ACQUISITION OF RESISTANCE AGAINST FASCIOLA-GIGANTICA BY INDONESIAN THIN TAIL SHEEP

The plasma levels of GLDH and the dynamics of development of the numbe rs of surface lesions on livers, and numbers of parasites, within two to three weeks of a challenge infection, indicated that the major comp onent of the high resistance of Indonesian thin tail (ITT) sheep again st Fasciola gigantica was acquired, and acted against juvenile parasit es. Few parasites reached the livers of ITT (exposed) sheep, but many had been inhibited, probably in the wall of the jejunum. ITT (naive) s heep showed some resistance, compared with control Merino sheep, by th ree weeks after infection. Manifestation of the resistance of ITT (exp osed) sheep was suppressed by administration of the immunosuppressant, dexamethasone. Killing of parasites in ITT sheep appeared to have cea sed by 21 to 28 days after infection. The basis of the acquired resist ance was deemed to be an exceptional immunological capacity of ITT she ep responding to an antigen, or an immunological suppressant, peculiar to F. gigantica. That molecule, produced by juvenile parasites, warra nts further study as a candidate for a vaccine. (C) 1997 Elsevier Scie nce B.V.