Significant increase of Echinococcus multilocularis prevalence in foxes, but no increased predicted risk for humans

- Increased prevalence of E. multilocularis in red foxes.
- In an area that had a stable prevalence since the first detection in 1997.
- An updated risk model shows no additional human cases.
- No infected dogs were found.
- Deworming schemes of dogs were inadequate.

The emergence of the zoonotic tapeworm Echinococcus multilocularis, causative agent of alveolar echinococcosis (AE), poses a public health risk. A previously designed risk map model predicted a spread of E. multilocularis and increasing numbers of alveolar echinococcosis patients in the province of Limburg, The Netherlands. This study was designed to determine trends in the prevalence and worm burden of E. multilocularis in foxes in a popular recreational area in the southern part of Limburg to assess the risk of infection for humans and to study the prevalence of E. multilocularis in dogs in the adjacent city of Maastricht. Thirty-seven hunted red foxes were tested by the intestinal scraping technique and nested PCR on colon content. Additionally, 142 fecal samples of domestic dogs from Maastricht were analyzed by qPCR for the presence of E. multilocularis.In foxes, a significantly increased prevalence of 59% (95% confidence interval 43-74%) was found, compared to the prevalence of 11% (95% CI 7-18%) in 2005-2006. Average worm burden increased to 37 worms per fox, the highest since the first detection, but consistent with the prediction about the parasite population for this region. Updated prediction on the number of AE cases did not lead to an increase in previous estimates of human AE cases up to 2018. No dogs in the city of Maastricht tested positive, but results of questionnaires showed that deworming schemes were inadequate, especially in dogs that were considered at risk for infection.