Vaccination of mice and sheep with Fh12 FABP from Fasciola hepatica using the new adjuvant/immunomodulator system ADAD.

We evaluate the ability of a Fasciola hepatica FABP native antigen (Fh12) with a new vaccination system called ADAD to protect mice and sheep against an experimental F. hepatica infection. The vaccination protocol consists of a set of two injections. The first injection contains a micelle in which two components are included, saponin from Quillaja saponaria (Qs) and/or Anapsos (A) a Polypodium leucotomos hydroalcoholic extract, both emulsified in a non-mineral oil (Montanide) in a water/oil emulsion (30/70). This is subcutaneously injected to achieve the "adaptation" of the immune system to subsequent stimuli. The second injection contains in addition the Fh12 antigen. Two different experiments were carried out using two mouse strains (BALB/c and CD-1). Mice vaccinated with Qs+A+Fh12 presented a survival rate of 40%, when compared with control groups. Furthermore, we evaluated the efficiency of the vaccination in sheep against an experimental F. hepatica challenge. The vaccinated sheep presented lower fluke recovery (24.5%), number of eggs in bile fluid (58.1%) and faeces (40.3%) than control groups. The recovered flukes were shorter (32.7%), immature (34.0%) and with lower body mass (31.6%) than non-complete vaccinated sheep. Thus, the new ADAD system could be a good alternative for future vaccination experiments against fasciolosis.

Preliminary study on genetic variability of Dicrocoelium dendriticum determined by random amplified polymorphic DNA.

Genetic variability of adult specimens of Dicrocoelium dendriticum has been studied using random amplified polymorphic DNA (RAPD). The worms were collected from the infected livers of different sheep from several localities in León province (NW Spain). DNA fragments were amplified by means of decamer primer oligonucleotides of arbitrary sequence. Some primers produce complex and highly variable patterns of amplified DNA in D. dendriticum. Intra- and inter-population genetic variability of adult parasites were analyzed, scoring polymorphic and monomorphic reproducible bands by means of the Jaccard similarity, and dendrograms showing genetic relationships between individuals were obtained using the FITCH method. Genetic variability seems to be high in this parasite and genetic similarity within a population (worms infecting a single animal) is similar to the average similarity between worms from different sheep. These results suggest that each sheep is infected by numerous genetically different parasites from one or more populations of infected ants.

Lymnaea truncatula, intermediate host of some Plagiorchiidae and Notocotylidae species in León, nw Spain.

To study the distribution of Lymnaea truncatula in the Porma river basin (León, NW Spain) and its helminth fauna, malacological samplings were carried out at 66 points in the basin and the presence of these molluscs was detected in 31. To trace the dynamics of this mollusc population and the prevalence and intensity of its infection by trematodes, malacological samplings were made at fortnightly intervals over two years at five locations, situated in the upper and middle regions of the river Porma basin. To confirm the identity of the larval stages found in the molluscs, second intermediate and/or definitive hosts, depending on the trematode species, were experimentally infected to complete the life cycles. Two different species of Plagiorchiidae and one of Notocotylidae were identified. The infection prevalence of Plagiorchis elegans for the 6291 specimens of L. truncatula examined was 2.8% and infection was observed in snails collected in 7 of the 31 sample localities. This parasite was found in all months of the year, with the highest prevalence observed in July and October. When the corrected frequency values were considered, a slightly positive relationship was observed between the infection prevalence and the latter months. The highest percentages of snails harbouring immature sporocysts were detected in March and June-July, while the highest percentages with sporocysts containing mature cercariae were observed in spring and at the end of summer-autumn, and cercarial shedding in the latter. Of the 6291 L. truncatula examined 0.3% were infected by sporocysts of Opisthioglyphe ranae.(ABSTRACT TRUNCATED AT 250 WORDS)

Natural infection of Lymnaea truncatula by the liver fluke Fasciola hepatica in the Porma Basin, León, NW Spain.

For two years fortnightly malacological samplings were carried out to collect Lymnaea truncatula (Mollusca; Basommatophora) at five points in the upper and middle Porma river basin, León, Spain. The highest numbers of snails were collected in September, May and November. Of the 5486 molluscs examined, 11.41% harboured F. hepatica (Trematoda; Digenea) with an average intensity of 20.14. In general, the values of both infection prevalence and intensity increased with the size of the snails. It was in October when the highest figures for each parameter mentioned above were detected (18.73% and 28.48, respectively). The chi-square test showed statistically significant differences in relation to the infection prevalence among the groups of molluscs established according to: their length; the months in which they were collected; the sampling localities; monthly average ambient temperature; precipitation during the collection. Similarly, statistically significant differences were detected in the intensity of the infection among the groups of molluscs previously established, except for that based on the values of precipitation. Generally, parasites were found in the same snail at different stages of development. It seems that most mollusc infections occur in February-March and at the end of summer-beginning of autumn periods. The highest rate of rediae with mature cercariae ready to be shed were detected between September and December. Metacercariae in the grass samples were also observed at the end of autumn. For this reason, this period could be considered as the most suitable for infection of the definitive hosts to take place.

Dynamics of elimination of the eggs of Fasciola hepatica (Trematoda, Digenea) in the faeces of cattle in the Porma Basin, Spain.

In order to contribute to the knowledge of the epizootiological conditions in which fasciolosis develops in the León mountains, the elimination of Fasciola hepatica eggs in 10% of the total number of cattle (1301 samples) at five locations in the Porma river basin was recorded at monthly intervals between March 1986 and March 1987. The parasite was found in cattle [29.5% prevalence, average of 51.6 +/- 4.5 eggs g-1 (e.p.g.) faeces] throughout the year. The main egg elimination period was winter-spring, with maximum prevalence in January and maximum e.p.g. in February-March. Prevalence of infection in cattle generally increased with the host's age, whilst the average e.p.g. varied between different age groups.