Detección de la infección ovina por f. Hepática mediante PCR y de la resistencia antihelmíntica en rebaños infectados de forma natural

Resumen

The aim of this study was to develop a PCR based on the ribosomal internal transcribed spacer for the diagnosis of the infection by Fasciola hepatica in faeces of sheep. The infection could be detected from the second week post-infection in experimentally infected sheep after the amplification of a 292 bp fragment. On the other hand, this PCR was used to detect the anthelmintic resistance (AR) in sheep flocks naturally infected; these results were compared with other techniques such as the faecal egg count reduction test (FECRT) and the coproantigen reduction test (CRT). The FECRT was carried out in two flocks, Santillán de la Vega (SV) and Corullón (CR) in which the sheep were divided into three groups to be treated with albendazole (ABZ), clorsulon (CL) and triclabendazole (TCBZ). Faeces were individually collected on days 0, 7, 15 and 30 post-treatment (pt) for the detection of the number of eggs per gram (epg) in faeces, coproantigen measurement and DNA extraction. According to the FECRT, both flocks resulted resistant to ABZ and CL against adult flukes; in relation to the treatment with TCBZ, the flock SV was susceptible against all stages although the flock CR resulted resistant against adult flukes and susceptible against immature forms. To compare the FECRT and the PCR results, we calculated the percentage of positive animals each sampled day after treatment. For both flocks, the percentage of positive sheep was always higher by PCR than by sedimentation, thus confirming that the PCR is a more sensitive method to diagnose the infection and therefore to detect the resistance. On the other hand, the CRT was carried out by means of a sandwich ELISA kit in the flock SV. When comparing the percentage of positive animals between PCR and this ELISA we observed that, after the treatment with ABZ, the percentages of positive animals was higher on day 30 pt by PCR although after the administration of CLOR all percentages were the same by both techniques. Regarding the treatment with TCBZ, the percentages of positive sheep were higher by PCR on days 7 and 15 pt.