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Ichthyophthirius multifiliis

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Title: Ichthyophthirius multifiliis  
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Language: English
Subject: Fish diseases and parasites, Bath treatment (fishkeeping), ICK, Quarantine tank, Ich
Collection: Ectoparasites, Oligohymenophorea, Parasites of Fish, Veterinary Protozoology
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Ichthyophthirius multifiliis

Ichthyophthirius multifiliis
Cichlid showing the white spots characteristic of ich
Scientific classification
Domain: Eukaryota
(unranked): SAR
(unranked): Alveolata
Phylum: Ciliophora
Class: Oligohymenophorea
Order: Hymenostomatida
Family: Ichthyophthiriidae
Genus: Ichthyophthirius
Species: I. multifiliis
Binomial name
Ichthyophthirius multifiliis

Ichthyophthirius multifiliis (commonly known as freshwater white spot disease, freshwater ich, or freshwater ick) is a common

  • in layman's terms.IchthyophthiriusLife cycle and treatment of
  • Your Guide to Freshwater AquariumsShirlie Sharpe's
  • Detailed life cycle of Ichthyophthirius multifiliis at MetaPathogen
  • Treatment information for freshwater Ich at the Aquarium Wiki
  • Genome Database Wiki Ichthyophthirius IchDB -

External links

  1. ^ a b c d e Noga, Edward J. (2000). Fish disease: diagnosis and treatment. Wiley-Blackwell. pp. 95–97.  
  2. ^ a b Ostrow, Marshall E. (2003). Goldfish. Barron's Educational Series. p. 79.  
  3. ^ a b c "Ichthyophthirius Multifiliis (White Spot) Infections in Fish" (PDF). Retrieved 2015-06-06. 
  4. ^ [2]
  5. ^ Blasiola, George C. (2000). The saltwater aquarium handbook. Barron's Educational Series. p. 146.  
  6. ^ Lin YK, Lin TL, Wang CC, Wang XT, Stieger K, Klopfleisch R, Clark TG (Mar 2002). "Variation in primary sequence and tandem repeat copy number among i-antigens of Ichthyophthirius multifiliis". MOLECULAR AND BIOCHEMICAL PARASITOLOGY 120 (1): 93–106.  
  7. ^ a b Xu, De-Hai (2014-02-01). "Preventing Ich". Tropical Fish Magazine. Retrieved 2014-04-07. 
  8. ^ a b Foster, Race; Smith, Marty. "Ich in Freshwater Fish: Causes, Treatment, and Prevention". Retrieved 2014-04-07. 


  • Marine ich for the similar disease of marine fishes

See also

Partially treated fish may initially harbour low numbers of unseen trophozoites, often in the gills. This subclinical carrier will cause another outbreak weeks later, most likely when stresses occur or uninfected fish are introduced to the aquarium.

When ich is diagnosed early, effective treatment is used, and stresses are minimised, mortality rates can be low. However, if the infection is at an advanced stage, treatment protocols are not followed, and the fish are stressed, higher death rates will occur. When a fish has had ich eradicated, it may develop partial resistance to reinfection.


Chemical treatments include formalin, malachite green, methylene blue, chelated copper, copper sulfate, potassium permanganate and quinine. There are also a large number of proprietary treatments available for the treatment of white spot, and the related Oodinium (velvet disease). Chemical treatment is only effective against free-swimming juvenile parasites [tomites].[3] All treatments target the free-living theronts and tomonts, which only survive about two to three days in the absence of a host fish.

Chemical treatments

One method of treatment for ich consists of adding aquarium salt until a specific gravity of 1.002 g/cm3 is achieved, as the parasites are less tolerant of salt than fish. This is not practical in ponds because even a light salt solution of 0.01% (100 mg/L; pure water at 4 °C or 39 °F), would require large quantities of salt. Fish can be dipped in a 0.3% (3 g/L; pure water at 4 °C) solution for thirty seconds to several minutes, or they can be treated in a prolonged bath at a lower concentration (0.05% = 500 mg/L; pure water at 4 °C).


For treating koi and goldfish, chlorine, in the form of tapwater, is very effective in removing not only the threadlike parasites, but eventually the persistent cysts. Thread like infestations on fish will disappear overnight, cysts will take a couple of weeks and possibly a couple of water changes to eliminate. Aquarium lighting is used to detect the presence of parasites, as the filament like threads fluoresce at these light frequencies.


Heat treatment can be highly effective, and it can be combined with other treatments. However, it can only be used on fish that can tolerate high water temperatures, and is unsuitable for cold water fish like koi and goldfish, but even in those cases, a higher water temperature will accelerate the life-cycle of the parasite, allowing other treatments to take effect sooner.

Heat treatment

Several different aquarium treatments are commercially available to treat ich and similar ailments.

Commercial treatments

If ich is detected before it becomes too serious, a number of different treatments can be applied.

Any treatment method must take into account the species of fish (some will not tolerate certain medications), how many of the fish are affected, and the size and kind of environment. Temperature affects how quickly the parasites multiply, so increasing the temperature can force them through their life cycle more quickly, allowing quicker treatment.[8]

Unfortunately, an efficient prevention of the disease by vaccination is not possible, although several studies identified potential vaccine candidate proteins, i.e. i-antigens, of the parasite.[6][7] The most effective prevention is quarantining new fish for two weeks and plants for four days in a separate tank.[8] Fish that survive an ich infection may develop at least a partial immunity, which paralyzes trophonts that attempt to infect it.[7]

Ichthyophthirius multifiliis (ich) is a common single-celled parasite of wild fish that finds its way into hatcheries through their water supplies (often streams and rivers that harbour wild fish populations).


Gill infection may cause breathing at the surface and fast respiration. Gill examination may reveal numbers of white spots or wet mount of a gill from a biopsy may reveal the trophozoites. The fishes' breathing can slow, causing them to rest on the sand or gravel.


The eye becomes cloudy almost to the point of whiteness and the fish lose vision. The causes behind this disease can vary. An increase in parasites in the aquarium is the most common cause but severe stress, old age, or malnutrition can all lead to this condition. Treating this condition requires an investigation of water quality. Once the water quality is high enough, the fish will usually recover by themselves within one to two weeks. Thus, it is advisable to wait for that time to elapse before administering antibiotics.


Visible ich lesions are usually seen as one or several characteristic white spots on the body or fins of the fish. The white spots are single cells called trophozoites or trophonts, which feed on the tissues of the host and may grow to 1 mm in diameter. A smear should show ciliates if white spot is present.


A subclinically infected fish will not show any of these signs. For example, a healthy fish with a newly attached trophozoite will not yet have clinical disease. The trophozoite is not visible to the naked eye until it has fed on the fish and grown to one or two millimetres. A trophozoite attached to the gills is hard to see. A subclinically infected fish may initially only have a single trophozoite.

  • Anorexia (loss of appetite, refusing all food, with consequential wasting)
  • Rapid breathing
  • Hiding abnormally
  • Not schooling (in schooling fish)
  • Resting on the bottom
  • Flashing
  • Rubbing and scratching against objects
  • Upside-down swimming near the surface

Typical behaviours of clinically infected fish include:

The diagnosis of "Ich" can easily be confirmed by microscopic examination of skin and gills. Remove several "white spots" from an infected fish, then mount them on a microscope slide with a few drops of water and cover with glass. The mature parasite is large and dark (due to thick cilia covering the entire cell). It has a horseshoe-shaped nucleus, which is sometimes visible under 100x magnification. The adult parasite moves slowly by tumbling. The immature forms [tomites] are smaller, translucent, and move quickly.[3]

This Siamese fighting fish developed spots characteristic of ich (including one between his eyes) upon arrival from a pet store. The symptoms disappeared after treatment with a parasite-preventing water additive.
Two juvenile clown loaches with ich. Characteristically, for this stage of infestation, both are hiding in an ornament.


Other abiotic factors can increase both fish and tadpole susceptibility to ich. These factors include decreased temperature, predatory cues (crowding, fighting) and increased levels of UV-B radiation.

There is no dormant stage in the lifecycle. Ich does not lie in wait for a weakened fish to infect. However, any factor that reduces immunity, such as changes in water temperature and quality, accelerate an outbreak of Ich in a subclinically infected fish. Ammonia, nitrite or high levels of nitrate in water do not in themselves cause clinical cases of Ich. However, poor water quality stresses fish, which allows an outbreak to spread rapidly and increases mortality rates.

Predisposing factors

Marine ich is a similar disease caused by a different ciliate, Cryptocaryon irritans.[5]

This life cycle is highly dependent on water temperature, and the entire life cycle takes from approximately 7 days at 25 °C (77 °F) to 8 weeks at 6 °C (43 °F).

  • Feeding stage : The ich trophozoite (a protozoan in active stage of life) feeds in a nodule formed in the skin or gill epithelium.[1]
  • After it feeds within the skin or gills, the trophozoite falls off and enters an encapsulated dividing stage (tomont). The tomont adheres to plants, nets, gravel or other ornamental objects in the aquarium.[1]
  • The tomont divides up to 10 times by binary fission, producing infective theronts, thus dividing rapidly and attacking the fish.[1]

The ich protozoan goes through these life stages:[1]

Life stages


  • Life stages 1
  • Predisposing factors 2
  • Diagnosis 3
    • Skin 3.1
    • Eyes 3.2
    • Gills 3.3
  • Treatment 4
  • Commercial treatments 5
    • Heat treatment 5.1
    • Chlorine 5.2
    • Salt 5.3
    • Chemical treatments 5.4
  • Prognosis 6
  • See also 7
  • References 8
  • External links 9

Whitespot is very damaging to the gills and skin. In heavily infected fish it can cause a rapid deterioration of condition, considerable distress and death. Infected fish have small white spots on the skin and gills (Fig. 2 and Fig. 3) and produce excess mucus, due to irritation. Whitespot causes most damage when entering and leaving the tissues of the fish. This can lead to the loss of skin and ulcers. These wounds can harm the ability of a fish to control the movement of water into its body. Damage caused to the gill tissue of an infected fish can also reduce respiratory efficiency. This means it is more difficult for the fish to obtain oxygen from the water, and becomes less tolerant to low levels of dissolved oxygen.[4]


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