FISHERIES AND MARINE SERVICE
Translation Series No.
4018
Changes in the white blood cell composition of carp infected with
D. extensus (Monogenoidea, Dactylogyridae) in the light of a new
classification of formed elements
by N.A. Golovina
Original title: Izmeneniyav sostave beloi krovi karpa pri zarazhenii
Dactylogyrus extensus (Monogenoidea, Dactylogyridae) v svete
novoi klassifikatsii formennykh elementov
From:
Parazitologiya 10: 178-182, 1976
Translated by L. Margolis
Department of Fisheries and the Environment
Fisheries and Marine Service
Pacific Biological Station
Nanaimo, B.C.
1977
7 pages typescript
4
A study of hematological characteristics of various diseases of
fish has not only theoretical but also great practical importance. On the
one hand, they permit evaluating the nature and depth of influence of a
particular parasite, and, on the other hand, they can substantially help
with differential diagnosis of diseases, especially those which have a
similar clinical picture.
In this connection, alterations in the composition of the white
blood cells of fish, occurring under the influence of parasites, is of great
interest because they can have a more or less specific nature.
A number of papers have been devoted to changes in hematological
characteristics of carp with dactylogyrosis. Bauer (1958), referring to
Lauva, indicates that the number of monocytes and histiocytes increases
and the number of lymphocytes decreases during infection with Dactylogyrus
vastator. Uspenskaya (1961), on the contrary, notes that in young carp
infected with Dactylogyrus vastator, the number of monocytes decreases to
one-third and the number of neutrophils increases 5.5 times. According to
the same author, the hemoglobin content decreases by one half. Sadkovskaya
(1958) notes an increase in the number of monocytes and neutrophils in carp
infected with Dactylogyrus extensus.
Such contradictory results obtained by different authors in checking
the leucocyte formula of the blood is explained not so much by different
degrees of infection of fish with Dactylogyrus, but by deficiencies in the
method of identification of the white blood cellular elements of fish. Thus,
Sadovskaya differentiated lymphocytes, monocytes, polymorphonuclear
granulocytes, and neutrophils, i.e., four categories of white blood cells;
but Uspenskaya differentiated only three groups -- lymphocytes, monocytes,
and neutrophils; and Lauva identified still another group -- histiocytes.
In 1970 Ivanova propOsed principally a new genetic classification of
fish blood cells. Based on staining properties of cells in different stains
she distinguished in the blood of teleost fish up to 22 formed white blood
elements. Since this classification permits evaluation of the white blood
cell picture in fish in greater detail, we used it to follow changes in the
leucocyte composition during various common diseases of carp, including
dactylogyrosis. Information on the morphology of the cells of the blood of
carp in the light of the new classification is non-existent in the literature,
therefore the beginning of the investigation was devoted to the study of the
normal picture of its blood.
In the peripheral blood of carp 7 groups of formed elements were
noted: lymphocytes and monocytes (agranulocytes), and eosinophil, pseudoeosinophil,
basophil, peudobasophil and neutrophil granulocytes (fig. 1). The most
numerous in the blood of carp are lymphocytes with a dense red-violet nucleus
which is surrounded by a narrow zone of strongly basophilic cytoplasm. Monocytes
have a very characteristic lobate nucleus and grayish, homogeneous cytoplasm.
Of the granulocyte leucocytes themselves many groups are neutrophils. In the
blood of carp 4 groups of neutrophils were noted: myelocytes, metamyelocytes,
and forms with rod and segmented nuclei. They differ from one another in the
structure and form of the nucleus; their cytoplasm is almost colorless, filled
2
with fine, specific granules.
Myelocytes have a comparatively large red-violet
nucleus.
In metamyelocytes, as a rule, it is rounded or oval and lies
eccentrically.
The nucleus in rod neutrophils is elongated, frequently with a
small indentation.
In segmented-nucleus.forms the nucleus is divided into
two lobes. Eosinophils are round with a compact oval or round nucleus; the
cytoplasm is filled with rather large, closely packed granules displaying an
absolute acidophilia.
The entire cytoplasm of pseudobasophils is filled with
heterogeneous red-violet, almost black granules.
The cytoplasm of basophils
contains large red granules, and in pseudoeosinophils they are raspberry
colored and acicular.
For 2-year old carp
observed during the course of
general condition of the fish
sampled the blood three times
[see Table I].
infected with Dactylogyrus extensus, which we
a month (11 June to 9 July), we recorded the
and clinical manifestations of disease, and we
to check for changes in the leucocyte formula
[Table I.] Changes in the numbers of leucocytes in the blood of carp.with
dactylogyrosis (in 70)
Cell type
Fish group
healthy
infected (1)
infected (2)
infected (3)
Myelocyte neutrophil
Metamyelocyte neutrophil
Rod neutrophil
Segmented neutrophil
1.5+0.5
1.2+0.5
2.0+0.5
1.5+0.5
1.6+0.6
4.4+0.4
1.9 +0.6
--
1.2+0.4
2.4+0.3
1.1+0.2
075
2.2+0.5
5.0+0.7
3.1+0.7
171
Total no. of neutrophils
6.3+0.5
7.9+1.4
5.2+0.4
11.4+0.7
-3.6+0.9
3.6_+0,9
2.6+0.3
4.0+0.5
80.5+5.5.
2.8+0.6
-2.8+0.6
17.1+1.7
---
5.0+0.5
l,g
6.2+1.0
12.1_+1.2
74.8+2.0
8.4+0.9
70.9+2.0
13.3+1.2
61.0+1.0
Eosinophils
Pseudoeosinophils
Basophils
Pseudobasophils
Monocytes
Lymphocytes
Among the leucocytes in infected fish we noted cells that differed
morphologically from the typical form (fig. 2). Among monocytes, for example,
we found forms with vacuolated nucleus and cytoplasm, the cytoplasm being
vacuolated more frequently. In the lymphocyte group there are cells with
nodular and coarsely textured nuclei.
There are lymphoblasts, but they are
The cytoplasm of diffèrent neutrophil granulocytes stains
found infrequently.
smoky-gray, and the granules are beaded in appearance and concentrated in the
margins of the cytoplasm. All these changes in morphology are not specific
but appear with anemia.
3
As for quantitative characteristics of the pathological process,
the leucocyte formula was first checked on June 11, 1974 (1). At this time
the gills were pale, swollen, and profusely covered with slime (mean weight
of fish -- 43 gm). Upon microscopic examination we found from 600 to 1200
specimens of Dactylogyrus extensus per fish. In the blood there was a reduced
number of lymphocytes, an absence of pseudoeosinophils and segmented neutrophil
granulocytes, and there appeared eosinophils, which were absent from normal
fish (see table). Among the erythrocytes there were comparatively many (up
to 17.5 7. ) immature forms (polychromatophilic and oxyphilic normoblasts),
which normally occur at a rate of 6 to 10%.
After two weeks, on June 24 (2), necrosis of the gill lamellae
commenced. The number of Dactylogyrus decreased to a mean of 60 parasites
per fish. Analysis of the blood indicated an abrupt increase in the number
of eosinophi1s from 2.8 + 0.6 to 17.1 + 1.7 7. and simultaneously a decrease
in the total number of neutrophils attributable largely to the metamyelocyte
group (from 4.4 + 0.4 to 2.4 + 0.3%) and in the lymphocytes (from 74.8 + 2.0
to 70.9 + 2.0%). Such an abrupt change in the gills led to further changes
in the r-ed blood cells. The number of young forms reached up to 41%. There
were especially many polychromatophilic and even basophilic normoblasts. At
the same time their occurs intensive replenishment in the number of red
blood cells due to rapid release of immature forms into the blood stream.
Consequently there arises polychromatophilic anemia and anisocytosis.
The next group of fish was taken for analysis on July 9, i.e.
28 days after the onset of the disease (3). Clinically these fish had
begun regeneration of the gill lamellae. The mean weight of fish at this
time was 56 gm, i.e. in approximately a month the fish increased in weight by
13 gm. In the blood there was a recovery in the number of basophilic and
segmented neutrophils, and pseudoeosinophils, which were generally absent
earlier in diseased fish; and the number of eosinophils declined to
5.0 + 0.5% and yoùng forms of erythrocytes to 28.0%. The shift in the
quantity of granulocytes attests to the operation in the fish of a regeneration
process.
Thus, during the whole pathological process there occurs
substantial changes in the blood picture of carp (see the table and fig. 3).
The number of lymphocytes gradually decreased from a norm of 80.5 + 5.5% to
61.0 + 1.0%, but the number of monocytes increased 2-3 times. There is an .
increase generally in the number of granulocytes. Among them, the most
active phagocytes are neutrophils (Kudryavtsev and Kudryavtseva, 1974).
Segmented neutrophils possess maximum mobility and are highly specialized
cells, the first to leave the blood stream and migrate to the tissues.
Evidently, this explains the decrease and even their absence at the
beginning of the disease. The most characteristic feature of dactylogyrosis
is the appearance in the blood of eosinophils (mobile, phagocytic cells,
capable also of adsorbing histamine) which appear during necrosis of the
gill tissue.
4
Generalizing from the data obtained, it should be noted that the
in
the quantity of Dactylogyrus extensus leads to an abrupt change
increase
in the fish. It feeds poorly, resulting in retarded growth and significant
changes in the blood, of which the most characteristic is eosinophilia,
polychromatophilic anemia, and anisocytosis.
Literature
Bauer, 0. N. 1958. Relationships between parasites and hosts (fishes).
In: Basic problems in parasitology of fishes. Izd. LGU: 90-108.
Ivanova, N. T. 1970. Data on the morphology of fish blood. Rostov-on-Don:
1-136.
Kudryavtsev, A. A. and Kudryavtseva, L. A. 1974.
animals. Izd. "Kolas," M.: 399.
Clinical hematology of
Sadovskaya, O. D. 1958. Changes in the leucocyte formula of the blood of
carp during infection with Dactylogyrus extensus (solidus). In:
Contributions to helminthology on the 80th birthday of
K. I. Skrjabin. M.: 320-321.
Uspenskaya, A. V. 1961. The influence of Dactylogyrus vastator Nybelin,
1924 (Monogenoidea, Dactylogyridae) on carp. Zool. Zhurn., 40(1):
7-12.
J
- 5 -
f
9
Fig. 1.
4
Morphological picture of the blood of healthy 2-yearold carp (mag. 1OX90).
1, myelocyte. 2, metamyelocyte. 3, rod neutrophil. 4,
segmented neutrophil. 5, eosinophil. 6, basophil. 7,
pseudoeosinophil. 8, lymphocyte. 9, erythrocyte. 10,
monocyte.
Pappenheim stain.
i
P
- 6
Fig. 2. Change in the morphology of some cellular forms in carp
with dactylogyrosis.(mag. 12.5X90).
1, neutrophil with smoky-grayish cytoplasm. 2, monocytes with
vacuolated cytoplasm. 3, vacuolated lymphoblast. 4, lymphocyte
with coarse nucleus. 5, polychromatophilic normoblast.
Pappenheim stain.
i
7
60
III
20
10
0
70
60
20
10
0
■1
■11
.1
II
1
f=1
W
2
3
70
60
20
10
11 VI
.1 1
72221
80
70
60
20
5
6
11 VI
1/(. 0 Fl mp 0 b)
10
0
123
Fig. 3.
4
5
6
Dynamics of the principal forms of leucocytes
during dactylogyrosis.
1, lymphocytes. 2, monocytes. 3, basophils. 4,
pseudoeosinophils. 5, eosinophils. 6,
neutrophils.