a dangerous parasite
Written by Frank Prince-Iles
Even one parasite warrants immediate
The parasite Chilodonella is a major threat to fish health and finding
even one parasite warrants immediate treatment. Chilodonella is a
potentially dangerous parasite for two reasons. First, unlike many
parasites, it has a wide range of temperature tolerance and outbreaks
often occur at low temperatures when fish are least able to resist.
Secondly, despite is relative small size it, is potentially more dangerous
than Ich, because in the initial stages there are no readily visible signs
of its presence.
|Chilodonella at 400x magnification (phase
|Chilodonella as seen in a wet mount of a
Often by the time it becomes obvious that something is wrong there may
already be severe tissue damage. As with other parasites there is also the
risk of secondary infections resulting from lesions caused by the
parasite's feeding activity.
The clinical signs are the same as all other parasite infestations.
Heavy and laboured 'breathing' (judged by watching operculum movements),
flashing and rubbing, skin cloudiness caused by excess mucus, loss of
appetite and lethargy. At a later advanced stage (which may be too late
for treatment) fish often isolate themselves, sometimes near the water
surface or water return. They can also exhibit extreme lethargy with long
spells laying on the bottom with clamped fins.
It can be easily recognized in skin scrapes and gill biopsies from its
characteristic slow gliding movements, often turning in circles.
It has a flattened shape, heart-shaped with a notched end. There are
bands of cilia on the ventral (bottom) surface, just faintly visible in
the photomicrograph. They measure around 30 - 80 µm in length x 20 -60
µm width. - slightly smaller than skin-dwelling Trichodina.
Chilodonella is usually easy to treat with any proprietary parasite
treatment, malachite and formalin, potassium permanganate, copper or salt
baths. One treatment is usually sufficient
Article and pictures placed here with permission from the author,