Fish diseases are becoming rampant. The pet fish are becoming susceptible to diseases in confined environments. Aquarium fish are transported over long distances across national boundaries—even across continents.
As such pet fish are under stress due transportation and change in water quality. Many of the common freshwater fish are farm-bred. However most of the marine species are from natural collections and are prone to infections.
The ornamental fish get predisposed to infections in stressful situations such as dense population, poor water quality, loading of the aquatic environment with organic waste, sharp temperature fluctuation and oxygen depletion.
Ornamental fish trade is a global industry. In USA many common aquarium pets are farm-raised. Many of the exotic species are imported from Asia and Far East. Proper quarantine protocols are required to stop importing diseases.
Subjecting imported aquarium pets to 30 days quarantine prevents introduction of diseases to local established populations. Prophylactic use of antibiotics and medication can further help in preventing introduction of infections. Any outbreak of a new disease can devastate the pet fish trade of a region.
Fish health can be affected by environmental factors, nutritional deficiencies and bad management practices. Bacteria, fungi, parasites and virus are the common fish disease causing organisms. Cases of malignancy and tumors are also reported in these pets.
Common fish diseases due to nutritional deficiencies
Nutritional deficiencies of vitamins and minerals are associated with collapse of the vertebral column, impaired wound healing, impaired immunity, deformation of gill cartilage, poor growth, anemia, clubbed gills, loss of equilibrium, hyperpigmentation, edema, hemorrhage of the eyes, neurologic abnormalities, retinal atrophy, myopathy and muscular deformities.
Bacterial Diseases of Fish
Aeromonas species and Pseudomonas are common bacteria which affect freshwater sp. and cause hemorrhagic septicemia characterized by external reddening and hemorrhage in the viscera. Vibrio species are usually the cause of hemorrhagic septicemia in marine aquarium species.
Aeromonas salmonicida affects goldfish and koi causing abscesses and hemorrhages in fins, tail and internal organs. Furunculosis, vibriosis, yersiniosis, enteric septicemia and columnaris disease are some of the common bacterial infections.
Fungal aquarium fish diseases
Aquatic fungi are common in the aquatic environment. These fungi grow on decaying organic waste. When the water quality is poor, when the fish is injured or when it is under stress, the fungi invade the tissues and infect. Temperature control, sanitation, water exchange can bring down the incidences of these common fungal infections.
Saprolegnia infections are common and cause visible cotton-wool like growths on the body and fins. Aphanomyces invadans is found to cause deep ulcerative lesions in gouramis and barbs. Fusarium solani is found to affect marine angelfish and parrot fish causing ulcers on the head.
Viral fish Diseases
Carp pox, koi herpesvirus, channel catfish virus (CCV), hematopoietic necrosis, hemorrhagic septicemia, spring viremia of carp, lymphocystis, erythrocytic necrosis, epizootic erythropoietic necrosis, infectious pancreatic necrosis and largemouth bass virus are some of the common viral infections found in aquarium pets.
There is high mortality in juveniles and the surviving adults may become carriers of the virus. Several other common iridoviruses have been observed in these ornamental aquarium fish.
Common parasites in aquarium fish
Ichthyophthirius multifiliis are the common notorious ciliated protozoa causing “ich” or “white spot disease.” Cryptocaryon irritans causes white spot disease in marine species.
Amyloodinium species are parasitic dinoflagellates causing “velvet” or “gold-dust” in marine species. Sphaerospora auratus, a myxosporidian, causes renal dropsy of goldfish. Monogene helminths Gyrodactylus and Dactylogyrus are very common organisms affecting the gills and skin of goldfish, koi and many other ornamental aquarium species.
Lernaea sp. (anchor worms) are common parasitic copepods attached to the gills and skin feeding on tissues. Argulus sp. of copepods cause ulcers on the body, especially near the pectoral fins.
Tumors and malignancy in aquarium fish
Malignant tumors and neoplastic disorders have been observed in koi, angelfish, goldfish, swordtails and skates. If the pet can stand the stress, the malignant mass may be surgically removed.
Aquarium fish diseases caused by environmental factors
Chlorine, hydrogen sulfide and heavy metals are toxic to aquarium fish. Low dissolved oxygen in the water can cause distress.
Gas bubble disease occurs when the water is supersaturated with gases. Ammonia (NH3 is highly toxic to the aquarium pets. Water pH levels and salinity are also very important fish specific parameters to be monitored closely.
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