Fish Health - Hexamita

Health main page


Aeromonas Hydrophila
Ammonia Test Errors
Anchor Worm
Bacterial Additives
Blanket Weed
Carp Pox
Cat Damage
Costia (killer)
Common Myths
(Egg Compaction)

Fat Fish
Fish Louse
Gill Bleeding
Gill Disease
Gill Maggots
Goldfish Ulcers
Mechanical Fish
Mechanical Injury
Microscope page
Milky Skin
Mouth Cancer
My Fish Jumped
Neon Tetra Disease
pH Crash
Post Mortems
Skin Cancer
Swim Bladder
Tonic Salt
Vitamin C
Water Filters
Water Fungus
White Spot






hole in the head

Five years ago I saw 3 cases. This year I have seen 67. Hexamita is going to become a problem.

Hexamita is a small flagella around 3-6 micron in size and is a parasite found in the intestinal tract of goldfish and koi. This was formerly a cichlid infection but has been known about with carp and salmon and trout for a number of years.

Infected fish get extremely thin. The symptoms can take many months to show if the infection is low and the fish were in good health when infection was introduced .

Some times the abdomen can be distended showing symptoms of dropsy. The intestines may contain a yellow mucoid material. Recent taxonomic studies have labeled the intestinal flagellate with other names such as spironucleus, hexamita, or sprironucleus.

To diagnosed, make a squash preparation of the intestine, and examine under the microscope at a magnification of 200-400, using phase contrast or semi close your iris on your scope. Hexamita looks very similar to bacteria on a corpse. The parasite can be found where the mucosa (intestine lining) is broken. They move by spiralling and in heavy infections they will be too numerous to be overlooked - like bacteria on a corpse.

In tropical fish, hexamita mostly shows itself by holes developing around the head erea. In cichlids including discus, symptoms sometimes show the signs you look for in koi - the tadpole affect - all head and a thin body in it's latter stages, which also fits the description of fish tuberculosis.

hexamita goldfishNotice the white marks on the top of the fish's head and neck, like shallow craters, this form is far more common when fish are kept in tanks rather than ponds.

In koi the marks are very similar, but are smaller and more round and some times all around the head. There is no set pattern and mostly appear in the latter stages of this infection. They can also appear down the lateral line.

The disease spreads faster in tanks than ponds. The problem is I would class a plant free indoor heated pond 1000-2000 gals with high stock level as a tank, as infection spreads as fast.

hexamita goldfishNotice that the fish look in good health and many do until weight loss starts. Loosing weight may start before any holes appear, often showing white string feaces sometimes transparent. In some cases the fish can have this infection for many years with no ill affect to themselves while affecting others - how and why I don't know

Treatment now available no need to mix with food.

Example Case
"On advice from the Fish Helpline with regards to the diagnosis of hexamita, I contacted my local vet to obtain the necessary medication-metronidazole. After consultation, this was prescribed in tablet form 200mg per tablet. The ratio of medication to food was calculated by the vet at 1-1/4 tablets to 100grams of food.

I weighed out 100 grams of dried pellets food and then crushed this using a mortar and pestle to fine powder. I then crushed the 1/1/4 tablets and mixed thoroughly with the crushed food. To bind the food back together so that I could feed the fish I used gelatin, as advised by the vet. The gelatin was obtained from local supermarket. I mixed the gelatin into hot water as per instructions given on the packet using approximately half the sachet per 100gms of fish food - this was a bit hit and miss until I found the correct consistency to bind the food. The gelatin was added to the crushed food and mixed thoroughly until all the liquid was absorbed, and the consistency was like firm paste. This was then rolled by hand into large pellets approximately 15mm in diameter. These pellets were then cut using a sharp knife into smaller segments (the size of normal food) 6mm. I found it easier to do this than try to make small pellets initially.

The pellets were then allowed to set for approximately 30mins or until cold. Tthe food was then fed individually to each fish.

The food should be fed at 1% of fishes body weight daily for 7 days to all fish, however this I found was very impractical. Please note that once the food has been broken down and reconstituted with gelatin it does not float."

With kind permission from my client Mr. N I Rice.