First records of the raccoon roundworm (Baylisascaris procyonis) in Luxembourg: evidence for natural spread and a novel introduction

The raccoon roundworm (Baylisascaris procyonis), a gastrointestinal nematode parasite of the raccoon (Procyon lotor), is the causative agent of a zoonotic disease that can cause severe neurological sequelae and even fatal cases. The parasite is now established in Europe and, while not present in all raccoon populations, it is currently expanding its range. Understanding the geographic distribution of the roundworm is a necessity for public health. Here, we report the first detections of the raccoon roundworm from Luxembourg. We used genetic techniques to test whether the roundworm originated from a distinct introduction event or entered the country by natural dispersal. We detected two roundworms in a raccoon that was road-killed in Echternach, northeastern Luxembourg. Furthermore, in a wildlife rescue centre, roundworms were detected in the latrine of an enclosure containing seven raccoons. Using different genetic techniques, we showed the Echternach roundworms to originate from the nearest German population, while the rescue centre roundworms were genetically distinct. By genotyping the host from a roundworm DNA extract, we identified a raccoon originating from southwest Luxembourg as the host of at least one roundworm. Roundworms are thus colonising Luxembourg both by natural dispersal and from an introduced population. The (potential) hosts all originated from the local population, suggesting that imported/introduced roundworms have already spread to the local raccoon population. Authorities should act as though the parasite is already widespread in the country, raising awareness among the public and individuals with occupational contact with raccoons.