Detection of Echinococcus multilocularis in foxes: evaluation of a protocol of the intestinal scraping technique

The intestinal scraping technique (IST) is widely used for the detection of definitive hosts infected with Echinococcus multilocularis. The sensitivity of the method has been questioned in recent years. Several variations of the technique are used that may differ in their performance. We therefore estimated the diagnostic sensitivity and specificity of the IST protocol used in our lab by examining the small intestines of 210 E. multilocularis-infected foxes and 294 foxes that had tested negative for this parasite. To this end, IST was first performed on 48 and 294 intestines from infected and uninfected foxes respectively, followed by an examination of the entire remaining mucosa of the small intestine to discover any infections with E. multilocularis that had not been detected by IST. The point estimate for diagnostic sensitivity was 100%. Five different classes of infection intensities were formed. The lower limits of the 95% confidence intervals ranged between 76.8% and 92.6% depending on the number of samples analysed per class. When the small intestines of another 162 infected foxes were examined by IST and the results recorded separately for the anterior, middle and posterior third of the small intestine, a strong preference of E. multilocularis for the posterior third was observed. For epidemiological purposes, it may thus be possible to restrict routine investigations to the posterior portion of the small intestine. By contrast, a reduction of the number of slides examined per infected animal may lead to a considerable loss in sensitivity in animals with a low intensity of infection.