Research of Bird Schistosomes
Trichobilharzia regenti - a neuropathogenic fluke
Trichobilharzia regenti is a neuropathogenic bird schistosome which has been discovered and described as a new species by our team in 1998. In addition to birds, the infectious larvae (cercariae) proved to penetrate also the skin of mammals and, therefore, T. regenti (neuro)pathogenicity is intensively investigated.
Etymology of T. regenti declared in the original description (Horak et al. 1998): "Regent is a governor of a kingdom/principality; the title was frequently used in South Bohemia (i.e. the area where the schistosome comes from) in the Middle Ages. At present the name represents a famous South Bohemian brewery (founded in 1379)". Introduction of the name of T. regenti was meant as an appreciation of the brewery.
Miracidia of T. regenti hatch directly in the nasal tissue of ducks (an exception within the family of Schistosomatidae). They leave the eggs (video 1 - the egg containing a miracidium), waiting for subsequent contact of the duck bill with water. If this happens, miracidia escape and search for intermediate snail hosts in water reservoirs. Cercariae of T. regenti develop asexually within snail intermediate hosts (video 2); mature cercariae escape via penetration of snail surface epithelia (video 3).
THREE MAIN RESEARCH STREAMS in the study of bird schistosomes (laboratory models: Trichobilharzia regenti, Trichobilharzia szidati) are in focus: (a) systematics/life cycles, (b) immune responses of snails and vertebrates, (c) biologically important parasite proteins - peptidases, lectins and hyaluronidases.
Immune responses of snails and vertebrates
• Snail hemocyte reactions against compatible and incompatible schistosome larvae
• Immune response in vertebrate skin; immune processes participating in cercarial dermatitis
• Inflammatory reactions in target tissues, histopathology of parasite migration within bird and mammalian bodies
• Screening for candidate antigens and introduction of specific immunodiagnosis
Biologically important parasite proteins
• Schistosome peptidases (mainly cathepsins) involved in skin penetration, tissue migration and digestion
• Hyaluronidases and lectins of bird schistosomes and their role in host-parasite interaction
• Morphology (incl. ultrastructure) and behavior of schistosome developmental stages
• Identification of natural/experimental intermediate and final hosts
Adults of nasal bird schistosomes live in the bill mucosa, where also mating and egg laying take place. Histopathologically, petechiae caused by worm migration and egg deposition may occur.
Workshops on Bird Schistosomes and Cercarial Dermatitis
From time to time, the scientists working on bird schistosomes organize a workshop. These events enable a valuable exchange of information.
List of Workshops on Bird Schistosomes and Cercarial Dermatitis
1st Workshop - Czech Republic, Dolni Vestonice, September 10-14, 2001
2nd Workshop - France, Annecy, June 16-18, 2003
3rd Workshop - Czech Republic, Rejckov-Kouty, July 6-10, 2009
(pdf version of abstracts, photo of participants)
Swimmer’s itch, also known as cercarial dermatitis, represents a common non-communicable waterborne cutaneous allergic disease which develops as a consequence of repeated infections by larval stages (cercariae) of schistosomatid ﬂukes. Swimmer’s itch is usually associated with swimming in recreational freshwater lakes, and mostly cercariae of avian schistosomes of the genus Trichobilharzia are reported as a source of infection. Bathing in the sea or brackish waters is rarely mentioned with respect to cercarial dermatitis.
Due to a higher number of reports on outbreaks, cercarial dermatitis may be regarded as an emerging disease.
(Schistosome Group Prague)
Cercaria of T. regenti penetrates a peripheral nerve isolated from a duck (left). The target tissue of T. szidati migration is the intestinal wall of ducks. Some of the eggs laid by females are trapped in the tissue; formation of granulomas can be noticed macroscopically as well as microscopically in tissue sections.
Confocal laser scanning microscopy can be used for characterization of different organs/tissues of Trichobilharzia. Using specific probes, we focus on organogenesis and stage-specific morphological features of T. regenti. For example, the presence of polymeric or oligomeric F-actin in the eggs, miracidia, cercariae and schistosomula is shown.