1. Overview Schistosomes have achieved first position among parasitic helminths, because some of them are the etiological agents of a serious human parasitic disease, schistosomiasis, which affects over 200 million people in tropical and subtropical countries (WHO, 2001). Other schistosomatids, such as the bird flukes of the genus Trichobilharzia, have also implications for human health. Although they can mature only in specific hosts (birds), their invasive larvae - cercariae - are able to penetrate also human skin due to chemical signals similar to those present on bird skin (Haas and van de Roemer 1998). Repeated infections result in an inflammatory reaction of the skin called cercarial dermatitis. Due to the increasing number of outbreaks all around the world, cercarial dermatitis is cons disease (Kolářová 2007idered as re-emerging ; Larsen et al. 2004). Among schistosomes, Trichobilharzia regenti is the only species described so far having a unique migration route within vertebrate hosts: after penetration of the skin, the invasive larvae enter peripheral nerves and continue via the spinal cord and central nervous system to the nasal cavity of birds, causing neuromotor disorders or paralyses of birds and even experimental mammals (Hrádková...

The parasites are one of the most important factors that shape relationships in the nature. This thesis deals mainly with developmental stages of trematodes (Platyhelmintes: Trematoda), especially the cercariae of so-called Schistosomes and sporocysts of Leucochloridium paradoxum, as well as with and their intermediate host - freshwater snails. Introductory chapters are focused on general introduction into the topic, such as basic terminology or occurrence issue of trematodes (mainly schistosomes) in the world and in the Czech Republic. In order to determine larval stages of flukes and their morphological types, the research was conducted in four Prague localities with known presence of aquatic snails. Only in one site, Kunratická tůň Pond, the constant presence of echinostomous cercariae (and in lesser extent also furcocercariae) in Radix labiata was recorded during summer season of 2015. In small pond in the Botanical Garden of the Natural Sciences Faculty of Charles University and in Modřanské tůně Ponds, xiphidocercarie in Lymnaea stagnalis were found. No cercarie were detected in the pond in the Genetic garden of Charles University. The presence of Leucochloridium paradoxum in the European Amber Snail Succinea putris was confirmed in the vicinity of Modřanské tůně Ponds. The verified...

This thesis aims to explore the larval development of a bird fluke Trichobilharzia regenti in its intermediate hosts, as well as the processes of differentiation of its embryonal cells and the differentiation between sporocystogenesis and cercariogenesis in sporocysts, with the ultimate goal to find out whether it is possible to find multiple generations of daughter sporocysts throughout the development of avian schistosomes in the intermediate hosts, just like in the case of human schistosomes of genus Schistosoma. Five developmental stages of daughter sporocysts, and ten developmental stages of cercariae have been defined. The first developmental stage in both larvae is the germinal cell. It divides and gives rise to a cell agregate. Afterwards an envelope (primitive epithelium) is formed around the embryo and subsequently, the embryo elongates. At this stage, the development of the two larvae undergoes different pathways. We can distinguish daughter sporocyst from cercaria in the phase, when the tegument is completed. The daughter sporocyst acquires characteristic vermiform appearance, and its body cavity contains plenty of germinal cells. For cercariae with an developed tegument, presence of the penetration glands is characteristic. Key words: Trichobilharzia regenti, germinal cells, mother...

Cercarial dermatitis (CD) is manifested as a strong itchy rash that usually occurs after bathing in the natural water bodies where it makes recreation uncomfortable. As a consequence, the natural swimming areas and be closed because of inconvenient water quality, what subsequently leads to the financial losses. The infection can also affect people working in the natural water bodies as lifeguards (at the natural swimming areas), people monitoring water organisms or water quality etc.). Nowadays, CD in Czech Republic occurs more frequently than in the past. For this reason, the topic of avian schistosomes and CD is very attractive not only for scientists, but newly also for employees of hygienic stations and health institutes. Based on the Act No. 258/2000 Coll. on protection of public health and related executive Decree No. 238/2011 Coll. approved this year their duty will be regular monitoring of official natural swimming areas for causative agents of CD. For the comprehensive overview about the occurrence of the avian schistosomes and CD, up to now, at the localities in the Czech Republic the specialized overview map with the marked catches of avian schistosomes and CD was created in the program ArcGIS Online. This map was made with use the records obtained from the scientific articles, final...

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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...

Helminth neuroinfections represent a serious health issue, but the mechanisms of the host immune response often remain neglected despite the fact they might contribute to pathogenesis. This is partly due to the unavailability of clinical samples and the lack of suitable laboratory models. Herein, I focused on the characterization of several aspects of the immune response of mice infected with the neuropathogenic avian schistosome Trichobilharzia regenti. After the percutaneous infection of mice (accidental hosts), most T. regenti schistosomula are entrapped and eliminated in the skin, but the parasite antigens initiating the protective immune reaction are not known. Our in vitro experiments revealed that T. regenti cathepsin B2, a cysteine peptidase used for the skin penetration, activates bone marrow-derived dendritic cells much stronger than the parasite homogenate, suggesting its role in initiating the mixed type1/2 host immune response. However, some schistosomula manage to escape from the skin and continue their migration to the spinal cord. Here they crawl preferentially within the white matter which we demonstrated by the robust 3D imaging techniques, ultramicroscopy and micro-CT. The invasion of the spinal cord is accompanied by striking hypertrophy of astrocytes and microglia. We showed...