The liver fluke, Fasciola hepatica, is one of the most important parasites of livestock, and it also infects humans. The proteolytic system of trematodes is critical for their interaction with the host and is a potential target for the development of novel vaccines. This work is focused on proteases secreted by F. hepatica adults and on FheCy2, a new protease inhibitor from the cystatin family. The proteolytic activity of the secreted proteases was analyzed using: (a) chromogenic protein substrates and fluorogenic peptide substrates, (b) selective protease inhibitors, and (c) a fluorescent activity-based probe for visualization of proteases. The results showed that the secreted proteases are cysteine proteases of papain family belonging to cathepsins L and B. These proteases were effectivelly inhibited by FheCy2 as demonstrated by enzymological analysis. It can be assumed that FheCy2 participates in the physiological regulation of endogenous proteases secreted by F. hepatica adults, which makes it attractive candidate protein for vaccination studies. Key words: Fasciola hepatica, cathepsins, proteolytic activity, substrate specificity, protease inhibitors (In Czech)

Fascioloides magna (giant liver fluke) is a digenetic trematode with two-host life cycle and high veterinary importancy. Typical definitive host is a deer (Cervidae), but many other species from different families can be accidentally infected, for example sheep, goat or cattle. Very important role in the life cycle of F. magna has the first host - fresh water snail of the family Lymnaeidae. Three different life stages of F. magna, two of them with ability of reproduction - sporocysts and rediae develop in the body of snail. The third stage - cercaria is produced by rediae. Cercariae are able to escape from the snail, encyst and become infective for the definitive host. Since the second half of the 19th century many researchers studied the development of particular stages in the first intermediate host, but many characteristics of this process are still not fully understood. This thesis should reveal some of unanswered questions concerning to the reproduction and ontogenetic development of trematodes, which is presented on the examples of three organ systems - muscles, nerves and excretory system of rediae and cercariae of F. magna.

Trichobilharzia regenti is a nasal avian schistosome which has during the initial phase of infection an affinity to the nervous system. Larvae migrate through the central nervous system to the nasal mucosa of waterfowl, where they mature and reproduce. Until now this infection phase has been described only marginally. Adults are located in the nasal mucosa approximately from 13th to 24th day post infection. During this life phase, they migrate through the vascularized connective tissue and lay eggs, the presence of which has been detected in the tissue only. Maturation and hatching of miracidia occur in the tissue (unlike human schistosomes). The parasite causes inflammation, and the tissue is infiltrated with immune cells. Lymphocytes, granulocytes, macrophages, plasma cells and giant multi-nuclear cells were described by histological methods. The thesis is focused on a more detailed description of cellular immune response and histopathological changes of the tissue by means of histological stains, and antibody/lectin probes. The flukes were observed more frequently in the blood vessel lumen, together with a higher number of immune cells compared to the healthy duck. Infiltration by a high number of lymphocytes occurred in the tissue, the macrophages were frequently observed in clusters around the...

This work applies advanced sampling (mark-release-recapture) and comparative approaches addressing the patterns in composition, structure and variability of larval trematode communities in three species of gastropod molluscs (Lymnaea stagnalis, Planorbarius corneus and Radix auricularia) at two nested scales of community organisation in typical Central European eutrophic environments. Hypothesis-testing with the application of null-model analyses, logistic regression modelling and multivariate randomisation techniques, revealed determinants of transmission rates, levels of infection and community structure in freshwater snail hosts in Central Europe and elucidated the mechanisms linking the spatial and temporal environmental variability with the action of complex community assembly rules in freshwater pulmonate snails.