Diphyllobothrium dendriticum and Diphyllobothrium latum in fishes from southern Argentina: association, abundance, distribution, pathological effects, and risk of human infection.

Diphyllobothrium dendriticum and Diphyllobothrium latum are reported for the first time from Argentina. The following species from Lake Moreno (southern Argentina) were studied to determine whether plerocercoids were present: 11 brook trout (Salvelinus fontinalis), 32 perca (Percichthys sp.), 21 pejerrey (Patagonina hatcheri), and 114 rainbow trout (Oncorhynchus mykiss). Brook trout harbored both species (27.3% prevalence of D. dendriticum and 9.0% of D. latum); perca harbored only D. latum (18.7% prevalence); pejerrey were not infected and rainbow trout also harbored both species, with significant association. Diphyllobothrium latum was less abundant (1.4 plerocercoids/fish, 28.0% prevalence) than D. dendriticum (7.2 plerocercoids/fish, 57.8% prevalence) implying a lower health risk for humans. For both parasites, rainbow trout seem to be more important than the other host species studied. There is no evidence that either of the species is more harmful to the host. The lack of significant weight variation of the liver as related to intensity of infection strongly suggests that competition for energy is not an important aspect of the host pathology.