An experimental study in sheep, to confirm triclabendazole resistance of Fasciola hepatica in Patagonia, Argentina

F. V. OLAECHEA; M. LARROZA; H. SOLANA; S. SCARCELLA; S. CARNEVALE

Buenos Aires

Congreso; Congreso. XXIII Congreso Internacional De La Asociación Mundial Para el Avance de la Parasitología Veterinaria; 2011

Asociación Mundial Para el Avance de la Parasitología Veterinaria

The aim of the present experimental study in sheep was to compare the efficacy of TCBZ against the resistant liver fluke strain described in the study of Olaechea et al. (2011) against a susceptible field strain. A group of 10 lambs were infected each with 200 metacercariae of the resistant (R) strain, and were compared to 10 naturally infected sheep, known as susceptible (S) F. hepatica strain. Eleven weeks after infection, five lambs of the resistant group (RT) and five sheep of the susceptible group (ST), were treated with triclabendazole (10 mg/kg). The remainder lambs and sheep were used as untreated controls (RC and SC). The parameters studied were: GLDH, GGT, ELISA measuring antibodies against recombinant cathepsin-L1 and eggs per gram of faeces (epg). Lambs were slaughtered 16 weeks after infection and sheep 4 weeks after treatment and the number of flukes was counted. The GLDH, GGT serum levels and the OD value of the ELISA indicated that the infection was well established in all lambs and had not decreased as a result of the treatment in group RT. Patent infections were observed in all animals of groups RT, RC and SC. In group ST, no eggs were found after treatment and no flukes at necropsy, showing 100% efficacy of TCBZ. The percentages of flukes collected in artificially infected lambs were 15% in RC and 14% in RT. These results corresponded to efficacies of 9% in the resistant strain. Histological sections of flukes recovered from treated lambs (RT), showed normal morphology, with no damage attributable to the TCBZ treatment. Since the resistant strain was isolated from a cattle farm, it confirms the existence of triclabendazole resistance in Patagonia, Argentina.