Dactylogyrus spp. (Gill 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 also: Gyrodactylus spp.

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

Dactylogyrus affects a wide range of fish besides the guppy: Carp, bream, goldfish, stickleback, pike, trout.

The dactylogyrus worm has distinctive eye spots on one end and at the other end has one pair of anchors and 14 marginal hooks. Because this fluke has a free-swimming stage in its life-cycle, it needs the eye spots to find its prey.

The worm irritates the gill epithelium, leading to excessive mucus formation. The gill filaments become sticky, adhering to each other. The fish begins to rapidly breathe. If the infestation is really bad, the fish hangs near the surface and gasps, eventually asphyxiating.

Unlike the gyrodactylus, which is a livebearer, the dactylogyrus is an egg-layer. It scatters its eggs in the tank which hatch and reinfect fish in 1 to 5 days. Eggs that fall to the bottom of the tank hatch after a few hours.

The larvae (oncomiracidium) can swim and must find a host within 10 hours or they die.  They land on the fish, and crawl to the gills. Within three to eight days, depending on water conditions and temperature, they reach sexual maturity. The larvae are killed with the same chemical treatments as the adult.

Under winter conditions in ponds the eggs can lie dormant until the spring and hatch when the warm weather arrives. The eggs are quite tough and can survive many different types of medicated treatments. This makes dactylogyrus more difficult to treat than gyrodactylus, as we note below.

The dactylogyrus is twice as long as the gyrodactylus, at 1 to 2 mm.

Dactylogyrus can be found on the gills of the guppy or the body. The term gill worms is somewhat of a misnomer.

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

The following symptoms may selectively appear on guppies infected by gyrodactylus:
•    inflamed or dark skin, slimy, sometimes a grey film
•    fish rubs against hard objects (flashing)
•    rapid breathing
•    opaque mucus covering the gills
•    sluggishness
•    faded color
•    weight loss and emaciation
•    secondary bacterial or fungal infections may accompany
•    in acute infections, the guppy will be found gulping at the surface, followed shortly by sudden death

Causative Condition
Acute infections usually arise when water conditions in the tank decline. A infected fish introduced to the tank can also give rise to an epidemic. Like most parasites, the ideal conditions are a crowded tank with poor quality water.

Diagnosis
A microscope is required to see the tiny flukes on the guppy's skin. A gill rinse must be performed. The water sample from the gill rinse is placed in a glass vessel with a funnel-shaped bottom. The worms settle to the bottom and are removed with a small suction pipette. You can also remove gill arches from a guppy. You need to wait a couple of hours for the gill worms to leave the fill arches. A 200X microscope is sufficient to see the worms. The clinical signs listed in the above section are part of a diagnosis.

The red square shows the fluke in intimate association with the gills. From http://www.biosci.ohio-state.edu/~parasite/monogenea.html.

Prevention and Treatment
Prevention and treatment for dactylogyrus is the same as gyrodactylus with the exception that it is an egg layer. While gyrodactylus can be eradicated with one course of treatment, dactylogyrus needs to be treated over the five days of its maximum live span. Dactylogyrus that fall off the guppy can live on the bottom of the tank for four to eight days.

Bleaching an infested tank for 30 minutes, using a cup of bleach for a ten gallon tank, is recommended. (The bleach should not have any scent additives or other additives in it.) Bleach will destroy the silicon adhesive in the tank, so do not exceed the recommended concentration and length of treatment.