title: Toxoplasma gondii in stranded marine mammals from the North Sea and Eastern Atlantic Ocean: Findings and diagnostic difficulties.
abstract: The occurrence of the zoonotic protozoan parasite Toxoplasma gondii in marine mammals remains a poorly understood phenomenon. In this study, samples from 589 marine mammal species and 34 European otters (Lutra lutra), stranded on the coasts of Scotland, Belgium, France, The Netherlands and Germany, were tested for the presence of T. gondii. Brain samples were analysed by polymerase chain reaction (PCR) for detection of parasite DNA. Blood and muscle fluid samples were tested for specific antibodies using a modified agglutination test (MAT), a commercial multi-species enzyme-linked immunosorbent assay (ELISA) and an immunofluorescence assay (IFA). Out of 193 animals tested by PCR, only two harbour porpoise (Phocoena phocoena) cerebrum samples, obtained from animals stranded on the Dutch coast, tested positive. The serological results showed a wide variation depending on the test used. Using a cut-off value of 1/40 dilution in MAT, 141 out of 292 animals (41%) were positive. Using IFA, 30 out of 244 tested samples (12%) were positive at a 1/50 dilution. The commercial ELISA yielded 7% positives with a cut-off of the sample-to-positive (S/P) ratio≥50; and 12% when the cut-off was set at S/P ratio≥20. The high number of positives in MAT may be an overestimation due to the high degree of haemolysis of the samples and/or the presence of lipids. The ELISA results could be an underestimation due to the use of a multispecies conjugate. Our results confirm the presence of T. gondii in marine mammals in The Netherlands and show exposure to the parasite in both the North Sea and the Eastern Atlantic Ocean. We also highlight the limitations of the tests used to diagnose T. gondii in stranded marine mammals.
authors.affiliation: Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium.
authors.forename: Norbert
authors.initials: N
authors.lastname: van de Velde
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium; Department of Public Health and Surveillance, Scientific Institute of Public Health (WIV-ISP), Brussels, Belgium. Electronic address: brechtdv@gmail.com.
authors.forename: Brecht
authors.initials: B
authors.lastname: Devleesschauwer
authors.affiliation: Wageningen IMARES - Institute for Marine Resources and Ecosystem Studies, Den Helder, The Netherlands.
authors.forename: Mardik
authors.initials: M
authors.lastname: Leopold
authors.affiliation: Viroscience, Erasmus Medical Centre, Rotterdam, The Netherlands.
authors.forename: Lineke
authors.initials: L
authors.lastname: Begeman
authors.affiliation: Utrecht University, Faculty of Veterinary Medicine, Dept. Pathobiology, The Netherlands.
authors.forename: Lonneke
authors.initials: L
authors.lastname: IJsseldijk
authors.affiliation: Utrecht University, Faculty of Veterinary Medicine, Dept. Pathobiology, The Netherlands.
authors.forename: Sjoukje
authors.initials: S
authors.lastname: Hiemstra
authors.affiliation: Utrecht University, Faculty of Veterinary Medicine, Dept. Pathobiology, The Netherlands.
authors.forename: Jooske
authors.initials: J
authors.lastname: IJzer
authors.affiliation: Scottish Marine Animal Stranding Scheme, SAC Consulting. Veterinary Services, Drummondhill, Inverness, IV2 4JZ Scotland, UK.
authors.forename: Andrew
authors.initials: A
authors.lastname: Brownlow
authors.affiliation: Scottish Marine Animal Stranding Scheme, SAC Consulting. Veterinary Services, Drummondhill, Inverness, IV2 4JZ Scotland, UK.
authors.forename: Nicholas
authors.initials: N
authors.lastname: Davison
authors.affiliation: Royal Belgian Institute of Natural Sciences (RBINS), Ostend, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Haelters
authors.affiliation: Department of Morphology and Pathology, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium.
authors.forename: Thierry
authors.initials: T
authors.lastname: Jauniaux
authors.affiliation: Institute for Terrestrial and Aquatic Wildlife Research, University of Veterinary Medicine Hannover, Büsum, Germany.
authors.forename: Ursula
authors.initials: U
authors.lastname: Siebert
authors.affiliation: Department of Virology, Parasitology and Immunology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium; Department of Biomedical Sciences, Institute of Tropical Medicine, Antwerp, Belgium.
authors.forename: Pierre
authors.initials: P
authors.lastname: Dorny
authors.affiliation: National Reference Laboratory for Toxoplasmosis, Department of Communicable and Infectious Diseases, Scientific Institute of Public Health (WIV-ISP), Brussels, Belgium.
authors.forename: Stéphane
authors.initials: S
authors.lastname: De Craeye
mesh_terms: D000372:Agglutination Tests / Q000592:standards; D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood; D059001:Aquatic Organisms / Q000469:parasitology*; D001267:Atlantic Ocean / Q000453:epidemiology; D010872:Caniformia / Q000469:parasitology; D002591:Cetacea / Q000469:parasitology; D016054:DNA, Protozoan / Q000032:analysis; D003955:Diagnostic Tests, Routine / Q000592:standards*; D004797:Enzyme-Linked Immunosorbent Assay / Q000592:standards; D005455:Fluorescent Antibody Technique / Q000592:standards; D008322:Mammals / Q000469:parasitology*; D009659:North Sea / Q000453:epidemiology; D010041:Otters / Q000469:parasitology; D016133:Polymerase Chain Reaction / Q000592:standards; D016036:Seroepidemiologic Studies; D014122:Toxoplasma / Q000235:genetics / Q000276:immunology / Q000502:physiology; D014124:Toxoplasmosis, Animal / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology
chemical_list: D000913:Antibodies, Protozoan; D016054:DNA, Protozoan
keywords: ELISA; IFA; MAT; Marine mammals; PCR; Seroprevalence; Toxoplasma gondii