Descriptive epizootiology of parasites from the 1991-2005 mass strandings of rough-toothed dolphins (Steno bredanensis) in the Southeastern United States

Parasites are commonly encountered during necropsies of mass stranded wild dolphins, however, due to a lack of standardized investigation and collection techniques, they are not always systematically described. This retrospective study describes parasites identified in 166 roughtoothed dolphins (Steno bredanensis) that mass stranded along the Florida coastline between 1991 and 2005. Encountered parasites were separated by type (i.e. trematode, nematode, cestode, crustacean, protozoan, and unknown) and burden (mild, moderate or severe, and singular infection or multiple infections). Variables of interest that could potentially have an effect on parasite type and burden were sex, age class, length range, and geographic region. Of the mass stranded S. bredanensis, 94.9% exhibited parasitic infections, and the most commonly identified parasites were trematodes, followed by nematodes and larval cysts of cestodes. Most of the stranded animals identified with parasitic infections presented with either 1 infection in 1 organ or 2+ infections in multiple organs. Although, each stranding event was represented by a distinctive set of parasites, it is not clear as to whether or not this was a result of the time of the stranding (varying by months and years), the geographic stock of the animals, the water temperature, or possibly the prey type. Sex, age class, and length range of the animals had no effect on the number of parasitic infections or parasite type exhibited by an individual, although females were the dominant sex represented at all strandings. Serendipitous collection of information from post-mortem examination by different evaluators makes it difficult to thoroughly interpret the data, and future efforts should be expanded upon and standardized