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.

After oral administration of ewes during mid gestation with 2000 freshly prepared sporulated oocysts of T. gondii isolate M4, abortions occurred between days 7 and 11 in 91.6% of pregnant and infected ewes. Afterwards, a further infection was carried out at late gestation in another group of sheep with 500 sporulated oocysts. Abortions happened again between days 9 and 11 post infection (pi) in 58.3% of the infected ewes. Classically, abortions in natural and experimental ovine toxoplasmosis usually occur one month after infection. Few experimental studies have reported the so-called acute phase abortions as early as 7 to 14 days after oral inoculation of oocysts, and pyrexia was proposed to be responsible for abortion, although the underline mechanism was not elucidated. In the present study, all placentas analysed from ewes suffering acute phase abortions showed infarcts and thrombosis in the caruncullar villi of the placentomes and ischemic lesions (periventricular leukomalacia) in the brain of some foetuses. The parasite was identified by PCR in samples from some placentomes of only one sheep, and no antigen was detected by immunohistochemical labelling. These findings suggest that the vascular lesions found in the placenta, and the consequent hypoxic damage to the foetus, could be associated to the occurrence of acute phase abortions. Although the pathogenesis of these lesions remains to be determined, the infectious dose or virulence of the isolate may play a role in their development.

The relation between gestational age and foetal death risk in ovine toxoplasmosis is already known, but the mechanisms involved are not yet clear. In order to study how the stage of gestation influences these mechanisms, pregnant sheep of the same age and genetic background were orally dosed with 50 oocysts of Toxoplasma gondii (M4 isolate) at days 40 (G1), 90 (G2) and 120 (G3) of gestation. In each group, four animals were culled on the second, third and fourth week post infection (pi) in order to evaluate parasite load and distribution, and lesions in target organs. Ewes from G1 showed a longer period of hyperthermia than the other groups. Abortions occurred in all groups. While in G2 they were more frequent during the acute phase of the disease, in G3 they mainly occurred after day 20 pi. After challenge, parasite and lesions in the placentas and foetuses were detected from day 19 pi in G3 while in G2 or G1 they were only detected at day 26 pi. However, after initial detection at day 19 pi, parasite burden, measured through RT-PCR, in placenta or foetus of G3 did not increase significantly and, at in the third week pi it was lower than that measured in foetal liver or placenta from G1 to G3 respectively. These results show that the period of gestation clearly influences the parasite multiplication and development of lesions in the placenta and foetus and, as a consequence, the clinical course in ovine toxoplasmosis.Electronic supplementary materialThe online version of this article (doi:10.1186/s13567-016-0327-z) contains supplementary material, which is available to authorized users.

In the present study, Diplectanum laubieri was redescribed from material obtained from wild and cultured fish. The population dynamics of D. aequans and D. laubieri under culture conditions was studied. The prevalence and mean intensity (average number of worms per parasitized fish) were 80.64% and 112 for D. aequans and 67.74% and 59.61 for D. 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 between D. aequans and D. 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.

The prevalence and aetiology of natural paramphistomosis was investigated in cattle slaughtered in the Castilla y León region (Spain) over a 3 year-period. The overall prevalence of positive animals was 6.20%. The parasite burden per animal ranged from 8 to 8005 (median=144) and the ruminal atrium had the highest parasite burden whereas the ruminal dorsal sac the lowest. The prevalence and parasite burden increased with age while these parameters were lower in cattle under intensive management. Calicophoron daubneyi was the only Paramphistomidae species identified using morphoanatomical, histological and molecular methods in the studied animals.

El artículo seleccionado no se encuentra disponible por ahora a texto completo por no haber sido facilitado todavía por el investigador a cargo del archivo del mismo.

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.

BackgroundIn the present study we studied and updated the prevalence of the infections caused by gastrointestinal nematodes (GIN) and Fasciola hepatica in grazing sheep in the northwest (NW) of Spain for the last six years (2006–2011), and its relationship with the current climatic conditions.MethodsWe analyzed faecal samples from 110 flocks located in four different provinces of the Autonomous Community of Castilla y León: 76.4% of them were situated in León, 12.7% in Zamora, 9.1% in Palencia and 1.8% in Valladolid.ResultsThe prevalence of GIN was 100% and the mean of eggs per gram (epg) in faeces was 237.2 (± 375.9) per flock. Regarding climatic conditions, we found a direct relationship between the GIN infection level and the maximum humidity (p<0.05) but inverse with the degree of solar radiation (p<0.05). The prevalence of fasciolosis was 59.3%, with a mean epg of 17.5 (± 33.9) per flock; these values were correlated with the minimum humidity and precipitations (p<0.05). Comparing our results in León with previous studies during the early 1990s, the mean epg of GIN was increased slightly (134.3 epg); regarding fasciolosis, the prevalence rose significantly, from 26.7% to 60.5%. Since the 1990s we observed that the maximum temperature is nowadays 0.45°C higher (17.0°C) and the minimum 0.5°C lower (5.2°C); the rainfall values were very similar in both decades but at the present time the humidity is higher (75.9%).ConclusionsWe found that the prevalence of GIN and F. hepatica infections was directly influenced by the humidity and also by precipitations in the case of F. hepatica. Comparing the current prevalence with studies carried out in the same area for the early 1990s, we observed that nowadays the mean epg of GIN is higher with a possible cause being the differences in climatic conditions depending on the sampling year. Regarding F. hepatica infection, its prevalence rose significantly probably favoured by an increase in irrigated areas in the area of study.