Unusually long lungworms from the Dutch North Sea: Characterisation of Parafilaroides gymnurus from eastern Atlantic common seals. Parafilaroides gymnurus characterisation

Lungworms are responsible for the foremost disease of eastern Atlantic common seals in the Dutch North Sea. A recent increase in lungworm admissions to a Dutch rehabilitation centre and initial observations that Parafilaroides sp. adults were extremely long, prompted us to ask whether these worms were as expected, P. gymnurus. We therefore performed a morphological and molecular study on a large number of adult Parafilaroides sp. to characterize the species from this host in the Dutch North Sea. Although these worms were, as expected, Parafilaroides gymnurus, the females were unusually long for this species. We determined that there was a strong plasticity in body length of female P. gymnurus between different seal host species, geographic locations (western Atlantic versus eastern Atlantic) and over time in the eastern Atlantic common seal (current time compared to 1899). We speculate that intraspecific genetic differences in P. gymnurus, parasite-host compatibility and the environment within the host could play a role.