Cystic echinococcosis in Iceland: a brief history and genetic analysis of a 46-year-old Echinococcus isolate collected prior to the eradication of this zoonotic disease

Abstract

Cystic echinococcosis (CE) is considered the most severe parasitic disease ever affected the human population in Iceland. Before the start of eradication campaign in the 1860s, Iceland was a country with very high prevalence of human CE, with approximately every fifth person infected.Eradication of CE from Iceland by 1979 was a huge success story and served as a leading example for other countries how to combat such a severe One Health problem. However, there is no genetic information on Echinococcus parasites before eradication. Here we reveal the genetic identity for one of the last Echinococcus isolates in Iceland, obtained from a sheep 46 years ago (1977). We sequenced a large portion of the mitochondrial genome (8,141 bp) and identified the isolate as E. granulosus sensu stricto genotype G1. As G1 is known to be highly infective genotype to humans, it may partly explain why such a large proportion of human population in Iceland was infected in the past. The study demonstrates that decades-old samples hold significant potential to uncover genetic identities of parasites in the past.