Fish & Invertebrate Hematologic & Coagulopathic Disorders

Question 1

Describe the primary hemopathies of fish.

What are some of the common findings on the history of these fish?

What will you see on examination?

What are the blood flukes that can cause issues? What is their life cycle, where do they reside, how are they controlled?

What protozoa cause hemopathies? How are they transmitted? How are they controlled?

What viruses cause hemopathies?

What is white lip disease? What species is susceptible?

Answer 1

Problem 44 – Primary Hemopathies

• Prevalence: WF - 4, WM - 4, CF - 4, CM - 4
• Diagnosis:
  
  • Wet mount of blood or tissue with pathogen
  • Blood or tissue smear
  • Histopathology of tissue
• History:
  
  • Lethargy, weight loss, chronic mortality; leech infestation
  • Asymptomatic
• Physical Examination:
  
  • Anemia, cachexia, or incidental finding
• Treatment: Pathogen specific
• Pathogens of Concern
  
  • Blood Flukes – Digenean Trematodes – Sanguinicola & Cardicola
    
    • Similar life cycle to other digeneans
      
      • Fish act as the final host – blood flukes only need one intermediate host
      • Cercaria penetrate the fish and migrate to target organs
      • Some blood flukes use a polychaete as an IH (only digeneans without a mollusk in their life cycle)
    • Adults reside in blood vessels and release fertilized eggs which can cause thrombosis, lethargy, and gill irritation as they incite an inflammatory response
    • Eggs eventually make their way out
    • Diagnosis – eggs or miracidia in the gills
    • Treatment – control intermediate host, praziquantel might help
  • Trypanosomes – T. carassii, T. cobitis, T. murmanensis
    
    • Common in cold water species
    • Found in high concentrations in blood-filtering organs like the kidney
    • Can cause anemia, hematopoietic damage, and death
    • Transmitted by leeches
    • Trypomastigotes in fish blood may be small (acute infection) or large (chronic)
    • Controlling the leech population is the only known treatment
  • Trypanoplasms – Trypanoplasma borreli, T. salmositica, T. bullocki
    
    • Similar life cycle to trypanosomes – parasitemia after a leech infects the fish
    • Fish either dies or a nonsterile immunity (no parasitemia but the fish is still infected)
    • Causes anemia, exoplathamos, abdominal distension, splenomegaly, immunosuppression
    • Has amoeboid motility and two flagella
  • Apicomplexan Hemoparasites - Haemogregarines
    
    • Commonly encountered in wild fish
    • In cultured turbot can cause anemia, leucocytosis, and tumor-like granulomas
  • Viral Hemopathies
    
    • Viral Erythrocytic Necrosis Virus – Iridovirus
      
      • >20 species of anadramous fish
      • Anemia (pale gills)
      • Erythrocyte degeneration, hematopeietic response in kidney
      • Eosinophilic IC inclusions in erythrocytes
      • Reportable; marine reservoir suspected but not confirmed
    • Erythrocytic Inclusion Body Syndrome
      
      • Unclassified virus
      • Progressive severe anemia in chinook and coho salmon.
      • Transmitted via water or orally
    • Coho Anemia
    • Intraerythrocytic Viral Disease of Rainbow Trout
  • Nitrite Poisoning
  • No Blood Disease aka White Lip Disease
    
    • Channel Catfish
    • Hematocrits as low as 1%
    • Mottled skin, ascites, pale gills & viscera
    • Etiology unknown – dietary, viral causes are possible