As the latter had a very low positive OD value on arrival, it may be concluded that this individual was already in the post-patency phase. of lungworm infected cattle, but further studies are needed to confirm this. Phylogenetic analyses of MSP sequences of different marine and terrestrial mammal parasitic nematodes revealed that lungworm MSP of the genus Dictyocaulus (superfamily Trichostrongyloidea) is more closely related to metastrongylid marine mammal lungworms than to trichostrongylid nematodes of terrestrial hosts. (Crenosomatidae) and (Filaroididae) of harbour seals (Lehnert et?al., 2005, Lehnert et?al., 2007, Siebert et?al., 2007). was found in the bronchi, in the right heart chamber, the and in the blood vessels of the liver (De Bruyn, 1933, Onderka, 1989, Claussen et?al., 1991, Measures, 2001, Lehnert et?al., 2007), while mainly parasitised the alveoles and bronchioles (Stroud and Dailey, 1978; Claussen et?al., 1991). Varying lungworm prevalence, up to 76%, was reported in harbour seals found in the German Wadden Sea (Claussen et?al., 1991, Lehnert et?al., 2007, Siebert et?al., 2007). Infections were age-related, with most infections occurring in young animals between two and 18 months of age. Harbour seals may start acquiring lungworm infections after nursing for four weeks and after a post-weaning fast of 15C17 days (Muelbert and Bowen, 1993, Ross et?al., 1994) when they start to consume prey species (Measures, 2001). Benthic fish were identified as potential intermediate hosts of lungworms (Dailey, 1970, Bergeron et?al., 1997a, Lehnert et?al., 2010); however, the complete TMI-1 life cycle is yet unknown. Lungworms in harbour seals can cause severe pathological changes, like obstruction of bronchial tubes, and are often accompanied by bacterial infections leading to severe bronchopneumonia and death (Measures, 2001, Lehnert et?al., 2007, Siebert et?al., 2007, Rijks et?al., 2008). Clinical symptoms include bronchospasm, anorexia, dehydration, and individual specimens can be observed in sputum (Bergeron et?al., 1997a, Measures, 2001). Lungworm infections are mainly reported from stranded harbour seals during post mortem examinations (Claussen et?al., 1991, Siebert et?al., 2007, Rijks et?al., 2008), but those data can be biased by different influences such as age, diseases and anthropogenic activities (Claussen et?al., 1991, Measures, 2001, Siebert et?al., 2007). Diagnosis in living seals is difficult, as detecting lungworm larvae in faeces has limited sensitivity (Schnieder, 1992). Collecting harbour seal faeces is logistically challenging and assigning samples to individual free ranging seals is not feasible. Due to the difficulties in diagnosing lungworm infections in living seals, prevalence data in the free-ranging harbour seal populations is missing. Therefore, an existing ELISA for immunodiagnosis of the bovine lungworm (Schnieder, 1992, von Holtum et?al., 2008) was adapted to harbour and grey seals with a resulting sensitivity of 98% and a specificity of 100% (Ulrich et?al., 2015). The ELISA represents a reliable method for diagnosing lungworm antibodies in serum samples of free-ranging harbour seals. Recombinant major sperm protein (MSP), a protein family occurring in nematode sperm only (Klass and Hirsh, 1981, Ward et?al., 1988) serves as diagnostic antigen. Information about the molecular structure of MSP from nematodes infecting harbour seals and harbour porpoises is missing. Previous phylogenetic analyses within the Metastrongyloidea have been performed on the base of large-subunit and small-subunit ribosomal (r)RNA (Carreno and Nadler, 2003), the ITS-2 region of rDNA (Lehnert et?al., 2010) and the 18S and 28S rRNA (Chilton et?al., 2006). Those analyses confirmed the close relationship of marine mammal lungworms within their superfamily Metastrongyloidea, an evolutionary old group that was derived from the terrestrial ancestors of seals and porpoises (Anderson, 1984, Carreno and Nadler, 2003). The aim of this study was to assess lungworm seroprevalence in free-ranging harbour seals in different age groups. Furthermore, TMI-1 consecutive serum samples of harbour seals in rehabilitation were analysed to obtain first information on the persistence of serum anti-lungworm-MSP antibodies. Additionally, MSP genes from different TMI-1 nematodes infecting harbour porpoises and harbour seals were identified and sequenced to explore phylogenetic relationships between marine and terrestrial parasitic nematodes. 2.?Material and methods 2.1. ELISA 2.1.1. Age determination of harbour seals The approximate age of sampled harbour seals was determined and sorted in age groups, considering sampling date, body-length and body-weight. In young seals, navel and canine development was additionally considered. Age group (AG) 1 included harbour seals from birth to six weeks of age, AG 2 harbour seals from six weeks to six months, AG 3 from six to 18 months and AG 4 above 18 months of age. 2.1.2. Sera of free-ranging harbour seals All experimental procedures involving harbour seals were approved by Mouse monoclonal to TEC the Ministry of Energy, Agriculture, the Environment and Rural Areas of the federal state Schleswig Holstein, Germany [permit number: TMI-1 V312-72241.121-19 (70-6/07)], the Danish Nature Agency (SNS-3446-00054 and SN 2001-34461/SN-0005) and the Animal Welfare.