Parasitological and pathological findings in fin whales Balaenoptera physalus stranded along Italian coastlines

Mediterranean fin whales Balaenoptera physalus face many threats to their conservation, including both anthropogenic and natural issues. There are few records of the parasitic fauna of this species in this geographical area. To partially fill in this gap of knowledge, we investigated the presence and potential impact of parasitic diseases in Mediterranean fin whales. Seven animals stranded along Italian coastlines between 2006 and 2015 were submitted for necropsy and parasitological examination. The protozoan parasite Toxoplasma gondii was detected in 1 fin whale and, for the first time in mysticetes, it was successfully genotyped as a type II strain with 15 microsatellite markers. One crustacean (Pennella spp.) and 4 helminth taxa (Crassicauda boopis, Ogmogaster antarcticus, Tetrabothrius ruudi and Bolbosoma sp.) were detected and morphologically identified. Different degrees of ectoparasitism by adult P. balaenoptera were recorded. Immature stages of Pennella sp. were also detected in 2 animals and are described here for the first time in cetaceans. Infestation by C. boopis was confirmed or suspected in 5 cases. Parasitic thrombi, involving renal veins and caudal vena cava, and fibrosis of renal parenchyma were associated with C. boopis and likely resulted in some degree of renal dysfunction. Larval nematodes were found within foci of mesenteric endarteritis. Further research to evaluate the prevalence of this potentially fatal endoparasitosis in Mediterranean fin whales is warranted.