Differential infectivity of Transversotrema patialense for naive fish.

The discovery of Transversotrema patialense cercariae in an aquarium harboring tropical fish triggered the present study. The purpose was to estimate the potential range of infection of local freshwater and fishpond populations by T. patialense. Experimental infection of T. patialense differed among 3 species employed: 76.5% for Tilapia zillii, 37.8% for Gambusia affinis, and none for 2 varieties of Cyprinus carpio. These patterns of infectivity are different from those published previously for T. patialense infections, and they may be attributed to the origin of the fish (temperate water vs. tropical and subtropical waters) and the size of their scales. In G. affinis, but not in the other species, worm load and fish length were closely related, and the left side harbored heavier worm burdens than the right side. Taken together, these results suggest that imported T. patialense may spread to various indigenous natural and cultured fish populations, with ensuing potential harm to these populations.