Biostatic activity of piscine serum and mucus on myxozoan fish infective stages.

Since the basis of host specificity in Myxozoa, i.e. the differential disposition and extinction of erroneously penetrated myxozoan infective stages in non-susceptible fish hosts, remains puzzling, we aimed to explore the role of the innate immune system in this issue.

No shot in the dark: myxozoans chemically detect fresh fish.

This work reports the discovery of an hitherto unknown chemical recognition trait enabling a parasitic life cycle in aquatic habitats. We believe this is the first record of a natural, host-derived chemical molecule identified as a recognition cue for the phylum Myxozoa. The actinospores of these parasites attach to fish hosts via polar filaments that are extruded upon mechanical stimulation after preceding recognition of a chemical trigger contained in surface mucus.

Penetration of cercariae into the living human skin: Schistosoma mansoni vs. Trichobilharzia szidati.

We studied the skin invasion of Schistosoma mansoni cercariae by placing gamma-irradiated and nonirradiated cercariae onto the living human skin and timing the behavior of 53 individuals. The skin invasion of S. mansoni was less efficient compared to the bird schistosome Trichobilharzia szidati.

Schistosoma mansoni: human skin ceramides are a chemical cue for host recognition of cercariae.

Schistosoma mansoni cercariae recognize the human host with a sequence of behavioral responses particularly to chemical host cues. After attaching to the skin surface, cercariae are stimulated by so far unknown skin components to hold enduring contact with the skin and to start creeping towards entry sites. We studied the chemical stimulus of human skin for the cercarial enduring contact response by fractionation of human and pig skin surface extracts and offering the fractions to the cercariae via membrane filters.

Selection of the host's habitat by cercariae: from laboratory experiments to the field.

The distribution of cercariae was studied in 18-cm-sized cuvettes under different lighting conditions, in Plexiglas cylinders (80 cm high) vertically placed in a pond, and when swimming freely in a pond. The vertical distribution and the effect of light intensity on it were relatively similar in the cuvettes, in the cylinders, and in the pond. Each of the species (Schistosoma mansoni, Diplostomum spathaceum, Echinostoma caproni, and Pseudechinoparyphium echinatum) showed its individual distribution within the water column, with distinct changes during the time after shedding.

Chemical attractants of human skin for swimming Schistosoma mansoni cercariae.

Cercariae of Schistosoma mansoni approach towards their host's skin with a chemokinesis. They respond to human skin extracts by inserting shifts between backward and forward swimming and therewith increase the rate of change of direction (RCD). We identified the host attractants by fractionating human skin surface extracts, exposing the fractions and chemicals to the cercariae and recording cercarial swimming by video tracking.

Swimming behaviour of Schistosoma mansoni cercariae: responses to irradiance changes and skin attractants.

The swimming behaviour of many cercarial species is governed by sensitive responses to light and dark stimuli. We studied the effect of irradiance changes on swimming behaviour of Schistosoma mansoni cercariae and found only insignificant responses. Decreasing light intensity results in a weak tendency of the cercariae to start swimming movements, and increasing light intensity tends to inhibit the start of swimming.

Larval trematodes in freshwater molluscs from the Elbe to Danube rivers (Southeast Germany): before and today.

Studies on life cycles of trematodes have a long tradition in Germany; (Odening 1978) listed a total of 177 trematodes, which can potentially complete their life cycles in German inland waters. However, almost no recent data on the occurrence of larval stages in molluscs are available. Therefore, a survey of trematodes in Southeast Germany was carried out in 2004.

Parasitic worms: strategies of host finding, recognition and invasion.

Many parasitic worms enter their hosts by active invasion. Their transmission success is often based on a mass production of invasive stages. However, most stages show a highly specific host-finding behaviour.

Life cycle studies of Myxobolus parviformis sp. n. (Myxozoa: Myxobolidae) from bream.

We experimentally followed the life cycle of Myxobolus parviformis sp. n., a myxozoan parasite from the gills of common bream Abramis brama L.

Snail odour-clouds: spreading and contribution to the transmission success of Trichobilharzia ocellata (Trematoda, Digenea) miracidia.

Chemical communication among freshwater organisms is an adaptation to improve their coexistence. Here,we focus on the chemical cues secreted by the freshwater gastropod Lymnaea stagnalis, which are known to stimulate behavioural responses of Trichobilharzia ocellata (Plathelminthes, Digenea, Trematoda) miracidia. Such responses are commonly claimed to influence transmission positively, but in response to chemical cues miracidia randomly change their swimming direction.

Behavioural strategies used by the hookworms Necator americanus and Ancylostoma duodenale to find, recognize and invade the human host.

The infective third-stage larvae of the hookworms Necator americanus and Ancylostoma duodenale infect their human hosts by active skin invasion, but A. duodenale is in addition capable of oral infection. The behaviour of the larvae when crawling on surfaces has already been described.

Infective larvae of the human hookworms Necator americanus and Ancylostoma duodenale differ in their orientation behaviour when crawling on surfaces.

The infective third stage larvae of hookworms infect their hosts by active skin invasion, and they find and recognize their hosts by the behavioural phases of activation, directed crawling, and penetration. Here we analyse the orientation of the infective larvae of the human hookworms Necator americanus and Ancylostoma duodenale when crawling on surfaces. Their behaviour differed from that of the larvae of the dog hookworm Ancylostoma caninum, but the two species also differed from each other.

Navigation within host tissues: Schistosoma mansoni and Trichobilharzia ocellata schistosomula respond to chemical gradients.

After penetration of human or duck host's skin schistosomula of Schistosoma mansoni and Trichobilharzia ocellata migrate parallel to the surface in the epidermis, then they enter the dermis and venules prior to further migration. This study focuses on potential behavioural mechanisms and host cues which may enable this navigation within host tissues. We stimulated cercariae to penetrate into agar substrates and to transform to schistosomula, and analysed their orientation behaviour within chemical concentration gradients.

Detection of Schistosoma mansoni cercariae in plankton samples by PCR.

A PCR assay on the basis of a tandemly repeated DNA sequence was employed for the detection of Schistosoma mansoni in artificial plankton samples. It was highly specific, since as few as 1fg DNA from this species were sufficient to obtain a clear signal, while 10pg DNA of Schistosoma rodhaini were required and no PCR products were obtained with even 10ng DNA of planktonic organisms and any other trematode species tested. In areas with transmission of different Schistosoma species 10pg DNA should be used for amplification, which would allow detection of 20 S.

Ultrastructure of pigmented and unpigmented photoreceptors in cercariae of Trichobilharzia ocellata (Plathelminthes, Trematoda, Schistosomatidae): evidence for the evolution of parasitism in Neodermata.

The lens-covered pigment cup ocelli in free-swimming cercariae of Trichobilharzia ocellata were re-examined and the differentiation of the lenticular elements was studied in cercariae still enclosed in sporocysts. Each eye consists of a single rhabdomeric sensory cell, a single cup cell harboring pigment granules and the lens. This lens is developed step by step by the fusion of numerous dark platelets not enclosed by a bordering membrane.

Detection of bird schistosomes in lakes by PCR and filter-hybridization.

Many lakes around the world are contaminated with bird schistosome cercariae, which penetrate into human skin, causing an itching dermatitis called "swimmers' itch." Bathers could be forewarned from exposure to the larvae and ecological examinations could be performed, when a sensitive method to detect the parasites in aquatic systems, where lots of organisms hinder microscopic examinations, would be available. For this purpose we cloned, sequenced, and analyzed a 396 bp tandem repeated DNA sequence from Trichobilharzia ocellata (ToSau3A), and employed it for developing molecular detection assays.

Diplostomum spathaceum cercariae respond to a unique profile of cues during recognition of their fish host.

During its normal life cycle, Diplostomum spathaceum cercariae attach to and invade fish intermediate hosts. They are also known to attach to various other aquatic animals in response to water currents, touch and carbon dioxide. The purpose of this study was to identify the specific stimuli used by D.