Management of Hexamita in Ornamental Cichlids
1
Ruth Francis-Floyd and Peggy Reed2
Hexamita is a flagellated protozoan found in the gastrointestinal tracts of
a variety of cold and warm water fish, including several species of Cichlids
which are popular aquarium pets. It can be a serious health problem in angel
fish and discus. Occasionally hexamita is found in healthy fish. Stress from
malnutrition, shipping, over-crowding, or poor water quality may lead to rapid
reproduction of the protozoan, resulting in disease. The genus hexamita was
formerly called "Octomitus" because of eight hair-like flagella which project
from the organism ( Figure
1 ). Three species of hexamita have been associated with disease in fish,
Hexamita salmonis , Hexamita truttae and Hexamita
intestinalis . It is unknown whether these species or new species which
have not yet been identified are responsible for disease in ornamental fish.
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Figure 1 .
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Transmission of hexamita
Hexamita is probably transmitted through the water from contaminated fecal
material. The flagellated stage makes its way to the lumen of the upper
intestine. There it swims freely in the intestinal and cecal fluids. The
organism may be present in small numbers under normal circumstances; however,
for disease to develop the organism must reproduce rapidly resulting in a
massive infestation. Generation time for the flagellated form is thought to be
24 hours.
Signs of hexamitiasis
Weak or stressed fishes seem to be most susceptible to heavy infestation.
Physical signs of hexamitiasis include weight loss, decreased activity and
refusal of food. Angel fish which are severely infected with hexamita may lie
horizontally on the surface of the water with the abdomen visibly distended.
Angel fish may remain in this condition for several days. These severely
infested fish often recover following treatment with metronidazole.
Infestations in adult breeding angel fish may be associated with decreased
hatchability of eggs or death of young fry.
Management of hexamita
Confirmation of hexamita infection is easily done by making a squash
preparation of the intestine and examining it with a light microscope at 200
and 400x. The flagellates move rapidly and erratically. They are most easily
seen in areas where the mucosa is broken. If the infestation is severe they
are numerous and easily found.
The recommended treatment for hexamita is metronidazole (Flagyl)
administered in a medicated food or, if the fish are not eating, in a bath
treatment. Metronidazole can be administered orally at a dosage of 50 mg/kg
body weight (or 10 mg/gm food) for 5 consecutive days. A recipe for a
gelatinized food is shown in Table 1 . The medication
can also be mixed with dry food using fish oil as a binding agent. One
teaspoon of metronidazole weighs approximately 2.25 gm; therefore 2 tsp.
should be added to each pound of food. The drug should be added when the
gelatinized mixture has cooled, but has not yet set. The medicated food can
then be frozen for storage. During the 5 day treatment regime feed only the
medicated food to the fish. If fish are not accustomed to a gelatinized food
they can be trained to accept the mixture by preparing the food without
medication and feeding it occasionally. Training should be done when fish are
healthy rather than waiting until they are sick. Sick fish do not eat well and
may completely refuse unfamiliar food.
If fish are already sick and off-feed metronidazole can be administered in
a bath at a concentration of 5 mg/l (18.9 mg/gallon) every other day for three
treatments. This treatment is effective but may not clear the organism from
the fishes' intestinal tract as well as the medicated food.
Since hexamita can be kept alive in laboratory media, it is assumed that it
is an inhabitant of aquaria where organic material has been allowed to
accumulate. Cleaning of gravel and filter materials will assist in eliminating
the organism from the environment. It may be advisable to periodically check
broodstock for subclinical hexamita infections. Even though the fish may not
be sick, low levels of the parasite may have an adverse effect on reproductive
performance or may flare up under conditions of stress. These subclinical
infections can be easily treated with a medicated feed before real problems
develop.
Summary
Hexamita is a flagellated protozoan that can be found in the intestine of
healthy and sick fish. It is of particular importance in angel fish and
discus. It can also cause problems in oscars and African cichlids, and other
fish. Stress, particularly caused by poor water quality or inadequate
nutrition, seems to be associated with increases in the number of flagellates
in the gut and development of clinical disease. Elimination of stress and
correction of husbandry will help correct an outbreak of hexamitiasis.
Metronidazole provided as a medicated feed or a bath is an effective treatment
and even severely affected fish often respond to therapy. Commercial producers
of ornamental cichlids should periodically check fish for hexamita infections
and treat any infected fish.
Tables
Table 1.
Table 1. Recipe for gelatinized
food which can be used to deliver oral medication to ornamental fish.
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Ingredients:
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6 oz
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Can of shrimp
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2 oz
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Frozen spinach
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1 oz
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Grated carrots
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3 tbsp
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Baby cereal (dry)
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2 tbsp
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Brewer's yeast
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2 oz
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Unflavored gelatin
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15 oz
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Water
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Optional ingredient:
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1 tsp
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Liquid vitamins
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Procedure:
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1.Blend 5 oz of water with shrimp,
spinach, carrots, baby cereal, brewer's yeast and vitamins.
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2.Boil remaining 10 oz of water.
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3.Add boiling water to gelatin in a
bowl.
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4.Cool until gelatin mixture is hot but
doesn't burn.
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5.Add contents of blender to partially
cooled gelatin mixture, mix thoroughly.
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6.Add medication to cooled mixture.
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7.Pour into flat pan and refrigerate.
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8.Cut gelatinized mixture into cubes for
feeding and store in freezer.
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Footnotes
1. This document is VM 67, one
of a series of the Department of Large Animal Clinical Sciences, Florida
Cooperative Extension Service, Institute of Food and Agricultural Sciences,
University of Florida. Printed January 1994. Please visit the FAIRS Web site
at http://hammock.ifas.ufl.edu.
2. Ruth Francis-Floyd,
assistant professor of aquaculture and fisheries; Peggy Reed, biological
scientist; Department of Large Animal Clinical Sciences and Department of
Fisheries and Aquaculture; Cooperative Extension Service, Institute of Food
and Agricultural Sciences, University of Florida, Gainesville, 32611.
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political opinions or affiliations. For information on obtaining other
extension publications, contact your county Cooperative Extension Service
office.
Florida Cooperative Extension Service / Institute of Food and Agricultural
Sciences / University of Florida / Larry R. Arrington, Interim Dean
Copyright Information
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Food and Agricultural Sciences (UF/IFAS) for the people of the State of
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and the people of the State of Florida. Permission is granted to others to use
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