title: Phocine distemper virus (PDV) seroprevalence as predictor for future outbreaks in harbour seals.
abstract: Phocine distemper virus (PDV) infections caused the two most pronounced mass mortalities in marine mammals documented in the past century. During the two outbreaks, 23,000 and 30,000 harbour seals (Phoca vitulina), died in 1988/1989 and 2002 across populations in the Wadden Sea and adjacent waters, respectively. To follow the mechanism and development of disease spreading, the dynamics of Morbillivirus-specific antibodies in harbour seal populations in German and Danish waters were examined. 522 serum samples of free-ranging harbour seals of different ages were sampled between 1990 and 2014. By standard neutralisation assays, Morbillivirus-specific antibodies were detected, using either the PDV isolate 2558/Han 88 or the related canine distemper virus (CDV) strain Onderstepoort. A total of 159 (30.5%) of the harbour seals were seropositive. Annual seroprevalence rates showed an undulating course: Peaks were seen in the post-epidemic years 1990/1991 and 2002/2003. Following each PDV outbreak, seroprevalence decreased and six to eight years after the epidemics samples were tested seronegative, indicating that the populations are now again susceptible to new PDV outbreak. After the last outbreak in 2002, the populations grew steadily to an estimated maximum (since 1975) of about 39,100 individuals in the Wadden Sea in 2014 and about 23,540 harbour seals in the Kattegat area in 2013. A re-appearence of PDV would presumably result in another epizootic with high mortality rates as encountered in the previous outbreaks. The current high population density renders harbour seals vulnerable to rapid spread of infectious agents including PDV and the recently detected influenza A virus.
authors.affiliation: Institute of Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine, Hannover, Foundation, Werftstrasse 6, 25761 Buesum, Germany. Electronic address: eva.ludes-wehrmeister@tiho-hannover.de.
authors.forename: Eva
authors.initials: E
authors.lastname: Ludes-Wehrmeister
authors.affiliation: Institute of Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine, Hannover, Foundation, Werftstrasse 6, 25761 Buesum, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Dupke
authors.affiliation: O.I.E., FAO and National Reference Laboratory for Avian Influenza, Institute of Diagnostic Virology, Friedrich Loeffler Institut, Suedufer 10, D-17493 Greifswald-Insel Riems, Germany.
authors.forename: Timm C
authors.initials: TC
authors.lastname: Harder
authors.affiliation: Department of Pathology, University of Veterinary Medicine Hannover, Foundation, Buenteweg 17, 30559 Hannover, Germany.
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Baumgärtner
authors.affiliation: Institute of Virology, University of Veterinary Medicine Hannover, Foundation, Buenteweg 17, 30559 Hannover, Germany.
authors.forename: Ludwig
authors.initials: L
authors.lastname: Haas
authors.affiliation: Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
authors.forename: Jonas
authors.initials: J
authors.lastname: Teilmann
authors.affiliation: Department of Bioscience, Aarhus University, Frederiksborgvej 399, DK-4000 Roskilde, Denmark.
authors.forename: Rune
authors.initials: R
authors.lastname: Dietz
authors.affiliation: Fisheries and Maritime Museum, Tarphagevej 2, 6710 Esbjerg V, Denmark.
authors.forename: Lasse F
authors.initials: LF
authors.lastname: Jensen
authors.affiliation: Institute of Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine, Hannover, Foundation, Werftstrasse 6, 25761 Buesum, Germany. Electronic address: ursula.siebert@tiho-hannover.de.
authors.forename: Ursula
authors.initials: U
authors.lastname: Siebert
mesh_terms: D000367:Age Factors; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood; D003198:Computer Simulation; D004196:Disease Outbreaks; D004216:Distemper / Q000097:blood / Q000453:epidemiology* / Q000276:immunology; D018104:Distemper Virus, Phocine / Q000276:immunology; D056724:Immunity, Humoral; D046049:Phoca / Q000821:virology*; D011156:Population Density; D016036:Seroepidemiologic Studies
chemical_list: D000914:Antibodies, Viral
keywords: Canine distemper virus; Common seal; Epidemic; Harbour seal; Morbillivirus antibodies; Phocine distemper virus