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Injecting Koi

There are many opinions regarding the use of antibiotics amongst the koi fraternity. There are even articles on this web-site warning against the use of antibiotics. Mostly the resistance among koi keepers refer to the indiscriminate use of antibiotics by mixing it with food or adding it directly to the water. A little knowledge about the stability of the ingredients in koi food and the rapid loss of effectiveness of antibiotics once opened is sufficient to question these methods. In the light of bacteria’s ability to “remember” and build some kind of resistance to the antibiotics that is frequently used, one tends to agree with those opposing antibiotics. The fact is that antibiotics are the only way to save a Koi once it has reached a certain stage of disease, and the only effective way to administer these drugs is through injection.

Much has been stated on how to inject Koi. Some experts feel that Intramuscular Injection (IM) is the best way, while others feel that Intraperitoneal Injection (IP, injections into the body cavity) is the preferred route of administration practiced around the world in aquaculture. There are also those who feel that they will never inject their koi. Injecting koi requires some skill and the responsibility remains that of the owner to ensure that it is done properly and correctly. The goals of this article are to assist the hobbyist and dealers on the differences between the location of the injection site and the proper technique for injecting koi. The specific injection site should be determined after consideration of various factors that will be discussed throughout this article.  

Dangers associated with injections
Despite the successes of antibiotic injections to combat bacterial disease, a small percentage of fish may not survive the procedure. This is mainly due to:

Averse reaction to the specific antibiotics.
When the fish struggles the sharp bevel of the needle may cause internal damage, especially when attempting an IP injection.

Even injections may not save a fish in advanced stages of disease.

Overdosing may damage kidney or liver function.

Slow release antibiotics may not combat the disease quickly enough.

Advantages associated with Injections

Guaranteed availability of the drug in the blood to combat disease.

Injections are affordable because of the relative low dosage.

There is no mass dosage that increases the possibility of wiping out beneficial bacteria or creating a resistant population of pathogens.

Injections are easy and quick

It is relatively safe.

Injections achieve higher levels of the drug in the blood faster than absorption through the intestines.

Intramuscular Injections
IM injections may be accomplished without anaesthesia and the uptake of the injected solution is equally efficacious with the IM injection compared to the IP route. If the injection is administered into the “red muscle” it will ensure even more rapid distribution throughout the fish. If the correct injection site is selected, no scales will be lost. Some injection sites will however brought about the loss of scales, as it will not always be possible to inject underneath a scale without piercing the underlying scales. There are also small non-contagious cysts that may appear at the injection site and it can also cause the loss of scales. One draw back of an IM injection is that after the needle has been withdrawn the muscle may contract and squeeze some of the injected antibiotics out the injection site. Determining factors when deciding on an injection site will be the whether the koi has a high economic and aesthetic value that may reduced when scales are lost the size of the fish and the type of antibiotic that will be used. Although it is stated that IM injections can be effected without anaesthetics, it is recommended that a fish be sedated to avoid injury to the fish and/or the health expert.

There are three main sites recommended for injection, although two of these may not be acceptable to the owner, for reasons stated above. 

Dorsal muscle

This injection site offers the opportunity for deep Intra Muscular injections. Slip the needle underneath a scale, aiming towards the nose of the fish and administer the injection. Keep some pressure on the injection site with a thumb for a few seconds to ensure better distribution of the antibiotics and to prevent it from being forced out by contracting muscles. Topical treatment can be applied to the injection site to prevent bacterial infection. Some scales may be lost because of the possibility of a non-contagious cyst that can develop, or a scale that has been pierced will be dislodged when the needle is extracted. This site is risky from an aesthetical point of view and is not recommended for valuable koi.

Caudal muscle

This injection site offers the opportunity for injection into the red muscle of the fish that will ensure rapid distribution of the antibiotics through the fish. The needle is also slipped underneath a scale. The procedure is similar to the injection into the dorsal muscle, and is also not recommended for valuable fish.

Base of the dorsal fin

The injection site is located at the rear of the dorsal fin, just behind the last fin ray. There are no scales at this site and offers an injection site without the immediate risk of scale losses. If a non-contagious cyst develops, scales may be lost. Insert the needle just behind and slightly to the side if the last fin ray, aiming towards the front of the fish at a 45-degree angle. Because this is also an IM injection, apply a little pressure to the injection site when the needle is withdrawn.

Pectoral muscle

An injection into the pectoral muscle is the best injection site for an IM injection, mainly because any cysts will be hidden from view and there are no scales. As with all injection sites, this one is also not without risk. Some medications are harsh on muscle tissue and the muscle of a fish may harden, rendering the fin immobile, especially in smaller fish. It however remains the IM injection of choice if the visual damage must remain as little as possible. The accompanying photo demonstrates how the pectoral fin is lifted away from the body exposing the muscle. The injection is administered and the injection site lightly massaged to ensure even distribution of the antibiotic. Topical treatment can also be applied to the injection site to prevent bacterial infection.

Intraperitoneal Injections

Those involved in aquaculture all over the world practice intraperitoneal injections. This method entails injecting antibiotics into the abdominal cavity. The needle is inserted between the body wall and the intestines and then the injection is administered. In inexperienced hands, this type if injection can cause serious damage to internal organs. It may also be injected into the intestines where it will be passed through the vent, or it may be deposited into the egg sac, rendering the injectable useless. It is preferable to hold the fish upside down when administering an IP injection. Normally the scales are fairly small on the belly of a koi and it will not always be possible to insert the needle between the scales. It is therefore best to accept that scales will be lost, but no damage will be done to the aesthetics of the fish. 

Intravenous Injections
Some antibiotics are developed for injection directly into the bloodstream, because it loses it's effectiveness quickly. This can be achieved through an intravenous injection to the base of the caudal fin. The main problem that one experience with this specific injection is the ability to penetrate the vein that runs through the centre of the fish. The best way to determine when the needle is placed correctly is to turn the fish upside down and then to insert the needle at the base of the caudal fin. If you draw the plunger back a little, blood should be entering the syringe. When this happens, the plunger can be depressed and the antibiotic will be deposited into the bloodstream. This should not be attempted unless it is absolutely necessary.


Last Updated on Wednesday, 29 February 2012 12:50