Common fish diseases and parasites Introduction, Causal organisms, symptoms and control measures Saprolegniasis, Tail rot/ Fin rot White spot diseases, Dactylogyrosis Argulosis and Asphyxiation Fisheries Program, FAVF, AFU 2 Introduction • Health management program and disease emergency plan- essential for a farm • Disease • Departure from the typical normal state of health of a fish or any other organisms • May be infectious or non-infectious • Infectious- caused by microorganisms including virus, bacteria, fungi, protozoa, worms, crustaceans etc. • Non infectious- nutritional deficiency, dietary toxicity, environmental problems. 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 3 Introduction… • Infectious disease • Complex causes • Prevention and control can be more challenging • Principles of fish health management • Minimization of stress • Confinement of disease outbreak to affected ponds • Minimizing the losses from disease outbreak • Prophylaxis and positive treatment of outbreak • Difficult to conduct a correct diagnosis and timely treatment • Prevention is important 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan Common symptoms/ Signs of sickness • Fish becomes restless or abnormal • Loss of balance and fish is unable to maintain its position in the water column • Fish tends to lie on their side either resting at the bottom or floating at the surface • Tail and fins do not seem to function normally • Persistence discoloration of the body 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 4 Common symptoms/ Signs of sickness • Erosion of scales, fins, gills or part of the skin • Pale gills • Slimy grey excretion on skins • Swelling of abdomen • Bloody or bulging eyes • Slowing down or complete stoppage of feeding 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 5 6 Test for sick fish • Van Dugin (1956) • Hold the fish in position in hand under water • Turn it on its one side • If the eye ball also turns following the turning of bodySick • If the eye ball can maintain its position, able to see the same thing- Good 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 7 Natural resistance of fish • Surface texture • Skin and mucous membrane acts as a screen to keep the infectious micro-organisms out of it. • Lysozyme secreted from the cell can kill bacteria. • Digestive enzymes kill pathogenic microbes entering digestive tract. • Phagocytic function of WBC • Bactericidin in fish blood 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 8 Infectious disease • Can be transferred to other individuals • Sources: • Primary: Sick fish, acts as carriers of pathogens. Infection through direct contact or by discharge of disease causing agents into water. • Secondary: Water coming from diseased ponds, contaminated silt, feeds and gears 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 9 Fungal diseases • Found in water, or on the surface of fish • In certain conditions, they are able to invade the fish tissues • May cause large ulcers and consequent loss of osmotic control • Most obvious and common is Saprolegnia • Found in water everywhere 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 10 Saprolegniasis • Also known as Water mould disease • Causative organism • Saprolegnia parasitica • May develop on dead eggs in incubation tanks • Contaminate healthy eggs on contact • Dead fish/ eggs are fertile medium for the growth • Affect all species in all environments and all ages • All external lesions open the way for this parasitic fungus 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan Saprolegniasis (Symptoms) • Characteristic wooly, whitish or light brown blotches on skin, fins, eyes, mouth and unfertilized eggs. • First indication is dullness of body color 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 11 12 Symptoms… • Ulceration of skin, exposure of jaw bones, blindness, inflammation of liver and intestine • Infected fish rub body against hard surface • Abnormal movement 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 13 Control measures • Injured fish during handling and transportationvulnerable to fungal attack • Actions to avoid or treat the causes of injuries and unhealthy environment • If only a small part of skin is infected • Touched with 1;10 solution of Iodine or 1% K2Cr2O7 • Dip treatment (5-10 minutes) • • • • 0.3% Common salt 1:2000 CuSO4 1:1000 KMnO4 1:10000 Malachite green (3 seconds) 2/24/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 14 Control measures… • Treating the fertilized eggs • 3-4% formalin for 10 minutes • 1-5% salt for 10 minutes • Using 0.02 g/L Malachite green for 20-25 minutes 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 15 Bacterial diseases • Single-celled organisms of different shapes • Occur in small numbers on the skin or inside the body • Might be beneficial as well as notorious • Many bacteria responsible for fish diseases • Stressed fish more vulnerable to bacterial infection • Present in many secondary infections 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 16 Tail rot or fin rot • Causal organism • Flavobacterium columnaris or Pseudomonas fluorescens • Most contagious disease in carps • Symptoms • Distinct white line seen at the margin of the fin in early stage of the disease • Line moves towards the base of fin • Fin becomes torn, and entire fin is destroyed after sometime • In severe stage, infection spread on the body and invade the connective tissues too. 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 17 Tail rot or fin rot 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 18 Control measures • Oxytetracycline or terramycin orally @7.5 g/ 100 kg feed per day for 2 weeks • Dip in 500 ppm CuSO4 for 1 minute • Bath in 5 ppm acriflavine for 1 hour • Crowding, water pollution and stress must be avoided 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 19 Bacterial diseases… • Furunculosis • Aeromonas salmonicida • Dropsy • Pseudomonas punctata • Columnaris • Flexibacter columnaris • Bacterial gill disease • Myxobacterium spp. 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 20 Protozoan diseases • Causes external and internal diseases • Main victims: fry and fingerlings stages • Adults too are susceptible • Some causes anemia, trauma, abnormal physiological changes, suffocation & death • Some responsible for secondary infections 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 21 White spot disease • Also known as Ichthyophthiriais • Causative organism • Ichthyophthirius multifiliis • One of the most dangerous fish parasites • Burrows beneath the fish skin and often kills • Parasite is spherical or ovoid ciliate with U or horseshoe shaped nucleus 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 22 Symptoms (White spot) • Small whitish nodules/cysts of about 1 mm diameter appear on the skin, gills and fins. • In advanced cases, the entire body surface of the fish may become covered with nodules/cysts. 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 23 Symptoms… • Swims and responds to stimulus slowly, spending much time at the bottom of the pond. • Continually rubs itself against other objects or jumps out of the water at the early stage. • The parasite may invade the cornea and causes inflammation and blindness. 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 24 Control measures • Treatment is difficult • Variability in the time of lifer cycle completion • Not possible to eliminate the parasite when under the epithelial layer of fish • Treatment aimed to eliminate the unprotected freeswimming stage of parasite. • Disinfecting the pond with lime @500 kg/ha done to prevent transmission. • Care on stocking density, quarantine and disinfection of fingerlings 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 25 Control measures… • Treatment • Bath fingerlings in 6.0 ppm malachite green for 30 min. • Dip treatment in 1:5000 formalin for 1 week • Dip in 2-3% salt solution for 2-3 min for 1 week • Pond disinfection with CuSO4 @ 0.5 ppm weekly. • Avoid the brood with white spot for breeding. 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 26 Parasitic diseases • Blue slime disease/ Ichthyobodosis • Ichthyobodo necator • Trichodiniasis • Trichodina spp. • Chilodonellosis • Chilodonella cyprinid • Whirling disease/ Myxobolosis • Myxobolus cerebralis • Costiasis • Costia necatrix 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 27 Disease caused by worms • Large number of external and internal parasitic worms • Might be monogenea and digenea • May be • Trematodes- Gyrodactylus, Dactylogyrus • Cestodes- Ligula • Nematodes- Philometra, Camallanus • Acanthocephala- Acanthogyrus and • Hirudinea- Hemiclepsis 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 28 Dactylogyrosis • Causative organism • Dactylogyrus vastator • Known as gill fluke • Worm of about 1.1 mm size • Two pairs of eyes at anterior end • Seven pairs of marginal, and 1 pair of central hooks • Oviparous • Miracidia stage attack the gills of fish and feed on the blood 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan Symptoms (Dactylogyrosis) • Faded gills • Gill necrosis • Loss of gill functions and partial suffocation (respiratory distress) • Excessive mucus secretion on the gills and skin • Lethargy, swimming near surface, seeking the sides of the ponds, refuse food 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 29 Control measures (Dactylogyrosis) • Pond treatment • Dipterex @ 0.2 ppm • Dry and disinfect using lime • Dip treatment • Malachite green 1:15000 for 15 mins • Acetic acid 5% for 1 min • Bath treatment • Common salt 2.5% for 1 hour • 0.7% common salt for indefinite period 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 30 Disease caused by crustaceans • Generally ectoparasites • Skin, fins and gills of fish • Mainly copepods • Argulus sp. • Ergasilus sp. • Lernea sp. • Caligus sp. • Pseudocycnus sp. • Clavellisa sp. 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 31 32 Argulosis/ Fish Lice • Causative organism • Argulus foliaceus • Adult ♂: 4-5 mm and ♀: 6-7 mm • Common ectoparasite, living on skin, fins and gills • Body shape is broad, flat and oval • Sucks blood • Attach by means of hooks and two suckers situated under eyes • Leaves host to deposit eggs of suitable submerged substratum 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 33 Argulosis… 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 34 Symptoms (Argulosis) • Small open wounds on fish body • Secondary infection by fungal diseases • Red blotches on skin caused by parasite attachment • Large number of parasites on infected areas • Fish rubs itself against other objects or jumps out of water • Sucks the blood, fish becomes weaker and cause death. 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan Control measures (Argulosis) • Pond treatment • Dipterex @ 0.25 ppm, repeatation twice daily • Drying and leaving ponds for some period • Dip treatment • 3-5 minutes bath in 2 % common salt solution • Glacial acetic acid 500-1000 ppm for 5 min • Indefinite treatment • 0.25 ppm KMnO4 in pond • Removal of parasites by forceps followed by a bath in weak KMnO4 solution for 2 - 3 minutes. • Use of sticks as egg traps: Argulus lays its eggs on them and by systematic daily removal of stick 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 35 36 Non-infectious diseases • Non-transmittable diseases • Might be due to • Environmental, Nutritional reasons and Genetic reasons • Although non-infectious, may cause mass mortality • • • • • • • Asphyxiation Gas bubble disease Mechanical trauma Thermal trauma Nutritional deficiency diseases Dietary toxins Anomalies and genetic disorders 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 37 Asphyxiation • Occurs due to low DO in water • A frequent problem during summer in ponds with heavy algal bloom • Fish found dead and stressed at dawn when DO is below 1 mg/L • Larger fish die first, and water often changes in smell and color 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 38 Symptoms (Asphyxiation) • Fish show sign of suffocation • Many fish comes to water surface to gulp air frequentlyPiping • Fish aggregate near water inlet • Mouth wide open, gill opercula raised and gill spread wide apart in dead fish • Mass mortality of fish in the morning 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 39 Control measures • Elevating DO level using commercial aerators • Adding fresh and cool water by spraying on surface • Thinning out of fishes • If temperature is too high, drain out the bottom water and supply cool water • Liming the pond @ 500 kg/ha • Decrease the oxygen consumption by bottom mud • Using chemicals like KMnO4 @ 1-2 ppm 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan 40 Thank You End of the Course Meet you in Practical Classes All the Best for Upcoming Examinations 2/25/2023 Fisheries Program, FAVF, AFU © Rahul Ranjan
