Veterinary session

Marine mammals are susceptible to many parasitic infections that can have an influence on their health and ability to survive in their environments, especially nowadays with increasing threats and many cetacean species being endangered or even at risk of extinction.

This study presents the results of a comprehensive molecular analysis of endoparasites in marine mammals, including the Fin Whale (Balaenoptera physalus), the Common Bottlenose Dolphin (Tursiops truncatus), the Short-beaked Common Dolphin (Delphinus delphis), the Striped Dolphin (Stenella coeruleoalba), the Harbour porpoise (Phocoena phocoena), and the Long-finned Pilot Whale (Globicephala melas), found in southern Spain including the strait of Gibraltar. The aim of this study is to investigate parasitic infections in marine mammals and thereby contribute to the protection of these endangered species.

The fieldwork included the collection of biological samples from several cetacean species that were found dead and stranded in southern Spain. The necropsies were conducted in the Campo de Gibraltar, Algeciras where muscle, skin and internal organ tissue samples as well as multicellular parasites were collected as frozen or ethanol-soaked specimens. Tissue and parasite samples were analyzed with molecular methods including conventional PCR for the presence of acanthamoebae, trypanosomes, piroplasms, haemogregarines, cystogenic coccidia, rickettsiae, anaplasmas and bartonellae. PCR products of positive samples were sent for sequencing to the Biotechnology Research Institute in Gödöllő, Hungary. In all PCR-positive samples the presence of T. gondii was confirmed, with a 100% sequence match to GenBank data of this species in multiple organs (lungs, muscle, cerebellum, and encephalon) of a single D. delphis.

According to our best knowledge, these findings reveal and confirm, for the first time globally, the presence of Toxoplasma gondii DNA in the Short-beaked Common Dolphin (D. delphis) as previous studies only confirmed the presence of anti-T. gondii antibodies or T. gondii antigens with immunological methods. Furthermore, the study provides insights into the occurrence of other parasites in cetaceans found in southern Spain, in this way helping to understand ecological condition of ecosystems and cetacean populations in the strait of Gibraltar. The results contribute to our knowledge on the epidemiology of T. gondii and underline the importance of continuing research and monitoring of global and Mediterranean cetacean populations.