The role of tubificid oligochaetes in the transmission of Goussia carpelli.

Tubifex tubifex and Limnodrilus hoffmeisteri, fed intestinal tissue of carp containing oocysts of Goussia carpelli, produced infections in laboratory-reared carp. Sporocysts ingested by the tubificids released the sporozoites that were found to be motile in the intestinal contents and incorporated in intestinal cells of the oligochaetes. Tubificids remained infective for carp at least up to 57 days postexposure (PE). Tubificids were also able to transmit G. carpelli to carp that had recovered from a previous infection, whereas attempts of direct transmission of G. carpelli among these carp failed. Direct transmission to uninfected carp by fecal contamination was possible. Organisms from the pond plankton, benthic Limnadia sp., and chironomid larvae did not transmit G. carpelli to carp.