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The purpose of this study was to evaluate the protective capacity of 130 kDa Dicrocoelium dendriticumprotein in hamsters experimentally infected with this parasite. Forty hamsters divided into four groups of ten animals each were used: G1 (control), G2 (infected), G3 (immunized with Freund’s adjuvant and infected), G4 (130 kDa protein vaccinated + adjuvant and infected). Infection with 40 metacercariae/hamster was carried out 4 weeks after the last immunization. Parasitological studies [number of eggs per gram (epg) and worm burden] and biochemical parameters (total proteins, albumin, and total bilirubin), hepatic enzymes [aspartate aminotransferase (AST) and alanine aminotransferase (ALT)], and total IgG levels were determined. A reduction in epg in G3 and G4 was observed 16 weeks postinfection with the higher reduction percentage in the latter (25.2%). No statistically significant differences were detected in the number of recovered worms among groups, although the mean was slightly less in G4 (12.2±2.08, mean±SE) than in G2 (15.4±2.90). In G4, global protection was 20.9% and an increase in AST and ALT levels was observed. Total IgG levels were similar in the three infected groups. The protection obtained was inadequate, so the antigen dose, immunization–infection period, adjuvants, and immunization route must be optimized.The purpose of this study was to evaluate the protective capacity of 130 kDa Dicrocoelium dendriticumprotein in hamsters experimentally infected with this parasite. Forty hamsters divided into four groups of ten animals each were used: G1 (control), G2 (infected), G3 (immunized with Freund’s adjuvant and infected), G4 (130 kDa protein vaccinated + adjuvant and infected). Infection with 40 metacercariae/hamster was carried out 4 weeks after the last immunization. Parasitological studies [number of eggs per gram (epg) and worm burden] and biochemical parameters (total proteins, albumin, and total bilirubin), hepatic enzymes [aspartate aminotransferase (AST) and alanine aminotransferase (ALT)], and total IgG levels were determined. A reduction in epg in G3 and G4 was observed 16 weeks postinfection with the higher reduction percentage in the latter (25.2%). No statistically significant differences were detected in the number of recovered worms among groups, although the mean was slightly less in G4 (12.2±2.08, mean±SE) than in G2 (15.4±2.90). In G4, global protection was 20.9% and an increase in AST and ALT levels was observed. Total IgG levels were similar in the three infected groups. The protection obtained was inadequate, so the antigen dose, immunization–infection period, adjuvants, and immunization route must be optimized.

Hepatic enzymes and biochemical parameter values were analysed in the sera of 32 lambs: 12 infected with 1,000 Dicrocoelium dendriticum metacercariae, 12 with 3,000 and eight controls. Blood samples were collected at intervals of 30 days from day 0 post-infection (p.i.). Half the lambs in each group were slaughtered on days 60 and 180 p.i, respectively. A histopathological and ultrastructural study was carried out on the liver, gall bladder and hepatic lymph nodes of all animals. A minute increase was detected in the bilirubin (7%) and albumin (3%) values in the infected lambs (with 30–2,063 worms) in comparison with those of the controls. The hepatic enzyme values did increase, above all aspartate aminotransferase (19%) and alanine aminotransferase (22%), mainly in the lambs tested with 3,000 metacercariae (38% and 48%, respectively). The increase was significant 60 days p.i. The severity of the lesions was closely associated with the parasite burden.

An epidemiological study on dicrocoeliosis caused by Dicrocoelium dendriticum was carried out on sheep, molluscs and ants in the mountains of León province (NW Spain) between 1987–1991. The results concerning the intermediate hosts and a review of some aspects of dicrocoeliosis are summarized. Mollusc collection for the helminthological study was random throughout the study area at fortnightly intervals. Twenty-nine Gastropoda species were identified. D. dendriticum infection was only detected in 2·98% of the 2084 Helicella itala examined and in 1·06% of 852 H. corderoi. The highest infection prevalence was detected in H. itala in September and in H. corderoi in February. Daughter sporocysts with well-developed cercariae predominated in spring and autumn. Infection prevalence increased with mollusc age and size. Ants were collected from anthills or plants to which they were attached. The behaviour of ants in tetania was followed. Twenty-one Formicidae species were identified, but only the following harboured D. dendriticum: Formica cunicularia (1158 examined specimens, 0·69% infection prevalence, 2–56 metacercariae per ant); F. sanguinea (234, 1·28%, 2–63); F. nigricans (1770, 4·97%, 1–186); F. rufibarbis (288, 6·59%, 2–107). In a flat area close to León town, 95·39% of the 2085 F. rufibarbis specimens collected in tetania contained metacercariae (1–240) in the abdomen. These were used for parasite characterization by isoelectric focusing and to infect lambs and hamsters. Only one brainworm per ant was found.

Abstract: The ELISA technique was used to study the kinetics of IgG antibodies against excretory–secretory (ES) and somatic (So) antigens of Dicrocoelium dendriticum in the sera of 32 lambs: 12 experimentally infected with 1,000 metacercariae, 12 with 3,000 and 8 controls. Both antigen types were used at a 2 μg/ml concentration. Dilutions of sera and the anti-sheep IgG peroxidase conjugate were: 1:200 and 1:6,000, respectively. Optical density values for each type of antigen in the two infected groups were higher than the cut-off point from day 30 post infection (p.i.), showing positive infection. Maximum antibody levels were observed 60 days p.i. and remained high until the experiment ended 180 days p.i. This pattern was similar for both ES and So antigens, although with slightly lower figures in the latter. Antibody kinetics were very similar for each of the two doses, except on day 30 p.i. No correlation between the antibody level and parasite burden could be established.

Dicrocoelium dendriticum egg output in cattle from five locations of the Porma river basin (León Province, Northwest Spain) was studied at monthly intervals between March 1986 and March 1987. We foundD. dendriticum eggs in 37.64% of the 1251 samples examined, and the number of eggs per gram (epg) ranged from 10 to 1000 (average, 41.65±2.73). The main eggelimination period, for prevalence, was autumn-winter. The average epg values were quite similar during all months except March, when the maximum was detected. The infection prevalence increased in cattle aged up to 2 years and then a slight, gradual decrease was observed with increasing host age. The average epg values ranged from 40.08±3.24 to 48.33±12.42 in all age groups except the oldest animals, for which the figures were lower. The rate of egg elimination was higher in animals that came from locations situated at a greater altitude.

In the present study,Diplectanum laubieri was redescribed from material obtained from wild and cultured fish. The population dynamics ofD. aequans andD. laubieri under culture conditions was studied. The prevalence and mean intensity (average number of worms per parasitized fish) were 80.64% and 112 forD. aequans and 67.74% and 59.61 forD. laubieri, respectively. Both Diplectanidae exhibited seasonal variations, with maximal infection levels occurring in winter, suggesting continuous parasites recruitment, and infection levels tended to increase with host age. Male hosts were more heavily infested than females. The apparent positive association betweenD. aequans andD. laubieri was not confirmed statistically. The Diplectanidae showed definite and different patterns of gill distribution. Histopathological gill damage mainly consisted of hyperplasia of the epithelium, fusion of branchial lamellae and the presence of hemorrhagic and inflammatory foci with leucocytic infiltration. The results demonstrated the pathological importance of both Diplectanidae for the cultivation of sea bass.