Nigeria. The parasitic infection of I. multifilis mainly in the gill and skin of fish, contribute to the diverse tissue damages. Histopathological changes in the gill and skin of Ich-infected Clarias gariepinus was studied. A total of 120 healthy parasite-free post juvenile catfish were disinfected with 0.05% potassium permanganate. The infective stage, theront of I. multifilis was obtained from the wild as a parasite source and then mass produced continuously by serial passage by cohabitation.  The fish were randomly distributed into three groups with 20 fish per replicate (group A, Normal control, Group B (infected with 24,000 theronts and group C, 44,000 theronts). The skin and gill tissues (n=3) were excised and quickly subjected to histological processing. Severity of the lesion was progressively classified in three stages of tissue damage. The values considered to be non-parametric were subjected to Kruskal-wallis and Mannwhitney U test using SPSS version 20. The skin and gill of uninfected fish showed normal skin morphology such as intact collagen cells, chromatophores and intact primary and secondary lamellae.  Significant differences (P<0.05) were observed in their lesion scores between group B and C. Histopathological changes observed in gill of group B and C were aneurysm, edema, epithelial lifting with evidence of trophont accumulation, inflammation, distortion of lamellae. In the skin, hyperemia, abscess formation, edema and inflammatory responses were observed at different degrees between groups B and C. Significant differences (P<0.05) in the degree of severity of lesions were observed in groups B and C. The observed tissue damages in the gill and skin of ich-infected fish proved that both routes are mainly compromised when there is an outbreak of Icthyophthiriasis. Therefore, the need for proper sensitization in promoting aquatic life safety and proper disease management is paramount.