. The Second International Conference on New Horizons in Basic and Applied Science. www.nhbas.com Histopathological studies on trichodinosis of farmed Oreochromis niloticus Mohamed A. Adly1, Mohamed A. A. Abd El-Galil2, Fayza M. Soliman1 and Fatma El Zahraa A. A. Ahmed1 Email: m.adly@yahoo.com 1-Depart. of Zoology, Fac. of Science, Sohag Univ., Egypt. 2-Depart. of Fish Dis. & Manage. Fac. Vet. Med., Sohag Univ., Egypt. 1-Introduction Trichodinosis (slime disease or trichodiniasis) is a parasitic disease caused by ectoparasitic ciliates calledTrichodina. Which are global parasites exist throughout the year. Trichodina is circular in shape, 50 microns in diameter; side view of the organism reveals a saucer or dome shape with rows of cilia at both ends and the rest of the body is non-ciliated. The protozoan ciliates including Trichodina are mainly ectocommensals feed on the disrupted cells of the host gills and/or skin. During stress conditions as deteriorated water quality and/or overcrowding in farms, the parasite multiplies rapidly and proliferates to pathogenic form causing severe irritation for the skin and gills as a result of crawling movement and its adhesive disc leading to serious diseases with signs of irritation and respiratory distress. 2- Goals This work aimed to study the histopathological effects of trichodinosis on O. niloticus as the most economically important species of farmed freshwater fishes where the ectoparasites including Trichodina sp. were reported as the largest pathogenic group of organisms that cause severe mortalities in fish farms. (1) detachment of scales, (2) fin rot, (a) Trichodina parasites from a skin scrap (100X) and (b) enlarged Trichodina parasite (400X). b a 3- Materials and Methods 3.1- Clinical investigation: The external body surfaces (skin, fins, gills, eyes and other external features) of alive fish were examined for the presence of any clinical abnormalities. 3.3- Histopathological examinations: Light Microscopy: Skin and gills were processed for the normal histological and histopathological studies. 3.2- Parasitological investigation: Skin scraps and gills smears were examined under dissecting microscope (10 and 40X) lens. High density of trichodinids per microscopic field indicates the infection with trichodinosis. Scanning Electron Microscopy (SEM): Samples from infected skin and gills were fixed in 2.5% glutaraldehyde in 0.1M phosphate buffer (pH 7.4) and processed for scanning electron microscopy. a d b c 4-Results A- Skin 100X D SM E SM 100X 100X CB SM 100X 400X E E CB Intact skin consist of (E) Epidermis, (D) Dermis filled with collagen bundles (CB) and underlined with (SM) Skeletal muscles. Moderate infection causing detachment and vacuolations within the epidermis (triangles), disarrangement of collagen bundles in dermis (stars). Severe infection causing sloughing of the epidermis, disarrangement of collagen bundles in dermis (stars) and aggregation of melanin-carrying cells forming a thick dark band between the dermis and skeletal muscles (arrows). Scanning electron micrographs: (a & c) intact skin surface with clear & regular squamous epithelium. (b & d) infected skin surface with cracked and irregular thickness of squamous epithelium with marked ulceration. B- Gills SL PL 400X E Pl Sl 100X m p c 400X Sl Pl a ir n d b c Moderate infection causing hyperplasia at tips and/or bases of some 2dary lamellae leading to fusion of some adjacent lamellae (arrows). Inflammatory cells appeared at the bases of some 2dary lamellae (double head arrows). Control gill arch bears (Pl) Primary lamellae, (Sl) Secondary lamellae and (E) stratified epithelium, (m) mucus cell, (c) chloride cell and (p) pillar cell. 100X PL SL E 400X PL E SL 400X Scanning electron micrographs: (a & c) intact gill surfaces, (Pl) primary lamellae, (Sl) secondary lamellae and (ir) clear inter-lamellar region. (b and d) infected gill filaments with irregular thickness and cracked surfaces. Moreover, small notches (n) appeared clearly on the surfaces and two secondary lamellae appeared adhere to each other. Severe infection causing hyperplasia (arrows), intense lamellar epithelial lifting in both primary and 2dary lamellae (double head arrows) and aggregation of inflammatory cells between the 2dary lamellae (stars). Severe infection causing severe hyperplasia in some primary lamellae (arrows) which lead to shortening of adjacent 2dary lamellae & complete fusion of some adjacent 2dary lamellae. 6-Conclusions On the light of above mentioned results it could be concluded that the trichodinosis affects the most freshwater fishes causing serious damage for the diseased fish. Histopathological investigation of the infected skin and gills revealed proliferative changes in the epithelial lining cells causing several clinical signs including irritation and respiratory distress. 6-References [1] Soliman Fayza, M.; Abd El-Galil, M. A. ; Adly, M. A. and Ahmed Fatma El Zahraa, A. A. (2013): Studies on trichodinosis of some cultured freshwater fishes at Sohag governorate. J. life Sci., 10(4): 1400-1409. [2] Hassan, M.A.H. (1999): Trichodiniasis in Farmed Freshwater Tilapia in Eastern Saudi Arabia. J. KAU: Mar Sci., 10: 157-168. Session VI: Basic and applied Zoological researches. August 1- 3 – 2015.