Detection of <i>Echinococcus multilocularis</i> in coyotes in Washington State, USA highlights need for increased global wildlife surveillance

Abstract Echinococcus multilocularis is a zoonotic cestode that uses canids as definitive hosts and rodents as intermediate hosts. In humans, this parasite is the causative agent of alveolar echinococcosis. Recently, its range has been expanding across the Northern Hemisphere, and it is increasingly detected in wild canids, domestic dogs, and humans across Canada and the United States. While this expansion has been documented in isolated studies across the continent, a lack of routine sampling in wildlife hinders our ability to anticipate and mitigate further spread of E. multilocularis . We confirmed the presence of E. multilocularis in Washington State, USA, using a combination of morphological and molecular techniques across carcasses and field-collected scats of coyotes ( Canis latrans ), this region’s most common wild canid. Morphological identification of adult worms was confirmed by next-generation sequencing. Over a third of all samples tested positive for E. multilocularis when all methodologies were combined. Sequencing revealed a haplotype of E. multilocularis matching a documented haplotype originally of European origin in British Columbia, Canada. Our study provides the first confirmation of E. multilocularis in a wild host on the west coast of the U.S and provides additional haplotype information crucial to tracking the geographical expansion of the parasite. We also provide a new next-generation sequencing primer targeting cestodes of canids. The difference in amplification between intestinal and fecal samples suggests that non-invasive fecal sampling using DNA metabarcoding—a popular method of helminth surveillance —may lead to underestimation of prevalence, hindering control measures. The global significance of these findings extends beyond North America; E. multilocularis is a major public health concern in Europe and Asia, where alveolar echinococcosis is increasingly diagnosed in humans. Our study highlights the urgent need for increased surveillance and improved diagnostic strategies worldwide, particularly in regions with significant human-wildlife contact. Author summary Parasites that are transmitted between wildlife, domestic animals, and people are an important part of global health. One such parasite is Echinococcus multilocularis , a small tapeworm of canids that can cause a severe, life-threatening disease in humans called alveolar echinococcosis. Many wild canid hosts of the parasite, such as coyotes, overlap significantly with domestic dogs, which facilitates transmission to humans. In Europe, Asia, and Arctic regions of North America, E. multilocularis has long been recognized as a major public health problem. In recent decades its range has expanded across the Northern Hemisphere, raising concern. In this study, we discovered E. multilocularis in coyotes in a densely populated area of Washington State, USA — the first detection of E. multilocularis in a wild host in the region. More than one-third of our coyote samples contained E. multilocularis , confirming that it is widespread in the area. Genetic testing showed that the strain we detected matched one previously found in Canada, originally from Europe. Our findings underscore the importance of monitoring E. multilocularis and other parasites in wildlife so that emerging public health threats can be detected early, reducing risk to people and pets.

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