Common fish diseases and their cure: how to detect fish diseases before it hits you hard.

antibiotics and antibacterial drugs are important in a fish farm

On our journey to achieving success in our fish farm, we find that sometimes farmers record huge loses as a result of disease outbreak in fish farms.

Fish farming, like all other animal husbandry face challenges caused by various diseases causing parasites and bacteria. While it is hard to remedy such outbreak, the best practice in aquaculture is to prevent diseases before they occur. In other words, prevention is better than cure.

Many factors can affect the health of a fish and these factors varies, One thing that all fish farmers alike must all know and come to understand, is that fishes in the water never live apart from bacteria and parasites, infact they all live together in the same environment. Some bacteria in aquaculture are labeled opportunistic; and this is because under normal circumstances, these bacterial live in the same environment as the fishes and interact with them without any harm to the fish.

Turn that the situation around, and let the water quality or oxygen level drop; or there be a shift in the pH or temperature of the fishpond to dangerous levels; then that same parasite or bacterial that once lived peacefully with the fish will become so dangerous as to cause a deadly infectious outbreak that has the potential to cause a major fish kill. 

During the cause of my research on catfish diseases, I have come to understand that; It is a fallacy to believe that there is such a thing as 100% parasite and bacterial free water. When we look at water with face value, what we see is a colorless and clear liquid and in our minds we believe that such water is clean and germ free. Don't we? 

Fast-forward and put that same water under a microscope and test it, what do we see? We see microscopic organisms that move about in the water. Such microorganism our eyes don't see are always present in the water and have naturally lived with the fishes from time, and the same goes for some parasitic and bacterial causing organism that live in water.

marine ecosystem

When we talk about fish diseases, it is best we have a proper understanding of the dynamic nature of the marine ecosystem. Many factors come to play when we talk about the aquatic habitat, such factors like pH; temperature; oxygen level, hardness; and stocking density all play a key role in freshwater aquaculture systems.

All things being equal, when all this factors mentioned earlier are balanced together, the fish will live peacefully with all these parasites and bacterial, without any harm being done to the fish, but when one of these parameters like pH, oxygen level, or temperature is changed or altered to low levels that cause the fish to stress. At that point; bacteria and parasits will take advantage of the fish, attack it and break down its immune systems, and ultimately causing it to become ill.

fish have a well built immune system that shields off bacterial and parasites infections

Under normal circumstances, fish have a well-built immune system that naturally fights against these bacterial and parasitic organisms, but when the water environment becomes polluted and unconducive for the fish, any infection becomes fatal and can cause death to the fish if left unresolved.

Before I started to talk about catfish diseases, I wanted to lay down a foundation, and then build on it, that was why I started my introduction, talking about the aquatic habitat; and my point of view was that; normally fish live in the same environment as these parasites and have a strong immune system that fights off diseases naturally.

The aquatic habitat is a complex habitat to sturdy, but much advancement has been made in the area of aquaculture. Some of these researches have shown that, stress is the main reason behind many infectious disease outbreak in freshwater ponds, and not really the parasitic organism causing such outbreak themselves.

Why would I say a thing like that?

when the environmental conditions are good the fish is happy.

Well lets look at it this way; when a fish lives in water that has good pH (6.5 to 8) and an ambient temperature; that is well oxygenated, and free of harmful chemicals like ammonia and hydrogen sulfide; you find that the fish will have a good apatite and respond well to feeding. It will convert the food you give it, to nutrients and use them for growth and for defense against disease, but alter any of the parameters like pH, temperature or even the oxygen content on the water and reverse is the case.

Now to the topic of the day, what are the disease that fish farmers should be aware off? And how can a fish farmer get sufficient knowledge, to be better fortified in the case of an outbreak? 

Let's find out.

fish infections are caused by different microscopic organism too small to be seen my the naked eye

Fish disease and infection are caused by different kinds of parasites and microscopic organisms that cause varying degrees of harm to the health of freshwater fish including, and not restricted to catfishes. The diseases these microorganism causes are categorized as:

1. Bacteria infections.

2. Viral diseases.

3. Fungal infections.

4. Parasitic infections.

Bacterial infections:

Some common bacteria infection that occur in freshwater ponds are listed in the table below.

Bacterial Disese	Symptoms	Treatment
Enteric Septicemia of Catfish (ESC)	lethargic swimming, abnormal behavior, alternating/restlessness and chaotic swimming, disorientation, and swimming in spirals. Loss of appetite is observed in infected fishes, also the fish are observed to be protruding the head from the water.	antibiotics such as: Terramycin (oxytetracycline), Romet (sulfadimethoxine-ormetoprim) or Aquaflor (florfenicol) are mixed with the fish feeds and given to the fish.
Fin and tail rot	Fins starts rot and corode	I min dip in 1:3000 solution of copper sulphate will cure the diseases. Painting the infected parts also helps with quick recovery.
Ulcers	Sores and injury seen on body of fish	The badly infected fish should be destroyed and the pond water disinfected with 0.5 ppm solution of KMnO4. Dip treatment for one minute in 1:2,000 copper sulphate solution for 3 to 4 days in case of fish showing early stage of infection is required. Addition of chloromycetin at 5 to 10 ppm to pond water and/or addition of the antibiotic oxytetracycyline to feed @ 75 mg/kg of fish/day should also be done.
Dropsy	Some part of fish body will be swollon	disinfection should be done with 1 ppm potassium permanganate solution or dip treatment in 5 ppm of the same chemical for 2 minutes.

1. Hole in the head or Enteric Septicemia of Catfish (ESC): this diseases is caused by a gram nega- tive bacterium called Edwardsiella ictaluri, and it is one of the most important diseases that is prevalent in many catfish farms. Some symptoms are detected by observing the behavior and swimming parttarn of the fish. Some signs can be lethargic swimming, abnormal behavior, alternating/restlessness and chaotic swimming, disorientation, and swimming in spirals. Loss of appetite is observed in infected fishes, also the fish are observed to be protruding the head from the water. This bacterial infection is transmitted by Horizontal transmission via the faecaloral route, cannibalism of dead and diseased fish, and contact with contaminated water and materials used in handling infected fish are known to spread the disease.

2. Fin and tail rot diseases; this kind of dieses affects both adults and young fishes. One of the first signs or symptoms of this infection is a whitish line on the margin of the fin. This sign is noticed at the onset of the infection and if left on treated, it spreads and as it spreads, it start to impart a frayed appearance to the appendage of the catfish, and it eventually disintegrates and petrifies the fin. This very disease is contagious and has the potential to cause a considerable damage or loss to your fish stock.

3. Ulcer disease (Columnaris disease)- This types of bacterial disease is caused by a bacterium called Flexibactor columnaris. The symptoms of this bacterial infection is that, the fish begin to show a raised white plaque, and often with a reddish peripheral zone on the fish body. This diese can lead to hemorrhagic ulcers in the fish stock.

4. Dropsy dieses:- this diese causes the skin of the fish to swell, and this swelling is because the fish is absorbing more water than it can eliminate via excretion. It can be caused by a bacterial and parasites. High nitrates level in water and liver dysfunction has been reported also to cause this infection in freshwater fishes. In scally fish I.e. tilapia, it causes scale protrusion and exophthalmic condition or bulging of the eyes. This type of diese leads to inflammation of intestine and ulcers on skin and fin of the catfish.

5. Ulcers: Ulcers are an open sore on the body of a fish. In catfish, ulcers can be external or internal, and can cause a break in the skin or mucous membrane which will not heal readly. Ulcers are commonly caused by injury to the skin of the fish, and this injury can sometimes be inflicted by a parasite, bacterial, or exposure to high levels of chemicals such as ammonia

See table below for different bacterial infections and their treatment methods:

Viral diseases:

One of most important viral diseases that affect catfish is the fish pox virus or CCVD: this virus is caused by the herpesvirus. This virus is common in heavily stocked catfish pond but it is more likely to be found in catfish fingerling ponds. Older catfish are affected by this virus but fatal outbreaks almost exclusively occur in catfish fingerlings ponds.

Fungal diseases:

Some fungal diseases encounted in freshwater fish farm are:

Fungal disease	Symptoms		Treatment
Saprolegniasis		a whitish fur-like growth is seen on the fish and is also observed in the water	Once a farmer observes or confirms the presence of saprolegniais, sanitation operations should be evaluated and corrected. Common treatments include potassium permanganate: KmNO4(1g in 100L of water for 30-90min), formalin, povidone iodine and bath treatment in sodium hydrooxide solutions ( NaOH 10-25 g/Lfor 10-20min ). Over treatment can further damage fish tissue, resulting in recurring infections. Environmental management is essential for satisfactory resolution of chronic problems.
Branchiomycosis		The gills starts to rot	Avoidance is the best control for branchiomycosis. Good management practices will create environmental conditions unacceptable for growth of fungi. If the disease is present, do not transport the infected fish. Great care must be taken to prevent movement of the disease to non-infected areas. Formalin and copper sulphate have been used to help stop mortalities; however, all tanks, raceways and aquaria must be disinfected and dried
Egg fungus		A whitish cotton like substance starts to gow on dead eggs	Hydrogen perooxide and formaline.
ichthyophonus			No treatment, prevention is better than cure

The three most common fungal diseases encountered in fish farm are saprolegniasis, branchiomycosis and ichthyophonus.

1. Saprolegniasis- one of the most common symptoms of this fungal disease is that a whitish fur-like growth is seen on the fish and is also observed in the water.

2. Branchiomycosis (Gill Rot)- It is caused by the fungi, Branchiomyces sanguinis (in carps) and Branchiomyces demigrans (in pike and tench). Branchiomycosis is a pervasive problem in Europe, but has been only occasionally reported by US fish farms.

3. Egg Fungus: this fungal infection is caused by the Saprolegnia spp and it attaches itself to fish eggs and kills them before they hatch. This is one of the fungals that is of importance to fish hatcheries. The most common treatment is with hydrogen peroxide or formalin.

Parasitic infections:

Parasite	Signs and symptoms	Treatment
Ichthyopthirus multifiliis	Mostly seen on the skin of fish. ICH infection is commonly visible as one or several characteristic white spots on the body or fins of fishes. The white spots are single cells which are called trophonts. These cells feed on their hosts cells (epidermal cells)	dip for hourly duration, in 1:5,000 formalin solution for 7 to 10 days, or in 2% common salt solution for more than 7 days, or in 1:50,000 quinine solution for 3 to 10 days should be used.
Diphyllobothrium dendriticum	This parasite can be on the body of the fish or it can be internal	chelated copper compounds
Diphyllobothriumlatum	This parasites can be on the body of the fish or it can be internal	chelated copper compounds
Trichodina sp	Superficial white lesions may appear on the body of the fish and the fins may become frayed.	In trichodiniasis 1 hour bath in 1 ppm malachite green solutions for 3 days should stop this parasite. chelated copper compounds, which are extremely effective against protozoan parasite, have been used over time.

Conclusion:

In conclusion, prevention is always the best way to go in aquaculture, this is because sometimes treatments to control the diseses in the event of an outbreak sometimes is not so effective. For treatments that have to be administered orally; loss of appitite affects the rate and efficacy of drugs because the is taking in less and less food.

Other bath treatments with chemicals such a sodium permanganate or formaline should be administered with care and the fish should be put under observation during and after the treatment baths.

To aviod many problems in your fish farm, it is best to always maintain a safe stocking density, this way you will avoid many disease in your fish farm.

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