On 9 Jun 1997 20:26:26 GMT, "Jolyon Claridge"
<Jac.Ullstrout at btinternet.com> wrote:
> I own a trout farm in the north west of England.
> Due to the low rainfall in recent years conditions of low water levels have
> caused an escalation in the number of cases of eye fluke in my stocks of
> rainbow trout. Does anyone have any information concerning: 1. Prevention
> of the condition. 2. Lifecycle of the parasite and whether it is
> particularly virulent under certain conditions. 3. Whether there is any
> cost effective method of treating fish which are already infected.
> Any help would be grately appreciated.
I assume you are talking about Diplostomum flexicaudum,
or a similar trematode?
If so, the life cycle begins with the adult worms
which occur in gull intestines. The worms are, as usual,
passed out in the feces. You aren't likely to be able to
control the gull population in your area. However, the
life cycle of D. flexicaudum includes a snail, which hosts
the sporocysts in its liver. It takes about six weeks for the
cercariae to begin emerging from the snail--and a single
snail can produce literally thousands of these a day.
The cercaria are what infest the trout and grow
into the metacercaria flukes that you see blinding the
trout and in some cases, destroying the eye lenses
entirely. It's not unusual to find over a hundred flukes
in a single trout eye lens.
You might want to check your ponds for the presence
of miracidium-infected snails. Since the snails are a
required for the life cycle, destroying an infected snail
population should take care of the problem for a while.
Tara K. Harper
PO Box 23-0107; Tigard, OR 97281-0107
e-mail: until at dontsendjunk_teleport.com
TO REPLY: remove "dontsendjunk_" from address