Gyrodactylus spp. (Skin Flukes)

Sometimes called: Clamping Disease, Clamped Fins Disease, Skin Flukes, Pintail Disease
Sometimes confused with the clamping of fins that occurs when there is poor water quality. See: Clamped Fins, Shimmying
See also: Dactylogyrus Spp

The worm is ventrally flat. This species has 16 marginal hooks and 2 large anchors.

Flukes or clamping disease describes two tiny worm-like parasites called dactylogyrus and gyrodactylus. This page describes gyrodactylus.

The gyrodactylus worm is a small flagellated protozoan about 0.2 mm to 1.2 mm in length, the skin fluke. Unlike the dactylogyrus, it does not have eye spots. This worm-like creature attaches itself to the fins, gills and scales of fresh water fish. It feeds on mucus, epithelium, occasionally blood and other body fluids. The head and end of the fluke alternately attach to the fish, allowing it to move in a caterpillar-like action. The punctures open the way for aeromonas bacteria. It uses its hooks and leaves small puncture wounds. These penetrate the mucus membrane, opening a way for other pathogens to attack the guppy, particularly bacteria. (It also irritates the guppy, causing it to flash or scratch itself on objects.) The result is ulcers covering the body of the guppy, a condition sometimes associated with a severe gyrodactylus infestation.

Gyrodactylus is a pest in a wide range of fish, including tropicals and coldwater fish like trout. It does not use an intermediate host.

Along with gill worms (Dactylogyrus), the Gyrodactylus skin fluke is the most common parasite to infect guppies. In a study titled "Behavior Favoring Transmission in the Viviparous Monogean Gyrodactylus turnbulli" (Cable, Scott, Tinsley, Harris, Journal of Parasitology, 88(1), 2002, pp. 183-184) the authors identify a specific species (Gyrodactylus turnbulli) native to the guppy's natural habitat.

The gyrodactylus thrives in closed, highly populated systems, like guppy tanks. Normally they are not lethal, but in the closed space of the aquarium they can reach epidemic proportions.

One prominent study in fact used the guppy as the unhappy host of experiments designed to discover the parasite's habits (Scott ME & Anderson RM, The population dynamics of Gyrodactylus bullatarudis (Monogenea) within laboratory populations of the fish host Poecilia reticulata. Parasitology. 89 ( Pt 1):159-94, 1984 Aug.) The researchers report that the parasite has an almost unique way of reproducing among helminth parasites of vertebrates. Like its host, gyrodactylus gives birth to live young on the skin of the guppy. This makes the disease particularly devastating, because its entire life cycle is spent on the body of the guppy. Not only that, the developing larvae within the uterus of the adult worm can have embryonic larva developing insiide it. And these larvas in turn can have embryonic larva. In fact, there can be a 4th embryonic larva! Four for the price of one. This means gyrodactylus can reproduce quickly and spread from one guppy to another quickly.
It has a life cycle of 1 to 5 days.

This little terror has another trick up its sleeveless body. It can survive for a period without the presence of a host. This means that a badly infested tank should be bleached. You should also keep the sides of the tank clean. It can lay eggs in the slime.

Gill and skin fluke species tend to be fairly host-specific. Although most species can live on guppies, only a few species can reproduce at a rate to damage the guppy. This means that a fish like a catfish or an algae-eater can act as a carrier for a guppy-specific species of flukes

Symptoms and Behavioral Signs

Primary Signs:
•    shimmying
•    erratic side-to-side deflections of the body
•    flattened dorsal fin
•    eventually the fins become contracted and the fin rays fuse together

Other Possible Signs:
•    inflamed or dark skin, slimy, sometimes a grey film
•    fish rubs against hard objects (flashing)
•    rapid breathing
•    hooks cause frayed gills, which may become swollen
•    fish may become less tolerant of low oxygen and hang near the surface
•    sluggishness
•    skin ulcers (onset of secondary bacterial disease)
•    faded color
•    weight loss and emaciation
•    there may be slight bleeding under the skin, visible as little red spots

Causative Condition
Live foods can be carriers of this fluke. In the Cable, Scott, Tinsley, Harris study cited above, the Gyrodactylus turnbulli was found to leave the dead guppy and crawl caterpillar-fashion up to the water surface where it hung waiting for a live victim. Most dead guppies float at the surface when they die, before sinking. This is when the flukes dissert the body and spread at the top of the tank where other guppies come to feed. The authors also said it can be transmitted between live hosts in close proximity (i.e. within the confines of a guppy tank).
Notably the authors obtained their Gyrodactylus turnbulli flukes from a commercial supplier (read fish store).
The Scott and Anderson study noted above discovered that guppies acquired immunity to gyrodactylus parasites. "Long-term laboratory experiments demonstrated the inability of the parasite to persist within populations of the host in the absence of the continual introduction of naive susceptible fish. The experimental results suggest that acquired resistance to infection is an important factor determining epidemic behavior." (http://martin.parasitology.mcgill.ca/jimspage/biol/scottref.htm

This might explain why gyrodactylus seems to come and go in a fish room.

Diagnosis
A microscope is required to see the tiny flukes on the guppy's skin. The clinical signs listed in the above section are part of a diagnosis.
Take a scraping of the guppy's slime coat with a razor blade or fine knife. Even under a low power microscope (20x), minute wriggly organisms can be easily seen if the fish has flukes. If the fish can be put in a very small glass container, a lens will reveal the worms clinging to the guppy's body.
Prevention and Treatment
As usual, a properly functioning biological cycle in your tank, a sustainable stocking level and proper nutrition are essential to helping guppies fend off the worms naturally. When a tank does become infected, it is essential that you isolate the infected tank. The worms can be spread in a drop of water.

Picture from Diseases of Tropical Fishes by Herbert R. Axelrod

The fish vet, Doc Johnson, reports success with Potassium Permanganate. (See our treatment article on this compound.) Really sick guppies do not tolerate formalin very well, which makes Potassium Permanganate a better choice. However, we believe that PP does not completely eradicate gyrodactylus. It's probably a good first treatment in a course of treatment that subsequently uses another medication.

Trichlorfon (trade name Masoten) is an active ingredient in Fluke-Tabs and is reported to be effective against flukes by disrupting the fluke nervous system. See our treatment article on this drug.

Praziquantel under its Bayer trade names of Droncit or Drontal is reported by the Discus health expert, Jim Quarles, as being a recent form of treatment that is highly effective. See the Droncit/ Praziquantel entry in the treatment section of the Disease and Treatment Library.

Praziquantel is also recommended by the veternarian S. Dru Forrester, DVM.

Fluke-Tabs, which contain trichlorphon and mebenzadole, are reported to have high efficacy against flukes. See the mebenzadole treatment entry in the library. See the trichlorfon  (Masoten) entry in the library.

The following drugs are also mentioned in the veterinary literature as affecting both immature and mature skin flukes: clorsulon, closantel, diamphenethide, nitroxynil, xyclozanide, rafoxanide, triclabendazole. Closantel has recently got a lot of attention because it was shown to eradicate all phases of this fluke in sheep.

When treating guppies for this disease:

1.    Isolate the tank completely, as it can spread in a drop of water.
2.    Remove dead fish immediately.
3.    If you do not already use salt in your tanks, add 1 tablespoon (20g) of salt for each five gallons (19 L)  of water to aid osmoregulation of the fish.
4.    Follow the treatment program of the chosen drug.