Abstract
Infection of certain species of cyprinid fish with the plerocercoid larva of the cestode Ligula intestinalis is accompanied by a host tissue response.The tissue reaction is evident in roach Rutilus rutilus as young as three months. An initial cellular infiltration is followed by the laying down of sheets of connective tissue. A case of calcification is described in a single infected rudd Scardinius erythrophthalmus.