Symptoms and Treatment of Costia – Ichthyobodo necatrix

The significance of Costia

Life was simple for a fish vet in the early nineties. Japanese fish were too expensive for the average hobbyist and their beautiful wiles had not been fully discovered. The usual pond-call involved a poor filtration system, high ammonia levels, a sagging pH and a case of “garden variety” Trichodina on some hardy domestic fish.

One would simply recommend a treatment of salt coupled with an upgrade to the filtration type and flow. A week later, all the fish are recovered. Doctor Johnson is a hero.

Now, partly because my exposure is more widespread and Japanese fish are so much more prevalent, the fish veterinarian sees much more challenging things.

Salt resistance has arisen in the following parasites:

Flukes – 20% of cases are completely resistant to salt treatments at any level. Most cases are cleared at zero-point-nine-percent but less than thirty percent still clear off at the old zero-point- three-percent standby level.

Trichodina – 20% of Trichodina cases do not clear at even zero-point-six-percent. There are rare cases where trichodina does not clear even at zero-point-nine-percent which is also stressful to the fish. Formalin or potassium permanganate are recommended.

Chilodonella and Ich have never been recorded as being salt resistant in the least bit.

Costia has shown some resistance and it is part of the reason for this article.

Some outbreaks of Costia have been known to be salt resistant for at least two years. I saw my first case of salt resistant Costia in late 1996 on some Japanese imports straight from Los Angeles California. The Costia resisted zero-point-nine-percent stiff salt solutions and finally required Formalin for clearance, which works extremely well.

Costia is responsible for a lot of the recent fish mortalities we’ve seen after Japanese style shows.
There are several reasons for this, which I wanted to discuss here.

  1. Costia resists drying. Empty tanks, nets, even dried nets and hoses, can transmit infective Costia from one group of fish to another. Folks are not very cautious about nets and bowls. A retail facility that does not rinse or disinfect their nets and bowls between tanks is capable of infecting every fish they sell, whether they originate in infected tanks or not.
  2. Costia is not always evenly distributed among fish populations or even upon an individual fish. What I am conveying is that you may have a collection of fish in which only a small percentage of fish will have Costia. Numerous biopsies of some healthy looking fish are negative while the affected fish swarm with Costia. An immune capability is suspected among those fish that do not show morbidity under Costial attack. Secondly, the Costia may exist in small “patches” on skin and gill and be missed in routine scrapes. It is imperative that whenever you’re biopsying a fish, you biopsy general locations such as between the gill covers and the pectoral fins. But that you also biopsy any red or white patches upon the fish.
  3. Costia is easily missed under routine microscopy. There is an important reason why. For a definitive diagnosis, a microscope should be able to perform a competent 200X scanning power. 400X is sometimes important to diagnose Costia when numbers of organisms are low. Many of the new Chinese microscopes are labeled with 40X optics and 10X oculars but despite the listed caliber, are nevertheless poor at imaging at that power. So you often see nothing.
  4. Leaving the iris diaphragm open on your microscope defeats the necessary contrast to diagnose Costia. You should use the lowest power light and the smallest aperture on your iris diaphragm. For more on this, refer to the book or the web page for a diagram of these important microscope parts.
Symptoms and Treatment of Costia - Ichthyobodo necatrix
Symptoms and Treatment of Costia – Ichthyobodo necatrix

It has unfolded in several scenarios that after shows, participants begin to lose fish, sometimes with ferocious rapidity. The hobbyist does a few biopsies and does not find an organism. Rumors of a virus begin to spread. Finally, a competent biopsy is taken and viewed under a powerful microscope and the Costia is discovered. Unfortunately, it is often too late for a bunch of fish, when the proper biopsy and microscopy is done.

Symptoms and Treatment of Costia – Ichthyobodo necatrix

Recently, a good friend of mine had some fish that were beginning to isolate. The fish developed reddish lesions on the skin, and face. Some white slime was attendant at these lesions. Biopsies were taken and nothing was found. I asked if he’d biopsied the specific lesions themselves, and indeed he had not, because he felt it might further traumatize damaged tissues. This was a logical concern, to be sure, but as I stated before. Costia can exist focally, in small patches that can be missed unless they are deliberately scraped.

Formalin is the best treatment for salt resistant Costia.

The general idea of this Formalin treatment is to apply fifty PPM Formalin (two milliliters(equivalent to cc) per ten gallons) to a tank with the filter bypassed. Increase circulation with a floom or with a spraybar. Run this level of Formalin for two hours and then execute a forty to fifty percent water change, with de-chlorinator. Repeat the treatment in 72 hours. Do this Formalin treatment for a total of three treatments and you can rid your system of Costia and Flukes.

You can also use 1cc per ten gallons with the filter bypassed for the first 2 to 4 hours of the application, without water change but you should watch your Ammonia and Nitrite levels. Nitrification will be upset by the Formalin impact on beneficial bacteria.

There is an important, auxiliary treatment for Costia which I have found to be very effective at slowing down the infection. I have been using topical hydrogen peroxide 3% USP applied directly to the patches. Here’s how that works:

When you see a fish, or a group of fish with patches of red, or white – perhaps even raised scales, you would be advised to to biopsies of the fish between the gill covers underneath, down the pectoral fin and tail, and finally taking biopsies from the patches themselves. If you can confirm Costia, you simply apply a cotton ball or gauze pad soaked in hydrogen peroxide 3% USP to the patchy areas. They foam madly. Nod and smile, with satisfaction that you just dropped the hammer on a bazillion Costial organisms and are allowing early healing of their infested area to occur.

This has been particularly effective in some of the Ranchu goldfish that I keep, where facial or body scarring might be highly undesirable. These fish are able to handle high levels of salt with aplomb, so I usually endeavor to treat the focal lesions with peroxide. Then I salt the system to zero-point-six-percent to-zero-point-nine-percent.

There are several important follow-up points to this article.

During and after your treatment of Costia with salt at zero-point-three-percent, it is imperative that you serially biopsy your specimens to make sure the numbers of Costial organisms are decreasing or are absent. If you’re still seeing Costial organisms after 72 hours in zero-point-three-percent salt, some level of resistance can be assumed. At that point you should either increase the salt concentration to zero-point-six-percent to-zero-point-nine-percent or consider Formalin. You should not use Formalin at fifty PPM with the higher levels of salt. I have used zero-point-three-percent salt and left it in during Formalin treatments. This has caused no problems in cooler water with high circulatory rates. I caution you that stiff (zero-point-nine-percent) salt solutions coupled with Formalin might create an oxygen availability/transfer problem. All oxygen tension problems become more acute under conditions of warm water, e.g. water over eighty DGF

A theory exists that Costia may exist in the fishes’ cloaca, using these sequestered surfaces as it might use any other extension of the surface of the fish. In the cloaca, the organisms may be protected from short-term treatments like Formalin, and this ability to inhabit the cloaca is proposed as one of the possible causes of unexplained recurrence of the disease. Currently, the time has not been available to biopsy the cloacas of infected fish nor to attempt or ascertain the safety of clearance of said pathogens by swabbing the vestibule with peroxide.

Do not let your fish out from under your effective treatment until all biopsies are negative for at least three days.

KEY POINTS OF THIS ARTICLE

  1. Costia may be salt resistant
  2. Costia may be focal, not general in distribution and so it is often missed on biopsy.
  3. One should biopsy “patches” and lesions, not just healthy tissues.
  4. Salt and Formalin are mainstays to treatment.
  5. Peroxide (three percent USP) swabs may speed healing at the lesions.
  6. Biopsies are IMPERATIVE during treatment to establish sensitivity to the chosen treatment and clearance
  7. A very good microscope and competent technique are mandatory for the diagnosis of Costia as it is easily missed.

Thank you for your time.

Doc Johnson

The following is a thorough discussion of Costia and other parasites and their treatments

Enter your email address for a free PDF of this article including its images.

Enter your Email Address

My Favorite Amazon Recommendations

Items and content will not show in "Reader View" check your browser.

This is The LCD Screen Scope
We Did The Tutorial With. I did a twenty page tutorial (Here's the tutorial) with video, audio, images and even little parasite movies to show you how to use a microscope. 

This Filter is Good For BIG Dirty Tanks
I've been wrestling with water quality with the turtles. The sponges work GREAT, but in THOSE turtle systems where they eat MICE the poops are bulky. This filter can handle it. In "Tortu's" tank, it's got an 800 gph pump and it rocks. 

PraziPro for Flukes
They nailed it. Figured out the solubility and worked out the dosing. It works. 

Buy Some Good Koi?
No, this isn't really for the 'high end' collector y'all. But for someone who isn't near a decent garden center, here are "good-to-quite-good" Koi you will like at a very good price. I know these guys personally.

Best Food, Ever
It's made for (and I discovered it for) my Blood Parrots but the small size, intense color enhancers and excellent formulation make it superb young-Koi food. Oh, and it's AMAZING on color-cichlids like Flowerhorn and Blood Parrots. 

Pro Air 60 Aerator is a VERY high output air pump pushing my whole fish room (17+ drops), and I have one at home driving everything there, and I have one as a back up. 

Formalin Malachite (Not dilute)
There are formalin malachite preparations at 10%, 22% and 37%. There's economy in the concentrates. Hard to get Prime shipping because air transport is curtailed. This is a good value on 32 ounces. 

Topical For Koi and Pond Fish Ulcers
I like 7% tincture of iodine because it stains but it's hard to hurt anything with it. Used with a WOVEN gauze, this works well to clean and disinfect a wound. Only use ONCE. Do not 'repeatedly' scrub wounds. 

Confectioner's Glaze 
Is the way to bind a medication to fish food. Gone are the days of paste food and oil. The write up is done, it's RIGHT HERE.

Koi Health & Disease
Hopefully this link takes you to the newest edition by PRIME to get it to your house the fastest. 

I have over ten of these Titanium Heaters in my fish room and at home. They're a paradigm shift in aquarium heating. They're titanium and 400W for under $30! Whaaaaaaaaat?

CyroPro by Hikari is safe and easy for Anchor Worms and Fish Lice.

Whatever heaters you use, back yourself up with a temperature controller, it'll turn on, and off your heaters. If your heater seizes "on" at least the thermostat will stop a tragedy. 

LifeGuard by Tetra is a tablet version of a tame 'chloramine-t' or 'halamid' compound that's easy to get and good on bacterial infections, in baths. 

Antimicrobial
If you're making medicated feed for a larger group of fish, this will come in handy. Dosing is available in the site. 

For me, filtration-of-choice
For aquariums, even small Koi holding facilities or small ponds. These sponge filters are cheap, easy to clean, and they clear hazes very well when used with some Accuclear or similar.

Rubber sided, round, nettable tanks
Make great hospital or quarantine facilities. They SHOULD cost about $200-300 depending on size, but this, lower quality unit (while panned in some reviews) may be good. Don't overfill and make sure it's propped up.

1200 Watt heater, on a thermostat held securely above the waterline, works GREAT as a large tank heater. That's all I'll say because there's risk of electrocution and all that. But then, even in a bucket you could get killed. Sound like fun?
I have several of these ALLIED PRECISION stainless ones that are a couple years old. Working still. 

Potassium Permanganate 
500 grams could be a lifetime supply but it's 50% more than the 100g cost wise, for 500% more amount. Dosing is in the site and the book.

What Does Ajax Eat?
I looked for something well formulated, with meat as the first ingredient. Something UNDER $2/lb and something they could deliver for free. And this was it. He looks and feels great on it.