Abstract
For clinical epidemiology specialists, connecting the genetic diversity of Echinococcus multilocularis to sources of infection or particular sites has become somewhat of a holy grail. It is very difficult to trace the infection history of alveolar echinococcosis (AE) patients as there may be an incubation period of five to 15 years before reliable diagnosis. Moreover, the variability of parasitic manifestations in human patients raises the possibility of genetically different isolates of E. multilocularis having different levels of pathogenicity. Thus, the exposure of human patients to different strains or genotypes circulating in geographically different environments may lead to different disease outcomes. Molecular tools, such as the microsatellite marker EmsB, were required to investigate these aspects. This genetic marker was previously tested on a collection of 1211 European field samples predominantly of animal origin, referenced on a publicly available database. In this study, we investigated a panel of 66 metacestode samples (between 1981 and 2019) recovered surgically from 63 patients diagnosed with alveolar echinococcosis originating from four European countries (France, Switzerland, Germany, Belgium). In this study, we identified nine EmsB profiles, five of which were found in patients located in the same areas of France and Switzerland. One profile was detected on both sides of the French-Swiss border, whereas most patients from non-endemic regions clustered together in another profile. EmsB profiles appeared to remain stable over time because similar profiles were detected in patients who underwent surgery recently and patients who underwent surgery some time ago. This study sheds light on possible pathways of contamination in humans, including proximity contamination in some cases, and the dominant contamination profiles in Europe, particularly for extrahepatic lesions.
Highlights
Echinococcus multilocularis is the parasite responsible for alveolar echinococcosis (AE) in humans, one of the most dangerous zoonoses in the Northern Hemisphere
Two mixtures (Multiplex PCR Master Mix (MLX) and Platinum Taq Polymerase (PL)) were compared for four AE lesions from a panel of 120 samples referred for PCR diagnosis of Echinococcus infection (Figure 1)
Obtained for EmsB were compared with those obtained with Platinum Taq DNA polymerase mixture (PL) by Euclidean distance calculation
Summary
Echinococcus multilocularis is the parasite responsible for alveolar echinococcosis (AE) in humans, one of the most dangerous zoonoses in the Northern Hemisphere. It belongs to the Taeniidae family and its life cycle involves passage through several different mammalian hosts. Experimental estimates of the patent period in carnivores range from 25 days post protoscolex ingestion [1] to beyond 90 days [2]. Rodents act as an intermediate host (IH), following the ingestion of parasite eggs originating from infected carnivore feces contaminating the environment. The oncospheres hatched from the eggs reach the liver of the IH where they develop into metacestodes, and protoscoleces are usually produced two to three months post-infection. Living in an endemic region is the major risk factor for contracting the disease [7], but many other putative risk factors have been identified, including agricultural activities, hunting activities and owning a pet dog or cat [8]
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