Freshwater Disease Guide

The following diseases and health problems have been covered.

Click the links to proceed quickly to specifics.

Parasitic Infections
Anchorworm (Lernaea elegans)
Black Spot Disease (Uvulifer ambloplitis)
Body Fungus (Saprolegnia spp.)
Camallanus cotti and Camallanus lacustris
Capillaria
Dactylogyridea
Diplostomosis (Diplostomum spathaceum)
Ergasilus
Fish Leech (Piscicola geometra)
Fish Lice (Argulus spp.)
Glossatella (Heteropolaria colisarium)
Gyrodactylidea
Neon Tetra Disease (Pleistophora hyphessobryconis)
Whirling Disease (Myxosoma cerebralis)
White Spot Disease (Ichthyophthirius multifiliis)

Flagellates
Carp Pox
Chilodonella
Costia (Ichthyobodo necatrix)
Glossatella (Heteropolaria colisarium)
Nematodes (Internal Parasites)
Tetrahymena
Trichodina
Velvet Disease (Oodinium spp.)

Bacterial and Viral Diseases
Bacterial Fin Rot
Bacterial Gill Rot
Columnaris
Enteric Red Mouth (Yersinia ruckeri)
Erythrodermatitis
Fish Tuberculosis (Mycobacterium spp.)
Hemorrhage Septicemia (Aeromonas hydrophila)
Lymphocystis

Health Issues, Defects and Deficiencies
Acidosis/Alkalosis
Acute Poisoning
Air Bubble Disease
Body Tumor
Cloudy Eyes
Constant gasping around the surface
Constipation
Continuous darkening of the whole body
Damaged/Pinched Nerves
Dropsy of Aquarium Fish
Gill Curl
Goiter
Hole in the Head
Insidious Intoxication
Osmotic Shock
Patchy Disease
Swim Bladder Disorder


Note: All previous sticky discussion threads can still be found here. Click links under Discussion Thread slot to proceed to those threads.

WARNING!
Please be sure to check the treatment information first and contraindications before proceeding with the treatment course!
http://monsterfishkeepers.com/forums/showthread.php?t=295289

White Spot Disease (Ichthyophthirius multifiliis)
Synonyms:
Ich, Ick

Symptoms:
Early signs of white spot begin when fish flick themselves against rocks. They may also swimming in an odd behaviour as if they were trying to use the water to wash away an irritation. Some of the more common causes are stress, bad water conditions, live food that have been infected by the pathogens or already infected fish without quarantining it.

Description:
Ich is a protozoal infection that afflicts fish and can rapidly kill them, most often by damaging gill tissue. It is highly infectious and potentially lethal and manifests as tiny white spots all over the fish. The spots are no larger than grains of salt. The wide host range of this parasite is its life cycle, and speed of multiplication especially in a tropical aquarium. When you see the white spot on your fish, it is already too late for those ich particles to be avoided.

The organisms, trophonts goes through a life cycle of a small white spot feeding on your fish which drops off to the floor of your tank and encases itself in a cyst called tomont. While encased in a cyst, it divides into up to 2000 new mobile organisms called theronts. The cyst then ruptures, thus releasing the theronts which seek out a host to feed into. They must locate a host within 24 hours otherwise they will die. Only the mobile stage is vulnerable to treatments.

Ich will appear if the fish is stressed. Note that it acts more as a 'contaminant' and is not part of the tank's ecosystem. Any new fish should be quarantined for 2-4 weeks. Failing that will increase the risk of introducing diseases which wil affect other occupants. New fish are always possible carriers of diseases.

Treatment:
Salt
Instructions
Increase the temperature to at least 84-86 degrees as much as the fish can tolerate. Add aquarium or table salt (dissolved in water) at a ratio of 1-3 teaspoons of salt per gallon of water in your tank equivalent to 0.1-0.3% depending on the tolerance level of your fish.

For basic procedures, here are the steps.
1. Dose one teaspoon per gallon of salt or equivalent to 0.1%.
2. After 12 hours and assuming the fish has tolerated it very wellso far, repeat step 1.
3. After another 12 hours, repeat step 1 again.

While waiting, it does not hurt to add a powerhead or airstone to increase the oxygen level. Over the first couple days, your fish will appear worse and will eventually recover as the treatment progresses. In most cases, ich will disappear on the sixth day. However, there is still a probability that some cysts have not yet ruptured so it is advisable to keep the treatment up for full ten days.

If you are not able to raise the temperature at all especially if you are dealing with fish that lack tolerance for temperature above 80 degrees Fahrenheit, you may need to extend the treatment although a good general guideline is to continue 7-10 more days of treatment right after the ich had seemingly disappeared.. At 85 degrees Fahrenheit, the life cycle of ich is quicker. The colder the temperature, the slower the life cycle thus the treatment will extend even longer than required.

Level of Tolerance
For bottom dwellers such as plecos and loaches, you may need to maintain the saline solution at 0.1-0.2% so it will not be detrimental to them although there have been few instances where some catfishes can tolerate as much as 0.3%.

Do make sure your fish can tolerate the elevated saline solution. If in doubt, be prepared to do a water change to relieve the fish of the osmotic stress caused by the salt. Try not to lose focus on the actual saline solution you already administered or you might end up overdosing the salt more than it was necessary.

Clown loaches and young oscars are notorious for getting ich after they are transferred to your tank. These and many others can tolerate salt. If you are unsure about your fish’s tolerance for salt, be sure to look for answers in a reference book or ask an expert.

A salt test kit available at your local fish store will help you get the exact dosage. Something in the range of .2%, is where you want to be.

Water Changes vs. Salt
Should a water change be necessary, make sure you redose the salt solution per the water volume replaced.

For example, a 10g needs 30 teaspoons at 3 teaspoons per gallon of water measurement. If you wish to change at least 50% of the water, then another 15 teaspoons of salt should be redosed to keep the saline solution effective against the parasites.

Teaspoon vs. Tablespoon Measurement
For those not familiar with the teaspoon = tablespoon conversion, a leveled heap of tablespoon is equivalent to 3 teaspoons whereas a round heap of tablespoon is equivalent to 5 teaspoons.

In Australian standard, a tablespoon is equivalent to four teaspoons so please adjust the necessary dosage as much as possible.

Plants Goners Or Not?
Unfortunately many plants do not do well with this salt treatment and may appear to wither but will usually come back in time once the salt treatment is over. Removing them to a salt free environment after a thorough rinsing may save them, however they must be kept at a high temperature or for an extended period of time. When the cyst breaks up in the plant holding tank, the small parasites will be unable to find a host and will die within 24-72 hours depending on the environmental conditions. Ich is easily transferred to other fish tanks so do not share nets, heaters and wet hands between infected and non infected tanks.

Mutual Relationship of Bacteria vs. Ich
Abstract explaining the presence of endosymbiotic bacteria within ich and bacteria with mutual relationship towards ich developing its infective capability can be found here.
http://thegab.org/forum/viewtopic.php?f=8&t=20210

Other Treatments:
Malachite Green, Formalin

Do NOT combine formalin and salt.

Check this list for contraindications of the above treatments.
http://monsterfishkeepers.com/forums/showthread.php?t=295289

Authors:
Lupin
Anythingfish
ChileRelleno
guppy
SkepticalAquarist.com
Tokis-Phoenix

Discussion Thread:
http://www.monsterfishkeepers.com/forums/showthread.php?t=20681

Columnaris
Synonyms:
Cotton-wool, Mouth Fungus, Flexibacter, Flexibacter columnaris

Symptoms:
When fish are infected with this pathogen, the following signs can be anticipated:

Skin
There will be necrotic lesions on the skin, which often are white/gray coloured with an edging of red. These will quickly in one to two days, transform into ulcers with have an orange/yellow colour, caused by the bacteria decaying the underlying tissue.

Gills
Similar effects very typically occur on the gills, but may for the average hobbyist be somewhat harder to observe at least in the early stages. The progression of these ulcers, causes the fish to have great trouble with its respiration, and thus can quickly lead to fatalities. If the gills are examined, excessive amounts of mucous, are to be expected.

Behaviour
The fish will become very listless and lethargic, often will hang at the surface, trying to breath there, although on occasion, the fish will rest on the bottom of the tank. Reluctance to feed is very typical and the fish will become anorexic. Respiration is often rapid, as the fish fights to overcome the damage done by the infection to its gills.

Body
In some cases, the lips of the fish will become swollen and macerated, and a milky slime like film can be observed with the naked eye on parts of the body.

Fins
Large milky patches can be seen quite easily on the fins of the fish, and this is usually an indication that the disease has progressed to a degree that cure will become much more difficult. One typical sign is the appearance of a saddle-shaped lesion usually around the area of the dorsal fin, and this occurs so often, that the name 'saddle back disease' is often used in aquaculture to describe this infection.

Description:
This is bacterial infection which is very common in the aquaria and is very contagious especially in stressful conditions including undercleaned, overcrowded environment. Immediate action is needed to contain it before it spreads to other fish.

Cannibalism of infected carcass of fish will always encourage progress of columnaris transmission to other fish. It is advisable to remove the dead infected fish immediately.

Treatment:
According to Oddball, this has worked for him on freshwater and brackish water fish.
1. Terramycin and Trypaflavin
a. Pull carbon.
b. Gravel wash and water change to reduce pathogen population.
c. Terramycin bath.
d. Add salt to the water to aid gill functions.
e. Treat food with Terramycin to fight internal infection.
f. Treat tank with chloramphenicol + acriflavin (trypaflavin) per dosage on container.
g. Gravel washes/water changes every other day. Replace salt and meds.
h. Treat for an additional 10 days after symptoms are no longer present.

2. Ophthalmic Ointment
Wipe it onto the affected areas of the fish (instead of dipping the fish in a bath).

3. Medicated Foods
Foods (dry/frozen/fresh) can be treated with medications to target internal infections in a fish. The meds (usually liquid but, can be powder) are added to regular foods (per med instructions). For a disease, such as columnaris, internal medication is important since the disease can cause gill damage/necrosis.

The combination of Maracyn and Maracyn 2 (erythromycin and minocycline respectively), kanaplex and tetracycline can be used as well as alternatives. They can be incorporated in gel foods.

Continue reading on this page for recommended amount per the amount of gel food reserves.
http://thegab.org/Articles/MedicatedGelFood.html

4. Sera Baktopur and Sera Baktopur Direct
1. Add 22 drops/1 ml per 5 gallons of Sera Baktopur in your tank.
2. Add a tablet of Sera Baktopur Direct. One tablet per 20 gallons is the dosage.
Note that #1 and #2 should be done on the odd number of days. First day, third day, fifth day and so on.
3. Do a 10% water change on the second day.
4. Repeat #1 and #2 on third day. The dosage has to be done according to how many gallons of water you replaced. Water changes should be done on even number of days.

Warning:
The combination of Sera Baktopur and Sera Baktopur Direct will harm your biological filtration.

Authors:
Lupin
Oddball
Tokis-Phoenix

Discussion Threads:
http://www.monsterfishkeepers.com/forums/showthread.php?t=21286
http://www.monsterfishkeepers.com/forums/showthread.php?t=31362

Hole in the Head
Synonyms:
Head and Lateral Line Erosion

(1)Water Quality
Get your water quality/chemistry perfect, NH3-0, NO2-0, NO3- 0/20ppm,
check your filters & clean'em if necessary (reduces alot of NO3), gravel vac & PWC, do small PWC's (25%) every other day.
Just about everyone will agree that bad water chemistry and HITH go together like apple pie -n- ice cream...

(2)Diet
Feed a well balanced and varied diet* (See below).

(3)Vitamin Supplements
Add liquid vitamin supplements to all food and vary their diet.
Soak or load everything you feed the fish with vitamins until cured and watch your water.
Vitamins that you add to your tanks water are worthless (IMO).
We use "Vita Chem", our fish get it regularly.
This particular brand is available at most on-line retailers and at better LFS's (We get ours at BigAls).
http://www.bigalsonline.com/catalog/...d1=2911;pcid2=

(4) Supplementary treatment
I would add a dose of salt to the tank, this encourages slime-coat production and gill function amongst other things.
Also a dose of Melafix and Pimafix, these have been known to help healing and prevent secondary infection.

(5)Temperature
Gradually increase your tanks temp to aprox 80'-82'f.
Increased temp increases metabolism which can influence the immune system thus possibly speed healing.

(6)Medicate
Alot of folks blame Hexamita for HITH and thus treat for it with medications, BUT, studies have been done showing that Hex (and others) is/are a secondary infection/s (Whether or not Hexamita plays a key-role with HITH infections is controversial).
You need to do what "You" feel is right and correct after researching this for yourself, google "HITH causes prevention and cure" or some such, and visit Cichlid specific forums for more info.

Some folks also think that filter carbon dust plays a role...
Carbons role is controversial.

Some folks also think that stray electrical currents are to blame...
Stray electrical currents role is controversial at best.

It seems there are no absolutes as to the cause, but just like ICH there are many ways to treat it and proponenets/opponents of each treatment.

I say again though...
Perfect water quality and a varied nutritious diet supplemented with vitamins.

Here's a good article on HITH available here at Oscarfish,
http://www.oscarfish.com/cms_view_article.php?aid=3
For more simply Google, 'HITH'.

DIET
A quality cichlid pellet or stick should make up 75-80% of your O's diet.
These are my primary foods...
Pellets, Carnivore sticks, freezedried krill, algae wafers, fresh nightcrawlers, fresh/freezedried earthworm (Any worms are great foods!), fresh crickets, fresh mealworms, almost any insect I catch (Insects from outside do pose a risk of insecticides which can harm your fish, be careful.).

I rotate store bought nightcrawlers, crickets and mealworms about monthly on the menu.
I feed my 10"+ O probably 4-6 large crickets, 6-10 mealworms or 1-2 large nightcrawlers per feeding and he'll get'em every 2-3 days.

I feed or have fed my O all of these foods...
Raw/cooked shrimp, small bits of raw cut fish, beefheart, bitesize bits of fruits-n-veggies (zucchini, carrot, shelled peas, shelled corn, apple, orange, pear, papya and etc...), small tree/grass frogs (NO toads, and know which frog species your feeding as some can be toxic too.) and properly quarantined or raised feeder fish, these should be fed sparingly and rotated as snacks or dessert.
Do not feed unquarantined feeder fish from LFS/LPS, do not feed mammalian flesh (Animal fats from mammals and fowl are very bad for most fish).

I supplement his nutrition by soaking his pellets 4-5 times a week in a liquid vitamin.
I use Vita-Chem, available at some LFS's and on-line retailers, I get mine at BigAl's, http://www.bigalsonline.com/BigAlsUS...mfreshwater4oz
Alot of different types and brands are used, Liquid Centrum for example, but you could reasonably use any quality L. vitamin.

Authors:
ChileRelleno

Discussion Thread:
http://www.monsterfishkeepers.com/forums/showthread.php?t=21851

Dropsy of Aquarium Fish
Synonyms:
Bloat, Malawi Bloat

Symptoms:
Protrusion of scales, distended abdomen, pop-eye

Not all symptoms however will appear at the same time. It must be noted there are various causes of this issue so steps must be taken that the issue is properly diagnosed in order to rectify the actual cause of this issue.

Description:
The problem with this issue is that there are a number of "potential" causes therefore making it very difficult to determine the appropriate steps to be taken to correct the issue.

Care must be taken in diagnosing the actual issue. Usually, a necropsy (post mortem examination) is the best route to enable you to correct the issue before your other fish may end up getting victimized by this issue.

The following so far are known causes of this issue:
1. Internal parasites
The presence of some internal parasites in the abdominal area of the fish and possibly allowing the harmful bacteria to infiltrate the blood vessels can cause quite a lot of damage on the tissues and subsequently kill the fish.

2. Cancerous tumors
3. Excessive protein intake (especially with lack of fiber thereof)
4. Viral infections
5. Internal bacterial infections, usually a resulting secondary infection from external parasites

Aeromonas hydrophila, Flavobacterium columnare and Pseudomonas sp. are often responsible for this issue. This happens mainly after a primary issue was able to take its toll on the fish. Resolve the primary issue first, usually parasitic, before this resulting secondary infection.

If the cause is bacterial, the swelling typically comes on pretty rapidly. If swelling is gradual then one or more of the other potential causes are more likely. Unfortunately, treatment is most often useless at this point due to the advanced state of the disease process. When the illness, whatever the cause, has progressed far enough to cause internal swelling, the concomitant internal damage is usually too extensive to be repairable.

6. Infrequent water changes or sudden temperature drop
7. Polycystic kidney disease (PKD for short; resulting renal damage especially by a parasite, Hoferellus carassii which commonly affects goldfish but not koi)

For further information, please see this. Be warned that the topic contains graphic images of fish examined by necropsy after it passed away from polycystic kidney damage.
http://thegab.org/forum/viewtopic.php?f=8&t=20356&p=274596#p274596

8. Accumulating organic matter (nice breeding ground for parasites especially the parasite HC mentioned above)

Treatment:
Romet B
The latest research has shown that if the disease cause is bacterial and if the disease process is caught early enough, treatment with Romet B, a broad spectrum antibacterial, may be effective when used concurrent with an increase in water temperature to 84-86ºF for 2 weeks minimum.

BE CERTAIN to maintain HIGH OXYGEN LEVELS during such treatment since at these temperatures, water holds significantly less oxygen at these higher water temperatures. One of the suspected bacterial precursors to the disease process -- Aeromonas, is killed at these temperatures.

Erythromycin
Feeding foods soaked in ERYTHROMYCIN will kill the second suspected bacteria, Mycobacterium. In rare cases popeye has been found to be caused by Edwardsiella etarda. This is found only in fish that have been bred in outdoor ponds -- the functional bacteria in this case is carried by frogs. While fair to good results in treatment have been found by feeding Romet B., even better results have been found using injectable chloramphenicol or amakacin. This is best done by your veterinarian.

If parasites are a known cause, treat for them first for 3 days increasing the temperature to 86ºF as fast as possible.

Epsom Salt
Concurrently add 1/8 teaspoon of EPSOM SALT -- per 5 gallons of water or 1/4 teaspoon per 10g. Epsom salt may help reduce the internal pressure caused by the swelling. Extremely good aeration is necessary here due to the use of such high temperatures.

Metronidazole
Experienced Directions by Oddball
1. Remove carbon/resins from filter.
2. Perform a 30-50% water change (reduces free-floating bacteria population)
3. Add salt (teaspoon to a tablespoon per gallon) to aid the fish's osmotic regulation processes.
4. Treat with 250mg/20gallons of Metronidazole (Flagyl)
5. Leave for 3 days and do not feed.
6. After 3 days, perform another large water change.
7. Replace the salt.
8. Add full dosage of Metronidazole.
9. Wait another 3 days. During this phase, the bloat should be decreasing in appearance. In large fish, the water may take on an ammonia odor from the high volume of urea the fish should now be producing due to reducing the bloat and recovering renal activity.
10. 3rd day, another water change. Also, replace the salt and redose the metronidazole (full dose). If the fish looks to be well on the road to recovery you can offer a small feeding each day.
11. Another water change on the 3rd day. No meds but, I'd recommend the salt. You should be clear now.

This is the treatment I use on my africans, puffers, and my lungfishes/polypteridae. Knock on wood that it's worked every single time.

Feeding Metronidazole
Recommended dosage when combined with foods is 250mg of metronidazole per 25g of foods. Best mixed with gel foods.

Aside from the above mentioned metronidazole, it is recommended that sodium chloride be added. For further information on how to administer salt, please check here.

Other Treatments:
Oxolinic acid, injectable antibiotics such as Baytril and Fortaz

For injectable antibiotics, instructions of how to inject antibiotics can be found here.
http://thegab.org/Illness-and-Treatment/giving-your-goldfish-an-injection.html

Do NOT use kanamycin and other aminoglycosides as these are quite toxic to fish suffering from suspected renal damage.

Authors:
Lupin
Oddball
Tokis-Phoenix


Discussion Thread:
http://www.monsterfishkeepers.com/forums/showthread.php?t=45617

Gyrodactylidea
Symptoms:
Rubbing movements, overproduction of mucous membrane, listlessness around the surface, rapid breathing due to stress

Causes:
The livebearing flukes, Gyrodactylidea are responsible for the erratic behavior of the fish which will eventually be overcome by the stress. Gyrodactylidea is found more often in the ponds rather than the aquaria but they can be transported to the aquaria too if the infested pond fish is introduced. They prefer colder temperatures and are much less common in warm water aquaria.

Some species can reach 3 mm and can be seen with the naked eye if closely watched.

The flukes hook themselves to the fish's tissues severely damaging it and at this stage, the fish begins to rub itself around the aquarium. The flukes must be eliminated immediately as soon as you detect them.

Treatment:
1. Formalin (It has been noted that this is not very effective against the eradication of fluke eggs.

2. Potassium Permanganate

3. Flubendazole-Noted to be very effective against the fluke eggs.

4. Praziquantel
It can be bought as Prazipro available in online sites or petstores or Droncit in veterinary clinics.

5. Salt dips

6. Sera Mycopur

7. Sera Ectopur

8. Trichlorfon

9. Chloramine T

Dactylogyridea
Symptoms:
Rubbing movements, rapid breathing, one gill is usually shut while using the other

Causes:
Poor water quality, stress and overpopulation will allow the gill flukes to reproduce quickly and the fish soon begins to rub over objects. If they are heavily infested, then they will stand under the surface breathing heavily. Adult fish usually can tolerate minor infestations but if infested heavily or severely stressed, they will eventually succumb to the gill flukes.

Dactylogyridea is an egg-laying gill fluke that is just the opposite of the Gyrodactylidea. They live mainly in the gills and can be visible with the naked eye as they reach 2-3 mm. Eggs fall to the bottom of the aquarium or vat. The fluke after it hatches eventually finds a host where it can attach itself.

Gill flukes have hooks that they use to attach themselves on the mucous membranes of the skin and gills of the fish thus injuring them. As a result, secondary infections such as fungi, protozoans and bacteria will appear and start to overtake the fish. Treatment must be done immediately to stop this situation from getting to the worse.

Treatment:
1. Formalin (It has been noted that this is not very effective against the eradication of fluke eggs.

2. Potassium Permanganate

3. Flubendazole-Noted to be very effective against the fluke eggs.

4. Praziquantel
It can be bought as Prazipro available in online sites or petstores or Droncit in veterinary clinics.

5. Salt dips

6. Sera Mycopur

7. Sera Ectopur

8. Trichlorfon

9. Chloramine T

Bacterial Fin Rot
Symptoms:
The fins are frayed and getting shorter. Edges are whitish.

Causes:
Overpopulation, severe stress especially on transit, untreated injuries, poor water quality and poor maintenance are the main causes of fin rot. Fin rot can occur in connection with columnaris, fungal overgrowths, lesions and as a secondary infection to parasite infestations. Fish begins to have difficulty swimming due to the damaged fins.

Treatment:
Broad spectrum antibiotics, frequent water changes are a must to improve water quality


Picture retrieved from O-fish.com for reference purposes.

Whirling Disease (Myxosoma cerebralis)
Symptoms:
Clinically fish become deformed about the head and spine with the fish swimming erratically (whirling). Histologically there is necrosis of the cartilage with numerous spores present in the area of inflammation. The necrosis of the cartilage is the cause of the deformation.

Causes:
Myxosporidean parasite with a 10 micron oval spore with 2 piriform polar capsules. Parasite affects primarily young salmonids (rainbow trout most susceptible).

Transmission is believed to be by ingestion of spores. The life cycle of this organism is not completely known (believed to be indirect since myxobolus spores do not directly infect the fish) however, there appears to be a tubeficid oligochaetes (tubifex mud worm) as an important intermediate or transport host. It is believed that the parasite undergoes sporulation in the tubiflex worm were the organism takes on the form of a Triactinomyxon sp. It is believed that this parasite is then released from the tubifex worm and infects the trout. (ingestion of infected tubifex worms may also cause the fish to become infected)

Morphology
All information retrieved from Wikipedia for reference and archival purposes.

Triactinomyxon stage
The stages that infect fish, called triactinomyxon spores, are made of a single style that is about 150 micrometers (µm) long and three processes or "tails" that are each about 200 micrometers long. A sporoplasm packet at the end of the style contains 64 germ cells surrounded by a cellular envelope. There are also three polar capsules, each of which contains a coiled polar filament between 170 and 180 µm long. Polar filaments in both this stage and in the myxospore stage (see picture above) rapidly shoot into the body of the host, creating an opening through which the sporoplasm can enter.

Sporoplasm stage
Upon contact with fish hosts and firing of the polar capsules, the sporoplasm contained within the central style of the triactinomyxon migrates into the epithelium or gut lining. Firstly, this sporoplasm undergoes mitosis to produce more amoeboid cells, which migrate into deeper tissue layers, in order to reach the cerebral cartilage.

Myxosporean stage
Myxospores, which develop from sporogonic cell stages inside fish hosts, are lenticular. They have a diameter of about 10 micrometers and are made of six cells. Two of these cells form polar capsules, two merge to form a binucleate sporoplasm, and two form protective valves. Myxospores are infective to oligochaetes, and are found among the remains of digested fish cartilage. They are often difficult to distinguish from related species because of morphological similarities across genera. Though M. cerebralis is the only myxosporean ever found in salmonid cartilage, other visually similar species may be present in the skin, nervous system, or muscle.

Life cycle
Myxobolus cerebralis has a two-host life-cycle involving a salmonid fish and a tubificid oligochaete. So far, the only worm known to be susceptible to M. cerebralis infection is Tubifex tubifex, though what scientists currently call T. tubifex may in fact be more than one species. First, myxospores are ingested by tubificid worms. In the gut lumen of the worm, the spores extrude their polar capsules and attach to the gut epithelium by polar filaments. The shell valves then open along the suture line and the binucleate germ cell penetrates between the intestinal epithelial cells of the worm. This cell multiplies, producing many amoeboid cells by an asexual cell fission process called merogony. As a result of the multiplication process, the intercellular space of the epithelial cells in more than 10 neighbouring worm segments may become infected.

Around 60–90 days post-infection, sexual cell stages of the parasite undergo sporogenesis, and develop into pansporocysts, each of which contains eight triactinomyxon-stage spores. These spores are released from the oligochaete anus into the water. Alternatively, a fish can become infected by eating an infected oligochaete. Infected tubificids can release triactinomyxons for at least 1 year.The triactinomyxon spores swim through the water to infect a salmonid through the skin. Penetration of the fish by these spores takes only a few seconds. Within five minutes, a sac of germ cells called a sporoplasm has entered the fish epidermis, and within a few hours, the sporoplasm splits into individual cells that will spread through the fish.

Within the fish, there are both intracellular and extracellular stages that reproduce in its cartilage by asexual endogeny, meaning that new cells grow from within old cells. The final stage within fish is the myxospore, which is formed by sporogony. They are released into the environment when the fish decomposes or is eaten. Some recent research indicates that some fish may expel viable myxospores while still alive.

Myxospores are extremely tough: "it was shown that Myxobolus cerebralis spores can tolerate freezing at ­-20°C for at least 3 months, aging in mud at 13°C for at least 5 months, and passage through the guts of northern pike Esox lucius or mallards Anas platyrhynchos without loss of infectivity" to worms. Triactinomyxons are much shorter lived, surviving 34 days or less, depending on temperature.

Treatment:
Some drugs such as furazolidone, furoxone, benomyl, fumagillin, proguanil and clamoxyquine have been shown to impede spore development, which reduces infection rates. For example, one study showed that feeding Fumagillin to Oncorhynchus mykiss reduced the number of infected fish from between 73% and 100% to between 10% and 20%. Unfortunately, this treatment is considered unsuitable for wild trout populations, and no drug treatment has ever been shown to be effective in the studies required for United States Food and Drug Administration approval.

Black Spot Disease (Uvulifer ambloplitis)
Symptoms:
Clinically the fish have numerous black to brown spots up to 1 mm (dia) over the skin, gills and eyes. The spots contain a metacercaria surrounded by heavily pigmented fibrous connective tissue.

Causes:
Introduction of herons and kingfishers which are the definitive host, snails are the first intermediate host. Fish are the second intermediate host.

Black Spot Disease is more common in ponds compared to the aquaria.

Life cycle:

• • Adults found in intestine of kingfishers.
  • Unembryonated eggs are shed in water -->> hatch in 3 weeks -->> miracidium emerges.
  • Miracidium penetrates snail Helisoma trivolvis (ramshorn snail) -->> mother sporocyst -->> daughter sporocyst -->> furcocercous cercaria are released.
  • Cercaria penetrates skin of host and transforms into neascus metacercaria, where there is a strong tissue reaction -->> black spot
  • Fish then eaten by bird -->> metacercariae excysts -->> adult in intestine.

Treatment:
Frequent water changes are recommended.

Pathology
1. Strong tissue reaction due to mobilization of fibrocytes and melanocytes to create black spot.

2. If reaction is strong enough, total body fat of fish will be driven below 5%.

3. If fish enters winter in this condition, it will not survive because fish does not feed in winter and does not have enough fat reserves to over winter.

4. At least 50 cysts are necessary to cause mortality.

5. At least 10-20% of fish will die each winter.

6. Because of parasite overdispersion, 70-80% of the parasites the pond will also be eliminated in winter.