Studies on trichodinosis of some freshwater fishes PhD. Fatma Elzahraa A. A. Ahmed Assistant lecture, Zoology Dept., Faculty of Science, Sohag University, Egypt. 2-8-2015

Introduction Like humans and other animals, fishes may suffer from diseases which lead to severe economic losses. Disease problem originates from overcrowding and/or deteriorating water quality such as unsuitable water temperature, pH, carbon dioxide and free ammonia concentrations. Fish diseases can be classified according to the causative agent into: 1. Parasitic diseases 2. Bacterial diseases 3. Fungal diseases 4. Viral diseases 5- Non infectious diseases including : Environmental diseases Nutritional diseases Congenital diseases

About 80% of fish diseases are parasitic especially in warm water fishes (from microscopic protozoans to grossly visible crustaceans and annelids). Ciliates are the most identified protozoan parasites where they can easily spread among most of fish hosts. Ectoparasitic diseases are cited as the major problem in warm water fish farms and the ectoparasites were reported as the largest pathogenic group of organisms causing severe mortalities. The majority of fish ectoparasitic protozoa are commensals which under stress (deteriorated water quality and/or suppressed fish immune system) convert into pathogenic organisms causing serious diseases and mortality especially in fries and fingerlings.

Trichodinosis (slime disease or trichodiniasis) is a parasitic disease caused by ectoparasitic ciliates called Trichodina. 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.

Trichodinosis can be diagnosed based on the clinical signs and identification of the protozoan parasites on the skin scrapings and gill arches. Clinical signs restlessness, loss of appetite, signs of irritation including swimming near borders and scratching against hard objects. Excessive mucous secretions and respiratory function can be impaired in gill infections. The clinical and laboratory diagnosis of trichodinosis can be confirmed with the histopathological studies of skin and gill specimens.

Aim of study this work was carried out to study trichodinosis and its effects on some freshwater fishes including {Oreochromis niloticus (O. niloticus) , Tilapia zilli (T. zilli) , Grass carp (Ctenopharyngodon idella) and catfish Clarias gariepinus (C. gariepinus) } because of their great economic importance.

Materials& Methods

Fish samples: cultured fishes including (180 Oreochromis niloticus, 180Tilapia zilli and 180 Ctenopharyngodon idella) and wild fishes including (180 Oreochromis niloticus, 180 Tilapia zilli and180 Clarias gariepinus) were collected alive in a plastic container partially filled with its local water and aerated by battery aerator. Clinical investigation: The external body surface (skin, fins, gills, eyes and other external features) of alive fishes were examined for the presence of any clinical abnormalities. Prevalence of trichodinosis: The prevalence was calculated as a number of infected fish divided by total number of examined fish multiplied by hundred.

Parasitological investigation: Skin scraps were prepared by curettage the body surface and smears from gills were prepared by cutting the gill arches in petri dish then the filaments were examined under dissecting microscope. High density of trichodinids per microscopic field indicates the infection with trichodinosis. Smears containing Trichodina from the infected fishes were air dried, fixed in methanol, impregnated for 10 min. in 2 % aqueous silver nitrate (AgNo3) solution, washed in distilled water and exposed to ultraviolet light for 30 mins. in order to study details of the parasite (Klein’s silver impregnation technique).

Parasitological identification: Identification of Trichodina could be performed by the morphology and measurements of the denticles surrounding the adhesive disc of the organism via examination under a research microscope at 400X magnification Susceptibility of Trichodina to steamed oil of colophony: Preparation of steamed oil: 500 grams of colophony were well grinded into fine powder, covered with 1 liter tap water and processed to steam distillation at College of Pharmacy, Beni-SuefUniversity. Susceptibility test: The steamed oil of colophony was used at concentrations of 2, 5 and 10 ppm for 30, 60 and 120minutes in water to evaluate its effect on trichodina parasite.

Results

Clinical Signs: 1 3 2 2 1

prevalence of trichodinosis: The prevalence of trichodinosis in cultured and wild O. niloticus in different seasons.

The prevalence of trichodinosis in cultured and wild T The prevalence of trichodinosis in cultured and wild T. zilli in different seasons.

The prevalence of trichodinosis in cultured C The prevalence of trichodinosis in cultured C. idella in different seasons.

Wild C. gariepinus Prevalence % No of diseased fish No of examined fish Season 45 Winter Spring Summer Autumn 180 Total The prevalence of trichodinosis in wild C.gariepinus in different seasons.

Comparison between the prevalence of trichodinosis in the studied wild and cultured fish species: A) - Prevalence of trichodinosis in cultured fish species

B)-Prevalence of trichodinosis in the wild fish species

Parasitological identification:

Trichodina magna Trichodina heterodentata Trichodina sangwala

Susceptibility of Trichodina parasite to steamed oil of colophony: The dosage of 5 and 10 ppm of colophony steamed oil destructed 100% of Trichodina parasites within 30 minutes in vitro.

Summary Clinical investigation of the infected fishes revealed some clinical signs in the form of irritation and respiratory distress. The seasonal prevalence of trichodinosis in the cultured and wild fishes recorded its highest level during summer season and the highest prevalence of trichodinosis was recorded in O. niloticus. The dosage of 5 and 10 ppm of colophony steamed oil destructed 100% of Trichodina parasites within 30 minutes in vitro.

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