Rapid and Reliable Detection of Echinococcus multilocularis from Faeces Using Droplet Digital PCR

Alveolar echinococcosis is a severe helminthic disease in humans caused by larvae of the fox tapeworm Echinococcus multilocularis. Austria is considered an endemic area with hotspots having up to 45% prevalence (Bagó et al. in Proceedings of the Zoo and Wildlife Health Conference 2019, Berlin, p. 91, 2019). At our facility, we have registered a notifiable increase of animals submitted for the diagnosis of E. multilocularis since 2016. Therefore, we investigated high throughput diagnostic methods to provide rapid and reliable results in comparison with our current method.

We have developed and compared a novel method of detection using droplet digital PCR (ddPCR) combined with previous target specific extraction according to Maas et al. (Vet Parasitol 230:20-24, 2016), with our current macroscopic method "Shaking in a Vessel Technique" (SVT) by Duscher et al. (Parasitol Res 95(1):40-42, 2005). We investigated 77 wild canids (72 red foxes, 5 golden jackals) using both methods. The data were analyzed using a non-Bayesian approach, applying bootstrapping to create confidentiality intervals.

Sensitivity for droplet digital PCR was 90.51% with the 95% credibility interval ranging from 82.50 to 96.92%, whereas mean sensitivity for SVT was 92.04% with a 95% credibility interval ranging from 84.75% to 98.36%. Additionally, a non-linear regression similar to R² could be pointed out between the counted worms and the results gathered from ddPCR.

Magnetic capture extraction followed by ddPCR shows strong potential as a high throughput method for diagnosing E. multilocularis prevalence in diverse canid populations as well as infection intensities of individual animals, giving valuable epidemiological insights of the distribution amongst wild canids as an alternative to conventional qPCR or macroscopic methods.