Gross and Histopathological Lesion Induced on the Gills Ofbarbus Fish by Monogenea Trematods Habiteting in Western Part of Lake Tana, Amhara Region, Ethiopia

Abstract Back ground: Gill parasitic is common on cultured and wild fish. Many of these species have long been recognized to have the potential to affect the growth, fecundity and survival of hosts.the objective of the study were to determine the prevalence and identify, gross and histopathological lesion of gills caused by Dactylogyrus and Gryodactylus spp. parasitic infection on naturally infected barbus fish.Result: A cross sectional study was conducted from in Lake Tana, amhara region. Three hundred eight four gill specimens were collected from barbus fish and of these, 22 (5.7%) of fish were infected with monogenean parasites. Higher prevalence of Dactylogyrus spp. (4.86%) was recorded than Gryodactylus sp (1.04). Large size fishes (≥ 20cm) were more susceptible to Dactylogyrus spp and Gryodactylus spp. However, highest prevalence of Dactylogyrus sp. was found in large fish size (6.85%). Gryodactylus sp. was not recorded in all small size fish. Descriptive statistics such as percentages was used to describe the nature and the characteristics of the disease. At gross examination of gills, hyperaemia and swollen, excess mucus secretion, paleness, congestion of branchial blood vessel were observed. Gills specimens of infected fish were fixed with10% formalin, for further identification and stained with the haematoxylin-eosin. Histopathological changes included hyperplasia, congestion and mucous cell proliferation of the gill epithelium and damaged primary and secondary lamellae, the uplifting of respiratory epithelial wall and damaged pillar cells. Conclusion: Gross and histopathological changes induced by the Dactylogyrus spp and Gryodactylus spp of parasites adversely affected the proper functioning of the gills of the host fish which can lead to detrimental effect on the health status of the fish and may result in huge economic losses through increased mortality.