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A perivisceral encapsulation process in Lymnaea glabra infected by Fasciola hepatica
JOURNAL
OF INVERTEBRATE
PATHOLOGY
49,
124-
126 (1987)
NOTES A Perivisceral Encapsulation Process in Lymnaea glabra Infected by Fasciola hepatica in the intervisceral spaces of these snails. The other viscera were of normal structure. The experimental snails did not show any living or degenerating parthenitae in their body at day 60 postexposure. Parts of their renal lamellae and their amebocyteproducing organ were as fibrous as the controls. Numerous tunnel-shaped cavities (D. Bouix-Busson, D. Rondelaud, and D. Barthe, Bull. Sot. Fr. Parasitol. 2, 103-107, 1984) occurred in the snail foot and mantle. The most characteristic lesions were observed around the digestive gland and intestine; these were used as the basis for classifying the snails into two subgroups. The 13 snails in subgroup 1 had smaller digestive glands with tubules which did not exceed 240 pm in diameter (instead of 290-420 km in diameter as in controls). Multiple areas of necrosis were present in all the tubules of these snails: in four snails, the number of epithelial cells per length unit (0.1 mm) was the same as in controls (19-20 cells) and the cell height varying from 30 to 40 pm; in the others, the cell number varied from 26 to 29 cells per length unit and the cell height from 26 to 60 pm, indicating the existence of cellular hyperplasia. These digestive gland morphological patterns corresponded to necrosis and reconstitution processes (D. Rondelaud and D. Barthe, Ann. Parasitol. Hum. Comp. 53, 255-264, 1978). In the seven snails of subgroup 2, the digestive gland had only four to nine tubules with a maximal tubular diameter less than 100 km. In some places, the tubular epithelium revealed irregular hyperplasia with 28-37 cells per length unit and cell height
Histological studies on Lymnaea glabra infected by Fakciola hepatica demonstrated the presence of variable tissue lesions in snails with an abortive infection (D. Bouix-Busson, D. Ron&laud, and D. Barthe, J. Parasitol. 35, 847-848, 1984). These lesions were somewhat similar to those in snails with living fasciolid parthenitae. However, specific tissue lesions were only observed in snails with abortive infections. This note reports the existence of an encapsulation process around the digestive gland of L. glabra with an abortive infection. One hundred snails, 4 mm in height, were collected in a road ditch at La Chabasse, commune of Saint-Priest-Taurion, Haute-Vienne. Fifty of them were individually exposed for 4 hr to a single miracidium of F. hepatica and the other 50 were used as controls. All snails were bred at 20°C in standard containers with 50 snails per container. Methods for breeding snails and exposing them to miracidia were described in a previous note (P. Busson, D. Busson, D. Rondelaud, and M. Pestre-Alexandre, Ann. Parasitol.
Hum.
Comp.
57, 555-563,
1982). Batches of 20 survivors each were randomly collected from breeding containers 60 days after exposure, and killed by dipping them in Bouin’s fluid and immediately breaking the shell. Five-micrometer serial sections were stained in Harris’ hematoxylin-modified Gabe’s trichrome. In the 20 control animals, the renal lamellar connective tissue and the amebocyte-producing organ were partially fibrous. No cellular proliferation was noted 124 0022-2011l87
$1 so
Copyright 0 1987 by Academic Press. Inc. All rights of reproduction in any form reserved.
NOTES
FIG. I. Light microscopy showing an irregular hyperplasia of tubular epithelium and an epithelial atrophy in the others ( x 135).
from 3.5 to 70 pm; in the other places, the epithelium was formed by a single layer of flattened cells, or it was apparently absent (Fig. 1). These tubules were surrounded by a granulomatous reaction with several layers of multivacuolated type-II amebocytes (D. Rondelaud and D. Barthe, Z. Parasitenkd. 65, 341-351, 1981) in the inner part, and several thin layers of flattened, fibroid cells in the outer part (Fig. 2). These type-II amebocytes were also observed in the basal part of this hyperplastic epithelium, or in the tubular lumen when the basement lamina was torn. The granulomatous reaction was sometimes limited to isolated areas of necrotic epithelial cells of the tubules, surrounded by layers of flattened cells without independent amebocytes. The gonadic acini were hypertrophic and had a normal activity. In all these snails, the intestinal lumen was empty surrounded by numerous necrotic epithelial cells. Small type-1 amebocyte nodules (D. Rondelaud and D. Barthe, lot. cit.) were seen in the fibrous areas of the amebocyteproducing organ: their presence suggests
in some places.
possible cell proliferation during the experiment. Type-II amebocytes were seen rarely in the hemolymph with the exception of those implicated in the granulomatous reaction. The granulomatous reaction noted around the digestive tubules of the snail subgroup 2 is similar to the encapsulation process described by previous authors in Lymnaea stagnalis (T. Sminia, E. Borghart-Reinders, and A. W. van de Linde, Cell Tissue Res. 153, 307-326, 1974), in Biomphalaria gLabrata (T. C. Cheng and T. A. Garrabrant, Int. J. Parasitol. 7, 467-472, 1977), or in Lymnaea palustris (A. M. McReath, T. A. J. Reader, and V. R. Southgate, 2. Parasitenkd. 67, 175- 184, 1982). This perivisceral reaction must be considered as a common detersive granuloma around tubular cells and is evidence of substances recognized by the snail amebocytes as foreign material. We interpret this encapsulation process in a snail as evidence of a reaction against modified host tissues (P, T. LoVerd, Gherson, J. and C. S. Richards, J. Znwr-
126
NOTES
FIG. 2. Light microscopy showing hemocytic infiltration and encapsulationprocessaround a digestive tubule (X 540).
tebr. Pathol. 39, 247-249, 1982). In our opinion, this reaction can only be explained by the presence of a toxic miracidial substance persisting in the snail during the 60 days of experiment. The tubular epithelium may react to this insult by successive cycles of necrosis, cellular infiltration, and hyperplasia, and finally atrophies prior to encapsulation. It would be of interest to know if this toxic substance is excreted by the degenerating sporocyst and/or if it is produced by cell necrosis which occasionally seen in the hyperplastic epithelia.
KEY WORDS: Lymnaea glabra; Fasciola hepatica; miracidia; perivisceral encapsu-
lation. DANIEL RONDELAUD DOMINIQUE BOUIX-BUSSON DOMINIQUE BARTHE Laboratoire d’Histologie FacultC de Mtfdecine 87025, Limoges Cedex and U.E.R. des Sciences Exactes et Naturelles (Malacologie Applique’e) 87060, Limoges Cedex. France Received February 4. 1986; accepted June 17, 1986
OF INVERTEBRATE
PATHOLOGY
49,
124-
126 (1987)
NOTES A Perivisceral Encapsulation Process in Lymnaea glabra Infected by Fasciola hepatica in the intervisceral spaces of these snails. The other viscera were of normal structure. The experimental snails did not show any living or degenerating parthenitae in their body at day 60 postexposure. Parts of their renal lamellae and their amebocyteproducing organ were as fibrous as the controls. Numerous tunnel-shaped cavities (D. Bouix-Busson, D. Rondelaud, and D. Barthe, Bull. Sot. Fr. Parasitol. 2, 103-107, 1984) occurred in the snail foot and mantle. The most characteristic lesions were observed around the digestive gland and intestine; these were used as the basis for classifying the snails into two subgroups. The 13 snails in subgroup 1 had smaller digestive glands with tubules which did not exceed 240 pm in diameter (instead of 290-420 km in diameter as in controls). Multiple areas of necrosis were present in all the tubules of these snails: in four snails, the number of epithelial cells per length unit (0.1 mm) was the same as in controls (19-20 cells) and the cell height varying from 30 to 40 pm; in the others, the cell number varied from 26 to 29 cells per length unit and the cell height from 26 to 60 pm, indicating the existence of cellular hyperplasia. These digestive gland morphological patterns corresponded to necrosis and reconstitution processes (D. Rondelaud and D. Barthe, Ann. Parasitol. Hum. Comp. 53, 255-264, 1978). In the seven snails of subgroup 2, the digestive gland had only four to nine tubules with a maximal tubular diameter less than 100 km. In some places, the tubular epithelium revealed irregular hyperplasia with 28-37 cells per length unit and cell height
Histological studies on Lymnaea glabra infected by Fakciola hepatica demonstrated the presence of variable tissue lesions in snails with an abortive infection (D. Bouix-Busson, D. Ron&laud, and D. Barthe, J. Parasitol. 35, 847-848, 1984). These lesions were somewhat similar to those in snails with living fasciolid parthenitae. However, specific tissue lesions were only observed in snails with abortive infections. This note reports the existence of an encapsulation process around the digestive gland of L. glabra with an abortive infection. One hundred snails, 4 mm in height, were collected in a road ditch at La Chabasse, commune of Saint-Priest-Taurion, Haute-Vienne. Fifty of them were individually exposed for 4 hr to a single miracidium of F. hepatica and the other 50 were used as controls. All snails were bred at 20°C in standard containers with 50 snails per container. Methods for breeding snails and exposing them to miracidia were described in a previous note (P. Busson, D. Busson, D. Rondelaud, and M. Pestre-Alexandre, Ann. Parasitol.
Hum.
Comp.
57, 555-563,
1982). Batches of 20 survivors each were randomly collected from breeding containers 60 days after exposure, and killed by dipping them in Bouin’s fluid and immediately breaking the shell. Five-micrometer serial sections were stained in Harris’ hematoxylin-modified Gabe’s trichrome. In the 20 control animals, the renal lamellar connective tissue and the amebocyte-producing organ were partially fibrous. No cellular proliferation was noted 124 0022-2011l87
$1 so
Copyright 0 1987 by Academic Press. Inc. All rights of reproduction in any form reserved.
NOTES
FIG. I. Light microscopy showing an irregular hyperplasia of tubular epithelium and an epithelial atrophy in the others ( x 135).
from 3.5 to 70 pm; in the other places, the epithelium was formed by a single layer of flattened cells, or it was apparently absent (Fig. 1). These tubules were surrounded by a granulomatous reaction with several layers of multivacuolated type-II amebocytes (D. Rondelaud and D. Barthe, Z. Parasitenkd. 65, 341-351, 1981) in the inner part, and several thin layers of flattened, fibroid cells in the outer part (Fig. 2). These type-II amebocytes were also observed in the basal part of this hyperplastic epithelium, or in the tubular lumen when the basement lamina was torn. The granulomatous reaction was sometimes limited to isolated areas of necrotic epithelial cells of the tubules, surrounded by layers of flattened cells without independent amebocytes. The gonadic acini were hypertrophic and had a normal activity. In all these snails, the intestinal lumen was empty surrounded by numerous necrotic epithelial cells. Small type-1 amebocyte nodules (D. Rondelaud and D. Barthe, lot. cit.) were seen in the fibrous areas of the amebocyteproducing organ: their presence suggests
in some places.
possible cell proliferation during the experiment. Type-II amebocytes were seen rarely in the hemolymph with the exception of those implicated in the granulomatous reaction. The granulomatous reaction noted around the digestive tubules of the snail subgroup 2 is similar to the encapsulation process described by previous authors in Lymnaea stagnalis (T. Sminia, E. Borghart-Reinders, and A. W. van de Linde, Cell Tissue Res. 153, 307-326, 1974), in Biomphalaria gLabrata (T. C. Cheng and T. A. Garrabrant, Int. J. Parasitol. 7, 467-472, 1977), or in Lymnaea palustris (A. M. McReath, T. A. J. Reader, and V. R. Southgate, 2. Parasitenkd. 67, 175- 184, 1982). This perivisceral reaction must be considered as a common detersive granuloma around tubular cells and is evidence of substances recognized by the snail amebocytes as foreign material. We interpret this encapsulation process in a snail as evidence of a reaction against modified host tissues (P, T. LoVerd, Gherson, J. and C. S. Richards, J. Znwr-
126
NOTES
FIG. 2. Light microscopy showing hemocytic infiltration and encapsulationprocessaround a digestive tubule (X 540).
tebr. Pathol. 39, 247-249, 1982). In our opinion, this reaction can only be explained by the presence of a toxic miracidial substance persisting in the snail during the 60 days of experiment. The tubular epithelium may react to this insult by successive cycles of necrosis, cellular infiltration, and hyperplasia, and finally atrophies prior to encapsulation. It would be of interest to know if this toxic substance is excreted by the degenerating sporocyst and/or if it is produced by cell necrosis which occasionally seen in the hyperplastic epithelia.
KEY WORDS: Lymnaea glabra; Fasciola hepatica; miracidia; perivisceral encapsu-
lation. DANIEL RONDELAUD DOMINIQUE BOUIX-BUSSON DOMINIQUE BARTHE Laboratoire d’Histologie FacultC de Mtfdecine 87025, Limoges Cedex and U.E.R. des Sciences Exactes et Naturelles (Malacologie Applique’e) 87060, Limoges Cedex. France Received February 4. 1986; accepted June 17, 1986