Ultrasound as a monitoring tool for cystic echinococcosis in sheep

Abstract

An ultrasound-based survey for cystic echinococcosis (CE) in sheep was carried out in Sardinia in 2012. The study was done on three farms (A, B, C) which had been pre-selected for different CE prevalence levels (A: >80%, B: 50–80%, C: <50%). In total, 129 sheep were examined on the farms using portable ultrasound equipment (A: n=51, B: n=30, C: n=48). Within a period of 20 days after ultrasound examination, all sheep were slaughtered and underwent a parasitological post-mortem examination for cysts in the liver and lungs. With post-mortem as gold standard, ultrasonography gave a test sensitivity of 88.7% and a specificity of 75.9%, while the positive and negative predictive values were 81.8% and 84.6%, respectively. When only sheep with fertile cysts were considered, the sensitivity of the test increased to 100%. We conclude that the ultrasound examination of the liver in sheep – using state-of-the-art technology – is a sensitive and specific diagnostic tool, which is cost-effective, highly appropriate for field use and requires only moderate time (no shaving required). The method can also be applied to other livestock species and will be useful tool in epidemiological studies, monitoring schemes and vaccination/control trials.