Catfish Disease Treatments
Before treating any fish, consider the following questions and decide whether or not treatment is warranted:
- What is the prognosis? Is the disease treatable, and what is the possibility of a successful treatment?
- Is it feasible to treat the fish where they are, considering the cost, handling, prognosis, etc.
- Is it worthwhile to treat, or will the cost of treating exceed the value of the fish?
- Can the fish withstand the treatment considering their condition?
- Does the loss rate and the disease present warrant treatment?
Before any treatment is started, know the following four factors:
· Know your water. Know the volume of water of the holding or rearing unit to be treated before you apply any treatment.
· Know your fish. Fish of different species and ages will react differently to the same drug or chemical.
· Know your chemical. Know the toxicity of the chemical to the particular species of fish to be treated. The effect of water chemistry on the toxicity of the chemical should also be known.
· Know the disease. Although this factor appears to be self-evident, it is one which is widely disregarded, much to the regret of many fish farmers.
Methods of Treatment
Various methods of treatment and drug application have been used to control fish diseases.
· Dip. A strong solution of a chemical is used for a relatively short time. This method can be dangerous because the solutions used are concentrated. The difference between an effective dose and a killing one is usually very slight.
Fish are usually placed in a net and dipped into a strong solution of the chemical for a short time, usually 15 to 45 seconds, depending on the type of chemical, the concentration, and the species of fish being treated.
· Flush. This method is fairly simple and consists of adding a stock solution of a chemical to the upper end of the unit to be treated, then allowing it to flush through the unit.
An adequate water flow must be available so the chemical can be flushed through the unit or system in a short period of time. This method cannot be used in ponds.
· Prolonged. There are two types of prolonged treatments: a short term, or bath, and an indefinite prolonged treatment.
Bath – the required amount of chemical or drug is added directly to the rearing or holding unit and left for a specified time, usually one hour. The chemical or drug is then quickly flushed with fresh water. Several precautions must be observed with this treatment to prevent serious losses. Although a treatment time of one hour may be recommended, always observe the fish during the treatment period.
At the first sign of distress add fresh water quickly. Install aerators of some type in the unit being treated to insure an adequate oxygen supply for the fish. Use extreme caution to insure that the chemical is evenly distributed throughout the unit to prevent the occurrence of a “hot spot” of the chemical. Adjust the temperature of the water to prevent temperature shock when water is changed.
Indefinite – usually this method is used for treating ponds or hauling tanks. Apply a low concentration of a chemical and allow it to dissipate naturally. This is generally one of the safest methods of treatment.
One major drawback, however, is the large quantities of chemicals required which can be so expensive it can be prohibitive. As in the bath treatment, it is necessary to distribute the chemical evenly throughout the unit being treated to prevent the occurrence of “hot spots.”
· Feeding. In the treatment of some diseases the drug or medication must be fed or in some way introduced into the stomach of the sick fish. This can be done by either incorporating the medication in the food or by weighing out the correct amount of drug, putting it in a gelatin capsule, and then using a balling gun to insert it into the fish’s stomach.
This type of treatment is based on body weight; thus standard units of treatment are given in grams of active drug per 100 pounds of fish per day, in milligrams of active drug per pound of body weight, or in milligrams of active drug per kilogram of body weight.
· Injections. Large and valuable fish, particularly when only small numbers are involved, can at times be treated best by injecting the medication into the body cavity (intraperitoneal or IP) or in the muscle tissue (intramuscular or IM). Most drugs work more rapidly when injected IP than IM. When injecting, particularly IP, use caution to insure that no internal organs are damaged.
The easiest location for IP injections is the base of one of the pelvic fins. Partially lift the pelvic fin and place the needle at its base and insert until the tip of the needle penetrates the body wall. The needle and syringe should be on a line parallel to the long axis of the body and at about a 45 degree angle downward. You can tell when the body wall has been penetrated by the sudden lack of pressure encountered when inserting the needle. As soon as the tip of the needle is in the body cavity, the required amount of medication is rapidly injected and the needle then withdrawn.
For IM injections the best location is usually the area immediately next to the dorsal fin. Hold the syringe and needle on a line parallel to the long axis of the body and at about a 45 degree angle downward. Insert the needle to a depth of about ¼ to ½ inch and slowly inject the medication directly into the muscle tissue of the back. Inject the medication slowly; otherwise, back pressure will force the medication out of the muscle along the wound channel created by the needle.
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