Saturday, March 13, 2021

  • March 13, 2021
  • Nigerian Catfish Farmers

 



Dropsy refers to a condition in which fish often have hugely swollen bellies, and the continuing use of the term probably has to do with how it so accurately depicts the visual symptom: the belly drops down. Sometimes the condition is also known as bloat. 


Any fish may be exposed to the dropsy-causing bacteria, but healthy fish rarely fall prey to the disease. Fish are only susceptible when their immune system has been compromised by some other stress factor. If all the fish in the tank are under stress, it’s quite common for the entire tank to become infected, but it is also possible for only one or two fish to fall ill, especially when prompt action is taken to prevent the spread of the bacteria.


As the infection progresses, skin lesions may appear, the belly fills with fluids and becomes swollen, internal organs are damaged, and ultimately the fish will die. Even with prompt treatment, the mortality rate is high. Successful treatment is very unlikely unless a fish is diagnosed in the early stages of the infection.


Symptoms of the underlying bacterial infection can vary widely. Some fish will have the classic swollen belly, others display skin lesions, while still others show few symptoms at all. This variability is what makes diagnosis difficult. In most cases, a number of symptoms are observed, both physical and behavioral.


Symptoms

  • Grossly swollen belly
  • Scales that stand out with a pinecone-like appearance
  • Eyes that bulge
  • Gills that are pale
  • The anus that becomes red and swollen
  • Feces that are pale and stringy
  • Ulcers on the body, along the lateral line
  • A spine that is curved
  • Fins clamped together
  • Redness of the skin or fins
  • General lethargy
  • Refusal to eat
  • Swimming near the surface

The agent that causes the symptoms of dropsy is usually the very common Aeromonas bacteria, one of several gram-negative bacteria present in most aquarium habitats. The bacteria are known as gram-negative because they do not take on a specific stain used in the Gram Stain method of identifying bacteria species.


The bacteria will only lead to serious infection in a fish that already has a compromised immune system. This can happen as the result of stress from a number of factors, such as:

  • Poor water quality
  • Ammonia or nitrite spikes
  • A large drop in water temperature
  • Stress from transportation
  • Improper nutrition
  • Aggressive tankmates
  • Other diseases

Generally, a single or short-term exposure to stress will not compromise the ability of the fish to fight infection. In most cases, the stress exposure must be present for an extended period of time, or several stress factors must occur in rapid succession, in order to affect the fish's immune system. 


  • Move the sick fish to a "separate tank."
  • Add 1 teaspoon of salt per gallon of water in the tank
  • Feed the fish fresh, high-quality foods.
  • Treat the fish with antibiotics, either in the food or in the water.
  • Test the water ph in the tank daily to ensure it is appropriate for the fish.

It is important to move any infected fish to another tank to separate them from the remaining healthy fish. While the affected fish are quarantined, perform a water change on the original tank and monitor the remaining fish closely for the appearance of symptoms.

Salt should be added to the hospital tank, again at the ratio of 1 teaspoon per gallon of water. Low levels of salt in the water aid in the osmotic balance of the fish by making the water salinity closer to the fish's blood salinity. That helps the fish get rid of excess water accumulating in the body, causing the dropsy. But, don't add too much salt as that can be unhealthy for freshwater fish. Keep the hospital tank scrupulously clean, and perform weekly partial water changes, adding salt to the new water being added to the aquarium.

Provide the ill fish with a variety of fresh, high-quality food. Often this is enough to resolve the infection in cases that are not too far advanced, if the fish is still eating. Keep the fish under observation for several weeks after the symptoms disappear.

Antibiotics should be used if the fish does not immediately respond. A broad-spectrum antibiotic specifically formulated for gram-negative bacteria is recommended, such as Maracyn-Two. A 10-day course is ideal for ensuring the infection is eradicated, but you should always follow the manufacturer's directions for duration and dosage.


How to Prevent Dropsy

As with many diseases, prevention is the best cure. Almost all the factors that stress fish enough to make them susceptible to infection can be prevented. Because poor water quality is the most common root cause of stress, tank maintenance is critical. Factors to keep in mind include:

  • Test the  water PH regularly to ensure it is healthy for your fish.
  • Perform regular water changes.
  • Keep the tank clean.
  • Clean the filter regularly.
  • Use a gravel vacuum to remove wastes from the bottom of the tank.
  • Avoid overcrowding the tank.
  • Do not overfeed fish.
  • Vary your fish's diet
    .

If the tank is well maintained and the fish are fed a healthy diet, outbreaks of infections causing dropsy are unlikely.


  • March 13, 2021
  • Nigerian Catfish Farmers

Aquaculture accompanies several disease problems caused by different microbial pathogens which are common evident in general culture practice. High stocking densities, over feeding and other organic loads stimulate the proliferation of pathogenic microorganisms. Bacteria, virus, fungus and protozoan parasites are the important microorganisms to cause diseases in fish culture. Disease outbreaks continue to be a major problem for the sustainable development of the aquaculture industry. Clinical outbreaks can negatively impact on the welfare of the fish and the economic gain.


The non pathogenic diseases in fishes is due to environmental factors, nutritional deficiency, degrade of pond conditions etc. The following are the important non pathogenic diseases of the which affect severely to catfishes….

 

  • Crack Head / Head Crack /Broken head disease / Broken skull disease
  • Yellow Liver (Jaundice) disease / Yellow Liver disease / Swollen liver disease
  • Brown Blood diseases


Crack Head Disease in Cat Fish.


The “Crack Head” disease is the only obvious catfish disease reported from pond culture .It is also called the Broken Head Disease / Broken Skull Disease. It is a highly devastating disease in commercial catfish farming in India.

 

Causes.


Crack Head disease is due to one or more of nutritional deficiencies like Vitamin C, Vitamin D, calcium, and phosphorus .Crack Head disease believe to be caused by a poor diet or lack of unbalanced nutrients, poor water quality and over feeding etc .

 

Symptoms.


Begins as small pits on the head region, usually just above the eyes. The affected fish shows a reddishness lateral line on the skull, between the two air chambers, parallel to the skull plate joints . In later stage, these turn into large cavities in which the disease is progresses along the lateral line. Skull will break ultimately fish will die.

 

The clinical symptoms are slightly distended abdomen due haemorrhages , occasionally exophthalmus (pop-eyes), reduced growth, scoliosis, lordosis, haemorrhages, lesion on fin distorted gill filaments, fin erosion, abnormal pigmentation, increased capillary fragility, poor reproductive performance and spinal deformity.

 

Recently, it has been noticed that the Crack Head disease is reported as Vitamin C deficiency syndrome in intensive catfish culture. The dearth importance of vitamin C as an immune modulator and a key nutritional element for catfish.

 

 

Possible Treatments.

 

  • Increase frequent water changes.
  • Add vitamins supplements enriched with Vitamin C in the feed.
  • Remove sludge from the pond bottom.
  • Maintain optimum DO, pH and minimizes ammonia level in pond water.
  • Supply balanced diet regularly.

 

 

Brown Blood Disease.

 

Nitrite poisoning commonly called "Brown Blood" Disease, is an environmental  disease that affect a number of fish species including channel catfish. The main cause is elevated levels of nitrite in the pond water. The disease occurs in fish when the water contains high nitrite concentrations. Nitrite is a product of the breakdown of ammonia by bacteria. Nitrite enters pond eco system after feed is digested by fish and the excess nitrogen is converted into ammonia, which is then excreted as waste into the water. Uneaten (wasted) feed and other organic material also break down into ammonia, nitrite, and nitrate in a similar manner.

 

Nitrite enters the bloodstream through the gills and turns the blood to a chocolate-brown color. Hemoglobin transports oxygen in the blood and combines with nitrite to form methemoglobin which is incapable of transport oxygen. Brown blood cannot carry sufficient amounts of oxygen and affected fish can suffocate despite adequate oxygen concentration in the water. This accounts for the gasping behavior often observed in fish with brown blood disease, even when oxygen levels are relatively high.The term "brown blood disease" comes from the appearance of the blood that has high levels of methemoglobin .


Brown blood disease can be prevented, or at least minimized, by close monitoring of nitrite, chloride, and TAN, and by maintaining the proper chloride to nitrite ratio. If brown blood disease does occur, the condition can be reversed by adding salt to the water. Catfish (likely other fish) surviving brown blood disease or nitrite stress are more susceptible to bacterial infections, anemia (white-lip or no-blood), and other stress-related diseases. The secondary problems such as Aeromonas or Columnaris infections, often occur in 1 to 3 weeks after brown blood disease.

 

 

Sodium chloride (common salt) is used to treat brown blood disease. Calcium chloride also can be used but typically more expensive. The chloride portion of salt competes with nitrite for absorption through the gills.

 

Jaundice Disease in Catfish.

 

Jaundice is a condition of yellow colouration in the abdominal skin, sclera of the eyes and fin bases. It is a significant health problem affecting the most of freshwater catfishes. Jaundice is due to an excess of bile pigment present in the blood and lymph. This condition described in catfish as "Catfish Jaundice".The affected fishes are suffering from a haemolytic anaemia resulting in jaundice. Although, a single pathogen could not be associated with this condition, a wide range of microbial pathogens are involved .

 

These may contribute towards the morbidity and mortality is observed in jaundiced fish. Myxosporean infection is found in both apparently normal fish and jaundiced fish. In affected fish gills becomes pale, yellow ascitic fluid, enlarged spleen, kidney and gall bladder, and/or yellow flesh.

 

The clinical symptoms are:

 

  • Affected fish shows yellow colour of the skin and gills.
  • Reduced appetite and became lethargic, anorexic and moribund
  • Fish show gill rot & increases mortality rates
  • The spleen, kidney, gall bladder and liver become enlarged with pale-yellow in colour.
  • The fat tissue in the abdominal cavity also yellow in colour.
  • Serum of jaundiced fish is bright yellow to orange in colour

 

 

Fish has lose movement due todamage of caudal fin. Disease occurs due to poor water quality, high stocking density , disease occours conveniently at temperature 30oC. However, disease also occurs when temperature fluctuates unusually. E. Italis, that causes pus-in-liver disease in Catfish.

 

 

Jaundice disease is very dangerous and difficult to treatment. In severe condition , it may lead mass mortality of fish in early growing stages . Jaundiced fish has prone more susceptible to stress and tended to die before reach to the market size .

 

 

Rancid fats in the diet result in high levels of free radicals and peroxides that cause oxidative damage to biological membranes and organelles. Polyunsaturated fatty acids (PUFAs) are essential components of all biomembranes. Vitamin E is an important antioxidant and protects biological membranes from lipid peroxidation by acting as a scavenger of free radicals. The presence of rancid fats however depletes the diet of vitamin E and other antioxidants, leaving the biological membranes vulnerable to oxidation. The improved and quality of the feed is recommended for this condition.

 

 

Preventive measures for diseases in fish culture farms.


The health management of fish is enforcement of stringent biosecurity measures that prevent the entry of pathogens into the culture system. Other important components of fish health management include minimization of stressful events and use of compounds that boost or stimulate the fish immune system. Following are the key recommendations for effective health management…Proper pond Preparation , stocking of quality seed and disease free fish fry ,maintaining of water quality ,high nutritional feed etc are essential to reduce risks of fish disease outbreaks. Regular use of probiotic and immunostimulants has the greater impact on fish farming and minimizes the risk factors for disease out breaks. Environmental management to minimize stress also plays a major role in disease prevention.


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