FISH PARASITES

• Arthropod Parasites of Fishes

  • Belong to Class Crustacea, majority of which are members of Subclass Copepoda
  • Bodies are segmented, covered by a rigid or semi-rigid chitinous exoskeleton
  • Thorax and head are fused into cephalothorax
  • All appendages are jointed
  • These feed on blood and/or epithelium. Effects include anemia, ulceration, and necrosis of the skin. Infestations also often results to secondary bacterial infection
• Arthropod Parasites of Fishes

  • Argulus spp.
  • Caligus spp.
  • Ergasilus spp.
  • Lernaea spp.
  • Alitropus spp., Nerocila spp. and Rhexanella spp. (isopods)

  
• Argulus


  Freshwater fish louse
• Argulus


  • Carapace is horseshoe-shaped
  • Can be found in body surface, fins, buccal or opercular mucosa with two conspicuous black spots
  • Attachment sites are hemorrhagic or ulcerated, which may become necrotic
  • Clinical sign includes erratic swimming, "flashing" and poor growth
• Caligus spp.


  Marine fish lice
• Caligus spp.


  • Transparent, appear as white patches on infestation sites such as body surface, fins, and gills
  • Infested areas have no scales, are hemorrhagic or ulcerated
  • Affected fish have lumpy body surface, swims sluggishly, shows flashing behavior, inappetence, and excessive mucus production

  
• Ergasilus spp.


  • White to dark brown in color, females may have two elongated white sacs
  • Infestation sites are gills and body surface
  • Destruction of the gill filaments can cause respiratory dysfunction and epithelial hyperplasia, which results to emaciation, retarded growth and sexual maturation
  • Fish may become listless and eventually die
• Lernaea spp.


  Anchor worms

  
• Lernaea spp.


  • Only females are parasitic, which can be seen protruding from the nostrils, body surface, bases of fins, gills, and buccal cavity. Egg sacs are present in its posterior end
  • Skin and muscle in infestation sites are swollen. Ulcers may develop and lead to necrosis
• Isopod parasites


  Include Alitropus spp., Nerocila spp., and Rhexanella spp.
• Isopod parasites


  • Affect tilapia, milkfish, sea bass, mullet, rabbitfish, grouper, and goby
  • Sites of attachment are body surface, mouth, nasal cavity, opercular cavity and gills
  • Clinical signs include reduced opercular movement, inappetence, anemia, slow growth rate and rubbing against objects
• Control of Parasitic Crustacea

  1. Water treatment with:

  • Potassium permanganate for Argulus
  • Dipterex for Argulus and Ergasilus
  • Neguvon and hydrogen peroxide for Caligus
  • Formalin for Caligus and isopods
  • Bromex for Ergasilus
  • 3-5% salt solution for larvae of Lernaea

  2. Use of water filters

  3. Removal of infested fish and reduction of fish density

  4. Complete drying of pools to keep eggs, larvae, and adults between cycles
• Arthropod Parasites of Pinnipeds

  Include sucking lice belonging to genera Antarctophthirus, Echinophthirius and Lepidophthirus, and nasal mite and lung mites Halarachne and Orthohalarachne
• The seal louse, Echinophthirius horridus, transmits the heartworm, Acanthocheilonema spirocauda
• Arthropod Parasites of Pinnipeds

  • Nasal mites and lung mites cause sneezing, nasal discharge, secondary infection and emphysema
• Arthropod Parasites of Cetaceans


  Whale lice, which are actually crustaceans belonging family Cyamidae, are the most common
• Arthropod Parasites of Cetaceans


  • Whale lice feed on epidermal tissue, body fluids, and algal filaments
  • Infestation is not associated with any clinical manifestation

  
• Protozoan Parasites of Fishes

  • Ciliates- ectoparasitic. Examples: Ichthyophthirius multifiliis, Cryptocaryon irritans, trichodinids (Trichodina spp., Trichodinella spp., and Tripartiella), Brooklynella spp., and Chilodenella spp.
  • Flagellates- occur on the skin, gills, intestines, organs, or blood. Examples: Amyloodinium ocellatum, Ichthyobodo spp., Hexamita spp., Spironucleus spp., Trypanosoma spp., and Cryptobia spp.
  • Sprozoans- coccidia
  • Myxosporidians

  
• Ichthyophthirius multifiliis


  Cause of ichthyophthiriasis (Ich) or white spot disease of fresh water fishes
• Ichthyophthirius multifiliis


  • Lesions appear as whitish or grayish spots on the skin and gills. Ulcers in the skin may develop
  • Clinical signs include inappetence, lethargy, abnormal swimming behavior, darkened body, hemorrhages on the body surface, and opaque or hemorrhagic exopthalmic eyes
  • In heavy infection, respiratory distress and high mucus production may be also observed
• Life cycle of Ichthyophthirius multifiliis

  infective stage
• Cryptocaryon irritans


  White spot disease in marine fishes
• Cryptocaryon irritans


  • Lesions are similar as in ich
  • In microscopic examination of mucus (spots), round or oval ciliated parasites can be observed. I. multifiliis has a horseshoe-shaped macronucleus, while C. irritans has round to spherical macronucleus
• Trichodinids


  Include Trichodina spp., Trichodinella spp., and Tripartiellas spp.
• Trichodinids


  • Body is saucer-shaped with several rings of cilia on the periphery, and a sucker-like adhesive disc with hook-like denticles on the lower side
  • Attaches mainly on the body surface and gills. Excessive mucus production, frayed fins and pale gills can be observed
  • Heavily infested fish are weak and can be seen rubbing against objects. The spinning motion and adhesive disc of the parasite can damage the branchial epithelium, leading to problem in respiration
  • Transmission is through direct contact with infected fish, water, contaminated farm equipment and live feed
• Brooklynella hostilis


  Occurs in grouper, sea bass, and snapper, attached to the body surface and gills
• Brooklynella hostilis


  • Can be seen as bean-shaped ciliate in wet mounts of mucus
  • May affect fry and fingerling stages, in which it causes subcutaneous and respiratory problems
  • Affected fish rub body against objects, causing extensive damage and subcutaneous hemorrhage
• Chilodonella spp.


  Freshwater counterpart of Brooklynella
• Chilodonella spp.


  • In fresh biopsies, they are tear-shaped or oval, dorsoventrally flattened with parallel bands of cilia, moving in a characteristic slow spiral
  • Infested fish lose condition and copious mucus secretion may be observed in areas with severe infestation
  • Can cause swelling of gills and mucoid formation, resulting to respiratory distress such as rapid breathing and coughing

  
• Amyloodinium ocellatum


  A dinoflagellate causing "velvet", "rust", "gold dust" or "coral disease"
• Amyloodinium ocellatum


  • Infestation looks like white or brownish-gold patches, or dusty appearance, due to extensive mucus production
  • In larval fish, they are confined to the body surface only, while in bigger fish, the gills are also affected
  • Affected fish can be seen rubbing its body against objects and abnormal surface swimming characterized by spasmodic gasping and uncoordinated movements
  • Infested fishes crowd together at the water surface or near source of aeration
  • Diagnosis is by finding brownish or yellowish, pear or ovoid-shaped trophonts, attached singly or in clusters of 2-4 in gill filaments or skin scrapings

  
• Ichthyobodo


  One of the most common and smallest flagellated protozoan parasites that can be found in the skin, dorsal fin, and gills of freshwater or marine fish
• Ichthyobodo


  • Flattened, pear-shaped, with two unequal flagella. They move in a jerky, spiral pattern, and free-swimming organisms. Once attached, they can be difficult to see
  • Affected skin has a steel-gray color or gray-blue film due to copious mucoid production ("blue slime disease"). Brown coloration of the gills may be present as well

  
• Amyloodinium ocellatum


  • Affected fish can be seen rubbing its body against objects and abnormal surface swimming characterized by spasmodic gasping and uncoordinated movements
  • Infested fishes crowd together at the water surface or near source of aeration
  • Diagnosis is by finding brownish or yellowish, pear or ovoid-shaped trophonts, attached singly or in clusters of 2-4 in gill filaments or skin scrapings

  
• Ichthyobodo


  • One of the most common and smallest flagellated protozoan parasites that can be found in the skin, dorsal fin, and gills of freshwater or marine fish
  • Flattened, pear-shaped, with two unequal flagella. They move in a jerky, spiral pattern, and free-swimming organisms. Once attached, they can be difficult to see
  • Affected skin has a steel-gray color or gray-blue film due to copious mucoid production ("blue slime disease"). Brown coloration of the gills may be present as well

  
• Hexamita and Spironucleus


  • Most frequently found in the intestinal tract of finfish; cichlids are highly susceptible
  • Also causes "Hole in the head" disease or "head and lateral line erosion" (HLLE)
  • Pathogenecity is variable and correlates with the burden of infection. More than 15 organisms on wet mounts of intestinal tissue or contents necessitates treatment
  • Chronic infection can occur in fish maintained in crowded or unsanitary condition

  
• Trypanosoma and Cryptobia


  • Slender, elongated, actively motile biflagellates, that occur in the blood of snakehead, carp, mullet, and milkfish
  • Trypanosoma spp. have a well-developed undulating membrane, which may be transmitted by leeches, and associated with anemia
  • Cryptobia iubilans is associated with granulomatous disease in African cichlids and discus. Infected fish exhibit severe weight loss and cachexia
  • C. cyprini can cause "sleeping sickness" of goldfish
• Coccidia of Fishes


  • Common in freshwater and marine fishes
  • Aside from the intestines, other internal organs may be affected
  • Sporulated Eimeria-like oocysts, as well as other stages can be found in direct smears and histologic sections of internal organs
  • Include Eimeria, Goussia, Crystallospora, Calyptospora, and Cryptosporidium
  • Majority are of low pathogenecity. Damage depends on intensity of infection
• Myxosporeans


  • Microscopic, multicellular obligate parasites in organ cavities and tissues, composed of several spore shell valves
  • The infective stage is the spore, composed of spore shell valves, sporoplasms, and polar capsules
  • Common myxosporeans are Myxidium, Myxobolus, Henneguya, Kudoa, Myxosoma, Thelohanellus, and Sphaerospora, found in catfish, eel, carps, climbing perch, snakehead, grouper, sea bass, mullet and marine catfish
• Myxosporeans


  • In general, white cysts containing thick milky exudates are formed on skin, gills, muscle, brain, heart, ovaries, or other internal organs
  • Heavy infection on the gills can cause respiratory dysfunction
  • Cysts in the muscle may cause condemnation of the fish
  • Other effects include loss of equilibrium, skeletal deformities, and destruction of host tissue