Freshwater catfish are not only an ecological staple but also a valued food source in many parts of the world. Because of their economical and culinary significance, special attention is paid to diseases and afflictions that can affect their population.
Channel Catfish Virus Disease (CCVD)
CCVD is a particularly devastating catfish illness that can have a large economical impact for catfish farms. Caused by a herpes virus (Ictalurid herpesvirus 1), it can spread quickly and kill large quantities of junior catfish and fry. Infected fish will show prominent symptoms such as hemorrhaging fins, pop eye (exopthalamus) and swollen abdomens (ascites). Fish that do not die from CCVD remain covert carriers of the virus, which is not detectable through culture during the latent stage. Methods of control include housing incubating eggs and fry separate from carrier communities and the avoidance of stressful handling of juveniles during warm months.
Proliferative Gill Disease (PGD)
PGD is a serious condition that causes death through oxygen deprivation. The origins of this affliction remained a mystery for some time. However, the cause was eventually discovered to be a protozoan known as Aurantiactinomyxon ictaluri. The spores of this parasite are released into mud through the intestines of host worms. Once out of the host, these spores attach themselves to the gills of catfish. Disease can occur at all life stages and is characterized by swollen, blood-streaked gills. Infected fish cease feeding and move around lethargically, piping for oxygen until death occurs. There is no known cure for PGD; treatment methods include water aeration and the exchange of water with an unaffected pond.
Brown Blood Disease
During cooler months, an overabundance of ammonia can occur in ponds. This spurns a feeding frenzy among ammonia-eating bacteria, which produce a waste material called nitrite. At elevated levels, nitrite can infiltrate the gills of catfish, resulting in the oxidation of hemoglobin in red blood cells. The resulting compound, methemoglobin, cannot carry oxygen and can therefore induce suffocation. Infected catfish may have blood that ranges in color from reddish to deep brown, depending on saturation level. Brown blood disease is easily prevented by maintaining adequate chloride levels (at least 60 ppm during fall months) in the water supply. This can be done with the addition of salt (NaCl).
Caused by a bacteria known as Flexibactum columnaris, this disease can be particularly devastating to catfish farms in the southeastern United States. It is most prevalent during warm months when waters range from 77 to 90 degrees Farenheit. When the bacteria attach to gill surfaces, they spread rapidly, causing necrosis. Common symptoms include lesions on the skin and gills that are yellow-brown in color. Advanced lesions may have centralized ulcers. Acculumated growth of the columnaris bacteria can sometimes be found in the mouths of infected fish. Reduction of stress levels among the fish population is the most effective method of prevention. Treatment involves treating the water with chemicals deemed legally safe for food fish. Potassium permanganate is commonly used for water treatment.
Enteric Septicemia of Catfish (ESC)
Within the catfish farming industry, ESC tops the ranks of devastating population illnesses. Caused by the bacteria Edwardsiella ictaluri, this disease can affect all stages of catfish. Signs of infection include physical symptoms such as protruding eyes, red spots on the body, bloated abdomen and holes in the top of the head. When the disease progresses, infected fish will slow or cease feeding and swim in erratic patterns. ESC outbreaks can usually be treated with a two-week antibiotic feed regimen. However, the presence of ESC should be confirmed by a specialist before treatment.
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