Henneguya koi

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Henneguya koi is a sporozoan parasite from the Myxosporidea family and is an ectoparasite of fish.

This species is especially seen in individual ornamental fish, but other species, such as Henneguya zschokkei are very important in cultured fish.

Life Cycle

The life cycle is indirect and involves an aquatic oligochaete worm as an intermediate host. Henneguya koi is an intracellular parasite and infection in the fish results in a spore-filled tissue cyst that displaced and disrupts tissue. The spores are released when the fish dies or if the cysts rupture.

The oval or sperm-shaped spore has a large sporoplasm and two polar capsules, each with an associated coiled filament.

Clinical Signs

Skin lesions may be visible as discrete, raised nodules, especially on the gills.

Fish may show signs of irritation such as flashing or rubbing.


Gill biopsies can be taken and examined under microscope to reveal the polar bodies of the spores in the target cells.

Giemsa staining may help in detecting the protozoa.


No treatment is available.

Affected fish should be isolated to prevent the spread of the disease.

Water quality should be monitored in all cases and stress to fish should be kept to a minimum.

Henneguya koi Learning Resources
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Test your knowledge using flashcard type questions
Ornamental Fish Q&A 15


Jepson, L. (2009) Exotic Animal Medicine Saunders

Roberts, H. (2009) Fundamentals of ornamental fish health John Wiley and Sons

Lewbart, G. (1998) Ornamental fish: self-assessment colour review Manson Publishing

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