The effects of crowding on adults of Echinostoma caproni in experimentally infected golden hamsters.

Fifty-nine of 60 (98%), 6-month-old male golden hamsters, Mesocricetus auratus, fed 15 (group A), 50 (group B), or 200 (group C) metacercarial cysts of Echinostoma caproni (Digenea: Echinostomatidae) were infected 7-34 days postexposure. The mean number of worms recovered in groups A, B and C were 9, 10, and 50, respectively. The percentage recovery was significantly different between group A (63%) and groups B (21%) and C (23%). The intestine was divided into three equal regions (I, II, III). Worms from group A were located in segments II and III of the small intestine whereas worms from groups B and C were distributed in all three segments. The body area, ovarian and testicular areas of worms from group A were greatest, followed in decreasing order by body and gonadal areas of worms from groups B and C. Echinostoma caproni eggs were found in the faeces of all the hamsters examined from groups A, B and C by days 9, 10 and 11, respectively. Physical damage occurred at the site of attachment of the echinostome. Pathological observations indicated the presence of enlarged lymphatic nodules with lymphocytes being the primary cellular infiltrate at the site of parasite attachment.     

Development and pathology of Echinostoma caproni in experimentally infected mice

In the present article, several parasitological features of mice, each experimentally infected with 75 metacercariae of Echinostoma caproni (Trematoda: Echinostomatidae), were studied during the first 12 wk postinfection. Moreover, the early pathological responses also were analyzed and compared with data previously published on other host species of E. caproni to gain further insight into the factors determining worm rejection or establishment of chronic infections. The results obtained show that the pattern of E. caproni infection in mice is consistent with a highly compatible host-parasite system. This combination is characterized by a high worm establishment, high egg output, and long survival of the worms. However, some differences with respect to other highly compatible hosts have been observed, particularly in relation to the survival of the adult worms. Histological studies suggest that the kinetics of goblet cells, mucosal neutrophils, and mononuclear inflammatory cells in the mesentery seem to be essential in determining the course of E. caproni infection in mice.     

Kinetics of Echinostoma caproni (Trematoda: Echinostomatidae) antigens in feces and serum of experimentally infected hamsters and rats

This study reports on the kinetics of antibody production to Echinostoma caproni and the dynamics of antigens in feces and sera in 2 experimental hosts (hamsters and rats) that display different degrees of susceptibility with this echinostome. Echinostoma caproni produced chronic infections in hamsters, whereas rats lost the infection at 49-56 days postinfection (DPI). Hamsters developed higher antibody responses than rats, probably in relation to different intestinal absorptions of worm antigens in each host species. The levels of coproantigens were indicative of the course of infection in each host. Positive coproantigen levels were detected at 1-2 DPI in both hosts, and the values remained positive until the end of the experiment in hamsters; in rats, the coproantigen levels reverted to negative values, coinciding with the loss of infection. High levels of circulating antigens were detected in hamsters from 21 DPI to the end of the study. In contrast, low levels of E. caproni seroantigens were detected in rats only. These observations may reflect the differences in local inflammatory responses induced by E. caproni in each host species.     

Echinostoma caproni in mice: studies on the attachment site of an intestinal trematode

During infection in mice Echinostoma caproni is attached to the mucosa of the small intestine with the ventral sucker (acetabulum). The morphology, histology and dynamics of attachment sites from primary infections were examined. The sites were highly characteristic microscopically, and consisted of a plug of grasped mucosa occupying the cavity of the ventral suckers. The mucosa in the area of the small intestine where the parasite resided showed marked villous atrophy and crypt hyperplasia. The cellular composition of the attachment sites did not appear significantly different from what was seen in other parts of the mucosa in the residential area, and the study did not reveal any specific cellular host response at the attachment site. After mechanical removal of the parasites from unfixed tissue in saline, the attachment sites gradually reduced in size and disappeared. It is suggested that the attachment sites are only temporary structures, formed by the mechanical grasp of the ventral sucker as the parasites move about in the residential area of the intestine.     

Echinostoma caproni in mice: shedding of antigens from the surface of an intestinal trematode

The surface antigens, which induce a serum antibody response during infection of mice with the intestinal trematode Echinostoma caproni, were examined. It was demonstrated that antigens are shed from the surface of juvenile and 4-week old adult E. caproni during in vitro culture. SDS-PAGE and Western blot analysis of in vitro shed and detergent solubilized surface antigens indicated that the four major antigens released from the surface of adult parasites had molecular masses of approximately 26,000, 66,000, 75,000 and 88,000. A modified ELISA technique showed the in vitro turn-over rate of the surface antigens to be very high, with a half-life of 8-15 min in both juvenile and adult E. caproni trematodes. Transmission electron microscopy of the surface of adult parasites revealed a highly active secreting tegument which was densely packed with membrane-bound vesicles, reflecting the high rate of shedding of the surface antigens. An attempt to immunize mice with detergent solubilized adult surface antigens failed to induce resistance to infection with metacercariae of E. caproni.     

Kinetics of antibodies and antigens in serum of mice experimentally infected with Echinostoma caproni (Trematoda: Echinostomatidae)

The present study reports on the kinetics of antibodies and antigens in serum of mice experimentally infected with 75 metacercariae of Echinostoma caproni during the first 12 wk postinfection (wpi). Antibody titers in the serum of mice were determined by an indirect enzyme-linked immunosorbent assay (ELISA) using excretory/secretory (ES) antigens of E. caproni. The early detection of antibodies against ES antigens of E. caproni is feasible using indirect ELISA. Mice developed significant antibody responses at 2 wpi, and the values progressively increased until the end of the experiment. This may be related to the intestinal absorption of adult worm antigens that induces humoral responses. The presence of E. caproni circulating antigens was determined by a capture ELISA based on polyclonal rabbit antibodies against ES antigens of E. caproni. High levels of seroantigens in mice were detected by 1-2 wpi, probably because of the local inflammatory responses in mice induced by the adult worms. A drop in circulating antigen levels was observed at 9 wpi, which could reflect changes in the intestinal tissues over the course of the infection.     

Chronological observation of intestinal lesions of rats experimentally infected with Echinostoma hortense

Intestinal histopathological changes due to infection with Echinostoma hortense (Trematoda) were studied in rats after experimental infection with the metacercariae. The metacercariae were obtained from the tadpoles of Rana nigromaculata, a second intermediate host infected in the laboratory. Total 18 albino rats (Sprague-Dawley) were given 200 matacercariae each and sacrificed on the day 1, 3, 7, 11, 22 or 44 post-infection (PI). Segments of the small intestine at 1, 3, 5, 8 and 30 cm posterior to the pylorus (PTP) were resected and studied histopathologically. 1. The flukes were seen to have intruded into the intervillous space in the upper small intestine at early stages (1-3 days PI), however, they were located mainly in the intestinal lumen at later stages (7-44 days PI). The flukes were sucking and destroying the epithelial layers of villi with their oral and ventral suckers. 2. Histopathological changes of the intestine were recognizable in as early as 1-3 days after infection, and the changes became severer as the infection progressed. 3. The intestinal mucosa was histopathologically characterized by villous atrophy and crypt hyperplasia throughout the infection period. Major villous changes were blunting, fusion, severe destruction and loss of epithelial layers of villi. Villous/crypt (V/C) height ratio was remarkably reduced from 3:1 in controls to 1:1 in severely infected animals. In the stroma of villi, inflammatory cell infiltrations, vascular congestion, edema, and/or fibrosis were recognized. The goblet cells were increased in number after 11 days PI.(ABSTRACT TRUNCATED AT 250 WORDS)     

Reproduction of the trematode Echinostoma caproni parthenites (Digenea: Echinostomatidae)

Dynamics of the reproduction in the trematode Echinostoma caproni parthenites (Echinostomatidae) was observed. Early laying and maturation of the generative cells are for the first time shown to be characteristic for all parthenogenetic generations. Really the process of reproduction had been finishing to the beginning of the generating of new age by parthenites. Mother sporocysts, as well as redia of different generations, in fact stop producing new generative cells with the beginning of the generating of new age, and assume the function of a brood pouch. This feature was considered previously as peculiar mainly to mother sporocysts. Data on the autotomy of the anterior body end in mother sporocysts are verified. In our opinion, these data are an evidence of an early manifestation of the evolutionary trend to the morpho-functional regress and disintegration of the parasitic stage of mother sporocyst.     

Echinostoma caproni in mice: ultrastructural studies on the formation of immune complexes on the surface of an intestinal trematode

The binding of mouse antibodies to the surface antigens of juvenile and 7 and 28 day old Echinostoma caproni was examined by transmission electron microscopy of thin sections of parasites, which were treated with antibodies in a double sandwich technique with ferritin-conjugated antibody. The surface of freshly recovered mature adult parasites was covered with an irregular but often rather intensive mouse antibody containing matrix, which probably represents a layer of mouse antibody/parasite antigen complexes. The complexes were lost after in vitro culturing of the parasites for 24 h, but incubation of the in vitro-maintained antibody-negative adult parasites with immune mouse serum led to reformation of a similar but less intensive cover with immune complexes. Juvenile and young stages of E. caproni, which had never been exposed to host antibodies, obtained a layer of immune complexes on their surface after incubation with immune mouse serum in vitro. In both young and mature parasites, the antibody-antigen complexes were observed to be rather loosely attached to the outer surface of the parasites, where the antigens probably constitute a part of the irregular glycocalyx of the organisms. It may also be that the antigens are present as isolated excretion along the surface of the parasites. Several sections indicated that the parasite surface antigens may be present in the tegument in vesicles which fuse with the outer membrane of the parasite whereby their contents are released to the exterior.     

The effects of crowding on adults of Echinostoma revolutum (Digenea: Echinostomatidae) in experimentally infected golden hamsters, Mesocricetus auratus

All 30 female golden hamsters, Mesocricetus auratus, fed either 125 +/- 50 (group A), 300 +/- 50 (group B), or 500 +/- 50 (group C) metacercarial cysts of Echinostoma revolutum were infected 7-35 days postexposure. The mean number of worms in A, B, and C were 62, 96, and 212, respectively. Most of the worms in A were in the jejunum, but in C worms were about equally distributed in the duodenum, jejunum, and ileum, and some were in the cecum. The body area and wet and dry weights of worms from C were significantly less than that of A or B at 2, 4, and 5 wk postinfection. Echinostoma revolutum eggs were in the feces of 100% of the hamsters by days 12, 13, and 14 in A, B, and C, respectively.     

Concurrent infections of the trematode Echinostoma caproni and the tapeworms Hymenolepis diminuta and Hymenolepis microstoma in mice

Superimposing the intestinal tapeworm Hymenolepis diminuta on an established infection with the trematode Echinostoma caproni or simultaneous infection of mice with H. diminuta and Hymenolepis microstoma caused destrobilation and expulsion of H. diminuta, whereas establishment and growth of H. microstoma under the same infection regimes were not affected. In contrast, simultaneous superimposition of H. diminuta and H. microstoma on an established E. caproni infection caused destrobilation and expulsion of both H. diminuta and H. microstoma.     

Immunodepression in hamsters experimentally infected with Opisthorchis viverrini

Hamsters experimentally infected with Opisthorchis viverrini had significant depression of the antibody response to sheep red blood cells. The depression was more severe with prolonged infections. Lymphoproliferative response to phytohaemagglutinin stimulation was also depressed when compared with uninfected controls. The immunodepression in these animals was abolished by anthelmintic treatment, suggesting that the immunodepressive effect is reversible and is associated with active infection.     

Single and multiple worm infections of Echinostoma caproni (Trematoda) in the golden hamster

Six of 10 hamsters fed a single metacercarial cyst of Echinostoma caproni (single-worm infections) and 13 of 19 hamsters fed either 2 or 5 cysts (multiple-worm infections) were infected with adult echinostomes at necropsy 22 days post-infection. Considerable histopathological changes to the small intestine occurred in hamsters carrying single-worm infections. There were no differences in either mean length, width or wet weight of echinostomes in single- versus multiple-worm infections. The mean number of eggs/worm from single-worm infections (525) was significantly greater than that from multiple-worm infections (288). The average percentage of fully developed miracidia/worm from single worms (94%) was similar to that from worms in multiple infections (92-95%). Single worms of E. caproni were capable of self-fertilization and production of viable eggs. Miracidia derived from single worms were as capable of infecting laboratory-reared Biomphalaria glabrata and producing patent rediae as were those from multiple infections.     

Concurrent infections of Echinostoma caproni and Echinostoma trivolvis in ICR mice.

ICR female mice, 6- to 8-weeks old, were exposed concurrently to 25 metacercarial cysts of Echinostoma caproni and 25 metacercarial cysts of Echinostoma trivolvis and necropsied 10 and 14 days post-infection. Controls consisted of mice exposed singly to either 25 or 50 E. caproni or E. trivolvis cysts. All 23 mice exposed to E. caproni cysts were infected with a total of 331 worms (37.8%), whereas only 11 (37.9%) of 29 mice exposed to E. trivolvis cysts were infected with a total of 77 (6.4%) worms. In the concurrent infections, 13 (59.1%) of 22 mice were infected with both species and the percentage of worm recovery was 72.6% for E. caproni and 14.2% for E. trivolvis. There was no difference in worm distribution of either species in single vs concurrent infections. In concurrent infections at 14 days PI, there was a significant decrease in the body area of worms of both species, when compared to single worm species.     

Free-pool amino acids in Biomphalaria glabrata infected with Echinostoma caproni as determined by thin-layer chromatography

Thin-layer chromatography was used to analyze the free-pool amino acids of the digestive gland-gonad complex (DGG) of Biomphalaria glabrata infected with Echinostoma caproni and uninfected (control) snails. Qualitative analysis revealed the presence of histidine, lysine, serine, alanine, valine, and isoleucine or leucine in all samples. Quantitative analysis of lysine and valine gave mean weight percentages of 0.00699 +/- 0.0022 and 0.00174 +/- 0.00056, respectively, in the DGG of uninfected snails, and 0.00504 +/- 0.0014 and 0.00254 +/- 0.00033, respectively, in the DGG of infected snails. The differences in values between infected and uninfected snails were not statistically significant (Student's t-test, P > 0.05).     

Infectivity, growth, development and pathology of Echinostoma caproni (Trematoda) in the golden hamster

Laboratory hamsters (Mesocricetus auratus) were experimentally infected with 75 ± 15 metacercarial cysts of Echinostoma caproni. Worms were recovered from days 7 to 89 post-infection with eight to 90 (average 37) parasites in the small intestine. Worm wet weights averaged 0.85 mg at 10 days, 1.8 mg at 17 days, 3.4 mg at 45 days, and 7.7 mg at 89 days; average dry weights for the identical days were, 0.15, 0.30, 0.70 and 2.2 mg, respectively. The average body area of worms fixed in hot (80°C) alcohol-formalin-acetic acid was 0.21 mm² on day 3, 4.9 mm² on day 10, and 17.7 mm² on day 42. Clinical signs in some hamsters included progressive unthriftiness and watery diarrhea. Gross examination revealed enlarged lymphatic nodules along the length of the small intestine. The histopathological responses of hamsters to the parasite showed erosion of the intestinal villi with lymphocytic infiltration being the primary response; hemorrhagic areas were also observed in the villi.     

Effects of Echinostoma caproni infections on metallic ions in the intestinal mucosa of ICR mice

Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to study metallic ions in the intestinal mucosa of ICR mice infected with Echinostoma caproni and the mucosa of uninfected control mice. Infected mucosa (n = 9 with about 100 mg wet weight per sample) were examined at 2 weeks p.i. in mice that were infected with about 25 worms per host. Uninfected mucosa (n = 9 with about 100 mg wet weight per sample) were examined in the same time frame as the infected mucosa. Five metals were measured in the mucosa by ICP-AES analysis, as follows: calcium, potassium, magnesium, sodium and zinc. There were no significant differences (Student's t-test, P > 0.05) in the concentrations of calcium, potassium or zinc in infected versus uninfected mucosa. The concentration of sodium was significantly greater (P < 0.05) in the mucosa of infected versus uninfected mucosa, but the situation was reversed in regard to magnesium.     

Inflammatory responses in the intestinal mucosa of gerbils and hamsters experimentally infected with the adult stage of Taenia solium

The inflammatory response in gerbils and hamsters harbouring experimental infections with Taenia solium adult parasites as well as worm burden and duration of infections were examined. For this purpose, non-suppressed or immunosuppressed rodents were infected with eight cysticerci and necropsied at different times up to 35 days post-infection. Cells in the mucosa surrounding the implantation site of T. solium scolices (duodenum-jejunum) and in ileum were counted in stained sections. A competitive enzyme linked immunosorbent assay was used to determine histamine concentration in intestinal fluid. In non-suppressed hosts, an inflammatory reaction developed with scarce macrophages, a slight increase of plasma cells, lymphocytes and fibroblasts, a moderate increase of eosinophils and neutrophils, and high numbers of goblet and mast cells. Goblet cells began to increase at 6 days post-infection and peaked at 13 days post-infection with a four-fold increase with respect to the control group. Mast cells only increased in gerbils starting at 9 days post-infection with an eight-fold increase when cells peaked between 11 and 19 days post-infection. Histamine concentration in intestinal fluid of gerbils had a similar behaviour to mast cells. Minimal increase of mast cells was seen in hamsters. The recovery of tapeworms was inversely related to the number of both cell types, which decreased when tapeworms were eliminated. Infections lasted up to 25 days in gerbils and up to 46 days in hamsters. Worms measured only 1-2 cm in gerbils and up to 40 cm in hamsters. When gerbils were suppressed with the steroid methyl predinisolone, tapeworms could be recovered up to 35 days post-infection and tapeworms measured up to 22 cm, a minor increase of goblet and mast cells was observed and histamine concentration was similar to that in non-infected animals. Our results suggest that expulsion of T. solium in gerbils and hamsters may be related to the increase of goblet cells and mast cells, but these cells may have different roles in each rodent model of taeniosis.