Common Names: Fluke
Gill flukes
Monogenean Trematodes

Salinity: Freshwater
Description: These are small parasitic wormlike creatures that under a microscopee resemble anything froma letter "T" to tiny tadpoles, and large sea slug like creatures. Large is a relative term for most species though, as on average they are less than 2mm long at full adult size. The flukes you will see externally on most fish look like tiny sea purses or shark eggs minus the adhesive stradns. Some are almost heart shaped, and other have been described as being a small flat slug with "bunny ears".

There are nearly as many species of fluke as there are fish, bit a few cause problems in aquaria across the board. External flukes are the most common , typically hermaphroditic, and are capable of producing huge numbers from one individual. In aquaria that of course means they can become a major pest.

The parasite usually attaches itself to the victim by a a minute clawed foot, sometimes with a sucking pad, and starts burrowing into the flesh. Sometimes they can be seen with the naked eye either sticking out of the fish or burrowed just beneath the skin on fish with more transparent skin. Gill flukes can burrow anywhere on the body, but their preferred place of attck is usually gill tissue. Here they feast on blood , soft tissue and sugars so easily accessable through the engorged gill membranes, often doing immense damage. They can be any colour, from transparednt to green,brown, red, and various hues of yellow.

Internal flukes are less common,except in coldwater systems where owners of pondfish may have regular problems with them. They burrow into the liver and gall bladder, obviously a very painful and dangerous parasite to have. Specimens of these kinds are the largest and have been known to be several inches long, and broad. Unfortunately most owners know nothing of the parasites until the fish shows symptoms of dropsy and dies from the damage inflicted by the worm consuming the gall bladder, kidneys and liver. Treatments for such infections are usually administered routinely on a yearly basis by the more conscientious pondkeeper.

Fish can be either the definitive host , or an intermediary host for various species of fluke. On average most fish in the world experience a minor infestation of flukes at some point, although those fish from near freezing waters are sometimes spared this uncomfortable indignity.

Other species of fluke specialise in colonising eye tissue, and the effect can be highly debilitating, diplostomum spathaceum is a species known to do this. They are among the most motile flukes and under close examination can sometimes be seen in the process of travelling to, penetrating, and then swimming within the eye itself. These infections are rare thanfully, but all captive fish from wild sources should be checked for them, particularly in areas where birds flock in some number, as the birds are part of the development of the parasite.

The parasite burden of external flukes anywhere other than on the gills is very light, but it is still in the fishkeepers interest to treat the problem as soon as possible, since once given a change to reproduce, they will do so in some number. Infections at the burrow site on a fish's anatomy are not uncommon, and sometimes large lesions will arise near the infection site.

Major carrier species include snails, frogs, and waterbirds. Flukes are present in one form or another in all wet environments across the world.

Some flukes/trematodes have developmental stages call cercarie, and these are among the most deadly forms, causing serious gastrointestinal disorders, organ failure, and debilitation in all species , fish and amphibians in particular may suffer huge cystic growths as they reproduce. The cysts may be of such size that a burst one will be life threatening to the fish. This also represents a stage of massive potential infection for any fish living within the confines of the same environment. There is also a significant risk to human health.

In terms of their range of effect on fish health, flukes range from almost insignificant, to truly dangerous, capable of decimating entire entire populations of fish. It depends very much on the species and its stage of development.

Needless to say , they should not be tolerated in an aquarium , and should be wiped out as quickly as possible.
Symptoms: Spots
Treatment: The range of techniques and treatments are large. Because many external or gill flukes are visible , if the fish only has the odd one or two, its quite possible to manually scrape them of the skin with a steralised scalpel and dispose of them. This becomes impractical with truly badly infested specimens, or in cases there the flukes themselves are barely visible. Gills are a very difficult area to remove parasites from manually , so rather than risk injury to the fish, turn to chemical cures.

For minor infections a simple salt bath for a few hours will kill the odd fluke, or indeed a freshwater bath for a marine fish. Flukes have real problems crossing the barriers of salinity, and direct contact with salt in freshwater species will often get them to loosen their footing. This is not always effective if the fluke is lodged under the skin, as the fish's very own slime layer may protect the fluke from exposure.

Common cures include formalin,trichlorfon, malachite green,menbendazole,methylene blue,and potassium permanganate usually administered in dips.

Internal species are much harder to treat, and to dispose of them , internal wormers need to be used. This applies equally to "lodged in" specimens, those that infect the eyes ,and the internal organs of the renal system. Its better to consult with a vet over these more aggressive infections, but most wormers for dealing with roundworm should kill flukes.

Comments: Treatment is easy enough, as long as you catch the correct stages of development in context with the correct medications, and in the right body area. Please, please be careful if dealing with cercarie stages of the rarer flukes, and consult with your doctor and vet simeultaneously. Most fluke infections are not immediately lethal, nor in most cases do they do a great deal of immediate damage, so take your time to choose the correct medication for your fish if it is of a sensitive species. Having saidd that, dont leave the worms there so long they have a chance to reproduce or cause some nasty secondary bacterial infections.

Eye flukes are the exception to the rule,must be tackled same day or faster if possible to prevent blindness.
Image Credit: ©
Submitted By: longhairedgit
Contributors: longhairedgit
History: View changes to this profile
Edit Profile: