Flying across Europe: the case of the spread of Chaunocephalus ferox on a black stork ( Ciconia nigra ).

The annual migration of birds involves a very large number of inter-continental and intra-continental movements in which thousands of bird species participate. These migrations have been associated with the spread of pathogens worldwide, including bacteria, viruses and parasites. This study describes the case of a black stork ( Ciconia nigra ) that was ringed at the nest in Latvia and died five months later in the south-east of the Iberian Peninsula. Post-mortem examination revealed that the cause of death was electrocution. In addition, a massive infection by the trematode Chaunocephalus ferox (Digenea: Echinostomatidae) causing severe granulomatous lesions throughout the small intestine was detected. This is the first report of C. ferox infection in a black stork in the Iberian Peninsula, a trematode that, due to the severe lesions it causes, can affect the health of C. ferox -infected wild birds, particularly in severely infected long-distance migrants. The dispersal of platyhelminths associated with migratory birds is discussed. After the ringing at the nest, the black stork was sighted in Central Europe one month before its capture, and the trematodes found by necropsy were mostly mature adults. Consequently, we estimate that this juvenile animal acquired the infection during its migration in a European area other than the Iberian Peninsula, evidencing a long-distance parasite spread through its migratory host. Our study highlights that bird ringing can be used to understand the epidemiological implications that bird migratory behaviour may have on the dispersal of parasites.