Abstract

This slide presentation is designed to give the audience a brief panorama on the subject of fish medicine. Representative cases of the more prevalent diseases of marine and freshwater tropical fishes will be projected. Of the infectious diseases afflicting exotic fishes, the following six categories will be discussed: 1. Bacterial, 2. Viral, 3. Fungal, 4. Protozoan, 5. Helminthic, and 6. Crustacean. Of the noninfectious or environmental diseases, cases will be projected that depict anoxia, nitrite toxicity, malnutrition, gas-bubble disease and a few examples of poisoning such as cyanide toxicity and ichthyoacanthotoxism. Some basic therapeutic concepts will be mentioned and the importance of ante- and postmortem diagnostic procedures will be emphasized.

Notes

Mark Dulin is available to aid fish farmers and has the facilities to test fish vaccines.

The USA gets 50% of the world tropical fish industry which amounts to about 3 billion dollars. It is comprised mostly of freshwater fish.

Infectious Diseases

Bacterial – Acute

• Bloat - ascites or gas in peritoneal cavity.

• Do a paracentesis, check for bacteria and treat intraperitoneally if peritonitis exists.

• Dermatitis

  • vibriosis occurs mainly in marine fish.

  • use furanase on freshwater fish.

  • ulcers provide a portal of entry for bacteria and allow fluid loss. Treat these with furanase, then cover with superglue to prevent fluid loss.

• Gills - Plexibacterium columnaris

• Chronic: Mycobacteriosis is zoonotic, causing tuberculosis in humans. Dr. Wolke in Rhode Island has a paper entitled "Piscine Mycobacteriosis" which describes the disease. Diagnosis is by demonstrating acid fast organisms on a smear. Histopathology shows the presence of granulomas.

• Viral - Lymphocystis.

• Fungal - do wet mounts, smears and histopathology. Eye problems are often fungal.

• Protozoan

  • Ichthyophthirius - do wet mount.

  • Oodinium - a freshwater bath will rupture them.

  • Orchlid "hole in the head" - Treat with Flagyl.

• Crustaceans - go for the gills.

Non-Infectious Diseases

• Overloading an aquarium with fish causes nitrite toxicity.

• Stress predisposes fish to disease. The presence of aggressive fish in a tank can cause stress.

• Some fish secrete toxins. The Box fish causes ichthyoacanthotoxism, for example.

• Anoxia is demonstrated by a flared operculum and gaping mouth.

• Malnutrition - obesity is seen as excess fat in the mesentery. When fish stop eating, their gall bladder enlarges. Fish can be tube-fed if they stop eating, however the effectiveness of this is unknown. Marine fish typically have a fatty liver.

• Vitamin C deficiency causes broken spinal columns. Grey flesh can be seen grossly in the region of the break on postmortem.

Diagnosis

• To test for a pathogen, take part of diseased fish and put it into water. Soak live fish in the water and see if they contract the disease.

• Inflammatory cells can be seen on blood smears.

• Gram stain of tissue imprints indicates bacterial infection.

Treatment