Parasitic helminths are invertebrate animals from various taxa, e.g. round worms (Nematoda), spiny-headed worms (Acanthocephala), tape worms (Cestoda), monogenean and parasitic flukes (Trematoda). They are endoparasites and live within their host in various locations. Most species parasitize the intestine; however, virtually every inner organ can be colonized by helminths, depending on their specialization (liver: liver fluke; lung: lung worms; lymphatic organs, blood, skin: various filarioid nematodes). Beside their preferences for specific organs, parasitic worms also have a distinct host preference. Some helminths have a broad host range, whereas others are only able to parasitize a single host species. As a consequence the extinction of a vertebrate host species would be accompanied by the extinction of several parasitic helminth species.

Most helminthes are highly adapted and long-living. Due to their ubiquitous distribution and the large number of species their importance as pathogens should not be underestimated.

Although there is a sound knowledge about parasitic worms of humans, some pets and livestock there is a lack of information about parasitic helminths in Austrian wild animals. In addition, many helminth species have only few morphological characteristics and are therefore difficult to determine to the species level, or can only be specified in certain life-cycle stages. For these cases, molecular barcoding technology is also of immediate practical importance.

Within the pilot-project ABOL, conducted at the University of Veterinary Medicine, Vienna in collaboration with the Museum of Natural History in Vienna and other Universities in Austria, we try to give a first overview on the species spectrum of parasitic helminths in Austria. Because of the large number of species the main focus within the pilot-study is on parasitic worms of fish, as well as domestic animals and their closest relatives among native wildlife.