Like many
things, I
have written
articles
that try to
encompass
broad areas
and make
them as
practical
and simple
as I can.
Part of this
is so that
everyone who
has engaged
this hobby
from all
walks-of-life
can
understand
the
material,
but another
part of this
stems from
the fact
that most of
this stuff
doesn't have
to be very
complicated.
So, in the
past, the
discussion
of
intestinal
and other
parasitic
worms in Koi
and Goldfish
has been
abbreviated
thusly:
"Worms and
intestinal
parasites of
Koi and
Goldfish are
usually not
severe
enemies. In
fact, your
Koi and
goldfish
could have
worms and
you would
probably
never know
it."
Which is
true,
however,
there are
many notable
exceptions.
And if you
were in a
group of
fish farmers
and breeders
who lost
almost all
your fish to
a tapeworm
like "Bothrio",
you would
immediately
challenge my
nonchalance.
Let's take
a look at
"worms" in
Koi and see
if we can
make heads
or tails of
it.
In the
first place,
I have
diagnosed
worms in Koi
and
Goldfish.
About once
every 3
months I
necropsy a
fish and
find this.
Half the
time, it's "Capillaria"
[from
petstore
Goldfish]
and the
other half
the time
it's Tapes,
probably "Bothrio"
from a
breeder
farm.
Worms:
What Are
They?
Worms can
be short, or
long, thin
or fat,
white or
red. They
are squiggly
tubular
living
organisms
and usually,
they're
USING a
host. In
other words,
they are
feeding on,
or living in
the Koi.
Regardless
of whether
we are
talking
about
Tapeworms,
Nematodes,
or whatever,
the vast
majority of
intestinal
parasites
depend on
transmission
through a
happenstance
copepod.
What is a
copepod you
may ask?
These
vaguely-referred
"copepods"
include all
your "fish
favorites":
Tiny,
naturally-occurring
fish
food-organisms
like
Cyclops,
amphipods,
isopods,
microcrustaceans,
insect
larvae, and
even annelid
worms like
Tubifex. The
folks with
the
healthiest
ponds will
probably
have a few
million of
these little
crunchies in
their ponds,
living among
the plants
or on the
pond bottom.
Back to
clinical
relevance:
As I
mentioned,
most of what
I have seen
in Koi and
Goldfish has
either been
a Tapeworm
or a
Capillaria
species.
Let's talk
about the
Tapes.
Another
word for
Tapeworm is
"Cestodes"
and they
infect Koi.
The Tapes
are rather
fat white
worms, and
they are
also
generally
flat.
Picture a
piece of
spaghetti
someone
stepped on.
Or a big fat
white
macaroni
noodle with
pointed ends
that someone
closed in a
book. All
the
Tapeworms
I've found
have been
balled up in
the
intestines
or less
commonly,
around the
internal
organs.
There are
a few, which
can pass
through a
Koi (using
it as a
temporary
host) while
some
cestodes
(tapes)
intend to
live
specifically
in the Koi.
In other
words,
depending on
the
tapeworm,
the Koi may
be an
intermediate
host, or a
definitive
host.
Probably
the worst of
the several
tapeworms of
Koi is
Bothriocephalus
acheilognathi
– which can
kill the
majority
among a
group of
infected
young Koi.
In other
infections,
tapeworms
can occupy
so much
space in the
peritoneal
space that
other organs
are crowded,
causing
weight loss,
and poor
reproductive
capacity.
The problem
with "Bothrio"
is that it
can take a
long time to
develop in
fish, so it
might be up
to two years
before you
could detect
it without
cutting a
fish open
for a
necropsy.
The Koi is
Bothrio's
final host.
"Bothrio's"
intermediate
host is a
copepod as
described
above.
Bothriocephalus
usually
kills its
host through
sheer bulk,
pressing on
organs and
blocking the
intestines.
Reproduction
of this worm
requires a
copepod or
annelid
(worm) host,
so folks
with natural
or mud
bottomed
ponds, which
foster the
growth of
balanced
ecosystems
complete
with
copepods and
insect
larvae could
give this
parasite
better
chances of
transmission.
To prevent
or eradicate
this worm,
any new
fish, and
new fish
being
brought in
from mud
ponds should
be dewormed
for this
parasite.
Otherwise,
an annual
deworming is
probably
adequate.
Other
Tapeworms of
Koi:
Ligula
intestinalis
is sometimes
a serious
pathogen of
Koi and
Goldfish.
Fish are not
the final
host for
Ligula
intestinalis.
This
particular
tapeworm
would prefer
to have the
fish (and
therefore
itself)
eaten by a
bird. I
don't think
I have ever
seen this
worm, the
reason I say
that is
because it
appears much
larger and
fatter than
the common,
smaller
Tapes I
encounter in
the fish.
Khawia
sinensis
Khawia
sinensis is
another
tapeworm of
Koi, which
causes
losses under
certain
conditions
of warmer
water,
higher
stocking
densities
and heavy
feeding in
mud ponds or
natural
ponds.
Khawia has
its
intermediate
host in an
annelid
(leech or
worm)
similar to
(but not
limited to)
Tubifex.
(Other
tubificids
like
Limnodrilus)
Like the
other
tapeworms,
Khawia kills
through
sheer bulk.
The "Cloverworms"
are closely
related to
Khawia, but
are
morphologically
distinct,
scientists
can tell
based on
where they
keep their
'bits'
whether they
are
Cloverworms
or Khawia,
but console
yourself
that they
all die the
same when
you feed
Praziquantel
or bathe the
host fish in
Praziquantel.
Other
cestodes
known to
infect Koi
for those
times when
you can't
get enough
big words:
Archigetes
Monobothrium
ssp
Atractolytocestus
Proteocephalus
Another
class of
worms is the
Nematode
class. These
worms are
not flat,
and many of
them are
exquisitely
small.
"Nematode"
is a VERY
broad word
which seems
to encompass
all the
other worm
parasites of
Koi.
Nematodes
don't want
fish for
their
retirement
home, very
much.
Basically,
they infect
fish
accidentally,
or on their
way to their
final host.
So they
might infect
a fish in
order to get
to a bird,
which would
be their
favorite
residence.
(Nematodes
are
essentially
and usually
all on their
way to a
bird or
mammal final
host)
We should
mention five
groups of
Nematode
worms that
can infect
Koi and
Goldfish. We
can take
them in
alphabetical
order.
Acanthocephala:
Acanthocephala
(Thorny
headed
worms) seem
to be
clinically
irrelevant
and require
an arthropod
host as
well. (Fish
is often a
final host)
I have never
seen these
infecting a
fish, even
incidentally,
so I doubt
their
importance.
Still, when
seen in
certain
species of
fish, their
"nose"
really
wrecks the
lining of
the
intestine
and can even
rupture the
gut. Let's
consider
them rare.
Ascarids:
Anisakis
is also
comparatively
rare.
Anisakis is
nothing if
it's not
persistent,
though. It
can be
transmitted
from one
fish muscle
tissue to
another
predator
fish. So, in
order to
finish its
life cycle,
it may
infect a
little
ocean-going
Mackerel,
which can be
used in
Goldfish
food. A
goldfish can
eat the fish
meat and be
infected
with
Anisakis.
Regardless
of the fish
host, if the
Anisakis
worm is not
happy there,
it can
encyst and
wait
patiently to
be eaten by
the fish or
animal it
really wants
to live in.
Salmon can
be infected
in the ocean
and carry
the parasite
to
freshwater
fish as it
migrates or
is eaten by
freshwater
fish. In
general,
Anisakis
wants to
live in
ocean-going
warm-blooded
fish eaters.
This is the
worm you
would get
from eating
Sushi or raw
fish, and
it's not
funny when
it happens.
It can
infect
people.
Dracunculoidea
Philometra
are in the
Dracunculoidean
group. They
are usually
blood red
and
associated
in or near a
blood
bearing
organ, such
as the gill,
or arteries.
They may be
in the
abdomen as
well. I have
not seen
these
parasites in
real life,
for all my
years of
doing this.
Trichurids:
Capillaria
– I have
seen this
one a pretty
good bit.
You identify
infections
with these
parasites by
fecal
impressions.
A simple
stool
sample,
compressed
between a
slide an
coverslip
and regarded
under 40-100
x
magnification
will show
the eggs of
this
parasite.
Positive
fecal
examinations
have the
typical
trichurid
egg: Oval in
shape, brown
in color,
with an
end-plug in
each end. In
many cases
you will see
both the
adult worms
and their
eggs
depending on
how you
collected
the sample.
If you have
collected
the sample
from a piece
of gut on
necropsy,
you will see
both life
phases. A
mammal is
the final,
intended
host.
Sometimes
they get
into fish
and can
mature and
reproduce
without ever
finding
their way to
a warm
blooded
mammal host.
Eggs shed in
the water
embryonate
and are
eaten by
fish. Since
Capillaria
does not use
a copepod,
worm or
insect
larvae host,
and the eggs
are the
infective
form, it's
life cycle
is
considered
"direct"
which makes
infections
more common
and easier
to sustain
in your pond
or aquarium.
Camallanoidea
Despite
the fact
that
Camallanus
delivers
live young
and not
eggs, this
nematode
requires an
arthropod /
copepod host
(like
Cyclops).
The adult
worms in the
intestinal
tract of
infected
fish will
produce and
retain eggs.
These eggs
develop into
juvenile
worms and
are shed.
The juvenile
worms must
be ingested
by copepods.
Inside the
copepod, the
worm matures
into an
infective
stage. The
fish then
eats the
copepod and
the
infection is
complete.
This worm is
found as an
adult in the
intestine of
the fish and
will even
protrude
from the
vent as a
reddish
tuft. It's
more common
in
farm-raised
livebearers,
such as
those from
Asia or
Florida.
This worm
damages the
intestine
and feeds on
the fishes'
blood,
causing
stress and
weakness. I
have not
seen this
worm in Koi
so far. I
have seen it
with some
frequency in
fish I've
necropsied
from pet
shops.
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