@PhdThesis{diss_mods_00003521, author = {Lehnert, Kristina}, title = {Prevalence, impact and molecular characterisation of parasites in harbour porpoises and harbour seals}, year = {2009}, publisher = {Christian-Albrechts-Universit{\"a}t zu Kiel}, address = {Kiel}, keywords = {Harbour porpoise; harbour seal; parasitology; Metastrongyloidea; life cycle; pathology; Schweinswal; Seehund; Parasitologie; Metastromgyloidea; Lebenszyklus; Pathologie}, abstract = {Parasitism is ubiquitous in wildlife, but little is known about the dynamics of parasitic infections and associated diseases in marine mammals. This thesis aimed to characterise the parasite fauna of harbour porpoises (Phocoena phocoena) and harbour seals (Phoca vitulina) to assess the impact on their health status and to improve the knowledge about the life history of their lungworm species. Parasitological investigations were carried out on harbour porpoises originating from the German North and Baltic Seas and the Norwegian North Sea. The parasites found in porpoises originated mainly from the respiratory tract and comprised four pseudaliid nematodes (Pseudalius inflexus, Torynurus convolutus, Halocercus invaginatus, Stenurus minor), one ascaridoid nematode (Anisakis simplex) and two trematodes (Campula oblonga, Pholeter gastrophilus). The finding of H. invaginatus was the first geographic record from German waters. Differences were found in the severity of the parasitic infection between stranded and bycaught animals as well as between porpoises from different areas. A correlation was shown between parasitic infection and observed lesions. Lungworm prevalence and intensity of infections increased with age suggesting horizontal transmission through the food web. The data also indicated that infections were accumulated with age and long‐lived. The occurrence of whale‐lice, Isocyamus delphinii (Crustacea: Amphipoda: Cyamidae), infestation was described in a stranded harbour porpoise. The emaciated animal had multiple, partially scarred wounds to which numerous small crustaceans were attached. The whale‐lice showed a significant sexual dimorphism and their population was male biased. The lesions in the lung were found to be the likely cause of death in this porpoise, and the ectoparasites were not diagnosed to be a major health threat to the animal. The skin wounds' origin remained unclear, but the lice seemed to be closely associated and dependent on the wounds of this host. In this first and unusual occurrence of I. delphinii on a harbour porpoise from German waters, the transmission was probably interspecific and skin wounds were likely the necessary means for the parasites to attach and remain on a porpoise. Eight species of parasites were collected from harbour seals from the German North Sea. Two anisakid nematodes (Pseudoterranova decipiens (sensu lato), Contracaecum osculatum (sensu lato) from the stomach, Otostrongylus circumlitus (Crenosomatidae) and Parafilaroides gymnurus (Filaroididae) from the respiratory tract, one filaroidid nematode (Acanthocheilonema spirocauda) from the heart, two acanthocephalans Corynosoma strumosum and C. semerme (Polymorphidae) from the intestine and the ectoparasite Echinophthirius horridus (Anoplura, Insecta) were found. Lungworm infection was the most prominent parasitological finding and secondary bacterial bronchopneumonia the most pathogenic lesion correlated with the parasites. Heavy nematode burdens in the respiratory tract were highly age‐related and more frequent in young seals. A positive correlation was observed between high levels of pulmonary infection and severity of bronchopneumonia. The prevalence of lungworms in this study was higher than in seals that died during the 1988/89 Phocine Distemper Virus epidemic, and prevalence of acanthocephalans and heartworms had decreased compared to findings from the die‐off. The metastrongyloid nematodes of porpoises and seals from German waters parasitising the respiratory tract were especially pathogenic and often caused secondary bacterial infections. In spite of the importance of lungworm disease for the health of wild populations and their clinical and epidemiological significance, the life cycle and biology of lungworms in the marine environment is still largely unknown. The ITS‐2 (rDNA) region of lungworms parasitising porpoises and seals were sequenced to characterise the different species. Molecular markers to identify larval nematode stages via in‐situ hybridisation in tissues of porpoise and seal prey were developed. Potential intermediate hosts from the North Sea were screened for larval stages of lungworms using the species‐specific traits of the ITS‐2. Histology and in‐situ hybridisation of tissue samples of flatfish showed larvae within the intestinal wall. Using larval ITS‐2 nucleotide sequences the nematode stages were identified as P. inflexus and P. gymnurus. Experimental infections of turbot (Psetta maxima) with live seal lungworm larvae (O. circumlitus) revealed second and third‐stage larvae of O. circumlitus in their intestinal tract. The results elucidated the life cycle of metastrongyloids of porpoises and seals and showed that they use vertebrate intermediate hosts. This thesis discovered new aspects of the life history of lungworm parasites of porpoises and seals by combining novel molecular techniques with methods from traditional parasitology. New information on parasite species and associated diseases in porpoises and seals improved the knowledge about the biology of parasites and hosts and our understanding of infection patterns.}, url = {https://macau.uni-kiel.de/receive/diss_mods_00003521}, file = {:https://macau.uni-kiel.de/servlets/MCRFileNodeServlet/dissertation_derivate_00002708/Diss_Lehnert2.pdf:PDF}, language = {en} }