Experimental induction of Sphaerospora renicola (Myxosporea) infection in common carp (Cyprinus carpio) by transmission of SB-protozoans


Molnar, K.; Kovacs Gayer, E.

Journal of Applied Ichthyology 2(2): 86-94

1986


This paper confirms in detail the preliminary report in Bull. Eur. Ass. Fish. Path. 4 1984 (4), 14-15 that the protozoa causing swimbladder inflammation in C. carpio are early development stages of S. renicola. Carp inoculated with infected swimbladder tissue developed renal sphaerosporosis. The parasites occurred in the swimbladder for about 2-3 weeks. However, UBO (unidentified blood organisms) of carp did not transform into Sphaerospora.

86
C.
Papaconstantinou
PAPACONSTANTINOU,
C.,
19836:
On
the
biology
of
Aspitrigla
cuculus
(L.
1758)
in
the
Saronikos
Gulf.
Thalassographica
6,49-75
(in
Greek).
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C.,
1984:
Age
and
growth
of
the
yellow
gurnard
(Trigla
lucerna,
L.
1758)
from
the
Thermaikos
Gulf
(Greece)
with
some
comments
on
its
biology.
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Res.
2,243-255.
PAULY,
D.,
1983:
Some
simple
methods
for
the
assessment
of
tropical
fish
stock.
FAO,
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Tech.
Paper
234.
PEYS,
J.
P.,
1960:
Etude
de
la
nourriture
de
quelques
poissons
demerseux
du
Golfe
du
Lion.
Red.
Tray.
stn.
Mar
Endoume
33
(20),
65-97.
TORTONESE,
E.,
1975:
Osteichthyes,
part
2,
vol
11
(In:
Fauna
d'Italia,
Ed.
Calderini,
Bologna,
Italy).
Author's
address:
C.
PAPACONSTANTINOU,
Ministry
of
Research
and
Technology.
National
Centre
for
Marine
Research.
Gr.-16604
Hellinikon
Athens
Greece
Veterinary
Medical
Research
Institute,
Hungarian
Academy
of
Sciences,
Budapest,
Hungary;
and
Cent-
ral
Veterinary
Institute,
Budapest,
Hungary
Experimental
induction
of
Sphaerospora
renicola
(Myxosporea)
infection
in
common
carp
(Cyprinus
carpio)
by
transmission
of
SB-protozoans
By
K.
MOLNAR
and
EVA
KOVACS-GAYER
Received
for
publication
January
18,
1985
Accepted
Sept.
23,1985
Summary
The
authors
have
experimental
evidence
that
the
protozoa
causing
the
swimbladder
inflammation
(SBI)
of
the
common
carp
(Cyprinus
carpio)
are
indentical
with
presporogonic
stages
of
Sphaerospora
renicola
Dykova
et
Lom,
1982
parasitizing
the
renal
tubules.
Homogenates
prepared
from
the
thickened
and
inflamed
swimbladder
of
naturally
infected
common
carp,
when
injected
into
the
abdominal
cavity
of
fish,
produced
renal
sphaerosporosis
in
the
infection-free
common
carp
if
the
homogenates
contained
the
parasites
described
by
KovAcs-GAYER
et
al.
(8).
By
intraperitoneal
injection,
the
Unidentified
Blood
Organisms
(UBOs)
living
in
the
blood
of
the
common
carp
were
transmissible
to
common
carp,
from
the
blood
of
which
they
were
demonstrable
for
a
long
time.
However,
they
were
not
transformed
into
Sphaerospora.
To
other
cyprinids
(gibel
carp,
silver
carp,
grass
carp,
tench,
roach)
neither
the
blood
stages
nor
the
swimbladder
stages
were
transmissible
from
the
common
carp.
Zusammenfassung
Experimentelle
Sphaerospora
renicola
(Myxosporea)
Infektion
beim
Karpfen
(Cyprinus
carpio)
durch
Obertragung
von
SB-Protozoen
Intraabdominale
Injektion
von
Homogenaten
aus
entziindeten
und
verdickten
Schwimmblasen
der
Karpfen
(mit
Prasenz
der
von
KovAcs-GAYER
et
al.
(1982)
beschriebenen
Parasiten)
verursachten
Nieren-Sphaerospore.
Die
im
Blut
der
Karpfen
vorkommenden
UBO
(unidentified
blood
organisms)
waren
zwar
experimentell
auf
gesunde
Karpfen
ubertragbar,
eine
Umwandlung
in
Sphaerosporen
konnte
aber
nicht
beobachtet
werden.
Weder
die
im
Blut
noch
die
in
Schwimmblasen
der
Karpfen
existierenden
Parasiten
konnten
auf
andere
Cypriniden
(Silberkarauschen,
Graskarpfen,
Silberkarpfen,
Schleie,
Plotzen)
ubertragen
werden.
U.S.
Copyright
Clearance
Center
Code
Statement:
0175-8659/86/0202-0086
$
02.50/0
J.
Appl.
Ichthyol.
2
(1986)
86-94
©
1986
Verlag
Paul
Parey,
Hamburg
und
Berlin
ISSN
0175-8659
Experimental
induction
of
Sphaerospora
renicola
infection
in
common
carp
87
Die
Ergebnisse
dieser
Arbeit
zeigen,
dais
die
Schwimmblasenentzundung
der
Karpfen
durch
Sphaerospora
renicola
(DYKOVA
and
Lord
1982)
induziert
werden
kann.
Résumé
Introduction
experimentale
de
l'infection
Sphaerospora
renicola
(Myxosporea)
chez
la
carpe
commune
(Cyprinus
carpio)
par
transmission
de
SB-protozoaires
Les
auteurs
ont
demontre
experimentalement
que
les
protozoaires
(SBP)
causant
l'inflammation
de
la
vessie
natatoire
de
la
carpe
commune
(Cyprinus
carpio)
sont
identiques
aux
stades
presporogoniques
de
Sphaerospora
renicola
DYKOVA
et
Loaf,
1982,
parasite
vivant
dans
les
tubulures
renales.
Des
prepara-
tions
homogenes
faites
a
partir
de
la
vessie
natatoire
enflammee
et
ay
ant
augmente
de
volume
de
la
carpe
infectee
par
voie
naturelle
ont
cause,
lorsque
injectes
dans
la
cavite
abdominale
du
poisson,
une
shaeros-
porose
renale
chez
la
carpe
non
infectee
si
les
preparations
contenaient
les
parasites
decrits
par
KovAcs-
GAYER
et
al.
Les
U.B.O.,
organismes
du
sang
non
identifies,
vivant
dans
le
sang
de
la
carpe
commune,
ont
pu
etre
transmis
a
la
carpe
commune
par
injection
dans
le
peritoine
et
ont
pu
etre
longtemps
constates
dans
le
sang
de
celle-ci.
Its
ne
se
sont
cependant
pas
transformes
en
Sphaerospora.
Ni
les
stades
du
sang,
ni
ceux
de
la
vessie
natatoire
de
la
carpe
commune
n'ont
pu
etre
transmis
a
d'autres
cyprinides
(Carassius
auratus
gibelio,
Ctenopharyngodon
idella,
Hypophthalmichthys
molitrix,
Tinca
tinca,
Rutilus
rutilus).
Introduction
In
a
short
communication
Molnar
(15)
reported
that
the
protozoan
developmental
stages
parasitizing
the
swimbladder
of
the
common
carp
(Cyprinus
carpio)
and
described
by
KovAcs-GAYER
et
al.
(8),
KoRTING
(9)
and
CSABA
et
al.
(3)
can
be
transmitted
experimen-
tally
into
infection-free
fish,
in
the
renal
tubules
of
which
the
protozoans
develop
into
the
spores
of
Sphaerospora
renicola
Dykova
et
Lom,
1982.
In
the
present
paper
the
results
of
those
repeated
and
expanded
experiments
are
reported
which
have
produced
many-sided
evidence
on
the
identity
of
SB-protozoans
causing
swimbladder
inflammation
(SBI)
of
the
common
carp
with
an
early
developmental
stage
of
Sphaerospora
renicola,
and
which
seem
to
contradict
the
postulated
Sphaerospora
renicola-
nature
of
blood
protozoans
described
by
CSABA
(2)
and
designated
by
LOM
and
DYKOVA
(11)
as
UBO
(Unidentified
Blood
Organism).
Materials
and
methods
The
experiments
were
conducted
in
1982,
1983
and
1984
from
the
beginning
of
July
up
to
mid-September,
in
the
period
when
swimbladder
inflammation
usually
occurs.
In
1982,
common
carp
fry
obtained
from
an
SBI-free
stock,
while
in
1983
and
1984
common
carp
artificially
hatched
in
1983
and
reared
under
parasite-free
conditions
were
used
in
the
experi-
ments.
When
hatched
from
the
eggs,
the
fry
were
fed
on
brine
shrimp,
then
on
a
dried,
synthetic
food,
and
were
kept
in
good-quality
drinking
water.
These
fish
remained
parasite-
free
throughout
and
contained
no
specific
pathogenic
germs
either.
Three
different
types
of
experiments
were
conducted.
In
the
first
type
experiments
(1,
2,
3,
4,
5,
7,
8,
9,
10)
common
carp
fry
diseased
in
acute
SBI
and
obtained
from
a
pond
farm
were
used
as
donors.
The
affected
swimbladders
of
the
fish
were
divided
into
three
parts:
one
part
was
fixed
for
histological
examination;
from
the
second
part
impression
smears
were
prepared,
fixed
with
methanol
and
stained
according
to
Giemsa;
tissues
of
the
third
part
of
the
swimbladder
were
lacerated
with
a
dissecting
needle
in
0.65
%
NaCI
solution
and
filtered
through
a
fine
sieve;
0.1-0.3
ml
of
the
obtained
filtrate
was
injected
with
a
syringe
into
the
abdominal
cavity
of
the
experimental
common
carp
fry
of
1-4
g
body
mass
before
being
checked
for
positivity.
In
the
second
type
of
experiments
(experiments
11)
homogenates
were
prepared
in
0.65%
NaCl
solution
from
the
kidneys
of
fish
showing
lesions
characteristic
of
more
88
K.
Molnar
and
Eva
Kovacs-Gayer
chronic
SBI,
already
free
from
SB-protozoans
but
containing
sporogonic
developmental
stages
of
Sphaerospora
renicola
in
their
renal
tubules,
and
these
homogenates
were
injected
into
the
abdominal
cavity
of
experimental
fish.
In
the
third
type
of
experiments
(experiment
6,
12)
0.1-0.2
ml
blood
of
fish
free
from
SB-
protozoans
and
renal
sphaerosporosis
but
containing
UBOs
was
injected
into
the
abdominal
cavity
of
infection-free
common
carp.
In
1984
our
experiments
were
extended,
in
addition
to
the
common
carp,
to
other
carps
(gibel
carp,
grass
carp,
silver
carp,
tench,
roach);
also
these
were
injected
intraperitoneally
with
parasite-containing
blood
and
swimbladder
and
kidney
homogenates
of
common
carp
origin.
The
fish
kept
at
20°
C
in
aquarium
and
were
killed,
depending
on
the
type
of
experiment,
on
post-infection
days
2-42.
After
the
native
examination
(squash
preparation,
blood
drop
examination)
impression
smears,
histological
preparations
and
blood
smears
were
prepared.
From
fish
inoculated
only
with
blood
parasites
(UBOs)
blood
samples
were
taken
regularly
also
before
the
extermination
of
the
fish.
Results
Observations
CSABA
et
al.
(3)
have
reported
that
swimbladder
protozoans
(SBP)
can
always
be
demon-
strated
in
common
carp
fry
diseased
in
acute
SBI.
In
the
present
experiments
the
disease
was
found
to
occur
also
in
two-summer
common
carp,
in
the
swimbladder
of
which
SB
proto-
zoans
occasionally
appeared
already
in
the
end
of
June.
In
fry,
infection
was
in
correlation
with
the
age
of
the
fish.
In
fish
hatched
earlier,
infection
appeared
already
in
the
beginning
of
July,
in
stocks
hatched
in
May
the
disease
was
demonstrated
mostly
in
the
end
of
July
and
in
the
beginning
of
August.
In
the
end
of
August
and
in
September
acute
SBI
occurred
only
in
stocks
that
had
been
hatched
late.
Within
a
stock,
infection
passed
off
synchronously,
and
3
weeks
after
the
appearance
of
the
first
symptoms
SB-protozoans
were
found
only
occasionally.
Because
of
this
fact,
for
the
experiments
performed
at
different
times
donors
had
to
be
selected
always
from
new
fish
stocks.
In
donor
fish
with
acute
SBI
lesions
most
of
the
SB-protozoans
consisted
of
primary
and
secondary
cells;
however,
in
fish
exhibiting
pronounced
symptoms,
triple
forms
corres-
ponding
to
tertiary
cells
were
abundant.
Experiments
In
1982
only
one
experiment
was
carried
out.
Experiment
1
The
swimbladder
homogenate
of
a
common
carp
affected
with
SBI
was
injected
into
the
abdominal
cavity
of
four
common
carp
fry,
each
weighing
10-12
g,
derived
from
an
SBI-free
stock.
Twenty-six
fish
served
as
control.
Large
numbers
of
SB-protozoans
were
found
in
the
impression
smears
prepared
of
the
swimbladder
of
the
donor
fish.
One
inoculated
fish
died
during
the
experiment.
Of
the
remaining
three
fish
one
proved
to
be
infection-free,
whereas
in
the
renal
tubules
of
the
remaining
two
S.
renicola
spores
and
developmental
stages
were
found.
(It
should
be
mentioned
here
that
both
in
the
present
and
in
further
experiments
the
developmental
stages
found
in
the
renal
tubules
were
exclusively
in
the
sporogonic
stage,
in
accordance
with
what
is
seen
in
natural
cases,
i.e.
one
pansporoblast
contained
two
sporo-
blasts
representing
different
degrees
of
development).
No
Sphaerospora
was
demonstrated
in
the
controls;
however,
in
part
of
the
fish
the
blood
contained
UBOs.
In
1983
five
experiments
were
conducted
in
which
positively
parasite-free
fish
were
used.
Experimental
induction
of
Sphaerospora
renicola
infection
in
common
carp
89
Experiment
2
On
August
4,
3
fish,
each
weighing
3
g,
were
inoculated
into
the
abdominal
cavity
with
swimbladder
homogenate.
In
the
swimbladder
impression
smears
and
in
the
histological
preparation
of
the
donor
fish
the
parasite
stages
described
by
KOVACS-GAYER
et
al.
(8)
were
demonstrated.
The
fish
were
killed
on
August
15.
The
kidneys
of
two
fish
contained
numer-
ous
S.
renicola
spores
and
developmental
stages
(One
of
these
fish
had
numerous
UBOs
in
the
blood).
The
kidneys
of
the
third
fish
contained
only
developmental
stages.
Experiment
3
This
experiment
was
started
on
August
17.
Swimbladder
homogenates
of
8
fish
showing
the
symptoms
of
SBI
were
used
for
infection.
Of
the
donors
showing
a
slightly
more
chronic
form
of
SBI,
the
swimbladder
impression
smear
of
only
one
fish
contained
SBPs.
No
histological
samples
were
taken.
On
the
other
hand,
UBOs
were
demonstrable
in
the
blood
of
all
donors.
The
homogenate
was
injected
into
the
abdominal
cavity
of
14
fish,
each
weighing
1-4
g.
These
fish
were
killed
at
different
times.
In
the
fish
killed
on
August
25
(the
8th
day
of
the
experiment)
numerous
Sphaerospora
developmental
stages
were
present
in
the
kidney.
In
the
kidney
of
fish
killed
on
August
26
some
spores
had
also
appeared
in
addition
to
the
developmental
stages,
and
in
both
fish
killed
on
August
29
numerous
spores
and
developmental
stages
were
present.
Infection
was
less
severe
in
fish
killed
on
September
2,
and
its
severity
had
decreased
further
in
fish
examined
on
September
12.
It
should
be
mentioned
that
at
both
of
the
latter
examinations
the
number
of
spores
and
developmental
stages
was
nearly
the
same,
and
at
the
last
examination
(September
12)
numerous
UBOs
were
demonstrable
in
the
blood
of
the
fish.
The
remaining
4
fish
were
killed
on
September
19.
At
that
time
the
kidneys
of
two
fish
were
already
negative,
while
in
the
other
two
low-degree
Sphaerospora
infection
was
observed.
In
the
latter
fish
there
still
always
were
sporogonic
developmental
stages
in
addition
to
the
spores.
Large
numbers
of
UBOs
were
present
in
the
blood
of
both
the
Sphaerospora-negative
and
the
Sphaerospora-positive
fish.
During
the
experiment
slight
opacification
of
the
swimbladder
was
observed
only
one
occasion;
how-
ever,
parasites
other
than
UBOs
were
found
in
the
swimbladder
neither
in
that
case.
Experiment
4
This
experiment
was
started
on
August
18.
At
this
time,
swimbladder
homogenate
from
8
fish
showing
slightly
more
chronic
SBI
was
inoculated
into
the
abdominal
cavity
of
12
parasite-free
fish.
No
parasites
were
demonstrable
in
impression
smears
prepared
from
the
swimbladder
of
donor
fish
and
the
swimbladders
were
negative
also
histologically.
The
fish
were
killed
parallel
with
those
of
Experiment
3.
Their
organs
proved
to
be
negative
in
all
cases.
Experiment
5
Five
infection-free
fish
were
inoculated
with
swimbladder
homogenate
on
August
31.
No
SBP
were
found
in
impression
smears
made
of
the
swimbladder
of
donor
fish.
The
fish,
killed
on
post-infection
(PI)
days
11
and
20,
proved
to
be
free
from
infection.
Experiment
6
During
the
last
experiment
conducted
in
the
autumn
of
1983,10
parasite-free
common
carp
fry
were
inoculated
into
the
abdominal
cavity
with
blood
from
donor
fish
which
contained
1-4
UBOs
per
visual
field
when
examined
in
400-fold
magnification
by
microscopy.
The
inoculated
fish
were
killed,
whenever
possible,
at
3-day
intervals.
No
parasites
were
found
in
the
fish
up
to
the
12th
day
postinfection.
On
the
14th
day
PI
a
few
UBOs
were
seen
in
the
90
K.
Molnar
and
Eva
Kovacs-Gayer
blood
smears
and
in
native
preparations
of
kidney
and
swimbladder
capillaries.
Infection
by
UBOs
aggravated
up
to
the
30th
day
when
4-6
parasites
per
visual
field
were
found
in
the
blood.
The
experiment
was
concluded
at
that
time.
During
the
experiment
no
parasites
other
than
UBOs
were
found
in
the
kidney
and
swimbladder.
(For
the
sake
of
completeness
it
should
be
mentioned
that
we
had
already
conducted
similar
experiments
with
similar
results
several
times.
However,
the
interpretation
of
these
experiments
was
hindered
by
the
lack
of
undoubtedly
parasite-free
fish,
although
appropriate
controls
were
available.)
In
1984,
experiments
with
SB-parasites
were
performed
in
July—August,
when
acute
cases
still
occurred.
In
this
year,
the
swimbladders
of
all
donors
used
in
the
experiment
proved
to
be
infected
according
to
the
subsequent
examination
of
impression
smears
and
histological
preparations
(Fig.
1).
Experiment
7
Swimbladder
homogenate
from
two
common
carp
fry
showing
an
early
stage
of
SBI
was
inoculated
into
2
infection-free
common
carp
fry
and
one
grass
carp
(Ctenophmyngodon
idella).
In
the
donors
mostly
early
SBP
stages
occurred.
The
kidneys
of
both
common
carp
killed
on
day
11
contained
numerous
Sphaerospora
spores
and
developmental
stages;
how-
ever,
their
swimbladder
and
blood
proved
to
be
negative.
The
grasscarp
remained
free
from
Sphaerospora
infection.
Experiment
8
Swimbladder
homogenate
of
2
twosummer
common
carp
were
used
for
infection.
The
swimbladders,
as
in
the
further
experiments,
contained
the
triple
forms
of
SBP
in
large
numbers.
The
homogenate
was
inoculated
into
the
abdominal
cavity
of
7
common
carp.
In
the
kidneys
of
the
two
fish
killed
on
PI
day
5
young
sporogonic
Sphaerospora
stages
were
demonstrated,
whereas
in
those
of
fish
killed
on
PI
days
9,11
and
14
both
Sphaerospora
developmental
stages
and
spores
were
found.
No
developmental
stages
were
seen
in
the
renal
tubules
of
fish
killed
on
PI
days
33
and
36,
and
spores
occurred
only
occasionally.
UBOs
were
observed
only
in
fish
killed
on
PI
day
36.
1:40%
9'
4,
t
'we
lik
A•
.
1
1
l
p
4
4.6
.
1;
1
.74
-
p
.
4
1
Arte
Pat
Po'
Fig.
I.
SBP
developmental
stages
in
a
histological
section
made
from
the
swimbladder
wall
of
a
donor
common
carp.
In
the
parasite
mass
representing
one
primary
cell
each,
infective
tertiary
forms
(arrow)
are
also
seen.
H.
and
E.,
x
800
Experimental
induction
of
Sphaerospora
renicola
infection
in
common
carp
91
7.11011r
#
Nir
di
ji
b
P
k'
1
411
410
lb
%AP'
ab
're
lli
baja
la
e=1:
Fig.
2
Young
Sphaerospora
renicola
stages
in
the
renal
tubule
3
days
after
infection.
H.
and
E.,
x
800
Experiment
9
Four
gibel
carp
(Carassius
auratus
gibelio),
and
one
silver
carp
(Hypophthalmichthys
moli-
trix),
roach
(Rutilus
rutilus)
and
common
carp
were
inoculated
with
swimbladder
homoge-
nate
of
an
SBP-infected
donor.
Of
the
fish
killed
on
PI
day
11
only
the
common
carp
had
Sphaerospora
stages
in
the
kidney.
Experiment
10
Twelve
common
carp
and
two
grasscarp,
silver
carp,
and
gibel
carp
each
were
inoculated
into
the
abdominal
cavity
with
swimbladder
homogenate
from
an
SBP-infected
donor.
The
common
carp
were
killed
at
one-day
intervals.
The
first
Sphaerospora
developmental
stages
were
observed
on
PI
day
3
(Fig.
2),
and
the
first
spores
on
PI
day
7
(Fig.
3).
Between
PI
days
4
and
12
the
kidneys
of
all
common
carp
but
two
proved
to
be
Sphaerospora-positive.
The
kidney
of
the
fish
surviving
up
to
day
36
was
negative;
however,
the
blood
of
this
fish
contained
UBOs.
The
silver
carp,
grass
carp
and
gibel
carp
killed
on
PI
day
13
were
negative.
Experiment
11
Ten
common
carp
and
2
gibel
carp
were
inoculated
with
kidney
homogenate
from
common
carp
infected
with
Sphaerospora
renicola.
The
kidneys
of
fish
killed
on
PI
day
11
were
free
from
Sphaerospora.
Experiment
12
Five
common
carp,
grasscarp,
silver
carp,
gibel
carp
and
tenches
(Tinca
tin
ca)
each
were
inoculated
into
the
abdominal
cavity
with
UBO-containing
blood
from
severely
infected
common
carp;
the
blood
was
diluted
in
Alsever's
solution.
During
the
42-day
experimental
period
the
blood
of
the
fish
was
examined
at
two-day
intervals.
The
blood
of
all
common
carp
became
infected.
First
UBOs
appeared
on
day
10,
and
infection
was
demonstrable
even
on
day
42.
However,
no
UBOs
appeared
in
the
blood
of
grass
carp,
silver
carp,
gibel
carp
and
tenches.
In
the
kidney
and
swimbladder
of
common
carp
killed
between
day
14
and
42
no
Sphaerospora
stages
were
seen.
a
.
an
is'
1P4s. d
p
92
--
A&
K.
Molnar
and
Eva
Kovacs-Gayer
Facim
el
IF
0
4i
1.
aa
r
4
.
11
`4.
4
41610
alt
o
*
411P*
Fig.
3
Spores
(arrow)
and
developmental
stages
in
the
renal
tubule
7
days
after
infection.
H.
and
E.,
x
800
Discussion
The
present
results
support
the
findings
of
KOVACS-GAYER
et
al.
(8),
KoRTING
(9)
and
CSABA
et
al
(3),
and
furnish
evidence
that
the
Myxozoa-stages
(SBP)
developing
in
the
swimbladder
wall
of
the
common
carp
correspond
to
the
early,
presporogonic
developmen-
tal
stages
of
S.
renicola
parasitizing
in
the
lumen
of
renal
tubules.
In
all
cases
when
the
parasites
were
demonstrated
in
the
impressions
mears
or
histological
preparations,
the
swimbladder
homogenate inoculated
into
the
abdominal
cavity
of
infection-free
carp
resulted
in
the
development
of
Sphaerospora
stages
in
the
kidney.
Sphaerospora
developmen-
tal
stages
causing
SBI
of
the
common
carp
are
first
demonstrable
simultaneously
with
the
onset
of
clinical
symptoms.
The
parasites
are
present
in
the
swimbladder
for
about
2
-
3
weeks;
thus,
under
the
climatic
conditions
of
Hungary,
they
are
expected
to
appear
in
one-
summer
fish
in
the
end
of
June
and
in
the
beginning
of
July,
while
in
4
-
6
weeks
old
fry,
disregarding
the
rarely
occurring
late
infections,
in
July
and
in
the
beginning
of
August.
In
the
light
of
the
above
facts,
the
partial
failure
of
the
experiments
conducted
in
1983
is
fully
understandable;
this
failure
was
corrected
in
1984.
In
cases
when
SBP
were
present
in
the
swimbladder,
the
final,
so-called
triple,
forms
of
the
parasites
inoculated
into
the
abdominal
cavity
developed
into
sporogonic
stages
of
S.
renicola
in
the
renal
tubules;
infection
developed
also
if
the
donors
contained
mostly
young
SBP
stages.
On
the
other
hand,
in
cases
when
the
parasites
had
already
left
the
swimbladder
and
only
chronic
forms
of
SBI
were
diagnosed
(see
Experiments
4
and
5),
for
the
lack
of
infective
stages
the
swimbladder
homogenate
inoculated
into
the
abdominal
cavity
produced
no
sphaerosporosis.
In
our
experiments,
renal
sphaerosporosis
was
demonstrable
already
3
days
after
infec-
tion,
and
by
PI
days
7-9
the
first
spores
had
appeared.
In
the
subsequent
period,
the
spore/
pansporoblast
ratio
kept
increasing;
however,
no
periodicity
could
be
observed
in
their
development
since
developmental
stages
were
demonstrable,
together
with
spores,
even
a
month
later.
At
the
same
time,
the
degree
of
infection
lessened
gradually
from
the
2nd
week,
and
by
5
weeks
PI
infection
practically
ceased
to
exist.
The
asynchronous
formation
of
spores,
i.
e.
the
prolongation
of
the
practically
8-day
Experimental
induction
of
Sphaerospora
renicola
infection
in
common
carp
93
period
of
sporogony
to
4
to
5
weeks
can
probably
be
explained
by
the
fact
that
the
develop-
mental
stages
inoculated
into
the
abdominal
cavity
reached
the
kidney
at
different
times.
However,
the
above
experiments
failed
to
elucidate
the
mode
by
which
the
kidney
became
infected.
It
is
not
clear
yet
how
the
developmental
stages
injected
into
the
abdominal
cavity
managed
to
get
into
the
renal
tubules.
It
seemed
an
obvious
hypothesis
that
swimblad-
der
parasites
were
somehow
transformed
into
motile
UBOs
which
were
transported
to
the
renal
tubules
by
the
blood
stream.
In
fish
inoculated
with
swimbladder
homogenate
UBOs
did
actually
appear;
however,
their
role
in
producing
renal
sphaerosporosis
has
not
been
confirmed
by
experiments
6
and
12.
UBOs
can
be
transmitted
easily
into
uninfected
com-
mon
carp
with
the
infected
blood,
but
in
the
latter
they
cause
neither
renal
sphaerosporosis
nor
SBI.
A
possible
explanation
for
the
fact
that
UBOs
still
appeared
in
the
blood
of
fish
inoculated
with
swimbladder
homogenate
is
that
these
parasites
had
been
present
in
blood
vessels
of
the
swimbladder
of
donor
fish.
As
regards
the
mode
of
infection
of
renal
tubules,
the
most
probable
possibility
is
that
the
triple
SBP
forms
that
developed
in
the
swimbladder
are
transported
by
the
blood
stream
to
the
renal
glomeruli
and
from
there
to
the
renal
tubules,
where
they
are
transformed
into
pansporoblasts
and
produce
two
S.
renicola
spores
each.
We
consider
impossible
the
hypothesis
of
LOM
and
DYKOVA
(10)
and
DYKOVA
and
Loan
(5)
according
to
which
S.
re-
nicola
might
have
intracellular
developmental
stages
in
the
epithelium
of
the
renal
tubules.
The
parasite
forms
observed
by
them
were
obviously
developmental
stages
of
Mitraspora
cyprini
or
Hoferellus
cyprini,
occurring
as
co-infecting
agents.
As
regard
the
host-specificity,
no
final
conclusions
can
be
drawn
from
the
experiments
performed.
The
results
obtained
so
far
indicate
that
both
the
S.
renicola
stages
and
the
UBOs
are
specific
common
carp
parasites
which
could
not
be
transmitted
even
to
the
genetically
closely
related
gibel
carp.
Apart
from
proving
the
aetiological
relationship
of
SBI
and
renal
sphaerosporosis,
the
above
experiments
have
also
theoretical
significance.
In
the
literature
(13,
16,
17)
it
is
an
established
fact
that
the
germinative
sporoplasm
released
from
the
spore
multiplies
and
produces
spores
at
the
site
of
its
colonization
in
the
host.
The
present
results
have
confirmed
our
earlier
observation
(14),
differing
from
reports
known
from
the
literature,
and
agree
also
with
the
similar
opinion
of
LoM
et
al.
(12)
that
only
the
sporogonic
stage
of
the
development
of
S.
renicola
takes
place
in
the
renal
tubules,
while
intensive
multiplication
occurs
in
the
swimbladder.
This
means
that
in
certain
Myxozoa
the
well-defined
developmental
periods
of
the
given
parasite
take
place
in
host
organs
differing
in
respect
of
location
and
structure.
Experiments
similar
to
ours
were
conducted
by
CLIFTON-HADLEY
et
al.
(1)
and
D'SILVA
et
al.
(4)
who
succeeded
in
transmitting,
by
intraperitoneal
inoculation,
the
causative
agent
of
proliferative
kidney
disease
(PKD),
the
so-called
PKX
organism,
into
uninfected
trouts
in
which
PKD
developed.
However,
these
authors
did
not
know
that
the
PKX
organism
was
probably
a
Myxosporea
protozoon.
FERGUSSON
(6)
and
KENT
and
HEDRICK
(7)
arrived
at
the
conclusion
that
the
PKX
organisms
living
in
the
renal
interstitium
of
salmons
were
the
developmental
stages
of
some
Myxosporea
(presumably
a
Sphaerospora
or
Mitraspora
species)
parasitizing
the
renal
tubules.
The
vegetative
and
sporogonic
stages
of
these
para-
sites
develop
also
in
different
locations
even
if
in
this
case
the
different
location
means
the
interstitial
and
tubular
part
of
the
very
same
organ.
However,
the
experiments
conducted
by
CLIFTON-HADLEY
et
al.
(1)
and
D'SILVA
et
al.
(4)
cannot
be
considered
fully
analogous
with
those
performed
by
us.
The
above-cited
authors
produced
the
same
phase
of
PKD
by
transmitting
the
causative
agent,
while
we
were
unable
to
produce
SBI,
only
the
subse-
quently
developing
renal
sphaerosporosis.
Also,
we
failed
in
transmitting
the
sporogonic
stages
present
in
the
renal
tubules.
However,
this
fact
is
not
at
all
surprising
since
the
coelozoic
forms
are
unable
to
migrate.
The
role
of
the
blood-parasite
UBOs
is
still
doubtful;
however,
based
upon
the
present
experiments,
despite
their
undoubted
similarity
to
SBP,
they
cannot
be
regarded
as
developmental
stages
of
S.
renicola.
94
K.
Molncir
and
Eva
Kovacs-Gayer
Acknowledgements
The
authors
express
their
thanks
to
Dr.
LAszi.o
REKtsi,
Dr.
GYoRGY
CSABA
and
Dr.
JOZSEF
SZAKOLC-
ZAI
(Central
Veterinary
Institute)
for
the
diagnosis
of
swimbladder
inflammation
and
for
critical
discus-
sions,
and
Dr.
S.
S.
DESSER
for
his
comments
on
the
manuscript.
References
1.
CLIFTON-HADLEY,
R.
S.;
RICHARDS,
R.
H.;
BUCKE,
J.
1984:
Experimental
transmission
of
pro-
liferative
kidney
disease:
Preliminary
report.
Vet.
Record.
114,
90.
2.
CSABA,
G.,
1976:
An
unidentifiable
extracellular
sporozoan
parasite
from
the
blood
of
the
carp.
Parasitol.
Hung.
9,21-24.
3.
CSABA,
G.;
KOVACS-GAYER,
P..;
BEictsi,
L.;
BUCSEK,
M.;
SZAKOLCZAI,
J.;
MOLNAR,
K.,
1984:
Studies
into
the
possible
protozoan
aetiology
of
swimbladder
inflammation
in
the
carp
fry.
J.
Fish
Dis.
7,39-56.
4.
D'SiLvA,
J.;
MULCAHY,
M.
F.;
DE
KINKELIN,
P.,
1984:
Experimental
transmission
of
proliferative
kidney
disease
in
rainbow
trout,
Salmo
gairdneri
Richardson.
J.
Fish
Dis.
7,235-239.
5.
DYKOVA,
I.;
Lom,
J.,
1982:
Sphaerospora
renicola
n.
sp.,
a
Myxosporean
from
carp
kidney,
and
its
pathogenicity.
Z.
Parasitenkd.
68,259-268.
6.
FERGUSON,
H.,
1984:
Proliferative
kidney
disease
in
Northern
Ireland.
Epidemiology
and
Con-
trol.
(In:
Program
and
Abstract
of
S.
F.
Snieszko
commemorative
fish
disease
workshop.
Little
Rock,
Arkansas,
p.
6.)
7.
KENT,
M.;
HEDRICK,
R.
P.,
1984:
The
protozoan
causing
Proliferative
Kidney
Disease
(PKD)
may
be
a
member
of
the
phylum
Myxozoa.
Epidemiology
and
Control.
(In:
Program
and
Abstract
of
S.
F.
Snieszko
commemorative
fish
disease
workshop.
Little
Rock,
Arkansas,
p.
5.)
8.
KOVACS-GAYER,
E.;
CSABA,
G.;
Btxtsi,
L.;
BUCSEK,
M.;
SZAKOLCZAI,
J.;
MOLNAR,
K.;
1982:
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Eur.
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2,22-24.
9.
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W.,
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Protozoan
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Z.
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146-149.)
11.
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DvicovA,
I.,
1984:
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some
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Dykova
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K.,
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MOLNAR,
K.,
1984:
Experimental
evidence
that
protozoans
causing
swimbladder
inflammation
in
common
carp
(Cyprinus
carpio
L.)
are
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of
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renicola.
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Authors'
addresses:
Dr.
K.
MOLNAR,
Veterinary
Medical
Research
Institute,
Hungarian
Academy
of
Sciences,
1581,
Budapest,
Hungary.
P.O.B.
18;
Dr.
F.vA
KovAcs-GAYER:
Central
Veterinary
Institute,
1149
Budapest,
Tabornok
u.
2.
Hungary.